CN114759157A - Negative pole piece, preparation method thereof and lithium secondary battery - Google Patents
Negative pole piece, preparation method thereof and lithium secondary battery Download PDFInfo
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- CN114759157A CN114759157A CN202210469031.6A CN202210469031A CN114759157A CN 114759157 A CN114759157 A CN 114759157A CN 202210469031 A CN202210469031 A CN 202210469031A CN 114759157 A CN114759157 A CN 114759157A
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 74
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 74
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- 239000010439 graphite Substances 0.000 claims abstract description 175
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 169
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 166
- 239000011148 porous material Substances 0.000 claims abstract description 93
- 239000007773 negative electrode material Substances 0.000 claims abstract description 62
- 239000002245 particle Substances 0.000 claims abstract description 48
- 238000000034 method Methods 0.000 claims description 22
- 239000003792 electrolyte Substances 0.000 claims description 16
- 239000011267 electrode slurry Substances 0.000 claims description 15
- 238000005087 graphitization Methods 0.000 claims description 8
- 239000012528 membrane Substances 0.000 claims description 8
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- 238000001035 drying Methods 0.000 claims description 6
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 5
- 239000011889 copper foil Substances 0.000 claims description 5
- 238000002156 mixing Methods 0.000 claims description 5
- 238000003825 pressing Methods 0.000 claims description 5
- 229910021383 artificial graphite Inorganic materials 0.000 claims description 4
- 239000002210 silicon-based material Substances 0.000 claims description 4
- 239000002904 solvent Substances 0.000 claims description 4
- 239000011366 tin-based material Substances 0.000 claims description 4
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 3
- 239000006256 anode slurry Substances 0.000 claims description 3
- 239000004917 carbon fiber Substances 0.000 claims description 3
- 239000006257 cathode slurry Substances 0.000 claims description 3
- 229910021385 hard carbon Inorganic materials 0.000 claims description 3
- 239000002931 mesocarbon microbead Substances 0.000 claims description 3
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- 239000011149 active material Substances 0.000 abstract 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 41
- 229910001416 lithium ion Inorganic materials 0.000 description 41
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- 238000007086 side reaction Methods 0.000 description 5
- QMGYPNKICQJHLN-UHFFFAOYSA-M Carboxymethylcellulose cellulose carboxymethyl ether Chemical compound [Na+].CC([O-])=O.OCC(O)C(O)C(O)C(O)C=O QMGYPNKICQJHLN-UHFFFAOYSA-M 0.000 description 4
- 239000003292 glue Substances 0.000 description 4
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- 229910052757 nitrogen Inorganic materials 0.000 description 3
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- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- 241001149900 Fusconaia subrotunda Species 0.000 description 1
- 229910013872 LiPF Inorganic materials 0.000 description 1
- 101150058243 Lipf gene Proteins 0.000 description 1
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- 239000004698 Polyethylene Substances 0.000 description 1
- 241001116459 Sequoia Species 0.000 description 1
- 229910000676 Si alloy Inorganic materials 0.000 description 1
- 229910001128 Sn alloy Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 description 1
- OBNDGIHQAIXEAO-UHFFFAOYSA-N [O].[Si] Chemical compound [O].[Si] OBNDGIHQAIXEAO-UHFFFAOYSA-N 0.000 description 1
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- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
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- 239000011888 foil Substances 0.000 description 1
- 238000009775 high-speed stirring Methods 0.000 description 1
- 238000010813 internal standard method Methods 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- GBCAVSYHPPARHX-UHFFFAOYSA-M n'-cyclohexyl-n-[2-(4-methylmorpholin-4-ium-4-yl)ethyl]methanediimine;4-methylbenzenesulfonate Chemical compound CC1=CC=C(S([O-])(=O)=O)C=C1.C1CCCCC1N=C=NCC[N+]1(C)CCOCC1 GBCAVSYHPPARHX-UHFFFAOYSA-M 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
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- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
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- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000011863 silicon-based powder Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- QHGNHLZPVBIIPX-UHFFFAOYSA-N tin(ii) oxide Chemical compound [Sn]=O QHGNHLZPVBIIPX-UHFFFAOYSA-N 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
-
- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
-
- 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
-
- 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)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Secondary Cells (AREA)
Abstract
The application provides a negative pole piece, a preparation method thereof and a lithium secondary battery. This negative pole piece includes that the negative pole collects the body and sets up the negative pole diaphragm on negative pole current collection body a surface or two surfaces, and the negative pole diaphragm includes negative pole active material, and negative pole active material includes porous graphite, and this porous graphite satisfies: a x Dv of 0.9 or less50C is less than or equal to 4.3; wherein the average pore diameter of the surface pore canal of the porous graphite is A nm; the volume median particle diameter of the porous graphite is Dv50Mu m; the gram capacity of the porous graphite is C mAh/g. By reasonably adjusting the relation among the average pore diameter of the porous graphite surface pore canal, the gram capacity of the porous graphite and the average particle diameter in the negative active material, the lithium secondary battery is enabled to be compatible with the lithium secondary batteryAllowing for high energy density, long cycle life and fast charge performance.
Description
Technical Field
The application relates to the field of lithium secondary batteries, in particular to a negative pole piece, a preparation method of the negative pole piece and a lithium secondary battery.
Background
The lithium secondary battery has the outstanding characteristics of light weight, high energy density, no pollution, no memory effect, long service life and the like, and is widely applied to portable electronic equipment and new energy automobiles. However, a long charging time is one of the important factors limiting the rapid popularization of new energy automobiles, and from the technical principle, the negative electrode plate has a large influence on the rapid charging performance of the lithium secondary battery, and if the charging and discharging current is too large, part of lithium ions are directly reduced and precipitated on the surface of the negative electrode plate instead of being embedded into a negative electrode active material, so that the rapid charging performance of the secondary battery is poor.
Disclosure of Invention
The application mainly aims to provide a negative pole piece, a preparation method thereof and a lithium secondary battery, so as to solve the problem of poor quick charging performance of the lithium secondary battery in the prior art.
In order to achieve the above object, according to one aspect of the present application, there is provided a negative electrode sheet, including a negative electrode current collector and a negative electrode film disposed on one surface or both surfaces of the negative electrode current collector, wherein the negative electrode film includes a negative electrode active material, the negative electrode active material includes porous graphite, and the porous graphite satisfies:
0.9≤A×Dv50/C≤4.3；
wherein the average pore diameter of the surface pore canal of the porous graphite is A nm;
the volume median particle diameter of the porous graphite is Dv50μm；
The gram capacity of the porous graphite is C mAh/g.
Further, the porous graphite satisfies A x Dv of 1.5. ltoreq503.5,/C, preferably 2. ltoreq. A.times.dv50/C≤3。
Further, the average pore diameter of the surface pore canal of the porous graphite is 20-200 nm, preferably 20-100 nm, and further preferably 30-80 nm; and/or the volume median particle size of the porous graphite is 3-20 μm, preferably 5-18 μm, and further preferably 8-15 μm; and/or the gram capacity of the porous graphite is 340-365 mAh/g, preferably 350-360 mAh/g, and further preferably 353-358 mAh/g.
Further, the specific surface area of the porous graphite is 1-10 m2A ratio of 3 to 8 m/g is preferred2(iv)/g, more preferably 4 to 6m2/g。
Further, the graphitization degree of the porous graphite is 80-99%, preferably 90-99%, and more preferably 95-99%.
Further, the mass ratio of the negative active material in the negative membrane is 80-98%, and the preferred negative active material further comprises one or more of natural graphite, artificial graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials and lithium titanate.
Further, the compacted density PD of the negative electrode diaphragm is 1-2 g/cm3Preferably 1.2 to 1.8g/cm3More preferably 1.4 to 1.7g/cm3。
According to another aspect of the present application, there is provided a lithium secondary battery comprising a positive electrode plate, a negative electrode plate, an electrolyte and a separator, wherein the negative electrode plate is any one of the above negative electrode plates.
Further, the lithium secondary battery satisfies Dv of 0.5. ltoreq50/[VOI×(CB+1)]≤5；
Wherein, the OI value of the negative electrode diaphragm is VOI；
The capacity excess coefficient of the lithium secondary battery is CB;
preferably satisfies 1. ltoreq. Dv50/[VOI×(CB+1)]Less than or equal to 4, and more preferably satisfies the condition that Dv is less than or equal to 150/[VOI×(CB+1)]≤2。
Further, the OI value V of the negative electrode diaphragmOI1 to 20, preferably 1 to 15, more preferably 1 to 8; and/or the capacity excess coefficient CB of the lithium secondary battery is 1.0-2.0, preferably 1-1.5, more preferably 1.1-1.3.
According to another aspect of the present application, there is provided a method for preparing any one of the above negative electrode sheets, the method comprising: preparing cathode slurry; coating the negative electrode slurry on one surface or two surfaces of a copper foil of a negative current collector, and drying, cold pressing and slitting to obtain a negative electrode piece; the process for preparing the anode slurry comprises the following steps: selecting porous graphite according to the following relational expression I, and mixing a negative active material comprising the porous graphite with a conductive agent, a binder and a dispersion solvent to obtain negative slurry;
0.9≤A×Dv50a/C is less than or equal to 4.3 of the relational formula I
Wherein the average pore diameter of the surface pore canal of the porous graphite is A nm;
the volume median particle diameter of the porous graphite is Dv50μm；
The gram capacity of the porous graphite is C mAh/g;
the porous graphite is preferably selected according to the relation I-1:
1.5≤A×Dv50the/C is less than or equal to 3.5, the relation is shown as formula I-1,
the porous graphite is preferably selected according to the relation I-2:
2≤A×Dv50the/C is less than or equal to 3, and the relation is I-2.
By applying the technical scheme, the energy density, the quick charging performance and the cycle performance of the battery can be considered and improved. The inventors of the present application have found, through extensive studies, that the average pore diameter of the surface pores of the porous graphite in the negative electrode active material (also referred to as the average pore diameter a in the present application), and the volume median particle diameter of the porous graphite (also referred to as the volume median particle diameter Dv in the present application) are the average pore diameter of the pores on the surface of the porous graphite50) And the gram capacity of the porous graphite (also called gram capacity C in the application) influences the quick charging capacity and the service life of the battery, and the lithium secondary battery can achieve high energy density, long cycle life and quick charging performance by jointly controlling the relation among the average pore diameter of the pore passage on the surface of the porous graphite in the negative active material, the volume median particle diameter of the porous graphite and the gram capacity.
When the battery is designed, the provided negative active material contains porous graphite, the particle surface of the porous graphite is provided with a pore channel, lithium ions can be inserted into the graphite crystal through the pore channel, the dynamic performance of the lithium secondary battery is improved, the pore channel on the surface of the porous graphite can buffer the volume change of the porous graphite in the charging and discharging process, and the cycle performance of the lithium secondary battery is improved. In view of the above, the present application provides a lithium secondary battery with high energy density, long cycle life and fast charging performance by reasonably adjusting the relationship among the average pore size of the surface pore of the porous graphite in the negative active material, the volume median particle size of the porous graphite and the gram volume.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail with reference to examples.
Theoretically, in the process of charging the battery, the negative electrode plate needs to go through the following 3 electrochemical processes: (1) lithium ions are extracted from the anode material and enter the electrolyte, and liquid phase conduction is carried out inside the cathode porous electrode along with the electrolyte; (2) the lithium ions exchange charges on the surface of the negative active material; (3) the lithium ions are conducted in a solid phase inside the negative electrode active material particles.
The charge exchange of the lithium ions on the surface of the negative active material and the solid phase conduction in the negative active material particles have an important influence on the improvement of the quick charging performance of the battery, and the charge exchange of the lithium ions on the surface of the negative active material and the solid phase conduction in the material are closely related to the particle morphology and the particle structure of the negative active material.
In an exemplary embodiment of the present application, there is provided a negative electrode sheet, including a negative electrode current collector and a negative electrode film disposed on one surface or both surfaces of the negative electrode current collector, wherein the negative electrode film includes a negative electrode active material, the negative electrode active material includes porous graphite, and satisfies:
0.9≤A×Dv50/C≤4.3
wherein the average pore diameter of the surface pore canal of the porous graphite is A nm;
the volume median particle diameter of the porous graphite is Dv50μm；
The gram capacity of the porous graphite is C mAh/g.
The inventors of the present application found, through extensive studies, that the average pore diameter a of the surface pores of the porous graphite in the negative electrode active material and the volume-average particle size a of the porous graphiteDiameter Dv50And the gram capacity C of the porous graphite influences the quick charging capacity and the service life of the battery, and the energy density, the quick charging performance and the cycle performance of the battery can be improved by jointly controlling the average pore diameter of the porous graphite surface pore canal in the negative active material and the volume median particle size and the gram capacity of the porous graphite.
When the battery is designed, the provided negative active material contains porous graphite, the particle surface of the porous graphite is provided with a pore channel, lithium ions can be inserted into a graphite crystal through the pore channel, the dynamic performance of the lithium secondary battery is improved, the pore channel on the surface of the porous graphite can buffer the volume change of the porous graphite in the charging and discharging process, and the cycle performance of the lithium secondary battery is improved. In view of the above, the present application provides a lithium secondary battery with high energy density, long cycle life and fast charging performance by reasonably adjusting the relationship among the average pore diameter of the porous graphite surface pore channel, the gram capacity of the porous graphite and the volume median particle diameter in the negative active material.
The average pore diameter A of the porous graphite surface pore canal in the negative active material is too large or the volume median particle diameter Dv of the porous graphite50Too large or too small a gram volume C of the porous graphite results in A.times.dv50When the upper limit of the/C is more than 4.3, the comprehensive performance of the battery is poor. The average pore diameter A of porous graphite surface pore channels in the negative active material is too large, the specific surface area of the material is too high, and active sites on the surface of the material are too many, so that the side reaction between the material and electrolyte is increased, the impedance and capacity loss of the battery are improved, and the quick charge performance and the cycle performance of the battery are reduced; volume median diameter Dv of porous graphite in negative electrode active material50Too large, too long solid phase diffusion path of lithium ions in the porous graphite particles, poor dynamic performance of the battery, and unfavorable for rapid charge and discharge; if the gram capacity C of the porous graphite in the negative electrode active material is too small, the energy density of the battery is too low, and the battery performance is poor.
The average pore diameter A of the porous graphite surface pore canal in the negative active material is too small or the volume median particle diameter Dv of the porous graphite50Too small or too large a gram volume C of porous graphite results in A x Dv50When the lower limit of/C is less than 0.9, the battery healdThe resultant performance is poor. The reason is that the average pore size a of porous graphite surface pore channels in the negative active material is too small, which results in poor charge exchange of lithium ions on the surface of the porous graphite and poor solid phase conductivity in the porous graphite particles, poor dynamic performance of the battery, and is not favorable for rapid charge and discharge; volume median diameter Dv of porous graphite in negative electrode active material50When the size of the negative electrode diaphragm is too small, the structure of the negative electrode diaphragm is too compact, so that the penetration of electrolyte is not facilitated, the liquid phase diffusion capacity of lithium ions is reduced, the dynamic performance of the battery is poor, and the rapid charging and discharging cannot be carried out; the gram capacity C of the porous graphite in the negative active material is too large, which shows that the side reaction between the porous graphite and the electrolyte is less, the specific surface area of the material is smaller, the active sites on the surface of the material are less, the charge exchange of lithium ions on the surface of the material is not facilitated, the dynamic performance of the battery is poorer, and the battery cannot bear higher charge-discharge speed.
On the basis, the average pore diameter A of the pore canal on the surface of the porous graphite, the volume median diameter Dv50 of the porous graphite and the gram volume C form a mutual restriction relationship. Wherein, the average pore diameter A of the pore canal on the surface of the porous graphite and the volume median diameter Dv of the porous graphite50The dynamic performance and the electrochemical cycle performance of the porous graphite are affected together, the dynamic performance and the electrochemical cycle performance cannot be simultaneously too large or too small, and the gram capacity C of the porous graphite can directly affect the energy density of the lithium ion battery; through a great deal of research, the inventor finds that when the average pore diameter A, the volume median particle diameter Dv50 and the gram volume C of the porous graphite satisfy 0.9-4.3 of A multiplied by Dv50/C, the battery has better comprehensive performance, proper energy density, better dynamic performance and electrochemical cycle performance.
In order to better balance the relationship among the average pore diameter of the pore canal on the surface of the graphite, the gram volume and the volume median diameter of the porous graphite, in some preferred embodiments of the present application, the porous graphite satisfies A × Dv of not less than 1.550C3.5, more preferably porous graphite satisfying 2. ltoreq. A.times.dv50the/C is less than or equal to 3, so that the negative electrode has the characteristics of high energy density, excellent quick charge performance and long cycle life under high-rate charge and discharge.
Considering the charge exchange capacity of lithium ions on the surface of the negative active material, the larger the average pore diameter A of the pore channel on the surface of the negative active material particles is, the higher the specific surface area of the material is, the more active sites on the surface of the material are, the more charge exchange of the lithium ions on the surface of the material is facilitated, and the quick charge performance of the lithium ion battery can be improved; meanwhile, in consideration of the solid-phase conductivity of lithium ions in the negative active material, the larger the average pore diameter A of the pore channel on the surface of the negative active material particle is, the more the lithium ions can be favorably diffused into the material, and the solid-phase conductivity of the lithium ions in the material can be improved, so that the quick charging performance of the lithium ion battery is improved; in addition. As the average pore diameter a of the pore channels on the surface of the negative active material particles increases, the battery impedance increases and causes a certain capacity loss, thereby reducing the energy density of the battery. In some embodiments of the present application, an average pore diameter of surface pores of the porous graphite is 20 to 200nm, preferably 20 to 100nm, and further preferably 30 to 80nm, for example, an average pore diameter of surface pores of the porous graphite is 40nm, or 50nm, or 60nm, or 70nm, so as to prevent that when an average pore diameter of surface pores of the negative active material particles is too large, a specific surface area of the material is too high, active sites on a surface of the material are too many, which causes too many side reactions with an electrolyte, which increases impedance of the battery, and decreases a rapid charging performance of the battery, and at the same time, irreversible capacity loss is also caused, which affects a service life of the battery, and lithium ions have higher conductivity and energy density.
Volume median diameter Dv of porous graphite50Can influence the liquid phase diffusion of lithium ions in the negative electrode, Dv50The larger the size, the more favorable the liquid phase diffusion of lithium ions inside the negative electrode, but the larger the solid phase diffusion path of lithium ions inside the porous graphite particles. Volume median diameter Dv of porous graphite in negative electrode active material50The adhesion of the negative pole piece is small and easy to fall off, so that the electronic conductivity of the negative pole piece is influenced and the dynamic performance of the battery is poor; volume median diameter Dv of porous graphite in negative electrode active material50Too large, the negative pole slurry is easy to settle, the appearance of the pole piece is rough during coating, the excellent rate of the negative pole piece product is low, and the Dv is low50Too large will reduce the solid phase conductivity of the lithium ions in the graphite particles, and is not conducive to rapid charging and discharging of the battery. Thus, a suitable Dv50The overall performance of the battery can be effectively guaranteed, and in some embodiments of the present application, the volume median particle diameter Dv of the porous graphite50The particle size is 3-20 μm, preferably 5-18 μm, and more preferably 8-15 μm, so that the lithium battery has more comprehensive performance.
The larger the gram capacity C of the porous graphite is, the higher the battery energy density of the porous graphite is, and the smaller the specific surface area is, the fewer the active sites on the surface of the material are, resulting in less capacity loss due to side reactions with the electrolyte, but not favorable for the charge exchange of lithium ions on the surface of the material, resulting in poor quick charge performance of the battery. In some embodiments of the present application, the gram capacity of the porous graphite is 340 to 365mAh/g, preferably 350 to 360mAh/g, and more preferably 353 to 358mAh/g, so that the porous graphite is selected to achieve both the energy density and the fast charging performance of the battery.
The foregoing has mentioned the average pore diameter A of the surface pores of the porous graphite, and the volume median diameter Dv of the porous graphite50The gram volume C of the porous graphite is related to the specific surface area of the porous graphite, and besides, the morphology of the porous graphite particles and the surface defects of the particles also influence the specific surface area of the porous graphite; the larger the specific surface area of the porous graphite, the more favorable the charge exchange of lithium ions, and the larger the capacity loss due to side reactions with the electrolyte. In some embodiments of the present application, the porous graphite has a specific surface area of 1 to 10m2Preferably 3 to 8 m/g2(iv)/g, more preferably 4 to 6m2G, e.g. 4.5m2/g、5m2/g、5.5m2Per g, has better comprehensive performance.
The carbon atoms realize the conversion from a disordered layer structure to an ordered structure through graphitization, so the graphitization degree of the porous graphite also has great influence on the comprehensive performance of the lithium secondary battery, the higher the graphitization degree is, the higher the crystallinity degree of the porous graphite is, the more active sites in the particles for lithium ion deintercalation are, and the higher the capacity of the porous graphite is. In some embodiments of the present application, the graphitization degree of the porous graphite is 80-99%, preferably 90-99%, more preferably 95-99%, such as 96%, 97%, 98%.
In some embodiments, the mass proportion of the negative active material in the negative membrane is 80-98%. In some embodiments, the negative active material may include one or more of natural graphite, artificial graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, and lithium titanate, in which the content of the above materials may be referred to in the prior art, and in some embodiments, the mass ratio of the porous graphite in the negative membrane is 10 to 60%. Wherein, preferably, the silicon-based material can be selected from simple substance silicon, silicon oxygen compound, silicon carbon compound and silicon alloy, and the tin-based material can be selected from simple substance tin, tin oxygen compound and tin alloy. When one or a combination of the above materials is applied to the negative active material, the specific amount thereof can be referred to the prior art, and the details are not repeated herein.
The material composition of the negative electrode diaphragm of the present application can be selected from the prior art, for example, the negative electrode diaphragm further includes a conductive agent and a binder besides the negative electrode active material, and the kind and content of the conductive agent and the binder are not particularly limited and can be selected according to actual requirements. In some embodiments of the present application, the negative electrode film sheet has a compacted density PD of 1-2 g/cm3Preferably 1.2 to 1.8g/cm3More preferably 1.4 to 1.7g/cm3So that the negative electrode of the battery has better comprehensive performance and ensures enough energy density.
In the negative pole piece of this application, the negative pole mass flow body kind does not receive specific restriction, can follow prior art and select according to actual need, for example select for use the copper foil.
In another embodiment of the present application, a lithium secondary battery is provided, which includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator, wherein the negative electrode plate is any one of the above negative electrode plates.
When the lithium secondary battery is designed, the adopted negative active material contains porous graphite, the particle surface of the porous graphite is provided with a pore channel, lithium ions can be inserted into the graphite crystal through the pore channel, the dynamic performance of the lithium secondary battery is improved, the pore channel on the surface of the porous graphite can buffer the volume change of the porous graphite in the charging and discharging process, and the cycle performance of the lithium secondary battery is improved. In view of this, the present application provides a lithium secondary battery with high energy density, long cycle life and fast charging performance by reasonably adjusting the relationship among the average pore size of the surface pore channel of the porous graphite, the gram volume of the porous graphite and the volume median diameter of the porous graphite in the negative active material.
The types and the compositions of the positive pole piece, the electrolyte and the isolating membrane of the lithium secondary battery can be selected from the prior art according to actual requirements, and the application is not limited.
In some embodiments of the present application, the lithium secondary battery further satisfies 0.5 ≦ Dv50/[VOI×(CB+1)]≤5；
Wherein, the OI value of the negative electrode diaphragm is VOI；
The capacity excess coefficient of the lithium secondary battery is CB.
When the volume median diameter Dv of the porous graphite in the negative electrode active material is50OI value V of too small or negative diaphragmOIThe Dv caused by the excessive battery capacity coefficient CB50/[VOI×(CB+1)]When the content is less than 0.5, the comprehensive performance of the battery is not obviously improved; volume median diameter Dv of porous graphite in negative electrode active material50OI value V of oversized or negative diaphragmOIToo small or too small battery capacity excess coefficient CB leads to Dv50/[VOI×(CB+1)]When the upper limit of (2) is more than 5, the improvement of the overall battery performance is not significant. In some preferred embodiments of the present application, the lithium secondary battery satisfies 1 ≦ Dv50/[VOI×(CB+1)]Less than or equal to 4, and more preferably satisfies the condition that Dv is less than or equal to 150/[VOI×(CB+1)]≤2。
Wherein, the OI value V of the negative diaphragmOINeither too large nor too small is necessary because of the OI value V of the negative electrode diaphragmOIWhen the size is too small, the negative active materials tend to be arranged in a mixed and disorderly manner, and lithium ions can be removed from the negative pole pieceThe embedded effective end faces are more, but the negative pole piece has poor adhesive force and is easy to fall off powder, so that the structural stability of the negative pole piece is poor in the circulating process, and the battery capacity is easy to jump when circulating; OI value V of negative electrode diaphragmOIAnd when the size of the negative electrode active substance is too large, the negative electrode active substance tends to be arranged parallel to a negative electrode current collector, the effective end face for lithium ion deintercalation in a negative electrode pole piece is less, the dynamic performance of the battery is influenced, and the charge and discharge efficiency is influenced. In some embodiments of the present application, the negative diaphragm has an OI value of VOI1 to 20, preferably 1 to 15, more preferably 1 to 8.
The capacity excess coefficient CB of the battery is the ratio of the negative electrode capacity to the positive electrode capacity under the same area, and the capacity can be tested according to the prior art method, for example, the positive electrode capacity and the negative electrode capacity can be obtained by assembling a positive electrode plate and a negative electrode plate with the same area and a lithium plate into a button battery respectively, and then testing the charging capacity by using a blue tester. In some embodiments of the present application, the capacity excess coefficient CB of the lithium secondary battery is 1.0 to 2.0, preferably 1 to 1.5, and more preferably 1.1 to 1.3.
The capacity excess coefficient CB of the lithium secondary battery is within an appropriate range, so that the performance of the lithium battery can be significantly improved. The battery capacity excess coefficient CB is too small, the negative electrode is in an excessively high SOC state under the full charge state of the battery, the negative electrode potential is too low easily caused by polarization in the large-rate charge and discharge process of the battery, and active lithium is easily reduced and separated out on the surface of the negative electrode, so that the cycle performance of the battery is reduced, and potential safety hazards are possibly caused; the battery capacity excess coefficient CB is too large, the content of the negative active substance is more, the negative pole piece is thicker, the liquid phase diffusion capacity of lithium ions in the negative pole piece is poorer, the battery is not favorable for quick charge and discharge, the utilization rate of the negative active substance is lower when the battery is fully charged, and the energy density of the battery is reduced.
In another embodiment of the present application, there is provided a method for preparing a negative electrode sheet, the method comprising: preparing cathode slurry; coating the negative electrode slurry on one surface or two surfaces of a copper foil of a negative current collector, and drying, cold pressing and slitting to obtain a negative electrode piece; the process for preparing the anode slurry comprises the following steps: selecting porous graphite according to the following relational expression I, and mixing a negative electrode active material comprising the porous graphite with a conductive agent, a binder and a dispersing solvent to obtain negative electrode slurry;
0.9≤A×Dv50a/C is less than or equal to 4.3 of the relational formula I
Wherein the average pore diameter of the surface pore canal of the porous graphite is A nm;
the volume median particle diameter of the porous graphite is Dv50μm；
The gram capacity of the porous graphite is C mAh/g;
the porous graphite is preferably selected according to the relationship I-1:
1.5≤A×Dv50the/C is less than or equal to 3.5 of the relational expression I-1
The porous graphite is preferably selected according to the relation I-2:
2≤A×Dv50the/C is less than or equal to 3 and is expressed as the relation I-2
When the lithium secondary battery is prepared by the method, the adopted negative active material comprises porous graphite, the particle surface of the porous graphite is provided with the pore channels, lithium ions can be inserted into the graphite crystal through the pore channels, the dynamic performance of the lithium secondary battery is improved, the pore channels on the surface of the porous graphite can buffer the volume change of the porous graphite in the charging and discharging process, and the cycle performance of the lithium secondary battery is improved. In view of the above, the present application selects porous graphite in the negative active material according to the above relational expression, and makes the lithium secondary battery have high energy density, long cycle life, and fast charging performance by using the relationship among the average pore diameter of the surface pore channels, the gram capacity of the porous graphite, and the volume median diameter.
The specific preparation method of the negative electrode slurry can be selected from the prior art, and the application is not limited, and in some embodiments of the application, the negative electrode slurry is prepared by the following method: adding deionized water, conductive carbon black and 70% of CMC powder into a stirring tank, and stirring at a low speed for 2 hours to form a conductive glue solution; adding porous graphite into the conductive glue solution, stirring at a low viscosity and a high speed for 1h to form a first mixed solution; adding xanthan gum, high viscosity and high-speed stirring for 1h into the first mixed solution to form a second mixed solution; adding ethanol and the residual 30% of CMC powder into the second mixed solution, stirring at a low viscosity and a high speed for 2 hours to prepare negative electrode slurry.
The advantageous effects that can be achieved by the present application will be further described below with reference to examples and comparative examples.
The lithium secondary batteries of examples and comparative examples were each prepared as follows.
(1) Preparation of positive pole piece
Mixing a positive electrode active substance NCM811, a conductive agent carbon nano tube and a binder PVDF according to a mass ratio of 94:3:4, adding a solvent NMP, and uniformly stirring the mixture to obtain positive electrode slurry; and uniformly coating the positive electrode slurry on two sides of the positive electrode current collector aluminum foil, drying in an oven, and then performing cold pressing and slitting to obtain the positive electrode piece.
(2) Preparation of negative pole piece
Firstly, preparing negative electrode slurry, wherein the proportion of negative electrode active substances, conductive carbon black, CMC and xanthan gum in the negative electrode slurry is 93:1.5:1.5:4, the solid content is 50%, and the specific preparation method of the negative electrode slurry comprises the following steps: adding deionized water, conductive carbon black and 70% of CMC powder into a stirring tank, and stirring at a low speed for 2 hours to form a conductive glue solution; adding a negative electrode active substance into the conductive glue solution, stirring at a low viscosity and a high speed for 1h to form a first mixed solution; adding xanthan gum into the first mixed solution, stirring at high viscosity for 1h to form a second mixed solution; adding ethanol and the rest 30% CMC powder into the second mixed solution, stirring at a low viscosity and a high speed for 2 hours to prepare negative electrode slurry, wherein the ratio of the deionized water to the ethanol in the slurry is 9: 1. The specific composition of the negative active material in each example and comparative example is shown in table 1, wherein the artificial graphite is selected from sequoia jezoensis SS 1-P15; and uniformly coating the negative electrode slurry on two sides of the copper foil of the negative current collector, drying in an oven, and then performing cold pressing and slitting to obtain the negative electrode pole piece.
(3) Preparation of the electrolyte
Adding ethylene carbonate(EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an organic solvent, followed by mixing a sufficiently dried lithium salt LiPF at a concentration of 1mol/L6Dissolving the electrolyte in the mixed organic solvent, and fully dissolving to obtain the electrolyte.
(4) Preparation of the separator
Polyethylene film was chosen as the release film.
(5) Preparation of lithium secondary battery
Stacking the positive pole piece, the isolating film and the negative pole piece in sequence to enable the isolating film to be positioned between the positive pole piece and the negative pole piece to play an isolating role, 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 processes to obtain the lithium secondary battery.
Next, the method for testing the performance of the lithium secondary batteries in examples and comparative examples will be described.
(1) And (3) testing the dynamic performance: at 25 ℃, fully charging the lithium secondary batteries prepared in the examples and the comparative examples at a 4C multiplying power, fully discharging the lithium secondary batteries at a 1C multiplying power, repeating for 10 times, fully charging the lithium secondary batteries at a 4C multiplying power, disassembling a negative pole piece, and observing the lithium precipitation condition on the surface of the negative pole piece. Wherein, the area of the lithium separating region on the surface of the negative pole piece is less than 5 percent and is considered to be slightly lithium separating, the area of the lithium separating region on the surface of the negative pole piece is 5 to 40 percent and is considered to be moderately lithium separating, and the area of the lithium separating region on the surface of the negative pole piece is more than 40 percent and is considered to be severely lithium separating.
(2) And (3) testing the cycle performance: the lithium secondary batteries prepared in examples and comparative examples were charged at a rate of 2C and discharged at a rate of 1C at 25C, and full charge discharge cycle tests were performed until the capacity of the lithium secondary battery had decayed to 80% of the initial capacity, and the number of cycles was recorded.
(3) Actual energy density test: fully charging the lithium ion batteries prepared in the examples and the comparative examples at a rate of 1C and fully discharging the lithium ion batteries at a rate of 1C at 25 ℃, and recording the actual discharge energy at the moment; weighing the lithium ion battery at 25 ℃ by using an electronic balance; the ratio of the actual discharge energy of the lithium ion battery 1C to the weight of the lithium ion battery is the actual energy density of the lithium ion battery. Wherein, when the actual energy density is less than 80% of the target energy density, the actual energy density of the battery is considered to be very low; when the actual energy density is greater than or equal to 80% of the target energy density and less than 95% of the target energy density, the actual energy density of the battery is considered to be low; when the actual energy density is greater than or equal to 95% of the target energy density and less than 105% of the target energy density, the actual energy density of the battery is considered to be moderate; when the actual energy density is not less than 105% of the target energy density and less than 120% of the target energy density, the actual energy density of the battery is considered to be high; when the actual energy density is 120% or more of the target energy density, the actual energy density of the battery is considered to be very high.
(4) Testing the average pore diameter A of the pore channels on the surface of the porous graphite: the adsorption capacity and the adsorption-desorption isotherm at each partial pressure point were determined by introducing and evacuating gas into a sample tube in a liquid nitrogen environment, using a nitrogen adsorption micropore size analyzer (3H-2000PM 1). And then calculating by using BJH theory to obtain the aperture parameter.
(5) Volume median diameter Dv of porous graphite50: the method is characterized in that sample particles are dispersed in a liquid medium at a concentration of 200-300 mg/L by using a laser diffraction particle size analyzer (MS2000), and a monochromatic light beam (usually laser) is passed through the sample particles. After the light is scattered by the particles and distributed over different angles, a regular multi-component detector receives values for the scatter pattern at many angles and records these values for analysis. And calculating the scattering numerical value by using a Rayleigh scattering formula to obtain the ratio of the volume of the particles of each granularity level to the total volume, thereby obtaining the volume distribution of the granularity.
(6) Gram volume of porous graphite C: after a negative pole piece is prepared by taking porous graphite as a negative active material, the negative pole piece and a lithium piece are assembled together to form a button cell, and then a blue tester (CT2001A) is used for testing the charging capacity to obtain the lithium ion battery.
(7) OI value V of negative electrode diaphragmOI: obtained by using an X-ray powder diffractometer (X' pert PRO), and obtained according to X-ray diffraction analysis method general rules and graphite lattice parameter measurement methods JIS K0131-Spectrogram according to formula VOIAnd calculating the OI value of the negative electrode membrane sheet as C004/C110, wherein C004 is the peak area of the 004 characteristic diffraction peak, and C110 is the peak area of the 110 characteristic diffraction peak.
(8) Capacity excess coefficient CB of battery: the positive electrode capacity and the negative electrode capacity can be obtained by assembling a positive electrode plate and a negative electrode plate with the same area and a lithium plate into a button cell respectively and testing the charging capacity by using a blue light tester (CT 2001A).
(9) Specific surface area of porous graphite: the method is obtained by using a specific surface area tester (V-Sorb 2800S), porous graphite powder is filled in a U-shaped sample tube, the sample tube is placed in a liquid nitrogen environment, adsorbate gas is injected into the sample tube, the adsorption amount of a sample to be tested on adsorption analysis is determined according to the pressure or weight change before and after adsorption, and the specific surface area of the sample is calculated by using a BET adsorption isotherm equation.
(10) Graphitization degree of porous graphite: the porous graphite powder was mixed with standard silicon powder at a ratio of 1:2 and tested using a bench top X-ray diffractometer (Aeris). And testing the crystal faces of C002 and Si 111 or the crystal faces of C004 and Si 311 by an internal standard method to obtain the corrected angle data of the crystal faces of C002 or Si 111, obtaining the crystal face spacing d by utilizing a Bragg equation, and calculating the graphitization degree by utilizing a Franklin equation.
(11) Compacted density PD of the negative electrode film: weighing the negative pole piece with the area A, recording the mass of the negative pole piece as M, weighing the negative pole current collector with the same area, and recording the mass of the negative pole current collector as M. And measuring the thickness of the negative pole piece as D and the thickness of the negative pole current collector as D, and calculating the compaction density of the negative pole diaphragm according to the PD ═ (M-M)/[ A x (D-D) ].
Tables 1 and 2 below show parameters and test results of examples 1 to 37 and comparative examples 1 to 3 of the present application.
TABLE 1
TABLE 2
As can be seen from the examples and comparative examples, when the average pore diameter A of the porous graphite and the volume median diameter Dv of the porous graphite are set50And the gram volume C of the porous graphite satisfies A x Dv50When the value range is represented by/C, the energy density of the lithium battery is relatively proper, and the dynamic performance and the cycle performance are relatively good. While A.times.dv of the porous graphite in the comparative example50When the value of/C is less than 0.9 or more than 4.3, relatively serious lithium precipitation occurs and the cycle performance is not good, even if the average pore diameter A of the porous graphite and the volume median diameter Dv of the porous graphite are50And the gram volume C of the porous graphite is respectively in the proper value range mentioned in the text, but not satisfying A multiplied by Dv of 0.9 or more50When the/C is less than or equal to 4.3, the performance of the battery is not ideal.
From the above description, it can be seen that the average pore diameter a of the surface pores of the porous graphite in the negative electrode material, and the volume median diameter Dv of the porous graphite50And the gram capacity C of the porous graphite influences the quick charging capacity and the service life of the battery, and the energy density, the quick charging performance and the cycle performance of the battery can be improved by jointly controlling the average pore diameter of the porous graphite surface pore passage in the negative electrode material and the volume median particle size and the gram capacity of the porous graphite.
When the battery is designed, the provided negative active material contains porous graphite, the particle surface of the porous graphite is provided with a pore channel, lithium ions can be inserted into the graphite crystal through the pore channel, the dynamic performance of the lithium secondary battery is improved, the pore channel on the surface of the porous graphite can buffer the volume change of the porous graphite in the charging and discharging process, and the cycle performance of the lithium secondary battery is improved. In view of this, the present application provides a lithium secondary battery with high energy density, long cycle life and fast charging performance by reasonably adjusting the relationship among the average pore size of the surface pore channel of the porous graphite, the gram volume of the porous graphite and the volume median diameter of the porous graphite in the negative active material.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (11)
1. The utility model provides a negative pole piece, its characterized in that, negative pole piece includes the negative current collector and sets up the negative diaphragm on negative current collector one surface or two surfaces, the negative diaphragm includes negative active material, negative active material includes porous graphite, just porous graphite satisfies:
0.9≤A×Dv50/C≤4.3；
wherein the average pore diameter of the surface pore canal of the porous graphite is A nm;
the volume median particle diameter of the porous graphite is Dv50μm；
The gram capacity of the porous graphite is C mAh/g.
2. The negative electrode sheet according to claim 1, wherein the porous graphite satisfies A x Dv of 1.5. ltoreq.503.5,/C, preferably 2. ltoreq. A.times.dv50/C≤3。
3. The negative electrode plate as claimed in claim 1 or 2, wherein the average pore diameter of the surface pore canal of the porous graphite is 20-200 nm, preferably 20-100 nm, and more preferably 30-80 nm;
and/or the volume median particle size of the porous graphite is 3-20 μm, preferably 5-18 μm, and further preferably 8-15 μm;
and/or the gram capacity of the porous graphite is 340-365 mAh/g, preferably 350-360 mAh/g, and further preferably 353-358 mAh/g.
4. The negative electrode plate as claimed in claim 1 or 2, wherein the specific surface area of the porous graphite is 1-10 m2Preferably 3 to 8 m/g2(iv)/g, more preferably 4 to 6m2/g。
5. The negative electrode plate according to claim 1 or 2, wherein the graphitization degree of the porous graphite is 80-99%, preferably 90-99%, more preferably 95-99%.
6. The negative electrode plate of claim 1, wherein the negative electrode active material is 80-98% of the negative electrode membrane by mass, and preferably the negative electrode active material further comprises one or more of natural graphite, artificial graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, a silicon-based material, a tin-based material and lithium titanate.
7. The negative electrode plate as claimed in claim 1, wherein the compacted density PD of the negative electrode film is 1-2 g/cm3Preferably 1.2 to 1.8g/cm3More preferably 1.4 to 1.7g/cm3。
8. A lithium secondary battery comprises a positive pole piece, a negative pole piece, electrolyte and an isolating film, and is characterized in that the negative pole piece is the negative pole piece in any one of claims 1 to 7.
9. The lithium secondary battery according to claim 8, wherein the lithium secondary battery further satisfies 0.5 ≦ Dv50/[VOI×(CB+1)]≤5；
Wherein the negative electrodeThe OI value of the membrane is VOI；
The capacity excess coefficient of the lithium secondary battery is CB;
preferably satisfies 1. ltoreq. Dv50/[VOI×(CB+1)]Less than or equal to 4, and more preferably satisfies the condition that Dv is less than or equal to 150/[VOI×(CB+1)]≤2。
10. The lithium secondary battery as claimed in claim 9, wherein the negative electrode membrane has an OI value VOI1 to 20, preferably 1 to 15, more preferably 1 to 8;
and/or the capacity excess coefficient CB of the lithium secondary battery is 1.0-2.0, preferably 1-1.5, more preferably 1.1-1.3.
11. The preparation method of the negative electrode plate of any one of claims 1 to 7, characterized by comprising the following steps:
preparing cathode slurry;
coating the negative electrode slurry on one surface or two surfaces of a copper foil of a negative current collector, and drying, cold pressing and slitting to obtain a negative electrode piece;
wherein the process of preparing the anode slurry comprises the following steps:
selecting porous graphite according to the following relational expression I, and mixing a negative electrode active material comprising the porous graphite with a conductive agent, a binder and a dispersion solvent to obtain negative electrode slurry;
0.9≤A×Dv50a/C is less than or equal to 4.3 of the relational formula I
Wherein the average pore diameter of the surface pore canal of the porous graphite is A nm;
the volume median particle diameter of the porous graphite is Dv50μm；
The gram capacity of the porous graphite is C mAh/g;
the porous graphite is preferably selected according to the relationship I-1:
1.5≤A×Dv50the/C is less than or equal to 3.5, the relation is I-1,
the porous graphite is preferably selected according to the relationship I-2:
2≤A×Dv50the/C is less than or equal to 3, and the relation is shown as formula I-2.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115621532A (en) * | 2022-10-27 | 2023-01-17 | 欣旺达电动汽车电池有限公司 | Secondary battery and power consumption device |
| WO2024020927A1 (en) * | 2022-07-28 | 2024-02-01 | 宁德时代新能源科技股份有限公司 | Secondary battery and preparation method therefor, and electric device |
| WO2024077607A1 (en) * | 2022-10-14 | 2024-04-18 | 宁德时代新能源科技股份有限公司 | Negative electrode active material and preparation method therefor, and secondary battery and electrical device containing negative electrode active material |
| WO2024108562A1 (en) * | 2022-11-25 | 2024-05-30 | 宁德时代新能源科技股份有限公司 | Secondary battery and electrical device |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109962236A (en) * | 2018-04-28 | 2019-07-02 | 宁德时代新能源科技股份有限公司 | Secondary battery |
| CN111668452A (en) * | 2019-03-06 | 2020-09-15 | 宁德时代新能源科技股份有限公司 | Negative electrode and lithium ion secondary battery thereof |
| CN113207314A (en) * | 2019-12-03 | 2021-08-03 | 宁德时代新能源科技股份有限公司 | Secondary battery, device, artificial graphite and preparation method |
| CN113644241A (en) * | 2021-07-15 | 2021-11-12 | 恒大新能源技术(深圳)有限公司 | Composite graphite negative electrode material, preparation method thereof and secondary battery |
| US20220052341A1 (en) * | 2019-12-04 | 2022-02-17 | Contemporary Amperex Technology Co., Limited | Secondary battery, and battery module, battery pack and apparatus comprising the same |
-
2022
- 2022-04-29 CN CN202210469031.6A patent/CN114759157B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109962236A (en) * | 2018-04-28 | 2019-07-02 | 宁德时代新能源科技股份有限公司 | Secondary battery |
| CN111668452A (en) * | 2019-03-06 | 2020-09-15 | 宁德时代新能源科技股份有限公司 | Negative electrode and lithium ion secondary battery thereof |
| CN113207314A (en) * | 2019-12-03 | 2021-08-03 | 宁德时代新能源科技股份有限公司 | Secondary battery, device, artificial graphite and preparation method |
| US20210313575A1 (en) * | 2019-12-03 | 2021-10-07 | Contemporary Amperex Technology Co., Limited | Secondary battery, apparatus, artificial graphite and preparation method thereof |
| US20220052341A1 (en) * | 2019-12-04 | 2022-02-17 | Contemporary Amperex Technology Co., Limited | Secondary battery, and battery module, battery pack and apparatus comprising the same |
| CN113644241A (en) * | 2021-07-15 | 2021-11-12 | 恒大新能源技术(深圳)有限公司 | Composite graphite negative electrode material, preparation method thereof and secondary battery |
Non-Patent Citations (1)
| Title |
|---|
| 张鑫;雷维新;潘俊安;潘勇;罗振亚;: "粒径级配对石墨基负极材料电化学性能的影响", 电源技术 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2024020927A1 (en) * | 2022-07-28 | 2024-02-01 | 宁德时代新能源科技股份有限公司 | Secondary battery and preparation method therefor, and electric device |
| WO2024077607A1 (en) * | 2022-10-14 | 2024-04-18 | 宁德时代新能源科技股份有限公司 | Negative electrode active material and preparation method therefor, and secondary battery and electrical device containing negative electrode active material |
| CN115621532A (en) * | 2022-10-27 | 2023-01-17 | 欣旺达电动汽车电池有限公司 | Secondary battery and power consumption device |
| WO2024108562A1 (en) * | 2022-11-25 | 2024-05-30 | 宁德时代新能源科技股份有限公司 | Secondary battery and electrical device |
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| CN114759157B (en) | 2023-07-14 |
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