A method for preparing a carbon composite divalent silicon material
By combining carbothermal reduction reaction and metal oxalate catalyst, the problem of high energy consumption in the preparation of divalent silicon materials was solved, and low-temperature rapid preparation and low-cost carbon composite divalent silicon materials with good electrochemical performance were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-19
- Publication Date
- 2026-03-24
AI Technical Summary
Existing methods for preparing divalent silicon materials suffer from high energy consumption and high cost. Traditional processes involve high operating temperatures, high energy consumption, and slow reaction rates.
The carbothermic reduction reaction is employed, using a mixture of metal oxalates as a catalyst. By uniformly mixing silicon-containing biomass with metal oxalates and then calcining at high temperature under an inert atmosphere, molten metal spheres are formed, which lowers the reduction temperature of tetravalent silicon and forms carbon-composite divalent silicon materials with the participation of biomass carbon.
This method enables the rapid preparation of carbon-composite divalent silicon materials at lower temperatures, reducing energy consumption and production costs. Furthermore, the catalyst is easy to separate, simplifying the preparation process and providing conductivity to the carbon framework.
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Figure CN116947046B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrochemical materials technology, specifically to a method for preparing a carbon composite divalent silicon material. Background Technology
[0002] The rapid development of lithium-ion battery technology and products necessitates further improvements in the energy density of energy storage batteries. Silicon-based anode materials, with their theoretical capacity far exceeding that of graphite anodes, are considered highly promising lithium storage anode materials. Since 2021, many companies have begun researching silicon-based materials, particularly Si(II)-C composite materials to replace graphite anodes, and divalent silicon composite materials are playing an increasingly important role in the lithium-ion battery industry.
[0003] Currently, the battery industry is producing divalent silicon (Si). 2+ The method is based on elemental silicon (Si), discovered in the 1980s. 0 ) and silicon dioxide (Si 4+ The composting reaction of SiO2 is a common process for producing elemental silicon. However, the high thermodynamic stability of SiO2 makes it difficult for the metallurgical industry to obtain elemental silicon. Currently, the most common production process for elemental silicon is the Siemens process based on carbothermic reduction. According to thermodynamic calculations, the initial temperature of carbothermic reduction of SiO2 is around 1700℃, and the reactor temperature is usually around 2000℃ to achieve a faster reaction rate; the subsequent composting reaction requires a temperature of around 1700℃. Although elemental silicon was discovered in blast furnace slag decades ago, the thermodynamic temperature of this reaction is still as high as 1720℃, and the reaction kinetics are poor with extremely low yield. Therefore, the traditional composting reaction method combining the above two processes to prepare silicon(II) composites has problems such as high operating temperature, high energy consumption, strong Si-O covalent bonds, and relatively slow reaction process and reaction rate. Even if the aluminothermic or magnesothermic reaction can reduce the reduction temperature to around 1000℃, the electrolytic preparation of Al or Mg still requires considerable energy consumption.
[0004] Therefore, the preparation of divalent silicon materials using a simple, efficient, low-energy-consumption, and environmentally friendly process is of great practical significance for the development of high-energy-density, low-cost lithium-ion battery anode materials. Summary of the Invention
[0005] To address the problems existing in the background technology, the present invention provides a method for preparing carbon composite divalent silicon materials, thereby solving the problems of high energy consumption and high cost in the current preparation of divalent silicon materials.
[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:
[0007] A method for preparing a carbon-composite divalent silicon material includes the following steps:
[0008] After grinding silicon-containing biomass into solid powder, it is mixed evenly with a metal oxalate mixture and calcined under an inert atmosphere to carry out a carbothermic reduction reaction. The reaction product is purified to obtain the carbon composite divalent silicon material. The metal oxalate mixture consists of two metal oxalates, namely a first metal oxalate and a second metal oxalate. The first metal oxalate is selected from tin oxalate or manganese oxalate, and the second metal oxalate is selected from manganese oxalate, iron oxalate, and zinc oxalate. The first metal oxalate and the second metal oxalate are different, and the molar ratio of the first metal oxalate to the second metal oxalate is 10:1 to 3.
[0009] Furthermore, the first metal oxalate is tin oxalate, and the second metal oxalate is manganese oxalate.
[0010] Furthermore, the mass ratio of the solid powder to the metal oxalate mixture is 1:0.66 to 2.
[0011] Furthermore, the calcination temperature is 800–1200℃, and the time is 3–5 hours.
[0012] Furthermore, the specific steps for grinding silicon-containing biomass into solid powder are as follows: the silicon-containing biomass is ball-milled to obtain solid powder. The ball-milling conditions are: rotation speed 300-400 r / min, time 5-6 h.
[0013] Furthermore, the silicon-containing biomass is one of rice straw, wheat straw, or corn straw.
[0014] Furthermore, the inert atmosphere is nitrogen or argon.
[0015] Furthermore, the impurity removal process includes acid washing.
[0016] The principle of the preparation method of this invention is as follows: Solid powder made from silicon-containing biomass is ground and mixed evenly with a metal oxalate mixture, then calcined at high temperature. Carbon and silicon dioxide in the biomass are retained. At this time, the metal oxalate mixture forms molten metal spheres, which are infinitely miscible with silicon dioxide and carbon. The retained silicon dioxide and carbon dissolve into the molten metal spheres. The molten metal spheres can lower the reaction temperature for the reduction of tetravalent silicon to divalent silicon, acting as a reduction catalyst. Simultaneously, they provide a reaction site for the reduction of silicon dioxide. Since the biomass carbon can also dissolve in the molten metal spheres, it participates in the entire reaction, combining with divalent silicon to form a carbon-composite divalent silicon material. After natural cooling to room temperature, the molten metal spheres transform into solid metal powder. At this time, the solubility of divalent silicon in the metal oxalate decreases, and the carbon-composite divalent silicon material precipitates, achieving the separation of the carbon-composite divalent silicon material from the catalyst.
[0017] The beneficial effects of this invention are:
[0018] 1) In the preparation of carbon composite divalent silicon materials by carbothermal reduction reaction, the present invention uses a metal oxalate mixture as a catalyst. The molten metal spheres formed by the metal oxalate mixture during high-temperature calcination catalyze the reduction of tetravalent silicon in silicon-containing biomass to divalent silicon and provide a site for divalent silicon to recombine with carbon. The catalyst has high catalytic efficiency, which can improve reaction kinetics, accelerate the reaction rate, and control the reaction process at a lower temperature and shorter time, which greatly reduces reaction energy consumption and production cost.
[0019] 2) The metal molten alloy catalyst in the metal oxalate mixture of the present invention can be easily separated from the product and recycled, which greatly simplifies the preparation process;
[0020] 3) This metal oxalate mixture is easy to prepare and inexpensive;
[0021] 4) This invention utilizes the natural SiO2-cellulose composite structure in silicon-containing biomass materials as a precursor for SiO2 and highly active charcoal, providing a carbon framework for carbon composite divalent silicon materials. Furthermore, the simultaneous catalysis and graphitization processes occurring in the metal oxalate molten metal ball catalytic system ensure the conductivity of the carbon framework. Attached Figure Description
[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0023] Figure 1 This is a schematic diagram illustrating the preparation principle of the preparation method of the present invention;
[0024] Figure 2 XPS image of the carbon composite divalent silicon material prepared in Example 1 of this invention;
[0025] Figure 3 This is a SEM image of the carbon composite divalent silicon material prepared in Example 1 of the present invention;
[0026] Figure 4 The HAADF, EDS, and XPS images of the carbon-composite divalent silicon material prepared in Example 1 and the silicon-carbon composite material prepared in the comparative example of this invention are shown below. Figure 4 a is the HAADF diagram of the carbon composite divalent silicon material prepared in Example 1. Figure 4 b is the HAADF diagram of the silicon-carbon composite material prepared in the comparative example. Figure 4 c shows the EDS diagrams of the carbon-composite divalent silicon material prepared in Example 1 and the silicon-carbon composite material prepared in the comparative example. Figure 4d is the XPS image of the carbon composite divalent silicon material prepared in Example 1 and the silicon-carbon composite material prepared in the comparative example;
[0027] Figure 5 The image shows the TG-DSC pattern of the carbon composite divalent silicon material prepared in Example 1 of this invention.
[0028] Figure 6 The above is a rate charge-discharge curve of the carbon composite divalent silicon material prepared in Example 1 of this invention. Detailed Implementation
[0029] The principles and features of the present invention are described below with reference to the accompanying drawings and specific embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.
[0030] This invention provides an effective carbothermic reduction strategy for carbon-composite divalent silicon materials. By introducing a molten metal oxalate alloy as a catalytic reaction medium, the low-temperature synthesis of carbon-composite divalent silicon materials from silicon-containing biomass is achieved. The specific method is as follows:
[0031] A method for preparing a carbon-composite divalent silicon material includes the following steps:
[0032] After grinding silicon-containing biomass into solid powder, it is mixed evenly with a metal oxalate mixture and calcined under an inert atmosphere to carry out a carbothermic reduction reaction. The reaction product is purified to obtain the carbon composite divalent silicon material. The metal oxalate mixture consists of two metal oxalates, namely a first metal oxalate and a second metal oxalate. The first metal oxalate is selected from tin oxalate or manganese oxalate, and the second metal oxalate is selected from manganese oxalate, iron oxalate, and zinc oxalate. The first metal oxalate and the second metal oxalate are different, and the molar ratio of the first metal oxalate to the second metal oxalate is 10:1 to 3.
[0033] The metal oxalate mixture is obtained by mixing and grinding a first metal oxalate and a second metal oxalate. The solid powder is mixed with the oxalate mixture by ball milling until homogeneous.
[0034] In some preferred embodiments, the first metal oxalate is tin oxalate and the second metal oxalate is manganese oxalate; in other preferred embodiments, the first metal oxalate is tin oxalate and the second metal oxalate is ferric oxalate; in some other embodiments, the metal oxalate may also be composed of tin oxalate and zinc oxalate, or of manganese oxalate and ferric oxalate, or of manganese oxalate and zinc oxalate.
[0035] Preferably, the mass ratio of the solid powder to the metal oxalate mixture is 1:0.66 to 2.
[0036] Preferably, the calcination temperature is 800–1200℃ and the time is 3–5 hours.
[0037] Preferably, the specific steps for grinding silicon-containing biomass into solid powder are as follows: ball milling the silicon-containing biomass to obtain solid powder, with the ball milling conditions being: rotation speed 300-400 r / min, time 5-6 h.
[0038] Preferably, the silicon-containing biomass is any biomass containing silicon dioxide that has been reported previously, such as rice straw, wheat straw, or corn straw.
[0039] Preferably, the inert atmosphere is nitrogen or argon.
[0040] Preferably, the impurity removal process includes acid washing, and the acid washing solution is oxalic acid solution, acetic acid solution or hydrochloric acid solution.
[0041] After the silicon-containing biomass is ground into solid powder and mixed evenly with a metal oxalate mixture, it is calcined at high temperature. The carbon and silicon dioxide in the biomass are retained. At this time, the metal oxalate mixture forms molten metal spheres, which are infinitely miscible with silicon dioxide and carbon. The retained silicon dioxide and carbon dissolve into the molten metal spheres. The molten metal spheres can lower the reaction temperature of the reduction of tetravalent silicon to divalent silicon, acting as a reduction catalyst. At the same time, they provide a reaction site for the reduction of silicon dioxide. Since the biomass carbon can also dissolve in the molten metal spheres, it participates in the entire reaction and combines with divalent silicon to form a carbon-composite divalent silicon material. After naturally cooling to room temperature, the molten metal spheres transform into metal solid powder. At this time, the solubility of divalent silicon in the metal oxalate decreases, and the carbon-composite divalent silicon material precipitates out, realizing the separation of the carbon-composite divalent silicon material from the catalyst. Figure 1 This explains the principle of the preparation method of the present invention.
[0042] The following are specific examples.
[0043] Example 1
[0044] 1) Mix and grind 11.26g of tin oxalate and 2.336g of manganese oxalate to obtain a metal oxalate mixture;
[0045] 2) Add 20.6g of rice straw to a planetary ball mill and grind it at 300r / min for 6h to obtain solid powder. Then add the metal oxalate mixture prepared in step 1) and stir evenly to obtain mixed solid powder.
[0046] 3) The mixed solid powder was placed in a tube furnace and calcined at 1000℃ for 4 hours under an argon atmosphere to obtain a solid carbon composite divalent silicon.
[0047] 4) The divalent silicon solid was acid-washed three times in oxalic acid solution to obtain pure phase carbon composite divalent silicon material.
[0048] Comparative Example 1
[0049] The difference between this comparative example and Example 1 is that manganese oxalate is replaced with aluminum oxalate, while everything else is the same as in Example 1.
[0050] Example 2
[0051] 1) Mix and grind 12.72g of tin oxalate and 0.876g of manganese oxalate to obtain a metal oxalate mixture;
[0052] 2) Add 20.6g of rice straw to a planetary ball mill and grind it at 300r / min for 6h to obtain solid powder. Then add the metal oxalate mixture prepared in step 1) and stir evenly to obtain mixed solid powder.
[0053] 3) The mixed solid powder was placed in a tube furnace and calcined at 800°C for 4 hours under an argon atmosphere to obtain a solid carbon composite divalent silicon.
[0054] 4) The carbon composite divalent silicon solid was acid-washed three times in oxalic acid solution to obtain pure phase carbon composite divalent silicon material.
[0055] Example 3
[0056] 1) Mix and grind 38.53g of tin oxalate and 2.67g of manganese oxalate to obtain a mixture of metal oxalates;
[0057] 2) Add 20.6g of rice straw to a planetary ball mill and grind it at 300r / min for 6h to obtain solid powder. Then add the metal oxalate mixture prepared in step 1) and stir evenly to obtain solid powder.
[0058] 3) The mixed solid powder was placed in a tube furnace and calcined at 1200℃ for 4 hours under an argon atmosphere to obtain a solid carbon composite divalent silicon.
[0059] 4) The carbon composite divalent silicon solid was acid-washed three times in oxalic acid solution to obtain pure phase carbon composite divalent silicon material.
[0060] Example 4
[0061] 1) Mix and grind 34.12g of tin oxalate and 7.08g of ferric oxalate to obtain a metal oxalate mixture;
[0062] 2) Add 20.6g of rice straw to a planetary ball mill and grind it at 300r / min for 6h to obtain solid powder. Then add the metal oxalate mixture prepared in step 1) and stir evenly to obtain mixed solid powder.
[0063] 3) The mixed solid powder was placed in a tube furnace and calcined at 1000℃ for 5 hours under an argon atmosphere to obtain a solid carbon composite divalent silicon.
[0064] 4) The carbon composite divalent silicon solid was acid-washed three times in oxalic acid solution to obtain pure phase carbon composite divalent silicon material.
[0065] Example 5
[0066] 1) Mix and grind 7.26g of tin oxalate and 2.64g of ferric oxalate to obtain a metal oxalate mixture;
[0067] 2) Add 15g of rice straw to a planetary ball mill and grind it at 300r / min for 6h to obtain solid powder. Then add the metal oxalate mixture prepared in step 1) and stir evenly to obtain mixed solid powder.
[0068] 3) The mixed solid powder was placed in a tube furnace and calcined at 800°C for 5 hours under an argon atmosphere to obtain a solid carbon composite divalent silicon.
[0069] 4) The carbon composite divalent silicon solid was acid-washed three times in oxalic acid solution to obtain pure phase carbon composite divalent silicon material.
[0070] Example 6
[0071] 1) Mix and grind 14.35g of tin oxalate and 15.65g of ferric oxalate to obtain a metal oxalate mixture;
[0072] 2) Add 15g of rice straw to a planetary ball mill and grind it at 300r / min for 6h to obtain solid powder. Then add the metal oxalate mixture prepared in step 1) and stir evenly to obtain mixed solid powder.
[0073] 3) The mixed solid powder was placed in a tube furnace and calcined at 1000℃ for 5 hours under an argon atmosphere to obtain a solid carbon composite divalent silicon.
[0074] 4) The carbon composite divalent silicon solid was acid-washed three times in acetic acid solution to obtain pure phase carbon composite divalent silicon material.
[0075] The carbon-composite divalent silicon material prepared in Example 1 was characterized by X-ray spectrometry (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis, and differential scanning calorimetry (TG-DSC), and the results were as follows. Figure 2-5 The results are shown in the figure.
[0076] Figure 2 The XPS image of the carbon composite divalent silicon material prepared in Example 1 is shown below. Figure 2 It can be seen that the Mn-Sn alloy with a melting point of 767.5℃ significantly reduces the binding energy of Si2p at a reaction temperature of 900℃, and can be used as a melt reactor, which is a key factor in promoting the carbothermic reduction of SiO2.
[0077] Figure 3 The image shows a SEM image of the carbon-composite divalent silicon material prepared in Example 1. Figure 3 It can be seen that after calcination at 1000℃ for 4 hours under an argon atmosphere, molten metal spheres that can act as reactors appeared on the sample surface. These molten metal spheres can act on both Si and C components simultaneously, providing a site for the carbothermic reduction reaction of SiO2.
[0078] Figure 4 HAADF diagrams of the carbon-composite divalent silicon material prepared in Example 1 and the silicon-carbon composite material prepared in the comparative example ( Figure 4 a,b), EDS diagram ( Figure 4 c) and XPS graph ( Figure 4 d), from Figure 4 It can be seen that in the high-angle annular dark-field image of the Mn-Sn alloy reactor, the bright areas correspond to alloy microspheres, and the dark areas correspond to the carbon skeleton; X-ray energy dispersive spectroscopy analysis shows that Mn forms a segregated phase on the Sn surface, and Si and C are uniformly distributed in the alloy reactor. Figure 4 a, b); At 1000℃, Al cannot be reduced by C and cannot form an alloy with Sn. Otherwise, Sn's ability to dissolve C in the molten state is weak. Therefore, although weak characteristic X-rays of Si can be detected inside Al-Sn alloys, the strength of C is much weaker compared to Mn-Sn alloys. Figure 4 c); This phenomenon corresponds to the XPS results, where, at the same reaction temperature, tetravalent silicon in the Mn-Sn alloy system is completely reduced to divalent silicon, while the reduction degree of SiO2 in the Al-Sn alloy system is significantly lower than that in the Mn-Sn alloy system. Figure 4 d).
[0079] Figure 5 The image shown is the TG-DSC pattern of the carbon composite divalent silicon material prepared in Example 1. Figure 5 It can be seen that manganese oxalate and tin oxalate decompose below 500℃; in the DSC curve, the small peak at 142℃ corresponds to the process of oxalate losing its water of crystallization; the temperature range of the carbothermic reduction reaction of SiO2 is around 1000℃.
[0080] The carbon-composite divalent silicon material prepared in Example 1 was assembled with lithium metal sheets to form a lithium battery, and performance tests were conducted to obtain the following results: Figure 6 The results are shown in the figure.
[0081] Figure 6 This is a rate charge-discharge curve of the carbon composite divalent silicon material prepared in Example 1 of the present invention. Figure 6As can be seen, as the current density increases from 100 mA / g to 2000 mA / g, the capacities of the carbon composite divalent silicon material prepared in Example 1 are 595, 514, 417, 364 and 292 mAh / g, respectively; when the current density is restored to 100 mA / g, the capacity is restored to 619 mAh / g. Thanks to the good porous hard template provided by rice straw and the uniform small-sized carbon composite divalent silicon material produced by catalysis, there is no obvious discharge plateau at high current density compared with the charge-discharge curve at low current density, which suppresses the degradation of silicon-based anode structure caused by large volume changes during charge-discharge.
[0082] The preparation methods in Examples 2-6 all yielded carbon composite divalent silicon materials with excellent electrochemical performance.
[0083] Metal oxalate mixtures can also be formed by tin oxalate and zinc oxalate, manganese oxalate and iron oxalate, or manganese oxalate and zinc oxalate, all of which can form molten metal spheres to catalyze the reduction of tetravalent silicon to divalent silicon.
[0084] The order of the steps in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.
[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for producing a carbon composite divalent silicon material, characterized by, The method comprises the following steps: After grinding the silicon-containing biomass into a solid powder, the solid powder is mixed with a metal oxalate mixture and then subjected to a carbothermal reduction reaction under an inert atmosphere, and the reaction product is purified to obtain the carbon composite divalent silicon material; The metal oxalate mixture is composed of two metal oxalates, i.e., a first metal oxalate and a second metal oxalate, the first metal oxalate is selected from one of tin oxalate or manganese oxalate, the second metal oxalate is selected from one of manganese oxalate, iron oxalate or zinc oxalate, and the first metal oxalate is different from the second metal oxalate, and the molar ratio of the first metal oxalate to the second metal oxalate is 10:1-3.
2. The method of claim 1, wherein the carbon-complexed divalent silicon material is prepared by a method comprising: The first metal oxalate is tin oxalate, and the second metal oxalate is manganese oxalate. 3. The method of claim 1, wherein the carbon-complexed divalent silicon material is prepared by a method comprising: providing a carbon-complexed divalent silicon material; and exposing the carbon-complexed divalent silicon material to a reducing atmosphere. The mass ratio of the solid powder to the metal oxalate mixture is 1:0.66-2.
4. The method of claim 1, wherein the carbon-complexed divalent silicon material is prepared by a method comprising: providing a carbon-complexed divalent silicon material; and exposing the carbon-complexed divalent silicon material to a reducing atmosphere. The temperature of the calcination is 800-1200℃, and the time is 3-5h.
5. The method of claim 4, wherein the carbon-complexed divalent silicon material is prepared by a method comprising: providing a carbon-complexed divalent silicon material; and exposing the carbon-complexed divalent silicon material to a reducing atmosphere. The specific steps of grinding the silicon-containing biomass into a solid powder are as follows: the silicon-containing biomass is ground into a solid powder, and the grinding conditions are as follows: the rotating speed is 300-400r / min, and the time is 5-6h.
6. The method of claim 1-5, wherein, The silicon-containing biomass is one of rice straw, wheat straw or corn straw.
7. The method of claim 1-5, wherein the carbon composite divalent silicon material is prepared by the steps of: The inert atmosphere is nitrogen or argon.
8. The method for preparing carbon composite divalent silicon material according to any one of claims 1-5, characterized in that, The impurity removal process comprises acid pickling.