Silicon monoxide negative electrode material, preparation method thereof and lithium ion battery

Abstract

The present disclosure relates to a silicon monoxide negative electrode material, a preparation method thereof and a lithium ion battery, the preparation method can introduce a graphene sheet structure on the surface of the silicon monoxide, and make the surface of the silicon monoxide generate a Li2Si2O5 crystal structure with charge-discharge reversibility, realize pre-lithiation treatment of the silicon monoxide, and be beneficial to improving the initial efficiency, rate performance and charge-discharge cycle stability of the negative electrode material.

Description

Technical Field

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

[0002] To improve the energy density of lithium-ion batteries, the research and development of high-capacity silicon-based anode materials has become increasingly mature. Among silicon-based anode materials, silicon-carbon anodes and silicon suboxide anodes are considered the most likely to be commercially applied. Although the expansion rate of silicon suboxide anode materials (160%) is lower than that of silicon-carbon anodes (>300%), the initial efficiency of silicon suboxide anode materials is also lower (below 60%). Compared with graphite anodes, these issues greatly limit their practical application. Summary of the Invention

[0003] The purpose of this disclosure is to provide a silicon suboxide anode material, its preparation method, and a lithium-ion battery. The preparation method can introduce graphene sheet structure on the surface of silicon suboxide and generate a Li2Si2O5 crystal structure with charge-discharge reversibility on the surface of silicon suboxide, thereby achieving pre-lithiation treatment of silicon suboxide, which is beneficial to improving the first efficiency, rate performance, and charge-discharge cycle stability of the anode material.

[0004] To achieve the above objectives, the first aspect of this disclosure provides a method for preparing a silicon suboxide anode material, the method comprising:

[0005] (1) Mix silicon suboxide and graphene oxide in a solution, and then separate the solid from the resulting mixed solution; sinter the solid to obtain the sintered product;

[0006] (2) Mix the sintered product, the lithium source and the first organic carbon source, and calcine the resulting mixture to obtain the first calcined product;

[0007] (3) Mix the first calcined product with the second organic carbon source and perform a second calcination.

[0008] Optionally, in step (1), the mixing conditions include: contacting a first dispersion containing silica powder and a second dispersion containing graphene oxide powder and stirring for 1 to 8 hours to obtain the mixed solution;

[0009] The separation method includes one or more of evaporation, filtration and centrifugation, preferably evaporation; the evaporation temperature is 80-110°C.

[0010] Optionally, the first dispersion has a solid content of 1-10%, and the D50 particle size of the silica suboxide powder is 3-12 μm; the second dispersion has a solid content of 1-10%; the first dispersion and the second dispersion are contacted at a weight ratio of silica suboxide powder to graphene oxide powder of 10:(0.5-5).

[0011] Optionally, in step (1), the sintering conditions include: drying and crushing the solid, and sintering the crushed product; the drying temperature is 80-110°C, and the time is 5-12 h; the particle size of the crushed product is less than 100 μm, preferably less than 74 μm; the sintering is carried out in an inert gas atmosphere, the inert gas including one or more of nitrogen, argon and helium, the sintering temperature is 500-1200°C, preferably 600-800°C; and the time is 6-24 h, preferably 8-12 h.

[0012] Optionally, in step (2), the sintered product, lithium source and first organic carbon source are mixed in a weight ratio of silicon suboxide powder, graphene oxide powder, lithium source and first organic carbon source of 10:(0.5~5):(0.1~2):(0.2~2);

[0013] The first calcination is carried out in an inert gas atmosphere, wherein the inert gas includes one or more of nitrogen, argon and helium; the temperature of the first calcination is 700-1200℃, the heating rate is 1-5℃ / min, and the holding time is 8-12h.

[0014] Optionally, in step (2), the lithium source includes an inorganic lithium compound, which includes one or more of lithium carbonate, lithium acetate, lithium hydroxide, lithium chloride, lithium nitrate and lithium sulfate, preferably lithium carbonate; the first organic carbon source includes one or more of citric acid, glucose and starch, preferably citric acid.

[0015] Optionally, in step (3), the first calcined product and the second organic carbon source are mixed at a weight ratio of silica powder to the second organic carbon source of 10:(0.3-2); the second organic carbon source is selected from one or more of asphalt, modified asphalt and polymer resin, preferably asphalt;

[0016] The second calcination temperature is 700–1200℃, the heating rate is 1–5℃ / min, and the holding time is 1–24h.

[0017] The second aspect of this disclosure provides a silicon suboxide anode material prepared using the preparation method described in the first aspect of this disclosure.

[0018] The third aspect of this disclosure provides a silicon suboxide anode material, the silicon suboxide anode material comprising silicon suboxide particles loaded with lithium silicate, the lithium silicate comprising a Li2Si2O5 crystalline phase, and the surface of the silicon suboxide particles further being coated with a graphene carbon layer, the thickness of the graphene carbon layer being 1-20 nm.

[0019] This disclosure provides a lithium-ion battery in a fourth aspect, the lithium-ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte; the negative electrode comprising the silicon suboxide negative electrode material described in the second and third aspects of this disclosure.

[0020] The preparation method provided in this disclosure first combines silicon suboxide and graphene oxide through hydrogen bonding, introducing a graphene sheet structure onto the surface of silicon suboxide. This improves the poor conductivity and low volume expansion rate of silicon suboxide and facilitates the formation of silicate crystal structures on the silicon suboxide surface. By physically mixing the sintered product with lithium salt and calcining it at high temperature, the silicon-oxygen functional groups on the silicon suboxide surface react with the lithium salt to generate a Li₂Si₂O₅ crystal structure with reversible charge-discharge properties, achieving pre-lithiation of silicon suboxide. This improves the first-stage efficiency, rate performance, and charge-discharge cycle stability of the anode material. Furthermore, by reacting the first calcined product with a second organic carbon source, the silicon suboxide particles are more completely coated, further enhancing conductivity. The preparation method of this disclosure is simple and easy to operate, suitable for industrial scale-up. The resulting silicon suboxide anode material exhibits high first-stage efficiency, rate performance, and charge-discharge cycle stability, and its application in lithium-ion batteries can improve the battery's electrochemical performance.

[0021] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0023] Figure 1 These are the XRD spectra of the negative electrode materials prepared in Examples 1, 5, 6 and Comparative Example 1 of this disclosure;

[0024] Figure 2 These are the XPS spectra of the negative electrode materials prepared in Examples 1-2 and Comparative Example 3 of this disclosure;

[0025] Figure 3 Discharge specific capacity diagrams of the negative electrode materials prepared in Examples 1, 4, 7 and Comparative Example 1 of this disclosure at a rate of 0.2-3C. Detailed Implementation

[0026] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0027] The first aspect of this disclosure provides a method for preparing a silicon suboxide anode material, the method comprising:

[0028] (1) Mix silicon suboxide and graphene oxide in a solution, and then separate the solid from the resulting mixed solution; sinter the solid to obtain the sintered product;

[0029] (2) Mix the sintered product, the lithium source and the first organic carbon source, and calcine the resulting mixture to obtain the first calcined product;

[0030] (3) Mix the first calcined product with the second organic carbon source and perform a second calcination.

[0031] The preparation method disclosed herein first involves combining silicon suboxide and graphene oxide through hydrogen bonding. This introduces a graphene sheet structure onto the silicon suboxide surface, which helps improve the poor conductivity and low volume expansion rate of silicon suboxide and facilitates the formation of silicate crystal structures on the silicon suboxide surface. By physically mixing the sintered product with lithium salt and calcining it at high temperature, the silicon-oxygen functional groups on the silicon suboxide surface react with the lithium salt to generate a Li₂Si₂O₅ crystal structure with reversible charge-discharge properties. This achieves pre-lithiation treatment of silicon suboxide, which is beneficial for improving the first-stage efficiency and charge-discharge cycle stability of the anode material. Furthermore, reacting the first calcined product with a second organic carbon source helps to more completely coat the silicon suboxide particles, further improving conductivity. The preparation method disclosed herein is simple and easy to operate, suitable for industrial scale-up. The resulting silicon suboxide anode material exhibits high first-stage efficiency, rate performance, and charge-discharge cycle stability, and its application in lithium-ion batteries can improve the electrochemical performance of the batteries.

[0032] In one embodiment of this disclosure, in step (1), the mixing conditions include: contacting a first dispersion containing silica powder and a second dispersion containing graphene oxide powder and stirring for 1 to 8 hours to obtain the mixed solution; the separation method includes one or more of evaporation, filtration and centrifugation, preferably evaporation; the evaporation temperature is 80 to 110°C.

[0033] In one embodiment of this disclosure, the solid content of the first dispersion is 1-10%, and the D50 particle size of the silica suboxide powder is 3-12 μm; the solid content of the second dispersion is 1-10%; the first dispersion and the second dispersion are contacted at a weight ratio of silica suboxide powder to graphene oxide powder of 10:(0.5-5). In the above embodiment, the preferred solid content facilitates the uniform dispersion of silica suboxide powder and graphene oxide powder in the solution, improving dispersion uniformity.

[0034] In one embodiment of this disclosure, step (1) includes the following sintering conditions: drying and crushing the solid, and then sintering the crushed product; the drying temperature is 80–110°C, and the time is 5–12 h; the particle size of the crushed product is less than 100 μm, preferably less than 74 μm; the sintering is carried out in an inert gas atmosphere, the inert gas including one or more of nitrogen, argon, and helium; the sintering temperature is 500–1200°C, preferably 600–800°C; and the time is 6–24 h, preferably 8–12 h. In the above embodiment, by adopting the preferred sintering conditions, the uniform growth of lithium silicate salt crystals is facilitated.

[0035] In one embodiment of this disclosure, in step (2), the sintered product, lithium source, and first organic carbon source are mixed in a weight ratio of 10:(0.5-5):(0.1-2):(0.2-2) for silicon suboxide powder, graphene oxide powder, lithium source, and first organic carbon source; the first calcination is carried out in an inert gas atmosphere, wherein the inert gas includes one or more of nitrogen, argon, and helium; the temperature of the first calcination is 700-1200℃, the heating rate is 1-5℃ / min, and the holding time is 8-12h. In the above embodiment, by using a preferred weight of inorganic lithium source and first organic carbon source, it is beneficial to coat the carbon layer on the surface of silicon suboxide; by selecting a preferred first calcination, it is beneficial to uniformly generate lithium silicate salt on the surface of silicon suboxide.

[0036] In one embodiment of this disclosure, in step (2), the lithium source includes an inorganic lithium compound, which includes one or more of lithium carbonate, lithium acetate, lithium hydroxide, lithium chloride, lithium nitrate and lithium sulfate, preferably lithium carbonate; the first organic carbon source includes one or more of citric acid, glucose and starch, preferably citric acid.

[0037] In one embodiment of this disclosure, in step (3), the first calcined product and the second organic carbon source are mixed at a weight ratio of silica powder to the second organic carbon source of 10:(0.3-2), preferably 10:(1-2); the second organic carbon source is selected from one or more of asphalt, modified asphalt, and polymer resin, preferably asphalt; the second calcination temperature is 700-1200℃, the heating rate is 1-5℃ / min, and the holding time is 1-24h. In the above embodiment, by using the preferred weight of the second organic carbon source, it is beneficial to coat the silica particles more completely, further improving conductivity; the preferred second calcination is beneficial to the formation of the coated carbon layer.

[0038] The second aspect of this disclosure provides a silicon suboxide anode material prepared using the preparation method described in the first aspect of this disclosure.

[0039] The third aspect of this disclosure provides a silicon suboxide anode material, the silicon suboxide anode material comprising silicon suboxide particles loaded with lithium silicate, the lithium silicate comprising a Li2Si2O5 crystalline phase, and the surface of the silicon suboxide particles further being coated with a graphene carbon layer, the thickness of the graphene carbon layer being 1-20 nm.

[0040] The silicon suboxide anode material disclosed herein has high initial coulombic efficiency and charge-discharge cycle stability. Compared with graphite anode materials, the initial efficiency is improved by at least 20%, and the capacity retention rate after 200 cycles is improved by at least 38%, making it suitable for high specific energy density ion batteries.

[0041] This disclosure provides a lithium-ion battery in a fourth aspect, the lithium-ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte; the negative electrode comprising the silicon suboxide negative electrode material described in the second and third aspects of this disclosure.

[0042] The present disclosure is further illustrated by the following examples, but the present disclosure is not limited thereto. Unless otherwise specified, all raw materials used in the following examples are commercially available products.

[0043] In the following embodiments, the specific test methods are as follows:

[0044] Particle size was measured using a transmission electron microscope (TEM) with a model FEI Tecnai G-20.

[0045] The test method for specific surface area is GB / T 19587-2024 Gas Adsorption BET Method for Determination of Specific Surface Area of ​​Solid Substances;

[0046] The test method for tap density is the tap density test method in GB / T 24533-2019;

[0047] The method for testing the thickness of the graphene carbon layer is GB / T 400660-2021 Atomic Force Microscopy.

[0048] The electrochemical cycling performance was tested using the Blue Electric Test System, instrument model CT3001A.

[0049] Example 1

[0050] (1) Take silica suboxide powder (D50 particle size of 6μm) and disperse it in deionized water, control the solid content to 8%, and obtain silica suboxide dispersion A; disperse graphene oxide powder in aqueous solution by ultrasonication, control the solid content to 5%, and obtain graphene oxide dispersion B; mix dispersion A and B at room temperature according to the weight ratio of silica suboxide powder to graphene oxide powder of 10:1, stir for 4h, then evaporate the solvent water at 90℃ and collect the remaining solid;

[0051] The solid was dried in a vacuum oven at 100°C for 8 hours. The dried powder was collected and crushed through a 200-mesh sieve. The powder that passed through the sieve was collected, which is the crushed product with a particle size of less than 74 μm. The crushed product was sintered at 800°C in a nitrogen inert gas atmosphere for 8 hours to obtain the sintered product.

[0052] (2) The sintered product, lithium carbonate, and citric acid were mixed in a solid phase for 30 min at a weight ratio of 10:1:1:0.5 for silica powder, graphene oxide powder, lithium carbonate, and citric acid. The resulting mixture was then subjected to a first calcination under a nitrogen atmosphere at a temperature of 750°C, a heating rate of 5°C / min, and a holding time of 12 h to obtain the first calcined product.

[0053] (3) The product after the first calcination was mixed with asphalt at a weight ratio of 10:1 between silica powder and asphalt. Then, the temperature was increased to 750°C at a heating rate of 5°C / min for the second calcination and kept at the temperature for 24 hours to obtain silica anode material.

[0054] The silicon suboxide anode material comprises silicon suboxide particles loaded with lithium silicate, wherein the lithium silicate comprises a Li₂Si₂O₅ crystalline phase, and the silicon suboxide particles have a particle size of 7 μm and a specific surface area of ​​12 m². 2 ·g -1 The tap density is 0.8 g·ml. -1 The silicon suboxide content is 74%, and the surface of the silicon suboxide particles is also coated with a graphene carbon layer with a thickness of 1-10 nm.

[0055] The XRD pattern of the silicon suboxide anode material is as follows: Figure 1 As shown, the XPS spectrum is as follows Figure 2 As shown.

[0056] Figure 1 The XRD pattern of Example 1 shows obvious Li2Si2O5 crystal phase characteristic diffraction peaks at 2θ = 23.6°, 24.2° and 24.7°, indicating that a Li2Si2O5 crystal structure with charge-discharge reversibility has been formed on the surface of silicon suboxide. This is beneficial for achieving pre-lithiation of the anode material and improving the first efficiency, rate performance and charge-discharge cycle stability of the anode material.

[0057] Figure 2 The XPS spectrum of Example 1 shows a distinct Li 1s characteristic peak at a binding energy of 54.9 eV, indicating that the surface of the negative electrode material contains lithium, which is beneficial for the formation of lithium silicate.

[0058] Example 2

[0059] The conditions are the same as in Example 1, except that in step (2), the silicon suboxide powder, graphene oxide powder, lithium carbonate and citric acid are mixed in a weight ratio of 10:1:2:0.5 to finally obtain the silicon suboxide anode material.

[0060] The XPS spectrum of the silicon suboxide anode material is as follows: Figure 2 As shown.

[0061] Example 3

[0062] The conditions are the same as in Example 1, except that in step (2), the silicon suboxide powder, graphene oxide powder, lithium carbonate and citric acid are mixed in a weight ratio of 10:1:0.5:0.5 to finally obtain the silicon suboxide anode material.

[0063] Example 4

[0064] The conditions are the same as in Example 1, except that the second calcination temperature in step (3) is 650°C, and silicon suboxide anode material is finally obtained.

[0065] Example 5

[0066] The conditions are the same as in Example 1, except that in step (1), dispersions A and B are mixed at a weight ratio of 10:2 for silica powder to graphene oxide powder, so that in step (2), the weight ratio of silica powder, graphene oxide powder, lithium carbonate, and citric acid is 10:2:1:0.5, ultimately yielding a silica anode material. The XRD pattern of this silica anode material is shown below. Figure 1 As shown.

[0067] Example 6

[0068] The conditions are the same as in Example 1, except that in step (1), dispersions A and B are mixed in a weight ratio of 10:5 for silicon suboxide and graphene oxide, so that in step (2), the silicon suboxide powder, graphene oxide powder, lithium carbonate and citric acid are mixed in a weight ratio of 10:5:1:0.5, and finally silicon suboxide anode material is obtained.

[0069] The XRD pattern of the silicon suboxide anode material is as follows: Figure 1 As shown.

[0070] Example 7

[0071] The conditions are the same as in Example 1, except that the second calcination temperature in step (3) is 950°C, and silicon suboxide anode material is finally obtained.

[0072] Example 8

[0073] The conditions are the same as in Example 1, except that the sintering temperature in step (1) is 950°C and the time is 8 hours, and the silicon suboxide anode material is finally obtained.

[0074] Example 9

[0075] The conditions are the same as in Example 1, except that in step (3), the first calcined product and the asphalt are mixed in a weight ratio of 10:0.5 between silica powder and asphalt to obtain silica anode material.

[0076] Comparative Example 1

[0077] Silica powder, lithium carbonate, and citric acid were mixed in a solid phase at a mass ratio of 10:1:0.5 for 30 min. Then, under a nitrogen atmosphere, the temperature was raised to 750℃ at a heating rate of 5℃ / min and held for 1-10 h to obtain a silica@lithium silicate composite intermediate.

[0078] The above-mentioned composite intermediate product was mixed with petroleum asphalt solid phase at a mass ratio of silicon suboxide, lithium carbonate, citric acid and asphalt of 10:1:0.5:1. Then the mixture was heated to 750℃ at a heating rate of 5℃ / min and held at that temperature for 24h to obtain silicon suboxide-carbon@lithium silicate / carbon layer anode material.

[0079] The XRD pattern of the anode material is as follows: Figure 1 As shown.

[0080] Comparative Example 2

[0081] Silicon suboxide powder and citric acid were mixed in a solid phase at a mass ratio of 10:0.5 for 30 min. Then, under a nitrogen atmosphere, the temperature was raised to 750℃ at a heating rate of 5℃ / min and held for 1-10 h to obtain silicon suboxide@carbon anode material.

[0082] Comparative Example 3

[0083] The conditions are the same as in Example 1, except that lithium carbonate is not added in step (3). The sintered product and citric acid are mixed in a solid phase according to the weight ratio of silicon suboxide powder, graphene oxide powder and citric acid of 10:1:0.5 to finally obtain silicon suboxide-carbon / graphene anode material.

[0084] The XPS spectrum of the anode material is as follows: Figure 2 As shown.

[0085] Comparative Example 4

[0086] The conditions are the same as in Example 1, except that the silicon suboxide@lithium silicate / graphene obtained in step (3) is not mixed with pitch, but is used directly as the negative electrode material.

[0087] Comparative Example 5

[0088] The conditions are the same as in Example 1, except that step (1) is not performed. In step (2), silicon suboxide powder, graphene powder, lithium carbonate and citric acid are mixed in a weight ratio of 10:1:1:0.5 to finally obtain the negative electrode material.

[0089] Comparative Example 6

[0090] Weigh 2.5g of tetraethyl orthosilicate and dissolve it in 4mL of ethanol. Stir briefly, then add 2mL of deionized water and 1mL of hydrochloric acid to obtain mixture A. Stir mixture A vigorously for 1 hour to obtain a silica sol. Adjust the pH of the sol to 6.5 with 1M ammonia water, and continue stirring for a period of time to obtain a silica gel. Measure 70mL of graphene oxide dispersion (graphene concentration 4mg / mL). -1 Then weigh out 0.6g of sucrose and add it to the mixture, stirring until completely dissolved to obtain mixture B.

[0091] Mixture B was added to the silica gel and stirred for a period of time to obtain a brown silica-oxygen-sucrose-graphene oxide gel. The brown gel was transferred to a ball mill jar and milled at 300 rpm for 3 hours. The milled brown gel was then transferred to a freeze dryer and dried for 24 hours. The freeze-dried powder was then ground in a mortar until the particles were uniform to obtain the precursor silica-oxygen-sucrose-graphene oxide powder. This powder was then placed in a crucible and placed in a tube furnace. Ar gas was introduced and the furnace was kept at 800°C for 3 hours. After cooling to room temperature, silicon suboxide-carbon / graphene was obtained.

[0092] Weigh 0.16 g of the above-mentioned silicon suboxide-carbon / graphene powder and disperse it in 20 mL of alcohol, then ultrasonically disperse it. Next, weigh 0.04 g of lithium nitrate and add it to the mixture, stirring for a period of time until the lithium nitrate is completely dissolved. Transfer the mixture to a rotary evaporator dryer, and dry it at 70 °C and 80 rpm for 2 hours. Place the resulting powder in a crucible, using a mixture of 5% hydrogen and 95% argon as the reaction gas, and set the heating rate to 10 °C / min. -1 After being held at 800℃ for 1 hour and then cooled to room temperature in the furnace, silicon suboxide-carbon@lithium silicate / graphene was finally obtained, which is the anode material.

[0093] Depend on Figure 1 It can be seen that in Comparative Example 1, since no graphene was added, the lithium silicate crystal phase formed on the surface of silicon suboxide was mainly Li2SiO3 crystal phase. However, in Examples 1, 5 and 6, since graphene was introduced on the surface of silicon suboxide, and as the graphene content increased, the structure of the lithium silicate crystal phase formed on the surface of silicon suboxide changed, gradually transforming from Li2SiO3 crystal phase to Li2Si2O5 crystal phase. At the same time, the appearance of silica with cristobalite and quartz crystal phases was also observed, indicating that the introduction of graphene is beneficial to the formation of Li2Si2O5 crystal structure on the surface of silicon suboxide.

[0094] Depend on Figure 2 It can be seen that Comparative Example 3, without the addition of lithium carbonate, produced a negative electrode material whose surface did not contain lithium. However, in Examples 1 and 2, with the same graphene content, the lithium content on the surface of the negative electrode material increased with the addition of lithium salt. This lithium content is beneficial for achieving pre-lithiation treatment of silicon suboxide, thereby improving the initial efficiency of the negative electrode material.

[0095] Test case

[0096] Electrochemical performance tests were conducted as follows: The negative electrode materials prepared in Examples 1-9 and Comparative Examples 1-6 were assembled into lithium-ion batteries. The assembly method was as follows: the negative electrode sheet was prepared by slurry preparation and coated by an automatic coating and drying machine. Super-p was used as the conductive additive in the negative electrode slurry, and the binder was a carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) composite system. The silicon suboxide negative electrode materials, Super-p, CMC and SBR prepared in each example and each comparative example were mixed at a mass ratio of 8:1:0.5:0.5 and stirred at room temperature for 12 hours. The lithium-ion coin cell used lithium sheets as the counter electrode and was assembled into CR2023 coin cell half-cells in an argon atmosphere glove box. The sealing machine pressure was 7 MPa. The assembled lithium-ion batteries were subjected to electrochemical performance testing on a Blue Electric charge-discharge testing instrument. The test conditions were: charge-discharge at 0.1C for the first week, and the charging specific capacity of the first week was taken as the reversible specific capacity of the material. The cutoff voltage was 0.01V-1.5V. The test results are shown in Table 1. The discharge specific capacity graphs of the batteries assembled in Examples 1, 4, 7, Comparative Example 1, and silicon suboxide at rates of 0.1C-3C are shown below. Figure 3 As shown:

[0097] Table 1

[0098]

[0099]

[0100] As shown in Table 1, Examples 1-9, prepared using the method provided in this disclosure, yielded silicon suboxide with a charge-discharge reversible lithium silicate crystalline phase (Li2Si2O5 crystalline phase) on its surface, enabling pre-lithiation of silicon suboxide and significantly improving the first-stage efficiency, rate performance, and charge-discharge cycle stability of the anode material. Comparative Examples 1-5, which did not employ the method provided in this disclosure, produced anode materials with lower first-stage efficiency, poorer reversible specific capacity, and poorer cycle stability. Comparative Example 6, which did not employ the method provided in this disclosure, produced anode materials with lower silicon suboxide content and fewer active materials, resulting in a lower reversible specific capacity of only 608.3 mAh / g and poorer cycle stability.

[0101] Specifically, Comparative Examples 1 and 2 did not include graphene, which prevented the formation of a graphene carbon layer on the surface of silicon suboxide. This hindered the subsequent formation of lithium silicate crystal phase on the silicon suboxide surface, resulting in low initial efficiency and poor charge-discharge cycle stability when used in batteries. Comparative Example 3 did not include lithium carbonate, resulting in a negative electrode material with no lithium on its surface. This prevented the pre-lithiation of silicon suboxide, leading to a poor initial efficiency of 59% and poor reversible specific capacity. Comparative Example 4 did not use asphalt for coating, resulting in poor conductivity of the negative electrode material, low initial efficiency, and poor charge-discharge cycle stability. In Comparative Example 5, the graphene did not form a complex with silicon suboxide, failing to improve the poor conductivity and low volume expansion rate of silicon suboxide, resulting in poor initial efficiency, reversible specific capacity, and cycle stability of the negative electrode material.

[0102] Depend on Figure 3 It can be seen that the batteries assembled in Examples 1, 4, and 7 can discharge rapidly at different rates while maintaining high capacity and efficiency, indicating that the silicon suboxide anode materials prepared in Examples 1, 4, and 7 have high rate performance. In contrast, the batteries assembled in Comparative Example 1 and with silicon suboxide have lower discharge specific capacity and poorer rate performance at different rates.

[0103] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0104] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0105] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for preparing a silicon suboxide anode material, characterized in that, The preparation method includes: (1) Mix silicon suboxide and graphene oxide in a solution, and then separate the solid from the resulting mixed solution; sinter the solid to obtain the sintered product; (2) Mix the sintered product, the lithium source and the first organic carbon source, and calcine the resulting mixture to obtain the first calcined product; (3) Mix the first calcined product with the second organic carbon source and perform a second calcination.

2. The preparation method according to claim 1, characterized in that, In step (1), the mixing conditions include: contacting a first dispersion containing silica powder and a second dispersion containing graphene oxide powder and stirring for 1 to 8 hours to obtain the mixed solution; The separation method includes one or more of evaporation, filtration and centrifugation, preferably evaporation; the evaporation temperature is 80-110°C.

3. The preparation method according to claim 2, characterized in that, The first dispersion has a solid content of 1-10%, and the D50 particle size of the silica suboxide powder is 3-12 μm; the second dispersion has a solid content of 1-10%; the first dispersion and the second dispersion are contacted at a weight ratio of silica suboxide powder to graphene oxide powder of 10:(0.5-5).

4. The preparation method according to claim 1, characterized in that, In step (1), the sintering conditions include: drying and crushing the solid, and sintering the crushed product; the drying temperature is 80-110℃, and the time is 5-12h; the particle size of the crushed product is less than 100μm, preferably less than 74μm; the sintering is carried out in an inert gas atmosphere, the inert gas including one or more of nitrogen, argon and helium, the sintering temperature is 500-1200℃, preferably 600-800℃; and the time is 6-24h, preferably 8-12h.

5. The preparation method according to claim 1, characterized in that, In step (2), the sintered product, lithium source and first organic carbon source are mixed in a weight ratio of 10:(0.5~5):(0.1~2):(0.2~2) of silicon suboxide powder, graphene oxide powder, lithium source and first organic carbon source; The first calcination is carried out in an inert gas atmosphere, wherein the inert gas includes one or more of nitrogen, argon and helium; the temperature of the first calcination is 700-1200℃, the heating rate is 1-5℃ / min, and the holding time is 8-12h.

6. The preparation method according to claim 1, characterized in that, In step (2), the lithium source includes an inorganic lithium compound, which includes one or more of lithium carbonate, lithium acetate, lithium hydroxide, lithium chloride, lithium nitrate and lithium sulfate, preferably lithium carbonate; the first organic carbon source includes one or more of citric acid, glucose and starch, preferably citric acid.

7. The preparation method according to claim 1, characterized in that, In step (3), the first calcined product and the second organic carbon source are mixed at a weight ratio of silica powder to second organic carbon source of 10:(0.3-2); the second organic carbon source is selected from one or more of asphalt, modified asphalt and polymer resin, preferably asphalt; The second calcination temperature is 700–1200℃, the heating rate is 1–5℃ / min, and the holding time is 1–24h.

8. A silicon suboxide anode material prepared by any one of claims 1 to 7.

9. A silicon suboxide anode material, characterized in that, The silicon suboxide anode material includes silicon suboxide particles loaded with lithium silicate, wherein the lithium silicate comprises a Li2Si2O5 crystalline phase, and the surface of the silicon suboxide particles is further coated with a graphene carbon layer, wherein the thickness of the graphene carbon layer is 1-20 nm.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte; the negative electrode includes the silicon suboxide negative electrode material as described in any one of claims 8 to 9.

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