Lithium-silicon-oxygen composite material and preparation method thereof

Abstract

The invention discloses a lithium-silicon-oxygen composite material and a preparation method thereof, and the preparation method comprises the following steps: S1, uniformly mixing a lithium-containing alloy, silicon oxide powder and a reaction assistant, carrying out ball milling treatment and / or heating treatment, removing lithium in the lithium-containing alloy, and reacting with silicon oxide to obtain a lithium-silicon-oxygen material containing metal powder residues; and S2, separating the metal powder residues in the lithium-silicon-oxygen material containing the metal powder residues, and carrying out heating treatment in an inert atmosphere to obtain the lithium-silicon-oxygen composite material. The lithium-silicon-oxygen composite material prepared by the method shows excellent performance when being applied to a negative electrode material of a lithium ion battery, and the first coulombic efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery electrode materials, and particularly to a lithium silicon oxide composite material and a preparation method thereof. Background Art

[0002] In recent years, there has been a strong demand for high-capacity lithium-ion batteries in small electronic products and electric vehicles, which has led to the development of using silicon oxides to replace carbon-based anode materials. A lithium-ion secondary battery has a positive electrode, a negative electrode, a separator, and an electrolyte, and the negative electrode contains a negative electrode active material related to the charge and discharge reaction. As the negative electrode active material, the theoretical capacity of currently widely used graphite (372 mAh / g) is far lower than that of silicon (4200 mAh / g). However, silicon undergoes severe volume expansion and contraction during charge and discharge, causing particle fragmentation. At the cracks, the electrolyte decomposes and a solid electrolyte film is formed, resulting in excessive consumption of the limited electrolyte in the battery and ultimately leading to battery deterioration.

[0003] As a substitute, silicon oxide materials such as silicon monoxide with a silicon-oxygen atomic ratio approximately of 1:1 have lower volume expansion and are more suitable for use as the negative electrode material of lithium-ion batteries. However, when silicon oxides are used as the negative electrode of lithium-ion batteries, there is a problem of low initial Coulomb efficiency. The initial Coulomb efficiency refers to the ratio of the discharge capacity to the charge capacity during the first charge and discharge of a lithium-ion battery; a lower initial Coulomb efficiency of the negative electrode will result in a reduction in the actual available cycle energy density of the lithium-ion battery and cause irreversible lithium loss in the corresponding positive electrode. Based on previous research, the reason for the low initial Coulomb efficiency of silicon oxides is that lithium-containing silicon oxides are formed when lithium ions react with silicon oxides during the first lithium intercalation process, and such lithium-containing silicon oxides cannot release lithium ions during the de-lithiation process.

[0004] To solve the above problems, pre-lithiation technology, which pre-reacts silicon oxides with lithium-containing compounds to form lithium silicon oxide composites before the first charge and discharge, is an effective means. For example, Chinese Patent CN102214824B mixes silicon oxides with lithium hydride, metallic lithium, etc. and calcines them to form lithium-containing silicon oxides before using them as the negative electrode of a lithium-ion battery, thereby improving the initial Coulomb efficiency; however, such methods have low reaction controllability, and the lithium-containing raw materials have high toxicity and danger; although the pre-lithiation technology of silicon oxide materials has been improved over the years, due to the need for high-temperature calcination, the internal crystal grains of silicon oxides or lithium-containing silicon oxides grow larger, and their performance deteriorates when applied as the negative electrode material of lithium-ion batteries. Summary of the Invention

[0005] Aiming at the defects existing in the prior art, the object of the present invention is to provide a lithium silicon oxide composite material and a preparation method thereof. The pre-lithiation of silicon oxide is completed by using a lithium-containing alloy and a reaction assistant, avoiding the problems of grain growth and performance deterioration of the material caused by the high-temperature treatment of mixing lithium-containing compounds and silicon oxide in the prior art. The lithium silicon oxide composite material prepared by the present invention exhibits excellent performance when applied to the negative electrode material of a lithium-ion battery, achieving an improvement in the first Coulomb efficiency.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a preparation method of a lithium silicon oxide composite material, comprising the following steps:

[0008] S1, after uniformly mixing a lithium-containing alloy, silicon oxide powder, and a reaction assistant, and performing ball milling treatment and / or heat treatment, the lithium in the lithium-containing alloy is removed and reacts with the silicon oxide to obtain a lithium silicon oxide material containing metal powder residues;

[0009] S2, after separating the metal powder residues in the lithium silicon oxide material containing metal powder residues, performing heat treatment in an inert atmosphere to obtain a lithium silicon oxide composite material.

[0010] Preferably, in the step S1, the preparation method of the lithium-containing alloy is as follows:

[0011] After uniformly mixing metallic lithium powder or lithium-containing compounds with metal powder or liquid metal by normal temperature stirring mixing or ball milling mixing or heat mixing, a lithium-containing alloy is obtained.

[0012] Preferably, the size of the metallic lithium powder or lithium-containing compounds is 0.5 - 20 μm; the lithium-containing compounds are selected from one of lithium hydride, lithium hydroxide, lithium carbonate, lithium bicarbonate, and lithium oxide; and / or

[0013] The metal powder or liquid metal is selected from one of beryllium, magnesium, aluminum, lead, mercury, zinc, copper, silver, tin, sodium, potassium, and germanium; the particle size of the metal powder is 0.5 - 20 μm.

[0014] Preferably, a closed container is used during heat mixing, and it is carried out under the protection of an inert atmosphere, and the heating temperature is 100 - 1500 °C.

[0015] Preferably, during heat mixing, the oxygen content in the heating furnace is controlled below 100 ppm.

[0016] Preferably, the time of the normal temperature stirring mixing or ball milling mixing or heat mixing is 10 - 4000 min.

[0017] Preferably, the molar ratio of lithium atoms to metal atoms in the lithium-containing alloy is 3:1 - 1:3.

[0018] Preferably, in the step S1:

[0019] The lithium-containing alloy and the silicon oxide powder are mixed in a molar ratio of lithium atoms to silicon atoms of 1:200 to 1:2; and / or

[0020] The addition amount of the reaction assistant is 0.01% to 50% of the total volume of the lithium-containing alloy and the silicon oxide; and / or

[0021] In the silicon oxide, the molar ratio of silicon element to oxygen element is 1:10 to 999:1; the particle size of the silicon oxide is 0.5 to 50 μm.

[0022] Preferably, in the step S1:

[0023] The reaction assistant is selected from one or both of n-hexane and cyclohexane; or

[0024] The reaction assistant is selected from one or more of ether solvents, ketone solvents, ester solvents, polycyclic aromatic solvents, linear polyphenylene solvents, alcohol solvents and amine solvents; or

[0025] The reaction assistant is selected from one or more of ether solvents, ketone solvents, ester solvents, alcohol solvents and amine solvents dissolved with lithium salts.

[0026] Preferably, in the step S1, the mixing method is one or more of ball milling, stirring, kneading and mixing pressing; and a container made of zirconia material, alumina material or polymer material is used during mixing.

[0027] Preferably, in the step S1:

[0028] When ball milling treatment is adopted, it is carried out under the protection of an inert gas, the ball milling speed is 10 to 20000 r / min, and the ball milling time is 1 to 10080 minutes; or

[0029] When heat treatment is adopted, it is carried out under the protection of an inert atmosphere, the heating temperature is 100 to 1500 °C, and the heating time is 1 to 1440 minutes.

[0030] Preferably, in the step S2:

[0031] The separation method is screening, cyclone separation or magnetic separation;

[0032] The heat treatment is carried out under the protection of an inert atmosphere, the heating temperature is 300 to 1000 °C, and the heating time is 1 to 1440 minutes.

[0033] The second aspect of the present invention provides a lithium silicon oxide composite material prepared by the preparation method of the lithium silicon oxide composite material as described in the first aspect of the present invention, and the grain size of the lithium silicon oxide composite material is 0.5-50 μm.

[0034] The beneficial effects of the present invention are as follows:

[0035] 1. The present invention uses a lithium-containing alloy to complete the prelithiation of silicon oxide, and converts silicon oxide into a lithium silicon oxide composite material with a simple, safe and efficient prelithiation process;

[0036] 2. The present invention uses a lithium-containing alloy to complete the prelithiation of silicon oxide, avoiding the problems of grain growth and performance deterioration of materials caused by high-temperature treatment of mixing and calcining lithium compounds and silicon oxide in the prior art, and the grain size of the prepared lithium silicon oxide composite material is controllable;

[0037] 3. The lithium silicon oxide composite material prepared by the present invention exhibits excellent performance when applied to the negative electrode material of a lithium-ion battery, achieving an improvement in the initial Coulomb efficiency.

[0038] 4. The preparation method of the lithium silicon oxide composite material of the present invention has controllable process and simple steps, and can be prepared for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] By reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings, other features, objects and advantages of the present invention will become more apparent:

[0040] Figure 1 is a schematic flow chart of the preparation method of the lithium silicon oxide composite material of the present invention;

[0041] Figure 2 is an XRD pattern of the lithium silicon oxide composite material prepared in Example 1 of the present invention;

[0042] Figure 3 is an XRD pattern of the lithium silicon oxide composite material prepared in the comparative example. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form.

[0044] Combined with Figure 1 shown, a preparation method of a lithium silicon oxide composite material provided by the present invention includes the following steps:

[0045] S1, after uniformly mixing a lithium-containing alloy, silicon oxide powder, and a reaction assistant, and performing ball milling treatment and / or heat treatment, lithium in the lithium-containing alloy is removed and reacts with the silicon oxide to obtain a lithium silicon oxide material containing metal powder residues;

[0046] First, select a lithium-containing alloy: It can be made by oneself or purchased as a commercially available product. The molar ratio of lithium atoms to metal atoms in the lithium-containing alloy is 3:1 to 1:3, preferably 1:1.

[0047] The preparation process of the lithium-containing alloy is as follows: Take a certain amount of lithium metal powder (or lithium-containing compound) and metal powder (or liquid metal), and after mixing by stirring at room temperature or by ball milling or by heating, a lithium-containing alloy is made.

[0048] The size of the lithium metal powder (or lithium-containing compound) is 0.5 - 20 μm, preferably 10 - 15 μm; the lithium-containing compound is selected from one of lithium hydride, lithium hydroxide, lithium carbonate, lithium bicarbonate, and lithium oxide. The metal powder (or liquid metal) can be any metal that can form an alloy with lithium, such as one of beryllium, magnesium, aluminum, lead, mercury, zinc, copper, silver, tin, sodium, potassium, and germanium. Considering cost, safety, and processability, aluminum, magnesium, and germanium are preferred, and aluminum is more preferred; the particle size of the metal powder is 0.5 - 20 μm, preferably 1 - 15 μm, and it should be larger than the size of the silicon oxide powder.

[0049] During the preparation process of the lithium-containing alloy, the mixing time by stirring at room temperature or by ball milling or by heating is 10 - 4000 min, preferably 60 min. When heating and mixing, a closed container can be used. Place the lithium metal powder (or lithium-containing compound) and the metal powder (or liquid metal) in the closed container to reduce losses; the heating can be carried out under the protection of an inert atmosphere, and the heating temperature is 100 - 1500 °C, preferably 200 - 1200 °C, so that lithium liquefies (vaporizes) and is easy to form an alloy; when heating and mixing, the oxygen content in the heating furnace can be controlled below 100 ppm to avoid the formation of metal oxides and affect alloying.

[0050] The size of the silicon oxide powder is 0.5 - 50 μm, preferably 3 - 8 μm. Since silicon and oxygen are bonded by covalent bonds, the ratio of silicon and oxygen elements can be adjusted within a wide range. The silicon oxide can be a compound or mixture formed by silicon and oxygen elements, and the molar ratio of silicon element to oxygen element in the silicon oxide is 1:10 to 999:1. Preferably, the silicon oxide can be silicon monoxide (chemical formula SiO).

[0051] The reaction promoter can be a solvent or powder that does not participate in the reaction and is beneficial to the dispersion of the powder during ball milling, such as n-hexane and cyclohexane; it can also be a solvent or solution that helps the alloying reaction, which can be one or several of ether solvents, ketone solvents, ester solvents, polycyclic aromatic solvents, linear polyphenylene solvents, alcohol solvents, and amine solvents; it can also be one or several of ether solvents, ketone solvents, ester solvents, alcohol solvents, and amine solvents dissolved with lithium salts. Preferably, tetrahydrofuran and dimethyl carbonate (volume ratio 1:1) dissolved with lithium hexafluorophosphate are used.

[0052] The lithium-containing alloy and silicon oxide powder are mixed in a molar ratio of lithium atoms to silicon atoms of 1:200 to 1:2. The addition amount of the reaction promoter is 0.01% to 50% of the total tapped volume of the lithium-containing alloy and silicon oxide.

[0053] The lithium-containing alloy, silicon oxide powder, and reaction promoter are mixed evenly in one or several of the ways of ball milling, stirring, kneading, and mixing and pressing; during mixing, containers and equipment made of zirconia material, alumina material, or polymer material can be used; among them, ball milling can be carried out under the protection of an inert gas, and when using a lithium-containing alloy that does not react with air as the raw material, it can also be carried out in an air atmosphere; preferably, the mixing is carried out in an argon atmosphere. Then, ball milling treatment and / or heat treatment are carried out. The lithium in the lithium-containing alloy is removed and reacts with the silicon oxide to form a lithium silicon oxygen material, and the lithium-containing alloy becomes a metal powder again after de-lithiation. Moreover, under the action of ball milling treatment and heat treatment, the metal powder can agglomerate into a residue with a relatively large volume, which is easy to distinguish from the lithium silicon oxygen material. The lithium silicon oxygen material containing metal powder residue is obtained through the above-mentioned ball milling treatment and / or heat treatment; among them, the ball milling treatment is carried out under the protection of an inert atmosphere, the ball milling speed is 10 to 20000 r / min, and the ball milling time is 1 to 10080 minutes; the heat treatment is carried out under the protection of an inert atmosphere, the heating temperature is 100 to 1500 °C, and the heating time is 1 to 1440 minutes.

[0054] S2, after separating the metal powder residue in the lithium silicon oxygen material containing metal powder residue, heat treatment is carried out in an inert atmosphere to obtain a lithium silicon oxygen composite material.

[0055] The metal powder residue in the lithium silicon oxygen material containing metal powder residue is separated. The separation method can be screening, cyclone separation, or magnetic separation. Screening separation is preferred. When screening, the screening mesh size should be selected to ensure that the lithium silicon oxygen material can just pass through while blocking the metal powder, that is, the mesh pore size is between the size of the silicon oxide and the size of the metal powder; if the lithium-containing alloy is liquid, the mesh pore size during screening needs to be smaller than the size of the silicon oxide.

[0056] After separating the metal powder residue in the lithium silicon oxide material containing the metal powder residue, heat treatment is carried out under the protection of an inert atmosphere to make the lithium diffusion reaction in the material more uniform and form a lithium silicon oxide composite material; the heat treatment is carried out under the protection of an inert atmosphere, the heating temperature is 300-1000 °C, and the heating time is 1-1440 minutes.

[0057] All the reagents and raw materials used above are commercially available.

[0058] In the lithium silicon oxide composite material prepared above, the size of the silicon grains is 1-10 nm. When it is applied to the negative electrode material of a lithium ion battery, in the 0.1C constant current charge and discharge test, the initial Coulomb efficiency is ≥89%.

[0059] The following further introduces the lithium silicon oxide composite material of the present invention and its preparation method with specific examples.

[0060] Example 1

[0061] The preparation method of the lithium silicon oxide composite material of this example adopts the following steps:

[0062] (1) Mix 18 g of aluminum metal powder (median particle size 10 μm) with 2 g of metallic lithium powder and heat at 550 °C for 1 hour to make a lithium aluminum alloy.

[0063] (2) Mix 20 g of the obtained lithium aluminum alloy with 20 g of silicon oxide powder (median particle size 5 μm) and place it in a zirconia ball mill pot, add 80 g of zirconia beads, and the bead configuration is: 20 g of 3 mm, 20 g of 5 mm, 20 g of 7 mm, and 20 g of 11 mm. Then add 5 mL of reaction assistant (1 mol / L lithium hexafluorophosphate dissolved in tetrahydrofuran and dimethyl carbonate (volume ratio 1:1)) to the ball mill pot and ball mill at a speed of 500 r / min for 2400 min to obtain a lithium silicon oxide material containing metal powder residue;

[0064] (3) Screen the product obtained by ball milling through a 100-mesh sieve to separate the powder, place it in a crucible, keep it warm at 150 °C for 1 hour in a 200 sccm Ar gas flow, and screen it through a 1000-mesh vibrating sieve to separate the lithium silicon oxide material and the aluminum metal powder residue.

[0065] (4) Take 10 g of the sieved lithium silicon oxide material, keep it warm at 600 °C for 1 hour in a 200 sccm Ar gas flow, and after cooling, a pre-lithiated lithium silicon oxide composite material is obtained, and its silicon grain size is 1-8 nm.

[0066] Combined with Figure 2From the XRD diagram of the lithium-silicon-oxygen composite material shown, it can be seen from the peaks that the obtained product contains Si element, Li2SiO3, and Li2Si2O5, among which Li2SiO3 and Li2Si2O5 are stable lithium silicates obtained by the full reaction of lithium-containing compounds with silicon oxide, indicating that pre-lithiation produces obvious effects, and the obtained Si element peak is not sharp and the grain size is controllable.

[0067] Example 2

[0068] The preparation method of the lithium-silicon-oxygen composite material of this embodiment adopts the following steps:

[0069] (1) Using a polytetrafluoroethylene stirring blade and a polytetrafluoroethylene beaker, 0.5 g of metallic lithium powder was slowly added to 50 g of mercury under stirring conditions, and stirred at 800 r / min to prepare a lithium-mercury alloy.

[0070] (2) 50 g of the obtained lithium aluminum alloy and 10 g of silicon oxide powder (median particle size 5 μm) were mixed and placed in a zirconia ball mill, and 80 g of zirconia beads were added. The beads were configured as follows: 3 mm 20 g, 5 mm 20 g, 7 mm 20 g, and 11 mm 20 g. The mixture was ball milled at a speed of 500 r / min for 2400 min to obtain a lithium silicon oxide material containing metal powder residue;

[0071] (3) The powder obtained by ball milling is vibrated and sieved through a 2000-mesh screen to separate the lithium silicon oxide material, aluminum metal powder residue, and zirconium oxide beads.

[0072] (4) 10 g of the sieved lithium silicon oxygen material was taken and kept at 500° C. for 1 hour in a 200 sccm Ar gas flow. After cooling, a pre-lithiated lithium silicon oxygen composite material was obtained, and the silicon grain size was 1 to 3 nm.

[0073] Example 3

[0074] The preparation method of the lithium-silicon-oxygen composite material of this embodiment adopts the following steps:

[0075] (1) 18 g of germanium metal powder (median particle size 10 μm) was mixed with 2.3 g of lithium hydride and heated at 600° C. for 1 hour to prepare a lithium-germanium alloy.

[0076] (2) 20 g of the obtained lithium germanium alloy and 20 g of silicon oxide powder (median particle size 5 μm) were mixed and placed in a zirconia ball mill, and 80 g of zirconia beads were added. The beads were configured as follows: 20 g of 3 mm, 20 g of 5 mm, 20 g of 7 mm, and 20 g of 11 mm; 50 mL of n-hexane was then added to the ball mill, and the mixture was ball milled at a speed of 500 r / min for 2400 min to obtain a lithium silicon oxide material containing metal powder residue;

[0077] (3) The product obtained by ball milling is subjected to a 1000-mesh vibration sieve to separate the lithium silicon oxide material and the germanium metal powder residue and zirconium oxide beads.

[0078] (4) 10 g of the sieved lithium silicon oxygen material was taken and kept at 500° C. for 1 hour in a 200 sccm Ar gas flow. After cooling, a pre-lithiated lithium silicon oxygen composite material was obtained, and the silicon grain size was 1 to 3 nm.

[0079] Example 4

[0080] The preparation method of the lithium-silicon-oxygen composite material of this embodiment adopts the following steps:

[0081] (1) 18 g of germanium metal powder (median particle size 10 μm) and 2 g of lithium metal powder were placed at the two ends of an ark, separated and sealed, and heated at 880° C. for 1 hour to prepare a lithium-germanium alloy.

[0082] (2) 20 g of the obtained lithium germanium alloy and 20 g of silicon oxide powder (median particle size 5 μm) were mixed in a crucible and stirred with a glass rod, and the mixture was kept at 150° C. for 1 hour in a 200 sccm Ar gas flow to obtain a lithium silicon oxide material containing metal powder residue;

[0083] (3) The powder obtained by heating is vibrated and sieved through a 1000-mesh screen to separate the lithium silicon oxide material and the germanium metal powder residue.

[0084] (4) 10 g of the sieved lithium silicon oxygen material was taken and kept at 500° C. for 1 hour in a 200 sccm Ar gas flow. After cooling, a pre-lithiated lithium silicon oxygen composite material was obtained, and the silicon grain size was 1 to 3 nm.

[0085] Comparative Example

[0086] (1) 2 g of metallic lithium powder and 20 g of silicon oxide powder (median particle size 5 μm) were mixed and placed in a crucible, and the mixture was fully stirred using a glass rod. The stirred powder was kept at 500° C. for 1 hour in a 200 sccm Ar gas flow, and after cooling, a pre-lithiated lithium-silicon-oxygen composite material was obtained, wherein the silicon grain size was 10 to 20 nm.

[0087] The XRD pattern of the lithium silicon oxygen composite material prepared in this comparative example is as follows Figure 3 As shown, from the peak situation, it can be seen that the obtained product contains Si element, Li4SiO4, and Li2SiO3, among which Li2SiO3 is a stable lithium silicate obtained by the full reaction of lithium-containing compounds and silicon oxide, and Li4SiO4 is an unstable lithium silicate, which indicates that the pre-lithiation effect is poor, and the obtained Si element has a sharp peak and a too large grain size, which is not suitable for negative electrode materials of lithium-ion batteries.

[0088] Performance detection: Take 0.8 g of the lithium-silicon-oxygen composite material prepared in Example 1 and Comparative Example, 0.06 g of single-walled carbon nanotubes, 0.04 g of CMC binder, and 0.1 g of SBR binder, disperse them in 5 mL of water to form a uniform slurry, coat it on a copper foil, and after vacuum drying, stamp it into a circular electrode sheet. Using metallic lithium as the counter electrode, 1 mol / L LiPF6 / DMC + DEC + EC (volume ratio 1:1:1) as the electrolyte, and Celgard 2400 as the separator, a test battery is formed. Perform a 0.1C constant current charge-discharge test on the battery (1C = 1500 mAh / g), and the charge-discharge voltage range is 0.01 - 1.5 V. The obtained performance comparisons are shown in Table 1;

[0089] Table 1

[0090]

[0091] Combined with Example 1, Comparative Example 1 and the table, during 0.1C constant current charge-discharge, when the charge-discharge voltage is 1.5 V, the capacity of the lithium-silicon-oxygen composite material prepared in Example 1 is 1358 mAh / g, the initial Coulombic efficiency is 89.5%, and the number of cycles when the cycle capacity decays to 80% of the initial capacity reaches 542 times, all of which are superior to the lithium-silicon-oxygen composite materials prepared in the comparative examples.

[0092] Thus, the present invention uses a lithium-containing alloy and a reaction assistant to complete the prelithiation of silicon oxide, avoiding the problems of grain growth and performance deterioration of the material caused by the high-temperature treatment of mixing and calcining lithium-containing compounds with silicon oxide in the prior art. The lithium-silicon-oxygen composite material prepared by the present invention exhibits excellent performance when applied to the negative electrode material of a lithium-ion battery, achieving an improvement in the initial Coulombic efficiency.

[0093] In summary, the above embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A preparation method of a lithium silicon oxygen composite material, characterized in that, It includes the following steps: S1. After uniformly mixing a lithium-containing alloy, silicon oxide powder, and a reaction assistant, and then performing ball milling treatment and / or heat treatment, lithium in the lithium-containing alloy is removed to react with the silicon oxide, obtaining a lithium-silicon-oxygen material containing metal powder residues; S2. After separating the metal powder residues in the lithium-silicon-oxygen material containing metal powder residues, heat treatment is performed in an inert atmosphere to obtain a lithium-silicon-oxygen composite material.

2. The preparation method of the lithium silicon oxide composite material according to claim 1, characterized in that, In step S1, the preparation method of the lithium-containing alloy is as follows: Lithium metal powder or lithium-containing compound and metal powder or liquid metal are mixed by normal temperature stirring, ball milling, or heating to obtain a lithium-containing alloy.

3. The preparation method of the lithium silicon oxide composite material according to claim 2, characterized in that, The size of the lithium metal powder or lithium-containing compound is 0.5 - 20 μm; the lithium-containing compound is selected from one of lithium hydride, lithium hydroxide, lithium carbonate, lithium bicarbonate, and lithium oxide; and / or The metal powder or liquid metal is selected from one of beryllium, magnesium, aluminum, lead, mercury, zinc, copper, silver, tin, sodium, potassium, and germanium; the particle size of the metal powder is 0.5 - 20 μm.

4. The preparation method of the lithium silicon oxygen composite material according to claim 2, wherein, When heating and mixing, a closed container is used and carried out under the protection of an inert atmosphere, and the heating temperature is 100 - 1500 °C.

5. The preparation method of the lithium silicon oxide composite material according to claim 2, characterized in that, When heating and mixing, the oxygen content in the heating furnace is controlled below 100 ppm.

6. The preparation method of the lithium silicon oxygen composite material according to claim 2, characterized in that, The time of the normal temperature stirring mixing, ball milling mixing, or heating mixing is 10 - 4000 min.

7. The preparation method of the lithium silicon oxide composite material according to claim 2, characterized in that, The molar ratio of lithium atoms to metal atoms in the lithium-containing alloy is 3:1 - 1:

3.

8. The preparation method of the lithium silicon oxide composite material according to claim 1, characterized in that, In step S1: The lithium-containing alloy and the silicon oxide powder are mixed in a molar ratio of lithium atoms to silicon atoms of 1:200 - 1:2; and / or The addition amount of the reaction assistant is 0.01% - 50% of the total volume of the lithium-containing alloy and the silicon oxide; and / or The molar ratio of silicon element to oxygen element in the silicon oxide is 1:10 - 999:1; the particle size of the silicon oxide is 0.5 - 50 μm.

9. The preparation method of the lithium silicon oxide composite material according to claim 1, characterized in that, In step S1: The reaction assistant is selected from one or both of n-hexane and cyclohexane; or The reaction assistant is selected from one or several of ether solvents, ketone solvents, ester solvents, polycyclic aromatic solvents, linear polyphenylene solvents, alcohol solvents, and amine solvents; or The reaction assistant is selected from one or several of ether solvents, ketone solvents, ester solvents, alcohol solvents, and amine solvents dissolved with lithium salts.

10. The preparation method of the lithium silicon oxygen composite material according to claim 1, wherein, In step S1, the mixing method is one or several of ball milling, stirring, kneading, and mixing pressing; when mixing, a container made of zirconia material, alumina material, or polymer material is used.

11. The preparation method of the lithium silicon oxygen composite material according to claim 1, characterized in that, In step S1: When performing ball milling treatment, it is carried out under the protection of an inert gas, the ball milling speed is 10 - 20000 r / min, and the ball milling time is 1 - 10080 minutes; and / or When performing heat treatment, it is carried out under the protection of an inert atmosphere, the heating temperature is 100 - 1500 °C, and the heating time is 1 - 1440 minutes.

12. The preparation method of the lithium silicon oxygen composite material according to claim 1, characterized in that In step S2: The separation method is screening, cyclone separation, or magnetic separation; The heat treatment is carried out under the protection of an inert atmosphere, the heating temperature is 300 - 1000 °C, and the heating time is 1 - 1440 minutes.

13. A lithium-silicon-oxygen composite material prepared by the method for preparing a lithium-silicon-oxygen composite material according to claims 1 to 12, characterized in that, The silicon grain size in the lithium-silicon-oxygen composite material is 1 - 8 nm.

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