CN116936740B - Positive plate and battery using same - Google Patents
Positive plate and battery using same Download PDFInfo
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- CN116936740B CN116936740B CN202311188708.XA CN202311188708A CN116936740B CN 116936740 B CN116936740 B CN 116936740B CN 202311188708 A CN202311188708 A CN 202311188708A CN 116936740 B CN116936740 B CN 116936740B
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- positive electrode
- active material
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- positive
- lithium
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- 239000007774 positive electrode material Substances 0.000 claims abstract description 132
- 239000011248 coating agent Substances 0.000 claims abstract description 10
- 238000000576 coating method Methods 0.000 claims abstract description 10
- 230000009471 action Effects 0.000 claims abstract description 4
- 229910052744 lithium Inorganic materials 0.000 claims description 16
- 239000000463 material Substances 0.000 claims description 16
- 239000003792 electrolyte Substances 0.000 claims description 15
- -1 nickel cobalt aluminum Chemical compound 0.000 claims description 15
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 12
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 11
- 239000011247 coating layer Substances 0.000 claims description 8
- 229910052748 manganese Inorganic materials 0.000 claims description 6
- 239000011572 manganese Substances 0.000 claims description 6
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 claims description 3
- KFDQGLPGKXUTMZ-UHFFFAOYSA-N [Mn].[Co].[Ni] Chemical compound [Mn].[Co].[Ni] KFDQGLPGKXUTMZ-UHFFFAOYSA-N 0.000 claims description 2
- BDKWOJYFHXPPPT-UHFFFAOYSA-N lithium dioxido(dioxo)manganese nickel(2+) Chemical compound [Mn](=O)(=O)([O-])[O-].[Ni+2].[Li+] BDKWOJYFHXPPPT-UHFFFAOYSA-N 0.000 claims description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 44
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 38
- 230000005540 biological transmission Effects 0.000 abstract description 14
- 230000009286 beneficial effect Effects 0.000 abstract 1
- 230000001737 promoting effect Effects 0.000 abstract 1
- 238000012360 testing method Methods 0.000 description 47
- 238000002360 preparation method Methods 0.000 description 44
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 42
- 238000010438 heat treatment Methods 0.000 description 32
- 238000001816 cooling Methods 0.000 description 30
- 239000000203 mixture Substances 0.000 description 29
- 239000002245 particle Substances 0.000 description 29
- 238000003756 stirring Methods 0.000 description 29
- 238000002156 mixing Methods 0.000 description 26
- 229910052751 metal Inorganic materials 0.000 description 25
- 239000002184 metal Substances 0.000 description 25
- 239000002243 precursor Substances 0.000 description 24
- 150000002696 manganese Chemical class 0.000 description 21
- 238000000034 method Methods 0.000 description 21
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 20
- 150000001868 cobalt Chemical class 0.000 description 20
- 150000002815 nickel Chemical class 0.000 description 19
- 230000000052 comparative effect Effects 0.000 description 17
- 238000001035 drying Methods 0.000 description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 15
- 238000001354 calcination Methods 0.000 description 14
- 238000000227 grinding Methods 0.000 description 13
- 239000012266 salt solution Substances 0.000 description 13
- 229910017052 cobalt Inorganic materials 0.000 description 11
- 239000010941 cobalt Substances 0.000 description 11
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 11
- 230000014759 maintenance of location Effects 0.000 description 10
- 229910052759 nickel Inorganic materials 0.000 description 10
- 238000007600 charging Methods 0.000 description 9
- 239000000243 solution Substances 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 8
- 238000006073 displacement reaction Methods 0.000 description 8
- 239000000843 powder Substances 0.000 description 8
- 239000000126 substance Substances 0.000 description 8
- 238000005303 weighing Methods 0.000 description 8
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 7
- 230000008569 process Effects 0.000 description 7
- 238000007599 discharging Methods 0.000 description 6
- 239000002244 precipitate Substances 0.000 description 6
- 238000005406 washing Methods 0.000 description 6
- 229910013553 LiNO Inorganic materials 0.000 description 5
- 230000006835 compression Effects 0.000 description 5
- 238000007906 compression Methods 0.000 description 5
- PQVSTLUFSYVLTO-UHFFFAOYSA-N ethyl n-ethoxycarbonylcarbamate Chemical compound CCOC(=O)NC(=O)OCC PQVSTLUFSYVLTO-UHFFFAOYSA-N 0.000 description 5
- 150000002500 ions Chemical class 0.000 description 5
- GLXDVVHUTZTUQK-UHFFFAOYSA-M lithium hydroxide monohydrate Substances [Li+].O.[OH-] GLXDVVHUTZTUQK-UHFFFAOYSA-M 0.000 description 5
- 229940040692 lithium hydroxide monohydrate Drugs 0.000 description 5
- 239000011259 mixed solution Substances 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 238000002485 combustion reaction Methods 0.000 description 4
- 238000005056 compaction Methods 0.000 description 4
- 238000011161 development Methods 0.000 description 4
- 239000011267 electrode slurry Substances 0.000 description 4
- 229910003002 lithium salt Inorganic materials 0.000 description 4
- 159000000002 lithium salts Chemical class 0.000 description 4
- 238000011068 loading method Methods 0.000 description 4
- 230000002269 spontaneous effect Effects 0.000 description 4
- 102000004310 Ion Channels Human genes 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 239000011230 binding agent Substances 0.000 description 3
- 239000006258 conductive agent Substances 0.000 description 3
- 238000007086 side reaction Methods 0.000 description 3
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 2
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 2
- 239000006230 acetylene black Substances 0.000 description 2
- 239000011149 active material Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000001768 carboxy methyl cellulose Substances 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 238000007872 degassing Methods 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 235000019441 ethanol Nutrition 0.000 description 2
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 2
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 229920003048 styrene butadiene rubber Polymers 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000002174 Styrene-butadiene 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
- 239000012298 atmosphere Substances 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000010280 constant potential charging Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 230000035807 sensation Effects 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 238000009210 therapy by ultrasound Methods 0.000 description 1
- 239000002562 thickening agent Substances 0.000 description 1
- 238000009461 vacuum packaging Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- 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
-
- 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
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
-
- 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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides a positive plate and a battery using the positive plate, wherein the positive plate comprises a positive current collector and a positive active coating arranged on the surface of the positive current collector, the positive active coating contains a positive active material, the positive active material is granular, under the action of external pressure, the maximum bearing value of the positive active material before rupture is MA, the maximum strain of the positive active material before rupture is X, the unit of MA is N, and the positive active material satisfies the condition that MA/X is less than or equal to 60 and less than or equal to 800. In the positive plate provided by the invention, the positive active material is controlled to meet MA/X of 60-800, so that the compressive capacity and mechanical stability of the positive active material can be effectively improved, the positive plate provided by the invention has good structural stability and is not easy to generate microcracks, and on the other hand, the positive plate is beneficial to optimizing the lithium ion transmission dynamics characteristic of the positive active material and promoting the smooth transmission of lithium ions on the positive plate.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a positive plate and a battery using the positive plate.
Background
The lithium ion battery is widely used in daily life, and can alleviate the problems of resource shortage, environmental pollution and the like due to the advantages of high capacity, long service cycle, no pollution and the like. In order to meet the increasing use demands, development of high-performance positive electrode active materials has become an important task in recent years. In lithium ion batteries, the positive electrode active material is one of the most important components, and plays a key role in the performance of the lithium ion battery. When Li+ is inserted into or extracted from a Li layer in the positive electrode active material in the process of charging and discharging the battery, the unit cell volume of the positive electrode active material is correspondingly expanded and contracted, the non-uniform deformation is accumulated to easily cause cracking or breaking of the positive electrode active material, and further, side reaction between the positive electrode and electrolyte is aggravated, and the cycle performance of the battery is worsened.
The high stability and long cycle are main development trends of the current lithium ion power batteries, and the development of the positive electrode material capable of taking the high stability and long cycle life into consideration has great significance for the development of new generation lithium ion batteries by taking the dominant role of the positive electrode active material in influencing factors of the performance of the lithium ion batteries into consideration.
Disclosure of Invention
In order to improve the structural stability of a lithium battery and optimize the cycle characteristics of the lithium ion battery, the invention provides a positive plate and a battery using the positive plate.
According to a first aspect of the present invention, there is provided a positive electrode sheet comprising a positive electrode current collector and a positive electrode active coating layer provided on the surface of the positive electrode current collector, wherein the positive electrode active coating layer contains a positive electrode active material, the positive electrode active material is granular, under the action of external pressure, the maximum bearing value of the positive electrode active material before rupture is MA, the maximum strain of the positive electrode active material before rupture is X, the unit of MA is N, and the positive electrode active material satisfies 60.ltoreq.ma/x.ltoreq.800. According to the positive plate provided by the invention, the positive active material meeting the requirement of MA/X of 60-800 is introduced into the positive active coating, so that the compression resistance and mechanical stability of the positive active material can be effectively improved, the positive plate provided by the invention has good structural stability, microcracks are not easy to generate, the lithium ion transmission dynamics characteristic of the positive active material is favorably optimized, and the smooth transmission of lithium ions on the positive plate is promoted.
According to a second aspect of the present invention, there is provided a battery comprising the positive electrode sheet, separator, negative electrode sheet and electrolyte as described above. The battery of the invention has good structural stability and good cycle characteristics.
Detailed Description
According to a first aspect of the present invention, there is provided a positive electrode sheet comprising a positive electrode current collector and a positive electrode active coating layer provided on the surface of the positive electrode current collector, wherein the positive electrode active coating layer contains a positive electrode active material, the positive electrode active material is granular, under the action of external pressure, the maximum bearing value of the positive electrode active material before rupture is MA, the maximum strain of the positive electrode active material before rupture is X, the unit of MA is N, and the positive electrode active material satisfies 60.ltoreq.ma/x.ltoreq.800. According to the positive plate provided by the invention, the positive active material meeting the requirement of MA/X of 60-800 is introduced into the positive active coating, so that the compression resistance and mechanical stability of the positive active material can be effectively improved, the positive plate provided by the invention has good structural stability and is not easy to generate microcracks, and on the other hand, the positive plate is favorable for optimizing the positive active material to keep good lithium ion transmission dynamics, and the smooth transmission of lithium ions on the positive plate is promoted.
Preferably, the positive electrode active material satisfies: MA/X is less than or equal to 100 and less than or equal to 600. When the positive electrode active material meets the characteristics, the lithium ion transmission characteristic and the battery cycle performance of the positive electrode sheet provided by the invention can be further optimized.
Preferably, the positive electrode active material satisfies 0 < X.ltoreq.0.5.
Preferably, D of the positive electrode active material 50 1 to 10 μm.
Preferably, D of the positive electrode active material 50 Is 2 to 5 μm.
Preferably, the specific surface area of the positive electrode active material is 0.2 to 3m 2 /g。
Preferably, the specific surface area of the positive electrode active material is 0.4 to 1m 2 /g。
Preferably, in the positive electrode active coating layer, the mass of the positive electrode active material is not less than 50% of the total mass of the positive electrode active coating layer.
Preferably, the positive electrode active material includes at least one of a lithium cobaltate material, a lithium nickelate material, a lithium manganate material, a nickel cobalt manganese material, a nickel cobalt aluminum material, a lithium-rich manganese-based material, and a lithium nickel manganate material.
According to a second aspect of the present invention, there is provided a battery comprising the positive electrode sheet, separator, negative electrode sheet and electrolyte as described above. The battery of the invention has good structural stability and good cycle characteristics.
In order that those skilled in the art will better understand the present invention, a technical solution of the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments.
The particle size D50, BET (specific surface area), maximum bearing value and their corresponding maximum strain test methods in the following examples and comparative examples are as follows:
d50 test: 0.02g of the powder sample was put into a 50mL clean beaker, 20mL of ethanol was added thereto, 2 to 3 drops of 1wt% surfactant were further added dropwise thereto, the powder sample was completely dispersed in water, and after 5 minutes of ultrasonic treatment in a 120W ultrasonic cleaner, the particle size distribution was measured by a laser particle size analyzer (MasterSizer 2000).
BET test: weighing the total weight of the empty small test tube and the plug, soaking the powder sample in absolute ethyl alcohol for 4 hours, then putting the powder sample into an oven at the temperature of 100 ℃ for half an hour, cooling, taking out the sample tube by forceps, weighing the total mass (the total mass of the sample, the small test tube and the plug) of the sample tube, and calculating to obtain the sample mass; opening a degassing station, placing a sample tube into the degassing station with the temperature of 100 ℃, purging with nitrogen (pure nitrogen) for 30min, cooling for 15min, performing sample BET test by using a BET tester under the test conditions of the temperature of 25 ℃ and the humidity of 60%, taking P/P0 with the point in the range of 0.05-0.25 as an x axis and P/V (P0-P) as a Y axis, and performing linear fitting by using a BET equation as a graph to obtain the slope and intercept of a straight line so as to calculate the specific surface area of the tested sample.
Maximum bearing value and corresponding maximum strain test: the invention adopts DL3C intelligent particle intensity measuring instrument of Tianjin university rock-soil institute to measure the particle intensity of the particle breaking test of the positive electrode active material, the maximum test force of the measuring instrument is 2kN, the measuring precision is +/-1%, the test speed is 1-500 mm/min, the measuring resolution is 10000 times, the diameter of the test bed is 58mm, and the test stroke is 350 mm; the pellets were continuously dried in an oven for more than 6 hours prior to testing. The particle crushing test adopts a loading mode of displacement control, particles are placed between two rigid plates, axial load is applied by controlling the displacement, the loading rate is 0.5 mm/min, and the load and the displacement are automatically recorded in the test process. When the force-displacement curve shows abrupt drop phenomenon or the particles are obviously subject to crushing, the particles are indicated to be crushed, the test is stopped, crushing stress and corresponding strain are recorded, wherein the crushing stress is the maximum bearing value, and the strain is the maximum strain (maximum deformation amount). Before the experiment, the number of the particles is accurately recorded, the particles are placed at the center of the lower chopping board disc, and then loading parameters are set and loading is started. The data acquisition module can automatically record the contact force and displacement information in the crushing process in real time. Because the irregularities of the particle shape can cause stress concentration to be generated near the contact point between the particle and the rigid plate, local fracturing or corner crushing of the particle is caused, the stress is reflected on a load-displacement curve and suddenly drops, the curve presents a saw-tooth shape, and the maximum bearing value and the strain curve of the particle are further determined according to the characteristics of the contact force-displacement curve and the particle damage mode. The maximum bearing value and maximum strain of the particles can be further determined according to the characteristics of the contact force-displacement curve and the particle failure mode.
At the above test particle size D 50 In BET and maximum bearing values and the corresponding maximum deformation amounts, the adopted test sample is obtained through the following steps: dismantling the battery to be tested with 0% of charge state, taking out the positive plate, scraping the powder of the positive plate, placing the obtained powder in a burning pot, calcining for 4 hours at 450 ℃ in an atmosphere furnace, removing the surface binder and the conductive agent of the positive active material, grinding the sintered powder into powder without obvious granular sensation.
Example 1
(1) Preparation of positive electrode active material
S1, weighing nickel salt, cobalt salt and manganese salt according to the molar ratio of 92:4:4, dissolving the nickel salt, the cobalt salt and the manganese salt in water, mixing uniformly to obtain a metal soluble salt solution, controlling the pH value of the system to be 12.1 under the condition that the stirring rotation speed is 500rpm, stirring and reacting for 8 hours, and washing and drying a precipitate obtained after the reaction, wherein the drying temperature is controlled at 110 ℃ to obtain metal salt hydroxide;
s2, according to Li: m is M Total (S) =1.04 LiOH-LiNO 3 Mixing and grinding molten salt and the metal salt hydroxide, wherein M Total (S) Adding the mole numbers of nickel, cobalt and manganese to obtain a precursor mixture;
s3, placing the precursor mixture into a muffle furnace, and calcining according to the following procedure: heating to 500 ℃ firstly, preserving heat for 3 h, then continuously heating to 850 ℃, preserving heat for 6h, cooling to 800 ℃, preserving heat for 12h, cooling to room temperature along with a furnace, and obtaining the granular positive electrode active material.
The positive electrode active material D in this example was obtained by testing 50 2.75 μm and BET 0.68m 2 And the maximum bearing value MA of the positive electrode active material is 40N, and the corresponding maximum strain X is 0.66, wherein MA and X meet MA/X=60.
(2) Preparation of a Battery
(1) Preparation of positive plate
Mixing the prepared positive electrode active material, a conductive agent acetylene black and a binder PVDF (polyvinylidene fluoride) according to a mass ratio of 96:2:2, adding a solvent NMP (N-methylpyrrolidone), and stirring in a vacuum stirrer until the system is uniform to obtain positive electrode slurry; and uniformly coating the positive electrode slurry on two surfaces of a positive electrode current collector aluminum foil, airing at room temperature, transferring to an oven, continuously drying, and then carrying out cold pressing and cutting to obtain the positive electrode plate.
(2) Preparation of negative electrode sheet
Mixing graphite as a negative electrode active material or a mixture of graphite and other active materials according to different mass ratios, acetylene black as a conductive agent, CMC (sodium carboxymethyl cellulose) as a thickening agent and SBR (styrene butadiene rubber) as a binder according to a mass ratio of 96.4:1:1.2:1.4, adding deionized water as a solvent, and stirring in a vacuum stirrer until the system is uniform to obtain negative electrode slurry; and uniformly coating the negative electrode slurry on two surfaces of a negative electrode current collector copper foil, airing at room temperature, transferring to an oven for continuous drying, and then carrying out cold pressing and slitting to obtain a negative electrode plate.
(3) Preparation of electrolyte
Mixing Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) according to a volume ratio of 1:1:1 to obtain a mixed organic solvent, and then fully drying lithium salt LiPF 6 Dissolving in a mixed organic solvent to prepare the electrolyte with the concentration of 1 mol/L.
(4) Preparation of a separator film
Selected from polyethylene films as barrier films.
(5) Preparation of lithium batteries
Sequentially stacking the positive plate, the isolating film and the negative plate, enabling the isolating film to be positioned between the positive plate and the negative plate to play a role of isolation, and then winding to obtain a bare cell; and placing the bare cell in an outer packaging shell, drying, injecting electrolyte, and performing vacuum packaging, standing, formation, shaping and other procedures to obtain the lithium battery.
Example 2
(1) Preparation of positive electrode active material
In the preparation of the positive electrode active material of this example, the procedure of calcination in S3 was different from that of example 1, and the remainder was identical to that of example 1; the specific calcination procedure for S3 in this example is as follows: heating to 500 ℃ firstly, preserving heat for 3 h, then continuously heating to 900 ℃, preserving heat for 6h, then cooling to 800 ℃, preserving heat for 12h, and then cooling to room temperature along with furnace cooling to obtain the granular positive electrode active material.
The positive electrode active material D in this example was obtained by testing 50 2.89 μm and BET 0.62m 2 And the maximum bearing value MA of the positive electrode active material is 50N, and the corresponding maximum strain X is 0.125, wherein MA and X meet MA/X=400.
(2) Preparation of a Battery
The preparation of the battery of this example was identical to that of example 1.
Example 3
(1) Preparation of positive electrode active material
S1, weighing nickel salt, cobalt salt and manganese salt according to the molar ratio of 92:4:4, dissolving the nickel salt, the cobalt salt and the manganese salt in water, and uniformly mixing to obtain a metal soluble salt solution;
s2, according to Li: m is M Total (S) =1.04 will LiNO 3 Uniformly mixing molten salt and metal soluble salt solution, wherein M Total (S) Adding the mole numbers of nickel, cobalt and manganese, and dripping the obtained mixed solution into a citric acid-glycol water solution, wherein the mole ratio of citric acid to lithium metal ions is 1:1, calculating the input amount of citric acid, stirring to form gel, drying the gel at 140 ℃, and then grinding and crushing to obtain a precursor mixture;
s3, placing the precursor mixture into a muffle furnace, and calcining according to the following procedure: heating to 400 ℃ firstly, preserving heat for 3 h, then continuously heating to 850 ℃, preserving heat for 6h, cooling to 800 ℃, preserving heat for 12h, cooling to room temperature along with a furnace, and obtaining the granular positive electrode active material.
The positive electrode active material D in this example was obtained by testing 50 2.78 μm and BET 0.65m 2 And the maximum bearing value MA of the positive electrode active material is 60N, and the corresponding maximum strain is 0.075, and MA and X meet MA/X=800.
(2) Preparation of a Battery
The preparation of the battery of this example was identical to that of example 1.
Example 4
(1) Preparation of positive electrode active material
S1, weighing nickel salt, cobalt salt and manganese salt according to the molar ratio of 92:4:4, dissolving the nickel salt, the cobalt salt and the manganese salt in water, mixing uniformly to obtain a metal soluble salt solution, controlling the pH value of the system to be 12.1 under the condition that the stirring rotation speed is 500rpm, stirring and reacting for 8 hours, and washing and drying a precipitate obtained after the reaction, wherein the drying temperature is controlled at 110 ℃ to obtain metal salt hydroxide;
s2, according to Li: m is M Total (S) =1.04 LiOH-LiNO 3 Mixing and grinding molten salt and the metal salt hydroxide, wherein M Total (S) Adding the mole numbers of nickel, cobalt and manganese to obtain a precursor mixture;
s3, radiating the precursor mixture by adopting microwaves with the frequency of 2.45GHz 1200W, taking out, placing in a muffle furnace, heating to 850 ℃, preserving heat for 10min, and cooling to room temperature to obtain the granular positive electrode active material.
The positive electrode active material D in this example was obtained by testing 50 2.71 μm and BET of 0.68m 2 And/g, and the maximum bearing value MA of the positive electrode active material is 45N, and the corresponding maximum strain X is 0.45, wherein MA and X meet MA/X=100.
(2) Preparation of a Battery
The preparation of the battery of this example was identical to that of example 1.
Example 5
(1) Preparation of positive electrode active material
S1, mixing lithium element, nickel element, cobalt element and manganese element according to a molar ratio of 1.03:1/3:1/9:1/3 of the lithium hydroxide monohydrate (LiOH-H) 2 O), nickel salt, cobalt salt and manganese salt, dissolving the nickel salt, cobalt salt and manganese salt in water, mixing the materials uniformly to obtain a metal soluble salt solution, controlling the pH value of the system to be 12.1 under the condition of the stirring rotating speed of 500rpm, stirring and reacting for 8 hours, transferring the obtained mixture into an autoclave, sealing the autoclave, and then placing the autoclave in a constant temperature box and preserving the heat for 12 hours at 110 ℃;
s2, taking out the mixture from the autoclave, washing the mixture with ethanol for 5 times, placing the mixture in a 60 ℃ vacuum oven for drying for 12 hours, and grinding the obtained solid to obtain a precursor mixture;
s3, placing the precursor mixture into a muffle furnace, and calcining according to the following procedure: heating to 500 ℃ firstly, preserving heat for 4h, then continuously heating to 850 ℃, preserving heat for 6h, cooling to 800 ℃, preserving heat for 5 h, and cooling to room temperature along with a furnace to obtain the granular positive electrode active material.
The positive electrode active material D in this example was obtained by testing 50 2.76 μm and BET 0.68m 2 And the maximum bearing value MA of the positive electrode active material is 45N, and the corresponding maximum strain X is 0.128, wherein MA and X meet MA/X=350.
(2) Preparation of a Battery
The preparation of the battery of this example was identical to that of example 1.
Example 6
(1) Preparation of positive electrode active material
S1, mixing lithium element, nickel element, cobalt element and manganese element according to a molar ratio of 1.05:0.33:0.33:0.33 lithium hydroxide monohydrate (LiOH-H) 2 O), nickel salt, cobalt salt and manganese salt, dissolving the nickel salt, cobalt salt and manganese salt in water, mixing uniformly to obtain a metal soluble salt solution, controlling the pH=12.1 of the system under the stirring rotation speed of 500rpm, stirring and reacting for 8 hours, and then dripping citric acid solution into the system, wherein the molar ratio of citric acid to lithium metal ions is 1:1 calculating the input of citric acid to obtain a mixtureHeating the mixed solution at a constant temperature of 80 ℃ for 6 hours in a stirring state to form sol;
s2, transferring the sol to an electric furnace for heating, generating spontaneous combustion after about 5min to form fluffy substances, and grinding the fluffy substances to obtain a precursor mixture;
s3, calcining the precursor mixture in a muffle furnace according to the following procedure: heating to 500 ℃ firstly, preserving heat for 4h, then continuously heating to 850 ℃, preserving heat for 6h, cooling to 800 ℃, preserving heat for 5 h, and cooling to room temperature along with a furnace to obtain the granular positive electrode active material.
The positive electrode active material D in this example was obtained by testing 50 2.73 μm and BET 0.68m 2 And the maximum bearing value MA of the positive electrode active material is 40N, and the corresponding maximum strain X is 0.108, wherein MA and X meet MA/X=600.
(2) Preparation of a Battery
The preparation of the battery of this example was identical to that of example 1.
Example 7
(1) Preparation of positive electrode active material
S1, mixing lithium element, nickel element, cobalt element and manganese element according to a molar ratio of 1.05:0.33:0.33:0.33 lithium hydroxide monohydrate (LiOH-H) 2 O), nickel salt, cobalt salt and manganese salt, dissolving the nickel salt, cobalt salt and manganese salt in water, mixing uniformly to obtain a metal soluble salt solution, controlling the pH=12.1 of the system under the stirring rotation speed of 500rpm, stirring and reacting for 8 hours, and then dripping citric acid solution into the system, wherein the molar ratio of citric acid to lithium metal ions is 1:1, calculating the input amount of citric acid, and heating the obtained mixed solution at a constant temperature of 80 ℃ for 6 hours in a stirring state to form sol;
s2, transferring the sol to an electric furnace for heating, generating spontaneous combustion after about 5min to form fluffy substances, and grinding the fluffy substances to obtain a precursor mixture;
s3, calcining the precursor mixture in a muffle furnace according to the following procedure: heating to 800 ℃, preserving heat for 4h, then continuously heating to 1000 ℃, preserving heat for 10 hours, then cooling to 800 ℃, preserving heat for 5 h, and then cooling to room temperature along with furnace cooling to obtain the granular positive electrode active material.
The positive electrode active material D in this example was obtained by testing 50 2.74 μm and BET 0.68m 2 And the maximum bearing value MA of the positive electrode active material is 80N, and the corresponding maximum strain X is 0.8, wherein MA and X meet MA/X=100.
(2) Preparation of a Battery
The preparation of the battery of this example was identical to that of example 1.
Example 8
(1) Preparation of positive electrode active material
S1, mixing lithium element, nickel element, cobalt element and manganese element according to a molar ratio of 1.05:0.33:0.33:0.33 lithium hydroxide monohydrate (LiOH-H) 2 O), nickel salt, cobalt salt, manganese salt, and dissolving them in water,
mixing uniformly to obtain a metal soluble salt solution, controlling the pH=11.1 of the system at a stirring rotation speed of 200rpm, stirring and reacting for 4 hours, and then dripping a citric acid solution into the solution, wherein the molar ratio of citric acid to lithium metal ions is 1:1, calculating the input amount of citric acid, and heating the obtained mixed solution at a constant temperature of 80 ℃ for 6 hours in a stirring state to form sol;
s2, transferring the sol to an electric furnace for heating, generating spontaneous combustion after about 5min to form fluffy substances, and grinding the fluffy substances to obtain a precursor mixture;
s3, calcining the precursor mixture in a muffle furnace according to the following procedure: heating to 500 ℃ firstly, preserving heat for 4h, then continuously heating to 850 ℃, preserving heat for 6h, cooling to 800 ℃, preserving heat for 5 h, and cooling to room temperature along with a furnace to obtain the granular positive electrode active material.
The positive electrode active material D in this example was obtained by testing 50 2.73 μm and BET 0.68m 2 And the maximum bearing value MA of the positive electrode active material is 40N, and the corresponding maximum strain X is 0.108, wherein MA and X meet MA/X=600.
(2) Preparation of a Battery
The preparation of the battery of this example was identical to that of example 1.
Example 9
(1) Preparation of positive electrode active material
S1, mixing lithium element, nickel element, cobalt element and manganese element according to a molar ratio of 1.05:0.33:0.33:0.33 lithium hydroxide monohydrate (LiOH-H) 2 O), nickel salt, cobalt salt and manganese salt, dissolving the nickel salt, cobalt salt and manganese salt in water, mixing uniformly to obtain a metal soluble salt solution, controlling the pH=13.1 of the system at a stirring rotation speed of 5000rpm, stirring and reacting for 8 hours, and then dripping a citric acid solution into the system, wherein the molar ratio of citric acid to lithium metal ions is 1:1, calculating the input amount of citric acid, and heating the obtained mixed solution at a constant temperature of 80 ℃ for 6 hours in a stirring state to form sol;
s2, transferring the sol to an electric furnace for heating, generating spontaneous combustion after about 5min to form fluffy substances, and grinding the fluffy substances to obtain a precursor mixture;
s3, calcining the precursor mixture in a muffle furnace according to the following procedure: heating to 500 ℃ firstly, preserving heat for 4h, then continuously heating to 850 ℃, preserving heat for 6h, cooling to 800 ℃, preserving heat for 5 h, and cooling to room temperature along with a furnace to obtain the granular positive electrode active material.
The positive electrode active material in this example was tested to be D 50 2.28 μm and BET 0.8m 2 And/g, and the maximum bearing value MA of the positive electrode active material is 70N, and the corresponding maximum strain X is 0.233, wherein MA and X meet MA/X=300.
(2) Preparation of a Battery
The preparation of the battery of this example was identical to that of example 1.
Example 10
(1) Preparation of positive electrode active material
S1, lithium element and cobalt element are mixed according to the molar ratio of Li: co=1.04, lithium salt and cobalt salt are weighed and dissolved in water, and are uniformly mixed to obtain a metal soluble salt solution, the pH=12.1 of the system is controlled at the stirring rotation speed of 1000rpm, after stirring reaction is carried out for 8 hours, precipitate obtained after reaction is washed and dried, wherein the drying temperature is controlled at 110 ℃, and metal salt hydroxide is obtained;
s2, mixing and grinding the metal salt hydroxide to obtain a precursor mixture;
s3, placing the precursor mixture into a muffle furnace, and calcining according to the following procedure: heating to 500 ℃ firstly, preserving heat for 3 h, then continuously heating to 850 ℃, preserving heat for 6h, cooling to 800 ℃, preserving heat for 12h, cooling to room temperature along with a furnace, and obtaining the granular positive electrode active material.
The positive electrode active material D in this example was obtained by testing 50 2.75 μm and BET 0.68m 2 And the maximum bearing value MA of the positive electrode active material is 40N, and the corresponding maximum strain X is 0.66, wherein MA and X meet MA/X=60.
(2) Preparation of a Battery
The preparation of the battery of this example was identical to that of example 1.
Example 11
(1) Preparation of positive electrode active material
S1, lithium element and manganese element are mixed according to the molar ratio of Li: mn=1.04, weighing lithium salt and manganese salt, dissolving the lithium salt and the manganese salt in water, mixing uniformly to obtain a metal soluble salt solution, controlling the pH=12.1 of the system at a stirring rotation speed of 2000rpm, stirring and reacting for 8 hours, and washing and drying a precipitate obtained after the reaction, wherein the drying temperature is controlled at 110 ℃ to obtain metal salt hydroxide;
s2, mixing and grinding the metal salt hydroxide to obtain a precursor mixture;
s3, placing the precursor mixture into a muffle furnace, and calcining according to the following procedure: heating to 500 ℃ firstly, preserving heat for 3 h, then continuously heating to 850 ℃, preserving heat for 6h, cooling to 800 ℃, preserving heat for 12h, cooling to room temperature along with a furnace, and obtaining the granular positive electrode active material.
The positive electrode active material D in this example was obtained by testing 50 2.75 μm and BET 0.68m 2 Per gram and positive electrode active materialThe maximum bearing value MA of the material is 40N, and the corresponding maximum strain X is 0.66, and MA and X satisfy MA/x=60.
(2) Preparation of a Battery
The preparation of the battery of this example was identical to that of example 1.
Comparative example 1
(1) Preparation of positive electrode active material
S1, weighing nickel salt, cobalt salt and manganese salt according to the molar ratio of 92:4:4, dissolving the nickel salt, the cobalt salt and the manganese salt in water, mixing uniformly to obtain a metal soluble salt solution, controlling the pH value of the system to be 12.1 under the condition that the stirring rotation speed is 350rpm, stirring and reacting for 8 hours, and washing and drying a precipitate obtained after the reaction, wherein the drying temperature is controlled at 110 ℃ to obtain metal salt hydroxide;
s2, according to Li: m is M Total (S) =1.04 LiOH-LiNO 3 Mixing and grinding molten salt and the metal salt hydroxide, wherein M Total (S) Adding the mole numbers of nickel, cobalt and manganese to obtain a precursor mixture;
s3, placing the precursor mixture into a muffle furnace, and calcining according to the following procedure: heating to 500 ℃ firstly, preserving heat for 6h, then continuously heating to 850 ℃, preserving heat for 10h, cooling to 800 ℃, preserving heat for 12h, cooling to room temperature along with a furnace, and obtaining the granular positive electrode active material.
Obtained by testing, the positive electrode active material D in this comparative example 50 2.98 μm and BET 0.6m 2 And the maximum bearing value MA of the positive electrode active material is 40N, and the corresponding maximum strain X is 0.8, wherein MA and X meet MA/X=50.
(2) Preparation of a Battery
The preparation of the cell of this comparative example was identical to that of example 1.
Comparative example 2
(1) Preparation of positive electrode active material
S1, weighing nickel salt, cobalt salt and manganese salt according to the molar ratio of 92:4:4, dissolving the nickel salt, the cobalt salt and the manganese salt in water, mixing uniformly to obtain a metal soluble salt solution, controlling the pH value of the system to be 12.1 under the condition that the stirring rotation speed is 300rpm, stirring and reacting for 8 hours, and washing and drying a precipitate obtained after the reaction, wherein the drying temperature is controlled at 110 ℃ to obtain metal salt hydroxide;
s2, according to Li: m is M Total (S) =1.04 LiOH-LiNO 3 Mixing and grinding molten salt and the metal salt hydroxide, wherein M Total (S) Adding the mole numbers of nickel, cobalt and manganese to obtain a precursor mixture;
s3, placing the precursor mixture into a muffle furnace, and calcining according to the following procedure: heating to 500 ℃ firstly, preserving heat for 3 h, then continuously heating to 950 ℃, preserving heat for 6h, then cooling to 800 ℃, preserving heat for 12h, and then cooling to room temperature along with furnace cooling to obtain the granular positive electrode active material.
Obtained by testing, the positive electrode active material D in this comparative example 50 2.28 μm and BET 1.0m 2 And/g, and the maximum bearing value MA of the positive electrode active material is 40N, and the corresponding maximum strain X is 0.044, wherein MA and X meet MA/X=900.
(2) Preparation of a Battery
The preparation of the cell of this comparative example was identical to that of example 1.
Test case
The batteries in examples 1 to 11 and comparative examples 1 to 2 were subjected to initial charge-discharge capacity and cyclic capacity retention rate tests in an experimental construction manner, and the specific test methods were as follows:
(1) Initial charge and discharge capacity test: placing the battery on a blue electric tester for charge and discharge test, wherein the test temperature is 25 ℃, standing the battery for 5 minutes, discharging the battery to 2.75V at 0.33 ℃, then charging the battery to 4.3V at a constant current with a rate of 0.33 (C), and charging the battery to 0.05C at a constant voltage, wherein the capacity obtained in the step is the initial charging capacity; the battery was charged to 4.3V at a constant current of 0.3 rate (C), charged to 0.05C at a constant voltage, and left to stand for 5 minutes, and discharged to 2.75V at 1C, whereby the capacity obtained in this step was taken as an initial discharge capacity.
(2) Cycle capacity retention test (200 times): performing charge and discharge test on the battery on a blue electric tester, wherein the test temperature is 60 ℃, charging the lithium ion battery to 4.3V at a constant current of 0.33 multiplying power (C), charging to 0.05C at a constant voltage, and discharging to 2.75V at 1C after standing for 5 minutes; then, a cycle test of 0.33C charge/1C discharge was performed 200 times, and the discharge capacity at the 200 th cycle was recorded. Cycle capacity retention= (discharge capacity of 200 th cycle/discharge capacity of first cycle) ×100%.
Experimental results table 1 structural characteristics of the test case reference object and statistics of electrochemical performance test results
| MA | X | MA/X | D50（μm） | Specific surface area (m 2/g) | First charge and discharge capacity (mAh/g) | Cycle Capacity retention, HT200cls (%) | |
| Example 1 | 40 | 0.66 | 60 | 2.75 | 0.68 | Charging 245.8 and discharging 216.3 | 92.6% |
| Example 2 | 50 | 0.125 | 400 | 2.89 | 0.62 | Fill 246.6 put 217.5 | 94.4% |
| Example 3 | 60 | 0.075 | 800 | 2.78 | 0.65 | Charge 246.2 and discharge 216.6 | 92.2% |
| Example 4 | 45 | 0.45 | 100 | 2.71 | 0.68 | Put 217.7 by filling 246.5 | 94.1% |
| Example 5 | 45 | 0.128 | 350 | 2.76 | 0.68 | Put 217.9 by filling 246.8 | 94.6% |
| Example 6 | 40 | 0.108 | 600 | 2.73 | 0.68 | Fill 246.9 put 217.1 | 94.3% |
| Example 7 | 80 | 0.8 | 100 | 2.74 | 0.68 | Fill 240.9 put 211.1 | 90% |
| Example 8 | 40 | 0.66 | 60 | 0.6 | 2.2 | Charging 244.9 and discharging 216.1 | 90.1% |
| Example 9 | 40 | 0.66 | 60 | 12 | 0.11 | Fill 245.2 put 215.8 | 89.3 |
| Example 10 | 40 | 0.57 | 70 | 2.72 | 0.65 | Charging 220.8 and discharging 200.5 | 92.6% |
| Example 11 | 40 | 0.47 | 85 | 2.86 | 0.61 | Fill 220.5 put 200.1 | 92.4% |
| Comparative example 1 | 40 | 0.8 | 50 | 2.98 | 0.6 | Fill 240.0 put 210.7 | 85.1% |
| Comparative example 2 | 40 | 0.044 | 900 | 2.28 | 1.0 | Fill 240.3 put 210.9 | 85.9% |
And classifying the reference lithium ion batteries of the test example by taking whether the positive electrode active material satisfies MA/X which is more than or equal to 60 and less than or equal to 800 as a classification basis to obtain examples 1-11 in which the positive electrode active material satisfies MA/X which is more than or equal to 60 and less than or equal to 800 and comparative examples 1 and 2 in which the positive electrode active material does not satisfy MA/X which is more than or equal to 60 and less than or equal to 800. The test results of this test example are shown in table 1, and the lithium ion batteries of examples 1 to 11 have higher high-temperature cycle retention and higher initial positive electrode charge capacity values than those of the lithium ion batteries of comparative examples 1 and 2. After the test is finished, the lithium ion battery to be tested is disassembled, and the observation shows that compared with the lithium ion battery of the embodiment 1-11 before the test is started, the positive electrode sheet basically has no obvious deformation or damage, the surface of the positive electrode active coating of the positive electrode sheet of the embodiment is kept smooth and flat, no obvious microcrack is formed, and the positive electrode sheets of the embodiment have good structural stability. The positive electrode sheets prepared in comparative examples 1 and 2, which are clearly different from examples 1 to 11, all show a certain number of obvious microcracks in the positive electrode active coating after the test, and electrolyte corrosion traces are found in the microcracks.
In the positive electrode active material adopted in comparative example 1, MA/X is less than or equal to 60, the positive electrode active material with the characteristics has weak compression resistance, microcracks are easy to generate even crystal breakage when the positive electrode active material is extruded, such as in the rolling processing process of a positive electrode plate, and the generation and the extension of the microcracks on the positive electrode active material are easy to be aggravated along with the continuous accumulation of cyclic stress in the charge-discharge cycle process of a battery, and the formation of the microcracks damages the structural stability of the positive electrode active material and is manifested as the deterioration of the cycle performance of a lithium ion battery. The generation of microcracks can increase the reaction interface between the positive electrode active material and the electrolyte, so that the side reaction degree between the positive electrode active material and the electrolyte is increased, and the internal resistance and capacity of the battery are increased.
In contrast, in the positive electrode active material adopted in comparative example 2, the MA/X is more than 800, the particles of the positive electrode active material are closely arranged, the internal porosity is too low, and the lithium ion transmission efficiency is low: on one hand, poor transmission dynamics performance of lithium ions is caused, and the deterioration of the rate performance of the battery is reflected; on the other hand, the accumulation of internal cycle stress of the positive electrode active material is similarly aggravated in the long-term charge-discharge cycle process, so that microcracks are generated on the surface of the positive electrode active material, the side reaction degree of the positive electrode active material and electrolyte is increased, and the degradation of the battery cycle performance is reflected. In addition, the internal arrangement of the positive electrode active material structure is too tight, which may cause the compressive capacity thereof to be too high, resulting in difficulty in processing in actual production.
And it can also be seen from the test data in table 1 that the first discharge capacity in the lithium ion batteries of comparative example 1 and comparative example 2 is significantly lower than that of examples 1 to 6. The reason is that the compression resistance of the particles determines the compaction density, if the compression resistance is too small, the compaction density is too small, the distance between the particles is increased, the ion channel is increased, the liquid absorption amount of the electrolyte is increased, and the rapid movement of lithium ions is facilitated; however, the contact probability and the contact area between particles are reduced due to overlarge inter-particle distance, so that electron transmission is not facilitated; and the decrease in conductivity increases polarization, resulting in an increase in internal resistance and a decrease in discharge capacity. If the pressure resistance is too high, the compaction density of particles is too high, the distance between particles is too high, the ion channel is reduced, the absorption amount of electrolyte is reduced, and the rapid transmission of lithium ions is not facilitated, so that the internal resistance is increased, and the discharge capacity is reduced.
According to the comparison analysis, in the process of preparing the positive plate in the embodiments 1-6, the positive electrode active material is controlled to meet MA/X which is less than or equal to 60 and less than or equal to 800, so that the compressive capacity and mechanical stability of the positive electrode active material can be effectively improved, the prepared positive plate has good structural stability, microcracks are not easy to generate, and on the other hand, the lithium ion transmission dynamics characteristic of the positive electrode active material is favorably optimized, and smooth transmission of lithium ions on the positive plate is promoted. Further, the electrochemical performance test results of the lithium ion batteries provided in examples 1 to 6 are compared, and the results show that the high-temperature cycle retention rate measured by the lithium ion batteries provided in examples 2, 4, 5 and 6 is higher, so that the lithium ion transmission characteristic and the battery cycle performance of the lithium ion batteries can be further improved by controlling the characteristics of the positive electrode active material which are more than or equal to 100 and less than or equal to 600.
Further, in examples 1 to 6 and example 7, the first charge/discharge capacity and the cycle capacity retention rate of the lithium ion battery in example 7 were slightly inferior. This is because the maximum strain X > 0.5 in the positive electrode active material of example 7, which is excessively large, represents an excessively large compressive capacity, causes an excessively large compaction density of the corresponding particles, an excessively large inter-particle distance, a reduced ion channel, is unfavorable for the absorption of electrolyte, deteriorates the transport of lithium ions, causes an increase in internal resistance and a decrease in charge-discharge capacity, and also deteriorates the cycle capacity retention rate of lithium ions.
Still further comparing examples 1 and 8, 9, the circulation capacity retention rates of examples 8, 9 were slightly lower. This is for examples 8, 9D respectively 50 Too small and too large results in too large and too small specific surface area, and the pressure bearing capacity and the surface electrolyte wettability of the positive electrode active material cannot be simultaneously considered, so that the cycle performance of the lithium battery is deteriorated.
In addition, as can be seen from examples 10 and 11, other positive electrode active materials such as lithium cobaltate and lithium manganate active materials were used, and the positive electrode active materials were controlled to satisfy the condition of 60.ltoreq.MA/X.ltoreq.800, and lithium ion batteries having high cycle retention and high initial charge/discharge capacity were also obtained.
The above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made to the technical solution of the present invention, but these modifications or substitutions are all within the scope of the present invention.
Claims (10)
1. The positive plate comprises a positive current collector and a positive active coating arranged on the surface of the positive current collector, wherein the positive active coating contains a positive active material and is characterized in that:
the positive electrode active material is granular, under the action of external pressure, the maximum bearing value of the positive electrode active material before rupture is MA, the maximum strain of the positive electrode active material before rupture is X, the unit of MA is N, and the positive electrode active material meets the requirement that MA/X is more than or equal to 60 and less than or equal to 800.
2. The positive electrode sheet according to claim 1, wherein: the positive electrode active material satisfies: MA/X is less than or equal to 100 and less than or equal to 600.
3. The positive electrode sheet according to claim 1, wherein: the positive electrode active material satisfies that X is more than 0 and less than or equal to 0.5.
4. The positive electrode sheet according to claim 1, wherein: d of the positive electrode active material 50 1 to 10 μm.
5. The positive electrode sheet according to claim 4, wherein: d of the positive electrode active material 50 Is 2 to 5 μm.
6. The positive electrode sheet according to claim 1, wherein: the specific surface area of the positive electrode active material is 0.2-3 m 2 /g。
7. The positive electrode sheet according to claim 6, wherein: the specific surface area of the positive electrode active material is 0.4-1 m 2 /g。
8. The positive electrode sheet according to claim 1, wherein: in the positive electrode active coating layer, the mass of the positive electrode active material is not less than 50% of the total mass of the positive electrode active coating layer.
9. The positive electrode sheet according to any one of claims 1 to 8, wherein: the positive electrode active material comprises at least one of a lithium cobaltate material, a lithium nickelate material, a lithium manganate material, a nickel cobalt manganese material, a nickel cobalt aluminum material, a lithium-rich manganese-based material and a lithium nickel manganate material.
10. A battery, characterized in that: comprising the positive electrode sheet, separator, negative electrode sheet, and electrolyte according to any one of claims 1 to 9.
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| CN116072854A (en) * | 2023-03-07 | 2023-05-05 | 中创新航科技集团股份有限公司 | Battery cell |
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