CN114284564B - Soft-packed battery with constant potential reference electrode and preparation method thereof - Google Patents
Soft-packed 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 22
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 60
- 238000000034 method Methods 0.000 claims abstract description 27
- 238000007599 discharging Methods 0.000 claims abstract description 15
- 230000008569 process Effects 0.000 claims abstract description 14
- 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 31
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 31
- 229910052759 nickel Inorganic materials 0.000 claims description 19
- 239000011267 electrode slurry Substances 0.000 claims description 18
- 238000012360 testing method Methods 0.000 claims description 17
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 16
- 239000011248 coating agent Substances 0.000 claims description 16
- 238000000576 coating method Methods 0.000 claims description 16
- 239000011889 copper foil Substances 0.000 claims description 16
- 229910001416 lithium ion Inorganic materials 0.000 claims description 16
- 239000011888 foil Substances 0.000 claims description 14
- 238000012544 monitoring process Methods 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 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
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 238000007789 sealing Methods 0.000 claims description 6
- 125000004122 cyclic group Chemical group 0.000 claims description 4
- 238000002347 injection Methods 0.000 claims description 3
- 239000007924 injection Substances 0.000 claims description 3
- 238000011160 research Methods 0.000 claims description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 15
- 230000008859 change Effects 0.000 abstract description 5
- 238000000840 electrochemical analysis Methods 0.000 abstract description 3
- 238000004458 analytical method Methods 0.000 abstract description 2
- 230000002688 persistence Effects 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 229910002804 graphite Inorganic materials 0.000 description 6
- 239000010439 graphite Substances 0.000 description 6
- 229910052802 copper Inorganic materials 0.000 description 5
- 239000010949 copper Substances 0.000 description 5
- 238000007747 plating Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- PFYQFCKUASLJLL-UHFFFAOYSA-N [Co].[Ni].[Li] Chemical compound [Co].[Ni].[Li] PFYQFCKUASLJLL-UHFFFAOYSA-N 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 230000002687 intercalation Effects 0.000 description 2
- 238000009830 intercalation Methods 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000000243 solution Substances 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
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 238000002788 crimping Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
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- 238000009826 distribution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
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- 230000004048 modification Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
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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-packed battery with a constant potential reference electrode, which comprises the steps of firstly overlapping a positive pole piece, a diaphragm and a negative pole piece in a Z shape to prepare a galvanic pile, then covering the surface of the negative pole piece at the outermost side of the galvanic pile with the diaphragm, placing a lithium metal sheet as the reference electrode, connecting and packaging electrode lugs, and performing electrochemical treatment on an oxide layer on the surface of the reference electrode by using a discharging process to obtain the soft-packed battery with the constant potential reference electrode. The preparation method is simple and wide in application range, the reliability, stability and persistence of the reference electrode in electrochemical test are effectively improved, meanwhile, independent analysis of lithium potential and impedance change of the positive electrode and the negative electrode in different states can be realized, and important basis can be provided for optimizing battery design, analyzing electrode interface stability, circulating 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 development process of the lithium ion battery, the reference electrode is introduced as an important auxiliary design method, and the positive electrode and the negative electrode of the battery can be separately researched by adding the reference electrode in the battery, so that the potential and impedance changes of the positive electrode and the negative electrode in different states can be independently analyzed, and an important basis is provided for optimizing the design of the battery, analyzing the interface stability of the electrode, the cyclic attenuation mechanism and the like.
The metal lithium is the most commonly used reference electrode in lithium ion batteries, and the adding modes mainly comprise two modes: (1) Copper wires, platinum wires, gold wires and the like are added into the battery core, and in-situ lithium plating is performed before use; (2) The lithium metal wire, the lithium metal belt, the lithium metal sheet and the like are directly connected into the battery. However, the accuracy of the potential of the reference electrode is less reported, and the foreign published article (Journal of Power Sources 481 (2021) 228933) proves that the potential error of the reference electrode of the lithium ion battery exists, and the copper wire with the diameter of 200 μm is adopted as the reference electrode, so that the potential error exceeding 67mV exists when the battery is charged at 0.6C by monitoring the change of the potential of the negative electrode in the charging process of different multiplying powers and combining the surface morphology of the negative electrode piece after the full-state disassembly, and the potential error can be reduced but cannot be eliminated along with the reduction of the size of the reference electrode. Therefore, a precise and reliable reference electrode with constant potential needs to be introduced into the battery, and the potential of the reference electrode is ensured to be kept constant all the time, so that accurate positive and negative electrode potential and impedance information can be obtained.
The Chinese patent application (publication No. CN 107293778A) 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 reference electrode is arranged between a positive pole piece and a negative pole piece and separated by a diaphragm, the other end of the reference electrode is an enameled wire, the enameled wire is led out of the battery and connected with a nickel tab, and the surface of the copper wire is required to be plated with lithium before alternating current impedance is tested. The diameter of the reference electrode is smaller than the thickness of the diaphragm and the particle size 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 lithium plating layer can increase the size of the reference electrode, so that the current is disturbed to the reference potential in the charge and discharge process, 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 plating is performed in advance before each monitoring, so that the operation procedure is increased.
The Chinese patent application (publication No. CN 106785068B) 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 pole piece and a negative electrode pole piece and separated by a diaphragm, and in order to avoid interference of the reference electrode, a blank area of uncoated sizing agent is reserved on the positive electrode pole piece and the negative electrode pole piece at the corresponding positions of the reference electrode. However, the invention is only applicable to small-capacity soft-pack batteries, and the influence of the oxide layer on the surface 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 provide a preparation method of a soft-packed 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 pile, then covering the surface of the outermost negative electrode plate of the pile with the diaphragm, placing a lithium metal plate as the reference electrode, connecting and packaging electrode lugs, and performing electrochemical treatment on an oxide layer on the surface of the reference electrode by using a discharging process to obtain the soft-packed battery with the constant potential reference electrode. The preparation method is simple and wide in application range, the reliability, stability and persistence of the reference electrode in electrochemical test are effectively improved, meanwhile, independent analysis of lithium potential and impedance change of the positive electrode and the negative electrode in different states can be realized, and important basis can be provided for optimizing battery design, analyzing electrode interface stability, circulating attenuation mechanism and the like.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a preparation method of a soft-packed battery with a constant potential reference electrode comprises the following steps:
s1, coating positive electrode slurry on two sides of an aluminum foil, and rolling and punching to obtain a positive electrode plate; coating the two sides of the copper foil with negative electrode slurry, and rolling and punching to obtain a negative electrode plate;
s2, overlapping the positive pole pieces, the diaphragm and the negative pole pieces in a Z shape to prepare a 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 galvanic pile is covered with a diaphragm, placing a lithium metal sheet connected with the nickel pole lug, coating the lithium metal sheet with the diaphragm, and insulating and fixing the lithium metal sheet; the lithium metal sheet is used as a reference electrode, and the nickel tab connected with the lithium metal sheet is used as a reference electrode tab;
s4, welding aluminum foil in a positive pole piece of the galvanic pile with an aluminum tab, and welding copper foil in a negative pole piece of the galvanic pile with a nickel tab; the aluminum electrode lug and the nickel electrode lug welded with the copper foil are respectively a positive electrode lug and a negative electrode lug;
s5, packaging the galvanic pile containing the reference electrode in sequence, injecting liquid, vacuumizing and sealing to obtain the soft-package three-electrode battery;
and S6, connecting a reference electrode lug and a negative electrode lug of the soft-package three-electrode battery into charge and discharge equipment, and carrying out electrochemical treatment on an oxide layer on the surface of the reference electrode through discharge 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 that of the negative electrode sheet, and the length of the lithium metal sheet is 0.1 to 0.8 times that of the negative electrode sheet.
Further, in the step S3, the thickness of the lithium metal sheet is 10 to 100. Mu.m.
Further, in the step S3, the lithium metal sheet placement area is located in an area corresponding to the negative electrode sheet.
Further, in the step S4, an aluminum foil in the positive electrode plate of the galvanic pile is welded with an aluminum tab by ultrasonic welding, and a copper foil in the negative electrode plate of the galvanic pile is welded with a nickel tab.
In step S5, the reference electrode-containing galvanic pile is encapsulated by an aluminum plastic film, and the electrolyte consumption during the liquid injection is 4-8 g/Ah.
Further, in step S6, a negative electrode tab of the soft-pack three-electrode battery is connected to a positive electrode of the charge/discharge device, and a reference electrode tab of the soft-pack three-electrode battery is connected to a negative electrode of the charge/discharge device.
Further, in the step S6, the soft-pack three-electrode battery is discharged with a constant current.
Further, in the step S6, a constant current I for discharging the soft-pack three-electrode battery r 5-200 mu A, discharge time t r 2 to 5 hours.
The soft-packed battery with the constant potential reference electrode is obtained by adopting the preparation method of the soft-packed battery with the constant potential reference electrode, is used for testing the electrochemical performance of the lithium ion battery, and is used for researching the design rationality, the power matching property and the cyclic attenuation mechanism of the lithium ion battery by monitoring the potential changes of the positive electrode and the reference electrode and the negative electrode and the reference electrode in the testing process; or the interface stability research of the lithium ion battery is carried out by monitoring the impedance changes of the positive electrode and the reference electrode and the impedance changes of the negative electrode and the reference electrode under different states.
Compared with the prior art, the invention has the following beneficial effects:
(1) In the preparation method of the soft-packed battery with the constant potential reference electrode, the lithium metal sheet is used as the reference electrode, and the electrochemical treatment is carried out on the oxide layer on the surface of the lithium metal sheet used as the reference electrode by utilizing the discharging process, so that impurities and oxides are removed, the reference potential is ensured to be constant all the time, the accuracy and the durability of the reference electrode in the electrochemical test are effectively improved, and the reliability and the stability of the soft-packed three-electrode battery in application are further improved;
(2) According to the preparation method of the soft-package battery with the constant potential reference electrode, disclosed by the invention, the interference of current change on the reference potential in the charge and discharge process can be avoided by arranging the lithium metal sheet at the outermost side of the electric pile, so that the reference potential is always kept constant;
(3) The preparation method of the soft-packed battery with the constant potential reference electrode is simple and wide in application range, and the soft-packed battery can be used for testing the electrochemical performance of the lithium ion battery, can independently analyze the lithium potential and impedance change of the positive electrode and the negative electrode in different states, and can provide important basis for optimizing the design of the battery, analyzing the stability of the electrode interface, the cyclic attenuation mechanism and the like.
Drawings
FIG. 1 is a schematic view of the stack overlap of the present invention;
fig. 2 is a schematic diagram of a flexible battery with a constant potential reference electrode according to the present invention;
fig. 3 is a graph showing the monitoring result of the battery voltage in example 1;
fig. 4 is a graph of the battery voltage monitoring result in comparative example 1;
fig. 5 is a graph showing the results of monitoring the battery voltage in comparative example 2.
Detailed Description
The features and advantages of the present invention will become more apparent and clear from the following detailed description of the invention.
The word "exemplary" is used 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. Although various aspects of the embodiments are illustrated in the accompanying 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, and rolling and punching to obtain a positive electrode plate; coating the copper foil with negative electrode slurry on both sides, and rolling and punching to obtain a negative electrode plate;
step two, overlapping the positive pole pieces, the diaphragm and the negative pole pieces in a Z shape to prepare a galvanic pile, wherein the number of the negative pole pieces is 1 more than that of the positive pole pieces;
thirdly, after the surface of the cathode pole piece at the outermost side of the galvanic pile is covered with a diaphragm, placing a lithium metal sheet which is cut in advance and is connected with a nickel pole lug as a reference electrode, coating the lithium metal sheet by the diaphragm, and insulating and fixing the lithium metal sheet;
fourthly, connecting an anode aluminum foil and an aluminum tab of the galvanic pile and connecting a cathode copper foil and a nickel tab by ultrasonic welding, and then packaging the galvanic pile with a reference electrode by using an aluminum plastic film, injecting liquid, vacuumizing and sealing to obtain the soft-package three-electrode battery;
fifthly, connecting a reference electrode lug and a negative electrode lug of the soft-package three-electrode battery into the charging and discharging equipment, connecting the battery negative electrode lug with the positive electrode of the charging and discharging equipment, connecting the battery reference electrode lug with the negative electrode of the charging and discharging equipment, and using constant current I r Discharging it for a period of time t r So as to remove oxide and impurities on the surface of the reference electrode, and prepare the soft-packed battery with the constant potential reference electrode.
Further, in the method for manufacturing a flexible battery with a constant potential reference electrode, in the third step, the width of the lithium metal sheet is 0.1 to 0.8 times of the width of the negative electrode sheet, and the length of the lithium metal sheet is 0.1 to 0.8 times of the length of the negative electrode sheet.
Further, in the preparation method of the soft-packed battery with the constant potential reference electrode, in the third step, the thickness of the lithium metal sheet is 10-100 μm;
further, in the method for manufacturing a flexible battery with a constant potential reference electrode, in the third step, the placement area of the lithium metal sheet is required 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 electrode sheet is positioned in the area of the negative electrode sheet;
further, in the preparation method of the soft-packed battery with the constant potential reference electrode, in the fourth step, the electrolyte dosage during liquid injection is 4-8 g/Ah;
further, in the preparation method of the soft-packed battery with the constant potential reference electrode, in the fifth step, I r Selected to be 5-200 mu A, t r Selecting for 2-5 h.
The soft-packed battery with the constant potential reference electrode is obtained by adopting the preparation method of the soft-packed battery with the constant potential reference electrode, the soft-packed 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 positive electrode and the reference and the potential changes of the negative electrode and the reference are monitored in the testing process, so that the soft-packed battery with the constant potential reference electrode can be used for researching the design rationality, the power matching property and the circulating attenuation mechanism of the lithium ion battery; the impedance changes of the positive electrode and the reference and the impedance changes of the negative electrode and the reference are monitored, and the method can be used for researching the interface stability of the lithium ion battery.
Example 1
A soft package battery with 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 positive electrode slurry on 15 mu m aluminum foil on two sides, and rolling and punching to prepare a positive electrode plate; preparing negative electrode slurry by taking graphite as a negative electrode, coating the negative electrode slurry on 8 mu m copper foil on two sides, and rolling and punching to obtain a negative electrode plate, wherein the size of the negative electrode plate is 70mm multiplied by 156mm;
(2) Overlapping the positive pole pieces, the diaphragms and the negative pole pieces in a Z shape to prepare a pile, wherein the number of the negative pole pieces is 8, the number of the positive pole pieces is 7, and a schematic diagram of the pile is shown in figure 1;
(3) Cutting a lithium metal sheet with the thickness of 50 mu m into a size of 30mm multiplied by 50mm, and pressing and connecting nickel lugs;
(4) After the surface of the outermost negative electrode plate of the galvanic pile is coated with a diaphragm, placing a cut lithium metal sheet in a central area corresponding to the negative electrode plate as a reference electrode, and coating the lithium metal sheet with the diaphragm to perform insulation and fixation;
(5) The method comprises the steps of connecting an anode aluminum foil and an aluminum tab of a galvanic pile and connecting a cathode copper foil and a nickel tab by ultrasonic welding, packaging the galvanic pile with a reference electrode by adopting 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, 1 is the cathode tab, 2 is the anode tab, 3 is the galvanic pile, 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 lug and a negative electrode lug of the soft-package three-electrode battery into a charging and discharging device, connecting a battery negative electrode lug with a positive electrode of the charging and discharging device, discharging the battery reference electrode lug with a negative electrode of the charging and discharging device with a constant current of 10 mu A for 5 hours, and preparing the soft-package battery with the constant potential reference electrode.
And carrying out 0.1C charge and discharge test on the prepared soft-packed battery with the constant potential reference electrode, monitoring potential values of the positive electrode and the reference and potential values of the negative electrode and the reference in the test process, wherein the test result is shown in figure 3. It can be seen that the potential value between the positive electrode and the reference and the potential value between the negative electrode and the reference have no abnormal and noise points, the negative electrode curve presents a typical graphite three-order lithium intercalation platform, the voltages of the lithium intercalation platforms are respectively 0.20V, 0.12V and 0.08V, and the voltages are consistent with the characteristic values of graphite, so that the accuracy of the reference electrode is verified.
Comparative example 1
In this comparative example, a soft-pack battery using a lithium metal sheet directly as a reference electrode was prepared as follows:
(1) Preparing positive electrode slurry by taking lithium cobaltate material as a positive electrode, coating the positive electrode slurry on 15 mu m aluminum foil on two sides, and rolling and punching to prepare a positive electrode plate; preparing negative electrode slurry by taking graphite as a negative electrode, coating the negative electrode slurry on 8 mu m copper foil on two sides, and rolling and punching to obtain a negative electrode plate, wherein the size of the negative electrode plate is 70mm multiplied by 156mm;
(2) Overlapping the positive plates, the diaphragms and the negative plates in a Z shape to prepare a 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 a size of 30mm multiplied by 50mm, crimping 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 the corresponding area of the cathode plate outside the galvanic pile from top to bottom, and cladding, insulating and fixing the reference electrode A and the reference electrode B by using a diaphragm;
(5) And (3) connecting an anode aluminum foil and an aluminum tab of the galvanic pile and connecting a cathode copper foil and a nickel tab by ultrasonic welding, packaging the galvanic pile with the reference electrode by adopting an aluminum plastic film, injecting 20g of electrolyte, vacuumizing and sealing to prepare the soft package battery with the lithium metal sheet as the reference electrode.
And (3) carrying out 0.1C charge-discharge test on the prepared soft-package battery with the lithium metal sheet as the reference electrode, monitoring 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 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, the potential deviation of 47mV at maximum appears, and the potential values of the negative electrode and the reference electrodes do not completely accord with the three-stage platform characteristics of graphite, which indicates that the potential values obtained by directly adopting the lithium metal sheet as the reference electrode have larger errors. Errors may be due to: in the production and operation process 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 can be affected due to different oxidation degrees.
Comparative example 2
The preparation method of the soft-packed battery using the copper wire as the reference electrode comprises the following steps:
(1) Preparing positive electrode slurry by taking a nickel cobalt lithium aluminate material as a positive electrode, coating the positive electrode slurry on 15 mu m aluminum foil on two sides, and rolling and punching to prepare a positive electrode plate; preparing negative electrode slurry by taking graphite as a negative electrode, coating the negative electrode slurry on 8 mu m copper foil on two sides, and rolling and punching to obtain a negative electrode plate, wherein the size of the negative electrode plate is 70mm multiplied by 156mm;
(2) Overlapping positive plates, diaphragms and negative plates in a Z shape to prepare a pile, wherein the number of the negative plates is 8, the number of the positive plates is 7, two pretreated copper wires (marked as 1# and 2 #) are added between the positive plates and the negative plates as reference electrodes in the pile manufacturing process, a certain distance is reserved between the two copper wires, the inside of the pile is exposed copper wires (the diameter is 20 mu m), and the outside of the pile is enameled wires;
(3) And (3) connecting an anode aluminum foil and an aluminum tab of the galvanic pile and connecting a cathode copper foil and a nickel tab by ultrasonic welding, packaging the galvanic pile with the reference electrode by adopting an aluminum plastic film, injecting 20g of electrolyte, vacuumizing, sealing, and fixing the exposed copper wire after welding the nickel tab to prepare the soft-package battery with the copper wire as the reference electrode.
And carrying out 0.1C charge and discharge test on the prepared soft-packed battery with the copper wire as the reference electrode, respectively carrying out in-situ lithium plating on the copper wire 1# and the copper wire 2# before the test, monitoring potential values of the positive electrode and the copper wire 1#, the negative electrode and the copper wire 1#, the positive electrode and the copper wire 2#, and the negative electrode and the copper wire 2#, in the test process, wherein 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, and the fact that the copper wire is adopted as the reference electrode has errors is confirmed. Errors may be due to: the copper wire is positioned between the anode and the cathode, which can cause abnormal current density distribution in the area where the copper wire is positioned, and the reference potential can be subjected to current disturbance, so that the stability and the accuracy of the reference potential are affected.
As can be seen from the comparison of the above example 1, the comparative example 1 and the comparative example 2, the soft-package battery with the constant potential reference electrode effectively improves the accuracy of the reference electrode in the electrochemical performance test, and has profound significance for the researches on the design rationality, the power matching property, the cycle attenuation mechanism and the interface stability of the lithium ion battery.
The invention has been described in detail in connection with the specific embodiments and exemplary examples thereof, but such description is not to be construed as limiting the invention. It will be understood by those skilled in the art 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, and these fall within the scope of the present invention. The scope of the invention is defined by the appended claims.
What is not described in detail in the present specification is a well known technology to those skilled in the art.
Claims (8)
1. The preparation method of the soft-packed battery with the constant potential reference electrode is characterized by comprising the following steps of:
s1, coating positive electrode slurry on two sides of an aluminum foil, and rolling and punching to obtain a positive electrode plate; coating the two sides of the copper foil with negative electrode slurry, and rolling and punching to obtain a negative electrode plate;
s2, overlapping the positive pole pieces, the diaphragm and the negative pole pieces in a Z shape to prepare a 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 galvanic pile is covered with a diaphragm, placing a lithium metal sheet connected with the nickel pole lug, coating the lithium metal sheet with the diaphragm, and insulating and fixing the lithium metal sheet; the lithium metal sheet is used as a reference electrode, and the nickel tab connected with the lithium metal sheet is used as a reference electrode tab;
s4, welding aluminum foil in a positive pole piece of the galvanic pile with an aluminum tab, and welding copper foil in a negative pole piece of the galvanic pile with a nickel tab; the aluminum electrode lug and the nickel electrode lug welded with the copper foil are respectively a positive electrode lug and a negative electrode lug;
s5, packaging the galvanic pile containing the reference electrode in sequence, injecting liquid, vacuumizing and sealing to obtain the soft-package three-electrode battery;
s6, connecting a reference electrode lug and a negative electrode lug of the soft-packaged three-electrode battery into charge-discharge equipment, and performing electrochemical treatment on an oxide layer on the surface of the reference electrode through discharge to obtain the soft-packaged battery with the constant potential reference electrode;
in the step S6, a negative electrode tab of the soft-packaged three-electrode battery is connected with a positive electrode of the charging and discharging device, and a reference electrode tab of the soft-packaged three-electrode battery is connected with a negative electrode of the charging and discharging device;
in the step S6, a constant current I for discharging the soft-packed three-electrode battery r 5-200 mu A, discharge time t r 2 to 5 hours.
2. The method according to claim 1, wherein in the step S3, the width of the lithium metal sheet is 0.1-0.8 times of the width 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 manufacturing a flexible 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 to 100 μm.
4. The method 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 manufacturing a flexible battery with a constant potential reference electrode according to claim 1, wherein in the step S4, an aluminum foil in a positive electrode sheet of a galvanic pile is welded with an aluminum tab by ultrasonic welding, and a copper foil in a negative electrode sheet of the galvanic pile is welded with a nickel tab.
6. The method for preparing a flexible battery with a constant potential reference electrode according to claim 1, wherein in the step S5, an aluminum plastic film is used to encapsulate a galvanic pile containing the reference electrode, and the electrolyte consumption during liquid injection is 4-8 g/Ah.
7. The method according to claim 1, wherein in the step S6, the soft-packed three-electrode battery is discharged with a constant current.
8. A flexible battery with a constant potential reference electrode, characterized in that the flexible battery is obtained by adopting the preparation method of the flexible battery with the constant potential reference electrode as claimed in any one of claims 1-7, is used for testing the electrochemical performance of a lithium ion battery, and is used for researching the design rationality, the power matching property and the cyclic attenuation mechanism of the lithium ion battery by monitoring the potential changes of a positive electrode and the reference electrode and a negative electrode and the reference electrode in the testing process; or the interface stability research of the lithium ion battery is carried out by monitoring the impedance changes of the positive electrode and the reference electrode and the impedance changes of the negative electrode and the reference electrode under different states.
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