U.S. patent application number 12/622788 was filed with the patent office on 2011-05-26 for pressure-relief mechanism to improve safety in lithium-polymer battery cells.
This patent application is currently assigned to APPLE INC.. Invention is credited to Ramesh C. Bhardwaj, Taisup Hwang, Richard M. Mank.
Application Number | 20110123844 12/622788 |
Document ID | / |
Family ID | 44062314 |
Filed Date | 2011-05-26 |
United States Patent
Application |
20110123844 |
Kind Code |
A1 |
Bhardwaj; Ramesh C. ; et
al. |
May 26, 2011 |
PRESSURE-RELIEF MECHANISM TO IMPROVE SAFETY IN LITHIUM-POLYMER
BATTERY CELLS
Abstract
The disclosed embodiments relate to a battery cell which
includes a weakness for relieving pressure. This battery cell
includes a jelly roll comprising layers which are wound together,
including a cathode with an active coating, a separator and an
anode with an active coating. The jelly roll also includes a first
conductive tab coupled to the cathode and a second conductive tab
coupled to the anode. The jelly roll is enclosed in a flexible
pouch, wherein the first and second conductive tabs extend through
seals in the pouch to provide terminals for the battery cell. This
pouch includes a weakness which yields when internal pressure in
the pouch exceeds a threshold to create a hole which releases the
internal pressure.
Inventors: |
Bhardwaj; Ramesh C.;
(Fremont, CA) ; Hwang; Taisup; (Santa Clara,
CA) ; Mank; Richard M.; (Sunnyvale, CA) |
Assignee: |
APPLE INC.
Cupertino
CA
|
Family ID: |
44062314 |
Appl. No.: |
12/622788 |
Filed: |
November 20, 2009 |
Current U.S.
Class: |
429/56 ;
29/623.2; 429/94 |
Current CPC
Class: |
H01M 50/116 20210101;
H01M 10/058 20130101; H01M 50/543 20210101; Y10T 29/4911 20150115;
H01M 10/34 20130101; Y02E 60/10 20130101; H01M 10/052 20130101;
H01M 50/3425 20210101; H01M 50/557 20210101; H01M 50/124 20210101;
H01M 50/209 20210101 |
Class at
Publication: |
429/56 ;
29/623.2; 429/94 |
International
Class: |
H01M 2/12 20060101
H01M002/12 |
Claims
1. A battery cell with a weakness for relieving pressure,
comprising: a jelly roll comprising layers which are wound
together, including a cathode with an active coating, a separator,
and an anode with an active coating; a pouch, which encloses the
jelly roll, wherein the pouch is flexible; a first conductive tab
coupled to the cathode; and a second conductive tab coupled to the
anode; wherein the first and second conductive tabs extend through
seals in the pouch to provide terminals for the battery cell; and
wherein the pouch includes a weakness which yields when internal
pressure in the pouch exceeds a threshold to create a hole which
releases the internal pressure.
2. The battery cell of claim 1, wherein the pouch includes multiple
weaknesses at different locations on the pouch.
3. The battery cell of claim 1, wherein the weakness includes one
of: a V-shaped notch cut into a seal for the pouch; a half-circle
cut into a seal for the pouch; a corner of the pouch which is cut;
a pattern of tiny holes formed in a seal for the pouch; and a
thinned region of the pouch material.
4. The battery cell of claim 1, wherein the weakness is located on
one of: a side seal for the pouch; a terrace seal for the pouch; a
corner of the pouch; a fold in the pouch material; and a location
on a surface of the pouch which is not part of a seal.
5. The battery cell of claim 1, wherein the pouch is comprised of:
a layer of aluminum; and a layer of polypropylene.
6. The battery cell of claim 1, wherein the battery cell is one of:
a lithium-polymer battery cell; and a silver-zinc battery cell.
7. A battery pack comprising one or more battery cells coupled
together and enclosed in a hard case, wherein each of the one or
more battery cells includes: a jelly roll comprising layers which
are wound together, including a cathode with an active coating, a
separator, and an anode with an active coating; a pouch, which
encloses the jelly roll, wherein the pouch is flexible; a first
conductive tab coupled to the cathode; and a second conductive tab
coupled to the anode; wherein the first and second conductive tabs
extend through seals in the pouch to provide terminals for the
battery cell; and wherein the pouch includes a weakness which
yields when internal pressure in the pouch exceeds a threshold to
create a hole which releases the internal pressure.
8. The battery pack of claim 7, wherein the one or more battery
cells are coupled together: in series; in parallel; or in series
and parallel.
9. The battery pack of claim 7, wherein each pouch includes
multiple weaknesses at different locations on the pouch.
10. The battery pack of claim 7, wherein the weakness includes one
of: a V-shaped notch cut into a seal for the pouch; a half-circle
cut into a seal for the pouch; a corner of the pouch which is cut;
a pattern of tiny holes formed in a seal for the pouch; and a
thinned region of the pouch material.
11. The battery pack of claim 7, wherein the weakness is located on
one of: a side seal for the pouch; a terrace seal for the pouch; a
corner of the pouch; a fold in the pouch material; and a location
on a surface of the pouch which is not part of a seal.
12. The battery pack of claim 7, wherein the pouch is comprised of:
a layer of aluminum; and a layer of polypropylene,
13. The battery pack of claim 7, wherein each battery cell is one
of: a lithium-polymer battery cell; and a silver-zinc battery
cell.
14. A portable computing device, comprising: a processor; a memory;
and a battery pack, which includes one or more battery cells
coupled together; wherein each of the one or more battery cells
includes: a jelly roll comprising layers which are wound together,
including a cathode with an active coating, a separator, and an
anode with an active coating; a pouch, which encloses the jelly
roll, wherein the pouch is flexible; a first conductive tab coupled
to the cathode; and a second conductive tab coupled to the anode;
wherein the first and second conductive tabs extend through seals
in the pouch to provide terminals for the battery cell; and wherein
the pouch includes a weakness which yields when internal pressure
in the pouch exceeds a threshold to create a hole which releases
the internal pressure.
15. The portable computing device of claim 14, wherein the portable
device includes one of: a laptop or notebook computer system; a
personal digital assistant; and a cellular telephone.
16. A method for assembling a battery cell, comprising: obtaining a
jelly roll comprising layers which are wound together, including a
cathode with an active coating, a separator, and an anode with an
active coating, wherein the jelly roll includes a first conductive
tab coupled to the cathode and a second conductive tab coupled to
the anode; obtaining a pouch to accommodate the jelly roll, wherein
the pouch is flexible; and sealing the jelly roll in the pouch,
wherein the pouch is sealed so that the first and second conductive
tabs extend through seals in the pouch to provide terminals for the
battery cell; wherein the pouch includes or is configured to
include one or more weaknesses, which yield when internal pressure
in the pouch exceeds a threshold to create a hole which releases
the internal pressure.
17. The method of claim 16, wherein the weakness in the pouch is
created: prior to sealing the jelly roll in the pouch; or after
sealing the jelly roll in the pouch.
18. The method of claim 16, wherein creating the weakness in the
pouch involves creating multiple weaknesses at different locations
on the pouch.
19. The method of claim 16, wherein the weakness includes one of: a
V-shaped notch cut into a seal for the pouch; a half-circle cut
into a seal for the pouch; a corner of the pouch which is cut; a
pattern of tiny holes formed in a seal for the pouch; and a thinned
region of the pouch material.
20. The method of claim 16, wherein the weakness is located on one
of: a side seal for the pouch; a terrace seal for the pouch; a
corner of the pouch; a fold in the pouch material; and a location
on a surface of the pouch which is not part of a seal.
21. The method of claim 16, wherein the pouch is comprised of: a
layer of aluminum; and a layer of polypropylene,
22. The method of claim 16, wherein the battery cell is one of: a
lithium-polymer battery cell; and a silver-zinc battery cell.
Description
BACKGROUND
[0001] 1. Field
[0002] The disclosed embodiments relate to techniques for improving
safety in rechargeable lithium-polymer battery cells. More
specifically, the disclosed embodiments relate to the design of a
pressure-relief mechanism which improves the safety in
lithium-polymer battery cells.
[0003] 2. Related Art
[0004] Rechargeable batteries are presently used to provide power
to a wide variety of portable electronic devices, including laptop
computers, cell phones, PDAs, digital music players and cordless
power tools. The most commonly used type of rechargeable battery is
a lithium battery, which can include a lithium-ion or a
lithium-polymer battery.
[0005] A potential safety issue can arise if there is a gas buildup
within a rechargeable lithium battery cell. This can occur, for
example, if the cell is overcharged, if there is a short within the
cell, or if the cell is left uncharged for a significant period of
time. This type of gas buildup can potentially cause the battery
cell to swell or even to explode, which can seriously damage the
portable electronic device, and may even start a fire.
[0006] To alleviate this problem, cylindrical lithium-ion battery
cells are often equipped with a vent valve to release the internal
pressure in the battery cell when a gas buildup occurs. However,
there exist no comparable pressure-relief mechanisms for
lithium-polymer batteries, which are becoming increasingly popular
in portable electronic devices. A lithium-polymer battery is
typically enclosed in a flexible pouch, which is lightweight and
inexpensive to manufacture. However, no pressure-relief mechanism
has been developed for these pouches so far.
SUMMARY
[0007] The disclosed embodiments relate to a battery cell which
includes a weakness for relieving pressure. This battery cell
includes a jelly roll comprising layers which are wound together,
including a cathode with an active coating, a separator, and an
anode with an active coating. The jelly roll also includes a first
conductive tab coupled to the cathode and a second conductive tab
coupled to the anode. The jelly roll is enclosed in a flexible
pouch, wherein the first and second conductive tabs extend through
seals in the pouch to provide terminals for the battery cell. This
pouch includes a weakness which yields when internal pressure in
the pouch exceeds a threshold to create a hole which releases the
internal pressure.
[0008] In some embodiments, the pouch includes multiple weaknesses
at different locations on the pouch.
[0009] In some embodiments, the weakness can include: a V-shaped
notch cut into a seal for the pouch; a half-circle cut into a seal
for the pouch; a pattern of tiny holes formed in a seal for the
pouch; and a thinned region of the pouch material.
[0010] In some embodiments, the weakness can be located on: a side
seal for the pouch; a terrace seal for the pouch; a corner of the
pouch; a fold in the pouch material; and a location on a surface of
the pouch which is not part of a seal.
[0011] In some embodiments, the pouch is comprised of a layer of
aluminum and a layer of polypropylene.
[0012] In some embodiments, the battery cell is a lithium-polymer
battery cell, or a silver-zinc battery cell.
BRIEF DESCRIPTION OF THE FIGURES
[0013] FIG. 1 illustrates a battery cell in accordance with the
disclosed embodiments.
[0014] FIG. 2 illustrates a battery cell with V-shaped notches cut
into seals for a pouch in accordance with the disclosed
embodiments.
[0015] FIG. 3 illustrates a battery cell with half-circles cut into
seals for a pouch in accordance with the disclosed embodiments.
[0016] FIG. 4 illustrates a battery cell with patterns of tiny
holes formed in a seal for a pouch in accordance with the disclosed
embodiments.
[0017] FIG. 5 illustrates a battery cell including a pouch with
corner cuts in accordance with the disclosed embodiments.
[0018] FIG. 6 illustrates a battery cell with weak regions formed
in the pouch material in accordance with the disclosed
embodiments.
[0019] FIG. 7 illustrates a portable computing device in accordance
with the disclosed embodiments.
DETAILED DESCRIPTION
[0020] The following description is presented to enable any person
skilled in the art to make and use the disclosed embodiments, and
is provided in the context of a particular application and its
requirements. Various modifications to the disclosed embodiments
will be readily apparent to those skilled in the art, and the
general principles defined herein may be applied to other
embodiments and applications without departing from the spirit and
scope of the disclosed embodiments. Thus, the disclosed embodiments
are not limited to the embodiments shown, but are to be accorded
the widest scope consistent with the principles and features
disclosed herein.
[0021] The data structures and code described in this detailed
description are typically stored on a computer-readable storage
medium, which may be any device or medium that can store code
and/or data for use by a computer system. The computer-readable
storage medium includes, but is not limited to, volatile memory,
non-volatile memory, magnetic and optical storage devices such as
disk drives, magnetic tape, CDs (compact discs), DVDs (digital
versatile discs or digital video discs), or other media capable of
storing code and/or data now known or later developed.
[0022] The methods and processes described in the detailed
description section can be embodied as code and/or data, which can
be stored in a computer-readable storage medium as described above.
When a computer system reads and executes the code and/or data
stored on the computer-readable storage medium, the computer system
performs the methods and processes embodied as data structures and
code and stored within the computer-readable storage medium.
Furthermore, the methods and processes described below can be
included in hardware modules. For example, the hardware modules can
include, but are not limited to, application-specific integrated
circuit (ASIC) chips, field-programmable gate arrays (FPGAs), and
other programmable-logic devices now known or later developed. When
the hardware modules are activated, the hardware modules perform
the methods and processes included within the hardware modules.
Battery Cell
[0023] FIG. 1 illustrates a battery cell 100 in accordance with the
disclosed embodiments. Battery cell 100 includes a jelly roll 101
comprising a number of layers which are wound together, including a
cathode with an active coating, a separator, and an anode with an
active coating. Jelly rolls are well known in the art and will not
be described further. During assembly of battery cell 100, jelly
roll 101 is enclosed in a flexible pouch, which is formed by
folding a flexible sheet along a fold line 108. For example, the
flexible sheet can be comprised of aluminum with a polymer film,
such as polypropylene. After the flexible sheet is folded, the
flexible sheet can be sealed, for example by applying heat along
side seals 102 and along a terrace seal 104.
[0024] Note that jelly roll 101 includes conductive tabs 103
coupled to the cathode and the anode. These conductive tabs 103
extend through seals in the pouch (for example, formed using
sealing tape 104) to provide terminals for battery cell 100.
[0025] Also note that a battery pack can be formed by coupling
together a number of such battery cells: in series, in parallel, or
both in series and in parallel. The coupled cells can then be
enclosed in a hard case.
Battery Cell Including a Weakness
[0026] As mentioned above, a gas buildup can potentially occur
within battery cell 100 if: battery cell 100 is overcharged; there
is a short within battery cell 100; or battery cell 100 is left
uncharged for a significant period of time. This gas buildup can
potentially cause the battery cell to swell or even explode. To
deal with this problem, the pouch includes one or more preformed
weaknesses which yield when internal pressure in the pouch exceeds
a threshold value to create a hole which releases the internal
pressure.
[0027] There are a number of different ways to create such a
weakness. For example, a number of V-shaped notches, including
V-shaped notch 202, can be cut into the seals for the pouch as is
illustrated in FIG. 2. These V-shaped notches can be cut using some
type of cutting tool after the pouch is formed. Alternatively, a
number half-circles, including half-circle 302, can be cut into the
seals for the pouch as is illustrated in FIG. 3. In yet another
embodiment which is illustrated in FIG. 4, instead of cutting
notches in the seals, weaknesses can be created by forming a
pattern of tiny holes 402 in the seals.
[0028] Weaknesses can also be formed at other locations on the
battery cell pouch. For example, FIG. 5 illustrates a battery cell
having a pouch with weaknesses which are formed as corner cuts 502.
Alternatively, FIG. 6 illustrates a battery cell with weak regions
602 which are formed at various locations on the pouch material.
These weak regions 602 can be formed, for example, by thinning the
pouch material.
[0029] In general, such weaknesses can be formed at any location on
the battery pouch, including at: a side seal for the pouch; a
terrace seal for the pouch; a corner of the pouch; a fold in the
pouch material; and any location on a surface of the pouch which is
not part of a seal. Moreover, although a number of different types
of weaknesses are illustrated in FIGS. 2-6, in general any type of
weakness which yields to internal pressure in the battery cell can
be used by the disclosed embodiments.
Computing Device
[0030] The above-described rechargeable battery cell can generally
be used in any type of electronic device. For example, FIG. 7
illustrates a portable computing device 700 which includes a
processor 702, a memory 704 and a display 708, which are all
powered by a battery 706. Battery 706 comprises a battery pack,
which includes multiple battery cells that are coupled together in
series and/or in parallel.
[0031] The foregoing descriptions of embodiments have been
presented for purposes of illustration and description only. They
are not intended to be exhaustive or to limit the present
description to the forms disclosed. Accordingly, many modifications
and variations will be apparent to practitioners skilled in the
art. Additionally, the above disclosure is not intended to limit
the present description. The scope of the present description is
defined by the appended claims.
* * * * *