Silicon monoxide negative electrode material and preparation method thereof

Abstract

The application discloses a kind of silicon monoxide negative materials and preparation method thereof, preparation method includes: after mixing organic carbon source and organic solvent stirring dissolution, with silicon monoxide and metal powder are mixed, after stirring, stationary, sintering is carried out in inert gas to obtain sintered material;Sintered material, solvent, acid are mixed, stirring, after solid-liquid separation, dry;After drying material, macromolecular polymer, organic solvent and conductive agent are mixed after stirring, microwave heating in inert gas.The application makes organic carbon source fully wrap silicon monoxide under liquid phase condition, reduces the agglomeration of material, increases the uniformity of coating layer;High-temperature sintering metal powder can partially reduce SiO2, the coating of organic carbon layer can reduce the volatilization of metal vapor, increase the reduction ratio of SiO2, improve the initial efficiency of silicon monoxide material;Microwave heating forms the secondary coating layer with high integrity and good mechanical properties on the surface of material, improves the long cycle stability of material.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a silicon suboxide anode material and its preparation method. Background Technology

[0002] With the widespread application of lithium-ion batteries in power batteries and energy storage power stations, traditional graphite anode materials, due to their inherent capacity limitations, are currently unable to meet the market demand for high-energy-density lithium-ion batteries. Silicon-based anode materials, with their abundant reserves and high capacity, are considered one of the most promising next-generation lithium-ion battery anode materials. Silicon suboxide (SiO₂) x With its high theoretical specific capacity (1700 mAh / g) and more stable cycle performance than other silicon-based anode materials, SiO₂ is one of the most promising materials to replace traditional graphite anodes as lithium-ion battery anode materials. However, due to the limitations of SiO₂... x In silicon-based anode materials, the amorphous SiO2 phase (a-SiO2) undergoes an irreversible electrochemical reaction with lithium ions after the initial few cycles, generating lithium silicates (Li2SiO3, Li4SiO4) and Li2O. This leads to a poor initial coulombic efficiency, resulting in the irreversible consumption of lithium ions from the positive electrode throughout the battery, thus reducing the actual energy density of lithium-ion batteries. Furthermore, another problem with silicon-based anode materials is their poor cycle performance, making them unable to replace commercially available graphite anode materials. The volume change of silicon suboxide during cycling (≈160%) is less than that of silicon-based anode materials (≈300%), but still significantly greater than that of graphite materials (≈10%). This severe volume change is the main reason for the poor long-term cycle stability of silicon-based anode materials.

[0003] Currently, improving the initial coulombic efficiency (ICE) is mainly achieved through pre-lithiation of silicon-based anodes, including direct addition of lithium powder and electrochemical pre-lithiation, both of which can improve ICE to some extent. However, these modification methods still have many problems. In terms of improving the cycle performance of materials, carbon coating is commonly used in industry to extend the material's cycle life.

[0004] Chinese patent application CN111434609A discloses a pre-lithiated lithium-ion battery anode material and its preparation method. The method involves adding a lithium metal source to an organic solvent, heating the resulting mixture until the lithium metal source melts, and stirring to disperse the molten lithium metal source into particles, obtaining a lithium metal source particle dispersion. An anode active material is then added to the lithium metal source particle dispersion, and the reaction is stirred for a predetermined time to obtain a pre-lithiated anode active material, wherein the anode active material includes a silicon-based material. However, this method still suffers from problems such as a complex pre-lithiation process and poor cycle life. Summary of the Invention

[0005] The technical problem to be solved by this invention is how to improve the cycle performance and coulombic efficiency of silicon suboxide anode materials.

[0006] The present invention solves the above-mentioned technical problems through the following technical means:

[0007] A method for preparing a silicon suboxide anode material includes the following steps:

[0008] S1. Mix the organic carbon source with the organic solvent and stir to dissolve to obtain a mixture;

[0009] S2. Mix the mixture, silicon suboxide and metal powder, stir and let stand;

[0010] S3. The material after S2 has been left to stand is sintered in an inert gas to obtain a sintered material;

[0011] S4. Mix the sintering material, solvent, and acid, stir, separate the solid and liquid, and then dry.

[0012] S5. The dried material from S4, the polymer, the organic solvent and the conductive agent are mixed and stirred, and then microwave heated in an inert gas to obtain the silicon suboxide anode material.

[0013] Preferably, in S1, the organic carbon source is one or more of polyvinyl alcohol, polyvinyl butyral, phenolic resin, tar, and glucose; and the organic solvent is one or more of anhydrous ethanol, acetone, dichloromethane, tetrahydrofuran, and ethyl acetate.

[0014] Preferably, in S1, the mass ratio of the organic carbon source to the organic solvent is 1:8 to 1:19; and the stirring time is 1 to 2 hours.

[0015] Preferably, in S2, the median particle size of the silicon suboxide is 3-5 μm; the metal powder is one or a mixture of magnesium, aluminum, tin, iron, antimony, lithium, and zinc powders.

[0016] Preferably, in S2, the mass ratio of silicon suboxide to metal powder is 5:1 to 10:1; the mass ratio of silicon suboxide to the organic carbon source in S1 is 40-50:5-16; the stirring time is 2 to 4 hours; and the settling time is 1 to 3 hours.

[0017] Preferably, in S3, the inert gas is one or a mixture of helium, argon, and nitrogen; the sintering temperature is 600–800°C, the heating rate is 2–5°C / min, and the sintering time is 4–12 h.

[0018] Preferably, in step S4, the mass ratio of the solvent to the sintering material is 2:1 to 5:1; the mass ratio of the acid to the solvent is 1:4 to 1:10; the stirring time is 1 to 3 hours; the solvent is one or a mixture of water, acetone, anhydrous ethanol, dichloromethane, and ethyl acetate; and the acid is one or a mixture of acetic acid, sulfuric acid, hydrochloric acid, and nitric acid.

[0019] Preferably, in step S5, the polymer is at least one of polyacrylonitrile, polyacrylic acid, polyethylene glycol, and polyacrylamide; the organic solvent is at least one of dimethylformamide, dimethyl sulfoxide, sulfolane, ethyl nitrate, and anhydrous ethanol; the conductive agent is at least one of Super-P, acetylene black, carbon nanotubes, and Ketjen black; the mass ratio of the polymer to the organic solvent is 1:5 to 1:12; the mass ratio of the polymer to the conductive agent is 19:1 to 9:1; the mass ratio of the dried material to the polymer is 20-30:5; in step S5, the inert gas is one or a mixture of helium, argon, and nitrogen; the microwave heating frequency is 2450 MHz; and the microwave heating time is 3 to 5 minutes.

[0020] Preferably, in step S4, the drying time is 6 to 12 hours and the drying temperature is 60 to 100°C.

[0021] Preferably, in step S5, the stirring time is 10 to 30 minutes.

[0022] The present invention also proposes a silicon suboxide anode material, which is prepared by the aforementioned method for preparing silicon suboxide anode materials.

[0023] The present invention also proposes a lithium-ion battery, wherein the negative electrode contains the aforementioned silicon suboxide negative electrode material and graphite.

[0024] Preferably, the mass ratio of the silicon suboxide anode material to graphite is 3:7.

[0025] The advantages of this invention are:

[0026] This invention provides a method for preparing a silicon suboxide anode material, wherein the silicon suboxide anode material is coated with a double carbon layer. The method involves uniformly stirring silicon suboxide material, metal powder, and an organic carbon source in an organic solvent, then sintering the mixture under an inert atmosphere. Through secondary coating, a silicon suboxide anode material with improved electrical performance is obtained. This method allows the organic carbon source to fully encapsulate the silicon suboxide material under liquid-phase conditions, reducing material agglomeration and increasing the uniformity of the coating layer. High-temperature sintering of the metal powder partially reduces SiO2, and the organic carbon layer coating reduces metal vapor volatilization, increasing the SiO2 reduction ratio and improving the initial efficiency of the silicon suboxide material. After the reaction, microwave heating technology can form a secondary coating layer with high integrity and good mechanical properties on the material surface, forming a double carbon layer and improving the long-term cycling stability of the material. Attached Figure Description

[0027] Figure 1 Here is a SEM image of the silicon suboxide anode material prepared in Example 1 of this invention;

[0028] Figure 2 The first charge-discharge curves of the batteries prepared with the materials of Example 1 and Comparative Example 1 of this invention at a current density of 0.1C are shown.

[0029] Figure 3 The cycling performance curves of the batteries prepared with the materials of Example 1 and Comparative Example 1 of this invention are shown at 1C / 1C current densities. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0032] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0033] Example 1

[0034] A method for preparing a silicon suboxide anode material includes the following steps:

[0035] In a dry environment, 45g of acetone solvent was weighed and poured into a beaker, followed by 5g of PVB powder. The mixture was stirred with a magnetic stirrer for 1 hour. 50g of silica powder with a median particle size of 3μm and 5g of magnesium powder were added to the resulting solution, and stirring was continued for 4 hours, followed by standing for 2 hours. The settled material was transferred to a tube furnace and heated to 800℃ at a rate of 2℃ / min under an argon atmosphere. Sintering was then carried out at this temperature for 4 hours, and the sintered material was removed after cooling to room temperature. 50g of the sintered material was poured into a beaker containing 250g of deionized water and 25g of acetic acid, stirred for 1 hour, filtered for 20 minutes, and then transferred to a vacuum oven to dry at 60℃ for 12 hours. Take 20g of the dried material, put it into a beaker, add 5g of polyacrylonitrile, 45g of dimethyl sulfoxide and 0.5g of Super-P, stir for 30min, pour into an alumina crucible, transfer to an argon atmosphere microwave heating furnace and heat for 3min, then take it out. The heating frequency is 2450MHz. After grinding, the silicon suboxide anode material is obtained.

[0036] Figure 1 The SEM image of the silicon suboxide anode material prepared in Example 1 shows that the material particles are relatively uniform in size, with a particle size of approximately 5 μm. The prepared silicon suboxide anode material was slurried and coated at a mass ratio of silicon suboxide anode material:SP:PAA = 8:1:1, and CR2032 coin cells were assembled. The electrolyte used was a 1 mol / L LiPF6 solution of EC + DMC + DEC (mass ratio 1:1:1), and electrochemical performance was tested. The results are as follows: Figure 2 As shown in Table 1, at a current density of 0.1C, the battery made from the material prepared in Example 1 has an initial discharge specific capacity of 1560.3 mAh / g, a charge specific capacity of 1329.2 mAh / g, and an initial coulombic efficiency of 85.2%.

[0037] Comparative Example 1

[0038] Commercially available SiO / C material was used as the negative electrode material. A slurry was prepared and coated according to a commercial SiO / C:SP:PAA mass ratio of 8:1:1. CR2032 coin cells were assembled using this slurry. A 1 mol / L LiPF6 EC+DMC+DEC solution (mass ratio 1:1:1) was used as the electrolyte, and electrochemical performance was tested. The results are as follows: Figure 2As shown in Table 1, at a current density of 0.1C, the battery made from the material of Comparative Example 1 has an initial discharge specific capacity of 2311.1 mAh / g, a charge specific capacity of 1600.5 mAh / g, and an initial coulombic efficiency of 69.3%. A comparison between Example 1 and Comparative Example 1 reveals that the battery made from the negative electrode material of Example 1 exhibits an initial coulombic efficiency improvement of approximately 15.9%. Using NCM622 as the positive electrode, and 30 wt% of the negative electrode material of Comparative Example 1 and 70 wt% of a conventional graphite mixture, or 30 wt% of the material prepared in Example 1 and 70 wt% of a conventional graphite mixture as the negative electrode, 7Ah soft-pack batteries were assembled through processes including slurry preparation, coating, rolling, slitting, die-cutting, stacking, tab welding, top-side sealing, baking, and electrolyte injection. After capacity testing, room temperature cycling tests were conducted at a current density of 1C / 1C. The results are as follows: Figure 3 As shown, after 300 full-cell cycles, the battery made from the material in Comparative Example 1 retained 89.5% of its capacity. Figure 3 Comparing Example 1 with Comparative Example 1, it can be found that the material prepared in Example 1 improves the cycle performance of the full cell by about 5.8%. This is because the metal powder partially reduces SiO2 in the silicon suboxide material, improving the first coulombic efficiency, and the double carbon layer coating further improves the cycle life of the battery.

[0039] Example 2

[0040] A method for preparing a silicon suboxide anode material includes the following steps:

[0041] In a dry environment, 140g of ethyl acetate solvent was weighed and poured into a beaker, followed by 10g of glucose powder. The mixture was stirred with a magnetic stirrer for 1 hour. 40g of silica powder with a median particle size of 4μm and 5g of aluminum powder were added to the resulting solution, and stirring was continued for 4 hours, followed by standing for 2 hours. The settled material was transferred to a tube furnace and heated to 700℃ at a rate of 3℃ / min under an argon atmosphere. Sintering was then carried out at this temperature for 4 hours, and the sintered material was removed after cooling to room temperature. 50g of the sintered material was poured into a beaker containing 150g of anhydrous ethanol and 25g of dilute hydrochloric acid, stirred for 1 hour, filtered for 30 minutes, and then transferred to a vacuum oven to dry at 60℃ for 12 hours. Take 20g of the dried material, put it into a beaker, add 5g of polyacrylonitrile, 45g of sulfolane and 0.5g of Super-P, stir for 30min, pour into an alumina crucible, transfer to an argon atmosphere microwave heating furnace and heat for 4min, then take it out. The heating frequency is 2450MHz. After grinding, the silicon suboxide anode material is obtained.

[0042] The prepared silicon suboxide anode material was slurryed and coated at a mass ratio of silicon suboxide anode material:SP:PAA = 8:1:1, and CR2032 coin cells were assembled. The electrolyte used was a 1 mol / L LiPF6 EC+DMC+DEC solution (mass ratio 1:1:1), and electrochemical performance was tested. The results are shown in Table 1. At a current density of 0.1C, the battery made from the material prepared in Example 2 had an initial discharge specific capacity of 1500.7 mAh / g, a charge specific capacity of 1257.6 mAh / g, and an initial coulombic efficiency of 83.8%.

[0043] Example 3

[0044] A method for preparing a silicon suboxide anode material includes the following steps:

[0045] In a dry environment, 160g of tetrahydrofuran solvent was weighed and poured into a beaker, followed by 16g of PVA powder. The mixture was stirred with a magnetic stirrer for 1 hour. 50g of silica powder with a median particle size of 5μm and 5g of lithium powder were added to the resulting solution, and stirring was continued for 3 hours, followed by standing for 2 hours. The settled material was transferred to a tube furnace and heated to 600℃ at a rate of 5℃ / min under an argon atmosphere. Sintering was then carried out at this temperature for 8 hours, and the sintered material was removed after cooling to room temperature. 50g of the sintered material was poured into a beaker containing 120g of anhydrous ethanol and 30g of acetic acid, stirred for 1 hour, filtered for 30 minutes, and then transferred to a vacuum oven to dry at 60℃ for 12 hours. Take 20g of the dried material, put it into a beaker, add 5g of polyacrylonitrile, 60g of sulfolane and 0.5g of carbon nanotubes, stir for 20min, pour into an alumina crucible, transfer to an argon atmosphere microwave heating furnace and heat for 5min, then take it out. The heating frequency is 2450MHz. After grinding, the silicon suboxide anode material is obtained.

[0046] The prepared silicon suboxide anode material was slurryed and coated at a mass ratio of silicon suboxide anode material:SP:PAA = 8:1:1, and CR2032 coin cells were assembled. The electrolyte used was a 1 mol / L LiPF6 EC+DMC+DEC solution (mass ratio 1:1:1), and electrochemical performance was tested. The results are shown in Table 1. At a current density of 0.1C, the battery made from the material prepared in Example 3 had an initial discharge specific capacity of 1486.8 mAh / g, a charge specific capacity of 1344.1 mAh / g, and an initial coulombic efficiency of 90.4%.

[0047] Example 4

[0048] A method for preparing a silicon suboxide anode material includes the following steps:

[0049] In a dry environment, 120g of tetrahydrofuran solvent was weighed and poured into a beaker, followed by 15g of phenolic resin powder. The mixture was stirred with a magnetic stirrer for 2 hours. 40g of silica powder with a median particle size of 3μm and 5g of tin powder were added to the resulting solution, and stirring was continued for another 2 hours, followed by standing for 3 hours. The settled material was transferred to a tube furnace and heated to 800℃ at a rate of 4℃ / min under an argon atmosphere. Sintering was then carried out at this temperature for 8 hours, and the sintered material was removed after cooling to room temperature. 50g of the sintered material was poured into a beaker containing 150g of acetone and 30g of acetic acid, stirred for 1 hour, filtered for 30 minutes, and then transferred to a vacuum oven to dry at 60℃ for 12 hours. Take 30g of dried material, put it into a beaker, add 5g of polyacrylic acid, 45g of sulfolane and 0.5g of Ketjen black, stir for 30min, pour into an alumina crucible, transfer to an argon atmosphere microwave heating furnace and heat for 3min, then take it out. The heating frequency is 2450MHz. After grinding, the silicon suboxide anode material is obtained.

[0050] The prepared silicon suboxide anode material was slurryed and coated at a mass ratio of silicon suboxide anode material:SP:PAA = 8:1:1, and CR2032 coin cells were assembled. The electrolyte used was a 1 mol / L LiPF6 EC+DMC+DEC solution (mass ratio 1:1:1), and electrochemical performance was tested. The results are shown in Table 1. At a current density of 0.1C, the battery made from the material prepared in Example 4 had an initial discharge specific capacity of 1509.3 mAh / g, a charge specific capacity of 1269.3 mAh / g, and an initial coulombic efficiency of 84.1%.

[0051] Table 1

[0052] First discharge specific capacity / mAh / g First charge specific capacity / mAh / g First Coulomb efficiency Comparative Example 1 2311.1 1600.5 69.3％ Example 1 1560.3 1329.2 85.2％ Example 2 1500.7 1257.6 83.8％ Example 3 1486.8 1344.1 90.4％ Example 4 1509.3 1269.3 84.1％

[0053] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a silicon monoxide negative electrode material, characterized by: The method comprises the following steps: S1, mixing and stirring an organic carbon source and an organic solvent to obtain a mixed solution; S2, mixing the mixed solution, silicon monoxide and metal powder, stirring and then standing; the mass ratio of the silicon monoxide to the metal powder is 5:1-10:1; the metal powder is a mixture of one or more of magnesium, aluminum, tin, iron, antimony, lithium and zinc powder; S3, sintering the material after standing in S2 in an inert gas to obtain a sintered material; S4, mixing the sintered material, a solvent and an acid, stirring, solid-liquid separation and then drying; S5, mixing the dried material in S4, a high molecular polymer, an organic solvent and a conductive agent, stirring, and then microwave heating in an inert gas to obtain the silicon monoxide negative electrode material.

2. The method of producing a silicon monoxide negative electrode material according to claim 1, characterized by: In S1, the organic carbon source is a mixture of one or more of polyvinyl alcohol, polyvinyl butyral ester, phenolic resin, tar and glucose; the organic solvent is a mixture of one or more of anhydrous ethanol, acetone, dichloromethane, tetrahydrofuran and ethyl acetate.

3. The method for preparing the silicon suboxide anode material according to claim 1, characterized in that: In S1, the mass ratio of the organic carbon source to the organic solvent is 1:8-1:19; the stirring time is 1-2 h.

4. The method of producing a silicon monoxide negative electrode material according to claim 1, characterized by: In S2, the median particle size of the silicon monoxide is 3-5 μm.

5. The method of claim 1, wherein the silicon monoxide negative electrode material is prepared by: In S2, the mass ratio of the silicon monoxide to the metal powder is 10:1; the mass ratio of the silicon monoxide to the organic carbon source in S1 is 40-50:5-16; the stirring time is 2-4 h; and the standing time is 1-3 h.

6. The method of producing a silicon monoxide negative electrode material according to claim 1, characterized by: In S3, the inert gas is a mixture of one or more of helium, argon and nitrogen; the sintering temperature is 600-800 ℃, the temperature rising rate is 2-5 ℃ / min, and the sintering time is 4-12 h.

7. The method of producing a silicon monoxide negative electrode material according to claim 1, characterized by: In S4, the mass ratio of the solvent to the sintered material is 2:1-5:1; the mass ratio of the acid to the solvent is 1:4-1:10; the stirring time is 1-3 h; the solvent is a mixture of one or more of water, acetone, anhydrous ethanol, dichloromethane and ethyl acetate; and the acid is a mixture of one or more of acetic acid, sulfuric acid, hydrochloric acid and nitric acid.

8. The method of claim 1, wherein the silicon monoxide negative electrode material is prepared by: In S5, the high molecular polymer is at least one of polyacrylonitrile, polyacrylic acid, polyethylene glycol and polyacrylamide; the organic solvent is at least one of dimethylformamide, dimethyl sulfoxide, sulfolane, ethylene nitrate and anhydrous ethanol; the conductive agent is at least one of Super-P, acetylene black, carbon nanotube and Ketjen black; the mass ratio of the high molecular polymer to the organic solvent is 1:5-1:12; the mass ratio of the high molecular polymer to the conductive agent is 19:1-9:1; the mass ratio of the dried material to the high molecular polymer is 20-30:5; the inert gas is a mixture of one or more of helium, argon and nitrogen; the microwave heating frequency is 2450 MHz; and the microwave heating time is 3-5 min.

9. A silicon monoxide negative electrode material, characterized by: The silicon monoxide negative electrode material is prepared by the method as claimed in any one of claims 1-8.

10. A lithium-ion battery, characterized by: The negative electrode contains the silicon monoxide negative electrode material and graphite.

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