CN114284564A - Soft package battery with constant potential reference electrode and preparation method thereof - Google Patents
Soft package battery with constant potential reference electrode and preparation method thereof Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title claims abstract description 24
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 59
- 238000000034 method Methods 0.000 claims abstract description 24
- 238000007599 discharging Methods 0.000 claims abstract description 22
- 230000008569 process Effects 0.000 claims abstract description 13
- 238000013461 design Methods 0.000 claims abstract description 9
- 230000007246 mechanism Effects 0.000 claims abstract description 8
- 238000004806 packaging method and process Methods 0.000 claims abstract description 8
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 38
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 38
- 229910052782 aluminium Inorganic materials 0.000 claims description 26
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 26
- 229910052759 nickel Inorganic materials 0.000 claims description 19
- 238000012360 testing method Methods 0.000 claims description 18
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 17
- 239000011248 coating agent Substances 0.000 claims description 17
- 238000000576 coating method Methods 0.000 claims description 17
- 229910001416 lithium ion Inorganic materials 0.000 claims description 17
- 239000011889 copper foil Substances 0.000 claims description 16
- 239000011267 electrode slurry Substances 0.000 claims description 16
- 239000011888 foil Substances 0.000 claims description 14
- 238000004080 punching Methods 0.000 claims description 12
- 238000005096 rolling process Methods 0.000 claims description 12
- 238000003466 welding Methods 0.000 claims description 12
- 238000012544 monitoring process Methods 0.000 claims description 11
- 239000002985 plastic film Substances 0.000 claims description 7
- 229920006255 plastic film Polymers 0.000 claims description 7
- 239000003792 electrolyte Substances 0.000 claims description 6
- 239000007788 liquid Substances 0.000 claims description 6
- 238000007789 sealing Methods 0.000 claims description 6
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- 238000004458 analytical method Methods 0.000 abstract description 2
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- 238000007747 plating Methods 0.000 description 3
- PFYQFCKUASLJLL-UHFFFAOYSA-N [Co].[Ni].[Li] Chemical compound [Co].[Ni].[Li] PFYQFCKUASLJLL-UHFFFAOYSA-N 0.000 description 2
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- 230000002687 intercalation Effects 0.000 description 2
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- 238000004519 manufacturing process Methods 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 238000010301 surface-oxidation reaction Methods 0.000 description 2
- 239000010405 anode material Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention discloses a preparation method of a soft package battery with a constant potential reference electrode, which comprises the steps of firstly overlapping a positive electrode plate, a diaphragm and a negative electrode plate in a Z shape to prepare a galvanic pile, then covering the diaphragm on the surface of the negative electrode plate at the outermost side of the galvanic pile, placing a lithium metal sheet as the reference electrode, connecting electrode lugs and packaging, and then carrying out electrochemical treatment on an oxide layer on the surface of the reference electrode by utilizing a discharging process to obtain the soft package battery with the constant potential reference electrode. The preparation method is simple, the application range is wide, the reliability, the stability and the continuity of the reference electrode in an electrochemical test are effectively improved, the independent analysis of the lithium potential and the impedance change of the positive electrode and the negative electrode in different states can be realized, and important basis can be provided for optimizing the battery design, analyzing the electrode interface stability, the cycle attenuation mechanism and the like.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a soft package battery with a constant potential reference electrode and a preparation method thereof.
Background
In the process of developing the lithium ion battery, the introduction of the reference electrode is an important auxiliary design method, the reference electrode is added in the battery, the anode and the cathode of the battery can be separately researched, the potential and impedance changes of the anode and the cathode in different states can be independently analyzed, and important basis is provided for optimizing the battery design, analyzing the electrode interface stability, the cycle attenuation mechanism and the like.
The lithium metal is the most commonly used reference electrode in lithium ion batteries, and the addition modes mainly include two modes: (1) adding copper wires, platinum wires, gold wires and the like into the battery cell, and carrying out in-situ lithium plating before use; (2) lithium metal wires, lithium metal bands, lithium metal sheets and the like are directly connected into the battery. However, the accuracy of the potential of the reference electrode itself is rarely reported, and the existence of the error of the reference electrode of the lithium ion battery is confirmed in an article (Journal of Power Sources 481(2021)228933) published and reported abroad, a copper wire with the diameter of 200 μm is used as the reference electrode, the potential change of the negative electrode in the charging process with different multiplying powers is monitored, and the surface topography of the negative electrode piece after full-state disassembly is combined, so that the potential error exceeding 67mV exists in the charging process of the battery at 0.6C, and the potential error is reduced along with the reduction of the size of the reference electrode, but cannot be eliminated. Therefore, an accurate and reliable reference electrode with a constant potential needs to be introduced into the battery, so that the potential of the reference electrode is always kept constant, and accurate positive and negative electrode potential and impedance information can be obtained.
The Chinese patent application (publication number: CN107293778A) discloses a three-electrode battery and a preparation method thereof, wherein the diameter of a reference electrode is 5-20 mu m, one end of the reference electrode is a bare copper wire, the bare copper wire is arranged between a positive electrode plate and a negative electrode plate and is separated by a diaphragm, the other end of the reference electrode is an enameled wire, the enameled wire is led out from the outside of the battery and is connected with a nickel electrode lug, and the surface of the copper wire needs to be plated with lithium before testing the alternating current impedance. The diameter of the reference electrode is considered to be smaller than the thickness of the diaphragm and the particle sizes of the anode and cathode materials, so that the transmission of lithium ions between the anode and the cathode is not influenced, and the detection accuracy can be obviously improved. However, the invention does not consider that the size of the reference electrode is increased by the lithium plating layer, so that the current disturbs the reference potential in the charging and discharging processes, and the accuracy of the reference electrode potential is not specifically described. In addition, the durability of the lithium layer on the surface of the copper wire is poor, and the lithium is required to be plated in advance before each monitoring, so that the operation procedures are increased.
The Chinese patent application (publication number: CN106785068B) discloses a three-electrode soft package battery and a preparation method thereof, wherein a lithium metal sheet is attached to a copper mesh as a reference electrode and is arranged between a positive electrode plate and a negative electrode plate and is separated by a diaphragm, and blank areas which are not coated with slurry are reserved on the positive electrode plate and the negative electrode plate at the corresponding positions of the reference electrode in order to avoid the interference of the reference electrode. However, the invention is only suitable for small-capacity soft package batteries, and the influence of the surface oxidation layer of the lithium metal sheet on the accuracy of the reference potential is not mentioned.
Disclosure of Invention
The invention aims to overcome the defects and provides a preparation method of a soft package battery with a constant potential reference electrode. The preparation method is simple, the application range is wide, the reliability, the stability and the continuity of the reference electrode in an electrochemical test are effectively improved, the independent analysis of the lithium potential and the impedance change of the positive electrode and the negative electrode in different states can be realized, and important basis can be provided for optimizing the battery design, analyzing the electrode interface stability, the cycle attenuation mechanism and the like.
In order to achieve the above purpose, the invention provides the following technical scheme:
a preparation method of a soft package battery with a constant potential reference electrode comprises the following steps:
s1, coating positive electrode slurry on both sides of the aluminum foil, rolling and punching to obtain a positive electrode plate; coating negative electrode slurry on two sides of a copper foil, and rolling and punching to obtain a negative electrode plate;
s2, overlapping the positive pole piece, the diaphragm and the negative pole piece in a Z shape to obtain the galvanic pile, wherein the number of the negative pole pieces is 1 more than that of the positive pole pieces;
s3, after the surface of the cathode pole piece at the outermost side of the pile is covered with a diaphragm, placing a lithium metal sheet connected with a nickel pole lug, then coating the lithium metal sheet with the diaphragm, and carrying out insulation treatment and fixation on the lithium metal sheet; the lithium metal sheet is used as a reference electrode, and the nickel electrode lug connected with the lithium metal sheet is used as a reference electrode lug;
s4, welding an aluminum foil in the positive pole piece of the pile with an aluminum tab, and welding a copper foil in the negative pole piece of the pile with a nickel tab; the aluminum lug and the nickel lug welded with the copper foil are respectively a positive lug and a negative lug;
s5, sequentially packaging the galvanic pile containing the reference electrode, injecting liquid, vacuumizing and sealing to obtain a soft package three-electrode battery;
s6, connecting a reference electrode tab and a negative electrode tab of the soft-package three-electrode battery to charging and discharging equipment, and performing electrochemical treatment on an oxide layer on the surface of the reference electrode through discharging to obtain the soft-package battery with the constant-potential reference electrode.
Further, in the step S3, the width of the lithium metal sheet is 0.1 to 0.8 times of the negative electrode plate, and the length of the lithium metal sheet is 0.1 to 0.8 times of the negative electrode plate.
Further, in the step S3, the thickness of the lithium metal sheet is 10 to 100 μm.
Further, in step S3, the lithium metal piece placement region is located in a region corresponding to the negative electrode tab.
Further, in step S4, an aluminum foil in the positive electrode plate of the stack is welded to the aluminum tab by ultrasonic welding, and a copper foil in the negative electrode plate of the stack is welded to the nickel tab.
Further, in the step S5, an aluminum-plastic film is adopted to package the galvanic pile containing the reference electrode, and the using amount of the electrolyte during liquid injection is 4-8 g/Ah.
Further, in step S6, a negative electrode tab of the soft-package three-electrode battery is connected to the positive electrode of the charge and discharge device, and a reference electrode tab of the soft-package three-electrode battery is connected to the negative electrode of the charge and discharge device.
Further, in step S6, the pouch three-electrode battery is discharged at a constant current.
Further, in the step S6, the constant current I is used for discharging the soft pack three-electrode battery r5 to 200 muA, discharge time trIs 2-5 h.
A soft package battery with a constant potential reference electrode is obtained by adopting the preparation method of the soft package battery with the constant potential reference electrode, is used for testing the electrochemical performance of a lithium ion battery, and researches on the design rationality, the power matching performance and the cycle attenuation mechanism of the lithium ion battery are carried out by monitoring the potential changes of a positive electrode and the reference electrode and the potential changes of a negative electrode and the reference electrode in the testing process; or the research on the interface stability of the lithium ion battery is carried out by monitoring the impedance changes of the anode and the reference electrode and the impedance changes of the cathode and the reference electrode under different states.
Compared with the prior art, the invention has the following beneficial effects:
(1) according to the preparation method of the soft package battery with the constant potential reference electrode, the lithium metal sheet is used as the reference electrode, the surface oxidation layer of the lithium metal sheet used as the reference electrode is subjected to electrochemical treatment in the discharging process to remove impurities and oxides, the reference potential is ensured to be constant all the time, the accuracy and the durability of the reference electrode in an electrochemical test are effectively improved, and the reliability and the stability of the soft package three-electrode battery in application are further improved;
(2) in the preparation method of the soft package battery with the constant potential reference electrode, the lithium metal sheet is arranged on the outermost side of the galvanic pile, so that the interference of current change to the reference potential in the charging and discharging process can be avoided, and the reference potential is always kept constant;
(3) the preparation method of the soft package battery with the constant potential reference electrode is simple, the application range is wide, the soft package battery is applied to the test of the electrochemical performance of the lithium ion battery, the lithium potential and impedance changes of the positive electrode and the negative electrode in different states can be analyzed independently, and important basis can be provided for optimizing the battery design, analyzing the stability of an electrode interface, a cycle attenuation mechanism and the like.
Drawings
FIG. 1 is a schematic diagram of the stack overlap of the present invention;
FIG. 2 is a schematic structural diagram of a pouch cell with a constant potential reference electrode according to the present invention;
FIG. 3 is a graph showing the results of monitoring the voltage of the battery in example 1;
FIG. 4 is a graph showing the results of monitoring the cell voltage in comparative example 1;
fig. 5 is a graph showing the results of monitoring the cell voltage in comparative example 2.
Detailed Description
The features and advantages of the present invention will become more apparent and appreciated from the following detailed description of the invention.
The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.
The invention relates to a preparation method of a soft package battery with a constant potential reference electrode, which comprises the following steps:
firstly, coating positive electrode slurry on two sides of an aluminum foil, rolling and punching to obtain a positive electrode plate; coating negative electrode slurry on two sides of a copper foil, and rolling and punching to obtain a negative electrode plate;
secondly, overlapping the positive pole piece, the diaphragm and the negative pole piece in a Z shape to prepare the electric pile, wherein the number of the negative pole pieces is 1 more than that of the positive pole pieces;
thirdly, after a diaphragm is covered on the surface of the negative pole piece at the outermost side of the pile, placing a lithium metal sheet which is cut in advance and connected with a nickel lug as a reference electrode, then coating the lithium metal sheet with the diaphragm, and carrying out insulation treatment and fixation on the lithium metal sheet;
fourthly, connecting the positive aluminum foil and the aluminum tab of the galvanic pile and connecting the negative copper foil and the nickel tab of the galvanic pile by ultrasonic welding, then packaging the galvanic pile with the reference electrode by an aluminum plastic film, injecting liquid, vacuumizing and sealing to obtain a soft package three-electrode battery;
fifthly, connecting a reference electrode tab and a negative electrode tab of the soft package three-electrode battery into the charging and discharging equipment, connecting the battery negative electrode tab with the positive electrode of the charging and discharging equipment, connecting the battery reference electrode tab with the negative electrode of the charging and discharging equipment, and carrying out constant current IrDischarging it for a discharge time trAnd removing oxides and impurities on the surface of the reference electrode to prepare the soft package battery with the constant potential reference electrode.
Furthermore, in the preparation method of the soft package battery with the constant potential reference electrode, in the third step, the width of the lithium metal sheet is 0.1-0.8 times of that of the negative electrode sheet, and the length of the lithium metal sheet is 0.1-0.8 times of that of the negative electrode sheet.
Furthermore, in the preparation method of the soft package battery with the constant potential reference electrode, in the third step, the thickness of the lithium metal sheet is 10-100 μm;
furthermore, in the preparation method of the soft package battery with the constant potential reference electrode, in the third step, the placement area of the lithium metal sheet needs to be located in the corresponding area of the negative electrode sheet; namely, the projection of the lithium metal sheet on the plane of the negative pole piece is positioned in the area of the negative pole piece;
further, in the preparation method of the soft package battery with the constant potential reference electrode, in the fourth step, the using amount of the electrolyte during liquid injection is 4-8 g/Ah;
further, in the preparation method of the flexible package battery with the constant potential reference electrode, in the fifth step, IrIs selected to be 5-200 muA, trThe selection time is 2-5 h.
The soft package battery with the constant potential reference electrode is used for testing the electrochemical performance of the lithium ion battery, and the potential changes of the anode and the reference and the cathode and the reference are monitored in the testing process, so that the soft package battery with the constant potential reference electrode can be used for researching the design rationality, the power matching property and the cycle attenuation mechanism of the lithium ion battery; and monitoring impedance changes of the anode and the reference and the cathode and the reference, and can be used for researching the interface stability of the lithium ion battery.
Example 1
A soft package battery with a constant potential reference electrode is prepared by the following steps:
(1) preparing positive electrode slurry by taking a nickel-cobalt lithium aluminate material as a positive electrode, coating the two surfaces of the positive electrode slurry on a 15-micron aluminum foil, and rolling and punching to obtain a positive electrode plate; preparing negative electrode slurry by taking graphite as a negative electrode, coating two surfaces of the negative electrode slurry on copper foil with the thickness of 8 mu m, and rolling and punching to prepare a negative electrode piece, wherein the size of the negative electrode piece is 70mm multiplied by 156 mm;
(2) overlapping the positive pole piece, the diaphragm and the negative pole piece in a Z shape to obtain a galvanic pile, wherein the number of the negative pole pieces is 8, the number of the positive pole pieces is 7, and the schematic diagram of the galvanic pile is shown in figure 1;
(3) cutting a lithium metal sheet with the thickness of 50 mu m into the size of 30mm multiplied by 50mm, and crimping a nickel tab;
(4) after the surface of the cathode pole piece at the outermost side of the pile is coated with a diaphragm, placing a cut lithium metal sheet as a reference electrode in the central area corresponding to the cathode pole piece, coating the lithium metal sheet with the diaphragm, and performing insulation and fixation;
(5) connecting a positive aluminum foil and an aluminum tab of a stack and a negative copper foil and a nickel tab of the stack by ultrasonic welding, then packaging the stack with a reference electrode by an aluminum-plastic film, injecting 20g of electrolyte, vacuumizing and sealing to obtain a soft-package three-electrode battery, wherein the structural schematic diagram of the battery is shown in figure 2, wherein 1 is a negative tab, 2 is a positive tab, 3 is the stack, 4 is the aluminum-plastic film, 5 is the reference electrode tab and 6 is a lithium metal sheet;
(6) and (3) connecting a reference electrode tab and a negative electrode tab of the soft-package three-electrode battery into a charging and discharging device, connecting the battery negative electrode tab to the positive electrode of the charging and discharging device, connecting the battery reference electrode tab to the negative electrode of the charging and discharging device, and discharging the battery reference electrode tab at a constant current of 10 mu A for 5h to prepare the soft-package battery with the constant potential reference electrode.
The prepared soft package battery with the constant potential reference electrode is subjected to 0.1C charging and discharging test, potential values of the anode and the reference and potential values of the cathode and the reference are monitored in the test process, and the test result is shown in figure 3. It can be seen that no abnormal and noise point appears in the potential value between the anode and the reference and the potential value between the cathode and the reference, the cathode curve presents a typical graphite three-order lithium intercalation platform, the lithium intercalation platform voltages are 0.20V, 0.12V and 0.08V respectively, and are consistent with the characteristic value of graphite, and the accuracy of the reference electrode is verified.
Comparative example 1
In this comparative example, a pouch cell was prepared using a lithium metal sheet directly as a reference electrode, and the preparation steps were as follows:
(1) preparing anode slurry by taking a lithium cobaltate material as an anode, coating the anode slurry on an aluminum foil with the thickness of 15 mu m on two sides, and rolling and punching to obtain an anode piece; preparing negative electrode slurry by taking graphite as a negative electrode, coating two surfaces of the negative electrode slurry on copper foil with the thickness of 8 mu m, and rolling and punching to prepare a negative electrode piece, wherein the size of the negative electrode piece is 70mm multiplied by 156 mm;
(2) overlapping the positive plates, the diaphragms and the negative plates in a Z shape to obtain the galvanic pile, wherein the number of the negative plates is 8, and the number of the positive plates is 7;
(3) cutting a lithium metal sheet with the thickness of 50 mu m into the size of 30mm multiplied by 50mm, pressing a nickel tab to prepare a reference electrode A, and preparing a reference electrode B by adopting the same method;
(4) sequentially placing a reference electrode A and a reference electrode B in a region corresponding to the cathode plate on the outer side of the pile from top to bottom, and coating, insulating and fixing the reference electrode A and the reference electrode B by using a diaphragm;
(5) and (3) connecting the anode aluminum foil and the aluminum tab of the stack and the cathode copper foil and the nickel tab of the stack by ultrasonic welding, then packaging the stack with the reference electrode by adopting an aluminum-plastic film, injecting 20g of electrolyte, vacuumizing and sealing to obtain the soft package battery with the lithium metal sheet as the reference electrode.
The prepared soft package battery with the lithium metal sheet as the reference electrode is subjected to 0.1C charge and discharge test, the potential values of the positive electrode and the reference electrode A, the negative electrode and the reference electrode A, the positive electrode and the reference electrode B and the negative electrode and the reference electrode B are monitored in the test process, and the test result is shown in figure 4. It can be seen that the monitoring results of the two reference electrodes are different, a potential deviation of 47mV at most appears, and the potential values of the negative electrode and the reference electrode do not completely conform to the three-order platform characteristics of graphite, which indicates that a larger error exists in the potential value obtained by directly using a lithium metal sheet as the reference electrode. The causes of the error may be: during the production and operation of the lithium sheet, once oxygen is contacted, an oxide layer is generated on the surface of the lithium sheet, and the stability and accuracy of the reference electrode potential are affected due to different oxidation degrees.
Comparative example 2
In this example, a soft package battery with a copper wire as a reference electrode is prepared, and the preparation steps are as follows:
(1) preparing positive electrode slurry by taking a nickel-cobalt lithium aluminate material as a positive electrode, coating the two surfaces of the positive electrode slurry on a 15-micron aluminum foil, and rolling and punching to obtain a positive electrode plate; preparing negative electrode slurry by taking graphite as a negative electrode, coating two surfaces of the negative electrode slurry on copper foil with the thickness of 8 mu m, and rolling and punching to prepare a negative electrode piece, wherein the size of the negative electrode piece is 70mm multiplied by 156 mm;
(2) the positive pole pieces, the diaphragm and the negative pole pieces are overlapped in a Z shape to prepare the galvanic pile, the number of the negative pole pieces is 8, the number of the positive pole pieces is 7, two preprocessed copper wires (marked as 1# and 2#) are added between the positive pole and the negative pole in the galvanic pile manufacturing process to serve as reference electrodes, a certain distance is reserved between the two copper wires, an exposed copper wire (the diameter is 20 mu m) is arranged inside the galvanic pile, and an enameled wire is arranged outside the galvanic pile;
(3) and (3) connecting the anode aluminum foil and the aluminum tab of the galvanic pile and the cathode copper foil and the nickel tab of the galvanic pile by ultrasonic welding, then packaging the galvanic pile with the reference electrode by adopting an aluminum-plastic film, injecting 20g of electrolyte, vacuumizing, sealing, welding the exposed copper wire with the nickel tab and then fixing to obtain the soft package battery with the copper wire as the reference electrode.
The prepared soft package battery with the copper wire as the reference electrode is subjected to 0.1C charging and discharging test, in-situ lithium plating is respectively carried out on the copper wire 1# and the copper wire 2# before the test, the potential values of the anode and the copper wire 1#, the cathode and the copper wire 1#, the anode and the copper wire 2#, and the cathode and the copper wire 2# are monitored in the test process, and the test result is shown in figure 5. It can be seen that the monitoring results of the two reference electrodes have obvious deviation in the low SOC interval, which confirms that there is an error in using the copper wire as the reference electrode. The causes of the error may be: the copper wire is arranged between the positive electrode and the negative electrode, so that the current density distribution of the area is abnormal, the reference potential is disturbed by the current, and the stability and the accuracy of the reference potential are influenced.
The comparison of the embodiment 1, the comparative example 1 and the comparative example 2 shows that the soft package battery with the constant potential reference electrode effectively improves the accuracy of the reference electrode in an electrochemical performance test, and has profound significance for the research on the reasonability of the lithium ion battery design, the power matching performance, the cycle attenuation mechanism and the interface stability of the lithium ion battery.
The invention has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to be construed in a limiting sense. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, which fall within the scope of the present invention. The scope of the invention is defined by the appended claims.
Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.
Claims (10)
1. A preparation method of a soft package battery with a constant potential reference electrode is characterized by comprising the following steps:
s1, coating positive electrode slurry on both sides of the aluminum foil, rolling and punching to obtain a positive electrode plate; coating negative electrode slurry on two sides of a copper foil, and rolling and punching to obtain a negative electrode plate;
s2, overlapping the positive pole piece, the diaphragm and the negative pole piece in a Z shape to obtain the galvanic pile, wherein the number of the negative pole pieces is 1 more than that of the positive pole pieces;
s3, after the surface of the cathode pole piece at the outermost side of the pile is covered with a diaphragm, placing a lithium metal sheet connected with a nickel pole lug, then coating the lithium metal sheet with the diaphragm, and carrying out insulation treatment and fixation on the lithium metal sheet; the lithium metal sheet is used as a reference electrode, and the nickel electrode lug connected with the lithium metal sheet is used as a reference electrode lug;
s4, welding an aluminum foil in the positive pole piece of the pile with an aluminum tab, and welding a copper foil in the negative pole piece of the pile with a nickel tab; the aluminum lug and the nickel lug welded with the copper foil are respectively a positive lug and a negative lug;
s5, sequentially packaging the galvanic pile containing the reference electrode, injecting liquid, vacuumizing and sealing to obtain a soft package three-electrode battery;
s6, connecting a reference electrode tab and a negative electrode tab of the soft-package three-electrode battery to charging and discharging equipment, and performing electrochemical treatment on an oxide layer on the surface of the reference electrode through discharging to obtain the soft-package battery with the constant-potential reference electrode.
2. The method for preparing the flexible package battery with the constant-potential reference electrode according to claim 1, wherein in the step S3, the width of the lithium metal sheet is 0.1-0.8 times of the negative electrode sheet, and the length of the lithium metal sheet is 0.1-0.8 times of the negative electrode sheet.
3. The method for preparing a pouch battery with a constant potential reference electrode according to claim 1, wherein in the step S3, the thickness of the lithium metal sheet is 10-100 μm.
4. The method for preparing a flexible package battery with a constant potential reference electrode according to claim 1, wherein in the step S3, the lithium metal sheet placement area is located in an area corresponding to the negative electrode sheet.
5. The method for preparing the laminate battery with the constant-potential reference electrode according to claim 1, wherein in the step S4, an aluminum foil and an aluminum tab in a positive electrode plate of the stack are welded by ultrasonic welding, and a copper foil and a nickel tab in a negative electrode plate of the stack are welded by ultrasonic welding.
6. The method for preparing the pouch battery with the constant-potential reference electrode according to claim 1, wherein in the step S5, an aluminum plastic film is used for packaging a galvanic pile containing the reference electrode, and the amount of the electrolyte used in liquid injection is 4-8 g/Ah.
7. The method for preparing the soft package battery with the constant potential reference electrode according to claim 1, wherein in the step S6, a negative electrode tab of the soft package three-electrode battery is connected to a positive electrode of a charging and discharging device, and a reference electrode tab of the soft package three-electrode battery is connected to a negative electrode of the charging and discharging device.
8. The method for preparing a pouch battery with a constant potential reference electrode according to claim 1 or 7, wherein in the step S6, the pouch three-electrode battery is discharged with a constant current.
9. The method for preparing a pouch battery with a constant potential reference electrode according to claim 8, wherein in the step S6, the constant current I is used for discharging the pouch three-electrode batteryr5 to 200 muA, discharge time trIs 2-5 h.
10. A soft package battery with a constant potential reference electrode is characterized in that the soft package battery with the constant potential reference electrode is obtained by the preparation method of the soft package battery with the constant potential reference electrode according to any one of claims 1 to 9, is used for testing the electrochemical performance of a lithium ion battery, and researches on the design rationality, the power matching performance and the cycle attenuation mechanism of the lithium ion battery are carried out by monitoring the potential changes of a positive electrode and the reference electrode and the potential changes of a negative electrode and the reference electrode in the testing process; or the research on the interface stability of the lithium ion battery is carried out by monitoring the impedance changes of the anode and the reference electrode and the impedance changes of the cathode and the reference electrode under different states.
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