Process for utilizing silicon monoxide micro-powder, product and application thereof
By combining silica suboxide micropowder with carbon nanotubes, a core-shell structured silicon-carbon anode material was prepared, which solved the problems of large specific surface area and agglomeration of silica suboxide micropowder in lithium-ion batteries, and achieved battery performance with high initial efficiency, high capacity and excellent cycle stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG LICHEN NEW MATERIAL TECH CO LTD
- Filing Date
- 2023-06-30
- Publication Date
- 2026-08-04
AI Technical Summary
Silica suboxide micropowder has problems such as large specific surface area, easy formation of agglomerates, and impact on battery performance in lithium-ion battery anode materials, and is difficult to use directly.
A core-shell silicon-carbon anode material was prepared by combining silica suboxide micropowder with carbon nanotubes, forming a winding structure through mechanical ball milling and shaping, and then combining it with carbon coating and lithium salt polymer coating.
The resource utilization of silica suboxide micropowder has been realized, which has improved the battery's initial efficiency, reversible specific capacity and cycle stability. The initial coulombic efficiency reaches 85% or above, and the capacity retention rate is 85% or above after 100 cycles.
Smart Images
Figure CN116812936B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of electrode materials, and in particular to a process for utilizing silica micropowder, its products, and applications. Background Technology
[0002] With the rapid development of new energy sources, facilities using electricity as the primary power source have become a development trend, leading to the research topic of energy storage and conversion. Research has found that rechargeable batteries can provide solutions to this problem, with lithium-ion batteries being a hot research topic in recent decades. Lithium-ion batteries, with their advantages of high specific energy, high operating voltage, and excellent safe cycle performance, have been widely used in various portable electronic devices and electric vehicles, significantly changing human production and lifestyles. Currently, the negative electrode of commercially available lithium-ion batteries is mainly graphite, primarily due to its good cycle stability. However, with the deepening application of lithium-ion batteries, research has found that graphite negative electrodes not only have the limitation of a relatively low theoretical specific capacity (372 mAh / g), but also suffer from lithium plating, significantly affecting battery safety performance. Therefore, a new type of negative electrode material with high specific energy and good safety is needed to replace graphite.
[0003] Among numerous novel anode materials, silicon-based materials stand out as one of the most promising alternatives to graphite anodes due to their theoretical specific capacity of up to 4200 mAh / g and their environmental friendliness. However, this high capacity also exposes the problem of significant volume changes during lithium insertion / extraction, leading to rapid capacity decay during cycling. This negatively impacts the electrochemical performance of lithium-ion batteries, limiting their commercial application.
[0004] While silicon suboxide in silicon-based materials possesses high capacity, its unique structural composition mitigates some volume changes, but volume expansion remains significant, leading to decreased cycle performance. Furthermore, the production process of silicon-based materials requires crushing and grading to obtain particles of suitable size. This process inevitably generates a large amount of microparticles, with a median particle size (D50) of 0.05–2 μm. These microparticles are unsuitable for direct use as anode materials in lithium-ion batteries. Experiments have shown that these microparticles have a large specific surface area, resulting in an excessively large SEI film during lithium insertion / extraction. This leads to significant electrolyte consumption, an irreversible process that severely impacts battery performance. Additionally, these microparticles tend to form uncontrollable agglomerates during electrode fabrication, hindering electrode production.
[0005] Therefore, solving the problem of silicon-based material micron powder and making full use of micron powder resources has become a major issue that needs to be addressed. Summary of the Invention
[0006] To address the shortcomings of existing technologies, this invention discloses a process for utilizing silica suboxide micropowder, which not only fully utilizes micropowder resources, but also enables the assembly of silicon-carbon composite materials prepared using silica suboxide as raw material to produce batteries with high initial efficiency, high reversible specific capacity, and excellent cycle stability, thus solving a series of problems that exist when silica suboxide micropowder is directly used in batteries.
[0007] The specific technical solution is as follows:
[0008] A process for utilizing silica fume micropowder includes the following steps:
[0009] (1) A raw material dispersion was obtained by mixing silica powder, carbon nanotubes, dispersant and solvent. After stirring evenly, the mixture was mechanically ball-milled and then dried to obtain silica / carbon nanotube composite.
[0010] (2) The silicon suboxide / carbon nanotube composite prepared in step (1) is subjected to shaping treatment to obtain silicon-based material / carbon nanotube aggregates.
[0011] (3) The silicon-based material / carbon nanotube aggregates prepared in step (2) are coated with carbon to obtain silicon-carbon composite material.
[0012] The process disclosed in this invention uses silica suboxide micropowder and carbon nanotubes as raw materials. First, the carbon nanotubes are dispersed to obtain an intertwined carbon nanotube framework structure. Then, silica suboxide micropowder is added, and mechanical ball milling is used to fully embed the silica suboxide micropowder into the gaps in the carbon nanotube framework structure. This process makes full use of silica suboxide micropowder while combining the characteristics of carbon nanotubes to make up for some of the deficiencies of silica suboxide micropowder. Subsequent shaping treatment further improves the problem of the large specific surface area of silica suboxide micropowder.
[0013] In step (1):
[0014] Preferably, the D50 of the silica suboxide micropowder is 0.05–2.0 μm; more preferably, it is 0.5–1.0 μm. The silica suboxide micropowder is derived from silica suboxide micropowder collected during the crushing and dispersion steps in the preparation of silicon-carbon anode materials.
[0015] Preferably, the carbon nanotubes are selected from carboxylated carbon nanotubes and / or hydroxylated carbon nanotubes.
[0016] Further preferably, the carbon nanotubes are selected from carboxylated carbon nanotubes, and silicon suboxide itself has a certain amount of hydroxyl groups, which can be chemically bonded to carbon nanotubes with carboxyl groups.
[0017] Preferably, the dispersant is selected from one or more of polyvinylpyrrolidone, sodium carboxymethyl cellulose, polyacrylic acid, and polyvinyl alcohol.
[0018] Preferably, the solvent is selected from one or more of water, N-methylpyrrolidone, triethyl phosphate, ethanol, and isopropanol.
[0019] Experiments revealed that the mass ratio of carbon nanotubes to dispersant, the mass ratio of silica fume to carbon nanotubes, and the mechanical ball milling process in this process synergistically influence the electrochemical performance of the battery assembled from the final silicon-carbon anode material. By adjusting the mass ratio of carbon nanotubes to dispersant, the dispersion state of the carbon nanotubes can be controlled, thereby regulating the content of silica fume embedded in the gaps of the carbon nanotube framework. Furthermore, adjusting the mechanical ball milling process parameters ensures the full embedding of the silica fume.
[0020] Preferred,
[0021] The mass ratio of carbon nanotubes to dispersant is 1:0.001 to 0.01;
[0022] The mass ratio of silica fume micropowder to carbon nanotubes is 0.2–2.0:1;
[0023] The mechanical ball milling process involves a ball milling speed of 2000–3500 rpm and a ball milling time of 1–5 hours.
[0024] Further optimization:
[0025] The mass ratio of silica fume powder to carbon nanotubes is 0.26–0.5:1;
[0026] The mass ratio of carbon nanotubes to dispersant is 1:0.006–0.01;
[0027] The mechanical ball milling process involves a ball milling speed of 3000–3500 rpm and a ball milling time of 2–4 hours.
[0028] Better:
[0029] The mass ratio of silica fume powder to carbon nanotubes is 0.26:1;
[0030] The mass ratio of carbon nanotubes to dispersant is 1:0.006–0.01;
[0031] The mechanical ball milling process involves a ball milling speed of 3000 rpm and a ball milling time of 3 hours.
[0032] Experiments have shown that as the above parameters are continuously optimized, the electrochemical performance of the battery assembled with the final silicon-carbon anode material is further improved.
[0033] Preferably, the concentration of the dispersant in the raw material dispersion is 0.05-0.20%; more preferably 0.10%.
[0034] Preferably, the drying temperature in step (1) is 80 to 150°C.
[0035] In step (2):
[0036] After shaping, the silicon-based material / carbon nanotube aggregates are spherical or near-spherical with a D50 of 6–10 μm.
[0037] Preferably, the shaping process is performed in a shaping machine, with an operating frequency of 10-60Hz and an operating time of 10-120min.
[0038] In step (3):
[0039] The carbon coating process uses silicon suboxide / carbon nanotube aggregates and organic carbon sources as raw materials, including precursor preparation, precursor heat treatment and carbonization.
[0040] The organic carbon source is selected from common types in the field, such as any one or a combination of low-temperature asphalt, medium-temperature asphalt, high-temperature asphalt, and modified asphalt.
[0041] Preferably, the mass ratio of silica-suboxide / carbon nanotube aggregates to organic carbon source is 1:0.01 to 0.3, and more preferably 1:0.05 to 0.2.
[0042] The preparation of the precursor involves mixing silicon suboxide / carbon nanotube aggregates with an organic carbon source and then heating to 300-400°C and stirring until homogeneous.
[0043] The heat treatment of the precursor includes first heating to 400-550℃ and holding for 1-5 hours, then heating to 550-700℃ and holding for 1-5 hours.
[0044] The carbonization treatment is carried out at a temperature of 700–1100℃ and for a holding time of 2–10 hours.
[0045] The crude product after carbon coating treatment still needs to undergo post-processing, including processes such as dispersing, sieving, and demagnetizing.
[0046] Preferably, the utilization process of silica suboxide micro powder disclosed in this invention further includes:
[0047] (4) The silicon-carbon composite material prepared in step (3) is mixed with a polymer slurry containing lithium salt, and then dried and post-treated after being mixed evenly.
[0048] In step (4):
[0049] The lithium-containing polymer slurry is prepared by dissolving a lithium-containing polymer in water;
[0050] The concentration of the lithium salt-containing polymer slurry is 0.5% to 2.0%;
[0051] The mass ratio of the silicon-carbon anode material to the lithium-containing polymer in the lithium-containing polymer slurry is (50-100):1.
[0052] The lithium-containing polymer is prepared by solution polymerization of acrylic monomers, a first monomer, a second monomer, and a lithium salt; specifically, it includes:
[0053] Under a protective atmosphere, acrylic monomers, the first monomer, the second monomer, and the solvent are stirred and mixed at 400–600 rpm at room temperature for 20–60 min. Then, the temperature is raised to 70–90 °C and held for 20–60 min. After the system temperature stabilizes, the initiator is added, and the mixture is stirred at 70–90 °C and 400–600 rpm for 3–8 hours. Then, the temperature is raised to 90–100 °C and stirred for 1–3 hours. After that, the system is evacuated for 20–40 min, cooled to room temperature, and then an aqueous solution containing lithium salt is slowly added and stirred for 1–3 hours to obtain a lithium salt-containing polymer.
[0054] The first monomer and the second monomer are independently selected from one or two of vinyl propionate, ethyl methacrylate, acrylonitrile, hydroxyethyl methacrylate, acrylamide, and N-vinylpyrrolidone, and the first monomer and the second monomer are different.
[0055] The solvent includes, but is not limited to, one or more of water, ethanol, methanol, N,N-dimethylformamide, and N-methylpyrrolidone.
[0056] The initiator is selected from conventional types in the art, such as ammonium persulfate. The initiator accounts for 0.1% to 5.0% of the total mass of the monomer.
[0057] Based on the total mass of monomers, the mass percentage of acrylic monomers is 45-95%, the mass percentage of the first monomer is 1-40%, and the mass percentage of the second monomer is 1-30%.
[0058] The lithium salt content in the lithium-containing polymer is 15% to 30%.
[0059] Experiments have shown that coating the surface of the silicon-carbon anode material with a polymer layer containing lithium salt can further improve the electrochemical performance of the assembled battery.
[0060] The present invention also discloses silicon-carbon anode materials prepared according to the above process.
[0061] The silicon-carbon anode material prepared by this invention has a core-shell structure, with the outer shell being a carbon coating layer and the core being a carbon nanotube framework, in which silica fume microparticles are embedded.
[0062] The silicon-carbon anode material prepared by adding the above step (4) has a lithium-containing polymer layer coated on the outside of the carbon coating layer, based on the above structure.
[0063] The present invention also discloses the application of the above-mentioned silicon-carbon anode material in lithium batteries.
[0064] Compared with the prior art, the present invention has the following beneficial effects:
[0065] This invention uses silica micro powder as raw material, which not only realizes its resource utilization, but also solves the defects of silica micro powder when it is directly used as a negative electrode material for lithium-ion batteries, such as large specific surface area affecting battery performance, and easy formation of uncontrollable agglomerates during the electrode sheet manufacturing process, which is not conducive to the manufacturing of electrode sheets.
[0066] The battery assembled with the silicon-carbon anode material prepared by this invention has high initial efficiency, high capacity and excellent cycle stability. Its reversible specific capacity can reach 1500 mAh / g or above; the initial coulombic efficiency is 85% or above, and can reach up to 89%; the capacity retention rate after 100 cycles is 85% or above, and can reach up to 92%. Attached Figure Description
[0067] Figure 1 This is a SEM image of the carbon nanotube solution after dispersion treatment in Example 1;
[0068] Figure 2 The image shows a SEM image of the silica / carbon nanotube composite prepared in step (1) of Example 1.
[0069] Figure 3 The image shows the SEM image of the final product prepared in Example 2. Detailed Implementation
[0070] The present invention will be described in further detail below with reference to embodiments and comparative examples, but the implementation of the present invention is not limited thereto.
[0071] Example 1
[0072] (1) After dispersing deionized water and polyvinylpyrrolidone (PVP) at a mass ratio of 1:0.001, multi-walled carbon nanotubes with carboxyl groups are added to the dispersant solution and mechanically stirred at 1000 rpm to obtain a dispersed carbon nanotube solution. The mass ratio of carbon nanotubes to polyvinylpyrrolidone (PVP) is 1:0.006.
[0073] Figure 1 This is a scanning electron microscope (SEM) image of the carbon nanotube solution after dispersion treatment in this embodiment. In the image, the carbon nanotubes are in a dispersed and entangled state.
[0074] Silica microparticles (median particle size D50 of 1.0 μm, purchased from Yunnan Lichen New Material Technology Co., Ltd.) were added to the dispersed carbon nanotube solution to obtain a raw material dispersion. The mass ratio of silica microparticles to carbon nanotubes was 0.26:1, and the dispersant concentration in the raw material dispersion was 0.08%. The mixture was first stirred at 1000 rpm for 2 hours using a mechanical stirrer. The homogenized raw material dispersion was then placed in a high-energy mechanical ball mill, with a grinding speed of 3000 rpm and a grinding time of 3 hours to obtain a mixed liquid. The obtained mixed liquid was then vacuum dried at 100℃ to obtain a silica / carbon nanotube composite.
[0075] Figure 2 The image shows a SEM image of the silica-suboxide / carbon nanotube composite prepared in step (1) of this embodiment. It is observed that the silica-suboxide micropowder is basically embedded in the gaps formed by the entanglement of carbon nanotubes.
[0076] (2) The silicon-based material / carbon nanotube composite obtained above was placed in a shaping machine, and the operating frequency was set to 40Hz and the operating time was 1h to obtain a spherical silicon suboxide / carbon nanotube aggregate with D50 = 6.12μm.
[0077] (3) The above-mentioned silica-suboxide / carbon nanotube aggregates and high-temperature asphalt were mixed evenly at a mass ratio of 1:0.12, heated to 330℃ and stirred at 100 rpm for 3 hours to obtain a silicon-based material / carbon nanotube precursor; the precursor was then heated to 480℃ and held for 3 hours, then heated to 660℃ and held for 1.5 hours, and finally heated to 930℃ and held for 6 hours for carbon coating treatment. After that, the mixture was dispersed, sieved (sieve mesh size of 400 mesh), and demagnetized to obtain a silicon-carbon composite material. The mass of the carbon coating layer after treatment accounted for 8% of the total mass of the silicon-carbon composite material.
[0078] The D50 of the silicon-carbon composite material finally prepared in this embodiment was found to be 6.32 μm after testing.
[0079] Example 2
[0080] Steps (1) to (3) are exactly the same as in Example 1.
[0081] (4) First, dissolve 8.0g of acrylic acid, 1.5g of acrylonitrile (first monomer), and 1.0g of vinyl propionate (second monomer) in 250g of deionized water. Slowly introduce nitrogen gas and stir at 500rpm and room temperature for 40min. Then, raise the temperature to 80℃ and hold for 40min. After the system temperature stabilizes, add 0.08g of ammonium persulfate and stir at 80℃ and 500rpm for 5 hours. Continue to raise the temperature to 95℃ and stir for 1 hour. Then, evacuate the system for 40min. After cooling to room temperature, slowly add an aqueous solution containing 3.0g of lithium hydroxide and stir for 1h to obtain a lithium salt-containing polymer.
[0082] 1.6g of lithium salt-containing polymer was dissolved in 200g of water and mechanically stirred at 2000rpm for 2h to obtain lithium salt-containing polymer slurry. Then, 100g of silicon-carbon composite material prepared in step (3) was added to the prepared lithium salt-containing polymer slurry, and mechanical stirring was continued for 2h. The mixture was then dried at 100℃ for 12h. The dried sample was then broken up and passed through a 400-mesh sieve to obtain the final product.
[0083] Figure 3 The scanning electron microscope (SEM) image of the final product prepared in this embodiment shows that a complete and uniform coating layer has been formed on the surface of the final product.
[0084] The D50 of the silicon-carbon composite material finally prepared in this embodiment was found to be 6.52 μm after testing.
[0085] Example 3
[0086] The preparation process is basically the same as in Example 1, with the only difference being:
[0087] In step (1), the mass ratio of silica fume powder to carbon nanotubes is 0.5:1 (adjusting the mass of silica fume powder), and the concentration of dispersant in the raw material dispersion is 0.08%.
[0088] Example 4
[0089] The preparation process is basically the same as in Example 1, with the only difference being:
[0090] In step (1), the mass ratio of carbon nanotubes to polyvinylpyrrolidone (PVP) is 1:0.01, and the concentration of dispersant in the raw material dispersion is 0.09%.
[0091] Example 5
[0092] The preparation process is basically the same as in Example 1, with the only difference being:
[0093] The raw material dispersion was placed in a high-energy mechanical ball mill, and the grinding speed was set to 2000 rpm for 3 hours.
[0094] Example 6
[0095] The preparation process is basically the same as in Example 1, with the only difference being:
[0096] In step (1), the raw material dispersion is placed in a high-energy mechanical ball mill, and the grinding speed is set to 3000 rpm and the grinding time is 1 h.
[0097] Example 7
[0098] The preparation process is basically the same as in Example 2, with the only difference being:
[0099] In step (4), an aqueous solution containing 1.50g of lithium hydroxide is added and stirred for 1 hour to obtain a polymer containing lithium salt; then 2g of the polymer containing lithium salt is dissolved in 200g of water and mechanically stirred to obtain a polymer slurry containing lithium salt.
[0100] Example 8
[0101] The preparation process is basically the same as in Example 2, except that:
[0102] The median particle size D50 of the silica powder used in step (1) is 0.5 μm. The prepared raw material dispersion is placed in a high-energy mechanical ball mill, and the grinding speed is set to 3500 rpm and the grinding time is 3 h.
[0103] In step (4), an aqueous solution containing 2g of lithium hydroxide is added and stirred for 1 hour to obtain a polymer containing lithium salt; then, 2g of the polymer containing lithium salt is dissolved in 200g of water and mechanically stirred to obtain a polymer slurry containing lithium salt.
[0104] Comparative Example 1
[0105] The preparation process is basically the same as in Example 1, with the only difference being:
[0106] In step (1), the mass ratio of carbon nanotubes to polyvinylpyrrolidone (PVP) is 1:0.0008, and the concentration of dispersant in the raw material dispersion is 0.04%.
[0107] Comparative Example 2
[0108] The preparation process is basically the same as in Example 1, with the only difference being:
[0109] In step (1), the mass ratio of silica fume powder to carbon nanotubes is 50:1 (adjusting the mass of silica fume powder), and the concentration of dispersant in the raw material dispersion is 0.01%.
[0110] Comparative Example 3
[0111] The preparation process is basically the same as in Example 1, with the only difference being:
[0112] In step (1), the mass ratio of silica fume powder to carbon nanotubes is 0.11:1 (adjusting the mass of silica fume powder), and the concentration of dispersant in the raw material dispersion is 0.08%.
[0113] Comparative Example 4
[0114] The preparation process is basically the same as in Example 1, with the only difference being:
[0115] The raw material dispersion prepared in step (1) was not subjected to high-energy mechanical ball milling.
[0116] Comparative Example 5
[0117] The preparation process is basically the same as in Example 1, with the only difference being:
[0118] In step (1), the carbon nanotubes were not dispersed. Instead, silica micropowder (median particle size D50 of 1.0 μm, purchased from Yunnan Lichen New Material Technology Co., Ltd.) was directly mixed with carbon nanotubes at a mass ratio of 0.26:1. The mixture was first stirred at 1000 rpm for 2 hours using a mechanical mixer. The uniformly mixed material was then placed in a high-energy mechanical ball mill, with a grinding speed of 3000 rpm and a grinding time of 3 hours to obtain the silica / carbon nanotube mixture.
[0119] SEM characterization revealed that the silica powder and carbon nanotubes in the prepared silica / carbon nanotube mixture were not mixed uniformly.
[0120] The obtained silica / carbon nanotube mixture was subjected to the same operations as in steps (2) and (3) of Example 1 to obtain the final product.
[0121] Performance testing:
[0122] The products prepared in each embodiment and comparative example were used as negative electrode materials to prepare 2032 button batteries. The specific steps are as follows: Silicon-carbon composite material, conductive agent SP, dispersant CMC and binder AONE were mixed in a mass ratio of 70:15:5:10, and water was used as a solvent to prepare a negative electrode slurry; the negative electrode slurry was coated on copper foil, and a lithium sheet was used as the counter electrode and a Celgard 2400 microporous polypropylene membrane was used as the separator to prepare a button battery.
[0123] The prepared button batteries were subjected to charge-discharge cycles under the following conditions:
[0124] The charge / discharge cutoff voltage is 0.005–1.5V. The discharge rate is first 0.1C to 0.005V, then 0.02C to 0.005V to ensure full discharge. The charging rate is 0.1C to 1.5V. The reversible capacity and initial coulombic efficiency of the button cell are then tested.
[0125] The obtained coin cells were subjected to a 200-cycle test, with a charge / discharge rate of 0.1C. The capacity retention rate was calculated after the cycle test; where, the 100-cycle capacity retention rate = (100th cycle discharge capacity / 1st cycle discharge capacity) × 100%.
[0126] After the coin cell was assembled, it was subjected to electrochemical impedance spectroscopy (EIS) testing using an electrochemical workstation to characterize the internal resistance of the cell by measuring the charge transfer resistance.
[0127] After the first cycle, the lithium-ion battery was disassembled, the thickness of the negative electrode sheet under full charge was measured, and the full charge expansion rate of the electrode sheet was calculated.
[0128] Electrode expansion rate when fully charged = (electrode thickness when fully charged - electrode thickness when uncharged) / electrode thickness when uncharged × 100%.
[0129] The test results are shown in Table 1:
[0130] Table 1
[0131]
[0132]
[0133] According to the data in Table 1, Example 1 and Example 7 are the best examples before and after coating with a lithium-containing polymer layer, respectively.
[0134] Comparing the data from Examples 1 and 3 with Comparative Examples 2 and 3 in Table 1, it can be seen that the mass ratio of silicon suboxide to carbon nanotubes in this process significantly affects the electrochemical performance of the final assembled battery. When the amount of silicon suboxide is too small (Comparative Example 3), the performance is insufficient to meet the requirements of the battery anode, resulting in poor initial efficiency, reversible specific capacity, and cycle stability of the assembled battery. As the amount of silicon suboxide increases, reaching a mass ratio of 0.26 to 0.5:1 with carbon nanotubes, the silicon suboxide powder is basically located within the pores of the carbon nanotube framework, effectively suppressing the volume expansion of silicon suboxide. The assembled battery exhibits high initial efficiency, high reversible specific capacity, and excellent cycle stability. When the amount of silicon suboxide powder is too large (Comparative Example 2), silicon suboxide powder becomes the main active component in the silicon-carbon composite material, its reversible specific capacity drops to 1300 mAh / g, the initial efficiency and capacity retention rate decrease significantly, and the expansion rate reaches as high as 180%.
[0135] Comparing the data of Example 1 with Examples 2, 7 and 8 in Table 1, it can be seen that the electrochemical performance of the silicon-carbon anode material coated with the lithium-containing polymer layer is improved to a certain extent compared with that before coating.
[0136] Comparing the data of Examples 1, 4, Comparative Example 1 and Comparative Example 5 in Table 1, it can be seen that if no dispersant is added or the amount of dispersant added is too small, the carbon nanotubes cannot be fully dispersed to obtain an intertwined carbon nanotube framework structure, which will lead to a significant deterioration in the electrochemical performance of the final silicon-carbon anode material.
[0137] Comparing the data of Examples 1, 5, and 6 and Comparative Example 4 in Table 1, it can be seen that if the raw material dispersion is mechanically stirred without high-energy mechanical ball milling, the electrochemical performance of the final silicon-carbon anode material will be significantly degraded. Even if high-energy mechanical ball milling is performed, if the process parameters of the high-energy mechanical ball milling are not matched with the amount of raw materials used, the electrochemical performance of the final silicon-carbon anode material will also decrease.
[0138] The above-described embodiments are preferred embodiments, but the scope of protection of the present invention is not limited thereto. Those skilled in the art can easily understand the spirit of the present invention based on the above embodiments and make different extensions and variations, but as long as they do not depart from the spirit of the present invention, they are all within the scope of protection of the present invention.
Claims
1. A process for utilizing fine silicon monoxide powder, characterized by, Includes the following steps: (1) A raw material dispersion is obtained by mixing silica powder, carbon nanotubes, dispersant and solvent. First, the carbon nanotubes are dispersed to obtain a carbon nanotube skeleton structure that is entangled with each other. Then, silica powder is added, stirred evenly and mechanically ball-milled, and then dried to obtain silica / carbon nanotube composite. The silica suboxide micropowder has a D50 of 0.05~2.0μm; the mass ratio of silica suboxide micropowder to carbon nanotubes is 0.26~0.5:1; The mass ratio of carbon nanotubes to dispersant is 1:0.006~0.01; The mechanical ball milling process involves a ball milling speed of 3000~3500 rpm and a ball milling time of 2~4 hours. (2) The silicon suboxide / carbon nanotube composite prepared in step (1) is subjected to shaping treatment to obtain silicon-based material / carbon nanotube aggregates. (3) The silicon-based material / carbon nanotube aggregate prepared in step (2) is subjected to carbon coating treatment to obtain silicon-carbon composite material.
2. The process for using the fine silicon monoxide powder according to claim 1, characterized by, In step (1): The carbon nanotubes are selected from carboxylated carbon nanotubes and / or hydroxylated carbon nanotubes; The dispersant is selected from one or more of polyvinylpyrrolidone, sodium carboxymethyl cellulose, polyacrylic acid, and polyvinyl alcohol; The solvent is selected from one or more of water, N-methylpyrrolidone, triethyl phosphate, ethanol, and isopropanol.
3. The process for utilizing silicon monoxide fine powder according to claim 1, characterized by, In step (1): The concentration of the dispersant in the raw material dispersion is 0.05~0.20%.
4. The process for utilizing silica fume micropowder according to claim 1, characterized in that, In step (2): After shaping, the silicon-based material / carbon nanotube aggregates are spherical or near-spherical with a D50 of 6~10 μm.
5. The process for using the fine silicon monoxide powder according to claim 1, characterized by, Also includes: (4) The silicon-carbon composite material prepared in step (3) is mixed with a polymer slurry containing lithium salt, and then dried and post-treated after being mixed evenly.
6. The process for using the fine silicon monoxide powder according to claim 5, characterized by, In step (4): The lithium-containing polymer slurry is prepared by dissolving a lithium-containing polymer in water; The concentration of the lithium salt-containing polymer slurry is 0.5%~2.0%; The lithium salt content in the lithium-containing polymer is 15% to 30%; The mass ratio of the silicon-carbon composite material to the lithium-containing polymer in the lithium-containing polymer slurry is (50~100):1; The lithium-containing polymer is prepared by solution polymerization using acrylic monomers, a first monomer, a second monomer, and a lithium salt as raw materials. The first monomer and the second monomer are independently selected from one or two of vinyl propionate, ethyl methacrylate, acrylonitrile, hydroxyethyl methacrylate, acrylamide, and N-vinylpyrrolidone, and the first monomer and the second monomer are different.
7. A silicon-carbon composite material prepared by the process according to any one of claims 1 to 6.
8. The application of the silicon-carbon composite material according to claim 7 in a lithium battery.