Silicon-oxygen composite material, negative electrode sheet, lithium ion battery and preparation method thereof

Abstract

The application discloses a silicon-oxygen composite material, a negative pole piece, a lithium ion battery and a preparation method thereof. The preparation method of the silicon-oxygen composite material comprises the following steps: a porous silicon-oxygen material is coated with carbon to obtain the silicon-oxygen composite material; the porosity of the porous silicon-oxygen material is 5-30%; lithium ions are distributed in the porous silicon-oxygen material; and the temperature of the carbon coating is 500-750 DEG C. The silicon-oxygen composite material is a prelithiated silicon-oxygen composite material with a porous structure, the prelithiated silicon-oxygen composite material with a porous structure serves as a core, and a carbon layer serves as an outer shell and is coated on the surface of the core. The silicon-oxygen composite material has a high specific capacity, effectively inhibits volume expansion, guarantees the integrity of the pole piece and has excellent cycle stability.

Description

Technical Field

[0001] This invention relates to a silicon-oxygen composite material, a negative electrode sheet, a lithium-ion battery, and a method for preparing the same. Background Technology

[0002] With the development of electric vehicles, portable power tools, and home appliances, the demand for lithium-ion batteries with high energy density, high initial coulombic efficiency, and high cycle performance is increasing. The theoretical specific capacity of graphite, a traditional lithium-ion battery anode material, is only 372 mAh / g, which is insufficient to meet current demands for high energy density anodes. Silicon-based anode materials, with their higher theoretical lithium intercalation capacity (approximately 4200 mAh / g) and lower lithium intercalation plateau, have attracted widespread attention.

[0003] However, the main problem with silicon-based anode materials is their poor conductivity and the huge volume change (approximately 300%) that occurs during lithium intercalation, resulting in poor cycle performance. While silicon suboxide (SiO) contains only 50% silicon, thus reducing volume expansion somewhat, it still reaches 150%, posing a significant challenge to lithium batteries in terms of both practicality and safety.

[0004] Furthermore, silicon suboxide consumes a certain amount of active lithium during the initial lithium insertion. This active lithium, originating from the cathode, cannot participate in further electrochemical reactions, resulting in a low initial coulombic efficiency and severely limiting the energy density of lithium batteries. Pre-lithiation technology can insert lithium into silicon suboxide material in advance, forming lithium silicate (such as Li2Si2O3 and Li2SiO3), avoiding the consumption of active lithium at the cathode and effectively improving the initial coulombic efficiency of silicon suboxide.

[0005] While pre-lithiation technology can effectively improve the initial coulombic efficiency of silicon suboxide, the large-scale application of pre-lithiated silicon oxide materials is still limited by the high volume expansion of up to 150%. The volume expansion problem still needs to be addressed in pre-lithiated silicon oxide materials to reduce particle breakage and pulverization during cycling and improve the material's cycle life.

[0006] Therefore, developing a silicon-oxygen composite material with high initial coulombic efficiency, high specific capacity, low expansion, and easy mass production is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to overcome the volume expansion defect of silicon-oxygen composite materials during charge and discharge processes in existing technologies, and to provide a silicon-oxygen composite material, a negative electrode sheet, a lithium-ion battery, and a method for preparing the same. The silicon-oxygen composite material of this invention is a porous pre-lithiated silicon-oxygen composite material. The porous pre-lithiated silicon-oxygen material serves as the core, and a carbon layer forms the outer shell covering its surface. While possessing high specific capacity, it effectively suppresses volume expansion, ensuring the integrity of the electrode sheet and exhibiting excellent cycle stability.

[0008] The present invention mainly solves the above-mentioned technical problems through the following technical solutions.

[0009] This invention provides a method for preparing a silicon-oxygen composite material, which includes the following steps: a porous silicon-oxygen material is obtained by carbon coating;

[0010] The porosity of the porous silica material is 5-30%;

[0011] Lithium ions are distributed within the porous silica material;

[0012] The carbon coating temperature is 500–750°C.

[0013] In this invention, the porous silica material can be conventional in the art, as long as it can achieve the porosity within the specified range. The porosity can be understood in the conventional sense, generally referring to the percentage of the volume of pores in the porous silica material to the total volume of the porous silica material without pores.

[0014] In this invention, the porosity of the porous silica material is preferably 10-21%, for example 11%, 12%, 13%, 14%, 14.8%, 14.9%, 15%, 15.2%, 15.1%, 16%, 17%, 18%, 19%, or 20.1%.

[0015] In this invention, the pores in the porous silicon-oxygen material are preferably uniformly distributed within the silicon-oxygen material.

[0016] In this invention, SiO is distributed in the porous silicon-oxygen material. x x is 0 to 1 and not 0; preferably, the silicon oxide material in the porous silicon oxide material is SiO. x x is 0 to 1 and is not 0.

[0017] In this invention, the method for preparing the porous silicon oxide material preferably includes the following steps: the silicon oxide material is subjected to metal deposition and chemical etching in sequence.

[0018] Preferably, the metal deposition refers to immersing the silicon-oxygen raw material in a mixture of metal nitrate and hydrofluoric acid. The silicon-oxygen raw material includes SiO₂. xx is 0 to 1 and not 0, preferably SiO x x is 0 to 1 and is not 0.

[0019] In the metal deposition, the volume ratio of the metal nitrate to the hydrofluoric acid is, for example, 1:1.

[0020] In the metal deposition, the molar ratio of the metal nitrate to the hydrofluoric acid is preferably 1:(2.5 to 3.5), for example 1:3.

[0021] In the metal deposition, the metal nitrate is, for example, silver nitrate and / or copper nitrate.

[0022] In the metal deposition, the concentration of the metal nitrate is preferably 0.8 to 1.5 mol / L, for example 1 mol / L.

[0023] In the metal deposition, the concentration of hydrofluoric acid is preferably 2 to 4 mol / L, for example 3 mol / L.

[0024] The etching solution used in the chemical etching is preferably a mixture of hydrofluoric acid and hydrogen peroxide.

[0025] In the chemical etching, the molar concentration of hydrofluoric acid to hydrogen peroxide is preferably 3:(0.15-0.25), for example 3:0.2.

[0026] In the chemical etching, the volume ratio of hydrofluoric acid to hydrogen peroxide is preferably (4-6):1, for example, 5:1.

[0027] In the chemical etching, the concentration of hydrofluoric acid is preferably 2 to 4 mol / L, for example 3 mol / L.

[0028] In the chemical etching, the concentration of hydrogen peroxide is preferably 0.15 to 0.25 mol / L, for example 0.2 mol / L.

[0029] In this invention, the lithium ions preferably exist in the porous silicon-oxygen material in the form of Li2SiO3 and / or Li2Si2O5.

[0030] In this invention, the lithium ions are preferably uniformly distributed in the porous silicon-oxygen material.

[0031] In this invention, the mass ratio of lithium to the total mass of the silicon-oxygen composite material is 5-25%.

[0032] In this invention, the D50 particle size of the porous silica material is preferably 2 to 15 μm, for example 5 μm, 6 μm, 7 μm or 8 μm.

[0033] As those skilled in the art will know, the porous silica material containing lithium ions is generally obtained by lithium adsorption.

[0034] The lithium absorption process typically refers to the mixing of the raw material to be absorbed with a solution of the organic lithium compound.

[0035] The raw material for lithium absorption can be porous silicon-oxygen material or silicon-oxygen raw material.

[0036] The mixing time can be conventional in the art, generally 1 to 48 hours, for example 2 hours.

[0037] The mixing is generally done by stirring.

[0038] The organolithium compound may be a conventional organolithium compound used in the art for preparing pre-lithiated silicon oxide materials, typically one or more of butyllithium, phenyllithium, naphthyllithium, methyllithium, and ethyllithium, such as phenyllithium.

[0039] The solvent in the solution of the organolithium compound generally needs to be able to dissolve the organolithium compound, such as one or more of benzene, cyclohexane, tetrahydrofuran, pentane, diethyl ether and petroleum ether.

[0040] Those skilled in the art will recognize from the described lithium absorption process that a filtration operation is generally included after lithium absorption to obtain the lithium-absorbed porous silica material. The room temperature generally refers to 0–35°C.

[0041] In this invention, SiO is preferably distributed within the porous silica material. x x is 0 to 1 and not 0. Preferably, the silicon oxide material in the porous silicon oxide material is SiO2. x x is 0 to 1 and not 0. In this invention, the silicon-oxygen material in the porous silicon-oxygen material is not suitable for silicon dioxide. If silicon dioxide is used, the composite material with the better specific capacity and cycle stability of this invention cannot be obtained.

[0042] In this invention, the carbon coating preferably refers to the process of mixing the porous silica material with a carbon source at the carbon coating temperature.

[0043] Preferably, the mixture is a mixture obtained by mixing the porous silica material and the carbon source at a low temperature, and the low temperature mixing temperature is preferably 80-120°C, for example 100°C.

[0044] In this invention, the carbon coating temperature is preferably 500-700°C, for example 550°C, 600°C or 650°C.

[0045] In this invention, when the carbon coating is performed, the mass ratio of the porous silica material to the carbon source is preferably 1:(0.2 to 0.4), for example 1:0.3.

[0046] In this invention, the carbon source for carbon coating can be conventional in the art, preferably including any one or more combinations of 9,10-dibromoanthracene, 1,3,5-tris(4-iodo-2-biphenyl)benzene, 6,11-dibromo-1,2,3,4-tetraphenyltriphenylene, and 10,10-dibromo-9,9-bidianethracene.

[0047] In this invention, the carbon coating is generally carried out in a tube furnace.

[0048] The carbon coating is typically carried out under an inert atmosphere, such as argon.

[0049] In this invention, to obtain a pre-lithiated silicon-oxygen composite material with a relatively uniform particle size distribution, the carbon coating process generally includes sieving. The mesh size of the sieve is, for example, 300 mesh.

[0050] This invention provides a silicon-oxygen composite material, which is prepared by the above-described method.

[0051] This invention provides a silicon-oxygen composite material with a core-shell structure, comprising a core and an outer shell, wherein the core is a porous silicon-oxygen material and the outer shell is a carbon layer;

[0052] The porosity of the porous silica material is 5-30%;

[0053] The porous silica material contains Li2SiO3 and / or Li2Si2O5.

[0054] In this invention, the particle size D50 of the core is preferably 2 to 15 μm, for example 5 μm, 5.6 μm, 5.7 μm, 5.5 μm, 5.4 μm, 5.36 μm, 7 μm or 8 μm.

[0055] In this invention, the silicon-oxygen material in the porous silicon-oxygen material is preferably SiO2. x x is 0 to 1 and is not 0.

[0056] In this invention, the porosity of the porous silica material is preferably 10-21%, for example 11%, 12%, 13%, 14%, 14.8%, 14.9%, 15%, 15.2%, 15.1%, 16%, 17%, 18%, 19%, or 20.1%.

[0057] In this invention, the mass of lithium in the porous silicon-oxygen material is preferably 5-25% of the total mass of the silicon-oxygen composite material.

[0058] In this invention, the pore size of the porous material in the silicon-oxygen composite material can be 2-2000 nm.

[0059] In this invention, the thickness of the carbon layer is preferably 10 to 1000 nm.

[0060] In this invention, the mass ratio of the carbon layer to the silicon-oxygen composite material can be conventional in the art, for example, 1 to 10%.

[0061] In this invention, X-ray diffraction of the silicon-oxygen composite material was performed using Cu-Ka rays, and characteristic peaks of lithium silicate Li2SiO3 were observed at 2θ of 19.1°, 26.8°, 33.1° and 38.7°, respectively, and / or characteristic peaks of lithium silicate Li2Si2O5 were observed at 2θ of 24.4°.

[0062] In this invention, the median particle size of the silicon-oxygen composite material can be 2–15 μm.

[0063] In this invention, the specific surface area of ​​the silicon-oxygen composite material can be 2–10 m². 2 / g, for example 2.7m 2 / g, 3.6m 2 / g, 3.7m 2 / g, 3.8m 2 / g, 4.1m 2 / g or 5m 2 / g.

[0064] In this invention, the silicon-oxygen composite material has a first-cycle specific capacity of 1000mAh / g-2000mAh / g at 0.1C, preferably 1300-1500mAh / g, for example 1450mAh / g, 1375mAh / g, 1377mAh / g, 1374mAh / g, 1284mAh / g, 1368mAh / g, 1428mAh / g or 1411mAh / g.

[0065] In this invention, the initial coulombic efficiency of the silicon-oxygen composite material at 0.1C can be 84-91%, for example 87% or 90%.

[0066] In this invention, the capacity retention rate of the silicon-oxygen composite material after 50 cycles at 0.1C can be 85-99%, for example 95%, 96%, 97%, 98% or 98.5%.

[0067] The present invention also provides a negative electrode sheet comprising the aforementioned silicon-oxygen composite material.

[0068] In this invention, the negative electrode sheet can be prepared using a method commonly used in the art, generally including the following steps: the mixture of the silicon-oxygen composite material, binder and conductive agent is homogenized and then coated to obtain the negative electrode sheet.

[0069] In the mixture, the mass ratio of the silicon-oxygen composite material, the binder, and the conductive agent is, for example, 70:15:15.

[0070] The present invention also provides a lithium battery comprising the above-described negative electrode sheet.

[0071] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0072] The reagents and raw materials used in this invention are all commercially available.

[0073] The positive and progressive effects of this invention are as follows: the core of the silicon-oxygen composite material is a porous structure with a specific porosity, and the outer shell is a carbon layer. The porous structure of the core provides space that can effectively accommodate the volume expansion of the core during charging and discharging, maintaining the integrity of the material and thus ensuring the integrity of the electrode, avoiding excessive battery expansion. The carbon layer covering the surface not only synergistically suppresses volume expansion but also increases the conductivity of the material. Therefore, the silicon-oxygen composite material with a porous structure provided by this invention has the characteristics of high initial coulombic efficiency, high specific capacity, and low expansion, and can be applied to lithium-ion batteries such as square batteries, pouch batteries, and cylindrical batteries; at the same time, its synthesis method is simple, easy to control, and easy to achieve large-scale production. Attached Figure Description

[0074] Figure 1 The image shows the XRD pattern of the pre-lithiated silicon-oxygen composite material of Example 1.

[0075] Figure 2 The image shows a SEM image of the pre-lithiated silicon-oxygen composite material from Example 1. Detailed Implementation

[0076] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0077] Example 1

[0078] (1) Metal deposition

[0079] The silicon-oxygen material used in this embodiment is SiO with a particle size D50 of 6.0 μm and a dosage of 1 kg.

[0080] The silicon oxide material is immersed in a mixed solution of silver nitrate and hydrofluoric acid and stirred until homogeneous at a temperature of 25°C. The concentration of silver nitrate is 1M, the concentration of hydrofluoric acid is 3M, and the volume ratio of silver nitrate to hydrofluoric acid is 1:1, resulting in a silicon oxide material with metal deposited on its surface.

[0081] (2) Chemical etching

[0082] Next, the deposited metal silica material is immersed in a mixed solution containing hydrofluoric acid and hydrogen peroxide and stirred continuously for 6 hours. The concentration of hydrofluoric acid is 3M, the concentration of hydrogen peroxide is 0.2M, and the volume ratio of the two is 5:1. Finally, the porous silica material is obtained by soaking in nitric acid solution to remove the metallic silver.

[0083] (3) Lithium absorption

[0084] The porous silica material was immersed in a butyllithium solution with cyclohexane as the solvent to absorb lithium. After stirring the solution for 2 hours, the lithium-absorbed porous silica material was obtained by filtration.

[0085] (4) Carbon coating

[0086] The porous silica material prepared above was mixed with a carbon source at 100°C for 1 hour and then heat-treated at 600°C for 12 hours. The carbon source was 9,10-dibromoanthracene and the amount of carbon source used was 0.3 kg.

[0087] Example 2

[0088] Immerse in a solution containing 3M hydrofluoric acid and 0.2M hydrogen peroxide, and stir continuously for 1 hour. The remaining preparation process parameters are the same as in Example 1.

[0089] Example 3

[0090] Immerse in a solution containing 3M hydrofluoric acid and 0.2M hydrogen peroxide, and stir continuously for 8 hours. The remaining preparation process parameters are the same as in Example 1.

[0091] Example 4

[0092] Immerse in a solution containing 3M hydrofluoric acid and 0.2M hydrogen peroxide, and stir continuously for 10 hours. The remaining preparation process parameters are the same as in Example 1.

[0093] Example 5

[0094] Copper nitrate was used instead of silver nitrate, and the other preparation process parameters were the same as in Example 1.

[0095] Example 6

[0096] The lithium absorption stirring time was 1 hour, and the other preparation process parameters were the same as in Example 1.

[0097] Example 7

[0098] The lithium absorption stirring time was 2 hours, and the other preparation process parameters were the same as in Example 1.

[0099] Comparative Example 1

[0100] Based on step (1) of Example 1, silver nitrate is not added, and the remaining process parameters are the same as in Example 1.

[0101] Comparative Example 2

[0102] Based on step (1) of Example 1, the chemical etching process in step (2) is omitted, and the remaining process parameters are the same as in Example 1.

[0103] Comparative Example 3

[0104] The carbon coating temperature was increased to 800℃, and the remaining process parameters were the same as in Example 1.

[0105] Example 1

[0106] The performance tests of the pre-lithiated silicon oxide composite materials in Examples 1-6 and Comparative Examples 1-3 are as follows.

[0107] (1) XRD characterization of pre-lithiated silicon oxide composite material

[0108] The XRD pattern of the pre-lithiated silicon-oxygen composite material in Example 1 is as follows: Figure 2 As shown. From Figure 2 As can be seen from the data, the pre-lithiated silicon oxide material in this embodiment has characteristic peaks of lithium silicate Li2SiO3 at 2θ of 19.1°, 26.8°, 33.1° and 38.7°, respectively, indicating that the formed lithium silicate is Li2SiO3.

[0109] XRD characterization of the pre-lithiated silicon oxide composites in Examples 2-4 showed that they all contained characteristic peaks of Li₂SiO₃ consistent with those in Example 1. Example 5 showed a characteristic peak of lithium silicate (Li₂Si₂O₅) at 2θ = 24.4°, indicating that Li₂Si₂O₅ was formed. Example 6 showed characteristic peaks of both lithium silicate (Li₂SiO₃) and Li₂Si₂O₅, indicating that the lithium silicate in this sample was a mixture of Li₂SiO₃ and Li₂Si₂O₅.

[0110] XRD characterization of the pre-lithiated silicon oxide composites of Comparative Examples 1–3 showed that they all contained Li2SiO3 characteristic peaks consistent with those of Example 1. Among them, the peak intensity of Comparative Example 3 was very high, indicating that the grain size was larger.

[0111] (2) Structural characterization of pre-lithiated silicon oxide composite material, the test results are shown in Table 1.

[0112] Example 1 has a porous structure, such as Figure 1As shown, a porous silicon oxide material serves as the core, with a carbon layer deposited by chemical vapor deposition coating the surface. In Examples 3 and 4, the number of pores increases and the porosity increases with etching time. However, Comparative Example 1, which did not undergo metal-assisted etching, ultimately did not form a porous structure. Comparative Example 2, which did not involve etching, also ultimately did not form a porous structure.

[0113] (3) Battery performance test

[0114] The pre-lithiated silicon oxide composite material obtained in Example 1 was homogenized and coated with a mixture of pre-lithiated silicon oxide composite material, binder (PAA), and conductive agent (SP) in a ratio of 70:15:15 to obtain a negative electrode sheet. The negative electrode sheet was then assembled into a half-cell, and the test results are shown in Table 1 below.

[0115] Examples 2-6 and Comparative Examples 1-3 prepared negative electrode sheets according to the same method and parameters as Example 1, and assembled them into half-cells for charge-discharge tests and cycle stability tests at 0.1C. The test results are shown in Table 1 below.

[0116] Table 1

[0117]

[0118] The experimental results above show that, in Examples 1 to 6 of the present invention, the porous pre-lithiated silicon oxide composite material with a porosity of 5 to 30% prepared under carbonization treatment at 500 to 750°C can simultaneously possess high specific capacity and cycle stability.

[0119] As can be seen, the present invention can effectively mitigate volume expansion during charging and discharging, resulting in minimal rebound of the electrode when fully charged. A porosity of less than 20% is sufficient to effectively buffer volume expansion; however, in Example 4, the porosity was greater than 20%, leading to a significant decrease in specific capacity.

[0120] In contrast, Comparative Examples 1 and 2 lacked a porous structure, resulting in a very high rebound rate and significantly poor cycling performance. In Comparative Example 3, the carbonization temperature exceeded 750℃, causing the porous pre-lithiated silicon oxide material to sinter, resulting in very large grains. This led to a significant decrease in specific capacity and initial coulombic efficiency, as well as a significant decline in cycling stability.

[0121] The pre-lithiated silicon-oxygen composite material of this invention has a core mainly containing one or more of Li₂SiO₃ and Li₂Si₂O₅, and a carbon outer shell. The pre-inserted lithium in the core reduces the consumption of active lithium ions in the positive electrode during the initial lithium intercalation process, improving the initial coulombic efficiency. Furthermore, the porous structure of the core provides space to effectively accommodate the volume expansion of the core during charge and discharge, maintaining the integrity of the material and thus ensuring the integrity of the electrode, preventing excessive battery expansion. Simultaneously, the carbon coating on the surface increases the conductivity of the material. Therefore, the pre-lithiated silicon-oxygen composite material with a porous structure provided by this invention features high initial coulombic efficiency, high specific capacity, and low expansion, making it applicable to lithium-ion batteries such as prismatic batteries, pouch batteries, and cylindrical batteries. Moreover, its synthesis method is simple, easy to control, and readily scalable.

[0122] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0123] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a silicon-oxygen composite material, characterized in that, It includes the following steps: Porous silica materials are obtained by carbon coating; The method for preparing the porous silicon-oxygen material includes the following steps: the silicon-oxygen raw material is sequentially subjected to metal deposition, chemical etching, and lithium adsorption. The metal deposition refers to immersing the silicon-oxygen raw material in a mixture of metal nitrate and hydrofluoric acid, wherein the metal nitrate is silver nitrate and / or copper nitrate. The chemical etching uses a mixture of hydrofluoric acid and hydrogen peroxide as the etching solution. The lithium adsorption refers to mixing the raw material to be lithium adsorbed with a solution of an organolithium compound, wherein the raw material to be lithium adsorbed refers to the silicon-oxygen raw material that has been sequentially subjected to the metal deposition and chemical etching. In the metal deposition, the molar ratio of the metal nitrate to the hydrofluoric acid is 1:(2.5~3.5). In the metal deposition, the concentration of the metal nitrate is 0.8~1.5 mol / L; In the metal deposition, the concentration of hydrofluoric acid is 2~4 mol / L; In the chemical etching process, the volume ratio of hydrofluoric acid to hydrogen peroxide is (4~6):1; In the chemical etching process, the concentration of hydrofluoric acid is 2-4 mol / L; In the chemical etching process, the concentration of hydrogen peroxide is 0.15~0.25 mol / L; The porosity of the porous silica material is 12-21%; Lithium ions are distributed within the porous silica material; The carbon coating temperature is 600~650℃.

2. The method for preparing the silicon-oxygen composite material as described in claim 1, characterized in that, The porosity of the porous silica material is 13-21%, and the porosity refers to the percentage of the volume of pores in the porous silica material to the total volume of the porous silica material when it contains no pores. And / or, SiO is distributed within the porous silica material. x x is between 0 and 1, and is not 0.

3. The method for preparing the silicon-oxygen composite material as described in claim 2, characterized in that, The porosity of the porous silica material is 13%, 14%, 14.8%, 14.9%, 15%, 15.2%, 15.1%, 16%, 17%, 18%, 19%, or 20.1%. And / or, the silicon oxide material in the porous silicon oxide material is SiO2. x x is between 0 and 1, and is not 0.

4. The method for preparing the silicon-oxygen composite material as described in claim 1, characterized in that, In the metal deposition, the volume ratio of the metal nitrate to the hydrofluoric acid is 1:1; And / or, in the metal deposition, the molar ratio of the metal nitrate to the hydrofluoric acid is 1:3; And / or, in the metal deposition, the concentration of the metal nitrate is 1 mol / L; And / or, in the metal deposition, the concentration of hydrofluoric acid is 3 mol / L; And / or, in the chemical etching, the molar concentration ratio of the hydrofluoric acid to the hydrogen peroxide is 3:(0.15~0.25). And / or, in the chemical etching, the volume ratio of the hydrofluoric acid to the hydrogen peroxide is 5:1; And / or, in the chemical etching, the concentration of the hydrofluoric acid is 3 mol / L; And / or, in the chemical etching, the concentration of hydrogen peroxide is 0.2 mol / L.

5. The method for preparing the silicon-oxygen composite material as described in claim 4, characterized in that, In the chemical etching, the molar ratio of hydrofluoric acid to hydrogen peroxide is 3:0.

2.

6. The method for preparing the silicon-oxygen composite material as described in claim 1, characterized in that, The lithium ions exist in the porous silicon-oxygen material in the form of Li2SiO3 and / or Li2Si2O5. And / or, in the silicon-oxygen composite material, the mass ratio of lithium element to the total mass of the silicon-oxygen composite material is 5-25%; And / or, the D50 particle size of the porous silica material is 2~15μm.

7. The method for preparing the silicon-oxygen composite material as described in claim 6, characterized in that, The D50 particle size of the porous silica material is 5μm, 5.6μm, 5.7μm, 5.5μm, 5.4μm, 5.36μm, 7μm or 8μm.

8. The method for preparing the silicon-oxygen composite material as described in claim 1, characterized in that, The organolithium compound is one or more selected from butyllithium, phenyllithium, naphthyllithium, methyllithium, and ethyllithium.

9. The method for preparing the silicon-oxygen composite material as described in claim 8, characterized in that, The organolithium compound is phenyllithium.

10. The method for preparing the silicon-oxygen composite material as described in claim 1, characterized in that, The solvent in the solution of the organolithium compound includes one or more of benzene, cyclohexane, tetrahydrofuran, pentane, diethyl ether, and petroleum ether.

11. The method for preparing the silicon-oxygen composite material according to any one of claims 1 to 10, characterized in that, The carbon coating temperature is 600℃ or 650℃; And / or, the carbon coating refers to the process of mixing the porous silica material with a carbon source at the carbon coating temperature.

12. The method for preparing the silicon-oxygen composite material as described in claim 11, characterized in that, The mixture is a mixture obtained by mixing the porous silica material and the carbon source at 80~120°C.

13. The method for preparing the silicon-oxygen composite material as described in claim 12, characterized in that, The mixture is a mixture obtained by mixing the porous silica material and the carbon source at 100°C.

14. The method for preparing the silicon-oxygen composite material as described in claim 11, characterized in that, When carbon coating is used, the mass ratio of the porous silica material to the carbon source is 1:(0.2~0.4).

15. The method for preparing the silicon-oxygen composite material as described in claim 14, characterized in that, During carbon coating, the mass ratio of the porous silica material to the carbon source is 1:0.

3.

16. The method for preparing the silicon-oxygen composite material as described in claim 11, characterized in that, The carbon source for carbon coating includes one or more of 9,10-dibromoanthracene, 1,3,5-tris(4-iodo-2-biphenyl)benzene, 6,11-dibromo-1,2,3,4-tetraphenyltriphenylene, and 10,10-dibromo-9,9-bidianethracene.

17. A silicon-oxygen composite material, characterized in that, It is prepared by the method of any one of claims 1 to 16 for the preparation of silicon-oxygen composite materials.

18. The silicon-oxygen composite material as described in claim 17, characterized in that, It has a core-shell structure, which includes a core and an outer shell. The core is a porous silicon-oxygen material, and the outer shell is a carbon layer. The porous silica material contains Li2SiO3 and / or Li2Si2O5.

19. The silicon-oxygen composite material as described in claim 18, characterized in that, The particle size D50 of the core is 2~15μm; And / or, SiO is distributed in the porous silica material. x x is between 0 and 1, and is not 0; And / or, the porosity of the porous silica material is 13-21%; And / or, in the porous silicon-oxygen material, the mass ratio of lithium to the total mass of the silicon-oxygen composite material is 5-25%; And / or, the pore size of the porous material in the silicon-oxygen composite is 2-2000 nm; And / or, the thickness of the carbon layer is 10~1000 nm; And / or, the mass ratio of the carbon layer to the silicon-oxygen composite material is 1~10%; And / or, X-ray diffraction of the silicon-oxygen composite material was performed using Cu-Ka rays, and characteristic peaks of lithium silicate Li2SiO3 were observed at 2θ of 19.1°, 26.8°, 33.1° and 38.7°, respectively, and / or characteristic peaks of lithium silicate Li2Si2O5 were observed at 2θ of 24.4°. And / or, the median particle size of the silicon-oxygen composite material is 2~15μm; And / or, the specific surface area of ​​the silicon-oxygen composite material is 2~10 m². 2 / g; And / or, the silicon-oxygen composite material has a first-cycle specific capacity of 1000mAh / g-2000mAh / g at 0.1C; And / or, the silicon-oxygen composite material has an initial coulombic efficiency of 84-91% at 0.1C; And / or, the silicon-oxygen composite material retains 85-99% of its capacity after 50 cycles at 0.1C.

20. The silicon-oxygen composite material as described in claim 19, characterized in that, The particle size D50 of the core is 5μm, 5.6μm, 5.7μm, 5.5μm, 5.4μm, 5.36μm, 7μm or 8μm; And / or, the silicon oxide material in the porous silicon oxide material is SiO2. x x is between 0 and 1, and is not 0; And / or, the porosity of the porous silica material is 13%, 14%, 14.8%, 14.9%, 15%, 15.2%, 15.1%, 16%, 17%, 18%, 19%, or 20.1%; And / or, the specific surface area of ​​the silicon-oxygen composite material is 2.7 m². 2 / g, 3.6m 2 / g, 3.7m 2 / g, 3.8m 2 / g, 4.1m 2 / g or 5m 2 / g; And / or, the silicon-oxygen composite material has a first-cycle specific capacity of 1300~1500mAh / g at 0.1C; And / or, the silicon-oxygen composite material has an initial coulombic efficiency of 87% or 90% at 0.1C; And / or, the capacity retention of the silicon-oxygen composite material after 50 cycles at 0.1C is 95%, 96%, 97%, 98%, or 98.5%.

21. The silicon-oxygen composite material as described in claim 20, characterized in that, The silicon-oxygen composite material has a first-cycle specific capacity of 1450mAh / g, 1375mAh / g, 1377mAh / g, 1374mAh / g, 1284mAh / g, 1368mAh / g, 1428mAh / g, or 1411mAh / g at 0.1C.

22. A negative electrode sheet, characterized in that, It includes the silicon-oxygen composite material as described in any one of claims 17 to 21.

23. A lithium battery, characterized in that, It includes the negative electrode sheet as described in claim 22.

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