CN110380029B - Silicon-based negative electrode material for lithium battery and preparation method thereof - Google Patents
Silicon-based negative electrode material for lithium battery and preparation method thereof Download PDFInfo
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 109
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 95
- 239000010703 silicon Substances 0.000 title claims abstract description 95
- 239000007773 negative electrode material Substances 0.000 title claims abstract description 41
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 29
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 27
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 78
- 239000002245 particle Substances 0.000 claims abstract description 41
- 229910021389 graphene Inorganic materials 0.000 claims abstract description 38
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 27
- 229910021419 crystalline silicon Inorganic materials 0.000 claims abstract description 24
- 239000000463 material Substances 0.000 claims abstract description 23
- 230000014759 maintenance of location Effects 0.000 claims abstract description 14
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 13
- 239000010439 graphite Substances 0.000 claims abstract description 13
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims abstract description 13
- 239000011863 silicon-based powder Substances 0.000 claims abstract description 13
- 239000000203 mixture Substances 0.000 claims abstract description 9
- 238000005253 cladding Methods 0.000 claims abstract description 5
- 241000219991 Lythraceae Species 0.000 claims abstract description 3
- 235000014360 Punica granatum Nutrition 0.000 claims abstract description 3
- 239000002210 silicon-based material Substances 0.000 claims description 55
- 239000000243 solution Substances 0.000 claims description 31
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 24
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 19
- 239000011889 copper foil Substances 0.000 claims description 19
- 229910021426 porous silicon Inorganic materials 0.000 claims description 17
- 239000002002 slurry Substances 0.000 claims description 14
- 238000000151 deposition Methods 0.000 claims description 13
- 238000001035 drying Methods 0.000 claims description 13
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 12
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 12
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 12
- 239000008367 deionised water Substances 0.000 claims description 12
- 229910021641 deionized water Inorganic materials 0.000 claims description 12
- 238000005530 etching Methods 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 12
- 229910017604 nitric acid Inorganic materials 0.000 claims description 12
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 claims description 12
- 238000005406 washing Methods 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 239000011248 coating agent Substances 0.000 claims description 10
- 238000000576 coating method Methods 0.000 claims description 10
- 238000005245 sintering Methods 0.000 claims description 8
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 7
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 7
- 229910021642 ultra pure water Inorganic materials 0.000 claims description 7
- 239000012498 ultrapure water Substances 0.000 claims description 7
- 239000002253 acid Substances 0.000 claims description 6
- 238000000498 ball milling Methods 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 6
- 230000008021 deposition Effects 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 6
- 239000011259 mixed solution Substances 0.000 claims description 6
- 229910001961 silver nitrate Inorganic materials 0.000 claims description 6
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 19
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 19
- 239000005543 nano-size silicon particle Substances 0.000 abstract description 12
- 239000003575 carbonaceous material Substances 0.000 abstract description 7
- 239000010406 cathode material Substances 0.000 abstract description 5
- 238000000034 method Methods 0.000 description 11
- 230000000694 effects Effects 0.000 description 10
- 239000002131 composite material Substances 0.000 description 9
- 239000010408 film Substances 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 239000003792 electrolyte Substances 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 230000007547 defect Effects 0.000 description 3
- 230000002427 irreversible effect Effects 0.000 description 3
- 239000002105 nanoparticle Substances 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000013329 compounding Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 230000002441 reversible effect Effects 0.000 description 2
- 229910052709 silver Inorganic materials 0.000 description 2
- 239000004332 silver Substances 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- 229910000733 Li alloy Inorganic materials 0.000 description 1
- 229920002472 Starch Polymers 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000005562 fading Methods 0.000 description 1
- 239000007770 graphite material Substances 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000001989 lithium alloy Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000007709 nanocrystallization Methods 0.000 description 1
- 239000002070 nanowire Substances 0.000 description 1
- 239000011255 nonaqueous electrolyte Substances 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 238000009751 slip forming Methods 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 235000019698 starch Nutrition 0.000 description 1
- 239000008107 starch Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
Classifications
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- 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
- H01M4/364—Composites as mixtures
-
- 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
-
- 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
-
- 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 discloses a silicon-based negative electrode material for a lithium battery, which comprises a silicon source material and a carbon source material, wherein the silicon source material and the carbon source material are compounded into a compact cladding body in a pomegranate-shaped structure, the carbon source wraps the silicon source, and the silicon source is tightly distributed in gaps of the carbon source; the silicon source comprises polycrystalline silicon powder with the particle size of 10-50um, crystalline silicon with the particle size of 100-500nm and crystalline silicon with the particle size of 10-50 nm; the silicon source comprises a mixture of graphite and graphene in equal parts by mass; the specific capacity of the silicon-based negative electrode material after 500 times of circulation is 1214-1236mAh/g, and the capacity retention rate after 500 times of circulation is 93.11-93.51%. The invention also discloses a preparation method of the silicon-based negative electrode material for the lithium battery. The invention solves the technical problem that when the nano silicon-based material and the carbon material are compounded into a pomegranate type structure, the volume specific capacity of the lithium ion battery cathode is reduced due to the reduction of the tap density of the nano silicon-based/carbon cathode material.
Description
Technical Field
The invention relates to the technical field of lithium battery cathode materials, in particular to a silicon-based cathode material for a lithium battery and a preparation method thereof.
Background
Lithium batteries, which are batteries using a nonaqueous electrolyte solution and using lithium metal or lithium alloy as a negative electrode material; lithium batteries can be broadly classified into two types: lithium metal batteries and lithium ion batteries.
Compared with the traditional graphite material used as the lithium ion battery cathode material, the silicon has ultrahigh theoretical specific capacity and lower lithium removal potential, and the voltage platform of the silicon is slightly higher than that of the graphite, so that the surface lithium precipitation is not easy to cause during charging, and the safety performance is better, therefore, the silicon-based material becomes one of the potential choices for upgrading and updating the lithium ion battery carbon-based cathode.
However, silicon has disadvantages as a negative electrode material for lithium ion batteries. Firstly, silicon is a semiconductor material and has low self conductivity; secondly, in the electrochemical cycle process, the insertion and extraction of lithium ions can cause the volume of the material to expand and contract by more than 300%, the generated mechanical acting force can gradually pulverize the material to cause structural collapse, and finally, the electrode active substance is separated from the current collector to lose electrical contact, so that the cycle performance of the battery is greatly reduced. In addition, due to such a volume effect, it is difficult for silicon to form a stable solid electrolyte interface film in an electrolyte solution, and a new fixed electrolyte interface film is continuously formed on the exposed silicon surface accompanying the destruction of the electrode structure, which accelerates the corrosion and capacity fade of silicon.
In order to improve the cycle performance of the silicon-based negative electrode and improve the structural stability of the material in the cycle process, the silicon material is generally subjected to nano-crystallization and composite treatment.
The silicon nano particles and the three-dimensional porous silicon can inhibit the volume effect of the material to a certain extent, and simultaneously can reduce the diffusion distance of lithium ions and improve the electrochemical reaction rate. However, they have large specific surface areas, which increase direct contact with the electrolyte, resulting in side reactions and an increase in irreversible capacity, and a decrease in coulombic efficiency. In addition, the silicon active particles are easy to agglomerate in the charging and discharging process, and electrochemical sintering is generated, so that capacity fading is accelerated.
The silicon nanowire/tube can reduce the radial volume change in the charging and discharging process, realize good circulation stability and provide a rapid lithium ion transmission channel in the axial direction. But the tap density of the silicon material is reduced, so that the specific volume capacity of the silicon negative electrode is reduced. The silicon film can reduce the volume change generated in the direction vertical to the film, and maintain the structural integrity of the electrode. However, after many cycles, the silicon thin film is easily broken and separated from the substrate, and the preparation cost of the silicon thin film is high.
The metal component in the silicon/metal type composite can improve the electronic conductance of the material, reduce the polarization of the silicon material and improve the multiplying power performance of the silicon material. The ductility of the metal can inhibit the volume effect of the silicon material to a certain extent and improve the cycle performance, but the silicon structure defects generated in the preparation process have high electrochemical activity and can cause the irreversible capacity to be increased. And the compounding of silicon and metal can not avoid direct contact of active silicon and electrolyte, and an unstable SEI film is generated, so that the cycle performance of the battery is reduced.
In the silicon/carbon type compounding, the carbon material has higher electronic conductivity and ionic conductivity, so that the rate capability of the silicon-based material can be improved, and the volume effect of silicon in the circulating process is inhibited. In addition, the carbon material can prevent the silicon from directly contacting with the electrolyte, and the irreversible capacity is reduced. But the defects are that the interface contact between the silicon material and the carbon material is poor, and the difficulty of completely and uniformly coating the inner wall of the hole with the nanometer scale of the silicon material with carbon is high.
The nano method and the composite method are combined to prepare the porous silicon/carbon composite material, wherein the porous structure can effectively buffer the volume expansion, and the composite with the carbon material can avoid the agglomeration of nano particles in the circulation process, thereby improving the initial efficiency, the circulation stability and the rate capability.
The invention patent with the patent publication number of CN105261733A discloses a preparation method of a nano silicon-based/carbon composite material, which comprises the steps of firstly coating a microporous carbon layer on the surface of a nano silicon by adopting organic resin and a pore-forming agent in a liquid phase, then adopting fermented starch as a carbon source, and carrying out coating and high-temperature carbonization. The method can be used for preparing the pomegranate-shaped structural characteristic nano silicon-based/carbon composite material, when the composite material is applied to manufacturing a lithium ion battery cathode material, the problems of rapid volume expansion in a lithium embedding process and particle crushing, pulverization and falling in a circulating process can be effectively solved, the specific capacity of the material reaches 450 mAh/g, and the capacity retention rate is 85-92% after 500-week circulating charge and discharge. However, in the technical scheme, the tap density of the material can be reduced by the pomegranate-type structural characteristic nano silicon-based/carbon composite material, so that the volume specific capacity of the negative electrode is reduced, and the technical problem that the reversible specific capacity and the cycle performance of the lithium ion battery can not be further improved is solved.
The invention provides a silicon-based negative electrode material for a lithium battery and a preparation method thereof, and aims to solve the technical problem that when a nano silicon-based material and a carbon material are compounded into a pomegranate-shaped structure, the volume specific capacity of a negative electrode of the lithium battery is reduced due to the reduction of the tap density of the nano silicon-based/carbon negative electrode material.
Disclosure of Invention
Technical problem to be solved
Aiming at the defects of the prior art, the invention provides a silicon-based negative electrode material for a lithium battery and a preparation method thereof, and solves the technical problem that when a nano silicon-based material and a carbon material are compounded into a pomegranate type structure, the volume specific capacity of a negative electrode of the lithium battery is reduced due to the reduction of the tap density of the nano silicon-based/carbon negative electrode material.
(II) technical scheme
In order to achieve the purpose, the invention provides the following technical scheme:
the silicon-based negative electrode material for the lithium battery comprises a silicon source material and a carbon source material, wherein the silicon source material and the carbon source material are compounded into a compact cladding body in a pomegranate-shaped structure, the carbon source wraps the silicon source, and the silicon source is tightly distributed in gaps of the carbon source;
the silicon source comprises polycrystalline silicon powder with the particle size of 10-50um, crystalline silicon with the particle size of 100-500nm and crystalline silicon with the particle size of 10-50 nm;
the silicon source comprises a mixture of graphite and graphene in equal parts by mass;
the specific capacity of the silicon-based negative electrode material after 500 times of circulation is 1214-1236mAh/g, and the capacity retention rate after 500 times of circulation is 93.11-93.51%.
Preferably, the silicon source is polycrystalline silicon powder with the particle size of 30um, crystalline silicon with the particle size of 200nm and crystalline silicon with the particle size of 30 nm.
Preferably, the silicon source comprises the following raw materials in parts by weight: 2 parts of polycrystalline silicon powder with the particle size of 30um, 6 parts of crystalline silicon with the particle size of 200nm and 3 parts of crystalline silicon with the particle size of 30 nm.
Preferably, the specific capacity of the silicon-based negative electrode material after 500 cycles is 1236mAh/g, and the capacity retention rate after 500 cycles is 93.47%.
The preparation method of the silicon-based negative electrode material for the lithium battery comprises the following steps of:
s1, polycrystalline silicon powder with the particle size of 10-50um, crystalline silicon with the particle size of 100-500nm, and crystalline silicon with the particle size of 10-50nm are mixed according to the mass ratio of 1-3: 5-7: 2-5, adding 10-30% by mass of hydrochloric acid and 5-20% by mass of nitric acid according to a volume ratio of 2: 1 for 20-60min in acid solution;
adding the silver-deposited silicon material into a silver-deposited mixed solution consisting of 0.02-0.06mol/L silver nitrate solution and 5-10% hydrofluoric acid by mass percent, depositing for 20-60min, and washing with deionized water after deposition is finished to prepare the silver-deposited silicon material;
s2, adding the silicon material prepared in the step S1 into an etching solution consisting of 8-10mol/L hydrofluoric acid, 5-10% nitric acid solution and 15-20% hydrogen peroxide, etching for 40-80min at 40-60 ℃, washing with deionized water, and drying by using an infrared lamp to prepare the porous silicon material;
s3, mixing the porous silicon material prepared in the step S2, graphite, graphene, polyvinyl alcohol and an ultrapure water solution according to a mass ratio of 5-8: 1-3: 1-3: 3-1: 2-1, placing the mixture in a ball mill together, and performing ball milling for 3-5 hours at 500r/min to prepare silicon slurry coated by graphene;
s4, coating the silicon slurry coated with the graphene prepared in the step S3 on a copper foil electrode current collector, placing the copper foil electrode current collector in a vacuum furnace, and drying the copper foil electrode current collector for 2-3 hours at the temperature of 80-90 ℃ to prepare a silicon material electrode coated with the graphene;
s5, placing the silicon material electrode coated by the graphene prepared in the step S4 in a vacuum furnace, heating to 850-950 ℃ at the speed of 4-7 ℃/min, sintering at 850-950 ℃ for 40-60min, and naturally cooling to room temperature to prepare the silicon-based negative electrode material for the lithium battery.
Preferably, in step S3, the porous silicon material, the graphite, the graphene, the polyvinyl alcohol, and the ultrapure water solution are mixed in a mass ratio of 7: 2: 2: 2: 1, mixing and preparing.
Preferably, in step S5, the graphene-coated silicon material electrode is placed in a vacuum furnace, heated to 900 ℃ at a rate of 5 ℃/min, and sintered at 900 ℃ for 50 min.
(III) advantageous effects
Compared with the prior art, the invention provides a silicon-based negative electrode material for a lithium battery and a preparation method thereof, and the silicon-based negative electrode material has the following beneficial effects:
1. according to the silicon-based negative electrode material, polycrystalline silicon powder with micron-sized particle sizes and crystalline silicon with two different nano-sized particle sizes are prepared into a mixed silicon source with a hierarchical particle size structure, and the mixed silicon source and a carbon source which is formed by mixing graphite, graphene and the like in mass can be compounded into a compact cladding body with a pomegranate-shaped structure;
tests show that the lithium ion battery made of the silicon-based negative electrode material has an average specific capacity of 1214 mAh/g after 500 cycles and a capacity retention rate of 93.11-93.51% after 500 cycles, and compared with the prior art that the specific capacity of the silicon-based negative electrode material is 450 mAh/g and 950mAh/g after 500 cycles, the specific capacity and the cycle capacity retention rate of the silicon-based negative electrode material consisting of a compact cladding body with a pomegranate-type structure are 85-92%, the technical effect of remarkably increasing the tap density of the nano silicon-based/carbon negative electrode material is realized, and the technical effect of remarkably increasing the specific volume capacity of the lithium ion battery negative electrode is further obtained.
2. The preparation method of the silicon-based negative electrode material comprises the steps of preparing a mixed silicon source with a hierarchical particle size structure by using polycrystalline silicon powder with micron-sized particle sizes and crystalline silicon with two different nano-sized particle sizes, depositing silver on the mixed silicon source, corroding the mixed silicon source with the deposited silver to prepare a porous silicon material, preparing the porous silicon material, graphene and graphite into graphene-coated silicon slurry, coating the silicon slurry on a copper foil electrode current collector, and drying and sintering to prepare the silicon-based negative electrode material.
Detailed Description
The first embodiment is as follows:
s1, polycrystalline silicon powder with the particle size of 10um, crystalline silicon with the particle size of 100nm and crystalline silicon with the particle size of 10nm are mixed according to the mass ratio of 1: 5: 2, adding hydrochloric acid with the mass fraction of 10% and nitric acid with the mass fraction of 5% according to the volume ratio of 2: 1 for 20min in acid solution;
adding the silver-deposited silicon material into a silver-deposited mixed solution consisting of 0.02mol/L silver nitrate solution and 5% hydrofluoric acid by mass, depositing for 20min, and washing with deionized water after deposition is finished to prepare the silver-deposited silicon material;
s2, adding the silicon material prepared in the step S1 into an etching solution composed of 8mol/L hydrofluoric acid, 5% nitric acid solution and 15% hydrogen peroxide, etching for 40min at 40 ℃, washing with deionized water, and drying by using an infrared lamp to prepare the porous silicon material;
s3, mixing the porous silicon material prepared in the step S2, graphite, graphene, polyvinyl alcohol and an ultrapure water solution according to a mass ratio of 5: 1: 1: 3: 2, mixing and preparing in a proportioning mode, putting the mixture into a ball mill, and carrying out ball milling for 3 hours at 500r/min to prepare silicon slurry coated by graphene;
s4, coating the silicon slurry coated with the graphene prepared in the step S3 on a copper foil electrode current collector, placing the copper foil electrode current collector in a vacuum furnace, and drying the copper foil electrode current collector for 2 hours at 80 ℃ to prepare a silicon material electrode coated with the graphene;
and S5, placing the silicon material electrode coated with the graphene prepared in the step S4 in a vacuum furnace, heating to 850 ℃ at the speed of 4 ℃/min, sintering for 40min at 850 ℃, and naturally cooling to room temperature to prepare the silicon-based negative electrode material for the lithium battery.
Example two:
s1, polycrystalline silicon powder with the particle size of 30um, crystalline silicon with the particle size of 200nm and crystalline silicon with the particle size of 30nm are mixed according to a mass ratio of 2: 6: 3, adding the mixture into a reaction kettle prepared from hydrochloric acid with the mass fraction of 20% and nitric acid with the mass fraction of 15% according to the volume ratio of 2: 1 for 40min in acid solution;
adding the silver-deposited silicon material into a silver-deposited mixed solution consisting of 0.04mol/L silver nitrate solution and 8% hydrofluoric acid by mass, depositing for 40min, and washing with deionized water after deposition is finished to prepare the silver-deposited silicon material;
s2, adding the silicon material prepared in the step S1 into an etching solution composed of 9mol/L hydrofluoric acid, 8% nitric acid solution and 18% hydrogen peroxide, etching for 60min at 50 ℃, washing with deionized water, and drying by using an infrared lamp to prepare a porous silicon material;
s3, mixing the porous silicon material prepared in the step S2, graphite, graphene, polyvinyl alcohol and an ultrapure water solution according to a mass ratio of 7: 2: 2: 2: 1, mixing and preparing the raw materials in a proportioning mode, putting the raw materials into a ball mill, and ball-milling for 3-5 hours at 500r/min to prepare silicon slurry coated with graphene;
s4, coating the silicon slurry coated with the graphene prepared in the step S3 on a copper foil electrode current collector, placing the copper foil electrode current collector in a vacuum furnace, and drying the copper foil electrode current collector for 2.5 hours at 85 ℃ to prepare a silicon material electrode coated with the graphene;
s5, placing the silicon material electrode coated with the graphene prepared in the step S4 in a vacuum furnace, heating to 900 ℃ at the speed of 5 ℃/min, sintering for 50min at 900 ℃, and naturally cooling to room temperature to prepare the silicon-based negative electrode material for the lithium battery.
Example three:
s1, polycrystalline silicon powder with the particle size of 50um, crystalline silicon with the particle size of 500nm and crystalline silicon with the particle size of 50nm are mixed according to the mass ratio of 3: 7: 5, adding hydrochloric acid with the mass fraction of 30% and nitric acid with the mass fraction of 20% according to the volume ratio of 2: 1 for 60min in acid solution;
adding the silver-deposited silicon material into a silver-deposited mixed solution consisting of 0.06mol/L silver nitrate solution and 10% hydrofluoric acid by mass, depositing for 60min, and washing with deionized water after deposition is finished to prepare the silver-deposited silicon material;
s2, adding the silicon material prepared in the step S1 into an etching solution composed of 10mol/L hydrofluoric acid, 10% nitric acid solution and 15-20% hydrogen peroxide, etching for 80min at the temperature of 60 ℃, washing with deionized water, and drying by using an infrared lamp to prepare the porous silicon material;
s3, mixing the porous silicon material prepared in the step S2, graphite, graphene, polyvinyl alcohol and an ultrapure water solution according to a mass ratio of 8: 3: 3: 1: 1, mixing and preparing in a proportioning mode, putting the mixture into a ball mill, and carrying out ball milling for 5 hours at 500r/min to prepare silicon slurry coated by graphene;
s4, coating the silicon slurry coated with the graphene prepared in the step S3 on a copper foil electrode current collector, placing the copper foil electrode current collector in a vacuum furnace, and drying the copper foil electrode current collector for 3 hours at 90 ℃ to prepare a silicon material electrode coated with the graphene;
s5, placing the silicon material electrode coated with the graphene prepared in the step S4 in a vacuum furnace, heating to 950 ℃ at the speed of 7 ℃/min, sintering at 950 ℃ for 60min, and naturally cooling to room temperature to prepare the silicon-based negative electrode material for the lithium battery.
Experimental example: the lithium ion battery manufactured by the silicon-based negative electrode material prepared in the embodiment adopts an electrochemical performance tester of the lithium ion battery to test the average specific capacity and the capacity retention rate of the lithium ion battery subjected to 500 cycles, and the test results are shown in table 1.
TABLE 1
| Examples | Average specific capacity (mAh/g) after 500 cycles | Capacity retention (%) after 500 cycles |
| Example one | 1214 | 93.11 |
| Example two | 1236 | 93.47 |
| EXAMPLE III | 1231 | 93.51 |
And (4) judging the standard: in the prior art, the specific capacity of the silicon-based negative electrode material is 450-950mAh/g, and the capacity retention rate is 85-92% after 500-week cyclic charge and discharge.
The invention has the beneficial effects that: the average specific capacity of the lithium ion battery prepared from the silicon-based negative electrode material prepared in the embodiment is 1214-1236mAh/g after 500 cycles, and compared with the specific capacity of the silicon-based negative electrode material in the prior art of 450-950mAh/g, the specific capacity of the silicon-based negative electrode material is remarkably improved, so that the technical effect of remarkably improving the reversible specific capacity of the lithium ion battery is realized;
the capacity retention rate of the lithium ion battery manufactured by the silicon-based negative electrode material prepared in the embodiment after 500 cycles is 93.11-93.51%, and compared with the capacity retention rate of 85-92% of the silicon-based negative electrode material in the prior art after 500 cycles, the capacity retention rate of the silicon-based negative electrode material is obviously improved, so that the technical effect of obviously improving the cycle performance of the lithium ion battery is realized.
Typical cases are as follows: s1, polycrystalline silicon powder with the particle size of 30um, crystalline silicon with the particle size of 200nm and crystalline silicon with the particle size of 30nm are mixed according to a mass ratio of 2: 6: 3, adding the mixture into a reaction kettle prepared from hydrochloric acid with the mass fraction of 20% and nitric acid with the mass fraction of 15% according to the volume ratio of 2: 1 for 40min in acid solution;
adding the silver-deposited silicon material into a silver-deposited mixed solution consisting of 0.04mol/L silver nitrate solution and 8% hydrofluoric acid by mass, depositing for 40min, and washing with deionized water after deposition is finished to prepare the silver-deposited silicon material;
s2, adding the silicon material prepared in the step S1 into an etching solution composed of 9mol/L hydrofluoric acid, 8% nitric acid solution and 18% hydrogen peroxide, etching for 60min at 50 ℃, washing with deionized water, and drying by using an infrared lamp to prepare a porous silicon material;
s3, mixing the porous silicon material prepared in the step S2, graphite, graphene, polyvinyl alcohol and an ultrapure water solution according to a mass ratio of 7: 2: 2: 2: 1, mixing and preparing the raw materials in a proportioning mode, putting the raw materials into a ball mill, and ball-milling for 3-5 hours at 500r/min to prepare silicon slurry coated with graphene;
s4, coating the silicon slurry coated with the graphene prepared in the step S3 on a copper foil electrode current collector, placing the copper foil electrode current collector in a vacuum furnace, and drying the copper foil electrode current collector for 2.5 hours at 85 ℃ to prepare a silicon material electrode coated with the graphene;
s5, placing the graphene-coated silicon material electrode prepared in the step S4 in a vacuum furnace, heating to 900 ℃ at the speed of 5 ℃/min, sintering for 50min at 900 ℃, naturally cooling to room temperature, and preparing the silicon-based negative electrode material for the lithium battery, wherein the average specific capacity of the lithium battery prepared from the silicon-based negative electrode material after 500 cycles is 1236mAh/g, and the capacity retention rate of the lithium battery after 500 cycles is 93.47%.
Claims (1)
1. The silicon-based negative electrode material for the lithium battery comprises a silicon source material and a carbon source material, and is characterized in that the silicon source material and the carbon source material are compounded into a compact cladding body in a pomegranate type structure, the carbon source wraps the silicon source, and the silicon source is tightly distributed in gaps of the carbon source; the silicon source comprises polycrystalline silicon powder with the particle size of 10-50um, crystalline silicon with the particle size of 100-500nm and crystalline silicon with the particle size of 10-50 nm; the carbon source comprises a mixture of equal parts by mass of graphite and graphene; the specific capacity of the silicon-based negative electrode material after 500 times of circulation is 1214-1236mAh/g, and the capacity retention rate after 500 times of circulation is 93.11-93.51%;
the preparation method comprises the following steps:
s1, polycrystalline silicon powder with the particle size of 10-50um, crystalline silicon with the particle size of 100-500nm, and crystalline silicon with the particle size of 10-50nm are mixed according to the mass ratio of 1-3: 5-7: 2-5, adding 10-30% by mass of hydrochloric acid and 5-20% by mass of nitric acid according to a volume ratio of 2: 1 for 20-60min in acid solution; adding the silver-deposited silicon material into a silver-deposited mixed solution consisting of 0.02-0.06mol/L silver nitrate solution and 5-10% hydrofluoric acid by mass percent, depositing for 20-60min, and washing with deionized water after deposition is finished to prepare the silver-deposited silicon material;
s2, adding the silicon material prepared in the step S1 into an etching solution consisting of 8-10mol/L hydrofluoric acid, 5-10% nitric acid solution and 15-20% hydrogen peroxide, etching for 40-80min at 40-60 ℃, washing with deionized water, and drying by using an infrared lamp to prepare the porous silicon material;
s3, mixing the porous silicon material prepared in the step S2, graphite, graphene, polyvinyl alcohol and an ultrapure water solution according to a mass ratio of 5-8: 1-3: 1-3: 3-1: 2-1, placing the mixture in a ball mill together, and performing ball milling for 3-5 hours at 500r/min to prepare silicon slurry coated by graphene;
s4, coating the silicon slurry coated with the graphene prepared in the step S3 on a copper foil electrode current collector, placing the copper foil electrode current collector in a vacuum furnace, and drying the copper foil electrode current collector for 2-3 hours at the temperature of 80-90 ℃ to prepare a silicon material electrode coated with the graphene;
s5, placing the silicon material electrode coated by the graphene prepared in the step S4 in a vacuum furnace, heating to 850-950 ℃ at the speed of 4-7 ℃/min, sintering at 850-950 ℃ for 40-60min, and naturally cooling to room temperature to prepare the silicon-based negative electrode material for the lithium battery.
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