CN115548496A - Lithium ion battery and preparation method thereof - Google Patents
Lithium ion battery and preparation method thereof Download PDFInfo
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- CN115548496A CN115548496A CN202211513291.5A CN202211513291A CN115548496A CN 115548496 A CN115548496 A CN 115548496A CN 202211513291 A CN202211513291 A CN 202211513291A CN 115548496 A CN115548496 A CN 115548496A
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- lithium ion
- ion battery
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- reference substance
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 55
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 55
- 238000002360 preparation method Methods 0.000 title description 7
- 229910052751 metal Inorganic materials 0.000 claims abstract description 49
- 239000002184 metal Substances 0.000 claims abstract description 49
- 239000013558 reference substance Substances 0.000 claims abstract description 45
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 38
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 38
- 239000011248 coating agent Substances 0.000 claims abstract description 29
- 238000000576 coating method Methods 0.000 claims abstract description 29
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000011230 binding agent Substances 0.000 claims abstract description 14
- 239000006258 conductive agent Substances 0.000 claims abstract description 14
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims abstract description 9
- 239000002002 slurry Substances 0.000 claims abstract description 8
- 238000004519 manufacturing process Methods 0.000 claims abstract description 6
- 238000004806 packaging method and process Methods 0.000 claims abstract description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 28
- 238000000034 method Methods 0.000 claims description 21
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 16
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 10
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 10
- -1 polytetrafluoroethylene Polymers 0.000 claims description 9
- 238000002156 mixing Methods 0.000 claims description 7
- 239000002033 PVDF binder Substances 0.000 claims description 6
- 239000006230 acetylene black Substances 0.000 claims description 6
- 239000002041 carbon nanotube Substances 0.000 claims description 5
- 239000011247 coating layer Substances 0.000 claims description 5
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 5
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 5
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 4
- 239000004642 Polyimide Substances 0.000 claims description 4
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 4
- 229920002125 Sokalan® Polymers 0.000 claims description 4
- 239000004917 carbon fiber Substances 0.000 claims description 4
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 4
- 229910021389 graphene Inorganic materials 0.000 claims description 4
- 239000003273 ketjen black Substances 0.000 claims description 4
- 239000004584 polyacrylic acid Substances 0.000 claims description 4
- 229920001721 polyimide Polymers 0.000 claims description 4
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 4
- 239000011888 foil Substances 0.000 abstract description 9
- 238000012544 monitoring process Methods 0.000 abstract description 8
- 230000007774 longterm Effects 0.000 abstract description 5
- 230000036541 health Effects 0.000 abstract description 3
- 239000012925 reference material Substances 0.000 abstract description 2
- 238000012827 research and development Methods 0.000 abstract description 2
- 238000012360 testing method Methods 0.000 description 12
- 238000007747 plating Methods 0.000 description 7
- 230000008569 process Effects 0.000 description 7
- 239000003792 electrolyte Substances 0.000 description 6
- 239000010410 layer Substances 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 238000007600 charging Methods 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 3
- 239000011149 active material Substances 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000007772 electrode material Substances 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
- 230000032677 cell aging Effects 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- 238000013112 stability test Methods 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000010277 constant-current charging Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 239000011267 electrode slurry Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 238000001453 impedance spectrum Methods 0.000 description 1
- 230000016507 interphase Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 1
- 229910052808 lithium carbonate Inorganic materials 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- 239000002562 thickening agent Substances 0.000 description 1
- 238000004506 ultrasonic cleaning Methods 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
-
- 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
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The lithium ion battery comprises a positive plate, a negative plate, a reference electrode and a diaphragm, wherein the diaphragm separates the positive plate, the negative plate and the reference electrode from each other; the reference electrode includes a metal wire and a coating of a reference substance disposed on an outer periphery of the metal wire. Also disclosed is a method of making a lithium ion battery comprising preparing a reference electrode by coating a slurry of an active reference material, a conductive agent, and a binder on a metal wire; placing a reference electrode between the positive plate or the negative plate and the conventional diaphragm; and packaging. The lithium ion battery uses lithium titanate or lithium iron phosphate as an active reference substance and adopts a non-foil type current collector, so that the reference electrode has long-term stability, can be used as a lithium ion battery reference electrode with the service life as long as that of a battery cell, and is applied to research and development of battery cell products and monitoring of product health states.
Description
Technical Field
The invention relates to a lithium ion battery, in particular to a lithium ion battery with a reference electrode and a manufacturing method thereof.
Background
Lithium ion batteries have been widely used in various electronic products, new energy vehicles, energy storage, and other fields because of their advantages of high energy density, long cycle life, small size, and low cost. For various applications, the volume energy density, the quick charging capability, the safety and the service life of the lithium ion battery are the most critical performance indexes. In the use process of the lithium ion battery, the electrolyte and the anode and cathode materials of the battery undergo a complex electrochemical process and slowly undergo side reactions, such as electrolyte consumption, thickening of an SEI (solid electrolyte interphase) film of the cathode, voltage reduction, lithium precipitation of the cathode and the like, so that the performance indexes of the lithium ion battery are influenced. Thus, there is a need for a method for in-situ, real-time monitoring of chemical and electrochemical reactions inside lithium ion batteries to understand the state of health of the cells. The three-electrode method is characterized in that a reference electrode is implanted in the battery, so that the positive and negative electrode potentials can be tested in situ, the electrochemical impedance spectrum of the positive and negative electrodes can be analyzed, the interface reaction between the pole piece and electrolyte can be researched, the performance condition of the battery can be judged without disassembling the battery, and researches such as a battery cell aging mechanism, charging strategies at different aging stages and the like can be further developed.
The traditional three-electrode lithium ion battery adopts a mode of plating lithium on a copper wire or internally arranging a metal lithium electrode to introduce a reference electrode, and has the defects that the metal lithium of the high-activity reference electrode continuously reacts with electrolyte in a circulation process, so that the metal lithium of the reference electrode is continuously consumed, and by-products generated by the reaction of the metal lithium and the electrolyte are deposited on the surface of the reference electrode, so that the monitoring of the reference potential loses accuracy. In order to improve the stability of the reference electrode in the lithium ion battery environment, studies have been made to adopt an active material having a stable electrode potential within a wide SOC interval as the reference electrode, such as a slurry made of a stable potential material such as lithium iron phosphate or lithium titanate is coated on a current collector foil to form the reference electrode, and then the reference electrode is placed between a positive electrode and a negative electrode. However, this production method has the following problems: the positive and negative surfaces of the reference electrode pole piece need to be subjected to potential adjustment respectively; the reference electrode has thicker pole piece and larger size, and causes electrochemical isolation to a certain degree on the positive pole piece and the negative pole piece of the contact surface; the adhesion stability of the reference electrode material on the narrow strip-shaped current collector foil is poor, so that the reliability of the reference electrode in the monitoring working process is influenced.
Therefore, improvement of a three-electrode lithium ion battery is still needed, a stable and reliable reference electrode is obtained, and long-term stable monitoring of the battery electrode potential is realized.
Disclosure of Invention
In view of the above problems in the current three-electrode lithium ion battery, the present inventors have conducted a great deal of experiments to overcome these problems item by item.
Accordingly, in one aspect, the present invention provides a lithium ion battery comprising a positive plate, a negative plate, a reference electrode, and a separator, wherein the separator separates the positive plate, the negative plate, and the reference electrode from each other; the reference electrode comprises a metal lead and a reference substance coating layer arranged on the periphery of the metal lead.
In another aspect, the present invention provides a method for preparing the aforementioned lithium ion battery, comprising:
(1) Mixing an active reference substance, a conductive agent and a binder to prepare slurry, partially coating the slurry on a metal wire to form an active reference substance coating, so that one end of the metal wire is completely coated by the active reference substance coating, and the other end of the metal wire extends out of the active reference substance coating;
(2) Placing the part of the reference electrode coated with the active reference substance coating between a positive plate and a negative plate of a lithium ion battery cell, and isolating the part of the reference electrode coated with the active reference substance coating from the positive plate or the negative plate through another diaphragm;
(3) And leading out the metal lead of the reference electrode which is not coated with the active reference substance coating from the battery cell and electrically connecting the metal lead to the reference electrode pole, and then packaging the battery cell to obtain the lithium ion battery.
According to the invention, the active reference substance is coated on the metal wire, and the reference electrode is prepared by adopting a non-foil type current collector. When the reference electrode is used for adjusting the potential in the battery core, only one of the positive electrode and the negative electrode of the battery is needed to be used for charging and discharging adjustment, and the potential of the front surface and the back surface of the reference battery is not needed to be adjusted respectively.
In addition, the active reference substance layers on the front side and the back side of the reference electrode pole piece manufactured by adopting the foil type current collector are not communicated, and potential difference exists during lithium plating, so that the accuracy of a three-electrode potential test result is influenced.
Furthermore, according to the present invention, when the active reference material is coated, a flexible adhesive is preferably used, so that the reference electrode is tightly attached to the diaphragm in the battery cell, and the conditions of material peeling, material falling from the metal wire, and the like due to the influence of the pressure stress between the pole pieces are not generated.
Drawings
Fig. 1 shows a schematic view of a reference electrode according to an exemplary embodiment of the present invention, for example, in which a single-stranded linear metal wire is used for the sectional view (a), a double-stranded linear metal wire is used for the sectional view (b), a single-stranded curved metal wire is used for the sectional view (c), and a double-stranded U-shaped metal wire is used for the sectional view (d).
Fig. 2 shows a reference potential map of a lithium ion battery using a stable lithium titanate reference electrode prepared according to example 1 of the present invention during a high temperature cycle, that is, a graph of the potential of the negative electrode of the lithium titanate reference electrode vs as a function of time at 45 ° and 1/3 ℃ cycles, at the 5 th cycle and at the 56 th cycle.
Fig. 3 shows a reference potential map of a lithium ion battery using a conventional copper wire plated lithium reference electrode in a high temperature cycle process, that is, a graph of a change of a potential of a negative electrode of a copper wire plated lithium reference electrode vs with time at the 5 th cycle and the 56 th cycle under 45 ℃ and 1/3 ℃ cycles.
Detailed Description
The present application will be described in further detail with reference to the following drawings and examples. The features and advantages of the present application will become more apparent from the description.
In addition, the technical features described below in the different embodiments of the present application may be combined with each other as long as they do not conflict with each other.
In one aspect, the invention provides a lithium ion battery, which comprises a positive plate, a negative plate, a reference electrode and a diaphragm, wherein the diaphragm separates the positive plate, the negative plate and the reference electrode from each other; the reference electrode comprises a metal lead and a reference substance coating layer arranged on the periphery of the metal lead.
In this context, the metal wire in the reference electrode may be a single-stranded linear metal wire, a double-stranded linear metal wire, a single-stranded curvilinear metal wire, a double-stranded U-shaped metal wire, or other shapes, as shown in fig. 1, without any particular limitation.
In one embodiment of the lithium ion battery according to the present invention, the reference electrode side is a conventional separator disposed between the positive and negative electrode sheets, and a separator is additionally disposed on the side opposite to the positive or negative electrode sheet to prevent electrical contact with the positive or negative electrode sheet. More preferably, the reference electrode is disposed between the negative electrode sheet and the conventional separator.
In one embodiment of the lithium ion battery according to the present invention, the metal lead is flat or cylindrical. Here, the shape of the wire refers to the cross-sectional shape of the wire.
In one embodiment of the lithium ion battery according to the present invention, the metal wire may be a copper wire, a nickel wire, and preferably a copper wire.
In one embodiment of the lithium ion battery according to the invention, the diameter of the metal wire, in particular of the copper wire, is from 3 to 30 μm.
In one embodiment of the lithium ion battery according to the present invention, the active reference substance coating layer includes 55 to 98 wt% of the active reference substance, 1 to 30 wt% of the conductive agent, and 1 to 15wt% of the binder.
In one embodiment of the lithium ion battery according to the invention, the active reference substance is lithium titanate or lithium iron phosphate, preferably lithium titanate.
The reference electrode requires the potential to be kept constant in the using process, so that a reversible electrode and a difficult-to-polarize electrode are usually selected as the reference electrode, and an electrode material with high multiplying power characteristic and a relatively flat charging and discharging platform is generally adopted. Lithium titanate and lithium iron phosphate can stably not react with electrolyte in a lithium ion battery system, and have stable electrode potential in a wide SOC interval. Therefore, according to the invention, the reference electrode prepared by using lithium titanate or lithium iron phosphate as an active reference substance has long-term stability, can be used as a lithium ion battery reference electrode with the same service life as a battery cell, and is applied to research and development of battery cell products and health state monitoring of the products.
In one embodiment of the lithium ion battery according to the present invention, the conductive agent is at least one selected from the group consisting of conductive acetylene black, ketjen black, conductive carbon black, carbon nanotubes, carbon fibers, and graphene.
In one embodiment of the lithium ion battery according to the present invention, the binder is at least one selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl alcohol, polyacrylic acid, and polyimide, and preferably polytetrafluoroethylene.
According to the invention, in the active reference substance coating, a flexible adhesive is preferably used, so that the reference electrode is tightly attached to the diaphragm in the battery cell, and the conditions of material peeling, material falling off from a metal lead and the like under the influence of stress between pole pieces are avoided, therefore, compared with the reference electrode made of a foil-type current collector, the reference electrode has better long-term stability.
In the reference electrode according to the present invention, a non-foil current collector is used, and an active reference substance is coated on a metal wire, so that when the reference electrode according to the present invention is used for potential adjustment in a battery cell, only one of the positive and negative electrodes of the battery is used for charge and discharge adjustment, and the positive and negative surfaces of the reference battery pole piece made of the foil current collector are respectively used for potential adjustment. In addition, the active reference substance layers on the front side and the back side of the reference electrode pole piece manufactured by adopting the foil type current collector are not communicated, and potential difference exists during lithium plating, so that the accuracy of the three-electrode potential test result is influenced.
In another aspect, the present invention further provides a preparation method of the foregoing lithium ion battery, including:
(1) Mixing an active reference substance, a conductive agent and a binder to prepare slurry, partially coating the slurry on a metal wire to form an active reference substance coating, so that one end of the metal wire is completely coated by the active reference substance coating, and the other end of the metal wire extends out of the active reference substance coating;
(2) The part of the reference electrode coated with the active reference substance coating is arranged between a positive plate and a negative plate of a lithium ion battery cell and is isolated from the positive plate or the negative plate through another diaphragm;
(3) And leading out the metal lead of the reference electrode which is not coated with the active reference substance coating from the battery cell and electrically connecting the metal lead to the reference electrode pole, and then packaging the battery cell to obtain the lithium ion battery.
In the method according to the present invention, a conventional separator is disposed between the positive electrode sheet and the negative electrode sheet, and a reference electrode is disposed between the conventional separator and the positive electrode sheet or the negative electrode sheet, preferably between the conventional separator and the negative electrode sheet; in order to prevent electrical contact, a separator is additionally arranged on the side of the positive plate or the negative plate opposite to the reference electrode, and the size of the additional separator is as small as possible under the condition that the electrical contact can be prevented so as to reduce the internal resistance of the battery.
In one embodiment of the method according to the invention, the active reference substance is lithium titanate or lithium iron phosphate, preferably lithium titanate; the conductive agent is at least one selected from conductive acetylene black, ketjen black, conductive carbon black, carbon nanotubes, carbon fibers and graphene; the binder is at least one selected from polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl alcohol, polyacrylic acid and polyimide, and polytetrafluoroethylene is preferred.
In one embodiment of the method according to the invention, the active reference substance, the conductive agent and the binder are mixed in a ratio of (55 to 98 wt%) (1 to 30 wt%) (1 to 15wt%).
In one embodiment of the method according to the invention, the metal wire is a copper wire.
Before the conductive copper wire is coated by the active reference substance coating, one end of the conductive copper wire is immersed in concentrated sulfuric acid for about 5 to 300 min, and then ultrasonic cleaning is performed by using dilute hydrochloric acid and deionized water to remove the insulating layer on the surface of the conductive copper wire. As described above, a coating of a reference substance, such as lithium titanate, may be applied over the treated end of, for example, a single strand of copper wire or a plurality of strands of copper wire, the copper wire having a linear or any curvilinear form. Then, one end of the coating which covers the reference substance is pressed and dried to manufacture a flaky lithium titanate reference electrode with the length of 5 to 15 mm, the width of 1 to 2 mm and the thickness of 10 to 50 mu m.
The method comprises the following steps of manufacturing a cell of a lithium ion battery according to a conventional process known by a person skilled in the art, implanting a reference electrode and an auxiliary diaphragm manufactured according to the method of the invention between a positive electrode plate and a negative electrode plate of a naked cell intermediate layer, then leading the other end of a conductive copper wire which is not coated with an active reference substance coating such as a lithium titanate coating out of a battery shell, and then packaging the cell to obtain the lithium ion battery with the stable reference electrode.
The reference electrode prepared by the method has stable performance, can be used as a lithium ion battery reference electrode with the service life of a battery cell and the like, realizes long-term stable monitoring of the electrode potential of the lithium ion battery, and provides feasibility on devices and methods for researching a battery cell aging mechanism, charging strategies at different aging stages and potential product applications, such as formulation of a real-time monitoring scheme of a product battery cell.
The present invention is further illustrated by the following examples. It is to be noted that the materials used in the following examples are commercially available, and are not particularly limited thereto.
Example 1
< preparation of Positive electrode sheet >
Mixing the prepared positive electrode active material, acetylene black as a conductive agent and PVDF as a binder according to a mass ratio of 96; and uniformly coating the positive electrode slurry on two surfaces of the positive electrode current collector aluminum foil, airing at room temperature, transferring to an oven for continuous drying, and then performing cold pressing and slitting to obtain the positive electrode piece.
< preparation of negative electrode sheet >
Mixing graphite serving as a negative electrode active material or a mixture obtained by mixing the graphite with other active materials according to different mass ratios, acetylene black serving as a conductive agent, CMC serving as a thickening agent and SBR according to a mass ratio of 96.4.
< preparation of lithium carbonate reference electrode >
Mixing lithium titanate, conductive carbon black, CNTs and PTFE (polytetrafluoroethylene) according to the mass ratio of 85 to 5.
< preparation of lithium ion Battery >
Preparing a positive plate, a diaphragm and a negative plate into a bare cell in a lamination mode, arranging the diaphragm between the positive plate and the negative plate, arranging a reference electrode on the diaphragm between the positive plate and the negative plate close to the outer layer of the bare cell, then arranging the reference electrode, covering the diaphragm on the reference electrode to separate the reference electrode from the adjacent positive plate or negative plate, and arranging the reference electrode between the positive plate or negative plate and a conventional diaphragm; leading out a conductive copper wire of the lithium titanate reference electrode to the outside of the battery, and then packaging the battery; the drawn copper wire is electrically connected to a nickel lug as a reference electrode binding post.
< reference electrode lithium plating >
And (3) lithium plating is carried out on the prepared battery by using a Land test cabinet, one end of the positive electrode of the test channel of the test cabinet is connected with the positive electrode pole of the battery, one end of the negative electrode of the test channel of the test cabinet is connected with the reference electrode binding post of the battery, constant current charging is carried out on the battery for 4 hours by adopting 0.5mA, after the reference potential is stable, lithium plating of the reference electrode is completed, and the lithium-plated reference electrode battery is obtained.
< stability test >
The battery prepared in example 1 was subjected to a charge-discharge cycle test in a 45 ℃ incubator, the cycle test was performed at 1/3C rate for full charge, and the potential of the negative electrode of the battery was detected by three electrodes during the cycle, so that a reference-negative voltage curve was obtained at different cycle times, and the test results are shown in fig. 2.
Example 2
A battery was fabricated in the same manner as in example 1, except that the reference electrode metal lead was flat in cross section, the reference active material was lithium iron phosphate, and the binder was PVDF (polyvinylidene fluoride).
Lithium plating was performed in the same manner as in example 1, and a reference electrode stability test was performed.
Comparative example 1
A lithium ion battery was prepared in the same manner as in example 1, except that a reference electrode was prepared as follows:
arranging an enameled wire copper wire on a copper foil, and soaking one end of the enameled wire copper wire in concentrated sulfuric acid to remove an insulating layer on the surface of the copper wire; and taking out the copper wire, and then ultrasonically cleaning the copper wire in deionized water and acetone solvent for 10 minutes respectively to remove acid liquor and residues on the surface of the end part of the copper wire so as to prepare the reference electrode.
A full cell containing a reference electrode was prepared and tested in the same manner as in example 1, except that the surface of the reference electrode was not coated with a reference electrode active material, and the test results are shown in fig. 3.
Fig. 2 shows that the negative-reference potential of the stable lithium titanate reference cell (example 1) maintains good stability over a reasonable range of values during high temperature charge-discharge cycling. Fig. 3 shows that the negative-reference potential degenerates below zero volts when the conventional copper wire-plated lithium reference cell (comparative example 1) is cycled up to 56 cycles of high temperature charge and discharge, indicating that the copper wire-plated lithium reference is lost by side reactions at high temperatures and loses the performance of accurately referencing the calibration potential.
In conclusion, the stable lithium titanate reference electrode used in the lithium ion battery can monitor the accurate potentials of the positive electrode and the negative electrode in real time, and meanwhile, the requirements of the performance verification of the full life cycle of the battery can be met based on the stable properties of the stable lithium titanate reference electrode under various extreme test conditions.
The present application has been described above in connection with preferred embodiments, which are, however, merely exemplary and illustrative. On the basis of the above, the invention can be applied to various replacements and improvements and fall into the protection scope of the application.
Claims (12)
1. A lithium ion battery comprises a positive plate, a negative plate, a reference electrode and a diaphragm, wherein the diaphragm separates the positive plate, the negative plate and the reference electrode from each other; the reference electrode comprises a metal lead and a reference substance coating layer arranged on the periphery of the metal lead.
2. The lithium ion battery of claim 1, wherein the metal wire is flat or cylindrical.
3. The lithium ion battery of claim 1, wherein the metal wire is a copper wire.
4. A lithium ion battery according to claim 3, wherein the diameter of the copper wire is 3 to 30 μm, and the thickness of the active reference substance coating is 5 to 500nm.
5. The lithium ion battery according to claim 4, wherein the active reference substance coating layer comprises 55 to 98 wt% of an active reference substance, 1 to 30 wt% of a conductive agent, and 1 to 15wt% of a binder.
6. The lithium ion battery of claim 5, wherein the active reference substance is lithium titanate or lithium iron phosphate, preferably lithium titanate.
7. The lithium ion battery according to claim 5, wherein the conductive agent is at least one selected from the group consisting of conductive acetylene black, ketjen black, conductive carbon black, carbon nanotubes, carbon fibers, and graphene.
8. The lithium ion battery according to claim 5, wherein the binder is at least one selected from polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl alcohol, polyacrylic acid, polyimide, preferably polytetrafluoroethylene.
9. A method of making a lithium ion battery according to any of the preceding claims, comprising:
(1) Mixing an active reference substance, a conductive agent and a binder to prepare slurry, partially coating the slurry on a metal wire to form an active reference substance coating, so that one end of the metal wire is completely coated by the active reference substance coating, and the other end of the metal wire extends out of the active reference substance coating;
(2) The part of the reference electrode coated with the active reference substance coating is arranged between a positive plate and a negative plate of a lithium ion battery cell and is isolated from the positive plate or the negative plate through another diaphragm;
(3) And leading out the metal lead of the reference electrode which is not coated with the active reference substance coating from the battery cell and electrically connecting the metal lead to the reference electrode pole, and then packaging the battery cell to obtain the lithium ion battery.
10. The method according to claim 9, wherein the active reference substance is lithium titanate or lithium iron phosphate, preferably lithium titanate; the conductive agent is at least one selected from conductive acetylene black, ketjen black, conductive carbon black, carbon nanotubes, carbon fibers and graphene; the binder is at least one selected from polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl alcohol, polyacrylic acid and polyimide, and polytetrafluoroethylene is preferred.
11. The method according to claim 9 or 10, wherein the active reference substance, the conductive agent and the binder are mixed in a ratio of (55 to 98 wt%) (1 to 30 wt%) (1 to 15wt%).
12. The method of claim 9, wherein the metal wire is a copper wire.
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| CN117613191A (en) * | 2023-11-30 | 2024-02-27 | 三一红象电池有限公司 | Reference electrode, preparation method thereof and three-electrode battery |
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