Negative electrode material and preparation method thereof, lithium ion battery

Abstract

The present application provides a negative electrode material containing an active material, a method for preparing the same, and a lithium ion battery, wherein the active material comprises a silicon oxide and a compound of metal M, and the compound of metal M comprises at least one of an oxide of metal M and a silicate of metal M, where metal M is selected from at least one metal having an electronegativity of less than 1.8. The negative electrode material, method for preparing the same, and lithium ion battery according to the present application can reduce the volume expansion of the negative electrode material and improve the rate performance and cycle stability of the negative electrode material.

Description

[Technical Field]

[0001] This application claims priority from a Chinese patent application bearing application number "202211627204.9" and title "Negative electrode material and preparation method thereof for lithium-ion batteries," filed with the China Patent Office on December 16, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the field of negative electrode materials, and more particularly to a negative electrode material and a method for preparing the same, and a lithium ion battery. [Background technology]

[0003] Electric new energy vehicles are the future development direction of the automobile market, and their core component is the lithium-ion battery. As the market develops, the demand for high-density batteries is increasing, and the adoption of new high-specific-capacity positive and negative electrode materials is one of the important methods for increasing the energy density of batteries.

[0004] New materials, such as metals, oxides, and metal alloys, are being applied as active materials to anode materials, and various methods for improving battery energy density are being explored. Taking silicon-based anode materials as an example, silicon-based anode materials are one of the active materials mentioned above. They are generally considered to be next-generation anode materials due to their ultra-high theoretical capacity (4200 mAh / g), low lithium desorption potential (<0.5 V), and slightly higher voltage terraces than graphite, which reduces lithium deposition on the anode material surface during charging and provides excellent safety. However, silicon anodes experience a severe volume expansion effect during cycling, which can lead to pulverization and shattering of the anode material and rapid decline in battery cycle life.

[0005] Conventionally, a part of the oxygen in the silicon-oxygen material system is removed by a metal M, and the reduction product of the silicon-oxygen material is SiO x , Si, and M silicides in that order. The formation of some M silicides will release a large amount of heat, and the grain size of Si microcrystals will increase significantly, affecting the cycling performance and expansion coefficient of the material.

[0006] Therefore, how to suppress the volume expansion of the negative electrode material and improve the stability of the circulation is a current issue that needs to be resolved. Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, it is necessary to provide a composite negative electrode material that can improve the cycle performance of the battery, as well as its preparation method and application.

[0008] This application provides a negative electrode material and a preparation method thereof for a lithium ion battery, which can reduce the volume expansion of the negative electrode material and improve the rate performance and cycle stability of the negative electrode material. [Means for solving the problem]

[0009] According to a first aspect, the present application provides a negative electrode material comprising an active material, the active material comprising a silicon oxide and a compound of a metal M, the compound of the metal M comprising at least one of an oxide of the metal M and a silicate of the metal M, the metal M being selected from at least one metal having an electronegativity of <1.8; The amount of gas generated after mixing 10 g of the negative electrode material with 10 mL of hydrochloric acid having a concentration of 1 mol / L is ≦1 mL.

[0010] In some embodiments, the silicon oxide contains silicon and oxygen elements, and the atomic ratio of the silicon to the oxygen elements is 0 to 2, but does not include 0.

[0011] In some embodiments, the chemical formula of the silicon oxide is SiO x and 0 <x≦2である。

[0012] In some embodiments, the metal M is at least one selected from Li, K, Na, Mg, Ca, Al, La, Zn, Ti, and Mn.

[0013] In some embodiments, the metal M is Mg.

[0014] In some embodiments, the silicon oxide contains Si crystallites, and the size of the Si crystallites satisfies ≦20 nm.

[0015] In some embodiments, the negative electrode material has a pH of 8-14.

[0016] In some embodiments, the specific surface area of ​​the negative electrode material is ≦30 m 2 / g.

[0017] In some embodiments, the median diameter of the negative electrode material is 1 μm to 20 μm.

[0018] In some embodiments, the Wadell sphericity Φ of the negative electrode material satisfies 0.3<Φ<1.

[0019] In some embodiments, X-ray diffraction analysis reveals that the negative electrode material has characteristic peak A, characteristic peak B, and / or characteristic peak C, wherein characteristic peak A represents a Si characteristic peak or a SiO characteristic peak, characteristic peak B represents a characteristic peak of an oxide of metal M, characteristic peak C represents a characteristic peak of a silicate of metal M, and characteristic peak D represents a characteristic peak of a silicide of metal M. When the peak height ratio of the strongest peak of characteristic peak D to the strongest peak of characteristic peak A is I, 0≦I<0.05 is satisfied.

[0020] According to a second aspect, the present application provides a negative electrode material comprising an active material, the active material comprising a silicon oxide and a compound of a metal M, the compound of the metal M comprising at least one of an oxide of the metal M and a silicate of the metal M, the metal M being selected from at least one metal having an electronegativity of <1.8; X-ray diffraction analysis shows that the negative electrode material has characteristic peak A, characteristic peak B, and / or characteristic peak C, where characteristic peak A is a Si characteristic peak or a SiO characteristic peak, characteristic peak B is a characteristic peak of an oxide of metal M, characteristic peak C is a characteristic peak of a silicate of metal M, and the characteristic peak of a silicide of metal M is characteristic peak D. When the peak height ratio of the strongest peak of characteristic peak D to the strongest peak of characteristic peak A is I, the relationship 0≦I<0.05 is satisfied.

[0021] In some embodiments, the silicon oxide contains silicon and oxygen elements, and the atomic ratio of the silicon to the oxygen elements is 0 to 2, but does not include 0.

[0022] In some embodiments, the chemical formula of the silicon oxide is SiO x and 0 <x≦2である。

[0023] In some embodiments, the metal M is at least one selected from Li, K, Na, Mg, Ca, Al, La, Zn, Ti, and Mn.

[0024] In some embodiments, the metal M is Mg.

[0025] In some embodiments, the silicon oxide comprises Si crystallites, and the size of the Si crystallites satisfies ≦20 nm.

[0026] In some embodiments, the negative electrode material has a pH of 8-14.

[0027] In some embodiments, the specific surface area of ​​the negative electrode material is ≦30 m 2 / g.

[0028] In some embodiments, the median diameter of the negative electrode material is 1 μm to 20 μm.

[0029] In some embodiments, the Wadell sphericity Φ of the negative electrode material satisfies 0.3<Φ<1.

[0030] In some embodiments, the negative electrode material further comprises a carbon material on at least a portion of the surface of the active material.

[0031] In some embodiments, the negative electrode material further includes a carbon material layer on at least a portion of the surface of the active material, and the carbon material layer has a thickness of 10 nm to 500 nm.

[0032] In some embodiments, the mass content of carbon element in the negative electrode material is 1% to 40%.

[0033] In some embodiments, the negative electrode material has a porosity of <20%.

[0034] In some embodiments, the specific heat capacity of the negative electrode material is 0.2 J / (gK) to 2.0 J / (gK).

[0035] In some embodiments, the negative electrode material has pores, and the volume ratio of all micropores with a pore diameter of less than 2 nm to the total pore volume is 1% to 5%.

[0036] According to a third aspect, the present application provides a method for preparing a negative electrode material comprising an active material, A step of subjecting a mixture containing a metal M raw material and a silicon oxide raw material to a heat treatment under reduced pressure to form a vapor of the metal M and a vapor of the silicon oxide raw material, and thoroughly mixing the vapors for 1 minute to 600 minutes; and cooling the mixed vapor gas to obtain an active material, wherein the metal M is at least one metal selected from metals having an electronegativity of less than 1.8, and the active material includes silicon oxide and a compound of the metal M, and the compound of the metal M includes at least one of an oxide of the metal M and a silicate of the metal M.

[0037] In some embodiments, the metal M raw material is at least one selected from an elemental metal and a metal oxide.

[0038] In some embodiments, the metal M is at least one selected from Li, K, Na, Mg, Ca, Al, La, Zn, Ti, and Mn.

[0039] In some embodiments, the silicon oxide raw material is a mixture of Si and SiO y and SiO2, a mixture of SiO y and Si (0 < y < 2), or a mixture of Si and SiO2, and includes at least one of them.

[0040] In some embodiments, the molar amount of metal M in the raw material of metal M is denoted as n M and the molar amount of Si in the silicon raw material is denoted as n Si and n M :n Si =(0.2~1):1.

[0041] In some embodiments, the silicon oxide contains silicon and oxygen elements, and the atomic ratio of silicon to oxygen elements is 0 to 2, excluding 0.

[0042] In some embodiments, the chemical formula of the silicon oxide is SiO x where 0 < x ≦ 2.

[0043] In some examples, the temperature of the vacuum heat treatment is 900°C to 2000°C.

[0044] In some examples, the gas pressure of the vacuum heat treatment is 0.1 Pa to 1000 Pa.

[0045] In some examples, the temperature of the cooling treatment is 500°C to 900°C.

[0046] In some examples, the gas pressure of the vacuum heat treatment is 0.1 Pa to 1000 Pa.

[0047] In some embodiments, steps (1) and (2) are repeated to control the total incubation time to 1 hour to 120 hours.

[0048] In some embodiments, the active material obtained by the cooling treatment is subjected to a carbon coating treatment to obtain a negative electrode material, and the carbon coating treatment is at least one of solid-phase carbon coating, liquid-phase carbon coating, and vapor-phase carbon coating.

[0049] In some embodiments, the carbon coating step includes heating the active material obtained by the cooling treatment, followed by passing a protective gas and a carbon source gas through the active material, and thermally decomposing the carbon source gas to obtain a negative electrode material.

[0050] In some embodiments, the carbon source gas comprises hydrocarbons.

[0051] In some embodiments, the carbon source gas comprises at least one of methane, ethylene, acetylene, propyne, propylene, propane, toluene, benzene, styrene, and phenol.

[0052] In some embodiments, the pyrolysis temperature is 600° C. to 1000° C., and the pyrolysis time is 30 minutes to 24 hours.

[0053] In some embodiments, the carbon coating step includes carbonizing a mixture of the active material obtained by the cooling treatment and a solid-phase carbon source to obtain a negative electrode material.

[0054] In some embodiments, the carbonization temperature is 500° C. to 1000° C., and the carbonization time is 30 minutes to 24 hours.

[0055] In some embodiments, the solid phase carbon source comprises at least one of sugars, esters, hydrocarbons, organic acids, and high molecular weight polymers.

[0056] In some embodiments, the solid phase carbon source comprises at least one of polyvinyl chloride, polyvinyl butyral, polyacrylonitrile, polyacrylic acid, polyethylene glycol, polypyrrole, polyaniline, sucrose, glucose, maltose, citric acid, pitch, furfural resin, epoxy resin, and phenolic resin.

[0057] In some embodiments, the mass ratio of the solid-phase carbon source to the active material is 5:(5 to 95).

[0058] According to a fourth aspect, the present application provides a battery comprising an anode material according to the first and / or second aspect, or an anode material prepared according to the third aspect. [Effects of the Invention]

[0059] The technical solution of the present application has at least the following advantages:

[0060] First, the active material for the negative electrode material according to the present application comprises silicon oxide and a compound of metal M, and the compound of metal M is dispersed and distributed throughout the silicon oxide. Furthermore, the amount of gas generated after mixing the negative electrode material with hydrochloric acid is ≦1 mL, and the compound of metal M includes an oxide of metal M and / or a silicate of metal M. Furthermore, M silicide is hardly present, allowing for effective control of the size of Si crystallites in the silicon oxide. The compound of metal M is dispersed and distributed throughout the silicon oxide; that is, the compound of metal M may be embedded on silicon oxide particles. Alternatively, the compound of metal M may be embedded between silicon oxide particles, thereby improving the rate performance and cycle stability of the negative electrode material.

[0061] The method for preparing an anode material according to the present application involves preparing a mixture of silicon oxide raw material and metal M raw material, heat-treating the mixture at a high temperature under reduced pressure to form M vapor and silica oxide raw material vapor, and thoroughly mixing the vapors to reduce the local excess of M vapor and prevent some of the silicon oxide raw material vapor from being reduced to elemental silicon and silicide of metal M. The mixture is then cooled to obtain a mixture of silicon oxide and a compound of metal M. However, since the compound of metal M is dispersed and distributed throughout the silicon oxide and may be intercalated on or between silicon oxide particles, with most of the compound of metal M not existing as a silicide, the size of the Si crystallites in the silicon oxide can be effectively controlled, which is advantageous for controlling the expansion coefficient of the anode material and for obtaining an anode material with a low expansion coefficient and excellent cycleability. [Brief explanation of the drawings]

[0062] [Figure 1] 1 is a schematic flowchart of a method for producing a negative electrode material according to an embodiment of the present application. [Figure 2] FIG. 10 is a diagram showing a test state of the amount of gas generated from the negative electrode material according to the example of the present application. [Figure 3] 1 is an XRD spectrum of silicon in the negative electrode material prepared in Example 1 of the present application. [Figure 4] 1 is an XRD spectrum of MgSiO3 in the negative electrode material prepared in Example 1 of the present application. [Figure 5] 1 is an XRD spectrum of Mg2SiO4 in the negative electrode material prepared in Example 1 of the present application. [Figure 6] 1 is a graph showing the specific heat capacity of the negative electrode materials prepared in the examples of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0063] The following describes preferred embodiments of the present application, and it is pointed out that those skilled in the art can make some improvements and refinements without departing from the principles of the present application, and these improvements and refinements are also considered to be within the scope of the present application.

[0064] Conventionally, a part of the oxygen in the silicon-oxygen material system is removed by metal M, and the reduction product of the silicon-oxygen material is SiO x The order of M silicides is Si, M, and M. The formation of some M silicides releases a large amount of heat, significantly increasing the grain size of the Si crystallites. Furthermore, the presence of a large amount of M silicide in the anode material is thought to result in a large amount of free elemental silicon in the anode material, which can lead to the generation of large amounts of gas when the electrolyte comes into contact with the anode material. The large grain size of the Si crystallites causes excessive localized expansion stress in the anode material, making it prone to particle rupture and shattering, which affects the material's cycle performance and expansion rate. Conventionally, M silicides can be removed from the material by pickling, but this process does not change the size of the Si crystallites, and the pickling process is prone to fire, raising safety concerns. SiO2, a sintered product of M silicide, can be mixed into the anode material, reducing the specific capacity of the anode material. Controlling the M silicide content in the anode material by pickling requires twice the effort to achieve half the results, which is time-consuming and increases production costs.

[0065] The present application provides a negative electrode material comprising an active material, the active material comprising a silicon oxide and a compound of a metal M, the compound of the metal M comprising at least one of an oxide of the metal M and a silicate of the metal M, the metal M being selected from at least one metal having an electronegativity of <1.8; The amount of gas generated after mixing 10 g of the negative electrode material with 10 mL of 1 mol / L hydrochloric acid was ≦1 mL.

[0066] In the above technical solution, the active material of the negative electrode material consists of silicon oxide and a compound of metal M, and the compound of metal M is dispersedly distributed in the silicon oxide. Also, the gas generation amount after mixing the negative electrode material and hydrochloric acid is ≤ 1 mL, and the compound of metal M includes metal M oxide and / or metal M silicate. Also, there is almost no existence as M silicide, and the size of Si microcrystals in the silicon oxide can be effectively controlled. The compound of metal M is dispersedly distributed in the silicon oxide, that is, the compound of metal M may be embedded on the silicon oxide particles. Or, it is embedded between the silicon oxide particles, and the rate performance and cycle stability of the negative electrode material can be enhanced.

[0067] In some embodiments, the silicon oxide contains silicon and oxygen elements, and the atomic ratio of silicon to oxygen elements is 0 to 2, excluding 0. Specifically, the atomic ratio of silicon element to oxygen element may be 0.05, 0.11, 0.21, 0.26, 0.31, 0.41, 0.51, 0.59, 0.61, 0.69, 0.71, 0.74, 0.76, 0.79, 0.89, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, etc., and is not limited thereto. Preferably, the atomic ratio of silicon element to oxygen element is 0 to 1, excluding 0.

[0068] In some embodiments, the chemical formula of the silicon oxide is SiOx, where 0 < x ≤ 2, and x may specifically be 0.05, 0.11, 0.21, 0.26, 0.31, 0.41, 0.51, 0.59, 0.61, 0.69, 0.71, 0.74, 0.76, 0.79, 0.89, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2, etc., and is not limited here. Preferably, 0 < x < 1.

[0069] In some embodiments, metal M is at least one selected from Li, K, Na, Mg, Ca, Al, La, Zn, Ti, and Mn.

[0070] In some embodiments, the element distribution spectrum obtained by X-ray scanning of the SEM cross section of particles of the negative electrode material shows a uniform distribution of Si, O, and metal M. The uniform distribution of Si, O, and metal M within the particles of the negative electrode material effectively reduces the loss of active components due to the infiltration of components such as air into the primary particles, preventing deterioration of the structure and properties during long-term storage, making the material highly suitable for use in lithium-ion batteries. The main advantage of uniform distribution is that it ensures that the physicochemical states (i.e., silicate concentration, silicon crystal size, etc.) throughout the material are similar, ensuring that expansion and contraction are at the same level throughout the lithium ion absorption and desorption process, eliminating stress weaknesses caused by excessive local expansion and improving material performance.

[0071] In some embodiments, the metal M is magnesium, and compounds of the metal M include MgO, MgSiO, and MgSiO. When the metal M is magnesium, the size of the Si crystallites can be further reduced, reducing the bulging of the negative electrode material.

[0072] In some embodiments, the silicate of metal M is uniformly distributed within the primary particles of the active material.

[0073] In some embodiments, the silicate of metal M is a lithium silicate, which includes at least one of Li2SiO3, Li4SiO4, Li2Si2O5, and Li2Si3O7. Preferably, the lithium silicate is Li2Si2O5.

[0074] In some embodiments, X-ray diffraction analysis reveals that the negative electrode material has characteristic peak A, characteristic peak B, and / or characteristic peak C, where characteristic peak A is a Si characteristic peak (based on PDF Card No. 27-1402) or a SiO characteristic peak (based on PDF Card No. 30-1127), characteristic peak B is a characteristic peak of an oxide of metal M, and characteristic peak C is a characteristic peak of a silicate of metal M. The characteristic peak of a silicide of metal M is designated as characteristic peak D, and the peak height ratio I of the strongest peak of characteristic peak D to the strongest peak of characteristic peak A is 0≦I<0.05.

[0075] Specifically, the peak height ratio I may be 0.04, 0.03, 0.02, 0.01, 0.005, 0, etc., and preferably 0≦I<0.01. When the peak height ratio I is 0, it was confirmed that no silicide of metal M was present in the negative electrode material.

[0076] In some embodiments, the compound of metal M comprises an oxide of metal M, and the oxide of metal M is uniformly distributed within the negative electrode material particles.

[0077] In some embodiments, the silicon oxide contains Si crystallites, and the size of the Si crystallites is ≦20 nm. Specifically, the size of the Si crystallites in the silicon oxide may be 20 nm, 18 nm, 15 nm, 12 nm, 10 nm, 9.2 nm, 8 nm, 6.7 nm, 6 nm, 5 nm, or 3 nm, but is not limited to the listed values. Other values ​​within the range are also applicable. The size of the Si crystallites reflects the degree of disproportionation of the silicon oxide. The larger the size of the Si crystallites, the higher the degree of disproportionation. The silicon oxide raw material reacts to produce large amounts of Si crystal particles and SiO2, resulting in problems such as a larger volume expansion due to the Si element and a decrease in capacity due to the loss of SiO2 capacity, which is detrimental to the excellent performance of the silicon material itself.

[0078] In some embodiments, silicon oxide contains Si crystallites, and the size of the Si crystallites is ≦10 nm, which explains the small volume of the Si crystal grains in the anode. The Si crystallites are dispersed in the silicon oxide, and do not interact with the metal M compound to release a large amount of heat, which does not affect the size of the Si crystallites. This effectively reduces the expansion of the anode material and improves cycle performance.

[0079] In some embodiments, the pH of the negative electrode material is 8 to 14, and specifically, but not limited to, 8, 9, 10, 10.5, 11, 11.5, 12, 13, or 14. The pH of the negative electrode material is preferably 9 to 11.

[0080] In some embodiments, the specific surface area of ​​the negative electrode material is 30 m 2 / g, specifically, less than 1.0m 2 / g, 1.5m 2 / g, 1.8m 2 / g, 2.0m 2 / g, 2.5m 2 / g, 3.0m 2 / g, 3.6m 2 / g, 4.0m 2 / g, 5m 2 / g, 5.5m 2 / g, 6.0m 2 / g, 7.0m 2 / g, 8.0m 2 / g, 8.5m 2 / g, 10.0m 2 / g, 12.0m 2 / g, 15.0m 2 / g, 18.0m 2 / g, or 30.0m 2 / g, but is not limited to the exemplified values, and other values ​​not listed within the range are also applicable. The specific surface area of ​​the negative electrode material is 10 m 2 It is preferable that the SiO2 content is less than 1 / g.

[0081] In some embodiments, the median diameter of the negative electrode material is 1 μm to 20 μm, and specifically may be, but is not limited to, 1 μm, 2 μm, 2.5 μm, 3.5 μm, 4 μm, 6 μm, 8 μm, 9.5 μm, 10 μm, 12.5 μm, 15 μm, or 20 μm.

[0082] In some embodiments, the Wadell sphericity Φ of the negative electrode material is 0.3<Φ<1, and the Wadell sphericity may be 0.325, 0.43, 0.54, 0.65, 0.76, 0.87, 0.98, 0.99, etc. It is understood that the Wadell sphericity of the negative electrode material particles is not limited to the exemplified numerical values, and other unspecified numerical values ​​within the numerical range also apply.

[0083] In some embodiments, the negative electrode material further comprises a carbon material on at least a portion of the surface of the active material.

[0084] In some embodiments, the negative electrode material further comprises a carbon material layer on at least a portion of the surface of the active material. It is understood that the carbon material layer on the surface of the active material can reduce material particle fracture due to repeated SEI film formation, thereby improving the cycle performance of the negative electrode material and reducing volume expansion due to SEI film formation.

[0085] In some embodiments, the thickness of the carbon material layer is 10 nm to 500 nm, and more preferably 50 nm to 200 nm. Specifically, the thickness of the carbon material layer can be 10 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 200 nm, 300 nm, 400 nm, or 500 nm, but is not limited to the exemplified values ​​and other values ​​within the ranges not exemplified can also be applied.

[0086] In some embodiments, the active material is dispersed in a carbon material, and the carbon material forms a conductive network for the active material, thereby allowing the active material (e.g., silicon oxide, SiO x) has the drawback of poor conductivity, and is advantageous for utilizing the capacity of silicon oxide and stabilizing the cycle.

[0087] In some embodiments, the mass content of carbon element in the negative electrode material is 1% to 40%, and specifically may be, but is not limited to, 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 25%, 28%, 35%, or 40%, or may be other values ​​within the above range.

[0088] In some embodiments, the negative electrode material further comprises a coating layer located on the surface of the active material, and the coating layer may comprise a polymeric flexible polymer.

[0089] In some embodiments, the negative electrode material has pores, of which micropores with a pore size of less than 2 nm account for 1% to 5% of the total pore volume, specifically, but not limited to, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc. The presence of an appropriate amount of micropores can provide a buffer space for the volume expansion of the active material and reduce particle fracture due to excessive local stress.

[0090] In some embodiments, the porosity of the negative electrode material is less than 20%. A smaller porosity is advantageous for maintaining structural stability, utilizing the capacity of the negative electrode material, and maintaining cycle stability. Specifically, the porosity of the negative electrode material may be 19.2%, 18%, 15%, 13%, 10%, 8%, 5%, 3%, 2%, or the like. It is understood that the porosity of the negative electrode material is not limited to the recited values, and that other unrecited values ​​within this range also apply.

[0091] In some embodiments, the specific heat capacity of the negative electrode material is 0.2 to 2.0 J / (gK). It has been explained that a negative electrode material with a specific heat capacity that is too high or too low clearly indicates the presence of impurities. The specific heat capacity of the material can be adjusted by controlling the uniformity of the distribution of metal M compounds in the negative electrode material. When a certain amount of metal silicide is contained in the negative electrode material, the specific heat capacity of the negative electrode material increases, exceeding 2.0 J / (gK), or the content of elemental metal in the negative electrode material increases, resulting in a decrease in the specific heat capacity.

[0092] The present invention also provides a method for preparing a negative electrode material, which, as shown in FIG. 1, includes the following steps S100 to S200.

[0093] In step S100, a mixture containing a metal M raw material and a silicon oxide raw material is decompressed and heated to form M vapor and silicon oxide raw material vapor, and the vapors are thoroughly mixed for 1 minute to 600 minutes, where the metal M is at least one metal selected from metals with an electronegativity of less than 1.8.

[0094] In step S200, the mixed vapor gas is cooled to obtain an active material, which includes silicon oxide and a compound of metal M, and the compound of metal M includes at least one of an oxide of metal M and a silicate of metal M.

[0095] In the above technical solution, a mixture of a silicon oxide raw material and a metal M raw material is prepared, and is heat-treated under reduced pressure at a high temperature to form a vapor of M and a vapor of the silicon oxide raw material. By sufficiently mixing the vapors, the excess of the vapor of M is locally reduced, and the reduction of the vapor of some of the silicon oxide raw material to elemental silicon and the silicide of metal M is reduced. Then, it is cooled to obtain a mixture of a silicon oxide and a compound of metal M. However, the compound of metal M is dispersed and distributed in the silicon oxide, and the compound of metal M may be inserted on the silicon oxide particles, or may be inserted between the silicon oxide particles. Since the compound of metal M hardly exists as a silicide, it is advantageous for effectively controlling the size of the Si microcrystals in the silicon oxide and controlling the expansion rate of the negative electrode material, and is advantageous for obtaining a negative electrode material with a low expansion rate and excellent cycle performance.

[0096] The present technical solution will be specifically described below.

[0097] Step S100 is to subject a mixture containing a metal M raw material and a silicon oxide raw material to heat treatment under reduced pressure to form a vapor of M and a vapor of the silicon oxide raw material, and the vapors are sufficiently mixed for 1 min to 600 min. Here, the metal M is at least one selected from metals with an electronegativity < 1.8.

[0098] In some embodiments, the silicon oxide raw material is a mixture of Si and SiO y (0 < y < 2) and SiO2, a mixture of SiO y and Si, and a mixture of Si and SiO2, and contains at least one of them.

[0099] In some embodiments, the metal M raw material is at least one selected from elemental metals and metal oxides.

[0100] In some embodiments, the metal M is at least one selected from Li, K, Na, Mg, Ca, Al, La, Zn, Ti, and Mn. <​​In some embodiments, the molar amount of metal M in the metal M source is n M The molar amount of Si in the silicon oxide raw material is n Si Let n M :n Si ≦(0.2 to 1):1, and specifically may be 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, or other values ​​within the above range. By controlling the ratio of the molar amount of metal M to the molar amount of silicon, the silicate of metal M can be uniformly distributed within the primary particles of the active material.

[0102] In some embodiments, the heat treatment temperature is 900° C. to 2000° C. The heat treatment temperature may be specifically 900° C., 1000° C., 1100° C., 1200° C., 1400° C., 1500° C., 1550° C., 1575° C., 1600° C., 1650° C., 1700° C., 1800° C., 1900° C., or 2000° C. The temperatures are not limited to the exemplified values, and it is understood that other unspecified values ​​within the numerical ranges also apply.

[0103] In some embodiments, the reduced pressure heat treatment is carried out in a vacuum furnace, and the vacuum furnace is preheated to 900° C. to 2000° C. prior to the introduction of the mixture.

[0104] In some embodiments, the air pressure inside the vacuum furnace is 0.1 Pa to 1000 Pa, and specifically may be, but is not limited to, 0.1 Pa, 50 Pa, 100 Pa, 200 Pa, 500 Pa, 600 Pa, 700 Pa, 800 Pa, 900 Pa, or 1000 Pa.

[0105] In some embodiments, the mixture coevaporates under reduced pressure and heating to form M vapor and silica oxide raw material vapor. The valve at the furnace tube port of the vacuum furnace is then closed, and the vapor gas is maintained in the vacuum furnace for 1 to 600 min, specifically, but not limited to, 1, 5, 10, 30, 60, 90, 120, 150, 300, 360, 420, or 600 min. Vacuum furnaces are generally divided into a furnace tube and a cooling zone. In conventional techniques, after materials are heated in the furnace tube, the vapor formed immediately enters the cooling zone and cools. In the present application, the valve at the furnace tube port connects and closes the furnace tube to the cooling zone, and the valve at the furnace tube port is closed to maintain the vapor within the furnace tube, thereby maintaining the reaction raw materials in a vapor state. Furthermore, in a constantly high-pressure environment, the uniformity of the vapor after thorough mixing is significantly improved, allowing for more uniform mixing of the vapor gas. A holding time of 30 to 600 min is preferred.

[0106] In step S200, the mixed vapor gas is cooled to obtain an active material, which includes silicon oxide and a compound of metal M, and the compound of metal M includes at least one of an oxide of metal M and a silicate of metal M.

[0107] In some embodiments, the temperature of the cooling treatment is 500°C to 900°C, and specifically may be 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, or 900°C. The above temperatures are not limited to the exemplified values, and it is understood that other unspecified values ​​within the numerical ranges also apply.

[0108] In some embodiments, since the vapor gas is sufficiently mixed, local appearance of elemental metal, i.e., formation of elemental Si and metal silicide, is suppressed, and the active material obtained after cooling does not require conventional acid washing or water washing, and can be directly subjected to the subsequent carbon coating or secondary granulation process.

[0109] In some embodiments, the cooling process is performed in a cooling area of ​​a vacuum furnace, and the air pressure in the cooling area is 0.1 Pa to 1000 Pa, specifically, 0.1 Pa, 50 Pa, 100 Pa, 200 Pa, 500 Pa, 600 Pa, 700 Pa, 800 Pa, 900 Pa, or 1000 Pa, etc., but is not limited thereto.

[0110] In some embodiments, steps S100 to S200 are repeated to sufficiently evaporate the silicon oxide raw material and the metal M raw material to form a mixed vapor gas, which is then cooled and the formed compound of metal M is dispersed and distributed throughout the silicon oxide.

[0111] In some embodiments, steps (1) and (2) are repeated to control the total incubation time to 1 to 120 hours, specifically, 1, 5, 10, 15, 20, 30, 40, 50, 60, 120 hours, etc., but of course other values ​​within the above range are also acceptable. Repeating steps S100 to S200 is advantageous for forming a more uniformly dispersed negative electrode material and can also suppress the formation of elemental Si and metal silicides.

[0112] In some embodiments, the silicon oxide comprises silicon and oxygen, and the atomic ratio of silicon to oxygen is 0 to 2, not including 0. Specific examples of the atomic ratio of silicon to oxygen include, but are not limited to, 0.05, 0.11, 0.21, 0.26, 0.31, 0.41, 0.51, 0.59, 0.61, 0.69, 0.71, 0.74, 0.76, 0.79, 0.89, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2. Preferably, the atomic ratio of silicon to oxygen is 0 to 1, not including 0.

[0113] In some embodiments, the chemical formula of the silicon oxide is SiOx, where 0 < x ≤ 2, and x may specifically be, for example, 0.05, 0.11, 0.21, 0.26, 0.31, 0.41, 0.51, 0.59, 0.61, 0.69, 0.71, 0.74, 0.76, 0.79, 0.89, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2, etc., and is not limited herein. Preferably, 0 < x < 1.

[0114] The preparation method of the negative electrode material in other embodiments includes step S300 of carbon coating the active material obtained by the cooling treatment to obtain the negative electrode material.

[0115] Therefore, the active material obtained by the cooling treatment can be prepared in steps S100 to S200.

[0116] The negative electrode material includes an active material and a carbon material on at least a part of the surface of the active material. The active material is composed of a silicon oxide and a compound of metal M, and the chemical formula of the silicon oxide is SiO x , where 0 < x ≤ 2.

[0117] In one embodiment, the carbon coating treatment is specifically at least one of solid-phase carbon coating, liquid-phase carbon coating, and gas-phase carbon coating.

[0118] Specifically, the steps of the carbon coating treatment specifically include heating the active material obtained by the cooling treatment, and then passing a protective gas and a carbon source gas, and the carbon source gas thermally decomposes to obtain the negative electrode material.

[0119] In some embodiments, the carbon source gas used for the gas-phase carbon coating contains hydrocarbons.

[0120] In some embodiments, the carbon source gas includes at least one of methane, acetylene, ethylene, ethane, propane, propylene, propyne, acetone, and benzene.

[0121] In some embodiments, the chemical vapor deposition apparatus includes at least one of a rotary chemical vapor deposition reactor, a plasma-enhanced chemical vapor deposition reactor, a chemical vapor deposition tube furnace, and a fluidized bed. The chemical vapor deposition apparatus is specifically at least one of a rotary kiln and a box furnace.

[0122] In some embodiments, the pyrolysis temperature is 600° C. to 1000° C., and the pyrolysis time is 30 minutes to 24 hours.

[0123] In some embodiments, the protective gas is passed through the carbon source gas.

[0124] In some embodiments, the protective gas comprises at least one of nitrogen, helium, neon, argon, krypton, and xenon.

[0125] In some embodiments, the carbon coating step specifically includes carbonizing a mixture of the active material obtained by the cooling treatment and a solid-phase carbon source to obtain a negative electrode material.

[0126] In some embodiments, the solid-phase carbon source comprises at least one of sugars, esters, hydrocarbons, organic acids, and polymers, such as polyvinyl chloride, polyvinyl butyral, polyacrylonitrile, polyacrylic acid, polyethylene glycol, polypyrrole, polyaniline, sucrose, glucose, maltose, citric acid, pitch, furfural resin, epoxy resin, and phenolic resin.

[0127] In some embodiments, the cooled product may be mixed with a carbon source by VC mixing, fusion, ball milling, three-dimensional mixing, fluidized bed mixing, or the like.

[0128] In some embodiments, the mixing is performed in a fusion machine, the fusion time is 0.5 h-2 h, and the rotation speed of the fusion machine is 500 r / min-5000 r / min.

[0129] In some embodiments, the mass ratio of the solid phase carbon source to the active material is 5:(5 to 95).

[0130] In some embodiments, the carbonization temperature is 500° C. to 1000° C., and the carbonization time is 2 hours to 20 hours.

[0131] In some embodiments, the equipment used for solid state carbon coating is at least one of a rotary kiln, a box furnace, a roller hearth kiln, a tunnel kiln, and a pusher kiln.

[0132] In some embodiments, the protective gas may be at least one of nitrogen, argon, helium, neon, krypton, and xenon. Specifically, the liquid-phase carbon coating process involves uniformly mixing the cooled product with a carbon source, placing it in a furnace and passing a protective gas through it, and then heat-treating it to decompose the carbon source, which is then coated on the surface of the cooled product.

[0133] In some embodiments, the carbon source used in the liquid phase carbon coating may be an organic carbon source, such as low temperature liquid phase pitch, furfuryl alcohol, glycidyl methacrylate, triethylene glycol dimethacrylate, or the like.

[0134] In some embodiments, the protective gas may be at least one of nitrogen, argon, helium, neon, krypton, and xenon.

[0135] In some embodiments, the temperature of the heat treatment may be between 600°C and 1000°C. The preparation method further includes sieving and demagnetizing the carbonized material to obtain the negative electrode material.

[0136] In some embodiments, the sieving method is any one of a fixed sieve, a roll sieve, a resonating sieve, a roll sieve, a vibrating sieve, and a chain sieve, and the sieving mesh size is 100 to 500 mesh. Specifically, the sieving mesh size may be 100 mesh, 200 mesh, 250 mesh, 325 mesh, 400 mesh, 500 mesh, etc., but preferably the sieving mesh size is 250 mesh, which controls the particle size of the negative electrode material within the above range and contributes to improving the processing performance of the negative electrode material.

[0137] In some embodiments, the demagnetizing device is a permanent magnet cylindrical magnetic separator, an electromagnetic iron remover, or a pulsating high gradient magnetic separator, and the demagnetization is performed to ultimately control the content of magnetic materials in the negative electrode material, reduce the discharging effect of magnetic materials on the lithium ion battery, and ensure safety during battery use.

[0138] The present application also provides a battery using the negative electrode material provided by the above-mentioned examples or the negative electrode material manufactured by the method for preparing the negative electrode material provided by the above-mentioned examples. The battery may be, but is not limited to, a lithium-ion battery or a sodium-ion battery. The battery provided by the present application has the advantages of excellent rate performance and low expansion.

[0139] Measurement method: 1) Particle size of the negative electrode material The particle size measurement method is based on the Chinese standard GB / T 19077-2016. Measurement can be easily performed using a laser particle size analyzer (e.g., the Mastersizer 3000 laser particle size analyzer manufactured by Malvern Panalytical, UK).

[0140] 2) Method for measuring the specific surface area of ​​negative electrode materials After measuring the amount of gas adsorbed onto the solid surface at different relative pressures at a constant low temperature, the amount of adsorption of the monolayer of the sample is calculated based on the Brunauer-Emmett-Teller adsorption theory and its formula (BET formula), and the specific surface area of ​​the negative electrode material is calculated.

[0141] 3) pH test of negative electrode material Take 10 g of negative electrode material, add 10 g of water, and stir for 30 minutes. After that, take the clear liquid and measure the pH of the negative electrode material.

[0142] 4) Method for measuring the thickness of the carbon material layer The negative electrode material particles are cross-sectionally processed using an FIB-SEM device, and the average thickness of the carbon material layer is measured using the SEM.

[0143] 5) Method for measuring the porosity of negative electrode materials The porosity of the negative electrode material particles is measured by mercury intrusion porosimetry.

[0144] 6) Method for measuring the mass content of carbon element in negative electrode material The mass content of carbon element in the negative electrode material is measured by thermogravimetric analysis.

[0145] 7) Method for measuring the specific heat capacity of anode materials The specific heat capacity of the sample was tested using a DSC meter manufactured by Netzsch, Germany. The specific heat capacity value of the negative electrode material was tested at a test temperature of 0 to 130°C, a temperature rise rate of 10°C / min, an N2 atmosphere, and a sample amount of 13 mg.

[0146] 8) XRD measurement method for negative electrode materials The negative electrode material was cut into a sheet and tested using an X-ray diffraction analyzer. The angle range was 10-90°, the scanning mode was step scanning, the slit width was 1.0, the voltage was 40 kW, and the current was 40 mA. The measured data was analyzed using the Jade 6.5 software, and the components of the negative electrode material were confirmed by comparing them with the PDF card.

[0147] Characterization with an X-ray diffraction analyzer revealed characteristic peaks in the ranges of 27.5° to 29.5°, 46.3° to 48.3°, and 55.0° to 57.0°. The Si(111) peak at 28.6° was fitted, and the size of the Si crystallites was calculated from the resulting FWHM using the Scherrer equation.

[0148] After adding the anode material to a mixed acid solution of HCl and HNO3, the liquid phase is stirred, separated, and dried, and then X-ray diffraction analysis is performed using the method described above to check for impurity peaks other than the characteristic peaks of Si, SiO, and SiO2. If impurity peaks are present, repeat the acid treatment; if no impurity peaks are present, measure the oxygen content of the anode material using an oxygen, nitrogen, and hydrogen analyzer, and then obtain the value of x using the formula x = 28 * oxygen content / (16 - 16 * oxygen content).

[0149] 9) Method for measuring gas generation rate of negative electrode material As shown in Figure 2, 10 g of negative electrode material and 10 mL of 1 mol / L hydrochloric acid were sealed in each end of a two-compartment liquid packaging bag, and the volume V1 was measured using the drainage method.The middle partition of the packaging bag was then torn open, and the negative electrode material and hydrochloric acid were thoroughly mixed.Then, the mixture was left to stand at room temperature for 24 hours, and the volume V2 was measured again using the same method.The difference between V2 and V1 was taken as the amount of gas generated from the negative electrode material.

[0150] 10) Coin cell battery testing The prepared negative electrode material, conductive carbon black, and polyacrylic acid binder were dissolved and mixed in N-methylpyrrolidone in a mass ratio of 75:15:10, coated on a copper foil current collector, and vacuum dried to prepare a negative electrode tab. A metal lithium tab was used as the counter electrode, and a coin-type battery was assembled in an argon-filled glove box. A charge-discharge test was performed at a current density of 0.1 C over a charge-discharge range of 0.01 to 1.5 V.

[0151] 11) Electrochemical performance test The resulting negative electrode material was mixed with graphite in a 10:90 ratio to obtain the negative electrode active material. Furthermore, the negative electrode active material was mixed with sodium carboxymethylcellulose (CMC), a binder (styrene butadiene rubber SBR), and conductive agents Super-P and KS-6 in a 92:2:2:2 mass ratio to prepare a negative electrode slurry. The negative electrode slurry was applied to copper foil, vacuum dried, and roll-pressed to prepare a negative electrode tab. A ternary positive electrode tab (nickel cobalt manganese oxide lithium NCM523) prepared using a conventional process, 1 mol / L of LiPF6 / ethylene carbonate + dimethyl carbonate + ethyl methyl carbonate (v / v = 1:1:1) electrolyte, a separator (Cenoreguard 2400), and a housing were then used to assemble a CR2016 simulated battery using a conventional manufacturing process. For the cycle performance test, a constant current charge / discharge test was performed at a current of 30mA, with the charge / discharge voltage limited to 0-1.5V. The test was performed using a LAND battery test system manufactured by Wuhan Kinno Electronics Co., Ltd. The charge / discharge test was performed at a current density of 0.1C with a charge / discharge range of 0.005V-1.5V.

[0152] First coulomb efficiency = 1st cycle discharge capacity / 1st cycle charge capacity.

[0153] After 50 cycles, the thickness of the lithium-ion battery tab measured with a micrometer was defined as H1, and the expansion rate after 50 cycles was calculated as (H1-H0) / H0 x 100%.

[0154] After 100 cycles, the discharge capacity was recorded as the remaining capacity of the lithium-ion battery, and the capacity retention rate = remaining capacity / initial capacity * 100%.

[0155] The present application will be further described below by dividing it into several examples. Note that the present application is not limited to the specific examples below. Appropriate modifications can be made within the scope of the patent right.

[0156] Example 1 The method for preparing the negative electrode material is as follows: (1) 100 kg of Li ingot and 900 kg of SiO powder were mixed. Li:n Si Step of putting into a vacuum furnace at 1600 °C with a ratio of 0.2:1 (2) Step of closing the valve at the furnace nozzle, reducing the pressure of both the furnace tube and the cooling area to 1000 Pa, and holding the evaporated gas in the furnace for 60 min (3) Step of opening the valve at the furnace nozzle, venting the evaporated gas to the cooling area, and condensing it to SiOx (0 < x ≤ 2) at a temperature of 900 °C in the cooling area (4) Step of repeating steps (2) to (3) and maintaining the temperature for a total of 10 h to obtain the active material, and (5) Step of placing the active material in a high-temperature box furnace, venting methane gas under a nitrogen atmosphere, performing carbon coating treatment at 820 °C for 4 h, pulverizing the product, and sieving it to obtain the negative electrode material

[0157] <0(000591>The negative electrode material manufactured in this example includes an active material containing a compound of silicon oxide and metallic Li. The compound of metallic Li includes Li2O, Li2SiO3, and Li4SiO4. The specific surface area of the negative electrode material is 7.3 m 2 / g. As shown in FIGS. 3 to 5, through X-ray diffraction analysis, it was found that the negative electrode material has characteristic peaks corresponding to Si or SiO, Li2O peak, Li2SiO3 peak, and Li4SiO4 peak, the size of the microcrystalline grains of Si is 19.9 nm, and the pH is 11.9

[0158] The mass ratio of carbon element in the negative electrode material is 10%. As shown in FIG. 6, the specific heat capacity of the negative electrode material is​​​​​​​​​​​​​:n Si Step of charging into a vacuum furnace at 1600 °C with a ratio of 0.19:1 (2) Step of closing the valve at the furnace nozzle, reducing the gas pressure in both the furnace tube and the cooling area to 1000 Pa, and holding the evaporated gas in the furnace for 60 min (3) Step of opening the valve at the furnace nozzle, venting the evaporated gas to the cooling area, and condensing it to SiO x (0 < x ≤ 2) (4) Steps of repeating steps (2) to (3) and keeping the temperature for a total of 10 h to obtain the active material

[0161] The negative electrode material produced in this example includes an active material containing a silicon oxide and a compound of metal Al. The compound of metal Al includes Al2O3, Al2(SiO3)3, and Al4(SiO4)3. The specific surface area of the negative electrode material is 18.3 m 2 / g. It was found by X-ray diffraction analysis that the negative electrode material has characteristic peaks corresponding to Si or SiO, the size of the Si microcrystalline grains is 19.3 nm, and the pH is 8.4

[0162] The specific heat capacity of the negative electrode material is 0.2 - 2.0 J / (g·K), and the porosity of the negative electrode material is 2.3%. The negative electrode material has pores, and the volume ratio of the micropores with pore diameters < 2 nm to the total pore volume of all pores is 4.11%

[0163] The amount of gas generated after mixing 10 g of the negative electrode material with 10 mL of hydrochloric acid with a concentration of 1 mol / L is 0.7 mL

[0164] (Example 3) The method for preparing the negative electrode material is (1) Step of charging 100 kg of Mg ingot and 900 kg of SiO powder into a vacuum furnace at 1600 °C with a ratio of Mg :n Si = 0.73:1 (2) Step of closing the valve at the furnace nozzle, reducing the gas pressure in both the furnace tube and the cooling area to 1000 Pa, and holding the evaporated gas in the furnace for 60 min (3) Open the valve at the furnace nozzle, ventilate the evaporated gas to the cooling area, and condense it to SiOx (0 < x ≤ 2) at a temperature of 900 °C in the cooling area. (4) Repeat steps (2) to (3) and keep the temperature for a total of 10 h to obtain the active material. (5) Place the active material in a high-temperature box furnace, ventilate methane gas under a nitrogen atmosphere, perform carbon coating treatment at 950 °C for 4 h, pulverize and sieve the product to obtain the negative electrode material. The negative electrode material produced in this example comprises an active material containing silicon oxide and a compound of metal Mg. The compound of metal Mg includes MgO, MgSiO3, and Mg2SiO4. The specific surface area of the negative electrode material is 12.6 m 2 / g. Through X-ray diffraction analysis, it is found that the negative electrode material has characteristic peaks corresponding to Si or SiO, MgO peak, MgSiO3 peak, and Mg2SiO4 peak. The size of the Si microcrystalline grains is 15.1 nm, and the pH is 11.2.

[0165] The mass ratio of carbon element in the negative electrode material is 10%. The specific heat capacity of the negative electrode material is 0.2 - 2.0 J / (g·K), and the porosity of the negative electrode material is 2.0%. The negative electrode material has pores, and the volume ratio of micropores with pore diameters < 2 nm in the total pore volume of all pores is 3.23%.

[0166] The amount of gas generated after mixing 10 g of the negative electrode material with 10 mL of hydrochloric acid with a concentration of 1 mol / L is 0.9 mL.

[0167] (Example 4) The difference from Example 3 is that the temperature of the vacuum furnace is 2000 °C and the pressure is 100 Pa.

[0168] The negative electrode material produced in this example comprises an active material containing silicon oxide and a compound of metal Mg. The compound of metal Mg includes MgO, MgSiO3, and Mg2SiO4. The specific surface area of the negative electrode material is 15.5 m 2 / g, and X-ray diffraction analysis revealed that the negative electrode material had characteristic peaks corresponding to Si or SiO, as well as MgO peaks, MgSiO3 peaks, and Mg2SiO4 peaks, the size of the Si crystallites was 9.9 nm, and the pH was 10.8.

[0169] The mass ratio of carbon element in the negative electrode material is 10%, the specific heat capacity of the negative electrode material is 0.2 to 2.0 J / (gK), and the porosity of the negative electrode material is 3.5%. The negative electrode material has pores, and the volume ratio of micropores with a pore diameter of less than 2 nm to the total pore volume of all pores is 1.34%.

[0170] The amount of gas generated after mixing 10 g of the negative electrode material with 10 mL of hydrochloric acid having a concentration of 1 mol / L is 0.1 mL.

[0171] Example 5 The difference from Example 3 is that the temperature of the vacuum furnace is 900°C and the pressure is 10 Pa.

[0172] The negative electrode material prepared in this example has an active material containing silicon oxide and a compound of metallic Mg, and the compound of metallic Mg includes MgO, MgSiO3, and Mg2SiO4. The specific surface area of ​​the negative electrode material is 4.3 m 2 / g, and X-ray diffraction analysis revealed that the negative electrode material had characteristic peaks corresponding to Si or SiO, as well as MgO peaks, MgSiO3 peaks, and Mg2SiO4 peaks, the size of the Si crystallites was 6.5 nm, and the pH was 13.1.

[0173] The mass ratio of carbon element in the negative electrode material is 10%, the specific heat capacity of the negative electrode material is 0.2 to 2.0 J / (gK), and the porosity of the negative electrode material is 1.3%. The negative electrode material has pores, and the volume ratio of micropores with a pore diameter of less than 2 nm to the total pore volume of all pores is 1.40%.

[0174] The amount of gas generated after mixing 10 g of the negative electrode material with 10 mL of hydrochloric acid having a concentration of 1 mol / L is 0.1 mL.

[0175] Example 6 The difference from Example 3 is that the silicon oxide raw materials used are SiO2 and Si.

[0176] The negative electrode material prepared in this example has an active material containing silicon oxide and a compound of metallic Mg, and the compound of metallic Mg includes MgO, MgSiO3, and Mg2SiO4. The specific surface area of ​​the negative electrode material is 7.6 m 2 / g, and X-ray diffraction analysis revealed that the negative electrode material had characteristic peaks corresponding to Si or SiO, as well as MgO peaks, MgSiO3 peaks, and Mg2SiO4 peaks, the size of the Si crystallites was 19.1 nm, and the pH was 11.5.

[0177] The mass ratio of carbon element in the negative electrode material is 10%, the specific heat capacity of the negative electrode material is 0.2 to 2.0 J / (gK), and the porosity of the negative electrode material is 2.4%. The negative electrode material has pores, and the volume ratio of micropores with a pore diameter of less than 2 nm to the total pore volume of all pores is 2.95%.

[0178] The amount of gas generated after mixing 10 g of the negative electrode material with 10 mL of hydrochloric acid having a concentration of 1 mol / L is 0.7 mL.

[0179] Example 7 The difference from Example 3 is that the raw material of the metal M to be added is CaO and Si, n Ca :n Si =0.73:1.

[0180] The negative electrode material manufactured in this example has an active material containing silicon oxide and a compound of metallic Ca, and the compound of metallic Ca includes CaO, CaSiO3, and Ca2SiO4. The specific surface area of ​​the negative electrode material is 9.0 m 2 / g, and X-ray diffraction analysis revealed that the negative electrode material had characteristic peaks corresponding to Si or SiO, as well as CaO peaks, CaSiO3 peaks, and Ca2SiO4 peaks, the size of the Si crystallites was 15.5 nm, and the pH was 13.0.

[0181] The mass ratio of carbon element in the negative electrode material is 10%, the specific heat capacity of the negative electrode material is 0.2 to 2.0 J / (gK), and the porosity of the negative electrode material is 2.2%. The negative electrode material has pores, and the volume ratio of micropores with a pore diameter of less than 2 nm to the total pore volume of all pores is 4.01%.

[0182] The amount of gas generated after mixing 10 g of the negative electrode material with 10 mL of hydrochloric acid having a concentration of 1 mol / L is 0.7 mL.

[0183] Example 8 The difference from Example 1 is that the raw materials of the metal M to be added are MgO, CaO, and Si, n Mg+Ca :n Si =0.2:1.

[0184] The negative electrode material prepared in this example has active materials including silicon oxide, CaO, CaSiO3, Ca2SiO4, MgO, MgSiO3, and Mg2SiO4, and the specific surface area of ​​the negative electrode material is 9.8 m 2 / g, and X-ray diffraction analysis revealed that the negative electrode material had characteristic peaks corresponding to Si or SiO, CaO peak, CaSiO3 peak, Ca2SiO4 peak, MgO peak, MgSiO3 peak, and Mg2SiO4 peak, the size of the Si crystallites was 15.0 nm, and the pH was 12.7.

[0185] The mass ratio of carbon element in the negative electrode material is 10%, the specific heat capacity of the negative electrode material is 0.2 to 2.0 J / (gK), and the porosity of the negative electrode material is 2.7%. The negative electrode material has pores, and the volume ratio of micropores with a pore diameter of less than 2 nm to the total pore volume of all pores is 4.89%.

[0186] The amount of gas generated after mixing 10 g of the negative electrode material with 10 mL of hydrochloric acid having a concentration of 1 mol / L is 0.6 mL.

[0187] Example 9 The difference from Example 3 is that (2) the valve at the furnace tube port is closed, the gas pressure in both the furnace tube and the cooling area is reduced to 1000 Pa, and the evaporated gas is kept in the furnace for 600 minutes.

[0188] The negative electrode material prepared in this example has an active material containing silicon oxide and a compound of metallic Mg, and the compound of metallic Mg includes MgO, MgSiO3, and Mg2SiO4. The specific surface area of ​​the negative electrode material is 15.6 m 2 / g, and X-ray diffraction analysis revealed that the negative electrode material had characteristic peaks corresponding to Si or SiO, as well as MgO peaks, MgSiO3 peaks, and Mg2SiO4 peaks, the size of the Si crystallites was 17.0 nm, and the pH was 11.7.

[0189] The mass ratio of carbon element in the negative electrode material is 10%, the specific heat capacity of the negative electrode material is 0.2 to 2.0 J / (gK), and the porosity of the negative electrode material is 2.3%. The negative electrode material has pores, and the volume ratio of micropores with a pore diameter of less than 2 nm to the total pore volume of all pores is 2.49%.

[0190] The amount of gas generated after mixing 10 g of the negative electrode material with 10 mL of hydrochloric acid having a concentration of 1 mol / L is 0.3 mL.

[0191] Example 10 The difference from Example 3 is that (2) the valve at the furnace tube opening is closed, the gas pressure in both the furnace tube and the cooling area is reduced to 1000 Pa, and the evaporated gas is kept in the furnace for 1 minute.

[0192] The negative electrode material prepared in this example has an active material containing silicon oxide and a compound of metallic Mg, and the compound of metallic Mg includes MgO, MgSiO3, and Mg2SiO4. The specific surface area of ​​the negative electrode material is 11.3 m 2 / g, and X-ray diffraction analysis revealed that the negative electrode material had characteristic peaks corresponding to Si or SiO, as well as MgO peaks, MgSiO3 peaks, and Mg2SiO4 peaks, the size of the Si crystallites was 13.5 nm, and the pH was 10.9.

[0193] The mass ratio of carbon element in the negative electrode material is 10%, the specific heat capacity of the negative electrode material is 0.2 - 2.0 J / (g·K), and the porosity of the negative electrode material is 1.8%. The negative electrode material has pores, and the volume ratio of the micropores with pore diameter <2 nm in all the pores to the total pore volume of all the pores is 4.93%.

[0194] The amount of gas generated after mixing 10 g of the negative electrode material with 10 mL of hydrochloric acid with a concentration of 1 mol / L is 0.9 mL.

[0195] (Example 11) The preparation method of the negative electrode material is (1) The step of putting 100 kg of Mg ingot and 900 kg of SiO powder into a vacuum furnace at 1600 °C, (2) The step of reducing the gas pressure in both the furnace tube and the cooling area to 1000 Pa, venting the evaporated gas to the cooling area, and condensing SiO x (0 < x ≤ 2) to obtain an active material by reacting for a total of 10 h, and <00​​​​​​​​​​​​​​​​(1) Step of charging 100 kg of Mg ingot and 900 kg of SiO powder into a vacuum furnace at 1600 °C, (2) Both reduce the gas pressure in the furnace tube and the cooling area to 1000 Pa, ventilate the evaporated gas to the cooling area, and condense SiO x (0 < x ≤ 2), react for a total of 10 h to obtain an active material, and (3) Place the active material in a high-temperature box furnace, ventilate methane gas under a nitrogen atmosphere, perform carbon coating treatment at 950 °C for 4 h, pulverize and sieve the product to obtain a negative electrode material.

[0198] The specific surface area of the negative electrode material produced in this comparative example is 15.9 m 2 / g. Through X-ray diffraction analysis, it was found that the negative electrode material has characteristic peaks corresponding to Si or SiO, MgO peaks, MgSiO3 peaks, Mg2SiO4 peaks, and a small amount of Mg2Si peaks. The size of the Si microcrystalline grains is 25.6 nm, and the pH is 13.0. However, the ratio I of the peak height of the strongest peak of the Mg2Si peak to the strongest peak of the Si characteristic peak is 0.1.

[0199] Perform a performance test on the negative electrode materials obtained in the examples and comparative examples, and show the results of the above performance test in Table 1.

[0200]

Table 1

[0201] The data in Table 1 indicate that the negative electrode materials prepared in Examples 1 to 11 contain active material, but the test spectra do not show the characteristic peak of M silicide, indicating that the metal M compound in the active material does not contain metal M silicide. The gas generation volume of each negative electrode material was less than 1 mL. This is because a mixture of silicon oxide raw material and metal M raw material is prepared, and then subjected to high-temperature, reduced-pressure heating to form metal M vapor and silicon oxide raw material vapor. By thoroughly mixing the vapors, the local excess of M vapor is reduced, reducing the reduction of some of the silicon oxide raw material vapor to elemental silicon and metal M silicide. This effectively controls the size of Si crystallites in the silicon oxide, thereby improving the rate performance and cycle stability of the negative electrode material.

[0202] The negative electrode material of Example 2 was not subjected to carbon coating treatment, and the specific surface area of ​​the negative electrode material was large, which resulted in increased side reactions with the electrolyte during the cycling process of the negative electrode material, resulting in a slight decrease in the rate performance and cycle performance of the battery.

[0203] In Example 11, the M silicide was removed through a pickling process. However, the pickling process did not significantly reduce the large Si crystal grain size that had formed before the pickling process, resulting in a decrease in the cycle life of the material and an increase in the expansion coefficient. At the same time, the pickling process also increases the specific surface area due to the removal of materials, resulting in the formation of more irreversible Li4SiO4, Li2O, and SEI films during the initial lithium absorption, reducing both the initial capacity and the initial Coulombic efficiency. As can be seen from the specific heat capacity, if the specific heat capacity after pickling is below 0.2 J / (gK), the anode material contains low-specific heat capacity material. This low-specific heat capacity material is derived from localized elemental Si formed due to insufficient gas mixing during the evaporation process. This material is not removed during pickling, resulting in a decrease in the cycle life of the material and an increase in the expansion coefficient. Therefore, removing the M silicide formed during synthesis by pickling is far less effective than preventing the formation of M silicide by thoroughly mixing the gas during evaporation, as in the present invention.

[0204] In Comparative Example 1, during the manufacturing process, the evaporated gas was vented to a cooling area and condensed into silicon oxide. The evaporated gas was not mixed sufficiently, which led to the local formation of M silicide and the release of a large amount of heat, which significantly increased the size of the Si crystal grains, resulting in a decrease in the cycle performance of the negative electrode material and an increase in the expansion rate.

[0205] Although the present application is disclosed in preferred embodiments, it does not limit the scope of the claims, and a person skilled in the art can make some possible variations and modifications without departing from the concept of the present application, so the protection scope of the present application should be in accordance with the scope defined by the claims of the present application.

Claims

1. A negative electrode material comprising an active material including a compound of silicon oxide and a metal M, the compound of metal M includes at least one of an oxide of metal M and a silicate of metal M; The metal M is selected from at least one metal having an electronegativity of <1.8; A negative electrode material characterized in that the amount of gas generated after mixing 10 g of the negative electrode material with 10 mL of hydrochloric acid having a concentration of 1 mol / L is ≦1 mL.

2. The silicon oxide contains silicon and oxygen elements, 2. The negative electrode material according to claim 1, wherein the atomic ratio of silicon to oxygen is 0 to 2, not including 0.

3. The chemical formula of the silicon oxide is SiO x 2. The negative electrode material according to claim 1, wherein x is 0<x≦2.

4. 4. The negative electrode material according to claim 1, further comprising at least one of the following characteristics (1) to (7): (1) The metal M is at least one selected from Li, K, Na, Mg, Ca, Al, La, Zn, Ti, and Mn. (2) The metal M is Mg. (3) The silicon oxide contains Si microcrystals, and the size of the Si microcrystals satisfies the condition of ≦20 nm. (4) The pH of the negative electrode material is 8 to 14. (5) The specific surface area of ​​the negative electrode material is ≦30 m 2 / g (6) The median diameter of the negative electrode material is 1 μm to 20 μm. (7) The Wadell sphericity Φ of the negative electrode material satisfies 0.3<Φ<1.

5. X-ray diffraction analysis reveals that the negative electrode material has at least one of characteristic peak A, characteristic peak B, and characteristic peak C; Feature peak A indicates a Si feature peak or a SiO feature peak, Characteristic peak B indicates a characteristic peak of an oxide of metal M, Characteristic peak C indicates a silicate characteristic peak of metal M, The characteristic peak of the silicide of the metal M is designated as characteristic peak D, 5. The negative electrode material according to claim 1, wherein I is the peak height ratio of the strongest peak of characteristic peak D to the strongest peak of characteristic peak A, and 0≦I<0.05 is satisfied.

6. A negative electrode material comprising an active material including a compound of silicon oxide and a metal M, the compound of metal M includes at least one of an oxide of metal M and a silicate of metal M; The metal M is selected from at least one metal having an electronegativity of <1.8; X-ray diffraction analysis reveals that the negative electrode material has at least one of characteristic peak A, characteristic peak B, and characteristic peak C; Characteristic peak A indicates a Si characteristic peak or a SiO characteristic peak, Characteristic peak B indicates a characteristic peak of an oxide of metal M, Characteristic peak C indicates a silicate characteristic peak of metal M, The characteristic peak of the silicide of the metal M is designated as characteristic peak D, A negative electrode material characterized in that, when the peak height ratio of the strongest peak of characteristic peak D to the strongest peak of characteristic peak A is I, 0≦I<0.05 is satisfied.

7. The silicon oxide contains silicon and oxygen elements, 7. The negative electrode material according to claim 6, wherein the atomic ratio of silicon to oxygen is 0 to 2, not including 0.

8. The chemical formula of the silicon oxide is SiO x 7. The negative electrode material according to claim 6, wherein x is 0<x≦2.

9. 9. The negative electrode material according to claim 6, wherein the negative electrode material comprises at least one of the following characteristics (1) to (7): (1) The metal M is at least one selected from Li, K, Na, Mg, Ca, Al, La, Zn, Ti, and Mn. (2) The metal M is Mg. (3) The silicon oxide contains Si microcrystals, and the size of the Si microcrystals satisfies the condition of ≦20 nm. (4) The pH of the negative electrode material is 8 to 14. (5) The specific surface area of ​​the negative electrode material is ≦30 m 2 / g (6) The median diameter of the negative electrode material is 1 μm to 20 μm. (7) The Wadell sphericity Φ of the negative electrode material satisfies 0.3<Φ<1.

10. 9. The negative electrode material according to claim 1, characterized in that it comprises at least one of the following characteristics (1) to (4): (1) The negative electrode material further contains a carbon material on at least a portion of the surface of the active material. (2) The negative electrode material further includes a carbon material layer on at least a portion of the surface of the active material, and the carbon material layer has a thickness of 10 nm to 500 nm. (3) The mass content of carbon element in the negative electrode material is 1% to 40%. (4) The porosity of the negative electrode material is less than 20%.

11. 11. The negative electrode material according to claim 1, wherein the specific heat capacity of the negative electrode material is 0.2 J / (g.K) to 2.0 J / (g.K).

12. the negative electrode material has pores, 12. The negative electrode material according to claim 1, wherein the volume ratio of micropores having a pore diameter of less than 2 nm to the total pore volume of all pores is 1% to 5%.

13. A step of subjecting a mixture containing a metal M raw material and a silicon oxide raw material to a reduced pressure heat treatment to form a vapor of the metal M and a vapor of the silicon oxide raw material, and thoroughly mixing the vapors for 1 minute to 600 minutes; cooling the mixed vapor to obtain an active material; The metal M is at least one metal selected from metals having an electronegativity of less than 1.8, the active material comprises a compound of silicon oxide and metal M; The method for preparing a negative electrode material, wherein the compound of metal M includes at least one of an oxide of metal M and a silicate of metal M.

14. The method for preparing a negative electrode material according to claim 13, characterized in that it comprises at least one of the following features (1) to (10): (1) The raw material of the metal M is at least one selected from the group consisting of a simple metal M and an oxide containing the metal M. (2) The metal M is at least one selected from Li, K, Na, Mg, Ca, Al, La, Zn, Ti, and Mn. (3) The silicon oxide raw material is Si and SiO y and SiO 2 a mixture of SiO y and Si mixtures, and Si and SiO 2 and a mixture of (4) The molar amount of metal M in the raw material of metal M is n M The molar amount of Si in the silicon oxide raw material is n Si Let n M :n Si = (0.2 to 1): 1 (5) The temperature of the reduced pressure heat treatment is 900°C to 2000°C. (6) The gas pressure in the reduced pressure heating treatment is 0.1 Pa to 1000 Pa. (7) The temperature of the cooling treatment is 500°C to 900°C. (8) The gas pressure in the reduced pressure heating treatment is 0.1 Pa to 1000 Pa. (9) The silicon oxide contains silicon and oxygen elements, and the atomic ratio of the silicon to the oxygen elements is 0 to 2, not including 0. (10) The chemical formula of the silicon oxide is SiO x and 0<x≦2

15. A battery comprising the negative electrode material according to any one of claims 1 to 12, or the negative electrode material prepared by the method for preparing the negative electrode material according to any one of claims 13 to 14.

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