CN117393738B - Negative electrode material and preparation method thereof - Google Patents
Negative electrode material and preparation method thereof Download PDFInfo
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- CN117393738B CN117393738B CN202311637045.5A CN202311637045A CN117393738B CN 117393738 B CN117393738 B CN 117393738B CN 202311637045 A CN202311637045 A CN 202311637045A CN 117393738 B CN117393738 B CN 117393738B
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- 239000007773 negative electrode material Substances 0.000 title claims abstract description 26
- 238000002360 preparation method Methods 0.000 title description 12
- 239000010410 layer Substances 0.000 claims abstract description 53
- 229910021385 hard carbon Inorganic materials 0.000 claims abstract description 38
- 239000010405 anode material Substances 0.000 claims abstract description 33
- 239000011148 porous material Substances 0.000 claims abstract description 32
- 239000011229 interlayer Substances 0.000 claims abstract description 12
- 238000003756 stirring Methods 0.000 claims description 71
- 239000011259 mixed solution Substances 0.000 claims description 58
- 229920000642 polymer Polymers 0.000 claims description 33
- 238000004321 preservation Methods 0.000 claims description 31
- 239000000243 solution Substances 0.000 claims description 31
- 239000002245 particle Substances 0.000 claims description 25
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 24
- 159000000000 sodium salts Chemical class 0.000 claims description 23
- GHMLBKRAJCXXBS-UHFFFAOYSA-N resorcinol Chemical compound OC1=CC=CC(O)=C1 GHMLBKRAJCXXBS-UHFFFAOYSA-N 0.000 claims description 22
- 229910052708 sodium Inorganic materials 0.000 claims description 21
- 239000011734 sodium Substances 0.000 claims description 21
- 238000009826 distribution Methods 0.000 claims description 20
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 20
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 19
- 229920003171 Poly (ethylene oxide) Polymers 0.000 claims description 18
- 239000003795 chemical substances by application Substances 0.000 claims description 18
- 239000000395 magnesium oxide Substances 0.000 claims description 18
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 17
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 17
- 238000001291 vacuum drying Methods 0.000 claims description 17
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical group [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims description 16
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 claims description 15
- 239000002253 acid Substances 0.000 claims description 15
- 238000000034 method Methods 0.000 claims description 15
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 14
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 14
- 239000003513 alkali Substances 0.000 claims description 14
- -1 sodium bis-fluorosulfonyl imide Chemical class 0.000 claims description 11
- 150000002500 ions Chemical class 0.000 claims description 10
- 238000002156 mixing Methods 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 9
- 230000000630 rising effect Effects 0.000 claims description 7
- 239000000377 silicon dioxide Substances 0.000 claims description 7
- 239000007833 carbon precursor Substances 0.000 claims description 6
- 238000005406 washing Methods 0.000 claims description 6
- 239000002994 raw material Substances 0.000 claims description 4
- 239000002028 Biomass Substances 0.000 claims description 3
- 229910021536 Zeolite Inorganic materials 0.000 claims description 3
- 239000003245 coal Substances 0.000 claims description 3
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 claims description 3
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 claims description 3
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 3
- 239000011295 pitch Substances 0.000 claims description 3
- 229920005989 resin Polymers 0.000 claims description 3
- 239000011347 resin Substances 0.000 claims description 3
- 235000012239 silicon dioxide Nutrition 0.000 claims description 3
- KKCBUQHMOMHUOY-UHFFFAOYSA-N sodium oxide Chemical class [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 claims description 3
- 239000010457 zeolite Substances 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims 2
- 238000007600 charging Methods 0.000 abstract description 4
- 238000013461 design Methods 0.000 abstract description 4
- 238000005253 cladding Methods 0.000 abstract description 2
- 229910001415 sodium ion Inorganic materials 0.000 description 45
- 239000000463 material Substances 0.000 description 26
- 230000000052 comparative effect Effects 0.000 description 25
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 11
- 239000003792 electrolyte Substances 0.000 description 11
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 10
- 230000005012 migration Effects 0.000 description 10
- 238000013508 migration Methods 0.000 description 10
- 230000000694 effects Effects 0.000 description 9
- XXYVTWLMBUGXOK-UHFFFAOYSA-N [Na].FS(=N)F Chemical compound [Na].FS(=N)F XXYVTWLMBUGXOK-UHFFFAOYSA-N 0.000 description 8
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 8
- 229910052593 corundum Inorganic materials 0.000 description 7
- 230000008569 process Effects 0.000 description 7
- 229910001845 yogo sapphire Inorganic materials 0.000 description 7
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 230000009286 beneficial effect Effects 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 5
- 238000007086 side reaction Methods 0.000 description 5
- VCCATSJUUVERFU-UHFFFAOYSA-N sodium bis(fluorosulfonyl)azanide Chemical compound FS(=O)(=O)N([Na])S(F)(=O)=O VCCATSJUUVERFU-UHFFFAOYSA-N 0.000 description 5
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 4
- 239000002033 PVDF binder Substances 0.000 description 4
- 239000002202 Polyethylene glycol Substances 0.000 description 4
- 239000004372 Polyvinyl alcohol Substances 0.000 description 4
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- 210000004027 cell Anatomy 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 238000011161 development Methods 0.000 description 4
- 238000004146 energy storage Methods 0.000 description 4
- 229910001416 lithium ion Inorganic materials 0.000 description 4
- 229920003229 poly(methyl methacrylate) Polymers 0.000 description 4
- 229920002239 polyacrylonitrile Polymers 0.000 description 4
- 229920001223 polyethylene glycol Polymers 0.000 description 4
- 239000004926 polymethyl methacrylate Substances 0.000 description 4
- 229920002451 polyvinyl alcohol Polymers 0.000 description 4
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 4
- 238000005245 sintering Methods 0.000 description 4
- 229910021201 NaFSI Inorganic materials 0.000 description 3
- KEAYESYHFKHZAL-UHFFFAOYSA-N Sodium Chemical compound [Na] KEAYESYHFKHZAL-UHFFFAOYSA-N 0.000 description 3
- QXZNUMVOKMLCEX-UHFFFAOYSA-N [Na].FC(F)(F)S(=O)(=O)NS(=O)(=O)C(F)(F)F Chemical compound [Na].FC(F)(F)S(=O)(=O)NS(=O)(=O)C(F)(F)F QXZNUMVOKMLCEX-UHFFFAOYSA-N 0.000 description 3
- 239000003575 carbonaceous material Substances 0.000 description 3
- 238000010277 constant-current charging Methods 0.000 description 3
- 210000001787 dendrite Anatomy 0.000 description 3
- 238000009830 intercalation Methods 0.000 description 3
- 230000002687 intercalation Effects 0.000 description 3
- 230000014759 maintenance of location Effects 0.000 description 3
- 230000002441 reversible effect Effects 0.000 description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- UIIMBOGNXHQVGW-DEQYMQKBSA-M Sodium bicarbonate-14C Chemical compound [Na+].O[14C]([O-])=O UIIMBOGNXHQVGW-DEQYMQKBSA-M 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 2
- 150000001450 anions Chemical class 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 230000001627 detrimental effect Effects 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000010494 dissociation reaction Methods 0.000 description 2
- 230000005593 dissociations Effects 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 238000006116 polymerization reaction Methods 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 235000017550 sodium carbonate Nutrition 0.000 description 2
- 235000011121 sodium hydroxide Nutrition 0.000 description 2
- 239000001488 sodium phosphate Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- RYFMWSXOAZQYPI-UHFFFAOYSA-K trisodium phosphate Chemical compound [Na+].[Na+].[Na+].[O-]P([O-])([O-])=O RYFMWSXOAZQYPI-UHFFFAOYSA-K 0.000 description 2
- 235000019801 trisodium phosphate Nutrition 0.000 description 2
- 229910000406 trisodium phosphate Inorganic materials 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 235000013162 Cocos nucifera Nutrition 0.000 description 1
- 244000060011 Cocos nucifera Species 0.000 description 1
- 108010052164 Sodium Channels Proteins 0.000 description 1
- 102000018674 Sodium Channels Human genes 0.000 description 1
- 230000005856 abnormality Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 230000009477 glass transition Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 235000010755 mineral Nutrition 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000009828 non-uniform distribution Methods 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 150000003385 sodium Chemical class 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000002345 surface coating layer Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
- 230000037303 wrinkles Effects 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
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- 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
- H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
-
- 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
- H01M4/04—Processes of manufacture in general
- H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
-
- 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
- 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
-
- 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
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
-
- 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
Abstract
The invention discloses a negative electrode material, which has a double-layer structure of an outer layer and an inner core, wherein the inner core is hard carbon, the outer layer is porous hard carbon, and the inner surface of the porous structure of the porous hard carbon is coated with a high ion conductivity layer. The invention designs the structure of the anode material, and mainly builds the anode material through a series of structures such as microstructure-interlayer spacing, macrostructure-double-layer structure, pore structure, surface modification-cladding of the anode material and the like, so as to obtain the anode material with high initial efficiency, high charging rate performance and high cycle performance.
Description
Technical Field
The invention relates to the field of materials, in particular to a negative electrode material for a sodium ion battery and a preparation method thereof.
Background
With the development of human society, the demand for energy is increasing, and the energy problem becomes urgent to solve the obtained problem. Thanks to the gradual achievement of the consensus of the international society and the gradual implementation of the national policy, new energy industry technology is rapidly advancing, wherein energy storage becomes an important one. Lithium ion batteries are becoming an extremely important energy storage medium in the market at a very wide angle and rapidly developing in a short time due to their excellent performance, and can partially replace fossil energy. However, the lithium ion battery still has the problem of resource limitation because the raw material lithium ore is used as a mineral energy source, and lithium resources are in shortage in the near future under the current rapid development environment of power batteries and energy storage. The sodium resource has the characteristics of abundant reserves, wide distribution, simple extraction and the like. The sodium ion battery is widely focused due to the advantages of relatively good energy density, good safety, excellent low-temperature performance and the like, can form a complementary effect with the lithium ion battery, has foreseeable long-term development in the fields of electric tools, two-wheelers, low-speed electric vehicles and energy storage, and therefore, the research of the sodium ion battery greatly promotes the rapid development of new energy industries.
Hard carbon is an important strategic place as the main negative electrode material for sodium ion batteries. Compared with lithium ions, sodium ions migrate relatively slowly in the hard carbon material due to larger ionic radius, sodium ions are easily reduced on the surface of the hard carbon material under the condition of high multiplying power in the charging process, so that sodium ions are converted into sodium metal, along with the progress of the reaction, sodium metal is continuously generated and forms clusters at certain positions which are easy to accumulate, and in long-time recycling, sodium metal is converted into sodium dendrites to generate serious side reaction with electrolyte, so that the interface between the material and the electrolyte is deteriorated, the recycling performance is deteriorated or water is jumped, and potential safety hazards are possibly formed by puncturing a diaphragm. In addition, there is a certain requirement for uniformity and flatness of the hard carbon negative electrode, and when there is a small abnormality such as local uneven surface density, the occurrence of sodium precipitation reaction is aggravated by membrane wrinkles and the like.
Disclosure of Invention
Aiming at the problems in the prior art, the invention discloses a negative electrode material which is beneficial to migration and diffusion of sodium ions, thereby reducing the formation of sodium dendrites; the negative electrode material is used in a battery, and can improve the cycle performance and the safety performance of the battery.
The invention is realized by the following technical scheme:
the negative electrode material provided by the invention has a double-layer structure of an outer layer and an inner core, wherein the inner core is hard carbon, the outer layer is porous hard carbon, and the inner surface of the porous structure of the porous hard carbon is coated with a high ion conductivity layer.
As a further option, the outer layer has at least 1 and at most 3 pore structures in the direction of thickness.
As a further aspect, the porous hard carbon has a pore size distribution of 200nm to 500nm.
As a further scheme, the half-width of the pore diameter distribution is 100nm-200nm.
As a further aspect, the microcrystalline interlayer spacing of the anode material is 0.37nm to 0.41nm.
As a still further aspect, the microcrystalline interlayer spacing of the anode material is 0.38nm to 0.4nm.
The microcrystalline interlayer spacing of the anode material in the invention is the carbon layer interlayer spacing of the anode material.
As a further alternative, the particle size D50 of the inner core is 3 μm to 9. Mu.m.
As a further scheme, the raw materials of the high ion conductivity layer comprise sodium salt, polymer and oxide.
As a still further aspect, the sodium salt comprises one or more of sodium hexafluorophosphate, sodium bis (trifluoromethylsulfonyl) imide.
As a still further aspect, the polymer comprises one or more of polyethylene oxide, polymethyl methacrylate, polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polyethylene glycol.
As a still further aspect, the oxide includes one or more of magnesia, silica, and alumina.
As a further scheme, the mass ratio of the sodium salt to the polymer to the oxide is (0.01-0.2) 1 (0.001-0.05).
As a further scheme, the sodium salt is sodium bis-fluorosulfonyl imide, the polymer is polyethylene oxide, and the oxide is magnesium oxide; the mass ratio of the sodium bis (fluorosulfonyl imide), the polyethylene oxide and the magnesium oxide is (0.01-0.2) 1 (0.001-0.05). On the one hand, the sodium bis (fluorosulfonyl) imide supports rapid migration of sodium ions in the polymer layer, and the magnesium oxide can reduce the polymerization degree of polyethylene oxide, so that the migration of sodium ions is facilitated, and on the other hand, the polyethylene oxide can rapidly solve the sodium ions in the sodium bis (fluorosulfonyl) imide, so that the sodium ions are uniformly dispersed.
The invention also provides a preparation method of the anode material, which comprises the following steps:
S1: presintering the hard carbon precursor to form an intermediate 1;
s2: adding resorcinol and formaldehyde into an ethanol solution, adding ammonia water, and finally adding a template agent to form a mixed solution 1;
s3: placing the intermediate 1 into the mixed solution 1, stirring, then carrying out heat preservation at 70-90 ℃ for 1-2h, then carrying out heat preservation at 400-800 ℃ for 1-3 h, and finally carrying out heat preservation at 900-1250 ℃ for 1-3 h; acid washing and alkali washing to obtain an intermediate 2;
s4: dissolving a polymer in a dimethylacetamide solution, stirring, and then adding sodium salt and oxide to obtain a mixed solution 2;
s5: and mixing the intermediate 2 with the mixed solution 2, and vacuum drying to obtain the anode material.
As a further aspect, the hard carbon precursor comprises one or more of biomass, pitch, resin, coal-based.
As a further aspect, the sodium salt comprises one or more of sodium hexafluorophosphate, sodium bis (trifluoromethylsulfonyl) imide.
As a further aspect, the polymer comprises one or more of polyethylene oxide, polymethyl methacrylate, polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polyethylene glycol.
As a further aspect, the oxide includes one or more of magnesia, silica, and alumina.
As a further aspect, the template agent includes one or more of zeolite, silica, and alumina.
As a still further aspect, the particle size of the template particles is in the range of 100nm to 400nm, preferably 100nm to 300nm. Is related to the pore size formed in the anode material.
As a further scheme, the ammonia water is 25% ammonia water. 25% of the 25% aqueous ammonia represents the concentration of aqueous ammonia.
As a further aspect, the acid includes one or more of hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid.
As a further scheme, the alkali comprises one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonia water and trisodium phosphate.
As a further scheme, the presintering condition in the step S1 is that the temperature is 300-600 ℃, and the temperature is kept for 1-3 h.
As a further scheme, the temperature rise rate to the temperature of the pre-sintering is 1 ℃/min to 5 ℃/min.
As a further alternative, in order to obtain anode material particles having a certain particle diameter, the crushing treatment may be performed when the intermediate 1 is obtained, and the size of the crushed particles may be selected by those skilled in the art according to their own actual demands.
As a further scheme, the mass ratio of the ethanol in the ethanol solution in the S2 is 60% -90%. In the present invention, the ethanol solution is used for dissolution, and a person skilled in the art may add an appropriate amount according to the actual situation, and may dissolve the substance added to the ethanol solution.
As a further scheme, the mass ratio of resorcinol, formaldehyde, ammonia water and template agent in the S2 is 1 (1.02-1.2) (0.9-1.2) (0.01-0.2).
As a further scheme, stirring is needed after the template agent is added in the S2, and the stirring time is 15-20 h.
In the step S2, resorcinol and formaldehyde may be added to the ethanol solution and then stirred for a period of time which may be selected by those skilled in the art according to the actual situation, in order to promote uniformity of the ethanol solution among the substances. The following is a preferred example, stirring for 25min-35min. Similarly, stirring may be performed after adding ammonia water, and the stirring time may be selected by those skilled in the art according to the actual situation. The following is a preferred example, stirring for 8min-12min.
As a further scheme, the mass ratio of the intermediate 1 in the mixed solution 1 in the step S3 to the resorcinol in the mixed solution 1 is (0.05-0.2): 1.
As a further scheme, the stirring time in the step S3 is 2-5 h.
As a further scheme, the temperature rising rate reaching 70-90 ℃ in the S3 is 1-5 ℃/min, and the temperature rising rate reaching 400-800 ℃ is 1-5 ℃/min; the temperature rising rate reaching 900-1250 ℃ is 1-5 ℃/min.
As a further scheme, the mass fraction of the polymer in the dimethylacetamide solution in the S4 is 0.1-10%.
As a further scheme, the mass ratio of the sodium salt to the polymer to the oxide is (0.01-0.2) 1 (0.001-0.05).
As a further scheme, the stirring condition in the step S4 is 50-90 ℃ for 10-12 h.
As a further scheme, the oxide is added in the S4, and then stirring is needed, wherein the stirring time is 10-12 h.
In a further scheme, in the S5, the mass ratio of the intermediate 2 to the mixed solution 2 is 1:1-5:1 by mass
As a further scheme, the vacuum drying condition is that the vacuum drying is carried out for 8-24 hours at the temperature of 90-110 ℃.
The invention also provides a battery or an electrochemical device with the negative electrode material.
The invention also provides a battery or an electrochemical device with the anode material prepared by the method.
The invention has the characteristics and beneficial effects that:
(1) The invention designs the structure of the anode material, and mainly builds the anode material through a series of structures such as microstructure-interlayer spacing, macrostructure-double-layer structure, pore structure, surface modification-cladding of the anode material and the like, so as to obtain the anode material with high initial efficiency, high charging rate performance and high cycle performance.
(2) The method of the invention is simple and easy to realize, and can be used for industrial production.
(3) The negative electrode material obtained by the invention is used in a sodium battery, and can improve the cycle performance and the safety performance of the battery.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments or the description of the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic view of a negative electrode material of the present invention.
Detailed Description
In order to facilitate understanding of the preparation method of an anode of the present invention, a more complete description of the preparation method of an anode of the present invention will be given below, examples of which are given, but are not intended to limit the scope of the present invention.
In order to facilitate understanding of the preparation method of a negative electrode material according to the present invention, a more complete description of the preparation method of a negative electrode material according to the present invention will be given below, but the scope of the present invention is not limited thereto. It should be understood that these examples are for the purpose of more detailed description only and should not be construed as limiting the invention in any way, i.e., not intended to limit the scope of the invention; relational terms such as "intermediate 1" and "intermediate 2" and the like may be used solely to distinguish one element from another element having the same name, and do not necessarily require or imply any such actual relationship or order between the elements.
In a first aspect, some embodiments of the present invention provide a negative electrode material having a double-layer structure of an outer layer and an inner core;
the inner core is hard carbon; the outer layer is porous hard carbon;
The porous hard carbon is characterized in that the inner surface of the porous structure of the porous hard carbon is coated with a high ion conductivity layer.
In the negative electrode material, the negative electrode material has a double-layer structure, so that uniform sodium ions can be realized, uniform and rapid deintercalation and migration of the sodium ions are promoted, on the other hand, side reactions between the negative electrode material and an electrolyte can be reduced, and the cycle performance and the safety performance of a battery can be improved when the negative electrode material is used in a sodium battery.
The porous hard carbon is mainly used for homogenizing the distribution of sodium ions, so that the sodium ions can be uniformly introduced into the negative electrode material, the accumulation of the sodium ions on the surface of the negative electrode material is reduced, and the formation of sodium dendrites is reduced. And the safety of the battery is improved.
The high ion conductivity layer loaded on the inner surface of the porous structure can isolate side reaction between electrolyte and the anode material and can also improve the transfer speed of sodium ions. In addition, the dissociation speed of the sodium salt can be improved, so that uniform distribution is formed, and the migration of sodium ions in the high-ion-conductivity layer is accelerated.
In some embodiments, the outer layer has at least 1 and at most 3 pore structures in the direction of thickness.
According to the invention, the uniformity and the capacity of the anode material are balanced for the arrangement between the thickness of the inner core and the thickness of the outer layer, and finally, the uniformity of the anode material is improved on the basis of obtaining higher capacity, so that the sodium precipitation reaction is reduced. When the outer porous hard carbon layer is too thin, the uniformity of the thickness of the outer layer structure is difficult to control or a better pore structure is difficult to form, and the final multiplying power performance effect is influenced; and when the outer porous layer is too thin, the control requirement on the process is extremely high, and the industrialization process is relatively difficult. When the outer layer structure is too thick, the density of the material will decrease due to the more porous structure, which will result in a decrease in the compacted density of the material, ultimately resulting in a lower cell capacity and energy density. Typical, non-limiting, for example, the thickness of the inner core and the thickness of the outer layer are 5:1, 6:1, 7:1, 8:1, 9:1, 10:1.
In some embodiments, the porous hard carbon has a pore size distribution of 200nm to 500nm.
In the invention, the pore size distribution is to realize the redistribution of sodium ions on one hand, and on the other hand, the poor uniformity of sodium ion clusters and loaded high ion conductivity layers caused by the too large exposure area of the anode material is prevented. The function of the holes is similar to that of a multi-layer screen, sodium ions can be redistributed in the holes for multiple times, so that sodium ions are relatively uniform when the sodium ions are embedded in all parts of the material, accumulation is not easy to form on the surface of the material due to sodium ion aggregation, particularly, machining defects or local failure in the circulation process exist in a battery cell, and the non-uniform distribution of the sodium ions is easy to be caused. If the pore diameter is smaller than 200nm, the entry of electrolyte is not facilitated, so that the transmission of sodium ions is affected, and the subsequent coating of the high-ion-conductivity material is also not facilitated. If the pore diameter is larger than 500nm, the specific surface area formed by pores is larger due to the larger pore diameter, so that regions with different surface energies are easier to form, sodium ions are easy to gather and reduce at a low surface energy to form sodium clusters, therefore, the pore diameter is not larger than 500nm, the larger the pores are, the larger the exposed specific surface area is, and if the coating is uneven, the condition of first effect reduction is more easy to occur. Typical, non-limiting, e.g., porous hard carbon, has a pore size distribution of 200nm-250nm、200nm-300nm、200nm-350nm、200nm-400nm、200nm-450nm、200nm-500nm、250nm-300nm、250nm-350nm、250nm-400nm、250nm-450nm、250nm-500nm、300nm-350nm、300nm-400nm、300nm-450nm、300nm-500nm、350nm-400nm、350nm-450nm、350nm-500nm、400nm-450nm、400nm-500nm、450nm-500nm.
In some embodiments, the half-width of the pore size distribution is 100nm to 200nm.
Typical non-limiting examples are the half-widths of the pore size distribution of 100nm,110nm,120nm,130nm,140nm,150nm,160nm,170nm,180nm,190nm,200nm.
In some embodiments, the anode material has a microcrystalline interlayer spacing of 0.37nm to 0.41nm, preferably 0.38 to 0.4nm.
In the invention, the proper microcrystalline interlayer spacing is favorable for the diffusion of the sodium ion material in the material, and the volume change of the material brought in the cyclic charge and discharge process can be reduced, so that the charge rate performance and the cyclic stability of the material can be further improved.
In some embodiments, the particle size D50 of the negative electrode material is 3 μm to 9 μm.
In some embodiments, the raw materials of the high ionic conductivity layer include sodium salts, polymers, oxides.
The high ionic conductivity layer can reduce the specific surface area of the anode material, has higher ionic conductivity and ensures the rate capability. The addition of the sodium salt can improve the ion conductivity of the high ion conductivity layer, and the polymer can disperse the sodium salt on one hand, thereby being beneficial to the uniform dissociation of the sodium salt, and on the other hand, can attract sodium ions in the electrolyte, and promote the rapid migration of the sodium ions; the oxide can increase sodium ion channels and further help the accelerated transmission of sodium ions.
In some embodiments, the sodium salt comprises one or more of sodium hexafluorophosphate, sodium bis-fluorosulfonimide.
In some embodiments, the polymer comprises one or more of polyethylene oxide, polymethyl methacrylate, polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polyethylene glycol.
In some embodiments, the oxide comprises one or more of magnesium oxide, silicon dioxide, aluminum oxide.
In some embodiments, the mass ratio of sodium salt, polymer, and oxide is (0.01-0.2) 1 (0.001-0.05).
In a second aspect, some embodiments of the present invention provide a method for preparing a negative electrode material, the method comprising:
S1: presintering the hard carbon precursor to form an intermediate 1;
s2: adding resorcinol and formaldehyde into an ethanol solution, adding ammonia water, and finally adding a template agent to form a mixed solution 1;
s3: placing the intermediate 1 into the mixed solution 1, stirring, then carrying out heat preservation at 70-90 ℃ for 1-2h, then carrying out heat preservation at 400-800 ℃ for 1-3 h, and finally carrying out heat preservation at 900-1250 ℃ for 1-3 h; acid washing and alkali washing to obtain an intermediate 2;
s4: dissolving a polymer in a dimethylacetamide solution, stirring, and then adding sodium salt and oxide to obtain a mixed solution 2;
s5: and mixing the intermediate 2 with the mixed solution 2, and vacuum drying to obtain the anode material.
In the method, the design of the aperture in the anode material is realized by adjusting the size of the template agent particles, and the design of the stage temperature in S3 is beneficial to the microcrystalline interlayer spacing of the anode material in the invention to be within the scope of the invention, so that the migration speed of sodium ions is beneficial to be improved.
In some embodiments, the hard carbon precursor comprises one or more of biomass, pitch, resin, coal-based.
In some embodiments, the sodium salt comprises one or more of sodium hexafluorophosphate, sodium bis (trifluoromethylsulfonyl) imide.
In some embodiments, the polymer comprises one or more of polyethylene oxide, polymethyl methacrylate, polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polyethylene glycol.
In some embodiments, the oxide comprises one or more of magnesium oxide, silicon dioxide, aluminum oxide.
In some embodiments, the templating agent comprises one or more of zeolite, silica, alumina.
In some embodiments, the aqueous ammonia is 25% aqueous ammonia. 25% of the 25% aqueous ammonia represents the concentration of aqueous ammonia.
In some embodiments, the acid comprises one or more of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid.
In some embodiments, the base comprises one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonia, trisodium phosphate.
In some embodiments, the presintering conditions in S1 are at a temperature of 300℃to 600℃and a heat preservation time of 1h to 3h.
In step S1 of the invention, a sintered hard carbon material is obtained, which forms a porous structural mat foundation for the subsequent. Typical, non-limiting, conditions for pre-sintering are, for example, a temperature of 300 ℃, 350 ℃, 400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃, a heat soak of 1h, 1.5h, 2h, 2.5h, 3h.
In some embodiments, the temperature up to the pre-sintering temperature is at a rate of 1 ℃/min to 5 ℃/min.
Typical, non-limiting, for example, heating rates are 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min.
In some embodiments, the mass fraction of ethanol in the ethanol solution in S2 is 60% -90%.
In some embodiments, the mass ratio of resorcinol, formaldehyde, ammonia water and template agent in S2 is 1 (1.02-1.2) (0.9-1.2) (0.01-0.2).
In some embodiments, stirring is required after adding the template agent in S2, and the stirring time is 15-20 h.
In the invention, the template agent is added and then stirred, and the stirring is used for full reaction. Typical, non-limiting, for example, stirring times are 15h, 16h, 17h, 18h, 19h, 20h.
In some embodiments, the mass ratio of intermediate 1 in mixed solution 1 to resorcinol in mixed solution 1 in S3 is (0.05-0.2): 1.
In some embodiments, the stirring time in S3 is 2h-5h.
Typical, non-limiting, for example, the stirring time in S3 is 2h, 3h, 4h, 5h.
In some embodiments, the heating rate up to 70-90 ℃ in S3 is 1-5 ℃/min, and the heating rate up to 300-600 ℃ is 1-5 ℃/min; the temperature rising rate reaching 1000-1250 ℃ is 1-5 ℃/min.
Typical, non-limiting, for example, the heating rate to 70℃to 90℃in S3 is 1℃per minute, 2℃per minute, 3℃per minute, 4℃per minute, 5℃per minute. The heating rate up to 300-600 ℃ is 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min and 5 ℃/min. The heating rate up to 900-1250 ℃ is 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min and 5 ℃/min.
In some embodiments, the mass fraction of polymer in the dimethylacetamide solution in S4 is 0.1% to 10%.
Typical, non-limiting, for example, the mass fraction of polymer in the dimethylacetamide solution in S4 is 0.1%, 1%, 3%, 5%, 7%, 10%.
In some embodiments, the mass ratio of the sodium salt, the polymer and the oxide is (0.01-0.2) 1 (0.001-0.05).
In some embodiments, the stirring in S4 is performed at a temperature of 50℃to 90℃for 10 hours to 12 hours.
Typical, non-limiting, conditions of stirring in S4 are, for example, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃. The stirring time is 10h, 11h and 12h.
In some embodiments, stirring is also required after adding the oxide to S4 for a period of time ranging from 10 hours to 12 hours.
Typical, non-limiting, for example, stirring times are 10 hours, 11 hours, 12 hours.
In some embodiments, in S5, the mass ratio of the intermediate 2to the mixed solution 2 is 1:1-.
Typical, non-limiting, for example, the mass ratio of intermediate 2to mixed solution is 1:1, 2:1, 3:1, 4:1, 5:1.
In some embodiments, the vacuum drying is performed at a temperature of 90 ℃ to 110 ℃ for 8 hours to 24 hours.
Typical, non-limiting, for example, vacuum drying temperatures are 90 ℃, 100 ℃, 110 ℃, and vacuum drying times are 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h.
In a third aspect, some embodiments of the present invention provide a battery or electrochemical device having a negative electrode material.
Further description will be provided below in connection with specific examples.
Example 1:
S1: pre-sintering coconut shells serving as precursors, heating to 600 ℃ at a heating condition of 2 ℃/min, and preserving heat for 2 hours to form an intermediate 1. Intermediate 1 was crushed to a D50 of between 3 μm.
S2: resorcinol 10g and formaldehyde 10.5g were added to a mixed solution of water and ethanol 280g, stirred for 30 minutes, then added with 25% ammonia water 10ml, stirred for 10 minutes, and then added with 0.5g of a template agent Al 2O3,Al2O3 to an average particle size of 100nm (half-width 50 nm) to give a mixed solution 1.
S3: 100g of the crushed intermediate 1 is added into the mixed solution 1, stirring is continued for 3 hours, the mixed solution is heated to 80 ℃ at the speed of 2 ℃/min, after heat preservation for 1 hour, the temperature is continuously heated to 700 ℃ at the speed of 2 ℃/min, heat preservation is carried out for 2 hours, and then the temperature is continuously heated to 1100 ℃ at the speed of 5 ℃/min, and heat preservation is carried out for 2 hours, so that the intermediate 2 is formed. Intermediate 2 is acid washed and alkali washed to obtain intermediate 3.
S4: 50g of polyethylene oxide is dissolved in a dimethylacetamide solution to form a solution with the mass fraction of 0.5%, 2g of sodium difluorosulfimide (NaFSI) is added after stirring for 12 hours at 80 ℃, 0.05g of nano-scale oxide magnesium oxide is added after continuous stirring, and stirring is continued for 12 hours to form a mixed solution 2. Mixing and stirring the intermediate 3 and the mixed solution 2 in a proportion of 50g uniformly, and vacuum drying at 100 ℃ for 24 hours to obtain the final hard carbon product.
Example 2: in example 2S 3: 100g of the crushed intermediate 1 is added into the mixed solution 1, stirring is continued for 3 hours, the mixed solution is heated to 80 ℃ at the speed of 2 ℃/min, after heat preservation for 1 hour, the temperature is continuously heated to 700 ℃ at the speed of 2 ℃/min, heat preservation is carried out for 2 hours, and then the temperature is continuously heated to 900 ℃ at the speed of 5 ℃/min, and heat preservation is carried out for 2 hours, so that the intermediate 2 is formed. Intermediate 2 is acid washed and alkali washed to obtain intermediate 3. Other preparation parameters were the same as in example 1.
Example 3: in example 3S 3: 100g of the crushed intermediate 1 is added into the mixed solution 1, stirring is continued for 3 hours, the mixed solution is heated to 80 ℃ at the speed of 2 ℃/min, after heat preservation for 1 hour, the temperature is continuously heated to 700 ℃ at the speed of 2 ℃/min, heat preservation is carried out for 2 hours, and then the temperature is continuously heated to 1250 ℃ at the speed of 5 ℃/min, and heat preservation is carried out for 2 hours, so that the intermediate 2 is formed. Intermediate 2 is acid washed and alkali washed to obtain intermediate 3. Other preparation parameters were the same as in example 1.
Example 4: in example 4, 50g of the crushed intermediate 1 was added to the mixed solution 1 and stirring was continued for 3 hours, the mixed solution was heated to 80℃at a speed of 2℃per minute, and after heat preservation for 1 hour, the temperature was continuously raised to 700℃at a speed of 2℃per minute for 2 hours, and then the temperature was continuously raised to 1100℃at a speed of 5℃per minute for 2 hours, to form intermediate 2. Intermediate 2 is acid washed and alkali washed to obtain intermediate 3.
Example 5: in example 5, 150g of the crushed intermediate 1 was added to the mixed solution 1 and stirring was continued for 3 hours, the mixed solution was heated to 80℃at a speed of 2℃per minute, and after heat preservation for 1 hour, the temperature was continuously raised to 700℃at a speed of 2℃per minute for 2 hours, and then the temperature was continuously raised to 1100℃at a speed of 5℃per minute for 2 hours, to form intermediate 2. Intermediate 2 is acid washed and alkali washed to obtain intermediate 3.
Example 6: in example 6, 200g of the crushed intermediate 1 was added to the mixed solution 1 and stirring was continued for 3 hours, the mixed solution was heated to 80℃at a rate of 2℃per minute, and after heat preservation for 1 hour, the temperature was continuously raised to 700℃at a rate of 2℃per minute for 2 hours, and then the temperature was continuously raised to 1100℃at a rate of 5℃per minute for 2 hours, to form intermediate 2. Intermediate 2 is acid washed and alkali washed to obtain intermediate 3.
Example 7: in example 7, the average particle diameter of the template Al 2O3,Al2O3 was 200nm (half-width of the particle size distribution 50 nm). Other parameters were the same as in example 1.
Example 8: in example 7, the average particle diameter of the template Al 2O3,Al2O3 was 300nm (half-width of the particle size distribution 50 nm). Other parameters were the same as in example 1.
Example 9: in example 10, S4: 50g of polyethylene oxide is dissolved into a dimethylacetamide solution to form a solution with the mass fraction of 0.5%, 1g of sodium difluorosulfimide is added after stirring for 12 hours at 80 ℃, 0.05g of nano-scale oxide magnesium oxide is added after continuous stirring, and stirring is continued for 12 hours to form a mixed solution 2. And (3) uniformly mixing and stirring 350g of the intermediate and 250g of the mixed solution, and vacuum drying at 100 ℃ for 24 hours to obtain a final hard carbon product. Other parameters were the same as in example 1.
Example 10: in example 11, S4: 50g of polyethylene oxide is dissolved into a dimethylacetamide solution to form a solution with the mass fraction of 0.5%, 10g of sodium difluorosulfimide is added after stirring for 12 hours at 80 ℃, 0.05g of nano-scale oxide magnesium oxide is added after continuous stirring, and stirring is continued for 12 hours to form a mixed solution 2. And (3) uniformly mixing and stirring 350g of the intermediate and 250g of the mixed solution, and vacuum drying at 100 ℃ for 24 hours to obtain a final hard carbon product. Other parameters were the same as in example 1.
Comparative example 1: s3 in comparative example 1: 100g of the crushed intermediate 1 is added into the mixed solution 1, stirring is continued for 3 hours, the mixed solution is heated to 80 ℃ at the speed of 2 ℃/min, after heat preservation for 1 hour, the temperature is continuously heated to 700 ℃ at the speed of 2 ℃/min, heat preservation is carried out for 2 hours, and then the temperature is continuously heated to 800 ℃ at the speed of 5 ℃/min, and heat preservation is carried out for 2 hours, so that the intermediate 2 is formed. Intermediate 2 is acid washed and alkali washed to obtain intermediate 3. Other preparation parameters were the same as in example 1.
Comparative example 2: s3 in comparative example 2: 100g of the crushed intermediate 1 is added into the mixed solution 1, stirring is continued for 3 hours, the mixed solution is heated to 80 ℃ at the speed of 2 ℃/min, after heat preservation for 1 hour, the temperature is continuously heated to 700 ℃ at the speed of 2 ℃/min, heat preservation is carried out for 2 hours, and then the temperature is continuously heated to 1350 ℃ at the speed of 5 ℃/min, and heat preservation is carried out for 2 hours, so that the intermediate 2 is formed. Intermediate 2 is acid washed and alkali washed to obtain intermediate 3. Other preparation parameters were the same as in example 1.
Comparative example 3: in comparative example 3, 250g of the crushed intermediate 1 was added to the mixed solution 1 and stirring was continued for 3 hours, the mixed solution was heated to 80℃at a speed of 2℃per minute, and after heat preservation for 1 hour, the temperature was continuously raised to 700℃at a speed of 2℃per minute for 2 hours, and then the temperature was continuously raised to 1100℃at a speed of 5℃per minute for 2 hours, to form intermediate 2. Intermediate 2 is acid washed and alkali washed to obtain intermediate 3.
Comparative example 4: in comparative example 4, 300g of the crushed intermediate 1 was added to the mixed solution 1 and stirring was continued for 3 hours, the mixed solution was heated to 80℃at a rate of 2℃per minute, and after heat preservation for 1 hour, the temperature was continuously raised to 700℃at a rate of 2℃per minute for 2 hours, and then the temperature was continuously raised to 1100℃at a rate of 5℃per minute for 2 hours, to form intermediate 2. Intermediate 2 is acid washed and alkali washed to obtain intermediate 3.
Comparative example 5: in comparative example 5, the average particle diameter of the template Al 2O3,Al2O3 was 400nm (half-width of the particle size distribution 50 nm). Other parameters were the same as in example 1.
Comparative example 6: in comparative example 6, the average particle diameter of the template Al 2O3,Al2O3 was 50nm (half-width of the particle size distribution 50 nm). Other parameters were the same as in example 1.
Comparative example 7: in comparative example 7, the average particle diameter of the template Al 2O3,Al2O3 was 100nm (the half-width of the particle diameter distribution was 200 nm). Other parameters were the same as in example 1.
Comparative example 8: in comparative example 8, the average particle diameter of the template Al 2O3,Al2O3 was 100nm (the half-width of the particle diameter distribution was 300 nm). Other parameters were the same as in example 1.
Comparative example 9: in example 9, S4: 50g of polyethylene oxide is dissolved in a dimethylacetamide solution to form a solution with the mass fraction of 0.5%, 2g of sodium difluorosulfimide is added after stirring for 12 hours at 80 ℃, 0.025g of nano-scale oxide magnesium oxide is added after continuous stirring, and stirring is continued for 12 hours to form a mixed solution 2. And (3) uniformly mixing and stirring 350g of the intermediate and 250g of the mixed solution, and vacuum drying at 100 ℃ for 24 hours to obtain a final hard carbon product. Other parameters were the same as in example 1.
Comparative example 10: in comparative example 9, S4: 50g of polyethylene oxide is dissolved into a dimethylacetamide solution to form a solution with the mass fraction of 0.5%, 2g of sodium difluorosulfimide is added after stirring for 12 hours at 80 ℃, 3g of nano-scale oxide magnesium oxide is added after continuous stirring, and the stirring is continued for 12 hours to form a mixed solution 2. And (3) uniformly mixing and stirring 350g of the intermediate and 250g of the mixed solution, and vacuum drying at 100 ℃ for 24 hours to obtain a final hard carbon product. Other parameters were the same as in example 1.
Comparative example 11: in comparative example 10, S4: 50g of polyethylene oxide is dissolved into a dimethylacetamide solution to form a solution with the mass fraction of 0.5%, 15g of sodium difluorosulfimide is added after stirring for 12 hours at 80 ℃, 0.05g of nano-scale oxide magnesium oxide is added after continuous stirring, and stirring is continued for 12 hours to form a mixed solution 2. And (3) uniformly mixing and stirring 350g of the intermediate and 250g of the mixed solution, and vacuum drying at 100 ℃ for 24 hours to obtain a final hard carbon product. Other parameters were the same as in example 1.
Comparative example 12: in comparative example 12, S4: 50g of polyethylene is dissolved into a dimethylacetamide solution to form a solution with the mass fraction of 0.5%, 2g of sodium difluorosulfimide is added after stirring for 12 hours at 80 ℃, 0.05g of nano-scale oxide magnesium oxide is added after continuous stirring, and the stirring is continued for 12 hours to form a mixed solution 2. And (3) uniformly mixing and stirring 350g of the intermediate and 250g of the mixed solution, and vacuum drying at 100 ℃ for 24 hours to obtain a final hard carbon product. Other parameters were the same as in example 1.
The negative electrode material obtained was also used in a battery and tested:
and (3) assembling a button cell: the anode material obtained above was stirred with a conductive agent, a dispersant CMC, and a binder SBR in a ratio of 92% to 2% to 3%, and the obtained slurry was coated on an aluminum foil and vacuum-dried. And cutting the dried pole piece into pole pieces with specific size, and assembling the pole pieces into the battery according to the sequence of the negative pole shell, the elastic piece, the sodium piece, the electrolyte, the diaphragm, the electrolyte, the negative pole piece and the positive pole shell.
And (3) calculating the microcrystalline interlayer spacing:
2dsinθ＝nλ
d, crystal face distance;
θ: read out on the graph;
lambda: x-ray wavelength n=1 (first order diffraction) Cu target Ka-ray (λ= 0.15406 nm)
The method for testing the first effect and the reversible capacity of the power-off comprises the following steps:
1、Rest 4h；
2. constant current discharge of 0.1C to 0V, constant current discharge of 0.02C to 0V, recording capacity C1;
3. Constant current charging to 1.5V at 0.1C, recording capacity C2, first effect = C2/C1, C2 noted as reversible capacity of the material.
Calculation of the retention rate of the power-off cycle:
1、Rest 4h；
2. constant current discharge of 0.1C to 0V, constant current discharge of 0.02C to 0V, recording capacity C1;
3. constant current charging to 1.5V at 0.1C, recording capacity C3;
4. Constant current discharge of 0.1C to 0V, constant current charge of 0.1C to 1.5V and 50 cycles, record 50 cycles of charge capacity C4. Circulation capacity retention = C4/C3.
Analysis of results:
TABLE 1 influence of hard carbon crystallite interlayer spacing on performance
As can be seen from table 1, as the temperature increases, the material microcrystalline layer spacing gradually decreases, and the reversible capacity tends to increase and then decrease in accordance with the practice. Mainly because the material does not form a good carbon lamellar structure, and the structure can store a certain amount of sodium, the material capacity is lower when the temperature is not high; at higher levels, the carbon platelet spacing is smaller, which is detrimental to sodium intercalation and can also result in reduced capacity. The battery 3C has a better constant current charging ratio (the higher the constant current ratio is, the better the rate performance is), mainly because the charging ratio is limited by electron conductivity and ion conductivity, when the temperature is lower, for example, 800 ℃ (comparative example 1), the material does not form a good carbon lamellar structure, and the electron conductivity is lower, so the rate performance is relatively poor; and at higher temperatures, such as 1350 c (comparative example 2), the rate capability is hindered because the carbon platelet spacing is smaller with increasing temperature, which is detrimental to sodium intercalation.
TABLE 2 influence of the inner and outer layer thickness ratios on the Performance
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As can be seen from Table 2, by controlling the ratio of the thickness of the inner and outer layers by the amount of the intermediate 1, it can be seen that the first effect and the capacity of the material are both in a reduced state as the ratio of the outer layer is increased, mainly because the pores of the outer layer are large, on the one hand, the density is reduced, resulting in a reduced capacity, and on the other hand, the specific surface area is increased, resulting in an increase in the side reaction in the sodium intercalation process, thus leading to a reduced first effect of the material. But on the other hand, the proportion of the pore structure of the outer layer is increased, so that the contact surface of the material and the electrolyte is increased, the multiplying power performance of the material is improved, and therefore, the proportion of the inner layer to the outer layer of the obtained material is controlled within the range of 5:1-10:1 in two aspects. TABLE 3 influence of outer pore size and distribution on Properties
As can be seen from Table 3, as the particle size of the template agent increases, the pore diameter increases, and in the range of 100-300nm of the template agent, the uniform pore structure has a good dispersion effect, so that sodium is not easy to separate out from the anode material, the capacity retention rate is high after 50cl of circulation, but the pore diameter continues to increase, so that the pore distribution effect is weakened, the half-peak width distribution of the pore diameter is too large, and the same reason is adopted, and sodium deposition is gradually started in the circulation process, so that the circulation capacity is reduced. When the pore diameter is too small, the surface coating layer cannot smoothly enter the pores, so that part of the pores are not coated, side reactions with electrolyte are serious, the impedance is increased, sodium is also separated after the circulation, and the material capacity is reduced.
TABLE 4 influence of polymer layers on cell performance
As can be seen in Table 4, when NaFSI is added in a small amount, the sodium ion concentration of the polymer layer is insufficient to support rapid migration of sodium ions, and when the concentration is too high, the anion concentration is too high and moves in the polymer layer to block migration of sodium ions due to the presence of anions in the sodium salt. The addition of magnesium oxide can reduce the degree of polymerization of the polymer chain and can reduce its local glass transition temperature, thus facilitating the segmental motion of the polymer chain and sodium ion migration, while after increasing the amount, the added material hinders the sodium ion transfer. The polymer adopts polyethylene oxide material with the coordination ability with sodium ions in NaFSI, on one hand, sodium ions can be dissociated uniformly, so that the sodium ions are distributed uniformly in the polymer layer, on the other hand, sodium ions in the electrolyte can be attracted to pass through the polymer layer quickly, and materials such as polyethylene which do not have the coordination ability with sodium ions can cause the sodium ions to be distributed unevenly in the polymer layer, and on the contrary, a certain resistance exists for the sodium ions to enter the material due to no attraction effect on the sodium ions. Therefore, it is further preferred that the sodium salt is sodium difluorosulfimide, the polymer is polyethylene oxide, and the oxide is magnesium oxide.
It should be noted that the above-mentioned embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. The negative electrode material is characterized by having a double-layer structure of an outer layer and an inner core, wherein the inner core is hard carbon, the outer layer is porous hard carbon, and the inner surface of the porous structure of the porous hard carbon is coated with a high ion conductivity layer;
The raw materials of the high ion conductivity layer comprise sodium salt, polymer and oxide;
The sodium salt is sodium bis-fluorosulfonyl imide, the polymer is polyethylene oxide, and the oxide is magnesium oxide; the mass ratio of the sodium bis (fluorosulfonyl imide), the polyethylene oxide and the magnesium oxide is (0.01-0.2) 1 (0.001-0.05).
2. The anode material according to claim 1, wherein the outer layer has at least 1 and at most 3 pore structures in a thickness direction;
the pore size distribution of the porous hard carbon is 200nm-500nm;
The microcrystalline interlayer spacing of the anode material is 0.37nm-0.41nm;
The particle diameter D50 of the inner core is 3-9 mu m.
3. The method for producing a negative electrode material according to any one of claims 1 to 2, comprising:
S1: presintering the hard carbon precursor to form an intermediate 1;
s2: adding resorcinol and formaldehyde into an ethanol solution, adding ammonia water, and finally adding a template agent to form a mixed solution 1;
s3: placing the intermediate 1 into the mixed solution 1, stirring, then carrying out heat preservation at 70-90 ℃ for 1-2h, then carrying out heat preservation at 400-800 ℃ for 1-3 h, and finally carrying out heat preservation at 900-1250 ℃ for 1-3 h; acid washing and alkali washing to obtain an intermediate 2;
s4: dissolving a polymer in a dimethylacetamide solution, stirring, and then adding sodium salt and oxide to obtain a mixed solution 2;
s5: and mixing the intermediate 2 with the mixed solution 2, and vacuum drying to obtain the anode material.
4. The method of claim 3, wherein the hard carbon precursor comprises one or more of biomass, pitch, resin, coal-based;
the template agent comprises one or more of zeolite, silicon dioxide and aluminum oxide;
The particle size distribution of the particles of the template agent is 100nm-400nm;
the mass ratio of the sodium salt, the polymer and the oxide is (0.01-0.2) 1 (0.001-0.05).
5. The method according to claim 3, wherein the presintering conditions in S1 are a temperature of 300 ℃ to 600 ℃ and a heat preservation time of 1h to 3h;
The temperature rising rate reaching the temperature of the presintering is 1 ℃/min-5 ℃/min;
the mass ratio of the resorcinol, formaldehyde, ammonia water and the template agent in the S2 is 1 (1.02-1.2) (0.9-1.2) (0.01-0.2);
stirring is needed after the template agent is added in the S2, and the stirring time is 15-20 hours;
the mass ratio of the intermediate 1 in the mixed solution 1 in the step S3 to the resorcinol in the mixed solution 1 is (0.05-0.2): 1;
the stirring time in the step S3 is 2-5 h;
The temperature rising rate reaching 70-90 ℃ in the step S3 is 1-5 ℃/min, and the temperature rising rate reaching 400-800 ℃ is 1-5 ℃/min; the heating rate reaching 900-1250 ℃ is 1-5 ℃/min;
The mass fraction of the polymer in the dimethylacetamide solution in the S4 is 0.1-10%;
Stirring in the step S4 is carried out for 10-12 hours at 50-90 ℃;
After the oxide is added in the S4, stirring is needed, and the stirring time is 10-12 hours;
in the step S5, the mass ratio of the intermediate 2 to the mixed solution 2 is 1:1-5:1;
The vacuum drying condition is that the vacuum drying is carried out for 8-24 hours at the temperature of 90-110 ℃.
6. A battery or an electrochemical device having the anode material according to any one of claims 1 to 2, or having the anode material obtained by the production method according to any one of claims 3 to 5.
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