CN115849381A - Three-dimensional porous silicon-carbon composite material and preparation method and application thereof - Google Patents
Three-dimensional porous silicon-carbon composite material and preparation method and application thereof Download PDFInfo
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- 239000002153 silicon-carbon composite material Substances 0.000 title claims abstract description 34
- 238000002360 preparation method Methods 0.000 title claims abstract description 21
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 61
- 238000000034 method Methods 0.000 claims abstract description 35
- 239000000047 product Substances 0.000 claims abstract description 28
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 28
- 229920002749 Bacterial cellulose Polymers 0.000 claims abstract description 25
- 239000005016 bacterial cellulose Substances 0.000 claims abstract description 24
- 238000001035 drying Methods 0.000 claims abstract description 19
- 239000012528 membrane Substances 0.000 claims abstract description 18
- 238000002791 soaking Methods 0.000 claims abstract description 12
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims abstract description 11
- 239000003513 alkali Substances 0.000 claims abstract description 11
- 238000001816 cooling Methods 0.000 claims abstract description 11
- 239000012298 atmosphere Substances 0.000 claims abstract description 7
- 239000011259 mixed solution Substances 0.000 claims abstract description 7
- 238000010438 heat treatment Methods 0.000 claims abstract description 6
- 239000002904 solvent Substances 0.000 claims abstract description 6
- 230000001590 oxidative effect Effects 0.000 claims abstract description 5
- 238000004140 cleaning Methods 0.000 claims abstract description 4
- 229910052814 silicon oxide Inorganic materials 0.000 claims abstract description 3
- 239000012265 solid product Substances 0.000 claims abstract description 3
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 50
- 239000007788 liquid Substances 0.000 claims description 28
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 28
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 claims description 22
- 239000006185 dispersion Substances 0.000 claims description 17
- 238000004108 freeze drying Methods 0.000 claims description 17
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 14
- 229910001416 lithium ion Inorganic materials 0.000 claims description 14
- 239000007773 negative electrode material Substances 0.000 claims description 14
- 239000002245 particle Substances 0.000 claims description 14
- 229910013870 LiPF 6 Inorganic materials 0.000 claims description 9
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 9
- 239000003792 electrolyte Substances 0.000 claims description 8
- 239000002002 slurry Substances 0.000 claims description 8
- 238000000498 ball milling Methods 0.000 claims description 7
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 6
- 239000011149 active material Substances 0.000 claims description 6
- 229910000288 alkali metal carbonate Inorganic materials 0.000 claims description 6
- 150000008041 alkali metal carbonates Chemical class 0.000 claims description 6
- 239000011248 coating agent Substances 0.000 claims description 6
- 238000000576 coating method Methods 0.000 claims description 6
- 229910052744 lithium Inorganic materials 0.000 claims description 6
- 238000001291 vacuum drying Methods 0.000 claims description 6
- 229910052751 metal Inorganic materials 0.000 claims description 5
- 239000002184 metal Substances 0.000 claims description 5
- 238000002156 mixing Methods 0.000 claims description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 4
- 239000011230 binding agent Substances 0.000 claims description 4
- 239000006258 conductive agent Substances 0.000 claims description 4
- 239000011889 copper foil Substances 0.000 claims description 4
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 claims description 4
- 238000005096 rolling process Methods 0.000 claims description 4
- 238000003756 stirring Methods 0.000 claims description 4
- 238000000967 suction filtration Methods 0.000 claims description 4
- 238000001914 filtration Methods 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 3
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 2
- 229910052786 argon Inorganic materials 0.000 claims description 2
- 238000005119 centrifugation Methods 0.000 claims description 2
- 239000001307 helium Substances 0.000 claims description 2
- 229910052734 helium Inorganic materials 0.000 claims description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 2
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 2
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- 229910000027 potassium carbonate Inorganic materials 0.000 claims description 2
- 238000011085 pressure filtration Methods 0.000 claims description 2
- 230000001681 protective effect Effects 0.000 claims description 2
- 238000000926 separation method Methods 0.000 claims description 2
- 238000000352 supercritical drying Methods 0.000 claims description 2
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 claims 1
- 230000008569 process Effects 0.000 abstract description 14
- 239000000463 material Substances 0.000 abstract description 11
- 238000007599 discharging Methods 0.000 abstract description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 25
- 239000008367 deionised water Substances 0.000 description 23
- 229910021641 deionized water Inorganic materials 0.000 description 23
- 238000000197 pyrolysis Methods 0.000 description 22
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 21
- 229910052710 silicon Inorganic materials 0.000 description 18
- 239000010703 silicon Substances 0.000 description 18
- 239000005543 nano-size silicon particle Substances 0.000 description 13
- 238000007710 freezing Methods 0.000 description 12
- 230000008014 freezing Effects 0.000 description 12
- 239000000126 substance Substances 0.000 description 11
- 239000007787 solid Substances 0.000 description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 8
- 238000001179 sorption measurement Methods 0.000 description 8
- 239000002131 composite material Substances 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
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- 238000005406 washing Methods 0.000 description 6
- 238000005303 weighing Methods 0.000 description 6
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 5
- 239000003575 carbonaceous material Substances 0.000 description 5
- 229910000077 silane Inorganic materials 0.000 description 5
- 239000012300 argon atmosphere Substances 0.000 description 4
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- 239000002070 nanowire Substances 0.000 description 4
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- 238000002604 ultrasonography Methods 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000009831 deintercalation Methods 0.000 description 2
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- 230000014759 maintenance of location Effects 0.000 description 2
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- 239000011863 silicon-based powder Substances 0.000 description 2
- 239000011868 silicon-carbon composite negative electrode material Substances 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 241000589220 Acetobacter Species 0.000 description 1
- 241000589158 Agrobacterium Species 0.000 description 1
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention relates to a three-dimensional porous silicon-carbon composite material and a preparation method and application thereof, wherein the preparation method of the three-dimensional porous silicon-carbon composite material comprises the following steps of (1) dispersing silica and alkali carbonate in a solvent to obtain a mixed solution containing the silica and the alkali carbonate; (2) Soaking the bacterial cellulose membrane in a mixed solution containing silicon oxide and alkali carbonate, and drying after the completion; (3) Heating the product obtained by drying in the step (2) in a non-oxidizing atmosphere, and naturally cooling to room temperature; (4) Dispersing the product obtained in the step (3) into a solvent, and separating to obtain a solid product; (5) And (4) cleaning the product obtained in the step (4) and drying to obtain the product. The method is environment-friendly and safe, and the prepared three-dimensional porous silicon-carbon composite material can effectively reduce volume expansion in the charging and discharging processes and simultaneously improve the conductivity of the material, so that the electrochemical performance of the battery is greatly improved.
Description
Technical Field
The invention belongs to the technical field of lithium ion battery materials, and particularly relates to a three-dimensional porous silicon-carbon composite material and a preparation method and application thereof.
Background
Lithium ion batteries have found wide applications in the fields of consumer electronics, power and energy storage due to their excellent properties. The current commercialized lithium ion battery negative electrode material is mainly graphite, the preparation technology of the negative electrode material is quite mature, but the capacity of the graphite negative electrode is close to the theoretical capacity (372 mAh/g), and with the great increase of the demand of the market on the energy density of the battery, the development of the lithium ion battery with higher energy density is urgently needed.
The development of a high-capacity negative electrode material is an effective way for improving the energy density of a lithium ion battery, wherein a silicon negative electrode material is one of the most promising negative electrode materials, the theoretical specific capacity of a pure silicon negative electrode can reach 4200mAh/g, but the silicon-based negative electrode material has low conductivity and faces severe volume expansion (300%) in the charging and discharging processes, and thus the development of the high-capacity negative electrode material becomes a great obstacle for hindering the industrialization of the silicon-based negative electrode. In order to relieve or overcome the adverse effects caused by low conductivity and volume expansion of the silicon-based negative electrode, the electrochemical performance of the silicon negative electrode can be improved by various modes such as nanocrystallization, carbon coating, construction of a special composite material structure and the like of silicon particles.
The current methods for preparing nano silicon comprise a high-energy ball milling method, a silane pyrolysis method and the like. Patent CN105655569A discloses a method for preparing superfine nano silicon powder, which comprises the steps of grinding crude silicon powder, mixing the primary grinding material with auxiliary materials, performing secondary ball milling, and finally drying to obtain the nano silicon powder. The nano silicon powder prepared by the method has irregular particles, low production efficiency and higher energy consumption, and the particle size distribution can not be effectively controlled. Patent CN103936009A discloses a method for producing nanoscale high-purity silicon powder by thermal decomposition of silane, wherein silane belongs to flammable and explosive gas, is not beneficial to transportation and storage, and has extremely high requirements on safety of processes and equipment.
The silicon particles are subjected to nanocrystallization, so that the volume expansion of the silicon cathode in the circulating process can be relieved to a certain extent, but the nano silicon has a strong surface effect, can cause secondary agglomeration and accelerates the capacity attenuation; moreover, the nano-silicon has a larger specific surface area, and is in more contact with electrolyte, which is not beneficial to improving the electrochemical performance of the material. Therefore, the nano-silicon is not generally used as a negative electrode alone, and is usually required to be compounded with other materials (such as carbon materials). The carbon coating is carried out on the silicon-based material, so that the volume change of the silicon negative electrode material can be relieved, a conductive network can be constructed, and the conductive performance is improved, and therefore the carbon-coated silicon composite material is greatly concerned in recent years. However, the plastic strain of the carbon material as the clad layer cannot completely buffer the volume expansion of the silicon material caused by the composite material during the lithium deintercalation process, which finally causes the crack of the clad layer, the reduction of the first coulombic efficiency of the battery and the deterioration of the long-term cycle performance. Therefore, it is required to research that the silicon particles are coated by the carbon material having good plastic deformation, wherein the three-dimensional network structure can effectively buffer the huge volume change generated during the lithium deintercalation process of silicon, and the network structure can provide a channel for the transmission of lithium ions.
Patent CN103000865A discloses a method for preparing a carbon fiber-silicon nanowire negative electrode material, which includes steps of preparation of a silicon nanowire and preparation of a carbon fiber-silicon nanowire composite material, wherein flammable and explosive silane gas is required for the preparation of the silicon nanowire, and long-time ball milling is required for the preparation of the composite material. Patent CN103337612A discloses a nanoporous silicon-carbon composite material and a preparation method thereof, wherein the nanoporous silicon-carbon composite material is prepared by corroding a multi-component alloy, the method realizes the controllable preparation of the highly active nanoporous silicon-carbon composite material by freely corroding in a strong electrolyte solution, but because the metal and the carbon-based material are difficult to be uniformly dispersed in the matrix of the composite material, the distribution of the finally formed pore structure is not uniform enough, and the conductivity of the material cannot be improved.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a preparation method of a three-dimensional porous silicon-carbon composite material, which is environment-friendly and safe in the process of preparing nano silicon, and can generate silicon nanoparticles in situ, meanwhile, bacterial cellulose is used as a carbon source, a better three-dimensional net structure can be formed in the pyrolysis process, silicon particles with small particle size are dispersed, the agglomeration of silicon in the charging and discharging process is inhibited, the electronic conductivity of the composite material can be improved, and the added alkali carbonate can enable the material to form a porous structure, so that more space is reserved for the volume expansion of silicon. The three-dimensional porous silicon-carbon composite material prepared by the method can effectively reduce the volume expansion in the charging and discharging processes and simultaneously improve the conductivity of the material, so that the electrochemical performance of the battery is greatly improved.
In order to achieve the technical effect, the technical scheme of the invention is as follows:
a preparation method of a three-dimensional porous silicon-carbon composite material comprises the following steps:
(1) Dispersing silica and alkali carbonate in a solvent to obtain a mixed solution containing the silica and the alkali carbonate;
(2) Soaking the bacterial cellulose membrane in a mixed solution containing silicon oxide and alkali carbonate, and drying after the soaking is finished;
(3) Heating the product obtained by drying in the step (2) in a non-oxidizing atmosphere, and naturally cooling to room temperature;
(4) Dispersing the product obtained in the step (3) into a solvent, and separating to obtain a solid product;
(5) And (4) cleaning the product obtained in the step (4) and drying to obtain the product.
As an example, the molar ratio of silica to alkali metal carbonate is 1.
As one example, the mixed solution of the step (1) has a total mass concentration of 1 to 30% of silica and alkali metal carbonate.
As one example, the median particle size of the silica is 1 to 10 μm.
As one example, the bacterial cellulose membrane has a thickness of 0.5 to 3mm and a soaking time of 0.5 to 3 hours.
As one example, the mass of the bacterial cellulose is 1 to 10 times the mass of the silica in the step (1).
As one example, the alkali metal carbonate is one or more of lithium carbonate, sodium carbonate or potassium carbonate, preferably sodium carbonate.
As one example, the temperature of the heat treatment in the step (3) is 600-1100 ℃ and the time is 2-10h.
Optionally, the separation method of the step (4) is one of suction filtration, centrifugation, pressure filtration or filtration.
Optionally, the drying method is vacuum drying or one of drying in a protective atmosphere, supercritical drying and freeze drying.
As one example, the dispersion method of the step (1) is any one of stirring, ultrasonic or ball milling.
Optionally, the non-oxidizing atmosphere comprises any one of nitrogen, argon or helium.
The invention provides a three-dimensional porous silicon-carbon composite material, which is obtained by the preparation method.
The invention provides a lithium ion battery, and a negative electrode material of the lithium ion battery comprises the three-dimensional porous silicon-carbon composite material.
The lithium ion battery provided by the invention takes the three-dimensional porous silicon-carbon composite material as an active material, and the active material, the binder and the conductive agent are mixed according to the mass ratio of 8:1:1, uniformly mixing to prepare slurry, then coating the slurry on a copper foil, carrying out vacuum drying at 120 ℃ for 12 hours, and then rolling to prepare a negative pole piece, wherein a metal lithium piece is taken as a counter electrode, and an electrolyte is dissolved with LiPF 6 With 5% of FEC, wherein LiPF 6 1mol/L, the volume ratio of EC to DMC is 1When the charging and discharging voltage range of the battery is 0.01-2.0V, the first efficiency obtained by testing is more than or equal to 85%, and the capacity retention rate after 100 cycles is more than or equal to 90%.
Compared with the prior art, the invention has the following advantages:
(1) The preparation method of the invention leads the disproportionation reaction of the silicon monoxide by heat treatment (2SiO =Si + SiO) 2 ) Compared with the traditional ball milling method or silane pyrolysis method, the method for preparing the nano silicon with small particle size is safer, more environment-friendly and low in cost;
(2) The bacterial cellulose adopted by the preparation method has a unique three-dimensional nano network structure, and the three-dimensional network structure can be well preserved after pyrolysis, has better plastic deformation, and can better resist the volume expansion of silicon in the charging and discharging processes;
furthermore, the bacterial cellulose membrane is used for adsorbing the silicon monoxide and the alkali carbonate and then performing pyrolysis, so that the nano silicon can be uniformly dispersed in the gaps of the three-dimensional reticular carbon material, the volume expansion of the silicon-based material in the charging and discharging process can be effectively relieved, the obtained carbon fiber network is also beneficial to improving the conductivity of the material, and the method for generating the nano silicon in situ avoids the problem of nano silicon agglomeration, thereby improving the electrochemical performance of the battery.
(3) Furthermore, the preparation method of the invention adopts inorganic sodium carbonate as pore-forming agent, and the sodium carbonate reacts with silicon dioxide (Na) generated in the disproportionation process in the pyrolysis process 2 CO 3 +SiO 2 ＝Na 2 O·SiO 2 +CO 2 ×) is prepared, and then the pore-forming agent can be removed by cleaning with water after the preparation is finished, and strong acidic substances such as hydrofluoric acid and the like are not needed.
The removal of silica further increases the porosity in the final product, providing more buffer space for the silicon component to expand.
Detailed Description
The bacterial cellulose of the present invention includes any one or a mixture of several kinds of cellulose synthesized by some microorganism of Acetobacter, agrobacterium, rhizobium or Sarcina, but is not limited to the above-mentioned bacterial cellulose, and other bacterial celluloses commonly used in the art can also be used in the present invention.
In order to test the application performance of the three-dimensional porous silicon-carbon composite material prepared by the invention in a lithium ion battery, as an example, the three-dimensional porous silicon-carbon composite material of each example is assembled into the lithium ion battery according to the following method:
mixing the three-dimensional porous silicon-carbon composite material with binders CMC, SBR and a conductive agent SP in a mass ratio of 8:1:1 to prepare slurry, then coating the slurry on a copper foil, carrying out vacuum drying at 120 ℃ for 12 hours, and rolling to prepare the negative pole piece.
Respectively taking the negative pole piece as a test electrode, a metal lithium piece as a counter electrode and an electrolyte as LiPF 6 (1 mol/L)/EC DMC (volume ratio 1.
It should be noted that the above description is not intended to unduly limit the application range of the three-dimensional porous silicon-carbon composite material of the present invention to the above-described battery structure, but merely as an illustration of the test effect.
Electrolyte LiPF 6 DMC (volume ratio 1: the electrolyte is LiPF 6 DMC, where LiPF 6 1mol/L, the volume ratio of EC to DMC is 1, EC is ethylene carbonate, DMC is dimethyl carbonate.
Example 1
1) Weighing 4.5g of silica with a median particle size of 5 mu m and 5.5g of sodium carbonate, adding the silica and the sodium carbonate into 100mL of deionized water under the assistance of ultrasound (the ultrasound frequency is 40 KHZ), and continuing to perform ultrasound for 30min to obtain a silica-sodium carbonate dispersion liquid;
2) Soaking 25g of bacterial cellulose membrane in a dispersion liquid of silicon monoxide and sodium carbonate for 1h, washing residual liquid on the surface by deionized water after adsorption is finished, freezing the bacterial cellulose membrane in a refrigerator at the temperature of-20 ℃ for 24h, and then freeze-drying the bacterial cellulose membrane in a freeze-drying oven for 12h;
3) And (3) carrying out high-temperature pyrolysis on the product in the step (2) at 800 ℃ for 6h in a nitrogen atmosphere, and naturally cooling to room temperature.
4) And (3) dispersing the pyrolysis product in the step (3) in 100mL of deionized water, then centrifuging to obtain a solid substance, pre-freezing for 24h in a refrigerator at the temperature of-20 ℃, and then carrying out freeze drying for 12h by using a freeze dryer at the temperature of-60 ℃ to obtain the three-dimensional porous silicon-carbon composite material.
Example 2
1) Weighing 5.7g of silica with a median particle size of 3 mu m and 10.3g of sodium carbonate, and then adding the silica and the sodium carbonate into 80mL of deionized water for ball milling (300 rpm/min,0.5 h) to obtain silica-sodium carbonate dispersion liquid;
2) 30g of bacterial cellulose membrane is immersed in the dispersion of silica and sodium carbonate for 1.5h, and after adsorption is completed, the residual liquid on the surface is washed by deionized water and then is freeze-dried.
3) And (3) carrying out high-temperature pyrolysis on the product obtained in the step (2) at 800 ℃ for 6h in a nitrogen atmosphere, and naturally cooling to room temperature.
4) And (4) dispersing the pyrolysis product obtained in the step (3) in 100mL of deionized water, then carrying out suction filtration to obtain a solid substance, pre-freezing the solid substance in a refrigerator at the temperature of-20 ℃ for 24 hours, and then carrying out freeze drying on the solid substance for 12 hours by using a freeze dryer at the temperature of-60 ℃ to obtain the three-dimensional porous silicon-carbon composite material.
Example 3
1) Weighing 4.8g of silica with a median particle size of 3 mu m and 8.7g of sodium carbonate, and then adding the silica and the sodium carbonate into 90mL of deionized water under the assistance of stirring for uniform dispersion to obtain a silica-sodium carbonate dispersion solution;
2) Dipping 26g of bacterial cellulose membrane in a dispersion liquid of silicon monoxide and sodium carbonate for 1h, after adsorption is finished, washing residual liquid on the surface by water, pre-freezing the residual liquid in a refrigerator at the temperature of-20 ℃ for 24h, and then freezing and drying the residual liquid for 12h by a freeze dryer at the temperature of-60 ℃;
3) Carrying out high-temperature pyrolysis on the product obtained in the step 2 at 900 ℃ for 4h in an argon atmosphere, and naturally cooling to room temperature;
4) And (3) dispersing the pyrolysis product in the step (3) in 100mL of deionized water, then centrifuging to obtain a solid substance, and drying in vacuum at 50 ℃ to obtain the three-dimensional porous silicon-carbon composite material.
Example 4
1) Weighing 10g of silica with the median particle size of 5 mu m and 15g of sodium carbonate, then mixing the silica with the sodium carbonate in 100mL of deionized water, and then carrying out ultrasonic treatment on the solution at the ultrasonic frequency of 40KHZ for 0.5h to obtain a silica-sodium carbonate dispersion liquid;
2) Soaking 50g of bacterial cellulose membrane in a dispersion liquid of silicon monoxide and sodium carbonate for 2h, washing residual liquid on the surface by deionized water after adsorption is finished, pre-freezing the residual liquid in a refrigerator at the temperature of-20 ℃ for 24h, and then freeze-drying the residual liquid in a freeze-drying machine at the temperature of-60 ℃ for 12h;
3) Carrying out high-temperature pyrolysis on the product obtained in the step 2 at 900 ℃ for 4h in a nitrogen atmosphere, and naturally cooling to room temperature;
4) And (4) dispersing the pyrolysis product obtained in the step (3) in 100mL of deionized water, centrifuging to obtain a solid substance, and drying in vacuum at 50 ℃ to obtain the three-dimensional porous silicon-carbon composite material.
Example 5
1) Weighing 5.5g of silica with a median particle size of 5 mu m and 8g of sodium carbonate, dispersing in 90mL of deionized water, and stirring the solution (300 rpm/min, 2 h) to obtain silica-sodium carbonate dispersion;
2) Soaking 29g of bacterial cellulose membrane in a dispersion liquid of silicon monoxide and sodium carbonate for 1h, washing residual liquid on the surface by deionized water after adsorption is finished, pre-freezing the residual liquid in a refrigerator at the temperature of-20 ℃ for 24h, and then freezing and drying the residual liquid for 12h by a freeze dryer at the temperature of-60 ℃;
3) Performing high-temperature pyrolysis on the product in the step 2 at 1000 ℃ for 4h in an argon atmosphere, and naturally cooling to room temperature;
4) And (4) dispersing the pyrolysis product obtained in the step (3) in 100mL of deionized water, then filtering to obtain a solid substance, and freeze-drying to obtain the three-dimensional porous silicon-carbon composite material.
Example 6
1) Weighing 9g of silica with the median particle size of 3 mu m and 11g of sodium carbonate, dispersing in 100mL of deionized water, and performing ball milling (250rpm, 0.5 h) on the solution to obtain silica-sodium carbonate dispersion liquid;
2) Soaking 48g of bacterial cellulose membrane in a dispersion liquid of silicon monoxide and sodium carbonate for 2 hours, washing residual liquid on the surface by deionized water after adsorption is finished, pre-freezing the bacterial cellulose membrane in a refrigerator at the temperature of minus 20 ℃ for 24 hours, and then freezing and drying the bacterial cellulose membrane for 12 hours by a freeze dryer at the temperature of minus 60 ℃;
3) Carrying out high-temperature pyrolysis on the product obtained in the step 2 at 900 ℃ for 4h in an argon atmosphere, and naturally cooling to room temperature;
4) And (3) dispersing the pyrolysis product in the step (3) in 100mL of deionized water, then centrifuging to obtain a solid substance, and freeze-drying to obtain the three-dimensional porous silicon-carbon composite material.
Comparative example 1
1) 5.4g of silica with a median particle size of 5 μm is dispersed in 100mL of deionized water to obtain a silica dispersion;
2) 30g of bacterial cellulose membrane is placed in the silicon monoxide dispersion liquid for dipping, after adsorption is completed, the residual liquid on the surface is washed by deionized water, and freeze drying is carried out (after pre-freezing is carried out for 24h in a refrigerator at the temperature of minus 20 ℃, and then freeze drying is carried out for 12h by a freeze dryer at the temperature of minus 60 ℃).
3) And (3) carrying out high-temperature pyrolysis on the product in the step (2) at 1000 ℃ for 3h in an argon atmosphere, and naturally cooling to room temperature.
4) And (3) dispersing the pyrolysis product in the step (3) in deionized water, then carrying out suction filtration to obtain a solid substance, and carrying out freeze drying to obtain the three-dimensional silicon-carbon composite negative electrode material.
Comparative example 2
1) 4.5g of silica with a median particle size of 3 mu m is dispersed in 90mL of deionized water to obtain silica dispersion liquid;
2) Soaking 25g of bacterial cellulose membrane in the silicon monoxide dispersion liquid, washing residual liquid on the surface by using deionized water after adsorption is finished, and freeze-drying the residual liquid (pre-freezing for 24 hours in a refrigerator at the temperature of-20 ℃ and then freeze-drying for 12 hours by using a freeze-drying machine at the temperature of-60 ℃);
3) And (3) carrying out high-temperature pyrolysis on the product obtained in the step (2) at 900 ℃ for 4h in a nitrogen atmosphere, and naturally cooling to room temperature.
4) And (3) dispersing the pyrolysis product in the step (3) in deionized water, then centrifuging to obtain a solid substance, and freeze-drying to obtain the three-dimensional silicon-carbon composite negative electrode material.
Test examples
The three-dimensional porous silicon-carbon composite material of the embodiments 1-6 and the material of the comparative examples 1-2 are respectively used as active materials, and the active materials, the binding agents CMC and SBR and the conductive agent SP are mixed according to the mass ratio of 8:1:1 to prepare slurry, then coating the slurry on a copper foil, carrying out vacuum drying at 120 ℃ for 12h, and rolling to prepare the negative pole piece.
Respectively taking the negative pole piece as a test electrode, a metal lithium piece as a counter electrode and an electrolyte as LiPF 6 (1 mol/L)/EC DMC (volume ratio 1.
The battery performance test is carried out on a Xinwei battery tester, the charging and discharging voltage range is 0.01-2.0V, and the test data is shown in Table 1.
TABLE 1
As shown in table 1, the batteries manufactured by using the negative electrode materials of examples 1 to 6 have higher specific capacity and first efficiency, the electrochemical performance of the negative electrode material is significantly improved, and the capacity retention rate after 100 cycles is more than 90% compared with the batteries manufactured by using the negative electrode materials of comparative examples 1 to 2.
Claims (10)
1. The preparation method of the three-dimensional porous silicon-carbon composite material is characterized by comprising the following steps of:
(1) Dispersing silica and alkali carbonate in a solvent to obtain a mixed solution containing the silica and the alkali carbonate;
(2) Soaking the bacterial cellulose membrane in a mixed solution containing silicon oxide and alkali carbonate, and drying after the soaking is finished;
(3) Heating the product obtained by drying in the step (2) in a non-oxidizing atmosphere, and naturally cooling to room temperature;
(4) Dispersing the product obtained in the step (3) into a solvent, and separating to obtain a solid product;
(5) And (4) cleaning the product obtained in the step (4) and drying to obtain the product.
2. The method of claim 1, wherein the molar ratio of the silica to the alkali metal carbonate is 1;
optionally, in the mixed liquid in the step (1), the total mass concentration of the silica and the alkali metal carbonate is 1-30%;
alternatively, the median particle size of the silica is from 1 to 10 μm.
3. The method for preparing the three-dimensional porous silicon-carbon composite material according to claim 1, wherein the bacterial cellulose membrane has a thickness of 0.5-3mm and a soaking time of 0.5-3h.
4. The method for preparing the three-dimensional porous silicon-carbon composite material according to claim 1, wherein the mass of the bacterial cellulose is 1-10 times that of the silicon monoxide in the step (1).
5. The method of claim 1, wherein the alkali metal carbonate is one or more of lithium carbonate, sodium carbonate or potassium carbonate, preferably sodium carbonate.
6. The method for preparing the three-dimensional porous silicon-carbon composite material according to claim 1, wherein the temperature of the heating treatment in the step (3) is 600-1100 ℃ and the time is 2-10h;
optionally, the separation method in the step (4) is one of suction filtration, centrifugation, pressure filtration or filtration;
optionally, the drying method is vacuum drying or one of drying in a protective atmosphere, supercritical drying and freeze drying.
7. The preparation method of the three-dimensional porous silicon-carbon composite material according to claim 1, wherein the dispersion method of the step (1) is any one of stirring, ultrasonic or ball milling;
optionally, the non-oxidizing atmosphere comprises any one of nitrogen, argon or helium.
8. A three-dimensional porous silicon-carbon composite material, characterized by being obtained by the production method according to any one of claims 1 to 7.
9. A lithium ion battery, wherein a negative electrode material of the lithium ion battery comprises the three-dimensional porous silicon-carbon composite material according to claim 8.
10. The lithium ion battery of claim 9, wherein the three-dimensional porous silicon-carbon composite material is used as an active material, and the active material, the binder and the conductive agent are mixed according to a mass ratio of 8:1:1, uniformly mixing to prepare slurry, then coating the slurry on a copper foil, carrying out vacuum drying at 120 ℃ for 12 hours, and then rolling to prepare a negative pole piece, wherein a metal lithium piece is taken as a counter electrode, and an electrolyte is dissolved with LiPF 6 And fluoroethylene carbonate which accounts for 5 percent of the total mass of the electrolyte is added, wherein LiPF 6 1mol/L, ethylene carbonate: the volume ratio of dimethyl carbonate is 1.
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