CN113782723A - Positive pole piece, preparation method thereof and lithium ion battery - Google Patents
Positive pole piece, preparation method thereof and lithium ion battery Download PDFInfo
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- CN113782723A CN113782723A CN202111024262.8A CN202111024262A CN113782723A CN 113782723 A CN113782723 A CN 113782723A CN 202111024262 A CN202111024262 A CN 202111024262A CN 113782723 A CN113782723 A CN 113782723A
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- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 43
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 42
- 238000002360 preparation method Methods 0.000 title claims abstract description 6
- 238000000576 coating method Methods 0.000 claims abstract description 118
- 239000011248 coating agent Substances 0.000 claims abstract description 113
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 101
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 101
- 238000005245 sintering Methods 0.000 claims abstract description 45
- 230000014759 maintenance of location Effects 0.000 claims abstract description 19
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 claims abstract description 3
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 claims abstract description 3
- 238000004804 winding Methods 0.000 claims description 12
- 239000006258 conductive agent Substances 0.000 claims description 5
- 239000000853 adhesive Substances 0.000 claims description 4
- 230000001070 adhesive effect Effects 0.000 claims description 4
- 239000011149 active material Substances 0.000 claims description 2
- 239000011247 coating layer Substances 0.000 claims 3
- 238000000034 method Methods 0.000 abstract description 15
- 230000010287 polarization Effects 0.000 abstract description 5
- 238000001556 precipitation Methods 0.000 abstract description 5
- 239000007774 positive electrode material Substances 0.000 abstract description 2
- 239000011505 plaster Substances 0.000 abstract 2
- 239000011267 electrode slurry Substances 0.000 description 14
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 11
- 229910052782 aluminium Inorganic materials 0.000 description 11
- 239000011888 foil Substances 0.000 description 11
- 238000012360 testing method Methods 0.000 description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 238000004806 packaging method and process Methods 0.000 description 4
- 238000005096 rolling process Methods 0.000 description 4
- 238000007789 sealing Methods 0.000 description 4
- 239000002033 PVDF binder Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 3
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 3
- 239000010405 anode material Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- FLAFBICRVKZSCF-UHFFFAOYSA-N [Li].[Co]=O.[Li] Chemical compound [Li].[Co]=O.[Li] FLAFBICRVKZSCF-UHFFFAOYSA-N 0.000 description 1
- 239000006256 anode slurry Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000002134 carbon nanofiber Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 229910021389 graphene Inorganic materials 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- -1 polytetrafluoroethylene Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 238000000926 separation method 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
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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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
- H01M10/05—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
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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
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
- H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
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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
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- 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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Abstract
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a positive pole piece and a preparation method thereof, and a lithium ion battery, wherein the positive pole piece comprises a positive current collector, a first active coating and a second active coating, the first active coating is coated on the long plaster coating surface of the positive current collector, the second active coating is coated on the short plaster coating surface of the positive current collector, and the first active coating and the second active coating are both positive active materials containing high-voltage lithium cobalt oxide; the sintering temperature of the high-voltage lithium cobaltate in the first active coating is different from that of the high-voltage lithium cobaltate in the second active coating, and the gram capacity of the high-voltage lithium cobaltate is different, so that the overpotential of the long paste coating surface of the positive electrode current collector is reduced, and the polarization of the high-voltage lithium cobaltate in the circulation process can be reduced, so that the lithium precipitation phenomenon and the capacity retention rate of the high-voltage lithium cobaltate lithium ion battery in the circulation process can be improved.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a positive pole piece, a preparation method of the positive pole piece and a lithium ion battery.
Background
The lithium cobaltate material as the lithium ion battery anode material has the advantages of high voltage, high compaction density and the like, and is an ideal lithium ion battery anode material, but under the conventional charging voltage of about 4.2V, the capacity of the lithium cobaltate material is limited, and the volume energy density of the battery can be improved by improving the charging voltage of the lithium cobaltate battery. Therefore, the research of the lithium ion battery at present is transferred to high-voltage (the charging voltage is more than or equal to 4.45V) lithium cobaltate as the positive electrode material of the lithium ion battery, the volume energy density of the battery can be improved, but the polarization is large in the circulating process, the problems of lithium precipitation, fast capacity attenuation and the like are easy to occur, and the problems are mainly solved by improving the dynamic performance of the negative electrode at present, but cannot be completely solved.
In view of the above, it is necessary to provide a solution to the above technical problems, which is used to improve the lithium deposition phenomenon and capacity retention rate of the high-voltage lithium cobalt oxide lithium ion battery during the cycling process.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the positive pole piece, the preparation method thereof and the lithium ion battery are provided, so that the polarization of high-voltage lithium cobaltate in the circulating process can be reduced, and the lithium separation phenomenon and the capacity retention rate of the high-voltage lithium cobaltate lithium ion battery in the circulating process can be improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a positive pole piece, which comprises a positive pole current collector, a first active coating and a second active coating, wherein the first active coating is coated on the long paste coating surface of the positive pole current collector, the second active coating is coated on the short paste coating surface of the positive pole current collector, and the first active coating and the second active coating are both positive pole active materials containing high-voltage lithium cobalt oxide; the sintering temperature of the high-voltage lithium cobaltate in the first active coating is different from that of the high-voltage lithium cobaltate in the second active coating, the gram capacity of the high-voltage lithium cobaltate is different, the overpotential of the long paste coating surface of the positive electrode current collector is reduced, and the polarization of the high-voltage lithium cobaltate in the circulating process can be reduced, so that the lithium precipitation phenomenon and the capacity retention rate of the high-voltage lithium cobaltate lithium ion battery in the circulating process can be improved. Preferably, the positive electrode current collector is one of an aluminum foil, a carbon-coated aluminum foil, a lithium iron phosphate-coated aluminum foil, and the like. Wherein, the thickness of the first active coating is 50-90 um, and the thickness of the second active coating is 50-90 um.
Preferably, the high-voltage lithium cobaltate in the first active coating and the high-voltage lithium cobaltate in the second active coating are sintered twice, the first sintering temperature of the high-voltage lithium cobaltate in the first active coating is T11, the second sintering temperature of the high-voltage lithium cobaltate in the first active coating is T12, the first sintering temperature of the high-voltage lithium cobaltate in the second active coating is T21, and the second sintering temperature of the high-voltage lithium cobaltate in the second active coating is T22; wherein T11> T12, and T21> T22.
Preferably, the first sintering temperature of the high-voltage lithium cobaltate in the first active coating is T11, the second sintering temperature of the high-voltage lithium cobaltate in the first active coating is T12, the first sintering temperature of the high-voltage lithium cobaltate in the second active coating is T21, and the second sintering temperature of the high-voltage lithium cobaltate in the second active coating is T22; wherein, T21-T11 is more than or equal to 20 ℃ and less than or equal to 100 ℃; T22-T12 is more than or equal to 20 ℃ and less than or equal to 100 ℃.
Preferably, the first sintering temperature T11 of the high-voltage lithium cobaltate in the first active coating ranges from 1000 ℃ to 1050 ℃, and the second sintering temperature T12 of the high-voltage lithium cobaltate in the first active coating ranges from 800 ℃ to 950 ℃; the first sintering temperature T21 of the high-voltage lithium cobaltate in the second active coating ranges from 1020 ℃ to 1150 ℃, and the second sintering temperature T22 of the high-voltage lithium cobaltate in the second active coating ranges from 820 ℃ to 1050 ℃.
Preferably, the gram capacity of the high voltage lithium cobaltate in the first active coating is greater than the gram capacity of the high voltage lithium cobaltate in the second active coating.
Preferably, the gram capacity of the high-voltage lithium cobaltate in the first active coating is A, the gram capacity of the high-voltage lithium cobaltate in the second active coating is B, and the A-B is more than or equal to 0.8mAh/g and less than or equal to 2.0 mAh/g.
Preferably, the gram capacity A of the high-voltage lithium cobaltate in the first active coating is in the range of 186-195 mAh/g; the gram capacity B of the high-voltage lithium cobaltate in the second active coating ranges from 184 mAh/g to 194.2 mAh/g.
Preferably, the mass ratio of each component of the first active coating is as follows:
high voltage lithium cobaltate: 96.5 to 97.2 percent;
conductive agent: 0.8 to 1.5 percent;
the conductive agent is one or more of conductive carbon black, carbon nano tubes, carbon nano fibers, conductive graphite, graphene and the like.
Adhesive: 1.3% -2.7%;
the binder is one or more of polyvinylidene fluoride, polytetrafluoroethylene and modified products thereof.
The mass ratio of the components of the second active coating is as follows:
high voltage lithium cobaltate: 96.5 to 97.2 percent;
conductive agent: 0.8 to 1.5 percent;
adhesive: 1.3% -2.7%;
in a second aspect, the invention provides a method for preparing a positive electrode plate, comprising the following steps:
preparing a first active coating and a second active coating, and coating the first active coating on the long paste coating surface of the positive current collector; coating the second active coating on the short paste coating surface of the positive current collector; and preparing the positive pole piece.
In a third aspect, the invention provides a lithium ion battery, the lithium ion battery is formed by winding a positive pole piece, a negative pole piece and a diaphragm, the positive pole piece is the positive pole piece, the capacity retention rate of the lithium ion battery after 100 times of circulation at the temperature of 45 ℃ reaches more than 96.3% @100T, the capacity retention rate of the lithium ion battery after 200 times of circulation at the temperature of 45 ℃ reaches more than 92.1% @200T, and the capacity retention rate of the lithium ion battery after 300 times of circulation at the temperature of 45 ℃ reaches more than 88.4% @ 300T.
Compared with the prior art, the beneficial effects of the invention include but are not limited to:
the invention improves the over-potential distribution of the high-voltage lithium cobaltate on the long coating surface of the positive electrode current collector by coating the active coatings with different high-voltage lithium cobaltate gram capacities and different high-voltage lithium cobaltate sintering temperatures on the two sides of the positive electrode, thereby reducing the polarization of the high-voltage lithium cobaltate in the circulating process and improving the lithium precipitation phenomenon and the capacity retention rate of the high-voltage lithium cobaltate in the circulating process.
Drawings
Fig. 1 is a schematic structural diagram of a positive electrode sheet according to the present invention.
In fig. 1: 10-positive current collector; 20-a first reactive coating; 30-second reactive coating
Detailed Description
Embodiments of the present application will be described in detail below. The examples of the present application should not be construed as limiting the present application.
The present application is further illustrated with reference to specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the claims.
Example 1
The first positive electrode slurry with the gram capacity of 191.5mAh/g of high-voltage lithium cobaltate is obtained by mixing 97.2% to 1.5% to 1.3% of high-voltage lithium cobaltate in percentage by mass, the first sintering temperature T11 of the high-voltage lithium cobaltate is 1030 ℃, the second sintering temperature T12 is 930 ℃, and the first positive electrode slurry is coated on the long paste coating surface of the aluminum foil of the positive electrode current collector to form a first active coating with the thickness of 60 mu m; the second positive electrode slurry with the high-voltage lithium cobaltate gram capacity of 189.5mAh/g is obtained by 97.2% to 1.5% to 1.3% by mass of the high-voltage lithium cobaltate, the first sintering temperature T21 of the high-voltage lithium cobaltate is 1130 ℃, the second sintering temperature T22 is 1030 ℃, and the second positive electrode slurry is coated on the short paste coating surface of the positive electrode current collector aluminum foil to form a second active coating with the thickness of 60 mu m; obtaining a positive pole piece, rolling, slitting and manufacturing the positive pole piece, then winding the manufactured positive pole piece, a negative pole piece and a diaphragm to obtain a winding core, packaging the winding core to obtain a dry cell, baking the dry cell, injecting, forming, secondary sealing and sorting to obtain a lithium ion battery, and finally testing the lithium ion battery.
Example 2
The first positive electrode slurry with the gram capacity of 191.5mAh/g of high-voltage lithium cobaltate is obtained by mixing 97.2% to 1.5% to 1.3% of high-voltage lithium cobaltate in percentage by mass, the first sintering temperature T11 of the high-voltage lithium cobaltate is 1030 ℃, the second sintering temperature T12 is 930 ℃, and the first positive electrode slurry is coated on the long paste coating surface of the aluminum foil of the positive electrode current collector to form a first active coating with the thickness of 60 mu m; the second positive electrode slurry with the high-voltage lithium cobaltate gram capacity of 190.5mAh/g is obtained by the mass percent ratio of 97.2% to 1.5% to 1.3% of high-voltage lithium cobaltate, the first sintering temperature T21 of the high-voltage lithium cobaltate is 1080 ℃, the second sintering temperature T22 is 980 ℃, the second positive electrode slurry is coated on the short paste coating surface of the positive electrode current collector aluminum foil, and a second active coating with the thickness of 60 mu m is formed; obtaining a positive pole piece, rolling, slitting and manufacturing the positive pole piece, then winding the manufactured positive pole piece, a negative pole piece and a diaphragm to obtain a winding core, packaging the winding core to obtain a dry cell, baking the dry cell, injecting, forming, secondary sealing and sorting to obtain a lithium ion battery, and finally testing the lithium ion battery.
Example 3
The first positive electrode slurry with the gram capacity of 191.5mAh/g of high-voltage lithium cobaltate is obtained by mixing 97.2% to 1.5% to 1.3% of high-voltage lithium cobaltate in percentage by mass, the first sintering temperature T11 of the high-voltage lithium cobaltate is 1030 ℃, the second sintering temperature T12 is 930 ℃, and the first positive electrode slurry is coated on the long paste coating surface of the aluminum foil of the positive electrode current collector to form a first active coating with the thickness of 60 mu m; the second positive electrode slurry with the high-voltage lithium cobaltate gram capacity of 191mAh/g is obtained by mixing 97.2% to 1.5% and 1.3% of polyvinylidene fluoride in percentage by mass, the first sintering temperature T21 of the high-voltage lithium cobaltate is 1060 ℃, the second sintering temperature T22 is 960 ℃, the second positive electrode slurry is coated on the short coating paste surface of the positive electrode current collector aluminum foil, and a second active coating with the thickness of 60 mu m is formed; obtaining a positive pole piece, rolling, slitting and manufacturing the positive pole piece, then winding the manufactured positive pole piece, a negative pole piece and a diaphragm to obtain a winding core, packaging the winding core to obtain a dry cell, baking the dry cell, injecting, forming, secondary sealing and sorting to obtain a lithium ion battery, and finally testing the lithium ion battery.
Comparative example 1
High-voltage lithium cobaltate, conductive carbon black and polyvinylidene fluoride according to a proportion of 97.2%: 1.5%: 1.3 percent of the mass percentage ratio to obtain the anode slurry with the gram capacity of the high-voltage lithium cobaltate of 191.0mAh/g, the first sintering temperature of the high-voltage lithium cobaltate is 1060 ℃, the second sintering temperature is 960 ℃, when the anode piece is coated, coating the positive electrode slurry on the long paste coating surface of the positive electrode current collector aluminum foil to form an active coating with the thickness of 60um, coating the positive electrode slurry on the short paste coating surface of the positive electrode current collector aluminum foil to form an active coating with the thickness of 60um, obtaining a positive electrode piece, rolling, slitting and sheet-making the positive pole piece, then winding the sheet-made positive pole piece, negative pole piece and diaphragm to obtain a roll core, packaging the roll core to obtain a dry battery core, baking the dry battery core, injecting, forming, secondary sealing and sorting to obtain the lithium ion battery, and finally testing the lithium ion battery.
And (3) performance testing:
the prepared lithium ion battery is subjected to cycle test, and specific test data are shown in the following table 1:
TABLE 1
As can be seen from Table 1, in the examples 1, 2 and 3, compared with the comparative example 1, the capacity retention rate of the lithium ion battery with the active coatings coated on the two sides of the positive electrode and having different gram capacities of the high-voltage lithium cobaltate and different sintering temperatures of the high-voltage lithium cobaltate is superior to the capacity retention rate of the active coatings coated on the two sides of the positive electrode and having the same gram capacities of the high-voltage lithium cobaltate and the same sintering temperature of the high-voltage lithium cobaltate, the capacity retention rate of the lithium ion battery can reach 96.3% @100T after the lithium ion battery is cycled for 100 times at the temperature of 45 ℃, the capacity retention rate can reach 92.1% @200T after the lithium ion battery is cycled for 200 times at the temperature of 45 ℃, and the capacity retention rate can reach 88.4% @300T after the lithium ion battery is cycled for 300 times at the temperature of 45 ℃.
Further, as is clear from comparison of examples 1, 2 and 3, the difference in the first sintering temperatures (T11-T21) of the high-voltage lithium cobaltates of the double-sided active coatings in examples 1, 2 and 3 was 100 ℃, 50 ℃ and 30 ℃, and the difference in the second sintering temperatures (T12-T22) of the high-voltage lithium cobaltates of the double-sided active coatings in examples 1, 2 and 3 was 100 ℃, the difference values of the gram capacities of the high-voltage lithium cobaltate of the double-sided active coating in the embodiment 1, the embodiment 2 and the embodiment 3 are (A-B) 2mAh/g, 1mAh/g and 0.5mAh/g respectively at 50 ℃ and 30 ℃, the capacity retention rate of the lithium ion battery of the embodiment 1 is better than that of the lithium ion battery of the embodiment 2, and the capacity retention rate of the lithium ion battery of the embodiment 2 is better than that of the lithium ion battery of the embodiment 3. Within the numerical range defined by the invention, the larger the difference between the gram capacities of the high-voltage lithium cobaltate coated on both sides is, and the larger the difference between the sintering temperatures of the high-voltage lithium cobaltate is, the higher the capacity retention ratio is, and the more the lithium precipitation phenomenon is improved.
Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. The present invention is illustrated by the above-mentioned examples, but the present invention is not limited to the above-mentioned detailed process equipment and process flow, i.e. it is not meant to imply that the present invention must rely on the above-mentioned detailed process equipment and process flow to be practiced. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Claims (10)
1. The positive pole piece is characterized by comprising a positive pole current collector, a first active coating and a second active coating, wherein the first active coating is coated on the long paste coating surface of the positive pole current collector, the second active coating is coated on the short paste coating surface of the positive pole current collector, and the first active coating and the second active coating are both positive pole active materials containing high-voltage lithium cobalt oxide; the sintering temperature of the high-voltage lithium cobaltate in the first active coating and the sintering temperature of the high-voltage lithium cobaltate in the second active coating are different, the gram capacity of the high-voltage lithium cobaltate is different, and the overpotential of the long paste coating surface of the positive electrode current collector is reduced.
2. The positive electrode sheet according to claim 1, wherein the high voltage lithium cobaltate in the first active coating and the second active coating are sintered twice, the first sintering temperature of the high voltage lithium cobaltate in the first active coating is T11, the second sintering temperature of the high voltage lithium cobaltate in the first active coating is T12, the first sintering temperature of the high voltage lithium cobaltate in the second active coating is T21, and the second sintering temperature of the high voltage lithium cobaltate in the second active coating is T22; wherein T11> T12, and T21> T22.
3. The positive electrode sheet according to claim 2, wherein the sintering temperature difference between the high-voltage lithium cobaltate in the first active coating and the high-voltage lithium cobaltate in the second active coating is in a range of: T21-T11 is more than or equal to 20 ℃ and less than or equal to 100 ℃; T22-T12 is more than or equal to 20 ℃ and less than or equal to 100 ℃.
4. The positive electrode sheet according to claim 2, wherein the first sintering temperature T11 of the high-voltage lithium cobaltate in the first active coating is in the range of 1000-1050 ℃, and the second sintering temperature T12 of the high-voltage lithium cobaltate in the first active coating is in the range of 800-950 ℃; the first sintering temperature T21 of the high-voltage lithium cobaltate in the second active coating ranges from 1020 ℃ to 1150 ℃, and the second sintering temperature T22 of the high-voltage lithium cobaltate in the second active coating ranges from 820 ℃ to 1050 ℃.
5. The positive electrode sheet according to claim 1, wherein the gram capacity of the high voltage lithium cobaltate in the first active coating layer is larger than the gram capacity of the high voltage lithium cobaltate in the second active coating layer.
6. The positive electrode sheet according to claim 5, wherein the gram capacity of the high-voltage lithium cobaltate in the first active coating is A, and the gram capacity of the high-voltage lithium cobaltate in the second active coating is B, wherein A-B is more than or equal to 0.8mAh/g and less than or equal to 2.0 mAh/g.
7. The positive electrode plate as claimed in claim 6, wherein the gram volume A of the high voltage lithium cobaltate in the first active coating layer is in the range of 186-195 mAh/g; the gram capacity B of the high-voltage lithium cobaltate in the second active coating ranges from 184 mAh/g to 194.2 mAh/g.
8. The positive electrode sheet according to claim 1,
the mass ratio of each component of the first active coating is as follows:
high voltage lithium cobaltate: 96.5 to 97.2 percent;
conductive agent: 0.8 to 1.5 percent;
adhesive: 1.3% -2.7%;
the mass ratio of the components of the second active coating is as follows:
high voltage lithium cobaltate: 96.5 to 97.2 percent;
conductive agent: 0.8 to 1.5 percent;
adhesive: 1.3 to 2.7 percent.
9. A preparation method of a positive pole piece is characterized by comprising the following steps:
preparing a first active coating and a second active coating, and coating the first active coating on the long paste coating surface of the positive current collector; coating the second active coating on the short paste coating surface of the positive current collector; preparing the positive pole piece according to any one of claims 1 to 8.
10. A lithium ion battery, characterized in that, the lithium ion battery is formed by winding a positive pole piece, a negative pole piece and a diaphragm, the positive pole piece is the positive pole piece according to any one of claims 1 to 8, the capacity retention rate of the lithium ion battery circulating 100 times under the temperature condition of 45 ℃ reaches more than 96.3% @100T, the capacity retention rate of the lithium ion battery circulating 200 times under the temperature condition of 45 ℃ reaches more than 92.1% @200T, and the capacity retention rate of the lithium ion battery circulating 300 times under the temperature condition of 45 ℃ reaches more than 88.4% @ 300T.
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Application publication date: 20211210 |