U.S. patent application number 14/893893 was filed with the patent office on 2016-05-05 for mitigating thermal runaway in lithium ion batteries using damage-initiating materials or devices.
This patent application is currently assigned to THE REGENTS OF THE UNIVERSITY OF CALIFORNIA. The applicant listed for this patent is THE REGENTS OF THE UNIVERSITY OF CALIFORNIA. Invention is credited to Anh Lee, Weiyi Lu, Yu Qiao, Yang Shi.
Application Number | 20160126535 14/893893 |
Document ID | / |
Family ID | 55853645 |
Filed Date | 2016-05-05 |
United States Patent
Application |
20160126535 |
Kind Code |
A1 |
Qiao; Yu ; et al. |
May 5, 2016 |
MITIGATING THERMAL RUNAWAY IN LITHIUM ION BATTERIES USING
DAMAGE-INITIATING MATERIALS OR DEVICES
Abstract
A method of manufacturing a battery includes introducing a first
material to the battery, providing an anode, a cathode and a
separator of the battery; and assembling the anode, the separator
and the cathode. The first material is configured and arranged to
increase the internal impedance of the battery upon mechanical or
thermal loading.
Inventors: |
Qiao; Yu; (San Diego,
CA) ; Lu; Weiyi; (La Jolla, CA) ; Shi;
Yang; (La Jolla, CA) ; Lee; Anh; (La Jolla,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
THE REGENTS OF THE UNIVERSITY OF CALIFORNIA |
Oakland |
CA |
US |
|
|
Assignee: |
THE REGENTS OF THE UNIVERSITY OF
CALIFORNIA
Oakland
CA
|
Family ID: |
55853645 |
Appl. No.: |
14/893893 |
Filed: |
June 5, 2014 |
PCT Filed: |
June 5, 2014 |
PCT NO: |
PCT/US14/41051 |
371 Date: |
November 24, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61831437 |
Jun 5, 2013 |
|
|
|
Current U.S.
Class: |
429/61 ;
29/623.1; 29/623.5 |
Current CPC
Class: |
H01M 2200/10 20130101;
H01M 2/1077 20130101; H01M 4/62 20130101; H01M 2/348 20130101; B60L
50/64 20190201; H01M 10/4207 20130101; H01M 2220/20 20130101; Y02E
60/122 20130101; B60L 50/60 20190201; H01M 10/0525 20130101; H01M
10/058 20130101; H01M 10/0481 20130101; H01M 10/4235 20130101; Y02E
60/10 20130101; H01M 2/347 20130101; Y02T 10/70 20130101; Y02T
10/7011 20130101 |
International
Class: |
H01M 2/34 20060101
H01M002/34; H01M 10/0525 20060101 H01M010/0525; H01M 10/058
20060101 H01M010/058; H01M 2/12 20060101 H01M002/12 |
Goverment Interests
FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] The invention was made with government support under
DE-AR0000396 awarded by the Department of Energy. The government
has certain rights in this invention.
Claims
1. A method of manufacturing a battery, the method comprising:
introducing a first material to the battery; providing an anode, a
cathode, charge collectors, and a separator of the battery; and
assembling the anode, the separator and the cathode, wherein the
first material is configured and arranged to increase the impedance
of the battery upon mechanical loading.
2-4. (canceled)
5. The method of claim 1, wherein the first material comprises a
particle, a fiber, a tube, a layer, or a platelet, the first
material formed of one or more of carbon, a glass, ceramic
materials, metallic materials, polymer materials, liquids, gels, or
composites produced from combinations thereof.
6. The method of claim 1, wherein the first material comprises an
array or a mesh or a truss, or a layer stack, the first material
formed of one or more of carbon, a glass, ceramic materials,
metallic materials, polymer materials, liquids, gels, or composites
produced from combinations thereof.
7. (canceled)
8. The method of claim 1, wherein the first material comprises a
shape or volume changing material, the shape or volume changing
material having a first shape or volume below a transition
temperature and a second shape or volume at or above the transition
temperature.
9.-11. (canceled)
12. The method of claim 1, wherein the first material has
anisotropic properties and promotes damages in the electrode upon
mechanical loading due to stiffness mismatch and local bending.
13-16. (canceled)
17. A method of manufacturing a battery, the method comprising:
introducing a first device to the battery; providing an anode, a
cathode, a separator, charge collectors, binders, an electrolyte,
and a case of the battery; and assembling the anode, the separator
and the cathode, wherein the first device is configured and
arranged to promote damages in electrodes or to change
configurations of the electrolyte upon mechanical or thermal
loading.
18. The method of claim 17, wherein the first device comprises a
first material that is stable and non-reactive under battery
operation conditions.
19. The method of claim 17, wherein the first device comprises a
container, the container encloses a second material, the container
being configured to release or to expose the second material upon
mechanical or thermal loading.
20. (canceled)
21. The method of claim 19, wherein the fire-extinguishing agents,
thermal runaway retarders, electrolyte absorbers, and gas
generation agents comprise solid, gel or liquid materials, foaming
materials that generate gas or bubbles.
22. (canceled)
23. A method of reducing or eliminating thermal runaway in a
battery, the method comprising: increasing an internal impedance of
the battery upon mechanical loading or thermal loading to reduce or
eliminate thermal runaway in the battery.
24. (canceled)
25. The method of claim 23, wherein increasing the internal
impedance comprises causing cracks, voids, or debonding in the
battery.
26. The method of claim 23, further comprising causing a first
material in the battery to change from a first shape or volume to a
second shape or volume upon thermal loading to cause cracks, voids
or debonding in the electrodes, charge collector, electrolyte, or
membrane of the battery, the shape or volume-changing material
having a first shape or volume below a transition temperature and a
second shape or volume at or above the transition temperature, or
the shape or volume-changing material having the first shape or
volume before mechanical loading and the second shape or volume
upon mechanical loading.
27-29. (canceled)
30. The method of claim 26, further comprising directly releasing
elastic energy from the elastic energy storage material into the
electrode to displace a plurality of damage initiators, and causing
damage in the electrode.
31. The method of claim 30, wherein the plurality of damage
initiators in the electrode deforms upon mechanical or thermal
loading when aided by another material.
32. (canceled)
33. A battery comprising: electrodes; a membrane; an electrolyte;
charge collectors; and a first material configured and arranged to
increase an internal impedance of the battery upon mechanical or
thermal loading to reduce or eliminate thermal runaway.
34. The battery of claim 33, wherein the first material is embedded
in the one or more of the electrodes, charge collectors, or
membrane, the first material configured to create cracks or voids
or debonding in the one or more electrodes, membrane, electrolyte,
or charge collectors, upon mechanical or thermal loading.
35-36. (canceled)
37. The battery of claim 33, wherein a second material comprises
fire-extinguishing agents, thermal runaway retarders, electrolyte
absorbers, gas generation agents, or a combination of them, the
fire-extinguishing agents comprise solid or liquid chemicals, and
the thermal runaway retarders and gas generation agents comprise
foaming materials that generate bubbles.
38. The battery of claim 33, wherein the gas generation agents
comprise materials that generate gas phase or gas bubbles, and the
gas generation agents are provided, as particles, layers, or
aggregates, in or on one or more electrodes, the charge collectors,
the case, the membrane separators, or the electrolyte.
39-40. (canceled)
41. The battery of claim 22, wherein the first material comprises a
binder of the one or more electrodes, the binder configured to
crack upon mechanical loading, or thermal abuse.
42. (canceled)
43. The method of claim 19, wherein the second material comprises
fire-extinguishing agents, thermal runaway retarders, electrolyte
absorbers, and gas generation pagents.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. application Ser.
No. 61/831,437 filed on Jun. 5, 2013, which is incorporated herein
by reference. This patent application is related to U.S.
application Ser. No. 61/831,455 filed Jun. 5, 2013, and entitled,
"Non-Straight, Hollow, and/or Frictional Battery Cells/Structures
as Protection and Structural Components", and PCT application filed
on the same day as this application, titled "Rate-sensitive and
self-releasing battery cells and battery-cell structures as
structural and/or energy-absorbing vehicle components", both of
which are hereby incorporated by reference.
BACKGROUND
[0003] Lithium-ion batteries are widely used because of their high
energy density. However, their safety, especially when subjected to
mechanical or thermal abuse, is a major concern. For instance, as a
Li-ion battery is impacted or involved in a collision, internal
shorting, e.g., direct contact of cathode and anode due to rupture
of membrane separator, can happen, which can lead to thermal
runaway.
[0004] Chemically protective techniques such as the use of advanced
cathode materials, such as LiMn.sub.2O4, LiFePO.sub.4, which
release less or no oxygen during decomposition, help to improve the
safety of Li-ion batteries. Similarly, alternative anode materials,
e.g. Li.sub.4Ti.sub.5O.sub.12, which reduce heat generation at
elevated temperature and even absorb oxygen have also been used.
Multifunctional components, such as flame retardant and/or
self-healing materials can also be added into the battery
housing.
[0005] In addition, mechanically protective techniques, such as the
use of protective battery pack mount and housing, can reduce
physical damages caused by external loadings. Low aspect ratio tube
cell structure, which enhances air flow in the battery module and
pack, can facilitate better thermal management.
[0006] Some techniques use phase change materials (PCM) to absorb
heat; or use positive temperature coefficient (PTC) elements, which
expand to increase impedance once the internal temperature of the
battery cell reaches a threshold value; or use phase transition
materials that initiate local volume mismatch operate after thermal
runaway has begun. Low-melting-point membrane separators or
particles can block ion transport paths operate after thermal
runaway has begun.
SUMMARY
[0007] More efficient methods that include thermal runaway shutdown
mechanisms that can be triggered either mechanically or thermally,
or simultaneously, as battery damage happens (i.e., before or
shortly after thermal runaway starts) are desired. The present
systems and techniques can operate before or shortly after thermal
runaway has begun. Mechanisms that operate before thermal runaway
has begun offer better control of material behavior and obviate the
need for a relatively high local temperature to be achieved before
mitigation mechanisms are deployed.
[0008] The methods and systems disclosed herein have working
temperatures that are below the boiling points of flammable liquids
in Li ion batteries (e.g. ethyl methyl carbonate), and the
effectiveness of the methods disclosed herein has been validated.
The methods and systems disclosed herein can work directly under
mechanical loading when battery cell is subjected to mechanical
abuse (e.g. impact or collision). The materials used in the systems
disclosed herein do not have negative effects on the
electrochemical performance of battery, and, are therefore relevant
to high-power batteries.
[0009] When a battery is subjected to dynamic loading, such as an
impact, or high-pressure quasi-static loading, its internal
structure can be damaged, causing internal shorting. Under this
extreme condition, the above mentioned technique may not fully
prevent thermal runaway. New techniques to mitigate thermal runaway
simultaneously as or even before internal shorting takes place
(that is, before the temperature increases) while the batteries are
under mechanical abuse, are desired.
[0010] As a mechanical load is applied to the battery, damage
initiators can trigger widespread damage or destruction of the
electrode, so that the internal resistance increases significantly
to mitigate thermal runaway even before it can happen. The damage
of electrodes can be induced under a wide range of loading
modes.
[0011] For example, hollow carriers containing fire extinguishing
agents (FEA), thermal runaway retarders (TRR), electrolyte
absorbers (EA), and/or gas generation agents (GGA), can be broken
once the battery is subjected to mechanical loading, so that FEA,
TRR, EA, and/or GGA can be released to suppress thermal runaway and
reduce the risk of fires.
[0012] The hollow carriers of FEA, TRR, EA, or GGA may also act as
cracking/voiding promoters. For instance, FEA, TRR, EA, or GGA can
be sealed in micro-capsules or hollow fibers. When an external
force applied on the battery exceeds a threshold value, a sealing
layer in the hollow carriers is broken and FEA, TRR, EA, or GGA
would be released to interrupt transmission of oxygen or ions. The
size, materials, and the strength of the capsules can be
adjusted.
[0013] Granular materials, fibers, arrays or meshes, and elastic
energy storage materials (e.g. springs) can also be mixed with
electrode materials or be placed near the electrode materials. When
external loadings are applied to the cell, widespread cracking,
rupture, and/or voiding can be initiated. Consequently, internal
resistance increases significantly, suppressing electro-chemical
reactions. In other words, the granular materials, fibers, arrays
or meshes, and pre-stressed elastic energy storage materials serve
as damage initiators (DI). They can be porous or hollow and carry
FEA, TRR, EA, or GGA in them. The type of materials, the amount,
the porosity, the size, the shape, the surface properties, and the
locations and distributions of the damage initiators can be
adjusted.
[0014] The charge collectors, separation membranes, and battery
cell cases can be specially designed to act as DI. For instance, as
the charge collectors are wavy or have a certain surface patterns,
as the battery cell is deformed local shearing, bending, torsion,
or compression can be promoted in electrodes, so that widespread
damage of electrodes is achieved.
[0015] The above damage initiators can also be thermally
responsive, enhancing the thermal-runaway mitigation performance.
For instance, the porous or hollow carriers of FEA, TRR, EA, or GGA
can melt or soften at a threshold temperature, so as to expose the
FEA, TRR, EA, or GGA to the battery system and retard
electrochemical reactions. FEA, TRR, EA, or GGA, with or without
carriers, can be mixed with electrodes or placed near electrodes,
and retard electro-chemical reactions as temperature rises to a
threshold point. The damage initiators can be confined or triggered
by devices or carriers that melt or soften at a threshold
temperature. The thermally responsive processes of damage
initiators take place after thermal runaway has begun. The working
temperature can be readily adjustable to close to or lower than the
boiling points of flammable liquids in lithium ion batteries.
[0016] The disclosed methods and apparatus work under various types
of external or internal loadings, and have broad applicability and
are particularly useful for various vehicles (e.g., electric
vehicles (EV)), military devices, and large-scale energy storage
units that use batteries.
[0017] In one aspect, methods described herein include introducing
a first material to the battery, providing an anode, a cathode,
charge collectors, and a separator of the battery; and assembling
the anode, the separator and the cathode. The first material is
configured and arranged to reduce a mechanical strength of the
battery upon mechanical loading.
[0018] Implementations can include one or more of the following
features. The first material includes a first device. Reducing the
mechanical strength includes causing damages or configuration
change of the battery upon mechanical loading. The first material
is configured and arranged to increase an internal impedance of the
battery upon mechanical loading. The first material includes a
particle, a fiber, a tube, a layer, or a platelet, the first
material formed of one or more of carbon, a glass, ceramic
materials, metallic materials, polymer materials, or composites
produced from combinations thereof The first material includes an
array or a mesh or a truss, or a layer stack, the first material
formed of one or more of carbon, a glass, ceramic materials,
metallic materials, polymer materials, or composites produced from
combinations thereof.
[0019] The first material includes expandable graphite, the
expandable graphite configured and arranged to expand and cause
cracks or voids in the battery when heated to or beyond a critical
temperature. The first material includes a shape or volume changing
material, the shape or volume changing material having a first
shape or volume below a transition temperature and a second shape
or volume at or above the transition temperature.
[0020] The first material includes a binder of the cathode, the
anode, or both, and introducing the first material to the battery
comprises reducing a binder content of the cathode, the anode, or
both of the battery or reducing a molecular weight of the
binder.
[0021] The first material is deposited in aggregates or distribute
non-uniformly inside the battery. The first material is distributed
non-uniformly inside the battery.
[0022] The first material has anisotropic properties and promotes
widespread damages in the electrode upon mechanical loading due to
stiffness mismatch and local bending. The first material comprises
a non-uniformly distributed damage initiators placed inside or near
an electrode of the battery. The methods include anisotropically
deforming or displacing the damage initiators to cause widespread
damage in the electrode. The damage initiators include a charge
collector, a membrane separator, or a battery case having a
heterogeneous or anisotropic shape or material.
[0023] The methods include providing a soft impact promotion
component in the battery to promote widespread damages in the
electrode.
[0024] In one aspect, methods described herein include introducing
a first device to the battery, providing an anode, a cathode, a
separator and an electrolyte of the battery; and assembling the
anode, the separator and the cathode. The first device is
configured and arranged to promote damages in electrodes or to
change configurations of the electrolyte upon mechanical or thermal
loading. The first device includes a first material that is stable
and non-reactive under battery operation conditions.
[0025] The first device includes a container, the container
encloses a second material, the container being configured to
release or to expose the second material upon thermal loading. The
container includes a hollow or porous particle, or tube and the
second material includes fire-extinguishing agents, thermal runaway
retarders, electrolyte absorbers, gas generation agents, or
combinations of them.
[0026] The fire-extinguishing agents, thermal runaway retarders,
electrolyte absorbers, and gas generation agents include solid or
liquid materials, foaming materials that generate bubbles. The
fire-extinguishing agents and thermal runaway retarders include
materials that change solvation structures of ions or materials
that change viscosity of electrolyte solutions.
[0027] In one aspect, methods described herein include increasing
an internal impedance of the battery upon mechanical loading or
thermal loading to reduce or eliminate thermal runaway in the
battery. The methods include reducing heat generation or internal
shorting in the battery upon mechanical or thermal loading.
[0028] Increasing the internal impedance includes causing cracks
and/or voids in the battery. The methods include causing a first
material in the battery to change from a first shape or volume to a
second shape or volume upon thermal loading to cause in-plane or
out-of-plane cracks, or voids in the battery, the shape or
volume-changing material having a first shape or volume below a
transition temperature and a second shape or volume at or above the
transition temperature. Increasing the internal impedance of the
battery includes causing a first material to release a second
material upon mechanical or thermal loading.
[0029] The methods include placing an elastic energy storage
material inside or near an electrode of the battery. The elastic
energy storage material is confined by a locking component that
weakens and releases elastic energy upon mechanical or thermal
loading. The methods include directly releasing elastic energy from
the elastic energy storage material into the electrode to displace
a plurality of damage initiators, and causing widespread damage in
the electrode. The plurality of damage initiators in the electrode
deforms upon mechanical or thermal loading when aided by another
material.
[0030] The elastic energy storage material includes a part of a
prestressed charge collector, a part of a prestressed membrane
separator, or a part of a prestressed battery case.
[0031] In one aspect, batteries described herein include
electrodes, a membrane, an electrolyte, charge collectors, and a
first material configured and arranged to increase an internal
impedance of the battery upon mechanical or thermal loading to
reduce or eliminate thermal runaway.
[0032] Implementations can include one or more of the following
features. The first material is embedded in the one or more of the
electrodes, the first material configured to create cracks or voids
in the one or more electrodes upon mechanical or thermal loading.
The first material includes a shape or volume changing material
embedded in the one or more electrodes, the shape or
volume-changing material changing from a first shape or volume
below a transition temperature to a second shape or volume at or
above the transition temperature upon thermal loading to cause
in-plane or out-of-plane cracks, or voids in the battery.
[0033] The first material includes a container, the container
encloses a second material, the container being configured to
release or expose the second material upon mechanical or thermal
loading, the first material being deposited in one or more of the
electrodes, the electrolytes, or the membrane. The second material
includes fire-extinguishing agents, thermal runaway retarders,
electrolyte absorbers, gas generation agents, or a combination of
them, the fire-extinguishing agents comprise solid or liquid
chemicals, and the thermal runaway retarders and gas generation
agents comprise foaming materials that generate bubbles.
[0034] The gas generation agents include materials that generate
gas phase or gas bubbles, and the gas generation agents are
provided in the one or more electrodes, the membrane separators, or
the electrolyte. The thermal runaway retarders include materials
that change solvation structures of ions in the electrolytes,
materials that dilute the electrolytes, materials that change
viscosity of the electrolytes. The second material includes
elastomers that expand upon release from the first material. The
first material includes a binder of the one or more electrodes, the
binder configured to crack upon mechanical loading.
[0035] The batteries can include materials that absorb an
electrolyte, prevent electrolyte from being available for ion
transport, or materials that isolate the electrolyte from a region
of the battery.
[0036] The details of one or more embodiments of the subject matter
described in this specification are set forth in the accompanying
drawings and the description below. Other features, aspects, and
advantages of the invention will become apparent from the
description, the drawings, and the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 shows a schematic of a battery.
[0038] FIG. 2A shows a reference cylindrical rod before mechanical
loading.
[0039] FIG. 2B shows a cylindrical rod having embedded activated
carbon before mechanical loading.
[0040] FIG. 2C shows a cylindrical rod having embedded solid silica
particles before mechanical loading.
[0041] FIG. 2D shows a cylindrical rod having embedded porous
silica particles before mechanical loading.
[0042] FIG. 2E shows cathode sheets.
[0043] FIG. 2F shows ground cathode particles.
[0044] FIG. 3 shows a schematic of a system used to fabricate a
cylindrical electrode.
[0045] FIG. 4A shows a small-scale drop tower apparatus.
[0046] FIG. 4B shows a hammer
[0047] FIG. 5A shows an SEM (scanning electron microscope) image of
an edge of a reference cylindrical rod after mechanical
loading.
[0048] FIG. 5B shows an SEM image of a center portion of a
reference cylindrical rod after mechanical loading.
[0049] FIG. 5C shows an SEM image of an edge of a cylindrical rod
containing solid silica powders after mechanical loading.
[0050] FIG. 5D shows an SEM image of a center portion of a
cylindrical rod containing solid silica powders after mechanical
loading.
[0051] FIG. 5E shows an SEM image of a cylindrical rod containing
porous silica after mechanical loading.
[0052] FIG. 5F shows an SEM image of a close up of a cylindrical
rod containing porous silica after mechanical loading.
[0053] FIG. 6A shows a cylindrical rod containing electrode
material that has been soaked by a solvent
[0054] FIG. 6B shows a cylindrical rod containing activated carbon
and electrode material that has been soaked by a solvent.
[0055] FIG. 6C shows a cylindrical rod containing porous silica
particles and electrode material that has been soaked by a
solvent.
[0056] FIG. 7A shows an SEM image of a cylindrical rod containing
electrode material that has been soaked by a solvent before
mechanical loading.
[0057] FIG. 7B shows an SEM image of an edge of a cylindrical rod
containing electrode material that has been soaked by a solvent
after mechanical loading.
[0058] FIG. 7C shows an SEM image of a center portion of a
cylindrical rod containing electrode material that has been soaked
by a solvent after mechanical loading.
[0059] FIG. 7D: shows an SEM image of an edge of a cylindrical rod
containing activated carbon and electrode material that has been
soaked by a solvent after mechanical loading.
[0060] FIG. 7E: shows an SEM image of a center portion of a
cylindrical rod containing activated carbon and electrode material
that has been soaked by a solvent after mechanical loading.
[0061] FIG. 7F shows an SEM image of cracks around an activated
carbon in an edge of the cylindrical rod.
[0062] FIG. 7G shows an SEM image of cracks around an activated
carbon in a center portion of the cylindrical rod
[0063] FIG. 7H: shows an SEM image of an edge of a cylindrical rod
containing porous silica and electrode material that has been
soaked by a solvent after mechanical loading.
[0064] FIG. 7I: shows an SEM image of a center portion of a
cylindrical rod containing porous silica and electrode material
that has been soaked by a solvent after mechanical loading.
[0065] FIG. 7J shows an SEM image of a center portion of an
impacted porous silica modified cylindrical rod.
[0066] FIG. 7K shows an SEM image of an edge portion of a
cylindrical rod which contains cracks around silica filler.
[0067] FIG. 8A shows a reference cylindrical rod containing anode
material.
[0068] FIG. 8B shows the cylindrical rod of FIG. 8A before
impact.
[0069] FIG. 8C shows an edge of the cylindrical rod of FIG. 8A
after impact.
[0070] FIG. 8D shows a center portion of the cylindrical rod of
FIG. 8A after impact.
[0071] FIG. 9A shows a cylindrical rod containing porous silica
particles.
[0072] FIG. 9B shows cracks in the rod of FIG. 9A after impact.
[0073] FIG. 9C shows cracks in the rod of FIG. 9A after impact.
[0074] FIG. 10A shows an electrode containing single wall carbon
nanotubes after mechanical loading.
[0075] FIG. 10B shows an electrode containing multiple wall carbon
nanotube after mechanical loading.
[0076] FIG. 11A shows an electrode containing expandable graphite
before a thermal trigger.
[0077] FIG. 11B shows cracks in the electrode of FIG. 11A after a
thermal trigger.
[0078] FIG. 12A shows an electrode containing a shape memory
material before a thermal trigger.
[0079] FIG. 12B shows cracks in the electrode of FIG. 12A after
thermal trigger.
[0080] FIG. 12C shows out of plane cracks in the electrode of FIG.
12A after thermal trigger.
[0081] FIG. 13A shows a schematic diagram of a battery that
includes containers.
[0082] FIG. 13B shows electrodes containing hydrophilic hollow
microfibers after mechanical loading.
[0083] FIG. 13C shows electrodes containing hydrophobic hollow
microfibers after mechanical loading.
[0084] FIG. 14A shows electrodes containing hollow hydrophilic
glass fibers after mechanical loading.
[0085] FIG. 14B shows electrodes containing hollow hydrophobic
glass fibers after mechanical loading.
[0086] FIG. 15A shows an empty miniature hollow capsule.
[0087] FIG. 15B shows a miniature hollow capsule containing
water.
[0088] FIG. 15C shows a miniature hollow capsule containing a
surfactant.
[0089] FIG. 15D shows an electrode before mechanical loading.
[0090] FIG. 15E: shows an electrode after mechanical loading.
[0091] FIG. 15F: shows an electrode after mechanical loading.
[0092] FIG. 15G shows an electrode after mechanical loading.
[0093] FIG. 15H shows an electrode after mechanical loading.
[0094] FIG. 16A shows an empty miniature hollow capsule.
[0095] FIG. 16B shows a miniature hollow capsule containing porous
silica particles.
[0096] FIG. 16C shows an electrode before mechanical loading.
[0097] FIG. 16D shows the electrode of FIG. 16C after mechanical
loading.
[0098] FIG. 17A shows electrodes having high molecular weight
binder after mechanical loading.
[0099] FIG. 17B shows electrodes having low molecular weight binder
after mechanical loading.
[0100] FIG. 17C shows electrodes having 6 wt % binder.
[0101] FIG. 17D shows electrodes having 5 wt % binder.
[0102] FIG. 17E shows electrodes having 4.5 wt % binder.
[0103] FIG. 17F shows electrodes having 4 wt % binder.
[0104] FIG. 18A shows a wavy nitinol wire.
[0105] FIG. 18B shows an embedded wire.
[0106] FIG. 18C shows cracks caused by an embedded wire.
[0107] FIG. 19A shows a prestressed coil spring.
[0108] FIG. 19B shows damages in an electrode,
[0109] FIG. 20A shows a copper wire with knots
[0110] FIG. 20B shows damages caused by the copper wire of FIG.
20A
[0111] FIG. 21A shows copper wires as damage initiators.
[0112] FIG. 21B shows damages in an electrode layer.
[0113] FIG. 21C shows debonding.
[0114] FIG. 22A shows a wavy shaped substrate.
[0115] FIG. 22B shows damages in an electrode.
[0116] FIG. 23A shows nanoporous carbon.
[0117] FIG. 23B shows nanoporous carbon that is soaked with an
electrolyte.
[0118] FIG. 23C shows nanoporous particles.
[0119] FIG. 23D shows nanoporous particles that are soaked with an
electrolyte.
[0120] FIG. 24A shows a solution.
[0121] FIG. 24B shows bubbles in the solution of FIG. 24A.
DETAILED DESCRIPTION
[0122] FIG. 1 shows a schematic of a battery 100. Battery 100
includes an anode 110, a cathode 120, a separator 130, electrolytes
140, a first charge collector 111 for the anode 110, and a second
charge collector 121 for the cathode 120, all of which are enclosed
in a housing 150. Electrical connections 160 connect the anode 110
and the cathode 120 to either an external load 162 or to a charging
source 164. Electrons flow along the direction 166 from the anode
110 to the cathode 120 when the battery 100 discharges to power the
external load 162. When the battery 100 powers an electric vehicle
(EV), the load 160 would be the EV. During charging, electrons flow
from the cathode 120 to the anode 110 along direction 168. The
electrolytes 140 allow for ionic conductivity. The separator 130
separates the anode 110 and the cathode 120 to prevent a short
circuit. Examples of the cathode include lithium cobalt oxide
(LCO), lithium (nickel cobalt manganese) oxide (NCM), lithium
(nickel cobalt aluminum) oxide (NCA), lithium manganese oxide
(LMO), lithium iron phosphate (LFP). Examples of anode includes
graphite, graphene, carbon nanotubes (CNT), Li-alloy, Si, TiO.sub.2
and Sn. Examples of electrolytes include LiPF.sub.6, LiBF.sub.4 or
LiClO.sub.4 in organic solvent such as ethylene carbonate (EC),
ethyl methyl carbonate (EMC), dimethyl carbonate (DMC) and diethyl
carbonate (DEC). Examples of separator include polyethylene (PE),
polypropylene (PP), trilayer PP/PE/PP, and any combination of
them.
[0123] In general, the anode 110 and the cathode 120 can include
binders such as polyvinylidene fluoride (PVDF) and poly(methyl
methacrylate) (PMMA), and conductors such as active carbon.
[0124] Electrochemical reactions that operate in the battery 100
are exothermic. Thermal runaway occurs when the reaction rate
increases due to an increase in temperature, causing a further
increase in temperature and hence a further increase in the
reaction rate. Thermal runaway can be a process by which an
exothermic reaction goes out of control (e.g., when accelerated by
a temperature rise), often resulting in an explosion or fire.
[0125] Lithium (Li) ion batteries, while providing higher capacity,
are more reactive and have lower thermal stability, compared with
other batteries such as lead-acid batteries. This makes Li ion
batteries susceptible to thermal runaway in cases of abuse such as
high temperature operation (e.g. >130.degree. C.) or
overcharging. At elevated temperatures, electrode decomposition
generates oxygen, which then reacts with the organic electrolyte of
the cell. This is a safety concern due to the magnitude of this
highly exothermic reaction, which can spread to adjacent cells or
ignite nearby combustible material.
[0126] In order to mitigate (e.g., reduce or eliminate) thermal
runaway, damage initiators 180 can be introduced to electrodes
(e.g., the cathode 110, the anode 120, or both), or be placed near
electrodes so that as the battery 100 is subjected to external
mechanical loading or overheating the damage initiators modify the
electrode and/or the electrolyte to cause an increase in internal
impedance. Examples of mechanical loading include impact,
collision, crushing, penetration, tension, compression, torsion,
bending, and indentation. Examples of overheating include
temperature increases caused by electro-chemical reactions or
caused by the environment. As the internal impedance increases,
exothermic electrochemical reactions are reduced, leading to
reduced heat generation rate.
[0127] An example of such damage imitators is passive damage
initiators. Passive damage initiators initiate cracking or voiding
in electrodes upon external loading, and such cracks and/or voids
increase the internal impedance of the electrode. Such additives
are also known as cracks or voids initiators (CVIs). The electrode
damages can be caused by debonding of CVI-electrode interfaces,
fracture and rupture of CVI, stress concentration caused by CVI,
and/or local shear, bending, torsion, compression and tension
caused by stiffness mismatch of CVI and electrode. Examples of
passive additives include solid or porous particles, solid or
hollow/porous fibers and tubes, solid or hollow/porous platelets,
arrays, clusters, trusses, and layers or layer stacks formed by
these materials. Passive additives can be formed from carbon
materials such as graphite, carbon nanotubes, activated carbons,
and carbon blacks. Passive damage initiators can also be formed
from ceramic materials such as silica, alumina, Al.sub.2TiO.sub.5,
ALN, B.sub.4C, BaTiO.sub.3, BeO, Bi.sub.12SiO.sub.20,
Bi--Sr--Ca--Cu--O, BN, cBN, CdS/Cu.sub.2S, CdTe, CeO.sub.2, CIGS,
CoOx, cordierite, CrO.sub.2, Fe.sub.2O.sub.3, GaAs, GaN, hBN,
hydroxy apatite, La--Ba--Cu--O, LaCrO.sub.3, Li silicate, Li--Al
silicate, LiNbO.sub.2, LiNbO.sub.3, LiTaO.sub.3, MgO, mica, MoS,
MoSi.sub.2, NiOx, PbTiO.sub.3, PLZT, PZT, Si.sub.3N.sub.4, SiC,
SnO.sub.2, SrTiO.sub.3, TiB, TiC, UC, UO.sub.2, V.sub.2O.sub.5,
Y.sub.2O.sub.2S, Y.sub.2O.sub.3, Y--Ba--Cr--O, zeolite, ZnO, ZnS
and ZrO.sub.2. Passive damage initiators of metallic materials such
as iron, steel, ferrous metals, aluminum, copper, zinc, titanium,
other nonferrous metals, alloys of these materials, copper based
shape memory alloys, NiTi and their derivatives are also possible.
Polymer materials such as epoxy, polyester resins, elastomers,
thermoplastics such as butyl rubber, polyethylene, polyurethane are
also suitable. Other suitable polymers can include thermoplastics,
thermosets and elastomers, such as derivatives of natural products
which include naturally occurring resins, derivative of cellulose,
derivatives of vegetal proteins; polyaddition resins which include
polyolefins such as polyethylene, polypropylene and polybutylene,
polyvinyls such as polyvinyl ethers, polyvinyl chloride and
polyvinyl fluoride, polyvinylidenes such as polyvinylidene chloride
and polyvinylidene fluoride, polyvinyl derivatives such as
polyvinyl alcohol and polyacetals, styrenics such as polystyrene,
acrylonitrile-butadiene-styrene and styrene-butadiene,
fluorocarbons such as polytetrafluoroethylene and fluorinated
ethylene propylene, acrylics such as polymethylmethacrylate,
coumarone-indenes; polycondensation resins which include phenolics
such as phenol-formaldehyde and pesorcinol formaldehyde,
aminoplastics such as urea-formaldehyde, melamine-formaldehyde and
melamine-phenolics, furan resins such as phenol-furfural,
polyesters such as alkyd resins and polycarbonates, polyethers such
as polyformaldehydes and polyglycols, polyurethanes, polyamides,
polyimides, polyaramides, sulfones such as polysulfones,
polyethersulfone and polyphenylsulfone, epoxy resins, polysiloxanes
such as silicones. In general, composites made of any combination
of above materials can be used to form passive additives. The sizes
of these passive additives can span from less than 1 nanometer to
the electrode thickness.
[0128] In addition to the passive additives, the mechanical
strength of electrodes can also be reduced by reducing the
percentage content of binder in the electrode or by using binders
having a lower molecular weight. When the mechanical strength of
electrodes is reduced, the binder itself effectively becomes a
CVI.
[0129] In addition, as the shapes of membrane separator, battery
case, or charge collector are non-uniform, they can promote local
shear, bending, tension, compression, or torsion of electrodes when
the battery is deformed, and thus cause damages (e.g., widespread
damages) in electrodes. As the widespread damage is promoted, the
non-uniform shaped membrane separators, battery cases, and charge
collectors themselves become CVIs.
[0130] Another type of additives are active damage initiators which
damage electrodes, electrolyte, or membrane separator as the
battery is subjected to external thermal or mechanical loadings. As
mechanical loading or temperature reaches a threshold value, the
active damage initiators actively deform, change volume, move,
decompose, melt, soften, or break; they may release chemicals such
as FEA, TRR, EA, or GGA, or absorb electrolyte. These thermally or
mechanically triggered active additives form cracks and/or voids in
electrodes, interact or react with an electrolyte or an electrode,
interact or react with a membrane separator, interact or react with
a charge collector and a battery cell case, change electrode
conductivity, generate gas or change conductivity of electrolyte,
absorb electrolyte, change configuration of membrane separator,
change an internal environment in a battery cell, and/or change the
configuration of electrodes, which would increase the internal
impedance of the battery and, thus, reduce heat generation
associated with possible internal shorting.
[0131] An active damage initiator can produce a significant volume
or shape change upon a mechanical or thermal loading. Active damage
initiators can include solid or porous particles, solid or hollow
beads, solid or hollow/porous fibers and tubes, solid or
hollow/porous layers and platelets, arrays, clusters, trusses, and
layers or layer stacks formed by shape or volume changing
materials. Active damage initiators can be formed from shape-memory
alloys such as Ni--Ti, Ni--Ti--Pd, Ni--Ti--Pt, Ni--Ti--Hf,
Ni--Ti--Zr, Ni--Ti--Cu, Ni--Ti--Nb, Cu--Al--Ni, Cu--Al--Nb/Ag,
Co--Al, Co--Ni--Al/Ga, Fe--Mn--Si, Ni--Al, Ni--Mn, Ni--Mn--Ga,
Zr--Cu, Ti--Nb, U--Nb, Ti--Au, Ti--Pd, Ti--Pt--Ir, Ta--Ru or Nb--Ru
alloys. The active damage initiators can also be formed from
shape-memory polymers and elastomers such as polyurethanes, epoxy,
copolyesterurethane, polynorbornene, poly(trans-isoprene),
polystyrene, polybutadiene, polyester, poly(methyl methacrylate),
ethylene vinyl acetate-nitrile rubber, ethylene vinyl
acetate-chlorosulfonated polyethylene, poly-caprolactone,
polyethylene terephthalate-polyethylene glycol, polyethylene
terephthalate, poly ethylene oxide, polyvinyl chloride, poly
(ketone-co-alcohol), polytetramethylene glycol, and copolymers
containing these components. Shape-memory ceramics and glasses,
such as ceria-zirconia, yttria-zirconia, magnesia-zirconia,
dicalcium silicate, lanthanum niobium oxide, yttria niobium oxide,
lanthanide sesquioxide, and enstatites can also form active damage
initiators. The active damage initiators can also include ionic
solids such as KCl, KI, NaCl, NaClO.sub.3, and NaBrO.sub.3.
Thermally or mechanically responsive carbon materials, such as
expandable graphite can be used. The active damage initiators can
also include elastic energy storage materials, such as springs. The
spring configurations include coils, rings, clips, and folded or
curved wires and sheets. The active damage initiators can be moved,
deformed, or broken by elastic energy storage materials inside or
near electrodes. The active damage initiators can contain
low-melting-point polymers, metals/alloys, and ceramics, such as
bismuth alloys. The damage initiators can be formed by using a
mechanically or thermally expandable, deformable, or breakable
carrier to contain functional fillers, such as phase change
materials, large-thermal-expansion-coefficient materials, or
swelling materials that can be involved in physical or chemical
processes of large volume/shape changes; such processes include
melting, boiling, or chemical reactions leading to large volume
changes. The carrier is optional if the fillers are stable and
non-reactive under battery operation conditions. The damage
initiators can be modified, coated, or decorated by carbon,
metallic, or glass materials, such as particles and fibers or
carbon blacks, carbon nanotubes, metallic fibers, activated
carbons. The active damage initiators can be placed inside or near
electrodes. If membrane separate, charge collector, or battery case
is made of these materials, the membrane separator, charge
collector, or battery case essentially becomes an active damage
initiator. The damage initiators can be placed in or near the
membrane separator to block ion transport.
[0132] Mechanical loading of rods fabricated using only cathode
materials and rods having embedded passive additives are
investigated. FIG. 2A shows a rod 210 fabricated using only cathode
material, without any passive additives. The cathode material was
collected from a cathode sheet 212 (shown in FIG. 2E) used in
cylindrical 18650 cells and ground into fine particles 214 (shown
in FIG. 2F). The cathode sheet 212 was obtained from American
Lithium Energy Co. of Vista, Calif.
[0133] FIG. 3 shows a system 300 used for fabricating cylindrical
rods. The fine particles 214 were compressed into the cylindrical
rod 210 by, for example, first placing the particles in a stainless
steel cell 310 using two pistons 312 and 314. In the examples shown
below, an inner diameter 318 of the stainless steel cell and the
outer diameter 316 of the piston 314 were 0.5'' (12.7 mm) The
pistons 312 and 314 were used to compress the cell 310 by a machine
320 (e.g., an Instron 5582 machine) with the piston velocity of 5
mm/min. Once the force impacted on the fine particles 214 reaches 4
kN, the piston force was removed.
[0134] A similar process is used to form a cylindrical rod 220
shown in FIG. 2B. Cathode material is mixed with activated carbon
(AC) particles to form the cylindrical rod 220. The AC particles
can act as damage initiators, or CVI. The AC particles can be
introduced in lower mass ratio than the cathode material, for
example, a ratio of cathode material to AC of 30:1, 20:1, 10:1, or
5:1 may be used. The mass ratio of cathode material to AC was 10:1
in cylindrical rod 220. AC having small particle size can be used,
for example, sizes of 500 microns or less, 200 microns or less, 100
microns or less, or 50 microns or less. The AC particles in
cylindrical rod 220 were around 150 microns. The AC powders were
obtained from J. T. Baker (Product No: E343), a division of Avantor
Performance Materials of Center Valley, Pa. The mixture containing
the cathode material and the AC powders was placed in the stainless
steel cell 310 and compressed using the apparatus 300 as outlined
above in reference to the cylindrical rod 210. A few samples are
shown in FIG. 2B.
[0135] Cathode material is mixed with solid silica particles to
form a cylindrical rod 230 shown in FIG. 2C using a similar method
as described above in reference to cylindrical rod 220. The solid
silica powders can act as damage initiators, or CVI. The solid
silica powders can be introduced in lower mass ratio than the
cathode material, for example, a ratio of cathode material to solid
silica powders of 30:1, 20:1, 10:1, or 5:1 may be used. The mass
ratio of cathode material to solid silica powders was 10:1 in
cylindrical rod 230. Solid silica powders having small particle
size can be used, for example, sizes of 500 microns or less, 200
microns or less, 100 microns or less, 50 microns or less, or 20
microns or less. The solid silica powders in cylindrical rod 230
were around 44 microns. The solid silica powders were obtained from
Sigma-Aldrich Co. of St. Louis, Mo. (Product No.: 342890). No
cracks could be observed after cylindrical rod 230 was formed using
the apparatus of 300. The total mass of the rod was 1.91 g, and the
rod has a height of 7.20 mm.
[0136] Cathode material is mixed with porous silica particles to
form a cylindrical rod 240 shown in FIG. 2D using a similar method
as described above in reference to cylindrical rod 220. The porous
silica particles can act as damage initiators, or CVI. The porous
silica particles can be introduced in lower mass ratio than the
cathode material, for example, a ratio of cathode material to
porous silica particles of 30:1, 20:1, 10:1, or 5:1 may be used.
The mass ratio of cathode material to porous silica particles was
10:1 in cylindrical rod 240. Porous silica particles having small
particle size can be used, for example, sizes of 500 microns or
less, 200 microns or less, 100 microns or less, 50 microns or less,
20 microns or less, 10 microns or less, 5 microns or less, or 1
micron or less. The average particle size of the porous silica
particles in cylindrical rod 240 were around 2 microns. The porous
silica particles were obtained from Performance Process Inc., of
Mundelein, Ill. No cracks could be observed after cylindrical rod
240 was formed using the apparatus of 300. The total mass of the
rod was 1.69 g, and the rod has a height of 7.38 mm.
[0137] Table 1 summarizes the parameters used to fabricate the
cylindrical rods shown in FIGS. 2A-2D.
TABLE-US-00001 FIG. 2A 2B 2C 2D CVI None Activated Solid silica
Porous silica carbon (AC), particles Size of CVI 150 micron 44
micron 2 micron Ratio of -- 10:1 10:1 10:1 cathode material:CVI
[0138] The cylindrical rod 210 without any AC particles was quite
strong. In contrast, the cylindrical rod 220 containing the AC
particles cracked easily as a small mechanical loading below 0.5
MPa was applied, as shown in FIGS. 5C-5F, indicating that AC
particles weakened the electrode sample.
[0139] A small-scale drop tower apparatus 400 as shown in FIG. 4A
was used to impact each of the rods 220-240. The apparatus 400
includes a titanium (Ti) hammer 410 (shown in FIG. 4B), which was
dropped on the top of the sample (i.e., each of rods 220-240)
placed at a location 420 under the hammer 410. A drop distance 430
measured from a lower end of the hammer 410 to a top surface of
each of the rods 220-240 was 100 mm The mass of the titanium hammer
410 was 473 g. The Ti hammer has a diameter of 22.45 mm and a
height of 265.4 mm.
[0140] After each drop-tower test for a corresponding one of the
cylindrical rods 220-240, the rods 220-240 were observed under a
SEM.
[0141] FIG. 5A shows an edge 510 of the cylindrical rod 210, which
does not contain any CVI, after the drop-tower test. While there
were a few cracks 512 and 514 near the edge 510 of the cylindrical
rod 210, a central part 516, shown in FIG. 5B was free of
cracks.
[0142] FIG. 5C shows an edge 518 of the cylindrical rod 230, which
contains solid silica powders after the drop-tower test. A number
of cracks 520, 522 were observed at the center of the cylindrical
rod 230 (shown in FIG. 5D), and more cracks 524, 526 were observed
near the edge 518.
[0143] FIG. 5E shows a number of cracks 540 having crack sizes and
crack density that were larger than those of cylindrical rod 230
containing solid silica powders. The cracks 540 were developed
around the porous silica particles 542 as shown in FIG. 5F.
[0144] Cylindrical rods containing cathode materials that have been
soaked in a solvent are also investigated. Ground anode particles
were mixed with AC particles, and the AC particles can be
introduced in lower mass ratio than the cathode material, for
example, a ratio of cathode material to AC particles powders may be
30:1, 20:1, 10:1, or 5:1. The mass ratio of cathode material to AC
particles was 19:1 in a cylindrical rod 620. The AC powders were
obtained from J. T. Baker (Product No: E343) a division of Avantor
Performance Materials of Center Valley, Pa., with a particle size
was around 150 microns. Various solvents can be used, 2 mL of
propylene carbonate anhydrous (Sigma-Aldrich Co. of St. Louis, Mo.,
310328), were added in the mixture. The presence of the solvent in
the cylindrical rod 620 is used to better approximate the working
conditions of an electrode.
[0145] The mixture containing the solvent was sealed using the
apparatus 300 similar to the method described in reference to rod
220. No cracks could be observed in cylindrical rod 620. A
reference cylindrical rod 610 (shown in FIG. 6A) was prepared using
a similar process with only the cathode material and the solvent
(i.e., without the addition of AC particles). The mass of the
reference cylindrical rod 610 was 1.11 g and has a diameter of
12.86 mm and a height of 3.16 mm. The mass of the porous silica
modified cylindrical rod 620 was 1.30 g and has a diameter of 12.90
mm and a height of 4.06 mm.
[0146] The ground cathode particles were mixed with porous silica
particles to form cylindrical rod 630 shown in FIG. 6C. The porous
silica particles can be introduced in lower mass ratio than the
cathode material, for example, a ratio of cathode material to
porous silica particles may be 30:1, 20:1, 10:1, or 5:1. The mass
ratio of cathode material to porous silica was 9:1 in cylindrical
rod 630. The porous silica powders, which served as CVI, were
received from Performance Process Inc., of Mundelein, Ill. The
average particle size was around 2 microns. Two mL electrolyte
solvent, propylene carbonate anhydrous (Sigma-Aldrich Co. of St.
Louis, Mo., 310328), were added in the mixture to resemble the wet
state of electrodes in a working battery. No cracks could be
observed in cylindrical rod 630, as shown in FIG. 6C when the rod
630 was removed from the apparatus 300. The total mass of the
cylindrical rod 630 was 1.36 g and has a diameter of 12.85 mm and a
height of 4.74 mm.
[0147] Table 2 summarizes the parameters of cylindrical rods
containing cathode materials that have been soaked in a
solvent.
TABLE-US-00002 FIG. 6A 6B 6C Damage Initiator None AC Porous silica
Size of damage -- 150 microns 2 microns initiator Ratio of cathode
-- 19:1 9:1 material:Damage initiator Solvent Propylene Propylene
Propylene carbonate carbonate carbonate anhydrous anhydrous
anhydrous Amount of Solvent 2 ml 2 ml 2 ml Mass of Rod 1.11 g 1.36
Dimension of Rod 12.86 mm .times. 3.16 12.85 .times. 4.74
[0148] FIG. 7A shows an SEM image of the reference cylindrical rod
610 before the drop-tower test. After the drop-tower test, few
cracks 710 could be observed in the SEM image in FIG. 7B at the
edge 712 of the reference cylindrical rod 610. FIG. 7C is the SEM
image of a center 714 portion of the cylindrical rod 610. The
center portion 714 was generally free of cracks. In contrast, a
large number of cracks 716 were observed at the center of the
cylindrical rod 620 shown in FIG. 7E and more cracks 718 were
observed near an edge 720 as shown in FIG. 7D. The cracks 718 were
developed around an AC particle 722 as shown in FIGS. 7F and 7G.
FIG. 7F shows the edge 720 of the cylindrical rod 620 while FIG. 7G
shows a center portion of the cylindrical rod 620.
[0149] FIG. 7H is an SEM image of an edge 724 of the cylindrical
rod 630 that contains porous silica particles 726 after the
drop-tower test. FIG. 7I is an SEM image of a center portion of the
cylindrical rod 630 after the drop-tower test, a large number of
cracks 728 were observed and the size and density of the cracks
were much larger than those of the cylindrical rod 620. The cracks
were developed around the porous silica particles 726, as shown in
FIGS. 7J and 7I. FIG. 7J is a close up of cracks 728 around a
porous silica particle 726 near the edge 724 of the cylindrical rod
620. FIG. 7K is a close up of cracks 728 around a porous silica
particle 726 in the center portion of the cylindrical rod 620.
[0150] Cylindrical rods containing anode materials that were soaked
in a solvent are also investigated. Anode materials for the
cylindrical rod 910 shown in FIG. 9A were collected from an anode
sheet obtained from American Lithium Energy Co. of Vista, Calif.
The anode sheet was grounded and the ground anode particles were
mixed with porous silica particles at a mass ratio of anode
material to porous silica of 9:1. The porous silica powders were
received from Performance Process Inc., of Mundelein, Ill. The
average particle size was around 2 microns. Two mL electrolyte
solvent, propylene carbonate anhydrous (Sigma-Aldrich Co. of St.
Louis, Mo., 310328), were added in the mixture to resemble the wet
state of electrodes in a working battery. The mixture of anode
materials, porous silica particles and solvent were compressed to
form cylindrical rod 910 using the apparatus 300 in a similar
fashion as that used to form cylindrical rod 620 described above.
No cracks could be observed in cylindrical rod 910 after it was
formed using apparatus 300. A reference cylindrical rod 810, as
shown in FIG. 8A was prepared through a similar process by using
only the anode material and the solvent, without the addition of
porous silica particles. The mass of the reference cylindrical rod
810 was 1.28 g, and the rod has a diameter of 13.02 mm and a height
of 5.55 mm. The mass of the cylindrical rod 910 was 1.33 g, and its
diameter was 12.97 mm and its height was 6.22 mm. A 46-range
digital multimeter from RadioShack of Fort Worth, Tex., was used to
measure an electrical resistance of the cylindrical rod 910
containing the porous silica. Before impact, the measured
resistance was about 200 k.OMEGA.. After the impact test, the
electrical resistance was 28.7 M.OMEGA., which is a few hundred
times higher than the resistance before the impact test. In
contrast, the electrical resistance of the reference cylindrical
rod 810 without porous silica fillers did not vary much.
[0151] Table 3 summarizes the parameters used to fabricate the
cylindrical rods shown in FIGS. 8A and 9A.
TABLE-US-00003 FIG. 8A 9A CVI None Porous silica Size of CVI -- 2
microns Ratio of anode -- 9:1 material:CVI Solvent Propylene
Propylene carbonate carbonate anhydrous anhydrous Amount of Solvent
2 ml 2 ml Mass of Rod 1.28 g 1.33 Dimension of Rod 13.02 mm .times.
5.55 12.97 mm .times. 6.22
[0152] Before impact, there were no cracks in the reference
cylindrical rod 810 as shown in FIG. 8B. After impact, cracks 812
were observed near the edge 814 of the reference cylindrical rod
810, as shown in FIG. 8C. However, the center portion 816 of the
sample was free of cracks, as shown in FIG. 8D.
[0153] In the cylindrical rod 910 containing porous silica
particles, a large number of cracks 912 were observed in a center
area 914 of the cylindrical rod 910, as shown in FIG. 9B, and more
cracks 912 were observed near an edge 916 as shown in FIG. 9C. The
cracks 912 were developed around silica particles 918 as shown in
FIGS. 9B and 9C.
[0154] After the impact test, the electrical resistance of the
cylindrical rod 910 containing porous silica increased
significantly by more than a few hundred times than before the
impact test; while that of the reference cylindrical rod 810
without porous silica fillers did not vary much.
[0155] Carbon nanotubes (CNT) can also be used as CVI to modify
electrodes. In some embodiments, polyvinylidene fluoride (PVDF) can
be used as a binder in the electrode. A binder in an electrode is
typically a polymer adhesive that holds the particles of active
materials together. The binder amount is usually 3-6% of electrode
mass. An exemplary preparation method includes using an active
material, either NCM-04ST LiNi.sub.0.5Mn.sub.0.3Co.sub.0.2O.sub.2
(NMC532) obtained from TODA America of Battle Creek, Mich. (for
cathode samples) or EQ-Lib-CMSG graphite obtained from MTI Corp. of
Richmond, Calif. (for anode samples), and mixing the active
material with polyvinylidene fluoride (PVDF) obtained from
Sigma-Aldrich Co. of St. Louis, Mo. (Product No. 182702) and
CNERGY-C65 conductive carbon (C) obtained from Timcal of Cleveland,
Ohio. The mixture was soaked up in 1-Methyl-2-pyrrolidinone (NMP)
(Sigma-Aldrich Co. of St. Louis, Mo., Product No. 328634). The
weight ratios of the solid components were NMC532: PVDF: C=93:4:3
and Graphite: PVDF: C=93:6:1 for cathode and anode samples,
respectively. For each 0.2 g of PVDF, 5 ml NMP was used. The solid
components and NMP was thoroughly mixed in a 50 ml beaker at room
temperature by a mechanical stirrer (PCVSl, IKA) at 400 rpm for 30
minutes, and then conductive carbon was added, stirred at 500 rpm
for another 30 minutes. After that, the active material was added,
which was further homogenized by stirring at 600 rpm for 90
minutes. Cathode slurry was cast on a 15 .mu.m thick aluminum foil
(MTI EQ-bcaf-15u-280) by a film casting doctor blade (MTI
EQ-Se-KTQ-150A) with the slurry thickness of 400 nm. Anode slurry
was cast on a 9 nm thick copper foil (MTI EQ-bccf-9u) with the
slurry thickness of 200 .mu.m. The electrode sample was dried in
vacuum at 80.degree. C. for 24 hours. After drying, the thickness
of the electrode sample was about 150 .mu.m for cathode and 100
.mu.m for anode, respectively. The dried sample was compressed by
two flat stainless steel plates in a Type-5582 Instron machine at
30 MPa, with the loading rate of 0.5 mm/min. In the following
sections, all electrode samples were processed through similar
procedures, except that extra functional components might be added
and special configurations might be employed. During testing, the
electrode samples were soaked in an electrolyte, to simulate the
working condition in a battery cell. The electrolyte was 1 M
LiFP.sub.6 dissolved in ethylene carbonate (EC) and ethyl methyl
carbonate (EMC). The mass ratio of EC:EMC was 1:1.
[0156] The electrode sample was impacted by a stainless steel rod
with a length of 305 mm and the mass of 7.7 kg, from a drop
distance in the range from 4-22 mm.
[0157] FIG. 10A is an optical microscope image of the electrode
containing SWCNT after impact. Cracks 1090 were observed. Under
similar impact conditions, a reference electrode (not shown)
prepared using a similar procedure but without the addition of CVI
showed no evidence of damage.
[0158] FIG. 10B shows various electrode samples modified by 3 wt %
MWCNT after impact tests. Ten electrodes formed a layer stack and
was impacted simultaneously, labeled as samples 1-10, respectively.
The drop distance was 12 mm. Multiple cracks 1090 are visible in
most of the electrode layers.
[0159] In addition to the passive additives described above, active
additives that are thermally triggered have also been
investigated.
[0160] Expandable graphite (EG) can be employed as a thermally
triggered CVI. The thickness of EG can expand by a few times when
it is heated to or above a critical temperature. FIG. 11A shows an
electrode 1010 containing expandable graphite (EG) before the
application of heat. The electrode 1010 includes 5 wt % of
conductive EG particles, obtained from ACS Material LLC of Medford,
Mass.; Products No. EG-110-230, having a size of 80 mesh. NCM532 is
the cathode materials for electrode 1010. The selected EG has an
critical temperature at about 110.degree. C. The modified cathode
layers were dried at 40.degree. C. for 72 hours. The low drying
temperature prevents premature damages. The electrode 1010 was then
heated to 120.degree. C. and kept for 20 minutes. The graphite
expanded and generated cracks/voids 1020 as expected upon heating,
as shown in FIG. 11B.
[0161] Shape memory materials (SMM) can also be used as a thermally
triggered CVI. A SMM can be deformed below the transition
temperature and recover to the original shape above the transition
temperature. FIG. 12A is an optical microscope image of an
originally straight SMM wire from Fort Wayne Metals; Products No.:
82909 that was cut into segments that are 10 mm long. The
transition temperature was about 90.degree. C. At room temperature,
the wire segments were bent into coils 1110, and embedded into 150
.mu.m thick cathode layers to form an electrode 1112. The electrode
1112 was heated to 120.degree. C. and kept for 5 minutes. After
heating, the SMM coils 1110 tend to change back to straight, either
causing in-plane cracking and voiding 1114 as shown in FIG. 12B or
causing out-of-plane damages 1116 as shown in FIG. 12C.
[0162] Hollow or porous beads, particles, tubes, pipes, fibers,
plates, pads, pouches, boxes, and other containers with sizes
ranging from a few nanometers to the battery cell size can be used
to hold fire-extinguishing agents (FEA), thermal runaway retarders
(TRR), electrolyte absorbers (EA), and/or gas generation agents
(GGA). Upon mechanical loading or thermal loading (when temperature
rises) FEA, TRR, EA, or GGA can be released from the hollow or
porous containers into the battery system to put out fire and/or
reduce heat generation rate in the battery. Such containers can be
placed in the cathode, anode, electrolyte, membrane, or other
locations, both inside or outside the battery cells. The containers
can be distributed uniformly, or form aggregates that have either
random or textured distribution patterns.
[0163] Thermal runaway retarders (TRR) can include chemicals that
can change salvation structures of ions, such as aromatic amine,
N,N-Diethylaniline, N,N-diethyl-p-phenylenediamine,
2-(2-methylaminoethyl)pyridine,
5-amino-1,3,3-trimethylcyclohexanemethylamine,
(1R,2R)-(+)-1,2-diphenylethylenediamine,
N,N'-diphenylethylenediamine, tryptamine, 2-benzylimidazoline,
1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indole,
4,4'-diaminodiphenylmethane,
1-(N-boc-aminomethyl)-4-(aminomethyl)benzene and pyridine; lightly
cross-linked polymers, which include but not limited to epoxy,
polyester, poly (vinyl ester), polyurethane, bakelite, polyimide,
urea methanal and melamine, or co-polymers containing these
components.
[0164] TTR can also include surfactants, such as sodium lauryl
sulfate, sodium dodecylbenzenesulfonate, oleic acid, Span.TM.
series, Atlas.TM. G series, Tween.TM. series, Solulan.TM. series,
Splulan.TM. series, Brij.TM. series, Arlacel.TM. series, Emcol.TM.
series, Aldo.TM. series, Atmul.TM. series surfactant.
[0165] TTR can also include chemicals that can change the viscosity
of electrolyte solutions. These TTR can include solid state
aromatic amine such as n,n'-diphenylethylenediamine,
4,4'-diaminodiphenylmethane and
1-(N-Boc-aminomethyl)-4-(aminomethyl)benzene; nonionic surfactants
such as 2,4,7,9-Tetramethyl-5-decyne-4,7-diol, polyethylene glycol
hexadecyl ether, polyoxyethylene nonylphenyl ether, sorbitan
laurate and polyethylene glycol sorbitan monolaurate; viscous
liquids such as glycerol, glycerin, and other polyols.
[0166] TTR can also be chemicals such as acid, bases, ketone,
alcohol and organic phosphorus compounds as well as their
halogenated derivatives.
[0167] The gas generation agents (GGA) and associated processes can
include catalytic decomposition of hydroxyl peroxide with potassium
iodine or manganese dioxide as catalyst; polyurethane foaming;
extinguishing agents in fire extinguishing processes such as
ammonium sulfate with sodium bicarbonate solution; organic solvents
having boiling points ranging from 60-250.degree. C. such as
acetone, methanol, ethanol, acetonitrile, benzene, carbon
tetrachloride, cyclohexane, cthyl acetate, isopropyl alcohol,
tert-butyl alcohol and triethylamine; thermal decomposition of
ionic solids, e.g. carbonates such as sodium bicarbonate and
potassium bicarbonate; thermal decomposition of permanganate salts
such as silver permanganate, ammonium permanganate, nickel
permanganate and copper permangantes; thermal decomposition of
ammonium salts such as ammonium nitrate, ammonium chromates,
ammonium citrate, ammonium carbonate and ammonium bicarbonate;
thermal decomposition of coordination compounds such as
diaquaamminecobalt chloride, diaquaamminecobalt bromide, cobalt
ammines chloride, cobalt ammines nitrate, chromium ammines
thiocyanate and nickel ammines chloride; thermal decomposition of
perchlorates such as nitronium/nitrosonium perchlorates; thermal
decomposition of oxalates such as silver oxalate; thermal
decomposition of azide such as sodium azide, potassium azide,
lithium azide and ammonium azide; thermal decomposition of organic
compounds such as azodicarbonamide, azobisisobutyronitrile,
n,n'-dinitrosopentamethylenetetramine, 4,4'-oxydibenzenesulfonyl
hydrazide, p-toluenesulfonyl hydrazide; thermal decomposition of
hydrated salts such as ammonium copper sulfate hexahydate, nickel
sulfate hexahydrate, calcium sulfate hemihydrate, lithium sulfate
monohydrate, sodium carbonate monohydrate, borax, nickel oxalate
dehydrate, soium carbonate perhydrate, alkali (Na, K, Rb, NH4)
oxalate perhydrate and calcium sulfite.
[0168] Gas generation agents (GGA) can also include bubble
generation promoters (BGP), materials that promote bubble
nucleation and growth when the electrolyte is heated, such as
particles, fibers, rods, layers and layer stacks, platelets of
rough, cracked, or dimpled surfaces or surface coatings. BGP can be
inside or near electrodes, inside or near membrane separator. If
the membrane separator can promote bubble generation as electrolyte
is heated, the membrane separator essentially becomes a BGP.
[0169] The electrolyte absorbers (EA) can include particles,
platelets, beads, tubes, fibers, membranes, disks, and monoliths of
metallic materials, glass materials, carbon materials, ceramics,
polymers, elastomers, alumina, zeolites, polyelectrolytes, polymers
with charged or polar side groups, silica and aerogels, and
composite materials. These materials can be porous, hollow, or
solid. The electrolyte absorbers (EA) can also include
superabsorbents such as poly (sodium acrylate), poly acrylic
acid-sodium styrene sulfonate (AA-SSS), poly acrylic acid and
2-acrylamido-2-methylpropane sulfonic acid (AA-AMPS),
2-Acrylamido-2-methylpropane sulphonic acid and poly(ethylene
glycol) copolymer, poly (potassium, 3-sulfopropyl acrylate-acrylic
acid) gels, poly (AMPS-TEA-co-AAm), (poly ethylene glycol methyl
ether methacrylate-acrylic acid) copolymers,
methacrylamidopropyltrimethyl ammonium chloride (MAPTAC). The
electrolyte absorbents (EA) can include particles, platelets,
tubes, membranes, disks, and monoliths of polyelectrolytes
including protines such as bovine serum albumin, casein,
lactoferrin; polycations containing aromatics or having a charged
backbone such as poly(-vinylpyridine) (PVP), x,y-ionene,
poly(N,N-diallyl-N,N-dimethyl-ammonium chloride) (PDMDAAC);
polycations with quaternary ammonium side chains such as
poly(trimethylammonio ethylmethacrylate) (PTMAEMA) and its
copolymers; polycations without steric stabilizer such as modified
polyaspartamide (PAsp), poly(amidoamine)s (PA) with different side
groups, poly(N-isopropylacryl amide) (PNIPAM) and derivatives,
poly(dimethylaminoethyl-L-glutamine) (PDMAEG) and copolymers,
Poly(methyl methacrylate) (PMMA) and methacrylamide derivatives,
poly[2-(dimethylamino)ethyl methacrylamide] (PDMAEMA) and
derivatives; polycations with steric stabilizer such as
poly(L-lysine) (PLL) and derivatives, amino acid-based polymers;
Amphiphilic polycations such as poly(N-ethyl-4-vinylpyridinium
bromide) (PEVP) and copolymers, poly(-vinylpyridine) (PVP)
copolymers; Polyamphoters such as modified poly(1,2-propylene
H-phosphonate), silica and aerogels, and composite materials. These
materials can be porous or solid. The electrolyte absorbents (EA)
can also include superabsorbents such as poly (sodium acrylate),
poly acrylic acid-sodium styrene sulfonate (AA-SSS), poly acrylic
acid and 2-acrylamido-2-methylpropane sulfonic acid (AA-AMPS),
2-Acrylamido-2-methylpropane sulphonic acid and poly(ethylene
glycol) copolymer, poly (potassium, 3-sulfopropyl acrylate-acrylic
acid) gels, poly (AMPS-TEA-co-AAm), (poly ethylene glycol methyl
ether methacrylate-acrylic acid) copolymers,
methacrylamidopropyltrimethyl ammonium chloride (MAPTAC), or
co-polymers containing these components.
[0170] Fire-extinguishing agents (FEA) include dry chemicals such
as sodium bicarbonate, monoammonium phosphate, potassium
bicarbonate, potassium bicarbonate and urea complex, potassium
chloride; foams such as Aqueous Film Forming Foam (AFFF),
Alcohol-Resistant Aqueous Film Forming Foams (AR-AFFF), Film
Forming Fluoroprotein (FFF), Compressed Air Foam System (CAFS);
[0171] FEA can be class D fire extinguishing powders such as sodium
chloride, copper, graphite based, sodium carbonate based
powders.
[0172] The containers of FEA, TRR, EA, or GGA can be weakened,
softened, melted, broken apart upon mechanical or thermal loading.
For FEA, TRR, EA, or GGA that are stable under normal battery
operation conditions (i.e. operating at a normal battery operation
temperature range, or without intense mechanical loading), or for
FEA, TRR, EA, or GGA that do not interact with active materials and
the electrolyte in the battery, the containers are optional. The
containers can be hollow carriers; organic surface coatings,
inorganic surface coatings, blockers, tubes, pouches, boxes, beads,
particles, disks, layers, stoppers, and surface layers of absorbed
or adsorbed particles, carbon nanotubes or other tubes, fibers,
rods, and platelets. The containers can be made of fusible alloys
such as bismuth alloys, polymers such as paraffin and polyethylene,
elastomers, glass materials, gelatin, carbon materials, ceramics,
smart materials such as smart alloys, polymers, elastomers, and
ceramics, e.g. Ti--Ni alloy, and hydrogels; and composite
materials. The containers can be either electrically conductive or
nonconductive. The containers can be either thermally conductive or
nonconductive. The containers can be used to carry the damage
initiators disclosed above, or additives such as positive thermal
coefficient materials, phase change materials, and membrane
blocking materials. Multiple layers or sections of containers can
be used.
[0173] FIG. 13A shows a battery 1300 having an anode 1301 and a
cathode 1302 both of which includes containers 1304. The containers
1304 can hold FEA, TRR, EA, or GGA. In FIG. 13A, the containers are
uniformly distributed in the electrodes. However, the containers
can be aggregates distributed in a random pattern or aggregates
that are distributed in a specific pattern.
[0174] Containers for holding FEA, TRR, EA, or GGA can be, for
example, hollow microfibers (HMF). HMF alone can also serve as a
CVI. The processing and testing procedure for exemplary electrodes
were similar with that of CNT modified electrodes described above
in FIGS. 10A and 10B, except that the CNT was replaced by HMF. The
HMF can be either clear fused quartz (CFQ) fibers, for example,
obtained from Produstrial of Fredon, N.J. (Product No. 134316),
which have an inner diameter (ID) of 50 microns and an outer
diameter (OD) of 80 microns; or borosilicate glass fibers of
similar ID and OD, provided by Produstrial of Fredon, N.J. (Product
No. 134270). The HMF content was either 3 wt % or 5 wt % of
electrode mass.
[0175] At a HMF content of 3 wt %, pronounced cracks 1310 are
observed after impact test done at a drop distance of 12 mm as
shown in FIG. 13B. Ten layers of HMF modified electrodes (samples
1-10) form a layer stack, and are impacted by the hammer Extensive
cracking are observed in most of the layers.
[0176] FIG. 14A shows a series of three optical microscope images
of electrodes containing 3% hollow hydrophilic glass fibers when
impacted at a drop distance of 7 mm. FIG. 14B shows a series of
three optical microscope images of electrodes containing 3% hollow
hydrophoboic glass fibers 1410 when impacted at a drop distance of
7 mm. As shown in FIGS. 14A and B, the fibers are broken, and any
chemicals initially contained inside would be released.
[0177] FIG. 15A shows a glass tube 1510 having an OD of 1.69 mm, ID
of 1.55 mm, height of 5.65 mm, and mass of 0.010 g that can contain
FEA, TRR, EA, or GGAand be embedded in the battery.
[0178] FIG. 15B shows a miniature capsule 1520 filled with 7 mg of
neat water, which serves as an analog of functional chemicals such
as FEA, TRR, EA, or GGA. The liquid was sealed in the capsules by
thin layers of epoxy adhesive 1522 at both ends.
[0179] FIG. 15C shows a miniature capsule 1530 filled with 9 mg of
a surfactant, Adogen 464 obtained from Sigma-Aldrich Co. of St.
Louis, Mo. (Product No. 856576), which is another analog of
functional chemicals such as FEAs.
[0180] The filled miniature capsules 1520 and 1530 were embedded
into cathode material cluster saturated with solvent, to form a
cylindrical rod 1540, as shown in FIG. 15D. The sample preparation
procedure is similar with that of FIG. 6A, except the additives are
filled miniature capsules.
[0181] FIG. 15E shows the impacted cylindrical rod 1550 containing
broken miniature capsules 1552 and the sealed liquids were
released.
[0182] FIG. 15F shows the impacted cylindrical rod 1550 being
shattered into small pieces 1560 after being impacted by the hammer
at a drop distance of 12 mm. The shattering of the rods indicates
that the capsules acted as damage initiators, as the electrode
samples without the capsules had few cracks.
[0183] The mechanical impacted samples were also characterized by
optical microscope and typical photos are shown in FIGS. 15G and
15H. A broken empty capsule 1564 is shown in FIG. 15H.
[0184] FIG. 16A shows a glass tube 1610 having an OD of 3.97 mm, ID
of 2.40 mm, a height of 3.97 mm, and a mass of 0.091 g. The glass
tube forms a miniature capsules 1620 when filled by 7 mg of porous
silica particles obtained from Performance Process Inc., of
Mundelein, Ill., as shown in FIG. 16B. The porous silica particles
are analogs of condensed aerosol fire suppression agent. The solid
agent was sealed in the capsule by thin layer of epoxy adhesives
1622 from both ends.
[0185] The filled miniature capsules 1620 were embedded into
cathode material soaked up by solvent, to form cylindrical rod 1630
as shown in FIG. 16C. The cylindrical rod 1630 was then impacted by
the drop tower 400.
[0186] As shown in FIG. 16D, the miniature capsules 1620 were
broken and the sealed porous silica particles 1624 were released
and exposed.
[0187] In general, a damage initiator needs not be an additive. For
example, reducing the amount or the molecular weight (MW) of the
binder in electrodes can also weaken (i.e., reduce) the mechanical
strength of the electrode upon mechanical impact. In other words,
the reduced binder phase effectively becomes the CVI.
[0188] An example of the binder is PVDF. The processing and testing
procedures for fabricating an electrode in this case are similar as
before, except that no CVI particles are added.
[0189] FIG. 17A shows the impact result from an electrode having a
high molecular weight (MW) binder. The MW in this case was 540 k
and was obtained from Sigma-Aldrich Co. of St. Louis, Mo. Ten
layers of electrodes form a layer stack (samples 1-10) and are
impacted by the hammer simultaneously. FIG. 17B shows impact
results from an electrode having a low molecular weight (MW)
binder. The mass ratio of binders to CB to active material remained
the same as that used in the electrodes shown in FIG. 17A but the
MW of the binder was reduced to 180 k, which is also provided by
Sigma-Aldrich Co. of St. Louis, Mo. (Product No. 427152). The MW of
the electrodes shown in FIG. 17B is lower than the MW of the binder
used for the electrodes shown in FIG. 17A by 2/3. FIG. 17B show
that the electrodes with lower MW binder suffer more cracking when
subjected to an impact from a drop distance of 12 mm while the
electrodes made from the larger MW binders were not damaged.
[0190] FIGS. 17C-F show samples made from different binder amounts
of 6 wt % i.e., a mass ratio of binder:CB:active material was
6:1:93, 5 wt % (i.e., binder:CB:active material of 5:1:94) , 4.5 wt
% (i.e., binder:CB:active material of 4.5:1:94.5) and 4 wt % (i.e.,
binder:CB:active material of 4:1:95), respectively when subjected
to an impact from a drop distance of 12 mm. FIGS. 17D and 17A show
that electrodes having the lowest (4 wt %) amount of binder exhibit
extensive cracking damages after impact, while electrodes having
the highest (6 wt %) amount of binder were not damaged.
[0191] While this specification contains many implementation
details, these should not be construed as limitations on the scope
of the invention or of what may be claimed, but rather as
descriptions of features specific to particular embodiments of the
invention. Certain features that are described in this
specification in the context of separate embodiments can also be
implemented in combination in a single embodiment. Conversely,
various features that are described in the context of a single
embodiment can also be implemented in multiple embodiments
separately or in any suitable subcombination. Moreover, although
features may be described above as acting in certain combinations
and even initially claimed as such, one or more features from a
claimed combination can in some cases be excised from the
combination, and the claimed combination may be directed to a
subcombination or variation of a subcombination.
[0192] The damage initiators can be triggered mechanically or
thermally; that is, damage initiators can deform, displace, break,
melt or soften, and/or expose FEA/TRR/EA/GGA to the interior of
battery, and/or absorb electrolytes upon thermal or mechanical
loading.
[0193] FIG. 18A shows a wavy nitinol wire 1800 (Niti#5, FWMetal)
having a diameter of 75 microns and a phase transition temperature
of 95.degree. C. was embedded in electrode 1820, as shown in FIG.
18B. The nitinol wire is straight at temperatures over 95.degree.
C. and has a wavy shape at room temperature. The nitinol wire was
placed on a charge collector before slurry casting, and
subsequently vacuum dried together with the slurry. The nitinol
wire could also be directly compressed into the dried electrode at
30 MPa, as the electrode sample was compressed after drying. The
electrode with embedded nitinol wire was heated by a hotplate to
100.degree. C. In a few minutes, cracks 1804 caused by the shape
change of the embedded nitinol wire are observed, as shown in FIG.
18Cs.
[0194] Damage initiators can be an elastic energy storage
material/device (EESMD), such as a spring. An EESMD can be
prestressed and be confined by a locking component, which can be
weakened, softened, broken, or melt upon mechanical or thermal
loading before releasing the stored elastic energy to cause damages
in an electrode. EESMD can be placed in an electrode or near an
electrode. If charge collectors, membrane separators, or battery
cases are prestressed and the associated stored elastic energy can
be released upon mechanical or thermal loading, they essentially
become EESMD. EESMD can include pre-stressed or pre-compressed
particles, fibers, tubes, rods, strings, layers, layer stacks,
platelets of polymers, elastomers, metals and alloys, ceramics,
glass materials, carbon materials, polyurethane, natural rubber,
polybutadiene, thermoset resins, epoxy, polyester, and co-polymers
containing these components.
[0195] EESMD can include springs, rings, wires, strings, beads,
rods, beams, meshs, arrays, and trusses that can be deformed and
pre-stressed elastically. They can be made of polymers, elastomers,
ceramic materials, metallic materials, glass materials, carbon
materials, or composite materials. They can be confined by locking
components, which can include hollow carriers, coatings, blockers,
and stoppers. The materials of above mentioned confining
methods/materials can be metallic materials, polymers, elastomers,
wax, epoxy, gelatin, glass materials, carbon materials, ceramics,
and composite materials.
[0196] As the elastic energy is released form an EESMD, it can
directly cause damages in electrode, or deform or displace other
damage initiators in electrode, indirectly causing damages (e.g.,
widespread damages) in electrode. The damage initiators can be
threads, meshes, arrays, and multilayers with various dimensions,
surface properties and features, and shapes and configurations. The
materials of the damage initiators can include polymers,
elastomers, glass materials, carbon materials, metals and alloys,
ceramics, and composite materials.
[0197] FIG. 19A shows a prestressed coil spring 1904 embedded in a
cathode sample 1902. The coil spring 1904 was made from a stainless
steel wire having a diameter of 125 microns (9882K11, from
McMaster-Carr of Santa Fe Springs, Calif.). The curvature of the
soil spring 1904 was about 1 mm. One end of the coil spring was
initially fixed on an aluminum charge collector by duct tape. The
other end of the coil spring was fixed by the locking component
1906, which can be, for example, a drop of paraffin having a
melting point below 100.degree. C. Initially, the coil spring 1904
was prestressed, so that its curvature can be changed by about 10%.
Cathode slurry was casted on top of the prestressed spring, dried
and compressed at 30 MPa. The electrode sample was then soaked up
by 20 ml ethyl methyl carbonate (EMC) (from Sigma-Aldrich Co. of
St. Louis, Mo., product number 754935), and covered by a 0.5 mm
thick, 20 mm.times.10 mm glass plate. The electrode sample was
heated by a Cimarec digital HP 131125 hot plate from Thermo
Scientific of Waltham, Mass., to 100.degree. C., and the paraffin
melted. The stored elastic energy in the spring was released and it
relaxes to a position 1908 shown in FIG. 9, causing evident damages
in the electrode, such as cracks 1910, as shown in FIG. 19B. The
resistivity of the damaged electrode increased by more than 4 times
compared to an undamaged electrode.
[0198] Other damage initiators, such as strings, threads, meshs,
and arrays and layer stacks of them, can be deformed or displaced
by elastic energy storage materials/devices upon mechanical or
thermal loading. The dimensions, surface features and properties,
and shapes and configuration of the damage initiators can be
controlled in broad ranges. The damage initiators can also be
deformed or displaced by thermally or mechanical responsive
components other than EESMD.
[0199] FIG. 20A shows a copper wire with knots 2002, embedded in an
electrode sample 2004 The wire has a diameter of 80 microns. The
electrode sample 2004 was processed using standard procedures,
except that in the final compression step the wire was compressed
into the dried electrode sample at 30 MPa by an Instron 5582
machine. After compression, the electrode sample soaked up 200
microliter of electrolyte. Damages 2006 observed in the electrode
sample 2004, as shown in FIG. 20B, were caused by displacement of
the wire, as the wire was pulled by a coil spring placed next to
the electrode sample. FIG. 20B Damages in electrode caused by
displacing the copper-wire damage initiator The resistivity of the
damaged electrode increased by more than 4 times compared to an
undamaged electrode.
[0200] Damage initiators (DI) can be distributed non-uniformly
inside an electrode or near an electrode. DI can have heterogeneous
and/or anisotropic materials, components, or shapes and
configurations. Upon mechanical loading, such damage initiators or
the electrode materials near such damage initiators deform or
displace differently in different areas and/or along different
directions, so that local compression, tension, shear, torsion,
bending, cracking, voiding, or debonding are promoted. Such
heterogeneous or anisotropic damage initiators can be fibers,
wires, wedges, strips, tubes, meshes, arrays, and trusses. When a
charge collector, a membrane separator, or a battery case has
heterogeneous or anisotropic shapes, surface features,
configurations, or materials or components, which can trigger
internal damages in battery, they essentially become damage
initiators. Such damage initiators and their components can be made
of metallic materials, polymers, elastomers, carbon materials,
glass materials, ceramics, and composite materials.
[0201] FIG. 21A shows an example of an aluminum (Al) sheet 2108
having copper (Cu) wires 2106 as damage initiators. The diameter of
the Cu wire can be 500 microns and the spacing between the wires
can also be about 500 microns. The Cu wires were firmly glued on
the Al substrate 2108. A cathode sample was processed using
standard procedures on an Al charge collector 2104. The cathode
sample thickness was about 150 microns. The size of the electrode
sample was 10.times.10 mm. The electrode layer 2102 soaked up 20
microliter of an electrolyte. The electrode sample was placed on
top of an array of copper wires 2106. This setup was impacted using
the same table top drop tower as shown in FIG. 4A. The drop weight
and distance were 405 g and 15 mm, respectively. Upon impact, as
the electrode layer 2102 was forced to bend and shear around the Cu
wires 2106. Damages (e.g., cracks 2110) in an electrode layer and
debonding (e.g., region 2112 in FIG. 21C) between the electrode
layer 2102 and the charge collector 2104 were observed, as shown in
FIG. 21B and FIG. 21C, respectively. The resistivity of the damaged
electrode increased by more than 3 times compared to the
resistivity of an undamaged electrode. Using a soft impactor, e.g.
a polyurethane hammer, helps promote widespread damage. The soft
impactor models soft inner layers of battery case or other soft
components near electrodes. If the shape or surface pattern of a
charge collector or a battery case is non-flat and wavy, such as
S-shaped or dotted-shaped, similar electrode damages can be
achieved.
[0202] A wavy shaped substrate, e.g. a charge collector 2202, as
shown in FIG. 22A, was tested as damage initiator. To control the
shape of the charge collector 2202, two arrays of copper wires
sandwich a copper foil. The copper wire has a diameter of 500
microns, and the spacing between adjacent wires was also 500
microns. The top and bottom arrays were misaligned so that the top
array can move into the gaps of the bottom array when an external
compression force is applied through a steel plate. After the
charge collector 2202 was deformed, the steel plate and the top
array of copper wires were removed. A cathode sample was prepared
on the wavy charge collector 2202 using standard procedures, except
that the final compression at 30 MPa was performed by a 10 mm thick
polyurethane plate, instead of a steel plate. After compression,
the electrode sample soaked up 20 ml of EMC. Then, the bottom array
of copper wires was removed, as shown in FIG. 22A. A wavy electrode
film 2204 was impacted by the table top drop tower shown in FIG.
4A. The drop weight and distance were 405 g and 30 mm,
respectively. After impact, a large number of cracks 2206 were
observed in the electrode sample, as shown in FIG. 22B. The
resistivity of the damaged electrode increased by more than 2 times
than compared to the electrode prior to the impact.
[0203] Upon mechanical or thermal loading, if gas generation agents
(GGA) can be released or exposed to an electrode, an electrolyte,
and/or a membrane separator, GGA can generate gas inside the
battery andblock ion transport. In one example, ammonium carbonate
was employed as GGA. About 50 mg of ammonium carbonate was immersed
in 5 ml 50% ethyl methyl carbonate (EMC) solution of ethylene
carbonate (EC). The system was heated to 100.degree. C. Ammonium
carbonate thermally decomposed and generated carbon dioxide gas,
beginning at about 80.degree. C. A large number of gas bubbles were
generated.
[0204] In one example, 10 mg of ammonium carbonate powders, with
the average particle size of about 80 .mu.m, were compressed onto a
cathode film, using a type 5582 Instron machine at 30 MPa. The
cathode diameter was 16 mm, and its thickness was about 150 .mu.m.
The cathode film was supported by a copper (Cu) disk charge
collector. The Cu disk diameter was 18 mm, and its thickness was 3
mm. A 25 .mu.m thick Celgard 2325 PP/PE/PP membrane separator was
firmly compressed on the top of the cathode film. The lateral
surface of the cathode and the membrane separator was strengthened
by a layer of Devcon 5 min epoxy glue. The glue layer thickness was
nearly 30 .mu.m. About 0.5 ml electrolyte, 1 M LiFP6 dissolved in
EC:EMC (1:1 by weight), was dropped on the electrode-membrane
system by a plastic disposable pipette. A second Cu disk charge
collector with a diameter of 16 mm and a thickness of 3 mm was
placed on top of the membrane separator. The two Cu charge
collectors were connected by a RadioShack 22-812 multimeter, to
measure the impedance of the electrode-membrane system. This setup
could be heated by a Barnstead Cimarec digital HP 131125 hot plate
from Thermo Scientific of Waltham, Massachusetts. The impedance was
measured at both room temperature (25.degree. C.) and 100.degree.
C. It could be clearly observed that as temperature increased, gas
bubbles generated between the membrane and the electrode block ion
transport and, increase an impedance of the system. At room
temperature, the measured impedance was 5 k.OMEGA.; at 100.degree.
C., the impedance increased by more than 2 times to 12 k.OMEGA..
The gas bubble size was around a few hundred microns.
[0205] Upon mechanical or thermal loading, if electrolyte absorbers
(EA) can be released or be exposed to an electrolyte, the amount of
electrolyte available for ion transport would be reduced, creating
the condition of "electrolyte starvation" (ES) in membrane
separator and/or in electrodes, or both. The flammability of the
electrolyte absorbed in EA is also reduced, as it is isolated from
the environment.
[0206] FIG. 23A shows nanoporous carbon 2302 (BP2000 obtained from
Cabot Corporation of Boston, Mass.) that can be used to absorb
electrolyte. The particles have nanopores of nanometer scale a
specific surface area that is around 2000 m.sup.2/g;, and a
porosity of 80%. As the particles 2302 are exposed to the
electrolyte solution, the nanopores 2304 are filled by the liquid
spontaneously. Thereafter, electrolyte starvation is developed in
other areas. About 0.1 g of BP 2000 particles were placed in a
sample glass container. About 0.4 mL 1 M LiPF6 in EC/EMC
electrolyte (LP 50, BASF) was dropped onto the particles. The
electrolyte was completely absorbed by the BP 2000 particles in a
few seconds. Similar to carbon black particles, porous silica or
silica gel can be used as electrolyte absorber. In one example,
iTNM-b 2306 was used as EA. The raw material was obtained from JLK
Industries of Coopersburg, Pa. (Product No. PP-35-HP-HS-18). The
received nanoporous silica particles were heated in vacuum at
450.degree. C. for 12 h. The nanoporous silica particles have the
pore size around 100 nm. About 0.1 g of nanoporous silica particles
were placed in a glass container. About 0.4 mL 1 M LiPF6 in EC/EMC
electrolyte (LP 50 from BASF of Ludwigshafen, Germany) was dropped
onto the particles. The electrolyte was completely absorbed by the
nanoporous silica particles in a few seconds to form electrolyte
soaked nanoporous silica particle 2308.
[0207] FIG. 24A shows a solution 2402 of 0.05 g ammonium carbonate
in 5 ml of 50% ethyl methyl carbonate (EMC) and 50% ethylene
carbonate (EC) before and after heating at 100.degree. C. A larger
amount of liquid was used to show more clearly the generated gas
bubbles 2404 Ammonium carbonate thermally decomposed and generated
carbon dioxide, beginning at about 80.degree. C., as shown in FIG.
24B.
[0208] Similarly, while operations are depicted in the drawings in
a particular order, this should not be understood as requiring that
such operations be performed in the particular order shown or in
sequential order, or that all illustrated operations be performed,
to achieve desirable results. In addition, the systems and
techniques described above can be combined with the subject matter
of the patent application entitled, "Rate-sensitive and
self-releasing battery cells and battery-cell structures as
structural and/or energy-absorbing vehicle components", filed on
the same day. For example, a non-chemical approach to developing
low-cost, robust, and multifunctional battery systems for electric
vehicles can be enabled.
[0209] The first material/device includes an elastic energy storage
material or device. The elastic energy storage material or device
can be placed inside or near electrode.
[0210] The elastic energy storage material or device can be
confined by a locking component. Upon mechanical or thermal
loading, the locking component can be weakened, softened, or broken
part, so as to release elastic energy.
[0211] The elastic energy storage material or device can directly
release elastic energy into the electrode, or deform or displace
other damage initiators. Both cause widespread damage in
electrode.
[0212] The damage initiators in electrode can deform, displace,
debond, or fracture or rupture upon mechanical or thermal loading,
aided by another material or device.
[0213] The elastic energy storage material or device can be charge
collector, membrane separator, battery case, or a part of them, as
they are prestressed and released upon mechanical or thermal
loading.
[0214] The first material/device includes a heterogeneous or
nonuniformly distributed, or anisotropic damage initiators. The
damage initiators can be placed inside or near electrodes.
[0215] Upon mechanical loading, the damage initiators or electrode
materials near such damage initiators deform or displace
heterogeneously or anisotropically (i.e. differently in different
areas or along different directions), causing widespread damage, as
local bending, torsion, shear, compression, tension, debonding,
cracking, or voiding is promoted. As charge collectors, membrane
separators, or battery case have heterogeneous or anisotropic
shapes or surface patterns or materials/components, they can become
such damage initiators.
[0216] Using a soft impact promotion layer helps promote widespread
damaging.
[0217] The electrolyte absorbers include materials that can absorb
electrolyte, materials that prevent electrolyte from being
available for ion transport, materials that isolate electrolyte
from the rest of battery system.
[0218] The gas generation agents include materials that generate
gas phase or gas bubbles, which can be placed in electrode,
membrane separator, or electrolyte.
[0219] The container can be used to house any materials that
mitigate thermal runaway. The container of the second material is
optional if the second material is stable and non-reactive under
battery operation condition.
[0220] The first material includes an elastic energy storage
material or device. The elastic energy storage material or device
can be placed inside or near electrode.
[0221] The elastic energy storage material or device can be
confined by a locking component. Upon mechanical or thermal
loading, the locking component can be weakened, softened, or
broken, so as to release elastic energy.
[0222] The elastic energy storage material or device can directly
release elastic energy into the electrode, or deform or displace
other damage initiators, causing widespread damage in
electrode.
[0223] The damage initiators in or near electrode can deform,
displace, debond, or fracture or rupture upon mechanical or thermal
loading.
[0224] The damage initiators in or near electrode can deform,
displace, debond, or fracture or rupture upon mechanical or thermal
loading, aided by another material or device in battery.
[0225] The elastic energy storage material or device can be charge
collector, membrane separator, battery case, or a part of them, as
they are prestressed and released upon mechanical or thermal
loading.
[0226] The first material includes a heterogeneous or nonuniformly
distributed, or anisotropic damage initiators, which can be placed
inside or near electrodes.
[0227] Upon mechanical loading, the damage initiators or electrode
materials near such damage initiators deform or displace
heterogeneously or anisotropically (i.e. differently in different
areas or along different directions), causing widespread damage, as
local bending, torsion, shear, compression, tension, debonding,
cracking, or voiding is promoted. Charge collectors, membrane
separators, or battery case having heterogeneous or anisotropic
shapes or surface patterns or materials/components can become such
damage initiators.
[0228] Using soft impact promotion components helps promote
widespread damaging. Particular embodiments of the invention have
been described.
[0229] Changing a configuration of an electrolyte can include
creating bubbles, absorbing liquids, increasing resistivity, or
changing viscosity,
[0230] Other embodiments are within the scope of the following
claims. For example, the actions recited in the claims can be
performed in a different order and still achieve desirable
results.
* * * * *