U.S. patent application number 16/875932 was filed with the patent office on 2020-09-03 for methods for making reference electrode and lithium ion battery having the same.
This patent application is currently assigned to Tsinghua University. The applicant listed for this patent is Tsinghua University. Invention is credited to ZHENG-YU CHU, XU-NING FENG, JIAN-QIU LI, LAN-GUANG LU, MING-GAO OUYANG.
Application Number | 20200280051 16/875932 |
Document ID | / |
Family ID | 1000004842080 |
Filed Date | 2020-09-03 |
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United States Patent
Application |
20200280051 |
Kind Code |
A1 |
CHU; ZHENG-YU ; et
al. |
September 3, 2020 |
METHODS FOR MAKING REFERENCE ELECTRODE AND LITHIUM ION BATTERY
HAVING THE SAME
Abstract
The present disclosure relates to methods for making a reference
electrode and a lithium ion battery having the reference electrode.
The reference electrode obtained has a long service life, moreover,
the manufacturing process is simple and can meet the industrial
production requirements, making the production and the application
of the lithium-ion battery with the reference electrode
possible.
Inventors: |
CHU; ZHENG-YU; (Beijing,
CN) ; FENG; XU-NING; (Beijing, CN) ; LU;
LAN-GUANG; (Beijing, CN) ; LI; JIAN-QIU;
(Beijing, CN) ; OUYANG; MING-GAO; (Beijing,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tsinghua University |
Beijing |
|
CN |
|
|
Assignee: |
Tsinghua University
Beijing
CN
|
Family ID: |
1000004842080 |
Appl. No.: |
16/875932 |
Filed: |
May 15, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/CN2018/114516 |
Nov 8, 2018 |
|
|
|
16875932 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 2/166 20130101;
H01M 4/661 20130101; H01M 2004/021 20130101; H01M 4/382 20130101;
H01M 10/0525 20130101; H01M 4/1395 20130101 |
International
Class: |
H01M 4/1395 20060101
H01M004/1395; H01M 4/66 20060101 H01M004/66; H01M 4/38 20060101
H01M004/38; H01M 2/16 20060101 H01M002/16; H01M 10/0525 20060101
H01M010/0525 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 17, 2017 |
CN |
201711143955.2 |
Claims
1. A method for making a reference electrode, comprising: providing
a reference electrode substrate and a current collecting metal
sheet adhered with a tab binder; welding the reference electrode
substrate to a lower portion of the current collecting metal sheet;
melting lithium metal to liquid state, thereby obtaining a liquid
lithium; immersing a lower portion of the reference electrode
substrate welded with the current collecting metal sheet into the
liquid lithium and standing to coat a lithium metal layer on the
lower portion of the reference electrode substrate, thereby
obtaining a reference electrode welded with the current collecting
metal sheet; and taking out the reference electrode welded with the
current collecting metal sheet from the liquid lithium, cooling,
and warping a portion below the tab binder of the reference
electrode with a separator, thereby obtaining a reference electrode
wrapped with the separator.
2. The method of claim 1, wherein the reference electrode substrate
is a porous copper foam, a porous nickel foam, a copper mesh, or a
nickel mesh.
3. The method of claim 1, wherein before the welding, the reference
electrode substrate is washed and then dried.
4. The method of claim 1, wherein after the welding, an upper
portion of the reference electrode substrate is overlapped with the
lower portion of the current collecting metal sheet, and an area of
the current collecting metal sheet is smaller than an area of the
reference electrode substrate.
5. The method of claim 1, after the welding, further comprising:
vacuum drying the reference electrode substrate welded with the
current collecting metal sheet at about 60.degree. C. to about
90.degree. C. under the water-free and oxygen-free condition for
about 4 to about 7 hours, cooling, and then transferring into and
preserving in a water-free and oxygen-free environment.
6. The method of claim 1, wherein before the immersing, the liquid
lithium is heated to about 200.degree. C. to about 500.degree. C.
to remove an impurity on the surface of the liquid lithium under
the water-free and oxygen-free condition.
7. The method of claim 1, wherein the lower portion of the
reference electrode substrate is immersed into the liquid lithium
and rested for about 1 min to about 5 min to coat the lithium metal
layer on the lower portion of the reference electrode
substrate.
8. The method of claim 1, wherein after the wrapping, the separator
is wrapped tightly around the current collecting metal sheet and
the reference electrode substrate.
9. The method of claim 1, wherein a material of the current
collecting metal sheet is nickel or aluminum.
10. The method of claim 1, wherein a material of the separator is
porous polypropylene, porous polyethylene, porous polypropylene
coated with ceramic, porous polyethylene coated with ceramic, or
non-woven fabric.
11. The method of claim 1, wherein the reference electrode
substrate has a pore size of about 50 .mu.m to about 500 .mu.m and
a thickness of about 0.1 mm to about 1 mm.
12. The method of claim 1, wherein a thickness of the current
collecting metal sheet is about 0.1 mm to about 1 mm, and a length
of the current collecting metal sheet is about 10 mm to about 30
mm.
13. The method of claim 1, wherein the lithium metal layer has a
thickness of about 10 .mu.m to about 100 .mu.m.
14. A method for making a lithium ion battery having a reference
electrode, comprising: providing a reference electrode substrate
and a current collecting metal sheet adhered with a tab binder;
welding the reference electrode substrate to a lower portion of the
current collecting metal sheet; melting lithium metal to liquid
state, thereby obtaining a liquid lithium; immersing a lower
portion of the reference electrode substrate welded with the
current collecting metal sheet into the liquid lithium and standing
to coat a lithium metal layer on the lower portion of the reference
electrode substrate, thereby obtaining a reference electrode welded
with the current collecting metal sheet; taking out the reference
electrode welded with the current collecting metal sheet from the
liquid lithium, cooling, and warping a portion below the tab binder
of the reference electrode with a separator, thereby obtaining a
reference electrode wrapped with the separator; interposing the
reference electrode wrapped with the separator between a cell
separator and an anode plate of a cell of the lithium ion battery
and protrude an upper end of the reference electrode out from the
cell of the lithium ion battery under the water-free and
oxygen-free condition; and packaging the lithium ion battery
implanted with the reference electrode under the water-free and
oxygen-free condition, thereby obtaining the lithium ion battery
having the reference electrode.
15. The method of claim 14, wherein an area of the reference
electrode substrate is about 1% to about 10% of an area of an
electrode plate of the lithium ion battery.
16. The method of claim 14, wherein the upper end of the reference
electrode is protruded out from the cell of the lithium ion battery
for 1 mm to 2 mm.
17. The method of claim 14, wherein the lithium ion battery
implanted with the reference electrode is packaged by an aluminum
plastic film under the anhydrous and oxygen-free condition.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims all benefits accruing under 35
U.S.C. .sctn. 119 from China Patent Application No. 201711143955.2,
filed on Nov. 17, 2017 in the State Intellectual Property Office of
China, the content of which is hereby incorporated by reference.
This application is a continuation under 35 U.S.C. .sctn. 120 of
international patent application PCT/CN2018/114516 filed on Nov. 8,
2018, the content of which is also hereby incorporated by
reference.
FIELD
[0002] The present disclosure relates to methods for making
reference electrode and lithium ion battery having the same, and
belongs to the technical fields of measurement of an electrode
potential and manufacture of an electrode.
BACKGROUND
[0003] The electrode potential is one of the most important
parameters in electrochemistry and battery research. The
open-circuit potential is an electrode potential in a thermodynamic
equilibrium state. In practice, a voltage vs. SOC curve of a
battery obtained during a charge-discharge process at a low current
can be regarded as an open-circuit voltage curve. If there is a
current flowing through an electrode, the electrode would be
polarized and a potential of the electrode would be deviated due to
an occurrence of overpotential. The detailed information of a
reaction occurring inside the electrode can be obtained by
measuring a potential varying curve of the electrode. Taking a
lithium ion battery with a graphite anode as an example,
overcharging or low-temperature charging may result in a Li plating
at the graphite anode, characterized in that the anode potential is
below to the equilibrium potential for the lithium-plating.
Therefore, the Li plating side reaction can be detected by
measuring the electrode potential. However, the battery includes
two electrodes, and the polarization of the individual electrode
cannot be detected directly because the overpotential gauged is
composed of the polarized potential of positive and negative
electrodes, respectively. More specifically, one or more reference
electrodes are interposed between the cathode and the anode to
measure the voltage difference between the electrode and the
reference electrode. The reference electrode in the related art is
mainly made of electrochemical deposition, lithium foil, lithium
alloy, lithium-containing metal oxide, or lithium-containing
phosphate, and so on.
[0004] The research article Development of reliable lithium
micro-reference electrodes for long-term in-situ studies of
lithium-based battery systems, Journal of The Electrochemical
Society, 2004 (DOI: 10.6100/IR624713) discloses lithium reference
electrodes made by electrochemical deposition on two surfaces of a
micron sized copper wire positioned in the battery. The method can
minimize the blocking to the lithium ion flow. However, since the
reference electrode is too small, the amount of lithium loaded on
the reference electrode is small, and the deposition layer is
usually uneven. Consequently, a potential drift may occur after a
long time measurement, which makes it difficult to apply in
durability studies, and requires high input impedance of the
measuring instrument.
[0005] Another method involves inserting a lithium foil directly
into a battery. The lithium metal is connected to a current
collector by a physical pressing method. In the research article
Self-Discharge of LiMn.sub.2O.sub.4/C Li-Ion Cells in Their
Discharged State, J. Electrochem. Soc., Vol. 145, No. 1, 1998,
lithium is physically connected to, i.e., pressed against, a
current collector (for example, a copper mesh). In this method, the
copper mesh has a relatively large pore diameter which is at the
millimeter-scale. However, the connection reliability of the
lithium and the copper mesh cannot be ensured by this physical
connection method. A poor contact can lead to an extremely large
ohmic resistance of the reference electrode influencing the use
thereof.
[0006] In view of the above, the difficulties in the development of
the reference electrode can be contributed to the lithium amount in
the electrode. The size of the reference electrode should be as
small as possible to decrease the blocking effect on lithium ions
in the electrolyte. However, this will reduce the lithium amount in
the material, and thus weaken the signal. In addition, an electrode
material loss or a potential drift tends to occur because of the
micro-currents in the measurement.
SUMMARY
[0007] An object of the present disclosure is to provide a method
for making a reference electrode and a method for making a lithium
ion battery having the reference electrode.
[0008] The method for making the reference electrode in the present
disclosure includes: [0009] S11, washing and then drying a
reference electrode substrate; [0010] S12, welding the reference
electrode substrate to a lower portion of a current collecting
metal sheet, an upper portion of which is adhered with a tab
binder; [0011] S13, melting lithium metal to liquid state and
continuing heating to remove an impurity on a surface of the liquid
state lithium metal under a water-free and oxygen-free condition;
[0012] S14, immersing a lower portion of the reference electrode
substrate welded with the current collecting metal sheet into the
liquid lithium and standing to coat a lithium metal layer on the
lower portion of the reference electrode substrate; [0013] S15,
taking out a reference electrode welded with the current collecting
metal sheet from the liquid lithium, cooling, and warping a portion
below the tab binder of the reference electrode with a separator by
a winding method, thereby obtaining the reference electrode wrapped
with the separator.
[0014] The method for making the lithium ion battery having the
reference electrode in the present disclosure includes: [0015] S10,
making a reference electrode, which comprises: [0016] S11, washing
and then drying a reference electrode substrate; [0017] S12,
welding the reference electrode substrate to a lower portion of a
current collecting metal sheet, an upper portion of which is
adhered with a tab binder; [0018] S13, melting lithium metal to
liquid state and continuing heating to remove an impurity on a
surface of the liquid state lithium metal under a water-free and
oxygen-free condition; [0019] S14, immersing a lower portion of the
reference electrode substrate welded with the current collecting
metal sheet into the liquid lithium and standing to coat a lithium
metal layer on the lower portion of the reference electrode
substrate; [0020] S15, taking out a reference electrode welded with
the current collecting metal sheet from the liquid lithium,
cooling, and warping a portion below the tab binder of the
reference electrode with a separator by a winding method, thereby
obtaining the reference electrode wrapped with the separator;
[0021] S20, interposing the reference electrode between a separator
and an anode plate of a cell of the lithium ion battery and
protrude an upper end of the reference electrode out from the cell
of the lithium ion battery under the water-free and oxygen-free
condition; and [0022] S30, packaging the lithium ion battery
implanted with the reference electrode under the water-free and
oxygen-free condition, thereby obtaining the lithium ion battery
having the reference electrode.
[0023] Another method for making the lithium ion battery having the
reference electrode in the present disclosure includes: [0024]
S100, making a reference electrode, which comprises: [0025] S110,
providing a porous copper foam, a porous nickel foam, a copper
mesh, or a mesh as a reference electrode substrate; and washing the
reference electrode substrate with acetone or deionized water and
then drying for later use, wherein a material of the reference
electrode substrate has a pore size of about 50 .mu.m to about 500
.mu.m, a thickness of the reference electrode substrate is about
0.1 mm to about 1 mm, and an area of the reference electrode
substrate is about 1% to about 10% of an area of an electrode plate
of the lithium ion battery; [0026] S120, welding the reference
electrode substrate obtained from the step S110 to a lower portion
of a current collecting metal sheet of which an upper portion is
adhered with a tab binder, to allow an upper portion of the
reference electrode substrate to be overlapped with the lower
portion of the current collecting metal sheet, wherein an area of
the current collecting metal sheet is smaller than the area of the
reference electrode substrate; and vacuum drying at about
60.degree. C. to about 90.degree. C. under the water-free and
oxygen-free condition for about 4 to about 7 hours, cooing, and
then transferring into and preserving in a water-free and
oxygen-free environment, wherein the current collecting metal sheet
is configured for collecting an electric current, a material of the
current collecting metal sheet is nickel or aluminum, a thickness
of the current collecting metal sheet is about 0.1 mm to about 1
mm, and a length of the current collecting metal sheet is about 10
mm to about 30 mm; and [0027] S130, melting lithium metal to liquid
state and continuing heating to about 200.degree. C. to about
500.degree. C. to remove an impurity on a surface of the liquid
state lithium metal under the water-free and oxygen-free condition;
immersing the lower portion of the reference electrode substrate
whose upper portion is welded with the current collecting metal
sheet obtained from the step S120 into the liquid lithium and
standing for about 1 min to about 5 min to allow a lithium metal
layer having a thickness of about 10 .mu.m to about 100 .mu.m to
coat on the lower portion of the reference electrode substrate; and
taking out, cooling, and wrapping a portion below the tab binder
with a separator by a winding method to allow the separator to be
wrapped tightly and entirely around the current collecting metal
sheet and the reference electrode substrate, thereby obtaining the
reference electrode wrapped with the separator, wherein a material
of the separator is porous polypropylene, porous polyethylene,
porous polypropylene coated with ceramic, porous polyethylene
coated with ceramic, or non-woven fabric; [0028] S200, interposing
the reference electrode obtained from the step S100 between a
separator and an anode plate of a cell of the lithium ion battery
under the water-free and oxygen-free condition, and protruding an
upper end of the reference electrode out from the cell of the
lithium ion battery for about 1 mm to about 2 mm; [0029] S300,
packaging the lithium ion battery implanted with the reference
electrode with an aluminum plastic film under the water-free and
oxygen-free condition, thereby obtaining the lithium ion battery
having the reference electrode.
[0030] In the method for making the reference electrode and the
method for making the lithium ion battery having the reference
electrode according to the present disclosure, the lithium metal
can be formed on the surface of the substrate material, while the
porous property of the substrate material can be maintained, so
that small molecules in the liquid electrolyte can pass through the
pores, and the normal operation of the battery will not be
influenced. Moreover, the thickness of the lithium metal layer
formed on the substrate can be controlled by regulating parameters
in the making process to ensure that the porous property of the
substrate material can be retained while sufficient lithium can be
loaded on the substrate to meet measurement requirements.
Therefore, the reference electrode made by the method according to
the present disclosure can have sufficient micro-structures as well
as long service life. In addition, the manufacturing process is
simple and can meet the industrial production requirements, making
the industrial production and the application of the lithium-ion
battery with the reference electrode possible.
[0031] The methods provided in the present disclosure solve the
unstable problem of the measurement using the traditional reference
electrode and improve the service life of the reference electrode,
thereby achieving a long term multi-cycle potential measurement of
the individual electrode and increasing the accuracy of the
measuring result.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] To describe the technical solutions of the embodiments of
the present disclosure or the related technology more clearly, the
following briefly introduces the accompanying drawings for
describing the embodiments or the related technology. Obviously,
the accompanying drawings in the following description are only
embodiments of the present disclosure, and a person of ordinary
skill in the art may still derive other drawings from the
accompanying drawings of the present disclosure without creative
effort.
[0033] FIG. 1 is a flowchart of a method for making a reference
electrode according to an embodiment of the present disclosure.
[0034] FIG. 2 is a schematic structural view of a lithium ion
battery having the reference electrode according to an embodiment
of the present disclosure.
[0035] FIG. 3 is a front view of the reference electrode according
to an embodiment of the present disclosure.
[0036] FIG. 4 is a flowchart of another method for making the
reference electrode according to an embodiment of the present
disclosure.
[0037] FIG. 5 is a side view of the reference electrode shown in
the FIG. 3 according to an embodiment of the present
disclosure.
[0038] FIG. 6 is a flowchart of a method for making a lithium ion
battery having the reference electrode according to an embodiment
of the present disclosure.
[0039] FIG. 7 is a schematic view of the lithium ion battery
implanted with the reference electrode according to an embodiment
of the present disclosure.
[0040] FIG. 8 is a flowchart of another method for making the
lithium ion battery having the reference electrode according to an
embodiment of the present disclosure.
[0041] FIG. 9 is a flowchart of yet another method for making the
lithium ion battery having the reference electrode according to an
embodiment of the present disclosure.
[0042] FIG. 10 is a schematic diagram showing a measuring circuit
connecting the lithium ion battery having the reference electrode
according to an embodiment of the present disclosure.
[0043] FIG. 11 is a diagram showing results of rate performance
test for the lithium ion battery having the reference electrode
according to an embodiment of the present disclosure.
[0044] FIG. 12 is a diagram showing results of capacity test for
the lithium ion battery having the reference electrode according to
an embodiment of the present disclosure.
DESCRIPTION OF REFERENCE NUMERAL
[0045] lithium ion battery 1; [0046] reference electrode 2; [0047]
cathode 3; [0048] anode 4, [0049] tab binder 5, [0050] current
collecting metal sheet 6, [0051] reference electrode substrate 7,
[0052] welding spot 8, [0053] lithium metal layer 9, [0054] cathode
plate 10, [0055] separator 11 between the cathode plate and the
anode plate of the lithium ion battery
DETAILED DESCRIPTION
[0056] Referring to FIGS. 1 to 3, a method for making a reference
electrode is provided in the present disclosure. The method for
making the reference electrode includes:
[0057] S11, washing and then drying a reference electrode
substrate;
[0058] S12, welding the reference electrode substrate 7 to a lower
portion of a current collecting metal sheet 6, an upper portion of
which is adhered with a tab binder 5;
[0059] S13, melting lithium metal to liquid state and continuing
heating to remove an impurity on a surface of the liquid state
lithium metal (i.e. liquid lithium) under a water-free and
oxygen-free condition;
[0060] S14, immersing a lower portion of the reference electrode
substrate 7 welded with the current collecting metal sheet 6 into
the liquid lithium and standing to coat a lithium metal layer on
the lower portion of the reference electrode substrate 7, thereby
obtaining a reference electrode 2 welded with the current
collecting metal sheet 6;
[0061] S15, taking out the reference electrode 2 welded with the
current collecting metal sheet 6 from the liquid lithium, cooling,
and warping a portion below the tab binder 5 of the reference
electrode 2 with a separator by a winding method, thereby obtaining
a reference electrode 2 wrapped with the separator.
[0062] Referring to FIG. 4, in an embodiment, prior to the step
S11, S011, a porous copper foam, a porous nickel foam, a copper
mesh, or a nickel mesh is adopted as the reference electrode
substrate 7. In the step S11, the reference electrode substrate 7
is washed with acetone or deionized water and then dried for later
use. In this embodiment, the material of the reference electrode
substrate 7 can have a pore size of about 50 .mu.m to about 500
.mu.m, and a thickness of the reference electrode substrate 7 can
be about 0.1 mm to about 1 mm.
[0063] In an embodiment, in the step S12, the reference electrode
substrate 7 is welded to the lower portion of the current
collecting metal sheet 6 whose upper portion is adhered with the
tab binder 5, to allow an upper portion of the reference electrode
substrate 7 to be overlapped with the lower portion of the current
collecting metal sheet 6. An area of the current collecting metal
sheet 6 is smaller than an area of the reference electrode
substrate 7. After the step S12, S012, the reference electrode
substrate 7 welded with the current collecting metal sheet 6 is
vacuum dried at about 60.degree. C. to about 90.degree. C. under
the water-free and oxygen-free condition for about 4 to about 7
hours, cooled, and then transferred into and preserved in a
water-free and oxygen-free environment. The current collecting
metal sheet 6 is used for collecting an electric current. A
material of the current collecting metal sheet 6 is nickel or
aluminum. In this embodiment, a thickness of the current collecting
metal sheet 6 can be about 0.1 mm to about 1 mm. A length of the
current collecting metal sheet 6 can depend on a location of the
reference electrode 2 disposed with respect to the battery, and can
be about 10 mm to about 30 mm.
[0064] In an embodiment, in the step S13, the lithium metal is
melted into the liquid state and is continuously heated to about
200.degree. C. to about 500.degree. C. to remove the impurity on
the surface of the liquid state lithium metal under the water-free
and oxygen-free condition.
[0065] Referring to FIG. 5, in an embodiment, in the step S14, the
lower portion of the reference electrode substrate 7 whose upper
portion is welded with the current collecting metal sheet 6 is
immersed into the liquid lithium and rested for about 1 minute
(min) to about 5 min to coat the lithium metal layer 9 on the lower
portion of the reference electrode substrate 7. In this embodiment,
the portion without any welding spot 8 of the substrate can be
entirely immersed into the liquid lithium, and the lower portion of
the reference electrode substrate 7 can be fully wetted with the
lithium metal to allow the lithium metal layer 9 to be formed on
the lower portion of the reference electrode substrate 7. The
lithium metal layer 9 can have a thickness of about 10 .mu.m to
about 100 .mu.m.
[0066] In an embodiment, in the step S15, the reference electrode 2
welded with the current collecting metal sheet 6 is taken out from
the liquid lithium and cooled. The portion below the tab binder 5
of the reference electrode 2 is wrapped with the separator by the
winding method. The separator can be wrapped tightly and entirely
around the current collecting metal sheet 6 and the reference
electrode substrate 7, thereby obtaining the reference electrode 2
wrapped with the separator. A material of the separator is porous
polypropylene, porous polyethylene, porous polypropylene coated
with ceramic, porous polyethylene coated with ceramic, or non-woven
fabric.
[0067] Referring to FIGS. 6 and 7, a method for making a lithium
ion battery having a reference electrode is provided in the present
disclosure. The method for making the lithium ion battery having
the reference electrode includes making two parts: a reference
electrode and a lithium ion battery. The method includes:
[0068] S10, making a reference electrode 2, which includes:
[0069] S11, washing and then drying a reference electrode substrate
7;
[0070] S12, welding the reference electrode substrate 7 to a lower
portion of a current collecting metal sheet 6, an upper portion of
which is adhered with a tab binder 5;
[0071] S13, melting a lithium metal to liquid state and continuing
heating to remove an impurity on a surface of the liquid state
lithium metal (i.e. liquid lithium) under a water-free and
oxygen-free condition;
[0072] S14, immersing a lower portion of the reference electrode
substrate 7 welded with the current collecting metal sheet 6 into
the liquid lithium and standing to coat a lithium metal layer on
the lower portion of the reference electrode substrate 7, thereby
obtaining a reference electrode 2 welded with the current
collecting metal sheet 6; and
[0073] S15, taking out the reference electrode 2 welded with the
current collecting metal sheet 6 from the liquid lithium, cooling,
and warping a portion below the tab binder 5 of the reference
electrode 2 with a separator by a winding method, thereby obtaining
the reference electrode 2 wrapped with the separator;
[0074] The method further includes making the lithium ion battery 1
having the reference electrode 2, which includes:
[0075] S20, interposing the reference electrode 2 between a
separator 11 and an anode plate of a cell of the lithium ion
battery 1 and protruding an upper end of the reference electrode 2
out from the cell of the lithium ion battery 1 under the water-free
and oxygen-free condition; and
[0076] S30, packaging the lithium ion battery 1 implanted with the
reference electrode 2 under the water-free and oxygen-free
condition, thereby obtaining the lithium ion battery 1 having the
reference electrode 2.
[0077] Referring to FIG. 8, in an embodiment, prior to the step
S11, S011, a porous copper foam, a porous nickel foam, a copper
mesh, or a nickel mesh is adopted as the reference electrode
substrate 7. An area of the reference electrode substrate 7 is
about 1% to about 10% of an area of an electrode plate of the
lithium ion battery 1. In the step S11, the reference electrode
substrate 7 is washed with acetone or deionized water and then
dried for later use. In this embodiment, the material of the
reference electrode substrate 7 can have a pore size of about 50
.mu.m to about 500 .mu.m, and a thickness of the reference
electrode substrate 7 can be about 0.1 mm to about 1 mm.
[0078] In an embodiment, in the step S12, the reference electrode
substrate 7 is welded to the lower portion of the current
collecting metal sheet 6 whose upper portion is adhered with the
tab binder 5, to allow an upper portion of the reference electrode
substrate 7 to be overlapped with the lower portion of the current
collecting metal sheet 6. An area of the current collecting metal
sheet 6 is smaller than an area of the reference electrode
substrate 7. After the step S12, S012, the reference electrode
substrate 7 welded with the current collecting metal sheet 6 is
vacuum dried at about 60.degree. C. to about 90.degree. C. under
the water-free and oxygen-free condition for about 4 to about 7
hours, cooled, and then transferred into and preserved in a
water-free and oxygen-free environment. The current collecting
metal sheet 6 is used for collecting an electric current. A
material of the current collecting metal sheet 6 is nickel or
aluminum. In this embodiment, a thickness of the current collecting
metal sheet 6 can be about 0.1 mm to about 1 mm. A length of the
current collecting metal sheet 6 can depend on a location of the
reference electrode 2 disposed with respect to the battery, and can
be about 10 mm to about 30 mm.
[0079] In an embodiment, in the step S13, the lithium metal is
melted into the liquid state and is continuously heated to about
200.degree. C. to about 500.degree. C. to remove the impurity on
the surface of the liquid state lithium metal under the water-free
and oxygen-free condition.
[0080] In an embodiment, in the step S14, the lower portion of the
reference electrode substrate 7 whose upper portion is welded with
the current collecting metal sheet 6 is immersed into the liquid
lithium and rested for 1 min to 5 min to coat the lithium metal
layer 9 on the lower portion of the reference electrode substrate
7. In this embodiment, the portion without any welding spot 8 of
the substrate can be entirely immersed into the liquid lithium, and
the lower portion of the reference electrode substrate 7 can be
fully wetted with the lithium metal to allow the lithium metal
layer 9 to be formed on the lower portion of the reference
electrode substrate 7. The lithium metal layer 9 can have a
thickness of about 10 .mu.m to about 100 .mu.m.
[0081] In an embodiment, in the step S15, the reference electrode 2
welded with the current collecting metal sheet 6 is taken out from
the liquid lithium and cooled. The portion below the tab binder 5
of the reference electrode 2 is wrapped with the separator by the
winding method. The separator can be wrapped tightly and entirely
around the current collecting metal sheet 6 and the reference
electrode substrate 7, thereby obtaining the reference electrode 2
wrapped with the separator. A material of the separator is porous
polypropylene, porous polyethylene, porous polypropylene coated
with ceramic, porous polyethylene coated with ceramic, or non-woven
fabric.
[0082] In an embodiment, in the step 20, the reference electrode 2
is interposed between the separator 11 and the anode plate of the
cell of the lithium ion battery 1. The upper end of the reference
electrode 2 is protruded out from the cell of the lithium ion
battery 1 for 1 mm to 2 mm under the water-free and oxygen-free
condition.
[0083] In an embodiment, in the step S30, the lithium ion battery 1
implanted with the reference electrode 2 is packaged with an
aluminum plastic film under the water-free and oxygen-free
condition, thereby obtaining the lithium ion battery 1 having the
reference electrode 2.
[0084] Referring to FIG. 9, a method for making a lithium ion
battery having a reference electrode is provided in the present
disclosure. The method including the following steps:
[0085] S100, a reference electrode 2 is made as follows:
[0086] S110, a porous copper foam, a porous nickel foam, a copper
mesh, or a nickel mesh is adopted as the reference electrode
substrate 7. The reference electrode substrate 7 is washed with
acetone or deionized water and then dried for later use. The
material of the reference electrode substrate 7 has a pore size of
about 50 .mu.m to about 500 .mu.m. A thickness of the reference
electrode substrate 7 is about 0.1 mm to about 1 mm. An area of the
reference electrode substrate 7 is about 1% to about 10% of an area
of an electrode plate of the lithium ion battery 1.
[0087] S120, the reference electrode substrate 7 obtained from the
step S110 is welded to a lower portion of a current collecting
metal sheet 6, an upper portion of which is adhered with a tab
binder 5, to allow an upper portion of the reference electrode
substrate 7 to be overlapped with the lower portion of the current
collecting metal sheet 6, vacuum dried at about 60.degree. C. to
about 90.degree. C. under a water-free and oxygen-free condition
for about 4 to about 7 hours, cooled, and then transferred into and
preserved in a water-free and oxygen-free environment. The current
collecting metal sheet 6 is used for collecting an electric
current. A material of the current collecting metal sheet 6 is
nickel or aluminum. A thickness of the current collecting metal
sheet 6 is about 0.1 mm to about 1 mm. A length of the current
collecting metal sheet 6 depends on a location of the reference
electrode 2 disposed with respect to the battery and can be about
10 mm to about 30 mm. The tab binder 5 disposed on the upper
portion of the current collecting metal sheet 6 is configured to
fix the reference electrode 2 relative to the cell of the lithium
ion battery 1 when the reference electrode 2 is inserted into the
cell, as shown in FIGS. 3 and 5.
[0088] S130, lithium metal is melted to liquid state and continued
to heat to about 200.degree. C. to about 500.degree. C. to remove
an impurity on a surface of the liquid state lithium metal under
the water-free and oxygen-free condition. The lower portion of the
reference electrode substrate 7 whose upper portion is welded with
the current collecting metal sheet 6 obtained from the step S120 is
immersed into the liquid lithium for about 1 min to about 5 min.
The portion without any welding spot 8 of the substrate should be
entirely immersed into the liquid lithium. The lower portion of the
reference electrode substrate 7 is fully wetted by the lithium
metal, so as to allow a lithium metal layer 9 having a thickness of
about 10 .mu.m to about 100 .mu.m to be formed on the lower portion
of the reference electrode substrate 7. The electrode is taken out,
cooled, and a portion below the tab binder 5 is wrapped with a
separator by a winding method to allow the separator to be wrapped
tightly and entirely around the current collecting metal sheet 6
and the reference electrode substrate 7, thereby obtaining a
reference electrode 2 wrapped with the separator. A material of the
separator is porous polypropylene, porous polyethylene, porous
polypropylene coated with ceramic, porous polyethylene coated with
ceramic, or non-woven fabric. The separator can prevent the
reference electrode 2 from directly contacting with a cathode 3 and
an anode 4 of the lithium ion battery 1 and can allow lithium ions
to pass therethrough.
[0089] S200, the reference electrode 2 obtained from the step S100
is interposed between a separator 11 and an anode plate of a cell
of the lithium ion battery 1 under the water-free and oxygen-free
condition, as shown in FIG. 7. An upper end of the reference
electrode 2 is protruded out from the cell of the lithium ion
battery 1 for 1 mm to 2 mm. In order to show the location of the
reference electrode 2 disposed with respect to the cell of the
lithium ion battery 1, only the cathode plate 10 in the cell of the
lithium ion battery 1 is shown while the anode plate of the lithium
ion battery 1 is not shown.
[0090] S300, the lithium ion battery 1 implanted with the reference
electrode 2 is packed with an aluminum plastic film under the
water-free and oxygen-free condition, thereby obtaining the lithium
ion battery 1 having the reference electrode 2.
[0091] Examples of making the lithium ion battery 1 having the
reference electrode 2 according to the present disclosure are
described as below.
EXAMPLE 1
[0092] S100, a reference electrode 2 is made, and a specific
process is as below.
[0093] S110, a porous copper foam is provided as a reference
electrode substrate 7. A material of the reference electrode
substrate 7 has a pore size of 50 .mu.m. A thickness of the
reference electrode substrate 7 is 0.2 mm. An area of the reference
electrode substrate 7 is 2% of an area of an electrode plate of a
lithium ion battery 1. The reference electrode substrate 7 is a
rectangle sheet with a length of 10 mm and a width of 5 mm. The
reference electrode substrate 7 is washed with acetone or deionized
water and then dried for use.
[0094] S120, the reference electrode substrate 7 obtained from the
step S110 is welded to a lower portion of a current collecting
metal sheet 6 to allow an upper portion of the reference electrode
substrate 7 to be overlapped with the lower portion of the current
collecting metal sheet 6. An upper portion of the current
collecting metal sheet 6 is adhered with a tab binder 5. In this
embodiment, preferably, the current collecting nickel sheet 6
having a same width as the reference electrode substrate 7 and a
length of 20 mm, provided with the tab binder 5, is used for
welding. The reference electrode substrate 7 is vacuum dried at
80.degree. C. under the water-free and oxygen-free condition for 5
hours, cooled, and transferred into and preserved in a water-free
and oxygen-free environment.
[0095] S130, lithium metal is melted into liquid state and
continued to heat to 400.degree. C. to remove an impurity on a
surface of the liquid state lithium metal under the water-free and
oxygen-free condition. The lower portion of the reference electrode
substrate 7 whose upper portion is welded with the current
collecting metal sheet 6 obtained from the step S120 is immersed
into the liquid lithium for 3 min. The portion without any welding
spot 8 of the substrate is entirely immersed into the liquid
lithium. The lower portion of the reference electrode substrate 7
is fully wetted by the lithium metal, so as to allow a lithium
metal layer to coat on the lower portion of the reference electrode
substrate 7. The reference electrode 2 is taken out from the liquid
lithium, a surface of the reference electrode 2 is immediately
blown with hot air at 400.degree. C. to remove the lithium filled
in pores to expose the pores. In this embodiment, a thickness of
the lithium metal layer 9 grown is about 10 .mu.m. After being
cooled, a portion below the tab binder 5 of the reference electrode
2 is wrapped with a separator by a winding method. The current
collecting metal sheet 6 and the entire reference electrode
substrate 7 are wrapped tightly, thereby obtaining the reference
electrode 2 wrapped with the separator. A material of the separator
is porous polypropylene. The separator can prevent the reference
electrode 2 from directly contacting with a cathode 3 and an anode
4 of the lithium ion battery 1 and can allow lithium ions to pass
therethrough;
[0096] S200, the reference electrode 2 obtained from the step S100
is interposed between a separator 11 and an anode plate of a cell
of the lithium ion battery 1 under the water-free and oxygen-free
condition. In this embodiment, preferably, a soft package battery
is an object to be tested. The cell of the battery is placed into
the water-free and oxygen-free environment. The reference electrode
2 is interposed between a cathode plate 10 and an anode plate of
the cell, more specifically, located at an interface between a
separator 11 and the anode plate. The reference electrode 2 can be
interposed between any two plates except the outermost electrode
plate. The reference electrode 2 can be located at anywhere on the
plate, including but not limited to a center, a corner, and an edge
of the plate according to needs. In this embodiment, the reference
electrode 2 is interposed from a central area of an edge, while an
upper end of the reference electrode 2 is protruded out from the
cell of the lithium ion battery for 2 mm.
[0097] S300, the lithium ion battery 1 provided with the reference
electrode 2 obtained from the step S200 is packaged by an aluminum
plastic film under the water-free and oxygen-free condition,
thereby obtaining the lithium ion battery 1 having the reference
electrode 2.
EXAMPLE 2
[0098] S100, a reference electrode 2 is made, and a specific
process is as below.
[0099] S110, a porous nickel foam is provided as a reference
electrode substrate 7. A material of the reference electrode
substrate 7 has a pore size of 100 .mu.m. A thickness of the
reference electrode substrate 7 is 0.2 mm. An area of the reference
electrode substrate 7 is 5% of an area of an electrode plate of a
lithium ion battery 1. The reference electrode substrate 7 is sized
to a rectangle sheet with a length of 12 mm and a width of 7 mm.
The reference electrode substrate 7 is washed with acetone or
deionized water and then dried for use.
[0100] S120, the reference electrode substrate 7 obtained from the
step S110 is welded to a lower portion of a current collecting
metal sheet 6 to allow an upper portion of the reference electrode
substrate 7 to be overlapped with the lower portion of the current
collecting metal sheet 6. An upper portion of the current
collecting metal sheet 6 is adhered with a tab binder 5. In this
embodiment, preferably, the current collecting nickel sheet 6
having a same width as the reference electrode substrate 7 and a
length of 20 mm and provided with the tab binder 5 is used for
welding. The reference electrode substrate 7 is vacuum dried at
90.degree. C. under the water-free and oxygen-free condition for 5
hours, cooled, and transferred into and preserved in a water-free
and oxygen-free environment;
[0101] S130, lithium metal is melted into liquid state and
continued to heat to 400.degree. C. to remove an impurity on a
surface of the liquid state lithium metal under the water-free and
oxygen-free condition. The lower portion of the reference electrode
substrate 7 whose the upper portion is welded with the current
collecting metal sheet 6 obtained from the step S120 is immersed
into the liquid lithium for 4 min. The portion without any welding
spot 8 of the substrate is entirely immersed into the liquid
lithium. The lower portion of the reference electrode substrate 7
is fully wetted by the lithium metal, so as to allow a lithium
metal layer to coat on the lower portion of the reference electrode
substrate 7. The reference electrode 2 is taken out from the liquid
lithium, a surface of the reference electrode 2 is immediately
blown with hot air at 400.degree. C. to remove the lithium filled
in pores to expose the pores. In this embodiment, a thickness of
the lithium metal layer 9 grown is about 30 .mu.m. After being
cooled, a portion, below the tab binder 5 of the reference
electrode 2 is wrapped with a separator by a winding method. The
current collecting metal sheet 6 and the entire reference electrode
substrate 7 are wrapped tightly, thereby obtaining the reference
electrode 2 wrapped with the separator. A material of the separator
is porous polypropylene. The separator can prevent the reference
electrode 2 from directly contacting with a cathode 3 and an anode
4 of the lithium ion battery 1 and can allow lithium ions to pass
therethrough.
[0102] S200, the reference electrode 2 obtained from the step S100
is interposed between a separator 11 and an anode plate of a cell
of the lithium ion battery 1 under the water-free and oxygen-free
condition. In this embodiment, preferably, a soft package battery
is an object to be tested. The cell of the battery is placed into
the water-free and oxygen-free environment. The reference electrode
2 is interposed between a cathode plate 10 and an anode plate of
the cell, more specifically, disposed at an interface between a
separator 11 and the anode plate. The reference electrode 2 can be
interposed between any two plates except the outermost electrode
plate. The reference electrode 2 can be located at anywhere on the
plate, including but not limited to a center, a corner, and an edge
of the plate according to needs. In this embodiment, the reference
electrode 2 is interposed from a central area of an edge, while an
upper end of the reference electrode 2 is protruded out from the
cell of the lithium ion battery for 2 mm.
[0103] S300, the lithium ion battery 1 provided with the reference
electrode 2 obtained from the step S200 is packaged by an aluminum
plastic film under the water-free and oxygen-free condition,
thereby obtaining the lithium ion battery 1 having the reference
electrode 2.
EXAMPLE 3
[0104] S100, a reference electrode 2 is made, and a specific
process is as below.
[0105] S110, a porous copper mesh is provided as a reference
electrode substrate 7. A material of the reference electrode
substrate 7 has a pore size of 300 .mu.m. A thickness of the
reference electrode substrate 7 is 0.2 mm. An area of the reference
electrode substrate 7 is 2% of an area of an electrode plate of a
lithium ion battery 1. The reference electrode substrate 7 is a
rectangle sheet with a length of 20 mm and a width of 10 mm. The
reference electrode substrate 7 is washed with acetone or deionized
water and then dried for use.
[0106] S120, the reference electrode substrate 7 obtained from the
step S110 is welded to a lower portion of a current collecting
metal sheet 6 to allow an upper portion of the reference electrode
substrate 7 to be overlapped with the lower portion of the current
collecting metal sheet 6. An upper portion of the current
collecting metal sheet 6 is adhered with a tab binder 5. In this
embodiment, preferably, the current collecting nickel sheet 6
having a same width as the reference electrode substrate 7 and a
length of 20 mm and provided with the tab binder 5 is used for
welding. The reference electrode substrate 7 is vacuum dried at
80.degree. C. under the water-free and oxygen-free condition for 5
hours, cooled, and transferred into and preserved in a water-free
and oxygen-free environment;
[0107] S130, a lithium metal is melted into liquid state and
continued to heat to 400.degree. C. to remove an impurity on a
surface of the liquid state lithium metal under the water free and
oxygen-free condition. The lower portion of the reference electrode
substrate 7 whose upper portion is welded with the current
collecting metal sheet 6 obtained from the step S120 is immersed
into the liquid lithium for 3 min. The portion without any welding
spot 8 of the substrate is entirely immersed into the liquid
lithium. The lower portion of the reference electrode substrate 7
is fully wetted by the lithium metal, so as to allow a lithium
metal layer to coat on the lower portion of the reference electrode
substrate 7. The reference electrode 2 is taken out from the liquid
lithium, and a surface of the reference electrode 2 is immediately
blown with hot air at 400.degree. C. to remove the lithium filled
in pores to expose the pores. In this embodiment, a thickness of
the lithium metal layer 9 grown is about 100 .mu.m. After being
cooled, a portion below the tab binder 5 of the reference electrode
2 is wrapped with a separator by a winding method. The current
collecting metal sheet 6 and the entire reference electrode
substrate 7 are wrapped tightly, thereby obtaining the reference
electrode 2 wrapped with the separator. A material of the separator
is porous polypropylene. The separator can prevent the reference
electrode 2 from directly contacting with a cathode 3 and an anode
4 of the lithium ion battery 1 and can allow lithium ions to pass
therethrough.
[0108] S200, the reference electrode 2 obtained from the step S100
is interposed between a separator 11 and an anode plate of a cell
of the lithium ion battery 1 under the water-free and oxygen-free
condition. In this embodiment, preferably, a soft package battery
is an object to be tested. The cell of the battery is placed into
the water-free and oxygen-free environment. The reference electrode
2 is interposed between a cathode plate 10 and an anode plate of
the cell, more specifically, disposed at an interface between a
separator 11 and the anode plate. The reference electrode 2 can be
interposed between any two plates except the outermost electrode
plate. The reference electrode 2 can be located at anywhere on the
plate, including but not limited to a center, a corner, and an edge
according to needs. In this embodiment, the reference electrode 2
is interposed from a central area of an edge, while an upper end of
the reference electrode 2 is protruded out from the cell of the
lithium ion battery for 2 mm.
[0109] S300, the lithium ion battery 1 provided with the reference
electrode 2 obtained from the step S200 is packaged by an aluminum
plastic film under the water-free and oxygen-free condition,
thereby obtaining the lithium ion battery 1 having the reference
electrode 2.
EXAMPLE 4
[0110] S100, a reference electrode 2 is made, and a specific
process is as below.
[0111] S110, a porous nickel mesh is provided as a reference
electrode substrate 7. A material of the reference electrode
substrate 7 has a pore size of 500 .mu.m. A thickness of the
reference electrode substrate 7 is 0.2 mm. An area of the reference
electrode substrate 7 is 1% of an area of an electrode plate of a
lithium ion battery 1. The reference electrode substrate 7 is a
rectangle sheet with a length of 20 mm and a width of 8 mm. The
reference electrode substrate 7 is washed with acetone or deionized
water and then dried for use.
[0112] S120, the reference electrode substrate 7 obtained from the
step S110 is welded to a lower portion of a current collecting
metal sheet 6 to allow an upper portion of the reference electrode
substrate 7 to be overlapped with the lower portion of the current
collecting metal sheet 6. An upper portion of the current
collecting metal sheet 6 is adhered with a tab binder 5. In this
embodiment, preferably, a current collecting nickel sheet 6 having
a same width as the reference electrode substrate 7 and a length of
20 mm and provided with the tab binder 5 is used for welding. The
reference electrode substrate 7 is vacuum dried at 80.degree. C.
under the water-free and oxygen-free condition for 5 hours, cooled,
and transferred into and preserved in a water-free and oxygen-free
environment.
[0113] S130, lithium metal is melted into liquid state and
continued to heat to 400.degree. C. to remove an impurity on a
surface of the liquid state lithium metal under the water-free and
oxygen-free condition. The lower portion of the reference electrode
substrate 7 whose upper portion is welded with the current
collecting metal sheet 6 obtained from the step S120 is immersed
into the liquid lithium for 3 min. The portion without any welding
spot 8 of the substrate is entirely immersed into the liquid
lithium, and the lower portion of the reference electrode substrate
7 is fully wetted by the lithium metal, so as to allow a lithium
metal layer to coat on the lower portion of the reference electrode
substrate 7. A reference electrode 2 is taken out from the liquid
lithium and a surface of the reference electrode 2 is immediately
blown with hot air at 400.degree. C. to remove the lithium filled
in pores to expose the pores. In this embodiment, a thickness of
the lithium metal layer 9 grown is about 100 .mu.m. After being
cooled, a portion below the tab binder 5 of the reference electrode
2 is wrapped with a separator by a winding method. The current
collecting metal sheet 6 and the entire reference electrode
substrate 7 are wrapped tightly, thereby obtaining the reference
electrode 2 wrapped with the separator. A material of the separator
is porous polypropylene. The separator can prevent the reference
electrode 2 from directly contacting with a cathode 3 and an anode
4 of the lithium ion battery 1 and can allow lithium ions to pass
therethrough.
[0114] S200, the reference electrode 2 obtained from the step S100
is interposed between a separator 11 and an anode plate of a cell
of the lithium ion battery 1 under the water-free and oxygen-free
condition. In this embodiment, preferably, a soft package battery
is an object to be tested. The cell of the battery is placed into
the water-free and oxygen-free environment. The reference electrode
2 is interposed between a cathode plate 10 and an anode plate of
the cell, more specifically, disposed at an interface between a
separator 11 and the anode plate. The reference electrode 2 can be
interposed between any two plates except the outermost electrode
plate. The reference electrode 2 can be located at anywhere on the
plate, including but not limited to a center, a corner, and an edge
according to needs. In this embodiment, the reference electrode 2
is interposed from a central area of an edge, while an upper end of
the reference electrode 2 is protruded out from the cell of the
lithium ion battery for 2 mm.
[0115] S300, the lithium ion battery 1 provided with the reference
electrode 2 obtained from the step S200 is packaged by an aluminum
plastic film under the water-free and oxygen-free condition,
thereby obtaining the lithium ion battery 1 having the reference
electrode 2.
[0116] A charge-discharge test is performed by connecting the
cathode 3 and the anode 4 of the lithium ion battery 1 having the
reference electrode 2 to an instrument such as a charge-discharge
tester or other power supply. The performance of assembled lithium
ion battery 1 having the reference electrode 2 is measured by the
measuring instrument. As shown in FIG. 10 which is a schematic
measuring circuit diagram, a high input impedance voltage
synchronous acquisition equipment having three testing channels is
used, an external voltage U1 of the lithium ion battery 1 having
the reference electrode 2 is measured and acquired via the channel
1, an anode-reference voltage U2 is measured and acquired via the
channel 2, and a cathode-reference voltage U3 is measured and
acquired via the channel 3. Moreover, different types of
charge-discharge cycling tests with a higher cutoff voltage of 4.2
V and a lower cutoff voltage of 2.5 V are performed on the lithium
ion battery 1 having the reference electrode 2 via the channel 1
during which charge and discharge currents are recorded. Result
analyses for two types of charge-discharge cycling tests are
described as below.
[0117] FIG. 11 is a diagram showing results of a charge-discharge
rate performance test for the battery having the reference
electrode 2, in which a horizontal axis denotes a time during the
test and a vertical axis denotes a tested voltage. External voltage
is shown by the solid line. Voltage of the individual electrode,
which is the anode 4, with respect to the reference electrode 2 is
shown by the dotted line. During the test, the charge-discharge
current rate gradually increased from 0.5 C to 1.5 C. More
specifically, the battery is charged and discharged at 0.5 C in the
first charge-discharge cycle, charged and discharged at 1 C in the
second charge-discharge cycle, and charged and discharged at 1.5 C
in the third charge-discharge cycle, as is shown in the FIG. 11. It
can be found upon this test that the variations of the external
voltage in the three different charge-discharge cycles using
different charge-discharge rates are consistent, while the
variations of the voltage of the anode 4 tested with respect to the
reference electrode 2 clearly tend to increase with the increase of
the charge-discharge rate. Such feature that the voltage of the
anode 4 is changed with the change of the charge-discharge rate,
cannot be tested by only measuring the external voltage. By using
the reference electrode 2, this voltage variation for an individual
electrode can be directly and conveniently tested, which
demonstrates the superiority of the testing using the reference
electrode 2.
[0118] FIG. 12 is a diagram showing results of a capacity test for
the battery having the reference electrode 2, in which a horizontal
axis denotes a time during the test and a vertical axis denotes a
tested voltage. External voltage of the battery is shown by the
solid line. Voltage of the individual electrode, which is the anode
4, with respect to the reference electrode 2 of the battery is
shown by the dotted line. During the test, the charge-discharge
current rate is kept at 1 C. It can be seen that the voltage of the
anode 4 as the individual electrode with respect to the reference
electrode is stable in each charge-discharge cycle, while the
voltage of the whole battery is also stable in each
charge-discharge cycle, suggesting that the reference electrode 2
has a satisfactory service time and does not interfere with the
normal operation of the battery.
* * * * *