CN114551886A - Composite negative electrode material, preparation method thereof and lithium ion battery - Google Patents
Composite negative electrode material, preparation method thereof and lithium ion battery Download PDFInfo
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- CN114551886A CN114551886A CN202210166676.2A CN202210166676A CN114551886A CN 114551886 A CN114551886 A CN 114551886A CN 202210166676 A CN202210166676 A CN 202210166676A CN 114551886 A CN114551886 A CN 114551886A
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- 239000002131 composite material Substances 0.000 title claims abstract description 70
- 238000002360 preparation method Methods 0.000 title claims abstract description 49
- 239000007773 negative electrode material Substances 0.000 title claims abstract description 30
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 20
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 20
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 153
- 239000005543 nano-size silicon particle Substances 0.000 claims abstract description 60
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 54
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 53
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 45
- 238000002156 mixing Methods 0.000 claims abstract description 45
- 238000000034 method Methods 0.000 claims abstract description 40
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 39
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 37
- 238000006722 reduction reaction Methods 0.000 claims abstract description 36
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims abstract description 34
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 34
- 239000010703 silicon Substances 0.000 claims abstract description 34
- 239000002243 precursor Substances 0.000 claims abstract description 28
- 238000010438 heat treatment Methods 0.000 claims abstract description 25
- 239000011777 magnesium Substances 0.000 claims abstract description 21
- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 21
- 230000009467 reduction Effects 0.000 claims abstract description 17
- 230000008569 process Effects 0.000 claims abstract description 15
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 8
- 238000005406 washing Methods 0.000 claims description 35
- 239000010405 anode material Substances 0.000 claims description 31
- 238000006243 chemical reaction Methods 0.000 claims description 31
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- 238000003756 stirring Methods 0.000 claims description 27
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 26
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 24
- 239000002253 acid Substances 0.000 claims description 24
- GHMLBKRAJCXXBS-UHFFFAOYSA-N resorcinol Chemical compound OC1=CC=CC(O)=C1 GHMLBKRAJCXXBS-UHFFFAOYSA-N 0.000 claims description 24
- 239000003054 catalyst Substances 0.000 claims description 22
- 230000007062 hydrolysis Effects 0.000 claims description 22
- 238000006460 hydrolysis reaction Methods 0.000 claims description 22
- UFWIBTONFRDIAS-UHFFFAOYSA-N Naphthalene Chemical compound C1=CC=CC2=CC=CC=C21 UFWIBTONFRDIAS-UHFFFAOYSA-N 0.000 claims description 20
- LZZYPRNAOMGNLH-UHFFFAOYSA-M Cetrimonium bromide Chemical compound [Br-].CCCCCCCCCCCCCCCC[N+](C)(C)C LZZYPRNAOMGNLH-UHFFFAOYSA-M 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 18
- 239000002245 particle Substances 0.000 claims description 17
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 16
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 16
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 14
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- JFCCVNTYPIUJDJ-UHFFFAOYSA-N methyl-tris(prop-2-enyl)silane Chemical compound C=CC[Si](C)(CC=C)CC=C JFCCVNTYPIUJDJ-UHFFFAOYSA-N 0.000 claims description 10
- QQQSFSZALRVCSZ-UHFFFAOYSA-N triethoxysilane Chemical compound CCO[SiH](OCC)OCC QQQSFSZALRVCSZ-UHFFFAOYSA-N 0.000 claims description 10
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 9
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 9
- 229910017604 nitric acid Inorganic materials 0.000 claims description 9
- -1 aldehyde compound Chemical class 0.000 claims description 8
- 239000001307 helium Substances 0.000 claims description 7
- 229910052734 helium Inorganic materials 0.000 claims description 7
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 7
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 7
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 7
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 7
- RYYKJJJTJZKILX-UHFFFAOYSA-M sodium octadecanoate Chemical compound [Na+].CCCCCCCCCCCCCCCCCC([O-])=O RYYKJJJTJZKILX-UHFFFAOYSA-M 0.000 claims description 7
- 239000004094 surface-active agent Substances 0.000 claims description 7
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 6
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- 238000011946 reduction process Methods 0.000 claims description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 4
- GVGUFUZHNYFZLC-UHFFFAOYSA-N dodecyl benzenesulfonate;sodium Chemical compound [Na].CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 GVGUFUZHNYFZLC-UHFFFAOYSA-N 0.000 claims description 3
- 229940080264 sodium dodecylbenzenesulfonate Drugs 0.000 claims description 3
- 238000000227 grinding Methods 0.000 claims description 2
- 239000000243 solution Substances 0.000 claims 21
- 238000004519 manufacturing process Methods 0.000 claims 5
- 238000004140 cleaning Methods 0.000 claims 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 claims 1
- 239000011259 mixed solution Substances 0.000 claims 1
- 239000010406 cathode material Substances 0.000 abstract description 24
- 239000000463 material Substances 0.000 abstract description 10
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 8
- 229910052744 lithium Inorganic materials 0.000 abstract description 8
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 abstract description 7
- 230000000694 effects Effects 0.000 abstract description 7
- 230000002829 reductive effect Effects 0.000 abstract description 7
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 abstract description 7
- 229910010271 silicon carbide Inorganic materials 0.000 abstract description 7
- 239000007772 electrode material Substances 0.000 abstract description 4
- 238000005265 energy consumption Methods 0.000 abstract description 4
- 238000011031 large-scale manufacturing process Methods 0.000 abstract description 4
- 235000011114 ammonium hydroxide Nutrition 0.000 description 22
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical group [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 14
- 239000008367 deionised water Substances 0.000 description 12
- 229910021641 deionized water Inorganic materials 0.000 description 12
- 239000007788 liquid Substances 0.000 description 10
- 229910002804 graphite Inorganic materials 0.000 description 9
- 239000010439 graphite Substances 0.000 description 9
- 230000002441 reversible effect Effects 0.000 description 9
- 230000009286 beneficial effect Effects 0.000 description 8
- 239000002153 silicon-carbon composite material Substances 0.000 description 8
- 239000011780 sodium chloride Substances 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 5
- 239000003575 carbonaceous material Substances 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 5
- 238000000576 coating method Methods 0.000 description 5
- 150000002431 hydrogen Chemical class 0.000 description 5
- 230000000670 limiting effect Effects 0.000 description 5
- 239000002210 silicon-based material Substances 0.000 description 5
- 238000009831 deintercalation Methods 0.000 description 4
- 239000006185 dispersion Substances 0.000 description 4
- HFQQZARZPUDIFP-UHFFFAOYSA-M sodium;2-dodecylbenzenesulfonate Chemical compound [Na+].CCCCCCCCCCCCC1=CC=CC=C1S([O-])(=O)=O HFQQZARZPUDIFP-UHFFFAOYSA-M 0.000 description 4
- 229960000892 attapulgite Drugs 0.000 description 3
- 229910021419 crystalline silicon Inorganic materials 0.000 description 3
- 238000005530 etching Methods 0.000 description 3
- 229910052625 palygorskite Inorganic materials 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 239000011863 silicon-based powder Substances 0.000 description 3
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 2
- IKHGUXGNUITLKF-XPULMUKRSA-N acetaldehyde Chemical compound [14CH]([14CH3])=O IKHGUXGNUITLKF-XPULMUKRSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 239000001110 calcium chloride Substances 0.000 description 2
- 229910001628 calcium chloride Inorganic materials 0.000 description 2
- 238000003763 carbonization Methods 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000009830 intercalation Methods 0.000 description 2
- 230000002687 intercalation Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000002086 nanomaterial Substances 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 2
- FHVDTGUDJYJELY-UHFFFAOYSA-N 6-{[2-carboxy-4,5-dihydroxy-6-(phosphanyloxy)oxan-3-yl]oxy}-4,5-dihydroxy-3-phosphanyloxane-2-carboxylic acid Chemical compound O1C(C(O)=O)C(P)C(O)C(O)C1OC1C(C(O)=O)OC(OP)C(O)C1O FHVDTGUDJYJELY-UHFFFAOYSA-N 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- 229920002153 Hydroxypropyl cellulose Polymers 0.000 description 1
- 229910014913 LixSi Inorganic materials 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 229940072056 alginate Drugs 0.000 description 1
- 235000010443 alginic acid Nutrition 0.000 description 1
- 229920000615 alginic acid Polymers 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- 238000010000 carbonizing Methods 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 238000004299 exfoliation Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000001863 hydroxypropyl cellulose Substances 0.000 description 1
- 235000010977 hydroxypropyl cellulose Nutrition 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 238000006138 lithiation reaction Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000004005 microsphere Substances 0.000 description 1
- 238000002715 modification method Methods 0.000 description 1
- 238000007709 nanocrystallization Methods 0.000 description 1
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- 230000001681 protective effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000011856 silicon-based particle Substances 0.000 description 1
- 239000011868 silicon-carbon composite negative electrode material Substances 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 238000001694 spray drying Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
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- 238000003828 vacuum filtration Methods 0.000 description 1
- 239000011800 void material Substances 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
-
- 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
- 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
-
- 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 composite negative electrode material, a preparation method thereof and a lithium ion battery, wherein the preparation method comprises the following steps: mixing a carbon source solution, a silicon dioxide solution and a reducing agent to obtain a precursor; and mixing a magnesium source with the obtained precursor, and heating and reducing to obtain the composite negative electrode material. The method simplifies the preparation of the carbon-coated nano silicon cathode material by the two-step magnesiothermic reduction method, prepares the carbon-coated nano silicon cathode material by one-step magnesiothermic reduction reaction, reduces energy consumption and process flow, and is easy for large-scale production; meanwhile, the influence of volume expansion in the process of embedding lithium in silicon is reduced, and the structural stability of the negative electrode material is maintained; the impedance is reduced, the activity of the electrode material is improved, and the cycle performance of the material is improved. According to the composite cathode material provided by the invention, silicon carbide is generated at the silicon-carbon interface, so that the structural stability of the composite cathode material is further kept.
Description
Technical Field
The invention belongs to the technical field of lithium ion battery materials, relates to a preparation method of a composite negative electrode material, and particularly relates to a composite negative electrode material, a preparation method of the composite negative electrode material and a lithium ion battery.
Background
In recent years, the key of new energy automobiles is to improve the energy density and the service life on the premise of the same safety. The current commercial graphite negative electrode has a theoretical specific capacity of only 372mAh/g, which is difficult to satisfy the requirement of high energy density lithium ion battery, and silicon has the highest theoretical specific capacity, which is one of the most promising negative electrode materials, and has received extensive attention from researchers.
The charging and discharging mechanism of the silicon cathode material is different from the charging and discharging mode of the traditional rocking chair battery through embedding and removing reaction, and is closer to the alloying reaction. The final product of lithiation of the silicon negative electrode is LixSi, x is 3-4.4. Because of alloying reaction, the lithiated lithium and silicon elements have the highest theoretical specific capacity compared with the silicon negative electrode when used for the lithium ion battery, and the mass specific energy of the lithium ion battery is greatly and effectively improved. However, the volume of silicon is repeatedly changed in the process of lithium intercalation and deintercalation to generate large internal stress, so that active substances are pulverized to cause the exfoliation of materials. In addition, the volume change of the silicon particles destroys the conductive network of the composite electrode, a solid electrolyte interface film (SEI film) formed on the surface of the material is unstable, more electrolyte is consumed in the circulation process, and the capacity of the battery is rapidly attenuated, so that the commercial application of silicon is limited. Li reduction by silicon nanocrystallization to alleviate the above problems, reduce volume change, and shorten+A transmission path. However, the silicon material with a nano structure is not suitable for being used alone because the silicon material with a nano structure generates more irreversible reactions and lower tap density due to high specific surface area, and needs to be further improved. One of the commonly used silicon negative electrode modification methods is the compounding of silicon carbon materials. The carbon material not only has excellent conductivity and higher electrochemical activity, but also has good compatibility with silicon materials, so that the silicon cathode material is the first choice for modification.
CN 111834610A discloses a preparation method of a lithium ion battery silicon-carbon composite negative electrode material based on magnesium thermal reduction, which comprises the steps of firstly preparing a high-concentration graphite dispersion liquid by using graphite and a carboxymethyl cellulose or hydroxypropyl cellulose solution, then adding nano silica sol into the graphite dispersion liquid to uniformly disperse the nano silica sol, then carrying out spray drying on the dispersion liquid to form a graphite/silica composite, carrying out magnesium thermal reduction reaction, finally adding a styrene-acrylonitrile copolymer emulsion and carrying out high-temperature treatment to obtain the lithium ion battery silicon-carbon composite material. The prepared lithium ion battery silicon-carbon composite material has the advantages of good electrical conductivity, high dispersion degree of graphite and silicon, high battery capacity and long cycle life.
CN 111244414a discloses a method for preparing a silicon-carbon negative electrode material by magnesiothermic reduction, which comprises the following steps: roasting the micro silicon powder, dispersing the micro silicon powder in an acid etching solution, heating in a water bath, and then performing suction filtration, washing and drying to obtain a pretreated sample; mixing a pretreated sample and magnesium powder by ball milling, placing the mixture in a sealed graphite crucible after natural drying, transferring the mixture to a tubular furnace of inert gas for magnesium thermal reaction, and carrying out acid washing, vacuum filtration, water washing and drying on the obtained product to obtain porous crystalline silicon; and uniformly mixing the prepared porous crystalline silicon and the organic matter precursor, drying, and then placing in protective gas for curing to obtain the silicon-based composite material. Porous crystalline silicon is obtained through acid etching pretreatment and magnesium thermal reduction treatment of the micro silicon powder; the silicon material has higher specific capacity, and the formed porous structure plays a role in buffering the volume expansion of the silicon material on one hand; on the other hand, the depth of lithium ion deintercalation and the diffusion distance are shortened, so that the lithium ion deintercalation device shows excellent electrochemical performance.
CN 112436131A discloses a method for preparing a silicon-carbon composite material by using molten salt to assist magnesiothermic reduction, which comprises the steps of firstly carbonizing alginate and attapulgite at high temperature to obtain an amorphous carbon coating coated attapulgite composite material, then adding a reducing agent and molten salt to perform heat-assisted reduction reaction, and performing acid pickling treatment to obtain the silicon-carbon composite material. According to the method for preparing the silicon-carbon composite material by combining high-temperature carbonization and low-temperature molten salt heat assistance, the generation of silicon carbide is effectively reduced through the molten salt heat assistance reduction reaction, the silicon nanoparticles reduced by attapulgite are coated by the carbon coating in the prepared silicon-carbon composite material, and a void structure is formed through acid etching. The composite material is used for a lithium ion battery cathode material, and the carbon layer, the gaps and the porous structure can effectively relieve the volume expansion effect caused in the lithium intercalation and deintercalation process, and simultaneously improve the electronic conductivity, so that the composite material has excellent electrochemical lithium storage performance.
According to the technical scheme, the silicon-carbon composite cathode material is prepared through a magnesiothermic reduction reaction, however, most of the currently adopted magnesiothermic reaction methods are that the reduction reaction of silicon and the carbonization reaction of a carbon source are separately carried out: namely, the reduction of the silicon dioxide material into silicon and the coating of the carbon source are separately carried out, then the high-temperature reaction is carried out, and the carbon source precursor material is carbonized to obtain the silicon-carbon composite material.
In view of the above, how to improve the preparation process, shorten the preparation process, simplify the preparation method, and ensure the excellent electrochemical performance of the composite negative electrode material is a technical problem to be solved in the field of negative electrode materials for lithium ion batteries.
Disclosure of Invention
In order to solve the technical problems, the invention provides a composite negative electrode material, a preparation method thereof and a lithium ion battery, and provides a method for preparing carbon-coated nano silicon by one-step magnesiothermic reduction.
In a first aspect, the present invention provides a method for preparing a composite anode material, the method comprising the steps of:
(1) mixing a carbon source solution, a silicon dioxide solution and a reducing agent to obtain a precursor;
(2) and (3) mixing a magnesium source with the precursor obtained in the step (1), and heating and reducing to obtain the composite negative electrode material.
The invention simplifies the two-step method for preparing the carbon-coated nano silicon cathode material by magnesium thermal reduction, realizes the preparation of the carbon-coated nano silicon cathode material by one-step magnesium thermal reduction reaction, reduces energy consumption and process flow, and is easy for large-scale production. Meanwhile, the preparation method provided by the invention reduces the influence of volume expansion in the process of embedding lithium in silicon, and maintains the structural stability of the cathode material. The outermost layer is coated with the carbon material, so that the conductivity of the negative electrode is improved, the impedance is reduced, the activity of the electrode material is improved, and the cycle performance of the material is improved; according to the composite cathode material provided by the invention, silicon carbide is generated at the silicon-carbon interface, so that the structural stability of the composite cathode material is further kept.
Preferably, the carbon source solution of step (1) comprises a carbon source, a solvent and a hydrolysis catalyst.
Preferably, the carbon source comprises any one or a combination of at least two of resorcinol, polyvinylpyrrolidone, o-diphenol, p-diphenol, or alpha-phenolic naphthalene, typical but non-limiting combinations include combinations of resorcinol and polyvinylpyrrolidone, combinations of polyvinylpyrrolidone and o-diphenol, combinations of o-diphenol and p-diphenol, combinations of p-diphenol and alpha-phenolic naphthalene, combinations of resorcinol, polyvinylpyrrolidone, o-diphenol and p-diphenol, or combinations of o-diphenol, p-diphenol and alpha-phenolic naphthalene, preferably resorcinol.
Preferably, the concentration of the carbon source in the carbon source solution in step (1) is 5-10mg/ml, such as 5mg/ml, 6mg/ml, 7mg/ml, 8mg/ml, 9mg/ml or 10mg/ml, but not limited to the values listed, and other values not listed in the numerical range are also applicable.
Preferably, the solvent comprises methanol and/or ethanol.
Preferably, the hydrolysis catalyst comprises aqueous ammonia.
Preferably, the concentration of the hydrolysis catalyst in the carbon source solution in step (1) is 2-3mg/ml, and may be, for example, 2mg/ml, 2.2mg/ml, 2.4mg/ml, 2.6mg/ml, 2.8mg/ml or 3mg/ml, but is not limited to the values recited, and other values not recited within the range of values are also applicable.
Preferably, the silica solution of step (1) comprises water, a surfactant and silica.
Preferably, the surfactant comprises any one of or a combination of at least two of cetyltrimethyl ammonium bromide, sodium stearate or sodium dodecylbenzene sulphonate, typical but non-limiting combinations include cetyltrimethyl ammonium bromide in combination with sodium stearate, sodium stearate in combination with sodium dodecylbenzene sulphonate, cetyltrimethyl ammonium bromide in combination with sodium dodecylbenzene sulphonate, or cetyltrimethyl ammonium bromide, sodium stearate in combination with sodium dodecylbenzene sulphonate.
Preferably, the surfactant is present at a concentration of 0.03-0.04g/mL, such as 0.03g/mL, 0.031g/mL, 0.032g/mL, 0.034g/mL, 0.036g/mL, 0.038g/mL, or 0.04g/mL, but not limited to the recited values, and any other values within the range are equally applicable.
Preferably, the silica is present in a concentration of 0.01 to 0.015g/mL, for example 0.01g/mL, 0.011g/mL, 0.012g/mL, 0.013g/mL, 0.014g/mL or 0.015g/mL, but not limited to the recited values, and other values not recited in the numerical ranges are equally applicable.
Preferably, the silica comprises nanosilica.
Preferably, the particle size of the nano-silica is in the range of 200-500nm, such as 200nm, 250nm, 300nm, 400nm, 450nm or 500nm, but not limited to the recited values, and other values not recited in the range of values are also applicable.
When the particle size range of the nano silicon dioxide is larger than 500nm, the particle size of the silicon after reduction is too large, the surface is difficult to form uniform coating, and when the particle size range of the nano silicon dioxide is smaller than 200nm, the product after reduction is easy to agglomerate.
Preferably, the preparation method of the nano-silica comprises the following steps: and mixing the organic silicon source solution and the hydrolysis catalyst solution, centrifuging, washing and drying to obtain the nano silicon dioxide.
The preparation process of the nano silicon dioxide provided by the invention is simpleThe shape and the grain size are controllable, and the nano SiO is easy to obtain2The microspheres have dispersed particles and uniform size, and are beneficial to realizing uniform coating with a carbon source.
Preferably, the source of organosilicon comprises any one or a combination of at least two of ethyl orthosilicate, diallylphenyldimethylsilane, triethoxysilane, or methyltriallylsilane, typical but non-limiting combinations include a combination of ethyl orthosilicate and diallylphenyldimethylsilane, a combination of diallylphenyldimethylsilane and triethoxysilane, a combination of triethoxysilane and methyltriallylsilane, a combination of ethyl orthosilicate, diallylphenyldimethylsilane and triethoxysilane, or a combination of diallylphenyldimethylsilane, triethoxysilane, and methyltriallylsilane, preferably ethyl orthosilicate.
Preferably, the solvent of the organic silicon source solution comprises an alcohol.
Preferably, the concentration of the organosilicon source in the organosilicon source solution is from 0.02 to 0.04g/ml, and may be, for example, 0.02g/ml, 0.025g/ml, 0.03g/ml, 0.035g/ml or 0.04g/ml, but is not limited to the recited values, and other values within the range of values are equally applicable.
Preferably, the hydrolysis catalyst comprises aqueous ammonia.
Preferably, the solvent in the hydrolysis catalyst solution comprises a water-alcohol mixture.
Preferably, the volume ratio of water to alcohol in the water-alcohol mixture is 1 (2-3), and may be, for example, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:2.9 or 1:3, but is not limited to the values listed, and other values not listed in the numerical range may be similarly applicable.
Preferably, the hydrolysis catalyst solution has a hydrolysis catalyst concentration of 0.3 to 0.4mg/ml, which may be, for example, 0.3mg/ml, 0.32mg/ml, 0.34mg/ml, 0.36mg/ml, 0.38mg/ml or 0.4mg/ml, but is not limited to the recited values, and other values not recited within the numerical range are equally applicable.
Preferably, the means of mixing comprises stirring.
Preferably, the stirring time is 4-6h, for example 4h, 4.5h, 5h, 5.5h or 6h, but is not limited to the values listed, and other values not listed within the range of values are equally suitable.
Preferably, the stirring speed is 500-700r/min, such as 500r/min, 550r/min, 600r/min, 650r/min or 700r/min, but is not limited to the values listed, and other values not listed in the numerical range are also applicable.
Preferably, the reducing agent in step (1) comprises an aldehyde compound, preferably formaldehyde and/or acetaldehyde.
Preferably, the volume ratio of the carbon source solution, the silica solution and the reducing agent in the step (1) is 1 (9-12) to (4-6), and the volume ratio can be, for example, 1:9:4, 1:10:5, 1:12:6, 1:12:4 or 1:9:6, but is not limited to the enumerated values, and other unrecited values in the numerical range are also applicable.
Preferably, the mixing means of step (1) comprises ultrasonic dispersion and/or stirring.
Preferably, the ultrasonic dispersion time is 20-40min, for example 20min, 25min, 30min, 35min or 40min, but not limited to the recited values, and other values not recited in the numerical range are equally applicable.
Preferably, the stirring temperature is 30-50 ℃, for example 30 ℃, 35 ℃, 40 ℃, 45 ℃ or 50 ℃, but not limited to the recited values, and other values not recited in the numerical range are equally applicable.
Preferably, the stirring time is 6 to 10 hours, for example 6 hours, 6.5 hours, 7 hours, 8 hours, 9 hours or 10 hours, but is not limited to the recited values, and other values not recited in the numerical range are equally applicable.
Preferably, the magnesium source of step (2) comprises magnesium powder.
Preferably, the mixing of step (2) further comprises mixing a salt. The salt is NaCl and/or CaCl2。
In the magnesiothermic reduction reaction, the effect of adding salt: used as an endothermic agent, to avoid a sharp increase in internal temperature.
Preferably, the mass ratio of the magnesium source, the precursor obtained in step (2) and the salt is (0.8-1.2):1: 9-11), and may be, for example, 0.8:1:9, 1.2:1:11, 1:1:10, 0.8:1:11 or 1.2:1:9, but is not limited to the values recited, and other values not recited in the range of values are equally applicable.
Preferably, the mixing in step (2) further comprises grinding.
Preferably, mixed gas is introduced during the temperature-rising reduction process in the step (2).
Preferably, the gas mixture comprises at least two of hydrogen, argon, helium or nitrogen, typical but non-limiting combinations include combinations of hydrogen and argon, argon and helium, helium and nitrogen, hydrogen, argon and helium, argon, helium and nitrogen, or hydrogen, argon, helium and nitrogen.
A small amount of silicon carbide is formed at the silicon-carbon interface due to the large amount of heat released by the thermal reaction of magnesium. The silicon carbide is beneficial to protecting the structural stability of the whole material, and prevents a new surface from contacting electrolyte to generate a new SEI film after the structure is broken.
Preferably, the gas is introduced in a flow rate of 0.02-0.05L/min, for example 0.02L/min, 0.03L/min, 0.04L/min, 0.045L/min or 0.05L/min, but not limited to the values cited, and other values not listed in the range of values are equally suitable.
Preferably, the temperature raising rate of the temperature raising in the step (2) is 2-10 ℃/min, for example, 2 ℃/min, 3 ℃/min, 5 ℃/min, 6 ℃/min, 8 ℃/min, 9 ℃/min or 10 ℃/min, but not limited to the values listed, and other values not listed in the numerical range are also applicable.
Preferably, the reaction temperature of the reduction in step (2) is 600-.
Preferably, the temperature-rising reduction process in the step (2) comprises acid washing after the temperature-rising reduction process is finished.
Preferably, the acid wash comprises any one or a combination of at least two of hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid, typical but non-limiting combinations include a combination of hydrochloric acid and sulfuric acid, a combination of sulfuric acid and nitric acid, a combination of nitric acid and phosphoric acid, a combination of hydrochloric acid, sulfuric acid, and nitric acid, a combination of sulfuric acid, nitric acid, and phosphoric acid, or a combination of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.
As a preferable technical solution of the preparation method of the first aspect of the present invention, the preparation method comprises the steps of:
(1) mixing a carbon source solution, a nano silicon dioxide solution and an aldehyde compound in a volume ratio of (9-12) to (4-6), wherein the concentration of the carbon source is 5-10mg/mL, the concentration of a hydrolysis catalyst in the carbon source solution is 2-3mg/mL, the concentration of the nano silicon dioxide is 0.01-0.015g/mL, performing ultrasonic dispersion for 20-40min, and stirring at the temperature of 30-50 ℃ for 6-10h to obtain a precursor;
the preparation method of the nano silicon dioxide comprises the following steps: mixing an organic silicon source solution and a hydrolysis catalyst solution, wherein the concentration of the organic silicon source is 0.02-0.04g/ml, the concentration of the hydrolysis catalyst is 0.3-0.4mg/ml, stirring at the rotating speed of 500-700r/min for 4-6h, centrifuging, washing and drying to obtain the nano silicon dioxide;
(2) mixing magnesium powder, the obtained precursor and salt according to the mass ratio of (0.8-1.2) to (1) (9-11), introducing mixed gas with the flow of 0.02-0.05L/min, heating at 2-10 ℃/min to the reaction temperature of 600-800 ℃ for reduction reaction, and pickling after the reaction is finished to obtain the composite cathode material;
the carbon source comprises any one or the combination of at least two of m-diphenol, polyvinylpyrrolidone, o-diphenol, p-diphenol or alpha-phenol naphthalene; the particle size range of the nano silicon dioxide is 200-500 nm; the organic silicon source comprises any one or the combination of at least two of tetraethoxysilane, diallyl phenyl dimethyl silane, triethoxysilane or methyl triallyl silane.
In a second aspect, the present invention provides a composite anode material obtained by the preparation method of the first aspect.
In a third aspect, the invention provides a lithium ion battery comprising the composite anode material according to the second aspect.
Compared with the prior art, the invention has at least the following beneficial effects:
the method simplifies the traditional two-step method for preparing the carbon-coated nano silicon cathode material by magnesium thermal reduction, realizes the preparation of the carbon-coated nano silicon cathode material by one-step magnesium thermal reduction reaction, reduces energy consumption and process flow, and is easy for large-scale production. Meanwhile, the preparation method provided by the invention reduces the influence of volume expansion in the process of embedding lithium in silicon, and maintains the structural stability of the cathode material. The outermost layer is coated with the carbon material, so that the conductivity of the negative electrode is improved, the impedance is reduced, the activity of the electrode material is improved, and the cycle performance of the material is improved; according to the composite cathode material provided by the invention, silicon carbide is generated at the silicon-carbon interface, so that the structural stability of the composite cathode material is further kept.
Detailed Description
For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides a preparation method of a composite anode material, which comprises the following steps:
(1) mixing an m-diphenol solution, a nano-silica solution and acetaldehyde in a volume ratio of 1:10:5, performing ultrasonic dispersion for 30min, and stirring at the temperature of 40 ℃ for 8h to obtain a precursor;
the resorcinol solution comprises resorcinol, an ethanol solvent and ammonia water, wherein the concentration of the resorcinol is 8mg/ml, and the concentration of the ammonia water is 2.5 mg/ml;
the preparation method of the nano silicon dioxide comprises the following steps: mixing tetraethoxysilane and ammonia water in an ethanol solvent, wherein the concentration of the tetraethoxysilane is 0.03g/ml, the concentration of the ammonia water is 0.35mg/ml, stirring for 5 hours at the rotating speed of 600r/min, washing by deionized water and drying to obtain the nano silicon dioxide, and the particle size range of the nano silicon dioxide is 200-500 nm;
the nano silicon dioxide solution consists of deionized water, hexadecyl trimethyl ammonium bromide and nano silicon dioxide, wherein the concentration of the hexadecyl trimethyl ammonium bromide is 0.035g/mL, and the concentration of the nano silicon dioxide is 0.012 g/mL;
(2) mixing magnesium powder, the obtained precursor and sodium chloride according to the mass ratio of 1:1:10, introducing mixed gas of argon and hydrogen with the flow rate of 0.04L/min, heating at 7 ℃/min, heating to the reaction temperature of 700 ℃ for reduction reaction, carrying out acid washing after the reaction is finished, wherein the washing liquid of the acid washing is hydrochloric acid, and thus the composite negative electrode material is obtained.
Example 2
The embodiment provides a preparation method of a composite anode material, which comprises the following steps:
(1) mixing an m-diphenol solution, a nano-silica solution and formaldehyde in a volume ratio of 1:9:4, performing ultrasonic dispersion for 20min, and stirring at the temperature of 50 ℃ for 6h to obtain a precursor;
the resorcinol solution comprises resorcinol, an ethanol solvent and ammonia water, wherein the concentration of the resorcinol is 6mg/ml, and the concentration of the ammonia water is 2.8 mg/ml;
the preparation method of the nano silicon dioxide comprises the following steps: mixing diallyl phenyl dimethylsilane and ammonia water in ethanol, wherein the concentration of the obtained diallyl phenyl dimethylsilane is 0.025g/ml, the concentration of the ammonia water is 0.3mg/ml, stirring for 6 hours at the rotating speed of 500r/min, washing by deionized water and drying to obtain the nano silicon dioxide, and the particle size range of the nano silicon dioxide is 200-500 nm;
the nano-silica solution consists of deionized water, sodium stearate and nano-silica, wherein the concentration of the sodium stearate is 0.03g/mL, and the concentration of the nano-silica is 0.01 g/mL;
(2) mixing magnesium powder, the obtained precursor and calcium chloride according to the mass ratio of 0.8:1:9, introducing mixed gas of argon and nitrogen with the flow of 0.02L/min, heating at the speed of 2 ℃/min, heating to the reaction temperature of 600 ℃ for reduction reaction, carrying out acid washing after the reaction is finished, wherein the washing liquid of the acid washing is sulfuric acid, and thus the composite negative electrode material is obtained.
Example 3
The embodiment provides a preparation method of a composite anode material, which comprises the following steps:
(1) mixing an o-diphenol solution, a nano-silica solution and formaldehyde in a volume ratio of 1:12:6, performing ultrasonic dispersion for 40min, and stirring at the temperature of 50 ℃ for 6h to obtain a precursor;
the o-diphenol solution comprises o-diphenol, an ethanol solvent and ammonia water, wherein the concentration of the o-diphenol is 10mg/ml, and the concentration of the ammonia water is 3 mg/ml;
the preparation method of the nano silicon dioxide comprises the following steps: mixing triethoxysilane and ammonia water in ethanol to obtain triethoxysilane with a concentration of 0.04g/ml and ammonia water with a concentration of 0.4mg/ml, stirring at a rotation speed of 700r/min for 6h, washing with deionized water, and drying to obtain the nano-silica with a particle size range of 200-500 nm;
the nano-silica solution consists of deionized water, sodium dodecyl benzene sulfonate and nano-silica, wherein the concentration of the sodium dodecyl benzene sulfonate is 0.04g/mL, and the concentration of the nano-silica is 0.015 g/mL;
(2) mixing magnesium powder, the obtained precursor and sodium chloride according to the mass ratio of 1.2:1:11, introducing mixed gas of nitrogen and hydrogen with the flow of 0.05L/min, heating at 10 ℃/min, heating to the reaction temperature of 800 ℃ for reduction reaction, carrying out acid washing after the reaction is finished, wherein the washing liquid of the acid washing is phosphoric acid, and obtaining the composite negative electrode material.
Example 4
The embodiment provides a preparation method of a composite anode material, which comprises the following steps:
(1) mixing a p-diphenol solution, a nano-silica solution and acetaldehyde in a volume ratio of 1:12:4, performing ultrasonic dispersion for 30min, and stirring at the temperature of 40 ℃ for 8h to obtain a precursor;
the p-diphenol solution comprises p-diphenol, an ethanol solvent and ammonia water, wherein the concentration of the p-diphenol is 9mg/ml, and the concentration of the ammonia water is 2.2 mg/ml;
the preparation method of the nano silicon dioxide comprises the following steps: mixing methyl triallyl silane and ammonia water in an ethanol solvent, wherein the concentration of the obtained methyl triallyl silane is 0.02g/ml, the concentration of the ammonia water is 0.4mg/ml, stirring for 5 hours at the rotating speed of 600r/min, washing by deionized water and drying to obtain the nano silicon dioxide, and the particle size range of the nano silicon dioxide is 200-500 nm;
the nano silicon dioxide solution consists of deionized water, hexadecyl trimethyl ammonium bromide and nano silicon dioxide, wherein the concentration of the hexadecyl trimethyl ammonium bromide is 0.03g/mL, and the concentration of the nano silicon dioxide is 0.01 g/mL;
(2) mixing magnesium powder, the obtained precursor and sodium chloride according to the mass ratio of 0.8:1:11, introducing mixed gas of argon and hydrogen with the flow of 0.04L/min, heating at 7 ℃/min, heating to the reaction temperature of 700 ℃ for reduction reaction, carrying out acid washing after the reaction is finished, wherein the washing liquid of the acid washing is nitric acid, and thus the composite negative electrode material is obtained.
Example 5
The embodiment provides a preparation method of a composite anode material, which comprises the following steps:
(1) mixing an alpha-phenol naphthalene solution, a nano-silica solution and acetaldehyde in a volume ratio of 1:10:6, performing ultrasonic dispersion for 30min, and stirring at the temperature of 40 ℃ for 8h to obtain a precursor;
the alpha-phenol naphthalene solution comprises alpha-phenol naphthalene, an ethanol solvent and ammonia water, wherein the concentration of the alpha-phenol naphthalene is 10mg/ml, and the concentration of the ammonia water is 3 mg/ml;
the preparation method of the nano silicon dioxide comprises the following steps: mixing methyl triallyl silane and ammonia water in an ethanol solvent, wherein the concentration of the obtained methyl triallyl silane is 0.04g/ml, the concentration of the ammonia water is 0.4mg/ml, stirring for 5 hours at the rotating speed of 600r/min, washing by deionized water and drying to obtain the nano silicon dioxide, and the particle size range of the nano silicon dioxide is 200-500 nm;
the nano silicon dioxide solution consists of deionized water, hexadecyl trimethyl ammonium bromide and nano silicon dioxide, wherein the concentration of the hexadecyl trimethyl ammonium bromide is 0.035g/mL, and the concentration of the nano silicon dioxide is 0.012 g/mL;
(2) mixing magnesium powder, the obtained precursor and sodium chloride according to the mass ratio of 1:1:9, introducing mixed gas of argon and hydrogen with the flow of 0.05L/min, heating at 7 ℃/min, heating to the reaction temperature of 700 ℃ for reduction reaction, carrying out acid washing after the reaction is finished, wherein the washing liquid of the acid washing is nitric acid, and thus the composite negative electrode material is obtained.
Example 6
The embodiment provides a preparation method of a composite anode material, which comprises the following steps:
(1) mixing m-diphenol, a nano-silica solution and acetaldehyde, performing ultrasonic dispersion for 30min, and stirring at the temperature of 40 ℃ for 8h to obtain a precursor;
the particle size range of the nano silicon dioxide is 100-200 nm;
the nano silicon dioxide solution consists of deionized water, hexadecyl trimethyl ammonium bromide and nano silicon dioxide, wherein the concentration of the hexadecyl trimethyl ammonium bromide is 0.035g/mL, and the concentration of the nano silicon dioxide is 0.012 g/mL;
(2) and mixing magnesium powder, the obtained precursor and sodium chloride, introducing a mixed gas of argon and hydrogen, heating at 7 ℃/min, heating to the reaction temperature of 700 ℃ for reduction reaction, and carrying out acid washing after the reaction is finished, wherein the washing liquid of the acid washing is hydrochloric acid, so as to obtain the composite negative electrode material.
Example 7
The embodiment provides a preparation method of a composite anode material, which comprises the following steps:
(1) mixing m-diphenol, a nano-silica solution and acetaldehyde, performing ultrasonic dispersion for 30min, and stirring at the temperature of 40 ℃ for 8h to obtain a precursor;
the particle size range of the nano silicon dioxide is 500-1000 nm;
the nano silicon dioxide solution consists of deionized water, hexadecyl trimethyl ammonium bromide and nano silicon dioxide, wherein the concentration of the hexadecyl trimethyl ammonium bromide is 0.035g/mL, and the concentration of the nano silicon dioxide is 0.012 g/mL;
(2) and mixing magnesium powder, the obtained precursor and sodium chloride, introducing a mixed gas of argon and hydrogen, heating at 7 ℃/min, heating to the reaction temperature of 700 ℃ for reduction reaction, and carrying out acid washing after the reaction is finished, wherein the washing liquid of the acid washing is hydrochloric acid, so as to obtain the composite negative electrode material.
Example 8
This example provides a method for preparing a composite negative electrode material, which is the same as in example 1 except that m-diphenol in step (1) is replaced with equal-mass graphite.
Example 9
This example provides a method for preparing a composite anode material, which comprises the same steps as example 1 except that the concentration of hexadecyl trimethyl ammonium bromide in step (1) is 0.02 g/mL.
Example 10
This example provides a method for preparing a composite anode material, which comprises the same steps as example 1 except that the concentration of hexadecyl trimethyl ammonium bromide in step (1) is 0.05 g/mL.
Example 11
The embodiment provides a preparation method of a composite anode material, and the process steps are the same as those in the embodiment 1 except that the concentration of the nano silicon dioxide in the step (1) is 0.008 g/mL.
Example 12
The embodiment provides a preparation method of a composite anode material, and the steps of the preparation method are the same as those of the embodiment 1 except that the concentration of the nano silicon dioxide in the step (1) is 0.02 g/mL.
Example 13
The embodiment provides a preparation method of a composite anode material, and the rest process steps are the same as those in the embodiment 1 except that the heating rate in the step (2) is 1 ℃/min.
Example 14
The embodiment provides a preparation method of a composite anode material, and the process steps are the same as those in the embodiment 1 except that the heating rate in the step (2) is 12 ℃/min.
Comparative example 1
The present comparative example provides a preparation method of a composite anode material, which is referred to CN106374088A, wherein the mass ratio of magnesium powder, silicon element and carbon element is the same as that of example 1.
Comparative example 2
The present comparative example provides a nano-silicon anode material (CW-Si-001).
And (3) assembling the composite negative electrode material into a lithium ion battery according to the standard of GB 31241-2014.
The test method comprises the following steps: for the obtained lithium ion battery, circulating for 3 circles under the current density of 0.21A/g in the voltage range of 3-0.01V to obtain the first coulombic efficiency. After 230 cycles at a current density of 0.84A/g, reversible capacity was obtained. The results are shown in Table 1.
TABLE 1
| Test number | First coulombic efficiency (%) | Reversible circulation capacity (mAh/g) |
| Example 1 | 73.43 | 1239.3 |
| Example 2 | 70.24 | 989.5 |
| Example 3 | 70.45 | 993.8 |
| Example 4 | 71.35 | 1123.6 |
| Example 5 | 71.67 | 1146.3 |
| Example 6 | 68.48 | 943.5 |
| Example 7 | 67.68 | 923.6 |
| Example 8 | 64.54 | 823.6 |
| Example 9 | 70.24 | 971.3 |
| Example 10 | 70.38 | 967.7 |
| Example 11 | 72.34 | 843.5 |
| Example 12 | 69.71 | 924.6 |
| Example 13 | 67.67 | 911.6 |
| Example 14 | 68.83 | 921.5 |
| Comparative example 1 | 65.44 | 873.7 |
| Comparative example 2 | 72.4 | 232.3 |
From the data in table 1, the following conclusions can be drawn:
(1) from examples 1-5, the method simplifies the traditional two-step magnesiothermic reduction preparation of the carbon-coated nano silicon cathode material, realizes the preparation of the carbon-coated nano silicon cathode material through one-step magnesiothermic reduction reaction, reduces energy consumption and process flow, and is easy for large-scale production. Meanwhile, the preparation method provided by the invention reduces the influence of volume expansion in the process of embedding lithium in silicon, and maintains the structural stability of the cathode material. The outermost layer is coated with the carbon material, so that the conductivity of the negative electrode is improved, the impedance is reduced, the activity of the electrode material is improved, and the cycle performance of the material is improved; according to the composite cathode material provided by the invention, silicon carbide is generated at the silicon-carbon interface, so that the structural stability of the composite cathode material is further kept.
(2) From the comparison between examples 6 and 7 and example 1, it can be seen that when the particle size range of the nano-silica exceeds 200-500nm, the first coulombic efficiency of the prepared composite anode material is low, and the reversible cycle capacity is low, which indicates that the particle size range of the nano-silica provided by the invention is beneficial to preparing the composite anode material with structural stability and excellent electrochemical performance.
(3) From the comparison between the embodiment 8 and the embodiment 1, when the carbon source is replaced by graphite, the prepared composite anode material has low coulombic efficiency and low reversible cycle capacity for the first time, which shows that the carbon source provided by the invention is beneficial to preparing the composite anode material with structural stability and excellent electrochemical performance.
(4) From the comparison between examples 9 and 10 and example 1, it can be seen that when the concentration of the hexadecyl trimethyl ammonium bromide exceeds 0.03-0.04g/mL, the prepared composite anode material has low first coulombic efficiency and low reversible cycle capacity, which indicates that the concentration of the surfactant provided by the invention is beneficial to preparing the composite anode material with structural stability and excellent electrochemical performance.
(5) From the comparison between examples 11 and 12 and example 1, it can be seen that when the concentration of silica exceeds 0.01-0.015g/mL, the prepared composite anode material has low first coulombic efficiency and low reversible cycle capacity, which indicates that the concentration of silica provided by the invention is beneficial to preparing composite anode materials with structural stability and excellent electrochemical performance.
(6) From the comparison between examples 13 and 14 and example 1, it can be seen that when the temperature rise rate of the magnesium thermal reaction exceeds 2-10 ℃/min, the prepared composite anode material has low initial coulombic efficiency and low reversible cycle capacity, which indicates that the temperature rise rate of the magnesium thermal reaction provided by the invention is beneficial to preparing the composite anode material with structural stability and excellent electrochemical performance.
(7) Compared with the magnesium thermal method in the prior art, the preparation method provided by the application has the advantages that the first coulombic efficiency of the obtained composite negative electrode material is high, the reversible cycle capacity is high, the preparation method for preparing the carbon-coated nano silicon by the magnesium thermal method is improved, and the composite negative electrode material with a stable structure and excellent electrochemical performance is obtained.
(8) Compared with the silicon negative electrode material in the prior art, the preparation method provided by the application has high first coulombic efficiency and high reversible cycle capacity, the preparation method for preparing the carbon-coated nano silicon by the magnesium thermal method is improved, and the composite negative electrode material with a stable structure and excellent electrochemical performance is obtained.
The applicant states that the process flow of the present invention is illustrated by the above examples, but the present invention is not limited to the above process flow, i.e. it is not meant to imply that the present invention must be implemented by relying on the above detailed process flow. 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 preparation method of the composite anode material is characterized by comprising the following steps of:
(1) mixing a carbon source solution, a silicon dioxide solution and a reducing agent to obtain a precursor;
(2) and (3) mixing a magnesium source with the precursor obtained in the step (1), and heating and reducing to obtain the composite negative electrode material.
2. The production method according to claim 1, wherein the carbon source solution of step (1) comprises a carbon source, a solvent and a hydrolysis catalyst;
preferably, the carbon source comprises any one or a combination of at least two of resorcinol, polyvinylpyrrolidone, o-diphenol, p-diphenol or alpha-phenol naphthalene, preferably resorcinol;
preferably, in the carbon source solution in the step (1), the concentration of the carbon source is 5-10 mg/ml;
preferably, the solvent comprises methanol and/or ethanol;
preferably, the hydrolysis catalyst comprises aqueous ammonia;
preferably, in the carbon source solution in the step (1), the concentration of the hydrolysis catalyst is 2-3 mg/ml.
3. The production method according to claim 1 or 2, wherein the silica solution of step (1) comprises water, a surfactant and silica;
preferably, the surfactant comprises any one of or a combination of at least two of hexadecyl trimethyl ammonium bromide, sodium stearate or sodium dodecyl benzene sulfonate;
preferably, in the silicon dioxide solution in the step (1), the concentration of the surfactant is 0.03-0.04 g/mL;
preferably, in the silica solution in the step (1), the concentration of the silica is 0.01-0.015 g/mL;
preferably, the silica comprises nanosilica;
preferably, the particle size of the nano-silica is in the range of 200-500 nm.
4. The method according to claim 3, wherein the method for preparing nano silica comprises: mixing an organic silicon source solution and a hydrolysis catalyst solution, centrifuging, washing and drying to obtain the nano silicon dioxide;
preferably, the solvent of the organic silicon source solution comprises an alcohol;
preferably, the concentration of the organic silicon source in the organic silicon source solution is 0.02-0.04 g/ml;
preferably, the organic silicon source comprises any one or a combination of at least two of ethyl orthosilicate, diallylphenyldimethylsilane, triethoxysilane or methyltriallylsilane;
preferably, the solvent of the hydrolysis catalyst solution comprises a water-alcohol mixture;
preferably, the volume ratio of water to alcohol in the water-alcohol mixed solution is (1.5-2): 1;
preferably, the concentration of the hydrolysis catalyst in the hydrolysis catalyst solution is 0.3-0.4 mg/ml;
preferably, the hydrolysis catalyst comprises aqueous ammonia;
preferably, the means of mixing comprises stirring;
preferably, the rotation speed of the stirring is 500-700r/min, and the time is 4-6 h.
5. The process according to any one of claims 1 to 4, wherein the reducing agent of step (1) comprises an aldehyde compound, preferably formaldehyde and/or acetaldehyde;
preferably, the volume ratio of the carbon source solution, the silicon dioxide solution and the reducing agent in the step (1) is 1 (9-12) to (4-6);
preferably, the mixing of step (1) comprises ultrasonic dispersion and/or stirring;
preferably, the time of ultrasonic dispersion is 20-40 min;
preferably, the stirring temperature is 30-50 ℃ and the stirring time is 6-10 h.
6. The production method according to any one of claims 1 to 5, wherein the magnesium source of step (2) comprises magnesium powder;
preferably, the mixing of step (2) further comprises mixing a salt;
preferably, the mass ratio of the magnesium source, the precursor and the salt in the step (2) is (0.8-1.2):1 (9-11).
7. The method according to any one of claims 1 to 6, wherein, between the mixing and the temperature-raising reduction in the step (2), grinding is further included;
preferably, mixed gas is introduced in the temperature-rising reduction process in the step (2);
preferably, the mixed gas includes at least two of hydrogen, argon, helium, or nitrogen;
preferably, the flow rate of the mixed gas is 0.02-0.05L/min;
preferably, the heating rate of the heating reduction in the step (2) is 2-10 ℃/min;
preferably, the reaction temperature of the temperature-rising reduction in the step (2) is 600-800 ℃;
preferably, after the temperature-rising reduction process in the step (2) is finished, acid washing is carried out to obtain the composite negative electrode material;
preferably, the acid wash comprises any one of hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid or a combination of at least two thereof.
8. The production method according to any one of claims 1 to 7, characterized by comprising the steps of:
(1) mixing a carbon source solution, a nano silicon dioxide solution and an aldehyde compound in a volume ratio of (9-12) to (4-6), wherein the concentration of the carbon source is 5-10mg/mL, the concentration of a hydrolysis catalyst in the carbon source solution is 2-3mg/mL, the concentration of the nano silicon dioxide is 0.01-0.015g/mL, performing ultrasonic dispersion for 20-40min, and stirring at the temperature of 30-50 ℃ for 6-10h to obtain a precursor;
the preparation method of the nano silicon dioxide comprises the following steps: mixing an organic silicon source solution and a hydrolysis catalyst solution, wherein the concentration of the organic silicon source is 0.02-0.04g/ml, the concentration of the hydrolysis catalyst is 0.3-0.4mg/ml, stirring at the rotating speed of 500-700r/min for 4-6h, centrifuging, washing and drying to obtain the nano silicon dioxide;
(2) mixing magnesium powder, the obtained precursor and salt according to the mass ratio of (0.8-1.2) to (1) (9-11), introducing mixed gas with the flow of 0.02-0.05L/min, heating at 2-10 ℃/min, heating to the reaction temperature of 600-800 ℃ for reduction reaction, and carrying out acid cleaning after the reaction is finished to obtain the composite negative electrode material;
the carbon source comprises any one or the combination of at least two of m-diphenol, polyvinylpyrrolidone, o-diphenol, p-diphenol or alpha-phenol naphthalene; the particle size range of the nano silicon dioxide is 200-500 nm; the organic silicon source comprises any one or the combination of at least two of tetraethoxysilane, diallyl phenyl dimethyl silane, triethoxysilane or methyl triallyl silane.
9. A composite anode material, characterized in that it is obtained by the production method according to any one of claims 1 to 8.
10. A lithium ion battery comprising the composite anode material according to claim 9.
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