CN117936774A - Negative electrode active material, negative electrode plate containing same and lithium battery - Google Patents
Negative electrode active material, negative electrode plate containing same and lithium battery Download PDFInfo
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- CN117936774A CN117936774A CN202410058107.5A CN202410058107A CN117936774A CN 117936774 A CN117936774 A CN 117936774A CN 202410058107 A CN202410058107 A CN 202410058107A CN 117936774 A CN117936774 A CN 117936774A
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- 239000007773 negative electrode material Substances 0.000 title claims abstract description 52
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 29
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 29
- 229910021383 artificial graphite Inorganic materials 0.000 claims abstract description 142
- 239000011163 secondary particle Substances 0.000 claims abstract description 11
- 239000002245 particle Substances 0.000 claims description 62
- 239000002994 raw material Substances 0.000 claims description 32
- 239000011248 coating agent Substances 0.000 claims description 25
- 238000002156 mixing Methods 0.000 claims description 21
- 239000011265 semifinished product Substances 0.000 claims description 20
- 238000005087 graphitization Methods 0.000 claims description 18
- 238000009656 pre-carbonization Methods 0.000 claims description 18
- 239000011331 needle coke Substances 0.000 claims description 14
- 239000011230 binding agent Substances 0.000 claims description 12
- 239000003822 epoxy resin Substances 0.000 claims description 12
- 229920000647 polyepoxide Polymers 0.000 claims description 12
- 238000000576 coating method Methods 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 9
- 239000011247 coating layer Substances 0.000 claims description 7
- 230000008569 process Effects 0.000 claims description 5
- 239000006183 anode active material Substances 0.000 claims description 4
- 239000002243 precursor Substances 0.000 claims description 4
- 102220043159 rs587780996 Human genes 0.000 claims description 4
- 238000010000 carbonizing Methods 0.000 claims description 3
- 239000007791 liquid phase Substances 0.000 claims description 3
- 239000011164 primary particle Substances 0.000 claims description 3
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 claims description 2
- 239000011280 coal tar Substances 0.000 claims description 2
- 239000002609 medium Substances 0.000 claims description 2
- 239000005011 phenolic resin Substances 0.000 claims description 2
- 229920001568 phenolic resin Polymers 0.000 claims description 2
- 230000008901 benefit Effects 0.000 abstract description 10
- 125000004122 cyclic group Chemical group 0.000 abstract description 7
- 238000002441 X-ray diffraction Methods 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 29
- 238000010438 heat treatment Methods 0.000 description 25
- 239000000463 material Substances 0.000 description 20
- 239000010426 asphalt Substances 0.000 description 17
- 238000012360 testing method Methods 0.000 description 17
- 238000011112 process operation Methods 0.000 description 14
- 238000002360 preparation method Methods 0.000 description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 10
- 229910002804 graphite Inorganic materials 0.000 description 10
- 239000010439 graphite Substances 0.000 description 10
- 238000003763 carbonization Methods 0.000 description 9
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 8
- 229910001416 lithium ion Inorganic materials 0.000 description 8
- 239000000843 powder Substances 0.000 description 7
- 238000012216 screening Methods 0.000 description 7
- 238000007600 charging Methods 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 5
- 230000005540 biological transmission Effects 0.000 description 4
- 238000005056 compaction Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000011056 performance test Methods 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- 239000006256 anode slurry Substances 0.000 description 3
- 230000015556 catabolic process Effects 0.000 description 3
- 238000010280 constant potential charging Methods 0.000 description 3
- 238000010277 constant-current charging Methods 0.000 description 3
- 230000001351 cycling effect Effects 0.000 description 3
- 238000006731 degradation reaction Methods 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 230000002195 synergetic effect Effects 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 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
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 239000000571 coke Substances 0.000 description 2
- 239000011889 copper foil Substances 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 239000011229 interlayer Substances 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000007493 shaping process Methods 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000011267 electrode slurry Substances 0.000 description 1
- 239000003292 glue Substances 0.000 description 1
- 238000005469 granulation Methods 0.000 description 1
- 230000003179 granulation Effects 0.000 description 1
- 239000007770 graphite material Substances 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 230000037427 ion transport Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 239000002006 petroleum coke Substances 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- -1 polyethylene Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000007086 side reaction Methods 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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
-
- 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
-
- 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
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- 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
- H01M2004/027—Negative electrodes
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- 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)
- Inorganic Chemistry (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Carbon And Carbon Compounds (AREA)
Abstract
The invention provides a negative electrode active material, which comprises first artificial graphite, wherein the first artificial graphite is secondary particles, and the length-diameter ratio of the first artificial graphite is 1.5-2.0: 1, the grain diameter D50 of the first artificial graphite is 11-15 mu m, and the orientation degree OI value of the first artificial graphite is 2.0-2.5; the degree of orientation OI value is the ratio of the peak area of the 004 characteristic diffraction peak to the peak area of the 110 characteristic diffraction peak of the first artificial graphite in the XRD diffractogram. The invention can make the first artificial graphite have the advantages of high gram capacity and low cyclic expansion by simultaneously controlling the grain diameter, the length-diameter ratio and the orientation degree of the first artificial graphite, thereby making the lithium battery containing the first artificial graphite have excellent energy density and dynamic performance.
Description
Technical Field
The invention belongs to the technical field of lithium batteries, and particularly relates to a negative electrode active material, a negative electrode plate containing the negative electrode active material and a lithium battery.
Background
Graphite has excellent properties such as high capacity and high compaction, and is often used as a negative electrode material in the field of lithium ion batteries. However, in the process of charging and discharging the lithium ion battery, the volume expansion effect of graphite can occur, and the practical requirement of the power battery is difficult to meet. This is because lithium ions are intercalated and deintercalated in the negative electrode material during charge and discharge to change the interlayer structure of graphite, causing a series of problems such as increase of internal stress of a pole piece, rebound of the pole piece, and the like, and simultaneously, excessive SEI film is consumed at the interface of the interlayer structure of graphite, causing decomposition of electrolyte and reduction of active lithium ions, and causing degradation of battery cycle performance and capacity degradation. Accordingly, there is a need to develop a negative active material with low cyclic expansion, which overcomes the disadvantages of the prior art.
Disclosure of Invention
The invention aims to provide a negative electrode active material, a negative electrode plate and a lithium battery containing the negative electrode active material, wherein the negative electrode active material has the advantages of high gram capacity and low cycle expansion, and the lithium battery containing the negative electrode active material has excellent energy density and dynamic performance.
According to an aspect of the present invention, there is provided a negative electrode active material comprising a first artificial graphite, the first artificial graphite being secondary particles, the first artificial graphite having an aspect ratio of 1.5 to 2.0:1, the grain diameter D50 of the first artificial graphite is 11-15 mu m, and the orientation degree OI value of the first artificial graphite is 2.0-2.5; the degree of orientation OI value is the ratio of the peak area of the 004 characteristic diffraction peak to the peak area of the 110 characteristic diffraction peak of the first artificial graphite in the XRD diffractogram. In the negative electrode active material provided by the invention, the first artificial graphite is secondary particles with proper particle size and needle-like morphology, has proper specific surface area, can reduce side reaction of electrolyte on the surface of the secondary particles, reduces expansion of a pole piece in a circulating process, and meanwhile, the first artificial graphite has proper orientation degree OI value, can ensure isotropy of graphite particles, enables expansion generated by the graphite particles in a lithium intercalation process to be dispersed in all directions, slows down degradation of the negative electrode piece and battery performance caused by local uneven expansion, and can achieve higher compaction density after rolling based on the secondary particles, so that gram capacity of the negative electrode piece is improved. In summary, the particle size, the length-diameter ratio and the orientation degree of the first artificial graphite are controlled simultaneously, so that the first artificial graphite has the advantages of high gram capacity and low cyclic expansion, and the lithium battery containing the first artificial graphite has excellent energy density and dynamic performance.
If the orientation degree OI of the first artificial graphite is too high, isotropy of graphite particles is difficult to ensure, and the volume expansion of the graphite particles is large in the circulation process; if the degree of orientation OI of the first artificial graphite is too low, the graphite particles are arranged randomly, which is disadvantageous in terms of capacity.
Preferably, the preparation method of the first artificial graphite comprises the following operations: s1, taking needle coke as a raw material, mixing a binder with the raw material, and granulating to obtain a semi-finished product; s2, pre-carbonizing the semi-finished product to obtain a precursor; s3, graphitizing the precursor to obtain graphitized particles; s4, coating the graphitized particles by adopting a coating agent in a liquid phase and carbonizing the graphitized particles, thereby preparing the first artificial graphite. According to the preparation method, needle coke is used as a raw material, the needle coke has the performance advantages of high compaction and high capacity, and the prepared first artificial graphite can fully exert the high gram capacity advantage of the raw material and further improve the dynamic performance of the first artificial graphite through pre-carbonization, graphitization and liquid phase cladding carbonization treatment of the raw material.
Preferably, the temperature of the pre-carbonization is greater than or equal to 1000 ℃. The low-temperature pre-carbonization is performed before graphitization treatment, so that volatile matters can be removed, the subsequent graphitization effect is ensured, and the safety is improved.
Preferably, the binder comprises at least one of medium temperature asphalt, high temperature asphalt, epoxy resin.
Preferably, the granulation temperature is 850-950 ℃.
Preferably, the graphitization temperature is 2800 to 3200 ℃. The gram capacity of the artificial graphite particles is fully exerted by controlling the graphitization temperature.
Preferably, the carbonization temperature is not less than 900 ℃.
Preferably, the particle size of the needle coke is less than or equal to 8 mu m, and the tap density is more than or equal to 0.8g/cm 3. By further limiting the particle size and tap density of the needle coke, the kinetic properties of the first artificial graphite thus produced can be further improved while ensuring that the feedstock exhibits its high gram capacity advantage.
Preferably, the coating agent comprises at least two of epoxy resin, phenolic resin, medium temperature pitch and coal tar. The adoption of the coating agent for coating is favorable for improving the uniformity and compactness of the coating layer, and simultaneously is favorable for improving the defects on the surface of the coating layer and improving the structural stability and the circulation stability of the first artificial graphite.
Preferably, the method further comprises a second artificial graphite, wherein the mass ratio of the first artificial graphite to the second artificial graphite is 50-60: 40-50 percent; the second artificial graphite comprises artificial graphite A and artificial graphite B, wherein the artificial graphite A is primary particles, the particle size D50=8-10 mu m of the artificial graphite A is 91.5-93%, the artificial graphite B is secondary particles, the particle size D50=11-14 mu m of the artificial graphite B is 93-94%. The second artificial graphite is formed by mixing artificial graphite A and artificial graphite B, and has excellent quick charge performance and lithium ion dynamic transmission characteristics. The second artificial graphite and the first artificial graphite are mixed according to a specific proportion, and the two can fully play a synergistic effect, so that the prepared negative electrode active material has the advantages of the first artificial graphite and the second artificial graphite, and the quick charge performance and the lithium ion transmission dynamics characteristic of the negative electrode sheet can be further improved on the premise of ensuring the high gram capacity and the low cycle expansion advantage of the negative electrode sheet.
Preferably, the tap density of the artificial graphite A is 0.95-1.05 g/cm 3.
According to another aspect of the present invention, there is provided a negative electrode sheet including a negative electrode current collector and a negative electrode active coating layer provided on a surface of the negative electrode current collector, the negative electrode active coating layer including the above-described negative electrode active material.
Preferably, the surface density of the negative electrode active coating is equal to or more than 20m 2/g. Under the condition of lower surface density, the negative plate can keep high gram capacity, and meanwhile, can ensure higher ion and electron diffusion rate, so that the dynamic performance of the battery is further improved.
Preferably, the negative electrode active coating has a compacted density of 1.8g/cm 3 or more. By reasonably setting the compaction density of the anode active coating, anode active particles in the anode active coating are uniformly distributed, so that the stress expansion of the anode active particles is restrained, the conduction of electrons and the transmission of ions are promoted, and the dynamic characteristics of the anode active coating can be further improved on the basis of ensuring the high gram capacity of the anode sheet.
According to another aspect of the present invention, there is provided a lithium battery including the above-described negative electrode sheet. The battery provided by the invention has excellent energy density and dynamic performance.
Detailed Description
In order to make the technical solution of the present invention better understood by those skilled in the art, the technical solution of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
Example 1
The embodiment provides a lithium battery, and the preparation method thereof comprises the following steps:
1. Preparation of negative electrode sheet
S1, preparing first artificial graphite:
(1) Taking high-quality needle coke as a raw material; crushing and grading raw materials, mixing binder high-temperature asphalt and the raw materials according to the mass ratio of 20:100, and granulating in a granulating kettle (the granulating temperature is 850 ℃ C., the granulating time is 7 h) to obtain a semi-finished product;
(2) Heating the semi-finished product to 1000 ℃ for pre-carbonization treatment for 6 hours;
(3) Heating the powder obtained after pre-carbonization to 3200 ℃ for graphitization treatment to obtain graphitized particles C;
(4) Screening the graphitized particles C, and mixing a coating agent (epoxy resin and medium-temperature asphalt) with the graphitized particles C according to a ratio of 4:100 mass ratio, and then heating to 1200 ℃ for carbonization for 7 hours to prepare the first artificial graphite. Wherein the first artificial graphite is a secondary particle, and the aspect ratio of the first artificial graphite is 1.7:1, the particle diameter D50 was 13.5. Mu.m, and the degree of orientation OI of the first artificial graphite was 2.3.
S2, preparing second artificial graphite:
(1) Preparation of artificial graphite A: taking petroleum coke raw coke aggregate with the grain diameter D50 of 6 mu m and the true density of 2.3g/cm 3 as a raw material, heating the raw material to 3100 ℃ for graphitization treatment to obtain graphitized particles A; and mixing the coating agent epoxy resin with the graphitized particles A according to the mass ratio of 5:100 to coat the graphitized particles A, and then heating to 1200 ℃ to carbonize for 7h to obtain the artificial graphite A. Wherein the artificial graphite A is primary particles, the particle diameter D50 of the artificial graphite A is 9.5 mu m, the graphitization degree is 92%, and the tap density is 1.03g/cm 3.
(2) Preparation of artificial graphite B: taking calcined needle coke of oil system with the grain diameter D50 of 8 mu m and the tap density of 0.75g/cm 3 as a raw material, mixing medium-temperature asphalt serving as an auxiliary material binder with the raw material, and granulating in a granulating axe (the granulating temperature is 950 ℃ C., the granulating time is 7 h) to obtain a semi-finished product; heating the semi-finished product to 3150 ℃ for graphitizing treatment to obtain graphitized particles B; and mixing the coating agent epoxy resin with the graphitized particles B according to the mass ratio of 4.5:100 to coat the graphitized particles B, and then heating to 1000 ℃ to carbonize for 6 hours to prepare the artificial graphite B. Wherein the artificial graphite B is secondary particles, the particle size D50 of the artificial graphite B is 12.5 mu m, and the graphitization degree is 93%. Wherein the artificial graphite B is secondary particles, the particle size D50 of the artificial graphite B is 12.5 mu m, and the graphitization degree is 93%.
(3) And mixing the artificial graphite A and the artificial graphite B according to the mass ratio of 30:70 to obtain second artificial graphite.
S4, preparing a negative electrode active material:
and mixing the first artificial graphite and the second artificial graphite according to the mass ratio of 50:50 to obtain the negative electrode active material of the embodiment.
S5, preparation of negative plate
97.4% Of anode active material and 0.3% of conductive carbon black are uniformly mixed, then CMC glue solution (CMC content is 1.1%) is added into the mixture, and the mixture is stirred and uniformly mixed, then SBR1.2% is added into the mixture, and anode slurry is prepared. And then coating the negative electrode slurry on a copper foil, and drying the copper foil for 12 hours in a vacuum environment at 100 ℃ to obtain a negative electrode plate.
2. Preparation of positive plate
Uniformly mixing an anode active material (lithium cobaltate), a conductive agent SP and a binder PVDF according to the mass ratio of 94:3:3, dispersing the mixture in NMP to obtain anode slurry, coating the anode slurry on an aluminum foil, and drying the aluminum foil in a vacuum environment at 85 ℃ for 24 hours to obtain the anode plate.
3. Preparation of electrolyte
Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) are mixed according to a volume ratio of 1:1:1, and then dissolving fully dried lithium salt LiPF6 in the organic solvent to prepare an electrolyte with the concentration of 1 mol/L.
4. Selection of a diaphragm
The diaphragm adopts a polyethylene film.
5. Lithium battery assembly and formation
Sequentially stacking the positive plate, the diaphragm and the negative plate, enabling the diaphragm 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 (3) placing the bare cell in an outer packaging shell, drying, injecting the electrolyte, vacuum packaging, standing, forming and performing constant volume working procedure to obtain the lithium battery.
Example 2
This example makes a lithium battery with reference to example 1, which differs from example 1 in that: the negative electrode active material used in this example includes only the first artificial graphite. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
Example 3
This example makes a lithium battery with reference to example 1, which differs from example 1 in that: the mass ratio of the first artificial graphite to the second artificial graphite in the negative electrode active material used in this example was 40:60. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
Example 4
This example makes a lithium battery with reference to example 1, which differs from example 1 in that: the mass ratio of the first artificial graphite to the second artificial graphite in the negative electrode active material used in this example was 60:40. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
Example 5
This example makes a lithium battery with reference to example 1, which differs from example 1 in that: the mass ratio of the first artificial graphite to the second artificial graphite in the negative electrode active material used in this example was 70:30. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
Example 6
This example makes a lithium battery with reference to example 1, which differs from example 1 in that: the second artificial graphite in the negative electrode active material used in this example includes only artificial graphite a. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
Example 7
This example makes a lithium battery with reference to example 1, which differs from example 1 in that: the second artificial graphite in the negative electrode active material used in this example includes only artificial graphite B. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
Example 8
This example makes a lithium battery with reference to example 1, which differs from example 1 in that: the aspect ratio of the first artificial graphite in the negative electrode active material used in this example was 1.5:1, the particle diameter D50 was 11 μm, and the degree of orientation OI value was 2.0. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
The preparation method of the first artificial graphite comprises the following operations:
(1) Taking high-quality needle coke with a inlaid polarized light structure as a raw material; crushing and grading raw materials, enabling the particle size of aggregate to be 6-7 mu m, mixing binder high-temperature asphalt and the raw materials according to the mass ratio of 1:100, and granulating in a granulating kettle (the granulating temperature is 850 ℃ C., the granulating time is 7 h), so as to obtain a semi-finished product;
(2) Heating the semi-finished product to 1000 ℃ for pre-carbonization treatment for 6 hours;
(3) Heating the powder obtained after pre-carbonization to 3200 ℃ for graphitization treatment to obtain graphitized particles C;
(4) The graphitized particles C are subjected to screening treatment, and a coating agent (epoxy resin and medium-temperature asphalt) and the graphitized particles C are mixed according to a ratio of 5.5:100 mass ratio, and then heating to 1200 ℃ for carbonization for 7 hours to prepare the first artificial graphite.
Example 9
This example makes a lithium battery with reference to example 1, which differs from example 1 in that: the aspect ratio of the first artificial graphite in the negative electrode active material used in this example was 2.0:1, the particle diameter D50 was 15 μm, and the degree of orientation OI value was 2.5. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
The preparation method of the first artificial graphite comprises the following operations:
(1) Taking high-quality needle coke with a polarization structure rich in fibrous components as a raw material; crushing and grading raw materials, mixing binder high-temperature asphalt and the raw materials according to a mass ratio of 15.5:100, and granulating in a granulating kettle (the granulating temperature is 850 ℃ C., and the granulating time is 8 h) to obtain a semi-finished product;
(2) Heating the semi-finished product to 1000 ℃ for pre-carbonization treatment for 6 hours;
(3) Heating the powder obtained after pre-carbonization to 3100 ℃ for graphitization treatment to obtain graphitized particles C;
(4) The graphitized particles C are subjected to screening treatment, and a coating agent (epoxy resin and medium-temperature asphalt) and the graphitized particles C are mixed according to a ratio of 3.5:100 mass ratio, and then heating to 1200 ℃ for carbonization for 7 hours to prepare the first artificial graphite.
Comparative example 1
This comparative example a lithium battery was prepared with reference to example 1, and this comparative example was different from example 1 in that: the particle diameter D50 of the first artificial graphite in the negative electrode active material used in this example was 9.5 μm. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
Comparative example 2
This comparative example a lithium battery was prepared with reference to example 1, and this comparative example was different from example 1 in that: the particle diameter D50 of the first artificial graphite in the negative electrode active material used in this example was 16.5 μm. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
Comparative example 3
This comparative example a lithium battery was prepared with reference to example 1, and this comparative example was different from example 1 in that: the aspect ratio of the first artificial graphite in the negative electrode active material used in this example was 1.3:1, and the particle diameter d50=14 μm. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
The preparation method of the first artificial graphite comprises the following operations:
(1) Taking isotropic coke with a mosaic structure as a raw material; crushing and grading raw materials, mixing binder high-temperature asphalt and the raw materials according to a mass ratio of 13:100, and granulating in a granulating kettle (the granulating temperature is 850 ℃ for 7 hours, and the stirring speed is 14HZ (300 Kg kettle)), so as to obtain a semi-finished product;
(2) Heating the semi-finished product to 1000 ℃ for pre-carbonization treatment for 6 hours;
(3) Heating the powder obtained after pre-carbonization to 3200 ℃ for graphitization treatment to obtain graphitized particles C;
(4) Screening the graphitized particles C, and mixing a coating agent (epoxy resin and medium-temperature asphalt) with the graphitized particles C according to a ratio of 4:100 mass ratio, and then heating to 1200 ℃ for carbonization for 7 hours to prepare the first artificial graphite.
Comparative example 4
This comparative example a lithium battery was prepared with reference to example 1, and this comparative example was different from example 1 in that: the aspect ratio of the first artificial graphite in the negative electrode active material used in this example was 2.2:1. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
(1) Taking high-orientation coal needle coke with a fibrous structure as a raw material; crushing and grading raw materials, mixing binder high-temperature asphalt and the raw materials according to a mass ratio of 15.7:100, and granulating in a granulating kettle (the granulating temperature is 850 ℃ for 7 hours, and the stirring speed is 19HZ (300 Kg kettle)), so as to obtain a semi-finished product;
(2) Heating the semi-finished product to 1000 ℃ for pre-carbonization treatment for 6 hours;
(3) Heating the powder obtained after pre-carbonization to 3200 ℃ for graphitization treatment to obtain graphitized particles C;
(4) Screening the graphitized particles C, and mixing a coating agent (epoxy resin and medium-temperature asphalt) with the graphitized particles C according to a ratio of 4:100 mass ratio, and then heating to 1200 ℃ for carbonization for 7 hours to prepare the first artificial graphite.
Comparative example 5
This comparative example a lithium battery was prepared with reference to example 1, and this comparative example was different from example 1 in that: the degree of orientation OI of the first artificial graphite in the negative electrode active material used in this example was 3.5. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
(1) Taking needle coke with high orientation degree as a raw material; crushing and shaping raw materials, mixing binder high-temperature asphalt and the raw materials according to the mass ratio of 16:100, and granulating in a granulating kettle (the granulating temperature is 850 ℃, the time is 7h, and the stirring speed is 18HZ (300 Kg kettle)), so as to obtain a semi-finished product;
(2) Heating the semi-finished product to 1000 ℃ for pre-carbonization treatment for 6 hours;
(3) Heating the powder obtained after pre-carbonization to 3200 ℃ for graphitization treatment to obtain graphitized particles C;
(4) Screening the graphitized particles C, and mixing a coating agent (epoxy resin and medium-temperature asphalt) with the graphitized particles C according to a ratio of 4:100 mass ratio, and then heating to 1200 ℃ for carbonization for 7 hours to prepare the first artificial graphite.
Comparative example 6
This comparative example a lithium battery was prepared with reference to example 1, and this comparative example was different from example 1 in that: the degree of orientation OI of the first artificial graphite in the negative electrode active material used in this example was 1.8. Except for the above differences, the materials used in this example and the process operations were exactly the same as in example 1.
(1) Taking high anisotropic needle coke as a raw material; crushing and shaping raw materials, mixing binder high-temperature asphalt and the raw materials according to a mass ratio of 13:100, and granulating in a granulating kettle (the granulating temperature is 850 ℃, the time is 7h, and the stirring speed is 15HZ (300 Kg kettle)), so as to obtain a semi-finished product;
(2) Heating the semi-finished product to 1000 ℃ for pre-carbonization treatment for 6 hours;
(3) Heating the powder obtained after pre-carbonization to 3200 ℃ for graphitization treatment to obtain graphitized particles C;
(4) Screening the graphitized particles C, and mixing a coating agent (epoxy resin and medium-temperature asphalt) with the graphitized particles C according to a ratio of 4:100 mass ratio, and then heating to 1200 ℃ for carbonization for 7 hours to prepare the first artificial graphite.
Test example 1
1. Test object:
Examples 1 to 9 and comparative examples 1 to 6 were used as test subjects of the present test example.
2. Test items:
(1) Gram volume: the half-battery test material gram is adopted to play, the button cell manufacturing is completed according to the standard graphite button cell mounting step, the actual gram play of the graphite material is obtained through the test, and the charging and discharging modes are as follows: DC:0.6mA to 5.0mV,0.06mA to 5.0mV,CC:0.6mA to 2.0V.
(2) Quick charge performance: and 3C direct charging test is carried out on the battery by adopting a Xinwei test cabinet, the cut-off voltage is 4.48V, the cut-off current is 0.025C, and the ratio of the 3C direct charging capacity to the total charging capacity acquired by the test cabinet is checked to be the 3C charging cross current ratio.
(3) Different temperature cycle capacity retention and volume expansion rates:
1) And (3) normal temperature circulation: 1C constant-current and constant-voltage charging to 4.48V, and 0.025C cut-off, and testing the initial thickness of the battery; then under 25 ℃ environment: ① Standing for 1min; ② Constant current discharge of 1C to 3.0V; ③ Standing for 5min; ④ 3C constant-current and constant-voltage charging to 4.48V, and 0.025C cut-off; ⑤ Standing for 5min; ⑥ Constant current discharge of 1C to 3.0V; ⑦ Standing for 5min; ⑧ The ④-⑦ cycle was repeated for 800 weeks; ⑨ Constant current and constant voltage charging of 1.0C to 4.48V and cutoff of 0.025C.
The full charge thickness of the battery was measured after 800 weeks of cycling, and the ratio of the full charge thickness of the battery to the initial thickness after 800 weeks was the volume expansion rate. The ratio of the remaining capacity after completion of 800-week cycle to the first-cycle discharge capacity was the capacity retention rate.
2) Cycling at 45 ℃): the process steps are the same as those in 1), except that the test is carried out in a constant temperature cabinet at 45 ℃ to test 600 circles.
3) Cycling at 15℃: the process steps are the same as those in 1), except that the test is carried out in a constant temperature cabinet at 15 ℃ to test 400 circles.
3. Test results:
Table 1 parameters related to examples 1 to 9 and comparative examples 1 to 6
Table 2 relevant parameters for examples 1 to 9 and comparative examples 1 to 6
The test results are shown in tables 1 and 2. The performance test results corresponding to comparative examples 1 to 6 were compared with example 1. As can be seen from table 1, under the same conditions of other materials and operations for preparing a battery, the gram capacity of the negative electrode active material obtained in example 1 is higher, the volume expansion rate of the battery is lower, and the particle diameter D50 of the first artificial graphite used in comparative example 1 is less than 11 μm, so that the gram capacity of the negative electrode active material obtained is lower than that of example 1, and the volume expansion rate of the battery is higher than that of example 1; the first artificial graphite used in comparative example 2 had a particle size of > 15 μm, and the volume expansion ratio of the resulting battery was higher than that of example 1; the aspect ratio of the first artificial graphite used in comparative example 3 was < 1.5:1, and thus the gram capacity of the negative electrode active material was lower than that of example 1, and the volume expansion ratio of the battery was higher than that of example 1; the aspect ratio of the first artificial graphite used in comparative example 4 was > 2:1, and the volume expansion ratio of the resulting battery was higher than that of example 1; the degree of orientation OI of the first artificial graphite used in comparative example 5 was > 2.5, and the volume expansion ratio of the resulting battery was higher than that of example 1; the degree of orientation OI of the first artificial graphite used in comparative example 6 was <2, and the gram capacity of the negative electrode active material thus obtained was lower than that of example 1, and the volume expansion ratio of the battery was higher than that of example 1. From this, it is demonstrated that the battery provided in example 1 can provide the first artificial graphite with the advantages of high gram capacity and low cyclic expansion by simultaneously controlling the particle diameter, aspect ratio and orientation degree of the first artificial graphite in the negative electrode active material, as compared with comparative examples 1 to 6.
The performance test results of example 1 and example 2 were compared. As can be seen from table 1, the negative electrode active material used in example 2 did not include the second artificial graphite under the same conditions as other materials and operations for preparing a battery, and thus the cycle expansion rate of the obtained battery was higher than that of example 1, and the quick charge performance was lower than that of example 1. As described above, the battery provided in example 1 suppresses expansion of the battery during the cycle and improves the quick charge performance of the battery by using the second artificial graphite a together with the second artificial graphite B as the negative electrode active material, as compared to example 2.
The results of the performance tests of example 1 and examples 3 to 5 were compared. As can be seen from table 1, the mass of the first artificial graphite in the negative electrode active material used in example 3 was as follows under the same conditions as other materials and operations for preparing a battery: the mass of the second artificial graphite is less than 50-60: 40 to 50, the volume expansion ratio of the battery thus obtained was slightly higher than that of example 1, and the mass of the first artificial graphite in the negative electrode active material used in example 5: the mass of the second artificial graphite is more than 50 to 60:40 to 50, the cycle expansion ratio of the battery thus obtained was slightly higher than that of example 1, and the quick charge performance was slightly lower than that of example 1. From this, it is demonstrated that, compared with examples 3 and 5, the battery provided in examples 1 and 4 can exert a synergistic effect by reasonably setting the mass ratio of the first artificial graphite to the second artificial graphite in the negative electrode active material, so that the fast charge performance and the lithium ion transmission kinetics of the battery are further improved on the premise of ensuring the high gram capacity and the low volume expansion of the first artificial graphite.
The results of the performance tests of example 1 and examples 6 to 7 were compared. As is clear from table 1, the second artificial graphite used in example 6 contained only artificial graphite a under the same conditions as other materials and operations for preparing a battery, and thus the gram capacity of the negative electrode active material was lower than that of example 1, the cyclic expansion rate of the battery was higher than that of example 1, and the second artificial graphite used in example 7 contained only artificial graphite B, and thus the cyclic expansion rate of the battery was higher than that of example 1, and the quick charge performance was lower than that of example 1. From this, it is demonstrated that, with respect to examples 6 and 7, the battery provided in example 1 is capable of exerting a synergistic effect by using the second artificial graphite comprising the artificial graphite a and the artificial graphite B as the negative electrode active material, so that the thus-prepared negative electrode active material has the advantages of both the first artificial graphite and the second artificial graphite, thereby reducing the cyclic expansion of the negative electrode active material, increasing the gram capacity of the negative electrode active material, and improving the fast charge performance and lithium ion transport kinetics of the battery.
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 negative electrode active material is characterized by comprising first artificial graphite, wherein the first artificial graphite is secondary particles, and the length-diameter ratio of the first artificial graphite is 1.5-2.0: 1, wherein the grain diameter D50 of the first artificial graphite is 11-15 mu m, and the orientation degree OI value of the first artificial graphite is 2.0-2.5;
the orientation degree OI value is the ratio of the peak area of 004 characteristic diffraction peaks to the peak area of 110 characteristic diffraction peaks of the first artificial graphite in the XRD diffraction pattern.
2. The anode active material according to claim 1, wherein the first artificial graphite is produced by a process comprising the steps of:
S1, taking needle coke as a raw material, mixing a binder with the raw material, and granulating to obtain a semi-finished product;
S2, carrying out pre-carbonization treatment on the semi-finished product to obtain a precursor;
s3, graphitizing the precursor to obtain graphitized particles;
s4, coating the graphitized particles by adopting a coating agent in a liquid phase and carbonizing to obtain the first artificial graphite.
3. The anode active material according to claim 2, wherein the needle coke has a particle diameter of 8 μm or less and a tap density of 0.8g/cm 3 or more.
4. The negative electrode active material of claim 2, wherein the coating agent comprises at least two of epoxy resin, phenolic resin, medium temperature pitch, coal tar.
5. The negative electrode active material according to claim 1, further comprising a second artificial graphite, wherein a mass ratio of the first artificial graphite to the second artificial graphite is 50 to 60: 40-50 percent;
The second artificial graphite comprises artificial graphite A and artificial graphite B,
The artificial graphite A is primary particles, the particle size D50=8-10 μm of the artificial graphite A has the graphitization degree of 91.5-93%,
The artificial graphite B is secondary particles, the particle size D50=11-14 μm of the artificial graphite B, and the graphitization degree is 93-94%.
6. The negative electrode active material according to claim 5, wherein the artificial graphite a has a tap density of 0.95 to 1.05g/cm 3.
7. A negative electrode sheet comprising a negative electrode current collector and a negative electrode active coating layer provided on a surface of the negative electrode current collector, the negative electrode active coating layer comprising the negative electrode active material according to any one of claims 1 to 6.
8. The negative electrode sheet according to claim 7, wherein the surface density of the negative electrode active coating layer is 20m 2/g or more.
9. The negative electrode sheet of claim 7, wherein the negative electrode active coating has a compacted density of 1.8g/cm 3 or more.
10. A lithium battery comprising the negative electrode sheet according to any one of claims 7 to 9.
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