CN111864206A - Hard carbon negative electrode material, preparation method thereof, pole piece comprising hard carbon negative electrode material and lithium ion battery - Google Patents
Hard carbon negative electrode material, preparation method thereof, pole piece comprising hard carbon negative electrode material and lithium ion battery Download PDFInfo
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- CN111864206A CN111864206A CN201910364006.XA CN201910364006A CN111864206A CN 111864206 A CN111864206 A CN 111864206A CN 201910364006 A CN201910364006 A CN 201910364006A CN 111864206 A CN111864206 A CN 111864206A
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- hard carbon
- negative electrode
- electrode material
- carbon negative
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- 229910021385 hard carbon Inorganic materials 0.000 title claims abstract description 278
- 239000007773 negative electrode material Substances 0.000 title claims abstract description 141
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 16
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 15
- 239000007833 carbon precursor Substances 0.000 claims abstract description 65
- 238000000034 method Methods 0.000 claims abstract description 49
- 239000000654 additive Substances 0.000 claims abstract description 48
- 238000002156 mixing Methods 0.000 claims abstract description 47
- 230000000996 additive effect Effects 0.000 claims abstract description 45
- 150000003839 salts Chemical class 0.000 claims abstract description 36
- 238000005245 sintering Methods 0.000 claims abstract description 30
- 238000006555 catalytic reaction Methods 0.000 claims abstract description 25
- 238000010438 heat treatment Methods 0.000 claims description 54
- 239000000463 material Substances 0.000 claims description 38
- 239000002245 particle Substances 0.000 claims description 30
- 238000001237 Raman spectrum Methods 0.000 claims description 29
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 28
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 25
- 238000001816 cooling Methods 0.000 claims description 21
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 20
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 claims description 19
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 18
- 239000012298 atmosphere Substances 0.000 claims description 18
- 238000001035 drying Methods 0.000 claims description 18
- 230000001681 protective effect Effects 0.000 claims description 18
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 16
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 claims description 16
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 16
- -1 polytetrafluoroethylene Polymers 0.000 claims description 16
- 239000002994 raw material Substances 0.000 claims description 16
- 229910052751 metal Inorganic materials 0.000 claims description 15
- 239000002184 metal Substances 0.000 claims description 15
- 238000005406 washing Methods 0.000 claims description 15
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 12
- 150000001768 cations Chemical class 0.000 claims description 12
- 238000002791 soaking Methods 0.000 claims description 12
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 11
- 239000002253 acid Substances 0.000 claims description 11
- 238000003763 carbonization Methods 0.000 claims description 11
- 229910052698 phosphorus Inorganic materials 0.000 claims description 11
- 239000011574 phosphorus Substances 0.000 claims description 11
- 238000010000 carbonizing Methods 0.000 claims description 10
- 229910052757 nitrogen Inorganic materials 0.000 claims description 10
- 239000001103 potassium chloride Substances 0.000 claims description 10
- 235000011164 potassium chloride Nutrition 0.000 claims description 10
- 239000011780 sodium chloride Substances 0.000 claims description 9
- 229910000398 iron phosphate Inorganic materials 0.000 claims description 8
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims description 8
- 229910001629 magnesium chloride Inorganic materials 0.000 claims description 8
- 230000035484 reaction time Effects 0.000 claims description 8
- 238000012216 screening Methods 0.000 claims description 8
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 7
- 229910019142 PO4 Inorganic materials 0.000 claims description 7
- 239000001110 calcium chloride Substances 0.000 claims description 7
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 7
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 7
- 239000010452 phosphate Substances 0.000 claims description 7
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 6
- 229910052786 argon Inorganic materials 0.000 claims description 6
- 239000001307 helium Substances 0.000 claims description 6
- 229910052734 helium Inorganic materials 0.000 claims description 6
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 6
- 229910052743 krypton Inorganic materials 0.000 claims description 6
- DNNSSWSSYDEUBZ-UHFFFAOYSA-N krypton atom Chemical compound [Kr] DNNSSWSSYDEUBZ-UHFFFAOYSA-N 0.000 claims description 6
- 229910052754 neon Inorganic materials 0.000 claims description 6
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 claims description 6
- 229910052724 xenon Inorganic materials 0.000 claims description 6
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 claims description 6
- 229910002651 NO3 Inorganic materials 0.000 claims description 5
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 5
- 239000003822 epoxy resin Substances 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 229910000159 nickel phosphate Inorganic materials 0.000 claims description 5
- JOCJYBPHESYFOK-UHFFFAOYSA-K nickel(3+);phosphate Chemical compound [Ni+3].[O-]P([O-])([O-])=O JOCJYBPHESYFOK-UHFFFAOYSA-K 0.000 claims description 5
- 229920000647 polyepoxide Polymers 0.000 claims description 5
- 239000002028 Biomass Substances 0.000 claims description 4
- 244000060011 Cocos nucifera Species 0.000 claims description 4
- 235000013162 Cocos nucifera Nutrition 0.000 claims description 4
- 235000001950 Elaeis guineensis Nutrition 0.000 claims description 4
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 4
- 240000007049 Juglans regia Species 0.000 claims description 4
- 235000009496 Juglans regia Nutrition 0.000 claims description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 4
- 244000018633 Prunus armeniaca Species 0.000 claims description 4
- 235000009827 Prunus armeniaca Nutrition 0.000 claims description 4
- 238000006243 chemical reaction Methods 0.000 claims description 4
- 229910000152 cobalt phosphate Inorganic materials 0.000 claims description 4
- ZBDSFTZNNQNSQM-UHFFFAOYSA-H cobalt(2+);diphosphate Chemical compound [Co+2].[Co+2].[Co+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O ZBDSFTZNNQNSQM-UHFFFAOYSA-H 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
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- 239000007787 solid Substances 0.000 claims description 4
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- 235000020234 walnut Nutrition 0.000 claims description 4
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 claims description 3
- 229920002134 Carboxymethyl cellulose Polymers 0.000 claims description 3
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 claims description 3
- 239000004793 Polystyrene Substances 0.000 claims description 3
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 3
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 3
- 239000001768 carboxy methyl cellulose Substances 0.000 claims description 3
- 235000010948 carboxy methyl cellulose Nutrition 0.000 claims description 3
- 239000008112 carboxymethyl-cellulose Substances 0.000 claims description 3
- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 claims description 3
- 229910001981 cobalt nitrate Inorganic materials 0.000 claims description 3
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 3
- MVFCKEFYUDZOCX-UHFFFAOYSA-N iron(2+);dinitrate Chemical compound [Fe+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MVFCKEFYUDZOCX-UHFFFAOYSA-N 0.000 claims description 3
- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 claims description 3
- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 claims description 3
- 239000005011 phenolic resin Substances 0.000 claims description 3
- 229920001568 phenolic resin Polymers 0.000 claims description 3
- 229920003229 poly(methyl methacrylate) Polymers 0.000 claims description 3
- 239000004926 polymethyl methacrylate Substances 0.000 claims description 3
- 229920002223 polystyrene Polymers 0.000 claims description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 3
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- 238000001291 vacuum drying Methods 0.000 claims description 3
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 2
- MQRWBMAEBQOWAF-UHFFFAOYSA-N acetic acid;nickel Chemical compound [Ni].CC(O)=O.CC(O)=O MQRWBMAEBQOWAF-UHFFFAOYSA-N 0.000 claims description 2
- 238000007605 air drying Methods 0.000 claims description 2
- 239000003054 catalyst Substances 0.000 claims description 2
- 239000003610 charcoal Substances 0.000 claims description 2
- 229910017052 cobalt Inorganic materials 0.000 claims description 2
- 239000010941 cobalt Substances 0.000 claims description 2
- 229940011182 cobalt acetate Drugs 0.000 claims description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 2
- GVPFVAHMJGGAJG-UHFFFAOYSA-L cobalt dichloride Chemical compound [Cl-].[Cl-].[Co+2] GVPFVAHMJGGAJG-UHFFFAOYSA-L 0.000 claims description 2
- QAHREYKOYSIQPH-UHFFFAOYSA-L cobalt(II) acetate Chemical compound [Co+2].CC([O-])=O.CC([O-])=O QAHREYKOYSIQPH-UHFFFAOYSA-L 0.000 claims description 2
- 230000005347 demagnetization Effects 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- FBAFATDZDUQKNH-UHFFFAOYSA-M iron chloride Chemical compound [Cl-].[Fe] FBAFATDZDUQKNH-UHFFFAOYSA-M 0.000 claims description 2
- PVFSDGKDKFSOTB-UHFFFAOYSA-K iron(3+);triacetate Chemical compound [Fe+3].CC([O-])=O.CC([O-])=O.CC([O-])=O PVFSDGKDKFSOTB-UHFFFAOYSA-K 0.000 claims description 2
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 229940078494 nickel acetate Drugs 0.000 claims description 2
- 229910017604 nitric acid Inorganic materials 0.000 claims description 2
- 238000000746 purification Methods 0.000 claims description 2
- 238000007873 sieving Methods 0.000 claims description 2
- 240000003133 Elaeis guineensis Species 0.000 claims 1
- 239000003575 carbonaceous material Substances 0.000 abstract description 24
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- 238000012360 testing method Methods 0.000 description 35
- 230000000052 comparative effect Effects 0.000 description 27
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 26
- 238000001179 sorption measurement Methods 0.000 description 19
- 230000000694 effects Effects 0.000 description 17
- 239000010439 graphite Substances 0.000 description 14
- 229910002804 graphite Inorganic materials 0.000 description 14
- 239000010406 cathode material Substances 0.000 description 13
- 238000000840 electrochemical analysis Methods 0.000 description 13
- 239000012299 nitrogen atmosphere Substances 0.000 description 12
- 230000002829 reductive effect Effects 0.000 description 10
- 230000002441 reversible effect Effects 0.000 description 10
- 229910052799 carbon Inorganic materials 0.000 description 9
- 239000005539 carbonized material Substances 0.000 description 9
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 8
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- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 2
- 229910001290 LiPF6 Inorganic materials 0.000 description 2
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- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 2
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 2
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- UEZVMMHDMIWARA-UHFFFAOYSA-N Metaphosphoric acid Chemical compound OP(=O)=O UEZVMMHDMIWARA-UHFFFAOYSA-N 0.000 description 1
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
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- 150000001721 carbon Chemical group 0.000 description 1
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Images
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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
-
- 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
-
- 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
Abstract
The invention provides a hard carbon negative electrode material, a preparation method thereof, a pole piece containing the hard carbon negative electrode material and a lithium ion battery. The hard carbon negative electrode material comprises an inner main body and an outer layer coated on the inner main body, wherein the disorder degree of the outer layer is lower than that of the inner main body, and the inner main body and the outer layer both comprise hard carbon. The preparation method comprises the following steps: 1) mixing the first hard carbon precursor, the additive and the molten salt, and then carrying out catalytic reaction to obtain a second hard carbon precursor; 2) and purifying the second hard carbon precursor, and sintering to obtain the hard carbon negative electrode material. The hard carbon negative electrode material provided by the invention improves the capacity, reduces the adsorptivity and has good cycle performance. The preparation method provided by the invention starts with the structure of the hard carbon material to carry out structure optimization design, and prepares the hard carbon negative electrode material with high capacity and low adsorbability by using a molten salt auxiliary process and an additive.
Description
Technical Field
The invention belongs to the technical field of energy storage materials, relates to a negative electrode material, and particularly relates to a hard carbon negative electrode material, a preparation method thereof, a pole piece containing the hard carbon negative electrode material, and a lithium ion battery.
Background
Research on carbon materials as electrochemical lithium intercalation host materials has been the focus of lithium ion battery negative electrode material research. The graphite carbon negative electrode material has low electrode potential (<1.0V vs.Li/Li+) Long cycle life, good safety and low price, and the like, and becomes the main cathode material of the current commercial lithium ion battery. However, the graphite negative electrode material has a layered structure and poor compatibility with an electrolyte, and a solvent ion co-intercalation phenomenon is easily generated in the charge and discharge processes to cause structural damage, so that the circulation stability and the coulombic efficiency of the graphite negative electrode material are affected. Meanwhile, the anisotropic structure characteristics of graphite limit the free diffusion of lithium ions in the graphite structure, restrict the exertion of the electrochemical capacity of the graphite cathode, and particularly influence the rate capability of the graphite cathode material. These problems make it difficult for simple carbon negative electrode materials to meet the requirements of increasingly developed electronic devices, electric automobiles, and the like for high-performance lithium ion batteries.
Compared with graphite, the hard carbon has the isotropic structural characteristics, has larger interlayer spacing, can accelerate the diffusion of lithium ions, and has the characteristics of better cycle performance and rate capability, low cost and the like, so that the hard carbon material is paid attention again to power type lithium ion batteries. However, the hard carbon material has many surface defects and a large specific surface area, so that the hard carbon material has strong adsorbability, and can adsorb part of water to form a bonding effect even if placed in the air, and the hard carbon material cannot be removed even through vacuum drying treatment at 120 ℃, so that the capacity and the first effect of the hard carbon material are greatly reduced after the hard carbon material is placed in the air for a period of time, and the practical application of the hard carbon material is limited, and therefore, the problem of high adsorbability of the hard carbon material needs to be improved through process optimization urgently. The existing process can only realize the optimization of partial properties (such as capacity, first effect, high-temperature performance or rate performance) of the hard carbon through a doping or surface modification process, and cannot realize the effect of improving the capacity and reducing the adsorptivity on the hard carbon material at the same time.
CN 102820455A discloses a preparation method of a hard carbon cathode material of a lithium ion battery, which is technically characterized in that the hard carbon cathode material is prepared by mixing a carbon source, additives of silicon and phosphorus according to a certain proportion and sintering at high temperature. The process mainly improves the first discharge capacity of the cathode material. However, the hard carbon material prepared by the method has many surface defects and low first coulombic efficiency, and the practical application of the material is influenced.
CN101901891A discloses an electrode material, which comprises an electrode material, a binder and a hydrogen storage alloy, and the hydrogen storage alloy adsorbs hydrogen generated by a lithium battery material during charging and discharging, so as to solve the problem of gas expansion of a lithium battery containing lithium titanate, hard carbon, soft carbon and other water-absorbable negative electrode materials. However, after water is absorbed by the hard carbon material, part of energy density is sacrificed by adding the adsorptive material, and meanwhile, the adsorbed water is decomposed rapidly in the high-rate charge and discharge process, so that the electric core is inflated rapidly, and huge potential safety hazards exist.
CN106629665A discloses a molten salt method for preparing sulfur-doped hard carbon nano-sheets and application thereof in sodium ion batteries, which comprises the following steps: fully grinding 0.1-0.2g of glucose, 0.1-0.2g of sulfur powder and 2-4g of molten salt (the weight ratio of LiCl/KCl is 40-50/50-60), putting the uniformly mixed reactants into a corundum boat, and placing the corundum boat in a tube furnace. Calcining at 300-400 ℃ for 1-3h in the argon atmosphere, calcining at 550-750 ℃ for 4-6h, cooling to room temperature, taking out a sample, washing and collecting. However, the hard carbon nano-sheet prepared by the method has strong adsorbability, and the performance is greatly reduced due to partial water adsorption after the hard carbon nano-sheet is placed in the air for a period of time.
Therefore, the research and development of a hard carbon negative electrode material with high capacity and low adsorbability is a technical problem in the field of lithium ion batteries.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a hard carbon negative electrode material, a preparation method thereof, a pole piece containing the hard carbon negative electrode material and a lithium ion battery. The hard carbon negative electrode material provided by the invention has high capacity and low adsorbability, can greatly reduce the performance attenuation generated after the hard carbon material is placed in the air, and obviously improves the cycle stability.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a hard carbon negative electrode material, comprising an inner main body and an outer layer coated on the inner main body, wherein the disorder degree of the outer layer is lower than that of the inner main body, and the inner main body and the outer layer both comprise hard carbon.
The hard carbon negative electrode material provided by the invention is a high-capacity low-adsorbability hard carbon negative electrode material. The hard carbon negative electrode material provided by the invention structurally comprises an inner main body and an outer layer, wherein the disorder degree of the outer layer is lower than that of the inner main body, namely the surface microcrystalline structure of the hard carbon negative electrode material provided by the invention tends to be regular, so that the porosity is reduced, the hydrophobicity is improved, and the aim of reducing the adsorbability of hard carbon is fulfilled. In the present invention, the disorder means a disorder of carbon atom arrangement.
The inner main body and the outer layer of the hard carbon cathode material provided by the invention are structures formed by reducing the disorder degree of the hard carbon surface layer, the part with the reduced disorder degree is the outer layer, and the part with the unchanged disorder degree is the inner main body.
The following is a preferred technical solution of the present invention, but not a limitation to the technical solution provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solution.
In a preferred embodiment of the present invention, the ratio of the D peak intensity to the G peak intensity in the raman spectrum of the outer layer is 0.2 to 0.7, for example, 0.2, 0.3, 0.4, 0.5, 0.6, or 0.7, but the present invention is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.
Preferably, the inner body has a raman spectrum with a ratio of D-peak to G-peak intensities of 0.7 to 1.5, for example 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4 or 1.5, but not limited to the recited values, and other values not recited within the range of values are equally applicable.
In the invention, the intensity ratio of the D peak to the G peak in the Raman spectrum is used for measuring the disorder degree of carbon, and the smaller the intensity ratio is, the smaller the disorder degree is.
Preferably, the outer layer has a thickness of 0 to 1 μm and does not contain 0, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or 1 μm. Here, if the outer layer thickness is too thick, the rate capability of the hard carbon negative electrode material is reduced; if the outer layer thickness is too thin, the hydrophobicity may be lowered, and the effect of reducing the hard carbon adsorption may not be obtained.
As a preferable technical scheme of the invention, the specific surface area of the hard carbon negative electrode material is 1-20 m2G, e.g. 1m2/g、5m2/g、10m2/g、15m2G or 20m2And/g, but not limited to, the recited values, and other values not recited within the range of the recited values are also applicable, and are preferably 1.5 to 15m2/g。
Preferably, the hard carbon negative electrode material has a median particle diameter of 4.0 to 30.0 μm, for example, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm, 15.0 μm, 20.0 μm, 25.0 μm, or 30.0 μm, but is not limited to the values listed, and other values not listed in the numerical range are also applicable, preferably 5.0 to 20.0 μm, and more preferably 6.0 to 15.0 μm.
Preferably, the inner body and the outer layer of the hard carbon anode material both comprise hard carbon and a doping element doped in the hard carbon. The doping element can improve the capacity and the first effect of the hard carbon.
Preferably, in the hard carbon anode material, the doping element comprises phosphorus and/or nitrogen.
Preferably, in the hard carbon negative electrode material, the mass fraction of the doping elements is 0.3-5 wt% based on 100% of the total mass of the hard carbon negative electrode material. Here, if the mass fraction of the doping element is too large, the cycle performance of the hard carbon negative electrode material is reduced; if the mass fraction of the doping elements is too small, the capacity and the first effect of the hard carbon material are not obviously improved.
In a second aspect, the present invention provides a method for preparing the hard carbon negative electrode material according to the first aspect, the method comprising the steps of:
(1) mixing the first hard carbon precursor, the additive and the molten salt, and then carrying out catalytic reaction to obtain a second hard carbon precursor;
(2) and (3) purifying the second hard carbon precursor in the step (1), and sintering to obtain the hard carbon negative electrode material.
In the preparation method provided by the invention, the high-capacity low-adsorption hard carbon negative electrode material is prepared by low-temperature catalytic modification through adding additives by means of a low-temperature blending molten salt auxiliary process. Specifically, the additive is added into the low-temperature molten salt, metal cations in the additive and carbon elements on the surface of the hard carbon are melted to form a compound (such as an iron-carbon compound), and the compound is decomposed after the temperature is further increased so that carbon atoms are rearranged, the microcrystalline structure on the surface of the hard carbon tends to be regular, the porosity is reduced, the hydrophobicity is improved, and the purpose of reducing the adsorptivity of the hard carbon is achieved. The process has the characteristics of simple process, remarkable effect, strong pertinence and convenience for industrial production.
As a preferred embodiment of the present invention, in the step (1), the method for preparing the first hard carbon precursor includes: carbonizing the hard carbon raw material, and then crushing to obtain a first hard carbon precursor.
Preferably, the hard charcoal raw material comprises a biomass raw material and/or a thermoplastic resin raw material.
Preferably, the biomass raw material comprises any one of coconut shells, apricot shells, walnut shells or oil palm shells or a combination of at least two of the coconut shells, the apricot shells, the walnut shells and the oil palm shells.
Preferably, the thermoplastic resin raw material comprises any one of epoxy resin, phenolic resin, carboxymethyl cellulose, ethyl methyl carbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate or polytetrafluoroethylene or a combination of at least two of the epoxy resin, the phenolic resin, the carboxymethyl cellulose, the ethyl methyl carbonate, the polyvinyl alcohol, the polystyrene, the polymethyl methacrylate or the polytetrafluoroethylene.
Preferably, the carbonization is performed under a protective atmosphere.
Preferably, the protective atmosphere is any one of nitrogen, helium, neon, argon, krypton or xenon or a combination of at least two thereof.
Preferably, the carbonization temperature is 400 to 800 ℃, for example 400 ℃, 500 ℃, 600 ℃, 700 ℃, or 800 ℃, but is not limited to the recited values, and other values not recited within the range of values are also applicable.
Preferably, the carbonization time is 1 to 8 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours, but not limited to the recited values, and other values not recited within the range of the values are also applicable.
Preferably, the temperature increase rate of the carbonization is 0.5 to 5 ℃/min, for example, 0.5 ℃/min, 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min, or 5 ℃/min, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable, and preferably 1 to 3 ℃/min.
Preferably, the carbonized mixture is cooled to 20-30 ℃ and then crushed. Namely, the mixture is cooled to room temperature and then crushed.
Preferably, the carbonization is performed in any one of a vacuum furnace, a box furnace, a rotary furnace, a roller kiln, a pusher kiln, or a tube furnace.
Preferably, the apparatus for performing the comminution comprises a crusher and/or a jet mill, preferably a combination of a crusher and a crusher.
Preferably, the crusher comprises any one of a jaw crusher, a cone crusher, an impact crusher, a counterimpact crusher or a hammer crusher or a combination of at least two of them.
Preferably, the pulverizer comprises any one of a flat jet mill, a fluidized bed counter-jet mill, a circulating tube jet mill, a counter-jet mill or a target jet mill or a combination of at least two thereof.
Preferably, when the apparatus for performing the comminution is a combination of a crusher and a crusher, the crusher is used first and then the crusher is used, the crusher crushes the material to a median particle size of 10 to 4000 μm, such as 10 μm, 100 μm, 500 μm, 1000 μm, 2000 μm, 3000 μm or 4000 μm, but not limited to the recited values, and other values not recited in this range are equally applicable, such as preferably 200 to 2000 μm.
Preferably, in the step (1), the first hard carbon precursor is pulverized by a pulverizer to have a median particle diameter of 4.0 to 30.0 μm, for example, 4.0 μm, 5.0 μm, 10.0 μm, 15.0 μm, 20.0 μm, 25.0 μm, or 30.0 μm, but not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable, preferably 5.0 to 20.0 μm, and more preferably 6.0 to 15.0 μm.
As a preferred technical scheme of the invention, in the step (1), the additive comprises metal cations.
Preferably, the additive comprises any one of or a combination of at least two of a salt compound of iron, a salt compound of cobalt, or a salt compound of nickel.
Preferably, the additive comprises nitrate and/or phosphate in addition to the metal cation. According to the invention, when the additive contains metal cations and nitrate and/or phosphate, the doping and catalysis can be synchronously carried out, the metal cations in the additive can play a role in catalysis, and non-metal elements in the additive can be fully doped into the hard carbon material, so that the capacity and the first effect of the hard carbon material can be improved.
Preferably, the additive comprises any one or a combination of at least two of iron phosphate, cobalt phosphate, nickel phosphate, iron nitrate, cobalt nitrate or nickel nitrate, typically but not limited to a combination of: a combination of iron phosphate and cobalt phosphate, a combination of nickel phosphate and iron nitrate, a combination of cobalt nitrate and nickel nitrate, and the like.
Preferably, the additive comprises a nitrate-or phosphate-free metal salt comprising any one of iron acetate, iron chloride, cobalt acetate, cobalt chloride, nickel acetate or nickel chloride or a combination of at least two thereof, and a nitrate-or phosphate-containing substance.
Preferably, in step (1), the molten salt comprises any one or a combination of at least two of potassium chloride, sodium chloride, lithium chloride, magnesium chloride or calcium chloride, typically but not limited to a combination of: combinations of potassium chloride and sodium chloride, combinations of sodium chloride and lithium chloride, combinations of lithium chloride and magnesium chloride, combinations of lithium chloride, magnesium chloride and calcium chloride, and the like.
Preferably, in step (1), the mixing is carried out in a mixing device.
Preferably, the mixing device comprises any one of a VC mixer, a ball mill, or a double cone blender.
Preferably, in the step (1), the mass ratio of the first hard carbon precursor to the molten salt to the additive is 1 (2-10): 0.01-0.5, for example, 1:2:0.01, 1:3:0.08, 1:4:0.1, 1:6:0.2, 1:8:0.4 or 1:10:0.5, but not limited to the enumerated values, and other non-enumerated values within the numerical range are also applicable, and preferably 1 (3-8): 0.03-0.3.
Preferably, the catalytic reaction of step (1) is carried out under a protective atmosphere.
Preferably, the protective atmosphere is any one of nitrogen, helium, neon, argon, krypton or xenon or a combination of at least two thereof.
Preferably, the catalytic reaction is carried out in any one of a vacuum furnace, a box furnace, a rotary furnace, a roller kiln, a pusher kiln, or a tube furnace.
Preferably, the reaction temperature of the catalytic reaction is 500 ℃ to 1000 ℃.
Preferably, the reaction time of the catalytic reaction is 0.5 to 8 hours, for example, 0.5 hour, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours, but is not limited to the recited values, and other values not recited in the range of the values are also applicable, preferably 1 to 6 hours. The thickness of the outer layer of the hard carbon material provided by the invention can be controlled through the time of catalytic reaction, the longer the time of catalytic reaction is, the more sufficient the rearrangement of the carbon skeleton is carried out, and the thicker the thickness of the outer layer with low disorder degree is.
Preferably, the temperature increase rate of the catalyst reaction is 0.5 to 10 ℃/min, for example, 0.5 ℃/min, 1 ℃/min, 2 ℃/min, 4 ℃/min, 6 ℃/min, 8 ℃/min, or 10 ℃/min, but not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable, preferably 1 to 6 ℃/min, and more preferably 2 to 4 ℃/min.
As a preferred embodiment of the present invention, in the step (2), the method for purifying includes: and (2) mixing the second hard carbon precursor in the step (1), acid and water, soaking, then centrifugally washing, and drying the obtained solid substance.
Preferably, the acid comprises any one of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid or hydrofluoric acid, or a combination of at least two thereof.
Preferably, the mass ratio of the second hard carbon precursor, the acid and the water is 1 (0.5-5): 2-20, for example, 1:0.5:2, 1:1:5, 1:1.5:10, 1:2:15, 1:0.8:18 or 1:5:20, but not limited to the enumerated values, and other non-enumerated values within the numerical range are also applicable.
Preferably, the soaking time is 1 to 10 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, but not limited to the recited values, and other values within the range of the values are also applicable, preferably 1 to 4 hours.
Preferably, the time for the centrifugal washing is 0.5 to 6 hours, for example, 0.5 hour, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours, but not limited to the recited values, and other values not recited in the range of the values are also applicable, preferably 1 to 4 hours, and more preferably 1.5 to 3 hours.
Preferably, the drying is performed in any one of a vacuum drying oven, a forced air drying oven, a box oven, a rotary kiln or a double cone dryer.
Preferably, the temperature of the drying is 60 to 200 ℃, for example, 60 ℃, 80 ℃, 100 ℃, 120 ℃, 140 ℃, 160 ℃, 180 ℃ or 200 ℃, but not limited to the recited values, and other values not recited in the range of the values are also applicable, preferably 80 to 150 ℃.
Preferably, the drying time is 6-48 h, such as 6h, 12h, 18h, 24h, 30h, 36h, 42h or 48h, but not limited to the recited values, and other values not recited in the range of the values are also applicable.
Preferably, in step (2), the sintering is performed under a protective atmosphere.
Preferably, the protective atmosphere is any one of nitrogen, helium, neon, argon, krypton or xenon or a combination of at least two thereof.
Preferably, the sintering is performed in any one of a vacuum furnace, a box furnace, a rotary furnace, a roller kiln, a pusher kiln, or a tube furnace.
Preferably, the sintering temperature is 900 to 1400 ℃, for example 900 ℃, 1000 ℃, 1100 ℃, 1200 ℃, 1300 ℃ or 1400 ℃, but is not limited to the recited values, and other values not recited in the numerical range are also applicable.
Preferably, the sintering time is 2 to 8 hours, such as 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours, but not limited to the recited values, and other values not recited within the range of values are also applicable, preferably 3 to 6 hours.
Preferably, the heating rate of the sintering is 0.5 to 10 ℃/min, for example, 1 ℃/min, 2 ℃/min, 4 ℃/min, 6 ℃/min, 8 ℃/min, or 10 ℃/min, but not limited to the values listed, and other values not listed within this range are also applicable, preferably 1 to 6 ℃/min.
Preferably, the preparation method further comprises: refining the hard carbon negative electrode material obtained in the step (2);
preferably, the refining comprises demagnetization and sieving.
As a further preferable technical scheme of the preparation method, the method comprises the following steps:
(1) heating a hard carbon raw material to 400-800 ℃ at a heating rate of 1-3 ℃/min under a protective atmosphere, carbonizing for 1-8 h, cooling to 20-30 ℃, crushing, and crushing the median particle size of the material to 6.0-15.0 mu m to obtain a first hard carbon precursor;
(2) mixing a first hard carbon precursor, an additive and molten salt, wherein the mass ratio of the first hard carbon precursor to the molten salt to the additive is 1 (2-10) to 0.01-0.5, heating to 500-1000 ℃ at a heating rate of 2-4 ℃/min under a protective atmosphere for doping and catalytic reaction for 1-6 h to obtain a second hard carbon precursor;
Wherein the additive comprises any one or the combination of at least two of iron salt compound, cobalt salt compound or nickel salt compound; and the additive comprises nitrate and/or phosphate besides metal cations; the molten salt comprises any one or the combination of at least two of potassium chloride, sodium chloride, lithium chloride, magnesium chloride or calcium chloride;
(3) and (3) mixing the second hard carbon precursor, acid and water in the step (2), wherein the mass ratio of the second hard carbon precursor to the acid to the water is 1 (0.5-5) to (2-20), soaking for 1-4 h after mixing, then centrifugally washing for 1.5-3 h, drying for 6-48 h at 80-150 ℃, then heating to 900-1400 ℃ at a heating rate of 3-5 ℃/min in a protective atmosphere, sintering for 3-6 h, demagnetizing and screening the obtained product after sintering, and thus obtaining the hard carbon negative electrode material.
The further preferred technical scheme adopts a low-temperature blending molten salt auxiliary process, and achieves the purposes of surface catalytic modification and doping modification by adding specific additives into the molten salt. According to the invention, a carbon source, an additive and molten salt are uniformly mixed according to a certain proportion, then are pretreated at a low temperature, then are added with acid for purification and impurity removal, and are dried and then are burnt to a high temperature, thus obtaining the high-capacity low-adsorption hard carbon negative electrode material.
In a third aspect, the present invention provides a pole piece comprising a hard carbon negative electrode material as described in the first aspect.
In a fourth aspect, the present invention provides a lithium ion battery comprising a hard carbon negative electrode material according to the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
(1) the hard carbon negative electrode material provided by the invention improves the capacity, reduces the adsorptivity, has good cycle performance, the first lithium removal capacity can reach 499.4mAh/g, the first coulombic efficiency can reach 85.2%, the retention rate of 1000 cycle capacity can reach 92.5%, the reversible capacity after being placed in the air for 30 days can reach 490.6mAh/g, and the first coulombic efficiency after being placed in the air for 30 days can reach 84.7%.
(2) The preparation method provided by the invention starts with the structure of the hard carbon material to carry out structure optimization design, prepares the hard carbon cathode material with high capacity and low adsorbability by one-step method through a molten salt auxiliary process, can improve the capacity and the first effect of the hard carbon by doping of non-metal elements, and achieves the purpose of reducing the specific surface area and the porosity of the hard carbon material by generating carbide through metal cations in the additive and a carbon material and then decomposing the carbide to rearrange a carbon skeleton, thereby improving the adsorption performance of the hard carbon material. In addition, the preparation method provided by the invention has the characteristics of simple process, remarkable effect, strong pertinence and convenience for industrial production.
Drawings
Fig. 1 is a scanning electron microscope picture of the hard carbon negative electrode material prepared in example 1 of the present invention;
fig. 2 is a raman spectrum of the hard carbon negative electrode material prepared in example 1 of the present invention;
fig. 3 is a first charge-discharge curve of the hard carbon negative electrode material prepared in example 1 of the present invention;
fig. 4 is a cycle performance curve of the hard carbon negative electrode material prepared in example 1 of the present invention.
Detailed Description
In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
The following are typical but non-limiting examples of the invention:
example 1
This example prepares a hard carbon negative electrode material as follows:
(1) heating 600g of apricot shells in a nitrogen atmosphere in a box furnace at a heating rate of 2 ℃/min to 600 ℃, carbonizing for 3h, cooling to 25 ℃ to obtain 170g of carbonized materials, crushing by using a ball mill, and crushing the median particle size of the materials to 10.0 mu m to obtain a first hard carbon precursor;
(2) mixing 100g of a first hard carbon precursor, 350g of potassium chloride, 300g of lithium chloride and 15g of iron phosphate together in a VC mixer, uniformly mixing, loading into a graphite crucible, placing into a box-type furnace, heating to 800 ℃ at a heating rate of 3 ℃/min under a nitrogen atmosphere for doping and catalytic reaction, wherein the reaction time is 4h, and cooling to 25 ℃ to obtain a second hard carbon precursor;
(3) Mixing the second hard carbon precursor, hydrochloric acid and water in the step (2), wherein the mass ratio of the second hard carbon precursor to the hydrochloric acid to the water is 1:2:10, soaking for 3h after mixing, then centrifugally washing for 2.5h, drying for 24h at 110 ℃, then putting 50g of the dried material into a crucible, placing the crucible into a tubular furnace, heating to 1100 ℃ at a heating rate of 4 ℃/min under a nitrogen atmosphere, sintering for 3h, naturally cooling after sintering, demagnetizing and screening the obtained product, and thus obtaining the hard carbon negative electrode material.
The hard carbon negative electrode material prepared in this example was subjected to a structural test using the following method:
the specific surface area of the material was tested using a Tristar3000 full-automatic specific surface area and porosity analyzer from Michner instruments USA.
The particle size range of the material and the average particle size of the raw material particles were measured using a malvern laser particle size tester MS 2000.
And testing the carbon layer disorder degree of the material by using a Raman spectrometer XPLORA.
The surface appearance, particle size and the like of the sample were observed by a scanning electron microscope of Hitachi S4800.
The hard carbon negative electrode material prepared by the embodiment comprises an inner main body and an outer layer coated on the inner main body, wherein the disorder degree of the outer layer is lower than that of the inner main body, and the inner main body and the outer layer both comprise hard carbon and doping elements doped in the hard carbon. The intensity ratio of a D peak to a G peak in a Raman spectrum of the whole hard carbon negative electrode material is 0.77, the intensity ratio of the D peak to the G peak in the Raman spectrum of the outer layer is 0.31, and the intensity ratio of the D peak to the G peak in the Raman spectrum of the inner main body is 1.04; the thickness of the outer layer is 0.5 μm; the specific surface area of the hard carbon negative electrode material is 2.853m 2(ii)/g; the doping element is phosphorus, and in the hard carbon negative electrode material, the mass fraction of the doping element is 1.836 wt% based on 100% of the total mass of the hard carbon negative electrode material.
The electrochemical test and the adsorption performance decay test results of the hard carbon negative electrode material prepared in this example are shown in table 1.
Fig. 1 is a scanning electron microscope picture of the hard carbon negative electrode material prepared in this embodiment, and it can be seen from the picture that the surface of the hard carbon negative electrode material is relatively smooth, irregular holes are distributed on the surface of the particles, meanwhile, the particle size distribution is generally 2-8 μm, the individual particle size is smaller than 1 μm, and the overall particle size distribution is relatively uniform.
FIG. 2 is a Raman spectrum of the hard carbon anode material prepared in this example, from which it can be seen that the D peak and the G peak are respectively located at 1360cm-1And 1580cm-1The overall Raman spectrum of the material is shown, and the intensity ratio of the D peak to the G peak is 0.77. The larger the intensity ratio, the larger the disorder degree of the material, and the ratio is more than 0.9 for the conventional hard carbon, and the carbon layer arrangement of the surface of the material prepared in the embodiment becomes more regular under the catalytic action of the additive, and the disorder degree is reduced, so that the intensity ratio of the D peak to the G peak in the Raman spectrum is reduced.
Fig. 3 is a first charge-discharge curve of the hard carbon negative electrode material prepared in the embodiment, and it can be seen from the curve that the discharge capacity of the hard carbon material is 586.2mAh/g, the lithium removal capacity is 499.4mAh/g, and the first coulombic efficiency reaches 85.2%, and meanwhile, the discharge curve of the material has a large amount of capacity at a voltage platform position close to 0V, which is represented as a typical hard carbon charge-discharge characteristic.
Fig. 4 is a cycle performance curve of the hard carbon negative electrode material prepared in this example, the cycle performance is the capacity retention rate of the cylindrical full battery after charging and discharging for 1000 weeks under the current density of 3C rate, and it can be seen from the figure that the material has excellent cycle stability, the capacity retention rate gradually decreases, and finally the capacity retention rate after 1000 cycles is 92.5%. In the figure, a certain fluctuation exists in the middle of the cycle curve, which is due to the capacity fluctuation caused by the temperature change of the test environment in the 1000-cycle process and belongs to a normal phenomenon.
Example 2
This example prepares a hard carbon negative electrode material as follows:
(1) placing 4.5kg of coconut shells in a pushed slab kiln under nitrogen atmosphere, heating to 500 ℃ at a heating rate of 2 ℃/min, carbonizing for 4h, cooling to 25 ℃ to obtain 1.5kg of carbonized materials, crushing, and crushing the median particle size of the materials to 6 microns to obtain a first hard carbon precursor;
(2) Mixing 1.0kg of first hard carbon precursor, 2kg of sodium chloride, 3kg of lithium chloride, 40g of nickel chloride and 40g of phosphoric acid in a VC mixer, uniformly mixing, putting into a graphite crucible, placing in a box-type furnace, heating to 750 ℃ at the heating rate of 3 ℃/min under the nitrogen atmosphere for doping and catalytic reaction, wherein the reaction time is 3h, and cooling to 25 ℃ to obtain a second hard carbon precursor;
(3) mixing the second hard carbon precursor, hydrochloric acid and water in the step (2), wherein the mass ratio of the second hard carbon precursor to the hydrochloric acid to the water is 1:1:10, soaking for 2 hours after mixing, then centrifugally washing for 2 hours, drying for 28 hours at 100 ℃, then putting 500g of the dried material into a crucible, placing the crucible into a roller kiln, heating to 1200 ℃ at a heating rate of 4 ℃/min under a nitrogen atmosphere, sintering for 3 hours, naturally cooling after sintering, demagnetizing and screening the obtained product, and thus obtaining the hard carbon negative electrode material.
The hard carbon negative electrode material prepared in this example was subjected to a structural test by the method of example 1.
The hard carbon negative electrode material prepared by the embodiment mainly comprises an inner main body and an outer layer coated on the inner main body, wherein the disorder degree of the outer layer is lower than that of the inner main body, and the inner main body and the outer layer both comprise hard carbon and doping elements doped in the hard carbon. The intensity ratio of a D peak to a G peak in a Raman spectrum of the whole hard carbon negative electrode material is 0.892, the intensity ratio of the D peak to the G peak in the Raman spectrum of the outer layer is 0.618, and the intensity ratio of the D peak to the G peak in the Raman spectrum of the inner main body is 1.24; the thickness of the outer layer is 0.1 μm; the specific surface area of the hard carbon negative electrode material is 2.15m 2(ii)/g; the doping element is phosphorus, and in the hard carbon cathode material, the mass fraction of the doping element is 0.32 wt% based on 100% of the hard carbon.
The electrochemical test and the adsorption performance decay test results of the hard carbon negative electrode material prepared in this example are shown in table 1.
Example 3
This example prepares a hard carbon negative electrode material as follows:
(1) placing walnut shells in a box furnace under nitrogen atmosphere, heating to 400 ℃ at a heating rate of 1 ℃/min, carbonizing for 8h, cooling to 20 ℃ to obtain a carbonized material, crushing the material by using a cone crusher until the median particle size is 200 mu m, and crushing the median particle size of the material to 8.0 mu m by using a fluidized bed counter-jet air flow mill to obtain a first hard carbon precursor;
(2) mixing a first hard carbon precursor, molten salt (sodium chloride) and an additive (cobalt phosphate) together in a ball mill according to a mass ratio of 1:8:0.20, uniformly mixing, putting into a graphite crucible, putting into a box-type furnace, heating to 850 ℃ at a heating rate of 2 ℃/min under a nitrogen atmosphere for doping and catalytic reaction, wherein the reaction time is 6h, and cooling to 20 ℃ to obtain a second hard carbon precursor;
(3) mixing the second hard carbon precursor, sulfuric acid and water in the step (2), wherein the mass ratio of the second hard carbon precursor to hydrochloric acid to water is 1:3:15, soaking for 1h after mixing, then centrifugally washing for 1.5h, drying for 48h at 80 ℃, then putting the dried material into a crucible, placing the crucible into a tubular furnace, heating to 1000 ℃ at a heating rate of 3 ℃/min under a nitrogen atmosphere, sintering for 4h, naturally cooling after sintering, demagnetizing and screening the obtained product to obtain the hard carbon negative electrode material.
The hard carbon negative electrode material prepared in this example was subjected to a structural test by the method of example 1.
The hard carbon negative electrode material prepared by the embodiment comprises an inner main body and an outer layer coated on the inner main body, wherein the disorder degree of the outer layer is lower than that of the inner main body, and the inner main body and the outer layer both comprise hard carbon and doping elements doped in the hard carbon. The ratio of the intensities of the D peak and the G peak in the Raman spectrum of the outer layer is 0.26, and the ratio of the intensities of the D peak and the G peak in the Raman spectrum of the inner main body is 1.15; the thickness of the outer layer is 0.7 μm; the specific surface area of the hard carbon negative electrode material is 3.56m2(ii)/g; the doping element is phosphorus, and the hard carbon cathodeIn the material, the mass fraction of the doping element is 2.13 wt% based on 100% of the mass of the hard carbon.
The electrochemical test and the adsorption performance decay test results of the hard carbon negative electrode material prepared in this example are shown in table 1.
Example 4
This example prepares a hard carbon negative electrode material as follows:
(1) placing the oil palm shells in a box type furnace under nitrogen atmosphere, heating to 800 ℃ at a heating rate of 3 ℃/min, carbonizing for 1h, cooling to 30 ℃ to obtain a carbonized material, crushing the carbonized material by using a cone crusher until the median particle size is 2000 mu m, and crushing the median particle size of the material to 15.0 mu m by using a fluidized bed jet mill to obtain a first hard carbon precursor;
(2) Mixing a first hard carbon precursor, molten salt (sodium chloride and lithium chloride) and an additive (nickel phosphate) together in a ball mill according to a mass ratio of 1:4:0.10, uniformly mixing, putting the mixture into a graphite crucible, putting the graphite crucible into a box-type furnace, heating to 700 ℃ at a heating rate of 4 ℃/min under a nitrogen atmosphere for doping and catalytic reaction, wherein the reaction time is 2 hours, and cooling to 30 ℃ to obtain a second hard carbon precursor;
(3) mixing the second hard carbon precursor, sulfuric acid and water in the step (2), wherein the mass ratio of the second hard carbon precursor to hydrochloric acid to water is 1:5:20, soaking for 4h after mixing, then centrifugally washing for 3h, drying for 6h at 150 ℃, then putting the dried material into a crucible, placing the crucible into a tubular furnace, heating to 900 ℃ at the heating rate of 5 ℃/min under the nitrogen atmosphere, sintering for 6h, naturally cooling after sintering, demagnetizing and screening the obtained product, and thus obtaining the hard carbon negative electrode material.
The hard carbon negative electrode material prepared in this example was subjected to a structural test by the method of example 1.
The hard carbon negative electrode material prepared by the embodiment mainly comprises an inner main body and an outer layer coated on the inner main body, wherein the disorder degree of the outer layer is lower than that of the inner main body, and the inner main body and the outer layer both comprise hard carbon and doping elements doped in the hard carbon. Raman light of the outer layer The ratio of the intensities of the D peak and the G peak in the spectrum is 0.54, and the ratio of the intensities of the D peak and the G peak in the Raman spectrum of the inner main body is 1.39; the thickness of the outer layer is 0.4 μm; the specific surface area of the hard carbon negative electrode material is 2.799m2(ii)/g; the doping element is phosphorus, and in the hard carbon cathode material, the mass fraction of the doping element is 1.06 wt% based on 100% of the hard carbon.
The electrochemical test and the adsorption performance decay test results of the hard carbon negative electrode material prepared in this example are shown in table 1.
Example 5
This example prepares a hard carbon negative electrode material as follows:
(1) placing epoxy resin in a box furnace under argon atmosphere, heating to 600 ℃ at a heating rate of 0.5 ℃/min, carbonizing for 5h, cooling to 25 ℃ to obtain a carbonized material, crushing the carbonized material by using an impact crusher until the median particle size is 4000 micrometers, and crushing the median particle size of the material to 20.0 micrometers by using a flat jet mill to obtain a first hard carbon precursor;
(2) mixing a first hard carbon precursor, molten salt (magnesium chloride and calcium chloride in a mass ratio of 1: 1) and an additive (nickel phosphate and ferric chloride in a mass ratio of 1: 1) together in a double-cone mixer according to a mass ratio of 1:4:0.5, uniformly mixing, putting into a graphite crucible, placing into a box-type furnace, heating to 800 ℃ at a heating rate of 1 ℃/min under an argon atmosphere for doping and catalytic reaction, wherein the reaction time is 8h, and cooling to 25 ℃ to obtain a second hard carbon precursor;
(3) Mixing the second hard carbon precursor, sulfuric acid and water in the step (2), wherein the mass ratio of the second hard carbon precursor to the sulfuric acid to the water is 1:2:10, soaking for 1h after mixing, then centrifugally washing for 1h, drying for 48h at 60 ℃, then putting the dried material into a crucible, placing the crucible into a tubular furnace, heating to 1400 ℃ at the heating rate of 2 ℃/min under the argon atmosphere, sintering for 2h, naturally cooling after sintering, demagnetizing and screening the obtained product, and thus obtaining the hard carbon cathode material.
The hard carbon negative electrode material prepared in this example was subjected to a structural test by the method of example 1.
The hard carbon negative electrode material prepared by the embodiment comprises an inner main body and an outer layer coated on the inner main body, wherein the disorder degree of the outer layer is lower than that of the inner main body, and the inner main body and the outer layer both comprise hard carbon and doping elements doped in the hard carbon. The ratio of the intensities of the D peak and the G peak in the Raman spectrum of the outer layer is 0.337, and the ratio of the intensities of the D peak and the G peak in the Raman spectrum of the inner main body is 1.217; the thickness of the outer layer is 0.8 μm; the specific surface area of the hard carbon negative electrode material is 5.451m2(ii)/g; the doping element is phosphorus, and in the hard carbon negative electrode material, the mass fraction of the doping element is 4.572 wt% based on 100% of the total mass of the hard carbon negative electrode material.
The electrochemical test and the adsorption performance decay test results of the hard carbon negative electrode material prepared in this example are shown in table 1.
Example 6
This example prepares a hard carbon negative electrode material as follows:
(1) placing epoxy resin in a box furnace under argon atmosphere, heating to 600 ℃ at a heating rate of 5 ℃/min, carbonizing for 5h, cooling to 25 ℃ to obtain a carbonized material, crushing the carbonized material by using an impact crusher until the median particle size is 10 mu m, and crushing the median particle size of the material to 5.0 mu m by using a flat jet mill to obtain a first hard carbon precursor;
(2) mixing a first hard carbon precursor, molten salt (magnesium chloride and calcium chloride in a mass ratio of 1: 1) and an additive (metaphosphoric acid and ferric nitrate in a mass ratio of 1: 1) together in a double-cone mixer according to a mass ratio of 1:3:0.3, uniformly mixing, putting into a graphite crucible, placing into a box-type furnace, heating to 500 ℃ at a heating rate of 1 ℃/min under an argon atmosphere for doping and catalytic reaction, wherein the reaction time is 0.5h, and cooling to 25 ℃ to obtain a second hard carbon precursor;
(3) mixing the second hard carbon precursor, sulfuric acid and water in the step (2), wherein the mass ratio of the second hard carbon precursor to the sulfuric acid to the water is 1:2:10, soaking for 10 hours after mixing, then centrifugally washing for 4 hours, drying for 12 hours at 200 ℃, then putting the dried material into a crucible, placing the crucible into a tubular furnace, heating to 1400 ℃ at the heating rate of 8 ℃/min under the argon atmosphere, sintering for 2 hours, naturally cooling after sintering, demagnetizing and screening the obtained product, and thus obtaining the hard carbon cathode material.
The hard carbon negative electrode material prepared in this example was subjected to a structural test by the method of example 1.
The hard carbon negative electrode material prepared by the embodiment comprises an inner main body and an outer layer coated on the inner main body, wherein the disorder degree of the outer layer is lower than that of the inner main body, and the inner main body and the outer layer both comprise hard carbon and doping elements doped in the hard carbon. The ratio of the intensities of the D peak and the G peak in the Raman spectrum of the outer layer is 0.693, and the ratio of the intensities of the D peak and the G peak in the Raman spectrum of the inner main body is 1.237; the thickness of the outer layer is 0.6 μm; the specific surface area of the hard carbon negative electrode material is 4.571m2(ii)/g; the doping elements are nitrogen and chlorine, and in the hard carbon negative electrode material, the mass fraction of the doping elements is 2.679 wt% based on 100% of the total mass of the hard carbon negative electrode material.
The electrochemical test and the adsorption performance decay test results of the hard carbon negative electrode material prepared in this example are shown in table 1.
Example 7
The specific method for preparing the hard carbon anode material in the embodiment refers to the embodiment 1, except that in the step (1), the median particle size of the material is 6 μm; in the step (2), the mass ratio of the first hard carbon precursor to the molten salt (potassium chloride and lithium chloride in a mass ratio of 1: 1) to the additive (iron phosphate) is 1:2:0.01, and the heating rate is 0.5 ℃/min; in the step (3), the centrifugal washing time is 6h, and the heating rate is 1 ℃/min.
The hard carbon negative electrode material prepared in this example was subjected to a structural test by the method of example 1.
The hard carbon negative electrode material prepared by the embodiment comprises an inner main body and an outer layer coated on the inner main body, wherein the disorder degree of the outer layer is lower than that of the inner main body, and the inner main body and the outer layer both comprise hard carbon and doping elements doped in the hard carbon. The ratio of the D peak intensity to the G peak intensity in the Raman spectrum of the outer layer is0.527, the internal body having a raman spectrum with a D peak to G peak intensity ratio of 1.225; the thickness of the outer layer is 0.2 μm; the specific surface area of the hard carbon negative electrode material is 4.596m2(ii)/g; the doping element is phosphorus, and in the hard carbon negative electrode material, the mass fraction of the doping element is 0.334 wt% based on 100% of the total mass of the negative electrode material.
The electrochemical test and the adsorption performance decay test results of the hard carbon negative electrode material prepared in this example are shown in table 1.
Example 8
The specific method for preparing a hard carbon negative electrode material in this example refers to example 1, except that in step (1), the median particle size of the material is set to 13.0 μm; in the step (2), the mass ratio of the first hard carbon precursor to the molten salt (potassium chloride and lithium chloride in a mass ratio of 1: 1) to the additive (iron phosphate) is 1:2:0.03, and the heating rate is 10 ℃/min; in the step (3), the centrifugal washing time is 0.5h, and the heating rate is 10 ℃/min.
The hard carbon negative electrode material prepared in this example was subjected to a structural test by the method of example 1.
The hard carbon negative electrode material prepared by the embodiment comprises an inner main body and an outer layer coated on the inner main body, wherein the disorder degree of the outer layer is lower than that of the inner main body, and the inner main body and the outer layer both comprise hard carbon and doping elements doped in the hard carbon. The ratio of the intensity of the D peak to the intensity of the G peak in the Raman spectrum of the outer layer is 0.416, and the ratio of the intensity of the D peak to the intensity of the G peak in the Raman spectrum of the inner main body is 1.241; the thickness of the outer layer is 0.3 μm; the specific surface area of the hard carbon negative electrode material is 2.124m2(ii)/g; the doping elements are phosphorus and chlorine, and in the hard carbon cathode material, the mass fraction of the doping elements is 0.782 wt% based on 100% of the total mass of the hard carbon cathode material.
The electrochemical test and the adsorption performance decay test results of the hard carbon negative electrode material prepared in this example are shown in table 1.
Example 9
This example describes a specific method for preparing a hard carbon negative electrode material, with reference to example 1, except that the iron phosphate in step (2) was replaced with equal mass of ferric chloride.
The hard carbon negative electrode material prepared in this example was subjected to a structural test by the method of example 1.
The hard carbon negative electrode material prepared by the embodiment comprises an inner main body and an outer layer coated on the inner main body, wherein the disorder degree of the outer layer is lower than that of the inner main body, and the inner main body and the outer layer both comprise hard carbon. The intensity ratio of a D peak to a G peak in a Raman spectrum of the whole hard carbon negative electrode material is 0.75, the intensity ratio of the D peak to the G peak in the Raman spectrum of the outer layer is 0.28, and the intensity ratio of the D peak to the G peak in the Raman spectrum of the inner main body is 1.05; the thickness of the outer layer is 0.55 μm; the specific surface area of the hard carbon negative electrode material is 2.135m2(ii) in terms of/g. The hard carbon negative electrode material provided by the embodiment does not contain doping elements.
The electrochemical test and the adsorption performance decay test results of the hard carbon negative electrode material prepared in this example are shown in table 1.
Comparative example 1
The specific production method of this comparative example refers to example 1 except that the operation of step (2), i.e., the doping and catalytic reaction, is not performed.
The hard carbon negative electrode material prepared by the comparative example does not contain doping elements, and the negative electrode material does not have an outer layer and an inner main body with different degrees of disorder, and the degrees of disorder are uniform.
The electrochemical test and the adsorption performance attenuation test results of the hard carbon negative electrode material prepared in the comparative example are shown in table 1.
Comparative example 2
The specific preparation method of this comparative example refers to example 1, except that no additive iron phosphate was added in step (2).
The hard carbon negative electrode material prepared by the comparative example does not contain doping elements, and the negative electrode material does not have an outer layer and an inner main body with different degrees of disorder, and the degrees of disorder are uniform.
The electrochemical test and the adsorption performance attenuation test results of the hard carbon negative electrode material prepared in the comparative example are shown in table 1.
Comparative example 3
The specific preparation process of this comparative example is as in example 1, except that no molten salts potassium chloride and lithium chloride are added in step (2), i.e., no molten salt system is used.
The hard carbon negative electrode material of the comparative example does not have an outer layer and an inner main body with different disorder degrees, the disorder degrees are uniform, and the material contains a certain content of doping elements.
The electrochemical test and the adsorption performance attenuation test results of the hard carbon negative electrode material prepared in the comparative example are shown in table 1.
Electrochemical test and adsorption performance decay test methods:
after the hard carbon negative electrode materials obtained in the above examples and comparative examples are prepared into batteries, electrochemical performance tests and adsorption performance decay tests are performed.
The preparation of the button cell is carried out by adopting a method known in the field: adjusting the negative electrode material, the conductive agent and the binder to a solid content of 50% by mass with distilled water according to a mass ratio of 91:3:6, uniformly mixing, coating on a copper foil current collector, and drying in vacuum to obtain a negative electrode plate; a lithium sheet is taken as a counter electrode, 1mol/L LiPF6/EC + DMC + EMC (v/v is 1:1:1) is taken as electrolyte, Celgrad2400 is taken as a diaphragm, and a 2016 button cell shell is adopted as a shell.
The preparation method of the specific cylindrical battery comprises the following steps: dispersing the negative electrode material, the conductive agent and the binder in a solvent according to the mass percentage of 94:1:5, uniformly mixing, controlling the solid content to be 50%, coating the mixture on a copper foil current collector, and drying in vacuum to obtain a negative electrode piece; then, a lithium cobaltate positive pole piece prepared by a traditional mature process, 1mol/L LiPF6/EC + DMC + EMC (v/v is 1:1:1) electrolyte, a Celgard2400 diaphragm and an outer shell are assembled into the 18650 cylindrical single-cell battery by adopting a conventional production process.
The first reversible capacity and the first coulombic efficiency of the hard carbon negative electrode materials prepared in the examples and the comparative examples are tested by using a button cell, and the specific test conditions are as follows: the test is carried out on a LAND battery test system of Wuhanjinnuo electronic Limited company, wherein 0.1C is discharged, the cut-off voltage is 1mV, and then 0.1C is charged, and the cut-off voltage is 1.5V.
The test of the absorption performance attenuation is to prepare the button cell by the method after the hard carbon negative electrode materials obtained in the embodiments and the comparative examples are placed in the air for 30 days, and test is carried out according to the conditions of testing the first reversible capacity and the first coulombic efficiency.
The 1C @1000 cycle performance of the hard carbon anode materials of the examples and the comparative examples is tested by using a cylindrical battery, and the specific test conditions are as follows: the test is carried out on a LAND battery test system of Wuhanjinnuo electronic Limited company, the charging and discharging are sequentially activated for 2 weeks at the multiplying power of 0.1C, 0.2C and 0.5C, then the charging and discharging multiplying power is increased to 1C, and the cycle performance is carried out under the condition of normal temperature.
The results of the above tests are shown in Table 1.
TABLE 1
It can be seen from the above examples and comparative examples that the hard carbon negative electrode materials provided in examples 1 to 8 of the present invention have both the doping element and the outer layer with a low disorder degree, so that the electrochemical properties in the aspects of the first reversible capacity, the first coulombic efficiency, the cycle capacity retention rate, etc. are all very excellent, and the degradation degree of the properties after the materials are left in the air is greatly reduced.
The hard carbon negative electrode material provided in example 9 does not contain doping elements, and therefore, the electrochemical properties such as capacity and first effect cannot be improved by doping nitrogen and phosphorus, and thus example 9 is inferior to the product of example 1 in capacity and first effect.
Comparative example 1 is inferior to example 1 in terms of first reversible capacity, first coulombic efficiency, 1000 cycle capacity retention rate, reversible capacity after standing for 30 days, and first coulombic efficiency of the material after standing for 30 days, which is probably because comparative example 1 is neither doped nor catalyzed, and thus the product of comparative example 1 is not subjected to a process of forming carbide from a metal cation and a carbon material and then decomposing the carbide to rearrange a carbon skeleton, and is not doped with a non-metal element, and thus the tested performances are inferior to those of example 1.
Comparative example 2 is inferior to example 1 in terms of first reversible capacity, first coulombic efficiency, 1000 cycle capacity retention ratio, reversible capacity after being left for 30 days, and first coulombic efficiency of the material after being left for 30 days, which is probably because no additive is added in comparative example 2, although comparative example 2 is subjected to heat treatment in a molten salt system, the additive is the key for allowing catalytic reaction and doping to be performed, metal cations in the additive play a catalytic role, non-metal elements play a doping role, comparative example 2 is not added with the additive, and the product is not subjected to catalytic modification and doping, so that the product is inferior to the product of example 1 in various performances tested.
Comparative example 3 is inferior to example 1 in terms of first reversible capacity, first coulombic efficiency, 1000 cycle capacity retention rate, reversible capacity after standing for 30 days, and first coulombic efficiency of the material after standing for 30 days, which is probably because no molten salt system is added in comparative example 3, and the final catalytic and doping effects of the additive are realized under the assistance of molten salt, and the comparative example 3 is not added with a molten salt system, although the additive plays a certain doping effect, the catalytic modification effect is limited, so that the performance of the test is inferior to that of the product of example 1.
The applicant states that the present invention is illustrated by the above examples to show the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, i.e. it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. The hard carbon negative electrode material is characterized by comprising an inner main body and an outer layer coated on the inner main body, wherein the disorder degree of the outer layer is lower than that of the inner main body, and the inner main body and the outer layer both comprise hard carbon.
2. The hard carbon negative electrode material as claimed in claim 1, wherein the ratio of the intensities of the D peak and the G peak in the Raman spectrum of the outer layer is 0.2-0.7;
preferably, the ratio of D peak/G peak in Raman spectrum of the inner main body is 0.7-1.5;
preferably, the thickness of the outer layer is 0 to 1 μm and does not contain 0.
3. The hard carbon negative electrode material as claimed in claim 1 or 2, wherein the specific surface area of the hard carbon negative electrode material is 1-20 m 2A preferred range is 1.5 to 15m2/g；
Preferably, the median particle size of the hard carbon negative electrode material is 4.0-30.0 μm, preferably 5.0-20.0 μm, and further preferably 6.0-15.0 μm;
preferably, the inner body and the outer layer of the hard carbon negative electrode material both comprise hard carbon and a doping element doped in the hard carbon;
preferably, in the hard carbon negative electrode material, the doping element comprises phosphorus and/or nitrogen;
preferably, in the hard carbon negative electrode material, the mass fraction of the doping elements is 0.3-5 wt% based on 100% of the total mass of the hard carbon negative electrode material.
4. A method for preparing the hard carbon negative electrode material according to any one of claims 1 to 3, comprising the steps of:
(1) mixing the first hard carbon precursor, the additive and the molten salt, and then carrying out catalytic reaction to obtain a second hard carbon precursor;
(2) and (3) purifying the second hard carbon precursor in the step (1), and sintering to obtain the hard carbon negative electrode material.
5. The method according to claim 4, wherein in the step (1), the method for preparing the first hard carbon precursor comprises: carbonizing a hard carbon raw material, and then crushing to obtain a first hard carbon precursor;
Preferably, the hard charcoal raw material comprises a biomass raw material and/or a thermoplastic resin raw material;
preferably, the biomass raw material comprises any one or a combination of at least two of coconut shells, apricot shells, walnut shells and oil palm shells;
preferably, the thermoplastic resin raw material comprises any one or a combination of at least two of epoxy resin, phenolic resin, carboxymethyl cellulose, ethyl methyl carbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate or polytetrafluoroethylene;
preferably, the carbonization is carried out under a protective atmosphere;
preferably, the protective atmosphere is any one of nitrogen, helium, neon, argon, krypton or xenon or a combination of at least two of the same;
preferably, the carbonization temperature is 400-800 ℃;
preferably, the carbonization time is 1-8 h;
preferably, the temperature rise rate of the carbonization is 0.5-5 ℃/min, preferably 1-3 ℃/min;
preferably, after carbonization, the mixture is cooled to 20-30 ℃ and then crushed;
preferably, the carbonization is performed in any one of a vacuum furnace, a box furnace, a rotary furnace, a roller kiln, a pusher kiln, or a tube furnace;
preferably, the apparatus for performing the comminution comprises a crusher and/or a jet mill, preferably a combination of a crusher and a crusher;
Preferably, the crusher comprises any one of a jaw crusher, a cone crusher, an impact crusher, a counterimpact crusher or a hammer crusher or a combination of at least two thereof;
preferably, the pulverizer comprises any one of or a combination of at least two of a flat jet mill, a fluidized bed counter-jet mill, a circulating tube jet mill, a counter-jet mill or a target jet mill;
preferably, when the equipment for crushing is a combination of a crusher and a crusher, the crusher is used for crushing the material to a median particle size of 10-4000 μm, preferably 200-2000 μm, and then the crusher is used for crushing the material to a median particle size;
preferably, in the step (1), the median particle diameter of the first hard carbon precursor is 4.0-30.0 μm, preferably 5.0-20.0 μm, and more preferably 6.0-15.0 μm.
6. The production method according to claim 4 or 5, wherein in the step (1), a metal cation is contained in the additive;
preferably, the additive comprises any one of or a combination of at least two of a salt compound of iron, a salt compound of cobalt or a salt compound of nickel;
preferably, the additive comprises nitrate and/or phosphate in addition to the metal cation;
Preferably, the additive comprises any one of iron phosphate, cobalt phosphate, nickel phosphate, iron nitrate, cobalt nitrate or nickel nitrate or a combination of at least two of the above;
preferably, the additive comprises a nitrate-or phosphate-free metal salt and a nitrate-or phosphate-containing substance;
preferably, the nitrate-or phosphate-free metal salt includes any one of iron acetate, iron chloride, cobalt acetate, cobalt chloride, nickel acetate, nickel chloride, or a combination of at least two thereof;
preferably, in step (1), the molten salt comprises any one of potassium chloride, sodium chloride, lithium chloride, magnesium chloride or calcium chloride or a combination of at least two of them;
preferably, in step (1), the mixing is carried out in a mixing device;
preferably, the mixing device comprises any one of a VC mixer, a ball mill or a double-cone mixer;
preferably, in the step (1), the mass ratio of the first hard carbon precursor to the molten salt to the additive is 1 (2-10) to (0.01-0.5), and preferably 1 (3-8) to (0.03-0.3);
preferably, the catalytic reaction of step (1) is carried out under a protective atmosphere;
preferably, the protective atmosphere is any one of nitrogen, helium, neon, argon, krypton or xenon or a combination of at least two of the same;
Preferably, the catalytic reaction is carried out in any one of a vacuum furnace, a box furnace, a rotary furnace, a roller kiln, a pushed slab kiln or a tubular furnace;
preferably, the reaction temperature of the catalytic reaction is 500-1000 ℃;
preferably, the reaction time of the catalytic reaction is 0.5-8 h, preferably 1-6 h;
preferably, the temperature rise rate of the catalyst reaction is 0.5-10 ℃/min, preferably 1-6 ℃/min, and more preferably 2-4 ℃/min.
7. The production method according to any one of claims 4 to 6, wherein in the step (2), the purification method comprises: mixing the second hard carbon precursor in the step (1), acid and water, soaking, then centrifugally washing, and drying the obtained solid substance;
preferably, the acid comprises any one of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, or hydrofluoric acid, or a combination of at least two thereof;
preferably, the mass ratio of the second hard carbon precursor to the acid to the water is 1 (0.5-5) to 2-20;
preferably, the soaking time is 1-10 hours, preferably 1-4 hours;
preferably, the centrifugal washing time is 0.5-6 h, preferably 1-4 h, and further preferably 1.5-3 h;
Preferably, the drying is performed in any one of a vacuum drying oven, a forced air drying oven, a box furnace, a rotary kiln or a double-cone dryer;
preferably, the drying temperature is 60-200 ℃, and preferably 80-150 ℃;
preferably, the drying time is 6-48 h;
preferably, in step (2), the sintering is performed under a protective atmosphere;
preferably, the protective atmosphere is any one of nitrogen, helium, neon, argon, krypton or xenon or a combination of at least two of the same;
preferably, the sintering is performed in any one of a vacuum furnace, a box furnace, a rotary furnace, a roller kiln, a pusher kiln or a tube furnace;
preferably, the sintering temperature is 900-1400 ℃;
preferably, the sintering time is 2-8 h, preferably 3-6 h;
preferably, the temperature rise rate of the sintering is 0.5-10 ℃/min, preferably 1-6 ℃/min;
preferably, the preparation method further comprises: refining the hard carbon negative electrode material obtained in the step (2);
preferably, the refining comprises demagnetization and sieving.
8. The method for preparing according to any one of claims 4 to 7, characterized in that it comprises the steps of:
(1) Heating a hard carbon raw material to 400-800 ℃ at a heating rate of 1-3 ℃/min under a protective atmosphere, carbonizing for 1-8 h, cooling to 20-30 ℃, crushing, and crushing the median particle size of the material to 6.0-15.0 mu m to obtain a first hard carbon precursor;
(2) mixing a first hard carbon precursor, an additive and molten salt, wherein the mass ratio of the first hard carbon precursor to the molten salt to the additive is (1), (3-8): (0.03-0.3), heating to 500-1000 ℃ at a heating rate of 2-4 ℃/min under a protective atmosphere after mixing, and carrying out doping and catalytic reaction for 1-6 h to obtain a second hard carbon precursor;
wherein the additive comprises any one or the combination of at least two of iron salt compound, cobalt salt compound or nickel salt compound; and the additive comprises nitrate and/or phosphate besides metal cations; the molten salt comprises any one or the combination of at least two of potassium chloride, sodium chloride, lithium chloride, magnesium chloride or calcium chloride;
(3) mixing the second hard carbon precursor, acid and water in the step (2), wherein the mass ratio of the second hard carbon precursor to the acid to the water is 1: (0.5-5): (2-20), soaking for 1-4 h after mixing, then centrifugally washing for 1.5-3 h, drying for 6-48 h at 80-150 ℃, then heating to 900-1400 ℃ at a heating rate of 3-5 ℃/min under a protective atmosphere, sintering for 3-6 h, and demagnetizing and screening the obtained product after sintering to obtain the hard carbon negative electrode material.
9. A pole piece comprising the hard carbon negative electrode material of any one of claims 1 to 3.
10. A lithium ion battery comprising the hard carbon negative electrode material according to any one of claims 1 to 3.
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Cited By (3)
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| CN113113601A (en) * | 2021-04-06 | 2021-07-13 | 常德速碳新能源科技有限公司 | Hard carbon negative electrode material for lithium ion secondary battery and preparation method thereof |
| CN115872403A (en) * | 2022-12-13 | 2023-03-31 | 溧阳紫宸新材料科技有限公司 | Porous carbon material and preparation method and application thereof |
| CN117410480A (en) * | 2023-12-13 | 2024-01-16 | 湖南镕锂新材料科技有限公司 | Hard carbon negative electrode material of lithium battery |
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