Negative electrode material and preparation method therefor, and secondary battery

Abstract

The present application relates to the technical field of batteries, and in particular to a negative electrode material and a preparation method therefor, and a secondary battery. The negative electrode material comprises a silicon-based active material and a matrix material; the negative electrode material contains a hydrogen element, a halogen element, a nitrogen element and a sulfur element, wherein the mass content of the hydrogen element is mH, and the mass content of the halogen element is mX, the mass content of the sulfur element is mS, the mass content of the nitrogen element is mN, and the following relations are satisfied: 0.02≤mX / mH≤5.00, 0.02≤mN / mH≤20.00, and 0.05≤mS / mH≤5.00. The mass content ratios of the hydrogen element to the nitrogen element, the sulfur element and the halogen element are each adjusted to an appropriate range, so that the volume expansion of the negative electrode material can be effectively inhibited, and the capacity, the first coulombic efficiency, the powder electrical conductivity, the cycle performance and the rate performance of the negative electrode material are all improved.

Description

Negative electrode material and preparation method thereof, and secondary battery Technical Field

[0001] The present application relates to the field of battery technology, and in particular to negative electrode materials and preparation methods thereof, and secondary batteries. Background Art

[0002] In recent years, lithium-ion batteries have been widely used in electric vehicles and consumer electronics due to their advantages, including high energy density, high output power, long cycle life, and low environmental pollution. Anode materials are one of the most critical components of lithium-ion batteries, and their structure and performance directly affect the electrochemical performance of lithium-ion batteries. Silicon-based anode materials are one of the most critical anode materials for high-energy-density lithium-ion batteries. However, existing silicon-based anode materials suffer from large volume expansion and poor rate capability, which limits their widespread application in lithium batteries.

[0003] In order to improve the volume expansion of silicon-based materials, silicon materials are generally compounded with carbon materials. However, a simple carbon material coating layer is difficult to effectively isolate the interfacial side reactions between the electrolyte and the negative electrode material. In the process of preparing negative electrode slurry using silicon-based materials, gas production is serious, and the volume expansion phenomenon of the material during the charge and discharge cycle also affects the performance of the negative electrode material such as the cycle life.

[0004] Therefore, how to improve the contact interface between the negative electrode material and the electrolyte and alleviate the volume expansion of the negative electrode material is still a technical problem that needs to be solved.

[0005] Summary of the Invention

[0006] The present application provides a negative electrode material and a preparation method thereof, and a secondary battery, which are beneficial to improving the stability of the solid-liquid contact interface of the negative electrode material, alleviating the volume expansion of the negative electrode material, and improving the initial efficiency and cycle performance.

[0007] In a first aspect, the present invention provides a negative electrode material, including a silicon-based active material and a matrix material, wherein the negative electrode material contains hydrogen, halogen, nitrogen and sulfur, wherein the mass content of hydrogen is m H , the mass content of halogen elements is m X , the mass content of sulfur element is m S , the mass content of nitrogen is m N , and satisfy the following relationship: 0.02≤m X / m H ≤5.00,0.02≤m N / m H ≤20.00,0.05≤m S / m H ≤5.00.

[0008] In some embodiments, the matrix material is formed on at least a portion of the surface of the silicon-based active material.

[0009] In some embodiments, the silicon-based active material is formed on the surface of the base material.

[0010] In some embodiments, the silicon-based active material and the matrix material are dispersed with each other.

[0011] In some embodiments, the negative electrode material contains pores.

[0012] In some embodiments, in the pore volume distribution curve of the negative electrode material, the pore size is and There is a characteristic peak of pore volume in the range.

[0013] In some embodiments, in the negative electrode material, 50 mg / kg≤m X ≤1500mg / kg.

[0014] In some embodiments, in the negative electrode material, 100 mg / kg≤m N ≤4000mg / kg.

[0015] In some embodiments, in the negative electrode material, 10 mg / kg≤m S ≤200mg / kg.

[0016] In some embodiments, the silicon-based active material includes at least one of elemental silicon, silicon oxide, silicon alloy, and silicate.

[0017] In some embodiments, the silicon-based active material comprises silicon oxide, the general formula of which is SiO x , 0<x≤2.

[0018] In some embodiments, the silicon-based active material includes a doping metal M, where M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu, and Mn.

[0019] In some embodiments, the silicon-based active material includes a doped metal M, and the mass content of the metal M in the negative electrode material is 0 wt % to 15 wt %, excluding 0 wt %.

[0020] In some embodiments, the matrix material includes a carbon material, or a mixture of a carbon material and an inorganic oxide.

[0021] In some embodiments, the matrix material includes a carbon material, and the carbon material includes at least one of graphite, graphene, amorphous carbon, diamond-like carbon, carbon nanotubes, and carbon fibers.

[0022] In some embodiments, the matrix material includes a carbon material, and the carbon material is formed on at least a portion of the surface of the silicon-based active material to form a carbon layer, and the thickness of the carbon layer is 20 nm to 1000 nm.

[0023] In some embodiments, based on the mass of the negative electrode material, the mass content of carbon in the negative electrode material is 0.5 wt % to 15 wt %.

[0024] In some embodiments, the negative electrode material has a median particle size of 2.0 μm to 12.0 μm.

[0025] In some embodiments, the specific surface area of ​​the negative electrode material is 0.50 m 2 / g~10.00m 2 / g.

[0026] In some embodiments, the tap density of the negative electrode material is 0.75 g / cm 3 ~1.35g / cm 3 .

[0027] In some embodiments, the powder conductivity of the negative electrode material under a pressure of 20 kN is 0.01 S / cm to 100.00 S / cm.

[0028] In some embodiments, the mass content of water in the negative electrode material is 0.01 wt% to 0.80 wt%.

[0029] In some embodiments, the pH of the negative electrode material is 6.00 to 12.00.

[0030] In a second aspect, the present invention also provides a method for preparing a negative electrode material, comprising the following steps:

[0031] preparing a precursor, wherein the precursor includes a silicon-based active substance and a matrix material; and

[0032] In a modified gas source environment, the precursor is surface modified by plasma enhanced chemical vapor deposition to obtain a negative electrode material, wherein the modified gas source includes hydrogen, sulfur, nitrogen and halogen elements; in the negative electrode material, the mass content of hydrogen is m H , the mass content of halogen elements is m X , the mass content of sulfur element is m S , the mass content of nitrogen is m N, and satisfy the following relationship: 0.02≤m X / m H ≤5.00,0.02≤m N / m H ≤20.00,0.05≤m S / m H ≤5.00.

[0033] In a third aspect, an embodiment of the present application further provides a secondary battery, comprising the negative electrode material as described above, or comprising the negative electrode material prepared by the preparation method as described above.

[0034] Compared with the existing technology, the technical solution of this application has at least the following technical effects:

[0035] In the negative electrode material of the present application, by exploring the content relationship between hydrogen and nitrogen, sulfur and halogen elements, the mass content ratio of hydrogen to nitrogen, sulfur and halogen elements in the negative electrode material is regulated to an appropriate range, so that the powder conductivity, first effect and cycle performance of the material are comprehensively improved. In the present application, the negative electrode material also contains an appropriate amount of halogen and N and S elements. The appropriate amount of halogen elements can also participate in the formation of a more stable solid electrolyte membrane (SEI membrane) when the electrolyte contacts the negative electrode material, which can enhance the bonding strength between the negative electrode material and the solid electrolyte membrane, and is beneficial to maintaining the stability of the solid-liquid contact interface on the surface of the negative electrode material during the cyclic charge and discharge process. At the same time, it can better inhibit the expansion of the negative electrode material, and the nitrogen and sulfur elements are also beneficial to further improve the conductivity of the negative electrode material powder, thereby improving the rate performance of the negative electrode material. When the content relationship of hydrogen, nitrogen, sulfur, and halogen elements in the negative electrode material meets the above-mentioned ratio relationship of this application, the wettability of the negative electrode material with the electrolyte can be improved, solid-liquid control can be achieved during the slurry mixing process of the negative electrode material, the slurry dispersion can be improved, the slurry sedimentation or agglomeration can be reduced, and gas production during the slurry mixing process can be suppressed, which helps to maintain the stability of the slurry. Therefore, the negative electrode material provided by this application can have the advantages of high initial efficiency, high powder conductivity, high cycle stability, and low volume expansion rate.

[0036] The preparation method of the negative electrode material provided by the present application uses plasma enhanced chemical vapor deposition to surface modify the precursor of the silicon-based active material and the carbon material in a modified gas source environment, and efficiently and uniformly dopes multiple elements with high deposition efficiency and high controllability. After the surface modification treatment, the carbon material on the surface of the silicon-based active material can combine with hydrogen to form a carbon-hydrogen bond. The appropriate amount of carbon-hydrogen saturation helps to adjust the hydrophilicity of the material, thereby adjusting the hydrophilicity of the carbon material and adjusting the wettability of the electrolyte on the negative electrode material, so that the lithium ion conduction interface between the negative electrode material and the electrolyte is smoother, thereby improving the mass transfer / charge transfer efficiency of the negative electrode material, and thereby improving the low-temperature performance and powder conductivity of the negative electrode material. The incorporation of appropriate amounts of halogens, nitrogen, and sulfur can, on the one hand, regulate carbon-hydrogen saturation: halogens compete with hydrogen for saturation, and their presence will occupy the hydrogen site, thereby achieving regulation of carbon-hydrogen saturation. Nitrogen and sulfur may combine with hydrogen to form local functional groups such as amino groups, which also play a role in regulating carbon-hydrogen saturation. On the other hand, halogens can also participate in the formation of a more stable solid electrolyte membrane (SEI membrane) when the electrolyte contacts the negative electrode material, which can enhance the bonding strength between the negative electrode material and the solid electrolyte membrane. This helps maintain the stability of the solid-liquid contact interface on the surface of the negative electrode material during cyclic charge and discharge, while also better suppressing the expansion of the negative electrode material. Nitrogen and sulfur also help further improve the conductivity of the negative electrode material powder, thereby improving the rate performance of the negative electrode material. Therefore, modifying the surface of the negative electrode material by modifying the gas phase source can suppress the volume expansion of the negative electrode material and comprehensively improve the electrochemical properties of the negative electrode material, such as the first effect, powder conductivity, and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present application is further described below with reference to the accompanying drawings and examples.

[0038] FIG1 is an FTIR graph of the negative electrode material provided in an embodiment of the present application.

[0039] FIG2 is a schematic flow chart of a method for preparing a negative electrode material provided in an embodiment of the present application.

[0040] FIG3 is a schematic diagram illustrating a discharge state of a secondary battery according to an embodiment of the present application.

[0041] FIG4 is a schematic diagram of the pore volume distribution of the negative electrode material provided in Example 1 of the present application. DETAILED DESCRIPTION

[0042] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0043] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0044] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0045] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0046] Silicon-based anode materials are one of the most critical materials for high-energy-density lithium-ion batteries. However, existing silicon-based anode materials have problems such as large expansion and poor rate performance, which limit their widespread application in lithium-ion batteries.

[0047] In existing related research, most of the research focuses on the G and D peaks of the carbon layer structure on the surface of silicon-based negative electrode materials to improve the surface physical and chemical properties of silicon-based negative electrode materials. However, it is still difficult to comprehensively improve the volume expansion and electrochemical performance of silicon-based negative electrode materials.

[0048] To address the above-mentioned issues, in a first aspect, the present application provides a negative electrode material, comprising a silicon-based active material and a matrix material. The silicon-based active material may be formed on at least a portion of the surface of the matrix material, the matrix material may be located on the surface of the silicon-based active material, or the silicon-based active material and the matrix material may be dispersed in each other. In some embodiments, the matrix material may comprise a carbon material, or a mixture of a carbon material and an inorganic oxide.

[0049] The negative electrode material contains hydrogen, halogen, nitrogen and sulfur, among which the mass content of hydrogen is m H , the mass content of halogen elements is m X (When the negative electrode material includes multiple halogen elements, m X is the total mass content of multiple halogen elements), the mass content of sulfur is m S , the mass content of nitrogen is m N , and satisfy the following relationship: 0.02≤m X / m H ≤5.00,0.02≤m N / m H ≤20.00,0.05≤m S / m H ≤5.00. In negative electrode materials, hydrogen and halogen elements are mainly used as terminal elements of the matrix material, which can modify the interface and structure of the negative electrode material. Nitrogen and sulfur elements are mainly doped into the matrix material, which is beneficial to improving the electrochemical properties of the negative electrode material, such as rate performance, powder conductivity, and early cycle stability.

[0050] In some embodiments, m X / m H The value of can be 0.02, 0.05, 0.1, 0.5, 0.8, 1, 2, 3, 4 or 5, etc., and of course it can be other values ​​within the above range, which are not limited here. The presence of a suitable content of halogen elements helps to improve the electrical conductivity of the negative electrode material, and can participate in the formation of a solid electrolyte film (SEI film) on the surface of the negative electrode material, improve the stability of the SEI film, and thus inhibit the expansion of the negative electrode material and improve the cycle performance of the negative electrode material. Controlling the mass ratio of halogen elements to hydrogen elements within the above range can improve the capacity, first coulomb efficiency and rate performance of the negative electrode material. However, excessive halogen elements will not only cause the inside of the matrix layer to be too loose, but will also cause the specific surface area of ​​the negative electrode material to increase, and will also cause the electrochemical properties such as the capacity, first coulomb efficiency and rate performance of the negative electrode material to decline.

[0051] In some embodiments, m N / m H The value of can be 0.02, 0.05, 0.1, 0.5, 0.8, 1, 2, 4, 8, 12, 16 or 20, etc., and of course it can also be other values ​​within the above range, which is not limited here. S / m H The value of can be 0.05, 0.1, 0.5, 0.8, 1, 1, 2, 3, 4 or 5, etc., and of course it can also be other values ​​within the above range, which is not limited here. Reasonable regulation of the ratio of nitrogen and sulfur elements to hydrogen elements can enhance the binding ability of the negative electrode material with lithium ions, which is beneficial to the desolvation of lithium ions between the interfaces, making it easier for lithium ions to enter the interior of the negative electrode material, thereby further improving the rate performance of the negative electrode material. In addition, the presence of nitrogen and sulfur elements can greatly improve the powder conductivity of the negative electrode material, which is beneficial to the improvement of the early cycle stability of the negative electrode material.

[0052] In some embodiments, after doping with hydrogen, halogen, nitrogen and sulfur, chemical bonds such as CH, OH, C-Cl, CF, C-Br, CN, ON, CS and SO are formed. In the negative electrode material of the present application, by exploring the content relationship between hydrogen and nitrogen, sulfur and halogen, the mass content ratio of hydrogen to nitrogen, sulfur and halogen in the negative electrode material is regulated to an appropriate range, so that the powder conductivity, first effect and cycle performance of the material are comprehensively improved. There are carbon-hydrogen bonds formed by the combination of hydrogen atoms and carbon atoms in the negative electrode material of the present application (as shown in Figure 1). Controlling the carbon-hydrogen saturation helps to adjust the hydrophilicity of the material, improve the wettability of the material by the electrolyte, make the lithium ion conduction interface between the negative electrode material and the electrolyte smoother, and improve the mass transfer / charge transfer efficiency of the negative electrode material, thereby improving the low temperature performance and powder conductivity of the negative electrode material. In the present application, the negative electrode material also contains an appropriate amount of halogens, N elements and S elements. On the one hand, the appropriate amount of halogens, N elements and S elements plays a role in regulating the carbon-hydrogen saturation: halogens have a competitive saturation relationship with H, and their presence will occupy the H site, thereby achieving the regulation of carbon-hydrogen saturation, while nitrogen and sulfur elements may combine with hydrogen elements to form local functional groups such as amino groups, which also play a role in regulating carbon-hydrogen saturation; on the other hand, halogen elements can also participate in the formation of a more stable solid electrolyte membrane (SEI membrane) when the electrolyte contacts the negative electrode material, which can enhance the bonding strength between the negative electrode material and the solid electrolyte membrane, and is beneficial to maintaining the stability of the solid-liquid contact interface on the surface of the negative electrode material during the cyclic charge and discharge process, while being able to better inhibit the expansion of the negative electrode material, and nitrogen and sulfur elements are also beneficial to further improve the conductivity of the negative electrode material powder, thereby improving the rate performance of the negative electrode material. When the content relationship between hydrogen and nitrogen, sulfur and halogen elements in the negative electrode material satisfies the above-mentioned ratio relationship of the present application, the wettability of the negative electrode material and the electrolyte can be improved, and solid-liquid regulation can be achieved during the slurry adjustment of the negative electrode material, thereby improving the dispersibility of the slurry, reducing the sedimentation or agglomeration of the slurry, and inhibiting gas production during the slurry adjustment process, which helps to maintain the stability of the slurry. Therefore, the negative electrode material provided in this application can have the advantages of high initial efficiency, high powder conductivity, high cycle stability and low volume expansion rate. It should be noted that, after research, exploration and data verification by the applicant, no matter what the specific form of the halogen elements, nitrogen elements and sulfur elements is, as long as the above-mentioned relationship is met, the technical problems that this application wants to solve can be solved.

[0053] In some embodiments, in the negative electrode material, 50 mg / kg≤m X≤1500mg / kg, meaning the mass of halogen elements per kilogram of negative electrode material can be 50mg, 150mg, 300mg, 600mg, 900mg, 1200mg, or 1500mg, etc., and other values ​​within the above range are also possible and are not limited here. By controlling the halogen content in the negative electrode material, the initial capacity efficiency, rate capability, and cycle performance of the negative electrode material can be further improved, and the expansion of the negative electrode material can be further suppressed.

[0054] In some embodiments, in the negative electrode material, 100 mg / kg≤m N ≤4000mg / kg, meaning the mass of nitrogen per kilogram of negative electrode material can be 100mg, 500mg, 1000mg, 2000mg, or 4000mg, etc. Other values ​​within the above range are also possible and are not limited here. By controlling the nitrogen content in the negative electrode material, the initial capacity efficiency, rate capability, and cycle performance of the negative electrode material can be further improved, and the expansion of the negative electrode material can be further suppressed.

[0055] In some embodiments, in the negative electrode material, 10 mg / kg≤m S ≤200mg / kg, meaning the mass of sulfur per kilogram of the negative electrode material can be 10mg, 30mg, 50mg, 80mg, 100mg, 120mg, 150mg, 180mg, or 200mg, etc. Other values ​​within the aforementioned range are also possible and are not limited here. By controlling the sulfur content in the negative electrode material, the capacity, initial efficiency, and rate performance of the negative electrode material can be improved.

[0056] In some embodiments, the negative electrode material contains pores. The presence of pores in the negative electrode material can reserve buffer space for the volume expansion of the silicon-based active material, reduce particle crushing and rupture caused by volume expansion, and improve the cycle stability of the negative electrode material.

[0057] In some embodiments, in the pore volume distribution curve of the negative electrode material, the pore size is or There is a pore volume characteristic peak in the range; that is, in the pore volume distribution curve of the negative electrode material, the pore size is in or any value between them, or any value between them, or any value in between, and Or any value between them has a characteristic pore volume peak. Differences in the elemental composition and carbon-hydrogen saturation in the material will affect the material morphology. This application controls the mass content ratio of hydrogen to nitrogen, sulfur, and halogen elements in the negative electrode material to an appropriate range, allowing the local structure to grow longitudinally, forming the above-mentioned unique pore structure, which is beneficial to improving the negative electrode material's electrochemical properties such as rate performance and cycle stability.

[0058] In some embodiments, the median particle size of the negative electrode material is 2.0 μm to 12.0 μm, specifically 2.0 μm, 4.0 μm, 6.0 μm, 8.0 μm, 10.0 μm or 12.0 μm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0059] In some embodiments, the silicon-based active material includes at least one of elemental silicon, silicon oxide, silicon alloy and silicate; that is, the silicon-based active material can be composed of any one component of elemental silicon, silicon oxide, silicon alloy or silicate alone, or can be composed of a mixture of two or more components of elemental silicon, silicon oxide, silicon metal or silicate.

[0060] In the above embodiment, the general formula of silicon oxide is SiO x , 0<x≤2, more commonly, silicon oxide can be a mixture of multiple silicon oxide compounds, for example, a mixture of silicon oxide and silicon monoxide.

[0061] In some embodiments, the silicon-based active material further includes a doping metal M, where M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu, and Mn. Specifically, the doping metal M may be present in a silicon alloy or a silicate. The silicate may be a monobasic silicate (containing one metal ion), such as lithium silicate, magnesium silicate, aluminum silicate, iron silicate, etc., or a dibasic silicate (containing two metal ions), such as lithium magnesium silicate, lithium aluminum silicate, lithium zinc silicate, etc., or a ternary silicate (containing three metal ions), such as lithium aluminum titanium silicate, lithium magnesium aluminum silicate, etc., without limitation. In a specific embodiment, the silicon-based active material includes the doping metal Mg and / or the doping metal Li.

[0062] In some embodiments, the mass content of the metal M in the negative electrode material is 0 wt% to 15 wt%, excluding 0 wt%, and may specifically be 0.000001 wt%, 1 wt%, 5 wt%, 10 wt%, or 15 wt%, and may also be other values ​​within the above range, which is not limited herein.

[0063] In some embodiments, the mass content ω2 of the carbon element in the negative electrode material is 0.5wt% to 15wt%, specifically 0.5wt%, 1wt%, 5wt% or 10wt%, 15wt%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0064] In some embodiments, the carbon material includes at least one of graphite, graphene, amorphous carbon, diamond-like carbon, carbon nanotubes, and carbon fibers.

[0065] In some embodiments, when the carbon material is amorphous carbon, the negative electrode material may include a mixture of nitrogen-doped amorphous carbon, chlorine-doped amorphous carbon, bromine-doped amorphous carbon, iodine-doped amorphous carbon, sulfur-doped amorphous carbon, and the like.

[0066] In some embodiments, the carbon material forms a carbon layer on the surface of the silicon-based active material, and the thickness of the carbon layer ranges from 20nm to 1000nm, specifically 20nm, 100nm, 200nm, 400nm, 800nm ​​or 1000nm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0067] In some embodiments, the inorganic oxide comprises a metal oxide of aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), niobium (Nb), molybdenum (Mo), yttrium (Y), lanthanum (La), cerium (Ce), lithium (Li), or a multi-metal oxide of a combination of multiple elements.

[0068] In some embodiments, the inorganic oxide may also include aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), niobium (Nb), molybdenum (Mo), yttrium (Y), lanthanum (La), cerium (Ce), lithium (Li), etc., and phosphorus (P), silicon (Si), titanium (Ti), etc. to form single or multiple silicates, phosphates, and titanates.

[0069] In some embodiments, the tap density of the negative electrode material is 0.75 g / cm 3 ~1.35g / cm 3 , specifically 0.75g / cm 3 , 0.95g / cm 3 , 1.05g / cm 3 , 1.35g / cm 3 Or any value therebetween. Of course, the tap density of the negative electrode material can also be higher than 1.35 g / cm 3 The higher the tap density, the more beneficial it is to improve the energy density of the material, and this application does not make any special restrictions on this.

[0070] In some embodiments, the powder conductivity of the negative electrode material under a pressure of 20 kN is 0.01 S / cm to 100.00 S / cm, specifically 0.01 S / cm, 10.00 S / cm, 40.00 S / cm, 60.00 S / cm, 80.00 S / cm, 100.00 S / cm or any value therebetween. Of course, the powder conductivity of the negative electrode material may also be higher than 100.00 S / cm. The higher the powder conductivity, the more conducive it is to improving the electrochemical properties of the material. This application does not impose any special limitation on this.

[0071] In some embodiments, the specific surface area of ​​the negative electrode material is 0.50 m 2 / g~10.00m 2 / g, specifically 0.80m 2 / g, 1.00m 2 / g, 1.50m 2 / g, 2.00m 2 / g, 3.00m 2 / g, 4.00m 2 / g, 5.00m 2 / g、8.00m 2 / g or 10.00m 2 Controlling the specific surface area of ​​the negative electrode material within the above range can slow down the volume expansion of the negative electrode material, which is beneficial to improving the cycle performance of the negative electrode material.

[0072] In some embodiments, the water content in the negative electrode material is 0.01 wt% to 0.80 wt%. For example, it can be 0.01%, 0.10%, 0.40%, 0.60%, 0.80%, or any value therebetween. The lower the water content in the negative electrode material, the more beneficial it is for improving the electrochemical performance of the material. This application does not impose any particular limitation on this.

[0073] In some embodiments, the pH range of the negative electrode material is 6.00-12.00, specifically 6.00, 8.00, 9.00, 10.00, 11.00 or 12.00, etc., and other values ​​within the above range are also possible, and are not limited here. Preferably, the pH range of the negative electrode material is 7-10.

[0074] In a second aspect, the present application provides a method for preparing the above-mentioned negative electrode material, as shown in FIG2 , comprising the following steps:

[0075] S100, preparing a precursor, the precursor including a silicon-based active substance and a substrate material;

[0076] S200, in a modified gas source environment, using plasma enhanced chemical vapor deposition to modify the precursor surface to obtain a negative electrode material, wherein the modified gas source includes hydrogen, sulfur, nitrogen and halogen elements; in the negative electrode material, the mass content of hydrogen is m H , the mass content of halogen elements is m X , the mass content of sulfur element is m S , the mass content of nitrogen is m N , and satisfy the following relationship: 0.02≤m X / m H ≤5.00,0.02≤m N / m H ≤20.00,0.05≤m S / m H ≤5.00. The preparation method of the negative electrode material provided in the present application utilizes plasma enhanced chemical vapor deposition to perform surface modification treatment on the precursor of the silicon-based active substance and the substrate material in a modified gas source environment, and efficiently and uniformly performs doping of multiple elements, with high deposition efficiency and high controllability. After the surface modification treatment, the substrate material on the surface of the silicon-based active substance can combine with hydrogen elements to form carbon-hydrogen bonds, and the appropriate amount of carbon-hydrogen saturation can help to adjust the hydrophilicity of the material, thereby adjusting the hydrophilicity of the substrate material, adjusting the wettability of the electrolyte to the negative electrode material, making the lithium ion conduction interface between the negative electrode material and the electrolyte smoother, thereby improving the mass transfer / charge transfer efficiency of the negative electrode material, and thereby improving the low-temperature performance and powder conductivity of the negative electrode material. The incorporation of appropriate amounts of halogens, nitrogen, and sulfur can, on the one hand, regulate carbon-hydrogen saturation: halogens compete with hydrogen for saturation, and their presence will occupy the hydrogen site, thereby achieving regulation of carbon-hydrogen saturation. Nitrogen and sulfur may combine with hydrogen to form local functional groups such as amino groups, which also play a role in regulating carbon-hydrogen saturation. On the other hand, halogens can also participate in the formation of a more stable solid electrolyte membrane (SEI membrane) when the electrolyte contacts the negative electrode material, which can enhance the bonding strength between the negative electrode material and the solid electrolyte membrane. This helps maintain the stability of the solid-liquid contact interface on the surface of the negative electrode material during cyclic charge and discharge, while also better suppressing the expansion of the negative electrode material. Nitrogen and sulfur also help further improve the conductivity of the negative electrode material powder, thereby improving the rate performance of the negative electrode material. Therefore, modifying the surface of the negative electrode material by modifying the gas phase source can suppress the volume expansion of the negative electrode material and comprehensively improve the electrochemical properties of the negative electrode material, such as the first effect, powder conductivity, and cycle performance.

[0077] The preparation method of the present application is described in detail below with reference to the examples:

[0078] S100, preparing a precursor, the precursor including a silicon-based active substance and a substrate material.

[0079] In some embodiments, the specific step of preparing the precursor includes: coating at least a portion of the surface of the silicon-based active material with a substrate material.

[0080] In some embodiments, the specific preparation steps of the precursor include: solid-phase coating treatment of the silicon-based active material and the substrate material.

[0081] In some embodiments, the matrix material comprises a carbon material, or a mixture of a carbon material and an inorganic oxide. In some embodiments, the carbon material comprises at least one of graphite, graphene, amorphous carbon, diamond-like carbon, carbon nanotubes, and carbon fibers.

[0082] In some embodiments, the inorganic oxide comprises a metal oxide of aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), niobium (Nb), molybdenum (Mo), yttrium (Y), lanthanum (La), cerium (Ce), lithium (Li), or a multi-metal oxide of a combination of multiple elements.

[0083] In some embodiments, the inorganic oxide may also include aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), niobium (Nb), molybdenum (Mo), yttrium (Y), lanthanum (La), cerium (Ce), lithium (Li), etc., and phosphorus (P), silicon (Si), titanium (Ti), etc. to form single or multiple silicates, phosphates, and titanates.

[0084] In some embodiments, the step of solid-phase coating the silicon-based active substance with the carbon material includes: ball-milling the silicon-based material with a solid carbon source (such as asphalt, etc.), and then performing high-temperature treatment to achieve coating of the silicon-based active substance with the carbon material.

[0085] In some embodiments, the specific preparation steps of the precursor include: performing vapor-phase carbon coating on the silicon-based active material in the presence of a vapor-phase carbon source.

[0086] In some embodiments, the gaseous carbon source includes at least one of methane, ethane, ethylene, propane, and propylene.

[0087] In some embodiments, the temperature of gas-phase carbon coating is 600-1000° C., and the holding time is 1 h to 48 h. Those skilled in the art can adjust the specific reaction time according to the type of carbon source gas, flow rate, deposition temperature, and target carbon amount.

[0088] In some embodiments, the mass content of the carbon material in the precursor is between 1 wt% and 10 wt%, preferably between 2 wt% and 7 wt%.

[0089] In some embodiments, the silicon-based active material includes at least one of elemental silicon, silicon oxide, silicon alloy, and silicate.

[0090] In some embodiments, the silicon-based active material includes a doping metal M, where M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu, and Mn.

[0091] In some embodiments, when performing vapor-phase carbon coating on the silicon-based active material, the specific preparation steps of the precursor further include: crushing and screening the coated product.

[0092] In some embodiments, after S100, the method further includes purifying the precursor to remove impurities in the precursor.

[0093] In some embodiments, the specific steps of the purification process include: washing and drying the precursor.

[0094] In some embodiments, the washing process may include rinsing, soaking and centrifugation; specifically, the precursor is first rinsed with deionized water to wash away impurities on the surface of the precursor, and then the precursor is soaked and centrifuged to remove impurities inside or in the pores of the precursor, which helps to ensure that the reaction rate of hydrogen (sulfur, nitrogen or halogen) attachment between precursor particles is consistent, so that the hydrogen content (nitrogen content, sulfur content and halogen content) between different particles is small.

[0095] In some embodiments, deionized water is used for rinsing due to cost and rinsing effect considerations. Of course, other suitable detergents may also be used for rinsing.

[0096] In some embodiments, for cost and soaking effect considerations, the material is soaked in deionized water. Of course, other suitable soaking liquids can also be used to soak the silicon-based active substance coated with the carbon material; in this embodiment, preferably, the mass ratio of the material to the liquid during the soaking process is (0.5-1.5): (1.5-2.5). If the ratio is too large, the soaking effect will be unsatisfactory, and if the ratio is too small, it will cause a waste of the soaking liquid (deionized water).

[0097] In some embodiments, the drying is vacuum drying to minimize the drying temperature. Low-temperature vacuum drying can effectively control the surface oxidation degree of the material, which is beneficial to improving the hydrogen (sulfur, nitrogen or halogen) reaction efficiency of the precursor.

[0098] In some embodiments, the centrifugation time is 30 min-360 min, specifically 30 min, 90 min, 150 min, 200 min, 250 min, 300 min or 360 min, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0099] In some embodiments, the drying temperature is 45°C to 80°C, specifically 45°C, 50°C, 60°C, 70°C or 80°C, etc., and of course it can also be other values ​​within the above range, which is not limited here; the drying time is 3h to 48h, specifically 3h, 10h, 20h, 30h, 40h or 48h, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0100] S200, in a modified gas source environment, using plasma enhanced chemical vapor deposition to modify the precursor surface to obtain a negative electrode material, wherein the modified gas source includes hydrogen, sulfur, nitrogen and halogen elements; the negative electrode material contains hydrogen, halogen, nitrogen and sulfur, wherein the mass content of hydrogen is m H , the mass content of halogen elements is m X , the mass content of sulfur element is m S , the mass content of nitrogen is m N , and satisfy the following relationship: 0.02≤m X / m H ≤5.00,0.02≤m N / m H ≤20.00,0.05≤m S / m H ≤5.00.

[0101] In some embodiments, the powder conductivity of the precursor under a pressure of 20KN is 0.001S / cm to 0.1S / cm, specifically 0.001S / cm, 0.005S / cm, 0.01S / cm, 0.05S / cm or 0.1S / cm, etc., and of course it can also be other values ​​within the above range, which is not limited here; the powder conductivity of the negative electrode material under a pressure of 20KN is 0.1S / cm to 100.0S / cm, specifically 0.1S / cm, 1S / cm, 10S / cm, 50S / cm or 100S / cm, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0102] In some embodiments, in the pore volume distribution curve of the negative electrode material, the pore size is or There is a pore volume characteristic peak in the range; that is, in the pore volume distribution curve of the negative electrode material, the pore size is in or any value between them, or any value between them, or any value in between, and Or there is a characteristic pore volume peak at any value between them. The composition difference of the modified gas phase source during the deposition process, the deposition method, the deposition rate and other deposition conditions will affect the morphology of the material. The present application controls the mass content ratio of hydrogen to nitrogen, sulfur and halogen elements in the modified gas phase source to an appropriate range, and controls the deposition rate and other deposition conditions to an appropriate range, so that the surface layer of the material is based on carbon elements, and the local structure grows vertically, forming the above-mentioned unique mesoporous structure.

[0103] In some embodiments, S200 specifically involves evacuating the precursor, placing the precursor under a modified gas source, and performing plasma-enhanced chemical vapor deposition on the precursor under bias voltage conditions. By regulating the modified gas source with different gas compositions and adjusting the bias voltage, the deposition efficiency of hydrogen, halogen, nitrogen, and sulfur on the precursor can be effectively controlled, thereby controlling the morphology, powder conductivity, rate capability, cycling performance, initial capacity efficiency, and low-temperature performance of the resulting negative electrode material.

[0104] In some embodiments, the bias voltage ranges from -500V to 0V, excluding 0V, specifically -500V, -400V, -300V, -200V, -100V, -50V or -0.1V, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0105] In some embodiments, before performing plasma enhanced chemical vapor deposition, the vacuum pressure is less than 1.0 Torr.

[0106] In some embodiments, the operating pressure of plasma-enhanced chemical vapor deposition ranges from 500 Pa to 5000 Pa, specifically 500 Pa, 1000 Pa, 2000 Pa, 3000 Pa, 4000 Pa, or 5000 Pa, and other values ​​within the aforementioned range are also possible and are not limited herein. Selecting a pressure within this range is beneficial to surface treatment efficiency, and controlling the plasma treatment intensity allows the specific surface area of ​​the negative electrode material to fall within a preferred range.

[0107] In some embodiments, the deposition temperature of plasma-enhanced chemical vapor deposition ranges from 200°C to 800°C, specifically 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, or 800°C, and other values ​​within this range are also possible and are not limited herein. By selecting a suitable processing temperature, the silicon-based core of the negative electrode material can be controlled to have a preferred crystalline form.

[0108] In some embodiments, the flow rate of the modified gas source ranges from 200 ml / min to 5000 ml / min, specifically 200 ml / min, 300 ml / min, 400 ml / min, or 5000 ml / min, and other values ​​within this range are also possible and are not limited to this. By selecting a reasonable flow rate, the processing capacity of the modified source is controlled to control the ratio of the relevant elements.

[0109] In some embodiments, the modified gas source includes a reaction gas, which includes hydrogen, a nitrogen-containing gas, a sulfur-containing gas, and a halogen source gas; specifically, the nitrogen-containing gas can be one or more of nitrogen and ammonia, the sulfur-containing gas can be hydrogen sulfide, and the halogen source gas can be one or more of fluorine, chlorine, bromine, iodine, hydrogen bromide, hydrogen iodide, and carbon tetrafluoride. When the modified gas source includes iodine, the added iodine raw material can be gaseous or solid. Preferably, the added iodine raw material is solid iodine, so as to facilitate the control of the amount of iodine added. Solid iodine is easily sublimated into a gaseous state and mixed with other gas components in the modified gas source; of course, those skilled in the art can also choose other types of nitrogen-containing gases, sulfur-containing gases and halogen source gases, as long as it is convenient to deposit nitrogen, sulfur and halogen elements on the precursor.

[0110] In some embodiments, the modified gas source further includes a protective gas, and the protective gas includes one or more of argon, krypton, nitrogen, neon, and helium.

[0111] In some specific embodiments, the volume ratio of hydrogen to shielding gas is in the range of 1:(0.1-5), specifically 1:0.1, 1:1, 1:2, 1:3, 1:4, 1:5 or other values ​​within the above range. By selecting the volume ratio of hydrogen to shielding gas within this range, it is beneficial to regulate the H content within the preferred range.

[0112] In some embodiments, the volume ratio of hydrogen to nitrogen-containing gas is 1:(0-1.2), specifically 1:0.05, 1:0.1, 1:0.3 or other values ​​within the above range.

[0113] In some embodiments, the volume ratio of hydrogen to sulfur-containing gas is 1:(0-0.2), specifically 1:0.01, 1:0.03, 1:0.05, 1:0.15, 1:0.20 or other values ​​within the above range.

[0114] In some embodiments, the volume ratio of hydrogen gas to halogen source gas is 1:(0-0.05), specifically 1:0.015, 1:0.01, 1:0.03, 1:0.05 or other values ​​within the above range.

[0115] In some embodiments, after step S200, the preparation method further comprises screening the modified product to obtain a finished negative electrode material with a target particle size.

[0116] Thirdly,

[0117] One embodiment of the present application provides a secondary battery (such as a lithium-ion battery, a sodium-ion battery, etc.), comprising a housing, an electrode assembly, and an electrolyte / electrolyte. The electrode assembly and the electrolyte / electrolyte are both located within the housing.

[0118] The outer shell can be a packaging bag encapsulated by an encapsulation film (such as an aluminum-plastic film), such as a soft-pack battery. In other embodiments, the secondary battery can also be a steel-shell battery, an aluminum-shell battery, etc.

[0119] Figure 3 shows a schematic diagram of a battery in a discharged state, i.e., during operation. As shown in Figure 3, the electrode assembly includes a positive electrode sheet 110, a negative electrode sheet 120, and a separator 130, with the separator being disposed between the positive and negative electrode sheets. The electrode assembly can be a laminated structure, in which the positive electrode sheets, separators, and negative electrode sheets are alternately stacked in sequence. In other embodiments, the electrode assembly can also be a wound structure, in which the positive electrode sheets, separators, and negative electrode sheets are stacked in sequence and then wound.

[0120] positive electrode

[0121] The positive electrode sheet 110 includes a positive electrode current collector 111 and a positive electrode active layer 112 provided on at least one surface of the positive electrode current collector. The positive electrode current collector can be made of aluminum foil or nickel foil, etc., or it can be any composite current collector disclosed in the prior art, such as but not limited to the current collector formed by combining the aforementioned conductive foil and the polymer substrate. The positive electrode active layer contains a positive electrode active material, and the positive electrode active material includes a compound that can reversibly embed and deintercalate metal ions. In some embodiments, the positive electrode active material may include a lithium transition metal composite oxide, a sodium transition metal composite oxide, etc. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese and nickel. In some embodiments, the positive electrode active material may include but is not limited to lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt ternary material (NCM), lithium manganese oxide (LiMn2O4), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4) or at least one of lithium iron phosphate (LiFePO4).

[0122] negative electrode

[0123] The negative electrode sheet 120 includes a negative electrode current collector 121 and a negative electrode active material layer 122 disposed on at least one surface of the negative electrode current collector. The negative electrode current collector can be made of at least one of copper foil, nickel foil, stainless steel foil, titanium foil, or a carbon-based current collector. It can also be any composite current collector disclosed in the prior art, such as, but not limited to, a current collector formed by combining the aforementioned conductive foil and a polymer substrate. The negative electrode active material layer includes a negative electrode material.

[0124] During battery operation, that is, when the battery is in a discharged state, the metal ions 140 (eg, lithium ions) in the negative electrode are released from the lattice of the negative electrode material, pass through the separator 130 via the electrolyte / electrolyte, and are embedded in the lattice of the positive electrode material.

[0125] Conversely, when the battery is charged by applying an external circuit, the oxidation of the positive electrode material causes the metal ions (such as lithium ions) in the positive electrode to be released from the lattice of the positive electrode material, pass through the isolation membrane through the electrolyte / electrolyte, and move to the negative electrode; at the same time, the negative electrode material undergoes a reduction reaction, causing the metal ions to be embedded in the lattice of the negative electrode material.

[0126] As metal ions move back and forth between the positive and negative electrodes, the battery can achieve discharge and charging processes over thousands of cycles.

[0127] Those skilled in the art will understand that the above-described negative electrode material and battery preparation method are merely examples, and other methods commonly used in the art may be used without departing from the disclosure of this application.

[0128] The following further illustrates the embodiments of the present application in multiple embodiments. The embodiments of the present application are not limited to the following specific embodiments. Within the scope of the unchanged main rights, appropriate changes can be made to the implementation.

[0129] Test method:

[0130] 1. Particle size: Particle size is measured using Mastersizer 3000 laser diffraction technology. When a laser beam passes through a dispersed particle sample, the particle size measurement is completed by measuring the intensity of the scattered light. The data is then used to analyze and calculate the particle size distribution that forms the scattering spectrum. D50: The particle size corresponding to when the cumulative volume particle size distribution percentage of a sample reaches 50%. Its physical meaning is that 50% of the particles have a particle size larger than it, and 50% of the particles have a particle size smaller than it. D50 is also called the median particle size. The D90 particle size, D50 particle size, and D10 particle size are the equivalent diameters (average particle sizes) of the largest particles in the distribution curve when the cumulative distribution is 90%, 50%, and 10%, respectively.

[0131] 2. Specific surface area: The specific surface area was measured using a Micromeritics TriStar 3000 specific surface area and pore size analyzer (USA).

[0132] 3. Tap density: Use a vibrator to weigh a certain amount of sample and vibrate 3000 times at 300 times / min to test the tap density.

[0133] 4. Coating (carbon layer) thickness: The material is sectioned using a FIB-SEM device, and the average coating thickness is measured in the SEM.

[0134] 5. Powder Conductivity: The volume resistivity of the negative electrode material powder is measured using the four-probe method. The instrument measures the resistance of the powder under five pressure points: 4kN, 8kN, 12kN, 16kN, and 20kN. The computer then automatically calculates the conductivity and resistivity of the negative electrode material powder.

[0135] 6. Test of the water content of the negative electrode material: Use the weight method to test. Place the material in a vacuum oven at 250°C and bake it for 48 hours. Check the weight loss before and after baking and convert it into water.

[0136] 7. pH test of negative electrode material: Mix 5g of material with 45g of deionized water, ultrasonicate for 30min, and then test using an electronic pH meter.

[0137] 8. Pore volume: Use a BET micropore ratio meter and pore size analyzer and follow the corresponding test guide of the equipment for testing.

[0138] 9. Test of element content:

[0139] Nitrogen and hydrogen content were tested using an ONH2000 oxygen, nitrogen, and hydrogen elemental analyzer. The sample and flux were placed in a graphite crucible, heated to a maximum of 3000°C, and molten nitrogen and hydrogen were generated by high-temperature cracking. The carrier gas was fed into a thermal conductivity cell for measurement. The single test volume was 10±1 mg, nickel foil was used as the flux, the test recalibration channel was High N / H, the degassing time was 30 seconds, the degassing power was 5 kW, the rinse time was set to 20 seconds, the stabilization time was set to 40 seconds, the infrared integration delay was set to 2 seconds, the analysis time was 60 seconds, and the analysis power was 4 kW. The sample was tested twice, and the average value was taken, with four decimal places retained.

[0140] Sulfur content testing: An Eltech infrared carbon-sulfur analyzer (CS i) was used for testing. A certain amount of sample was weighed and placed into a ceramic crucible. A flux was added and the sample was passed through a high-purity oxygen furnace for combustion to generate carbon dioxide and sulfur dioxide. The carbon and sulfur contents of the gases were measured using an infrared detector. A multi-component co-solvent was used, with a sample volume of 50 g, a blank analysis time of 40 seconds, a furnace flush time of 2 seconds, a furnace flush flow of 180 L / h, a stabilization time of 45 to 60 seconds, and an analytical carrier gas flow of 180 L / h.

[0141] Halogen ion content testing: Tested in accordance with GB / T 24533-2019 using an ICS-6000 instrument, using an eluent concentration of 25 nM, a flow rate of 0.30 mL / min, a sample weight of 0.7 g, an ultrasonication time of 3 minutes, and natural sedimentation. Accurately weigh 0.7 ± 0.01 g of sample, add 50 mL of primary water, disperse manually for 5 minutes, and then ultrasonicate for 3 minutes at 240 W.

[0142] 10. Electrical performance test:

[0143] Referring to the operating instructions BTRTC / ZY / 01-020 "Button Battery Method Operating Instructions" of BTR Company, button batteries were assembled; among them, the electrodes used metal lithium sheets, and the separator was a PP-PE-PP composite film with a diameter of 19.2mm; the electrolyte component ratio was EC / EMC / DMC=1 / 1 / 1, and the lithium salt (LiPF6) concentration was 1.05mol / L.

[0144] Capacity test: The negative electrode materials prepared in the examples and comparative examples were prepared into batteries, and tested using a button battery charging and discharging device, with 0.1C constant current charging to 10mV, then 0.02C constant current charging to 5mV, and 0.1C constant current discharge to 1.5V cutoff.

[0145] Half-cell 50-week cycle test: The negative electrode materials prepared in the examples and comparative examples were prepared into batteries and tested using a button battery charging and discharging device. In the first week, the battery was discharged at 0.1C to 0.01V, discharged at 0.01C in arithmetic descending order to 0.01V, discharged at 0.01C to 0.005V, and charged at 0.1C to 1.5V; in the second week, the battery was discharged at 0.2C to 0.01V, discharged at 0.02C in arithmetic descending order to 0.01V, discharged at 0.02C to 0.005V, and charged at 0.2C to 1.5V; in the third week, the battery was discharged at 0.1C to 0.01V, discharged at 0.02C in arithmetic descending order to 0.01V, discharged at 0.02C to 0.005V, and charged at 0.2C to 1.5V; in the fourth week, the battery was discharged at 0.1C to 0.01V, discharged at 0.01C in arithmetic descending order to 0.01V, discharged at 0.02C to 0.005V, and charged at 0.2C to 1.5V; in the fifth week, the battery was discharged at 0.1C to 0.01V, discharged at 0.01C to 0.005V, and charged at 0.2C to 1.5V. For 3 weeks, discharge at 0.5C to 0.01V, discharge at 0.05C in a regularly decreasing manner to 0.01V, discharge at 0.05C to 0.005V and charge at 0.5C to 1.5V; from the 4th to the 50th week, discharge at 1C to 0.01V, discharge at 0.1C in a regularly decreasing manner to 0.01V, discharge at 0.1C to 0.005V and charge at 1C to 1.5V; for the 51st week, discharge at 0.1C to 0.01V, discharge at 0.01C in a regularly decreasing manner to 0.01V and discharge at 0.01C to 0.005V.

[0146] Full battery performance test: Full battery performance test was conducted using 18650 small cylindrical batteries. Silicon-based materials and graphite were compounded according to a capacity of 450mAh / g. The relevant performance tests were completed according to the methods specified in the national standard GB / T 31486-2015.

[0147] Example 1

[0148] A method for preparing a negative electrode material comprises the following steps:

[0149] (1) Silicon oxide was coated with graphite to obtain 1000 g of a precursor (the mass content of carbon element was 5 wt%), which was rinsed with deionized water for 30 min, vacuum dried for 12 h at a drying temperature of 75° C., and then sieved to obtain a precursor of the target particle size.

[0150] (2) The precursor is placed on the bias voltage platform in the plasma reaction chamber, and after vacuum treatment to below 0.1 Pa, a modified gas source is introduced at a flow rate of 3000 ml / min, wherein the modified gas source is a mixed gas of hydrogen, argon, ammonia, hydrogen sulfide and chlorine, and the volume ratio of hydrogen, argon, ammonia, hydrogen sulfide and chlorine is 1:1:0.2:0.03:0.01; after the pressure in the reaction chamber is controlled to 2000 Pa by a vacuum pump, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -200 V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to maintain it at 2000 Pa, and the timing reaction is started. The reaction time is 24 hours, and the reaction temperature is controlled between 450°C and 500°C to obtain a modified product.

[0151] (3) The modified product was screened and dried under vacuum at 75°C for 12 h to obtain a finished negative electrode material.

[0152] The specific electrochemical properties of the negative electrode material obtained in Example 1 are shown in Table 2.

[0153] The finished negative electrode material prepared in Example 1 includes a silicon-based active substance and a carbon material. The carbon material is located on at least a portion of the surface of the silicon-based active substance. The negative electrode material contains hydrogen, halogen, nitrogen, and sulfur. Specific test data are shown in Table 1.

[0154] In addition, the negative electrode material obtained in Example 1 has the following characteristics: a median particle size of 5.3 μm, a carbon content of 4.95 wt%, and a tap density of 0.98 g / cm 3 , moisture content is 0.21%, pH=9.63, specific surface area is 1.88m 2 / g.

[0155] In addition, the negative electrode material obtained in Example 1 was as well as There is a characteristic pore volume peak in each pore size range, as shown in Figure 4.

[0156] Example 2

[0157] A method for preparing a negative electrode material comprises the following steps:

[0158] (1) Lithium-doped silicon oxide was coated with graphene to obtain 1000 g of a precursor (the mass content of carbon element was 5 wt%), and the precursor was centrifuged and rinsed with deionized water for 2 h, and then vacuum dried at a drying temperature of 80° C. for 24 h, and then sieved to obtain a precursor of the target particle size.

[0159] (2) The precursor is placed on the bias voltage platform in the plasma reaction chamber, and after vacuum treatment to below 0.1 Pa, a modified gas source is introduced at a flow rate of 3000 ml / min, wherein the modified gas source is a mixed gas of hydrogen, argon, ammonia, hydrogen sulfide and carbon tetrafluoride, with a volume ratio of 1:1:0.1:0.05:0.05; after the pressure in the reaction chamber is controlled to 2000 Pa by a vacuum pump, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -200 V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to maintain it at 2000 Pa, and the timing reaction is started. The reaction time is 24 hours, and the reaction temperature is controlled between 450°C and 500°C to obtain a modified product.

[0160] (3) The modified product was sieved and further vacuum dried for 12 h at a drying temperature of 75° C. to obtain a finished negative electrode material.

[0161] The specific electrochemical properties of the negative electrode material product prepared in Example 2 are shown in Table 2.

[0162] The finished negative electrode material prepared in Example 2 includes a silicon-based active substance and a carbon material. The carbon material is located on at least a portion of the surface of the silicon-based active substance. The negative electrode material contains hydrogen, halogen, nitrogen, and sulfur. Specific test data are shown in Table 1.

[0163] The finished negative electrode material obtained in Example 2 has the following characteristics: median particle size of 5.62 μm, carbon content of 5.01 wt%, and tap density of 0.98 g / cm 3 , moisture content is 0.17%, pH=10.47, specific surface area is 1.92m 2 / g.

[0164] In addition, the negative electrode material obtained in Example 2 was as well as There is one pore volume characteristic peak in each pore size range.

[0165] Example 3

[0166] A method for preparing a negative electrode material comprises the following steps:

[0167] (1) Silicon oxide was coated with graphite to obtain 1000 g of a precursor (the mass content of carbon element was 5 wt%), which was rinsed with deionized water for 30 min, vacuum dried for 12 h at a drying temperature of 75° C., and then sieved to obtain a precursor of the target particle size.

[0168] (2) The precursor is placed on the bias voltage platform in the reaction chamber, and after vacuum treatment to below 0.1 Pa, a modified gas source is introduced at a flow rate of 3000 ml / min, wherein the modified gas source is a mixed gas of hydrogen, argon, ammonia, hydrogen sulfide and hydrogen bromide, with a volume ratio of 1:1:0.15:0.03:0.03. After the pressure in the reaction chamber is controlled to 3000 Pa by a vacuum pump, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -200 V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to maintain it at 3000 Pa, and the timing reaction is started. The reaction time is 24 hours, and the reaction temperature is controlled between 650 and 700 ° C to obtain a modified product.

[0169] (3) The modified product was sieved and further vacuum dried for 12 h at a drying temperature of 75° C. to form a finished negative electrode material.

[0170] The specific electrochemical properties of the negative electrode material product prepared in Example 3 are shown in Table 2.

[0171] The finished negative electrode material prepared in Example 3 includes a silicon-based active substance and a carbon material. The carbon material is located on at least a portion of the surface of the silicon-based active substance. The negative electrode material contains hydrogen, halogen, nitrogen and sulfur. The specific test data are shown in Table 1.

[0172] The negative electrode material obtained in Example 3 has the following characteristics: median particle size of 5.12 μm, carbon content of 4.95 wt%, and tap density of 0.98 g / cm 3 , moisture content is 0.07%, pH=9.51, specific surface area is 2.49m 2 / g.

[0173] In addition, the negative electrode material obtained in Example 3 was as well as There is one pore volume characteristic peak in each pore size range.

[0174] Example 4

[0175] A method for preparing a negative electrode material comprises the following steps:

[0176] (1) Lithium-doped silicon dioxide was coated with graphite to obtain 1000 g of a precursor (the mass content of carbon element was 5 wt%), and the precursor was centrifuged and rinsed with deionized water for 2 h, and then vacuum dried at 80 ° C for 24 h, and then sieved to obtain a precursor of the target particle size.

[0177] (2) The precursor is placed on the bias voltage platform in the reaction chamber, and after vacuum treatment to below 0.1 Pa, a modified gas source is introduced at a flow rate of 3000 ml / min, wherein the modified gas source is a mixed gas of hydrogen, argon, ammonia, hydrogen sulfide, and hydrogen iodide, and the volume ratio is 1:1.5:0.05:0.01:0.01; after the pressure in the reaction chamber is controlled to 3000 Pa by a vacuum pump, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -200 V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to maintain it at 3000 Pa, and the timing reaction is started. The reaction time is 24 hours, and the reaction temperature is controlled between 700 and 750 ° C to obtain a modified product.

[0178] (3) The modified product was sieved and further vacuum dried for 12 h at a drying temperature of 75° C. to form a finished negative electrode material.

[0179] The specific electrochemical properties of the negative electrode material product prepared in Example 4 are shown in Table 2.

[0180] The finished negative electrode material prepared in Example 4 includes a silicon-based active substance and a carbon material. The carbon material is located on at least a portion of the surface of the silicon-based active substance. The negative electrode material contains hydrogen, halogen, nitrogen and sulfur. The specific test data are shown in Table 1.

[0181] The finished negative electrode material obtained in Example 4 has the following characteristics: median particle size of 5.35 μm, carbon content of 4.95 wt%, and tap density of 0.98 g / cm 3 , moisture content is 0.17%, pH=10.47, specific surface area is 1.92m 2 / g.

[0182] In addition, the negative electrode material obtained in Example 4 was as well as There is one pore volume characteristic peak in each pore size range.

[0183] Example 5

[0184] A method for preparing a negative electrode material comprises the following steps:

[0185] (1) Silicon oxide was coated with graphite to obtain 1000 g of a precursor, which was rinsed with deionized water for 30 min and then vacuum dried for 12 h at a drying temperature of 75° C., and then sieved to obtain a precursor of the target particle size.

[0186] (2) The precursor is placed on the bias voltage platform in the reaction chamber, and after vacuum treatment to below 0.1 Pa, a modified gas source is introduced at a flow rate of 3000 ml / min, wherein the modified gas source is a mixed gas of hydrogen, argon, ammonia, hydrogen sulfide, and chlorine, and the volume ratio is 1:1:0.05:0.015:0.05. After the vacuum pump controls the pressure in the reaction chamber to 3000 Pa, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -200 V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to maintain it at 3000 Pa, and the timing reaction is started. The reaction time is 24 hours, and the reaction temperature is controlled between 650 and 700 ° C to obtain a modified product.

[0187] (3) The modified product was sieved and further vacuum dried for 12 h at a drying temperature of 75° C. to form a finished negative electrode material.

[0188] The specific electrochemical properties of the negative electrode material product prepared in Example 5 are shown in Table 2.

[0189] The finished negative electrode material prepared in Example 5 includes a silicon-based active substance and a carbon material. The carbon material is located on at least a portion of the surface of the silicon-based active substance. The negative electrode material contains hydrogen, halogen, nitrogen and sulfur. The specific test data are shown in Table 1.

[0190] The finished negative electrode material obtained in Example 5 has the following characteristics: median particle size of 5.08 μm, carbon content of 5.32 wt%, and tap density of 0.98 g / cm 3 , moisture content is 0.05%, pH=9.45, specific surface area is 2.23m 2 / g.

[0191] In addition, the negative electrode material obtained in Example 5 was as well as There is one pore volume characteristic peak in each pore size range.

[0192] Example 6

[0193] A method for preparing a negative electrode material comprises the following steps:

[0194] (1) A mixture of silicon oxide and lithium silicate was coated with a mixture of graphite and graphene to obtain 1000 g of a precursor (the mass content of carbon element was 5 wt%), which was rinsed with deionized water for 30 min, vacuum dried for 10 h at a drying temperature of 80°C, and then sieved to obtain a precursor of the target particle size.

[0195] (2) The precursor is placed on the bias voltage platform in the reaction chamber, and after vacuum treatment to below 0.1 Pa, a modified gas source is introduced at a flow rate of 5000 ml / min, wherein the modified gas source is a mixed gas of hydrogen, argon, ammonia, hydrogen sulfide, and chlorine, and the volume ratio is 1:5:0.3:0.015:0.01; after the pressure in the reaction chamber is controlled to 2000 Pa by a vacuum pump, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -200 V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to maintain it at 2000 Pa, and the timing reaction is started. The reaction time is 24 hours, and the reaction temperature is controlled between 450°C and 500°C to obtain a modified product.

[0196] (3) The modified product was sieved and further vacuum dried for 12 h at a drying temperature of 75° C. to form a finished negative electrode material.

[0197] The specific electrochemical properties of the negative electrode material product prepared in Example 6 are shown in Table 2.

[0198] The finished negative electrode material prepared in Example 6 includes a silicon-based active substance and a carbon material. The carbon material is located on at least a portion of the surface of the silicon-based active substance. The negative electrode material contains hydrogen, halogen, nitrogen and sulfur. The specific test data are shown in Table 1.

[0199] The finished negative electrode material obtained in Example 6 has the following characteristics: median particle size of 8.4 μm, carbon content of 4.89 wt%, and tap density of 0.95 g / cm 3 , moisture content is 0.08%, pH=9.55, specific surface area is 1.54m 2 / g.

[0200] In addition, the finished negative electrode material obtained in Example 6 as well as There is one pore volume characteristic peak in each pore size range.

[0201] Example 7

[0202] A method for preparing a negative electrode material comprises the following steps:

[0203] (1) Silicon oxide was coated with amorphous carbon to obtain 1000 g of a precursor (the mass content of carbon element was 5 wt%), the precursor was rinsed with deionized water for 30 min, and then vacuum dried for 12 h at a drying temperature of 75° C., and then sieved to obtain a precursor of the target particle size.

[0204] (2) The precursor is placed on the bias voltage platform in the reaction chamber, and after vacuum treatment to below 0.1 Pa, a modified gas source is introduced at a flow rate of 3000 ml / min, wherein the modified gas source is a mixed gas of hydrogen, argon, nitrogen, hydrogen sulfide, and iodine, and the volume ratio is 1:5:0.05:0.2:0.1; after the pressure in the reaction chamber is controlled to 5000 Pa by a vacuum pump, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -200 V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to maintain it at 3000 Pa, and the timing reaction is started. The reaction time is 24 hours, and the reaction temperature is controlled between 500°C and 800°C to obtain a modified product.

[0205] (3) The modified product was sieved and further vacuum dried for 12 h at a drying temperature of 75° C. to form a finished negative electrode material.

[0206] The specific electrochemical properties of the negative electrode material product prepared in Example 7 are shown in Table 2.

[0207] The finished negative electrode material prepared in Example 7 includes a silicon-based active substance and a carbon material. The carbon material is located on at least a portion of the surface of the silicon-based active substance. The negative electrode material contains hydrogen, halogen, nitrogen and sulfur. The specific test data are shown in Table 1.

[0208] The finished negative electrode material obtained in Example 7 has the following characteristics: median particle size of 5.5 μm, carbon content of 6.54 wt%, and tap density of 0.98 g / cm 3 , moisture content is 0.21%, powder conductivity (under 20kN) is 4.39S / cm, pH=9.63, specific surface area is 1.88m 2 / g.

[0209] In addition, the negative electrode material obtained in Example 7 was as well as There is one pore volume characteristic peak in each pore size range.

[0210] Example 8

[0211] A method for preparing a negative electrode material comprises the following steps:

[0212] (1) Magnesium-doped silicon oxide was coated with graphite to obtain 1000 g of a precursor (the mass content of carbon element was 5 wt%), which was rinsed with deionized water for 30 min and then vacuum-dried for 12 h at a drying temperature of 75° C., and then sieved to obtain a precursor of the target particle size.

[0213] (2) The precursor is placed on the bias voltage platform in the reaction chamber, and after vacuum treatment to below 0.1Pa, a modified gas source is introduced at a flow rate of 3000ml / min, wherein the modified gas source is a mixed gas of hydrogen and argon, nitrogen, hydrogen sulfide and chlorine, and the volume ratio is 1:1:0.15:0.01:0.015; after the pressure in the reaction chamber is controlled to 2000Pa by a vacuum pump, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -200V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to keep it at 2000Pa, and the timing reaction is started. The reaction time is 24h, and the reaction temperature is controlled between 450℃ and 500℃ to obtain a modified product.

[0214] (3) The modified product was sieved and further vacuum dried for 12 h at a drying temperature of 75° C. to form a finished negative electrode material.

[0215] The specific electrochemical properties of the negative electrode material product prepared in Example 8 are shown in Table 2.

[0216] The finished negative electrode material prepared in Example 8 includes a silicon-based active substance and a carbon material. The carbon material is located on at least a portion of the surface of the silicon-based active substance. The negative electrode material contains hydrogen, halogen, nitrogen and sulfur. The specific test data are shown in Table 1.

[0217] The finished negative electrode material obtained in Example 8 has the following characteristics: median particle size of 5.13 μm, carbon content of 4.98 wt%, and tap density of 0.98 g / cm 3 , moisture content is 0.22%, pH=9.61, specific surface area is 1.85m 2 / g.

[0218] In addition, the negative electrode material obtained in Example 8 was as well as There is one pore volume characteristic peak in each pore size range.

[0219] Example 9

[0220] A method for preparing a negative electrode material comprises the following steps:

[0221] (1) A mixture of lithium aluminum doped silicon oxide was coated with graphite to obtain 1000 g of a precursor (the mass content of carbon element was 5 wt%), which was rinsed with deionized water for 30 min, vacuum dried for 12 h at a drying temperature of 75°C, and then sieved to obtain a precursor of the target particle size.

[0222] (2) The precursor is placed on the bias voltage platform in the reaction chamber, and after vacuum treatment to below 0.1 Pa, a modified gas source is introduced at a flow rate of 3000 ml / min, wherein the modified gas source is a mixed gas of hydrogen and argon, nitrogen, ammonia, hydrogen sulfide, chlorine and iodine, and the volume ratio is 1:1:0.005:0.005:0.04:0.005:0.005; after the pressure in the reaction chamber is controlled to 2000 Pa by a vacuum pump, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -200 V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to maintain it at 2000 Pa, and the timing reaction is started. The reaction time is 24 hours, and the reaction temperature is controlled between 450°C and 500°C to obtain a modified product.

[0223] (3) The modified product was sieved and further vacuum dried for 12 h at a drying temperature of 75° C. to form a finished negative electrode material.

[0224] The specific electrochemical properties of the negative electrode material product prepared in Example 9 are shown in Table 2.

[0225] The negative electrode material prepared in Example 9 includes a silicon-based active substance and a carbon material. The carbon material is located on at least a portion of the surface of the silicon-based active substance. The negative electrode material contains hydrogen, halogen, nitrogen and sulfur. The specific test data are shown in Table 1.

[0226] The negative electrode material prepared in Example 9 also has the following characteristics: a median particle size of 5.18 μm, a carbon content of 4.99 wt%, and a tap density of 0.98 g / cm 3 , moisture content is 0.15%, pH=9.83, specific surface area is 1.98m 2 / g.

[0227] In addition, the finished negative electrode material obtained in Example 9 as well as There is one pore volume characteristic peak in each pore size range.

[0228] Comparative Example 1

[0229] Different from Example 1, no plasma treatment is performed.

[0230] The negative electrode material prepared in Comparative Example 1 also has the following characteristics: median particle size of 5.21 μm, carbon content of 4.98 wt%, and tap density of 0.98 g / cm 3 , moisture content is 0.25%, pH=9.69, specific surface area is 1.81m 2 / g.

[0231] In addition, the negative electrode material obtained in Comparative Example 1 There is a large broad peak within the pore size range.

[0232] Comparative Example 2

[0233] A method for preparing a negative electrode material comprises the following steps:

[0234] The difference from Example 2 is that:

[0235] (2) The precursor is placed on the bias voltage platform in the reaction chamber, and after vacuum treatment to below 0.1 Pa, a modified gas source is introduced at a flow rate of 3000 ml / min, wherein the modified gas source is a mixed gas of hydrogen, argon, ammonia and hydrogen sulfide, and the volume ratio is 0.5:1:1:1; after the pressure in the reaction chamber is controlled to 4000 Pa by a vacuum pump, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -500 V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to maintain it at 2000 Pa, and the timing reaction is started. The reaction time is 24 hours, and the reaction temperature is measured between 450°C and 500°C to obtain a modified product.

[0236] The negative electrode material prepared in Comparative Example 2 has the following characteristics: median particle size of 5.38 μm, carbon content of 5.05 wt%, and tap density of 0.98 g / cm 3 , moisture content is 0.13%, pH=10.47, specific surface area is 1.92m 2 / g.

[0237] In addition, the negative electrode material obtained in Comparative Example 2 as well as There is one pore volume characteristic peak in each pore size range.

[0238] Comparative Example 3

[0239] A method for preparing a negative electrode material comprises the following steps:

[0240] The difference from Example 2 is that:

[0241] (2) The precursor is placed on the bias voltage platform in the plasma reaction chamber, and after vacuum treatment to below 0.1 Pa, a modified gas source is introduced at a flow rate of 2000 ml / min, wherein the modified gas source is a mixed gas of hydrogen, argon, ammonia and carbon tetrafluoride, with a volume ratio of 1:1:0.1:0.03; after the pressure in the reaction chamber is controlled to 1500 Pa by a vacuum pump, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -200 V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to maintain it at 1500 Pa, and the timing reaction is started. The reaction time is 24 hours, and the reaction temperature is controlled between 400°C and 450°C to obtain a modified product.

[0242] The negative electrode material obtained in Comparative Example 3 has the following characteristics: median particle size of 5.36 μm, carbon content of 4.96 wt%, and tap density of 0.97 g / cm 3 , moisture content is 0.09%, pH=9.53, specific surface area is 1.99m 2 / g.

[0243] In addition, the negative electrode material obtained in Comparative Example 3 as well as There is one pore volume characteristic peak in each pore size range.

[0244] Comparative Example 4

[0245] A method for preparing a negative electrode material comprises the following steps:

[0246] The difference from Example 2 is that:

[0247] (2) The precursor is placed on the bias voltage platform in the plasma reaction chamber, and after vacuum treatment to below 0.1 Pa, a modified gas source is introduced at a flow rate of 2000 ml / min, wherein the modified gas source is a mixed gas of hydrogen, argon and ammonia with a volume ratio of 1:1:0.03; after the pressure in the reaction chamber is controlled to 1500 Pa by a vacuum pump, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -200 V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to maintain it at 1500 Pa, and the timing reaction is started. The reaction time is 24 hours, and the reaction temperature is controlled between 400°C and 450°C to obtain a modified product.

[0248] The negative electrode material obtained in Comparative Example 4 has the following characteristics: median particle size of 5.03 μm, carbon content of 5.55 wt%, and tap density of 0.98 g / cm 3 , moisture content is 0.20%, pH=9.38, specific surface area is 1.79m2 / g.

[0249] In addition, the negative electrode material obtained in Comparative Example 4 was as well as There is one pore volume characteristic peak in each pore size range.

[0250] Comparative Example 5

[0251] A method for preparing a negative electrode material comprises the following steps:

[0252] The difference from Example 2 is that:

[0253] (2) The precursor is placed on the bias voltage platform in the plasma reaction chamber, and after vacuum treatment to below 0.1 Pa, a modified gas source is introduced at a flow rate of 2000 ml / min, wherein the modified gas source is a mixed gas of hydrogen, argon, ammonia, hydrogen sulfide and carbon tetrafluoride, with a volume ratio of 1:1:0.01:0.03:0.01; after the pressure in the reaction chamber is controlled to 2000 Pa by a vacuum pump, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -200 V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to maintain it at 2000 Pa, and the timing reaction is started. The reaction time is 24 hours, and the reaction temperature is controlled between 400°C and 450°C to obtain a modified product.

[0254] The negative electrode material obtained in Comparative Example 5 has the following characteristics: median particle size of 5.58 μm, carbon content of 5.65 wt%, and tap density of 0.98 g / cm 3 , moisture content is 0.18%, pH=9.7, specific surface area is 2.18m 2 / g.

[0255] In addition, the negative electrode material obtained in Comparative Example 5 as well as There is one pore volume characteristic peak in each pore size range.

[0256] Comparative Example 6

[0257] A method for preparing a negative electrode material comprises the following steps:

[0258] The difference from Example 2 is that:

[0259] (2) The precursor is placed on the bias voltage platform in the plasma reaction chamber, and after vacuum treatment to below 0.1 Pa, a modified gas source is introduced at a flow rate of 4000 ml / min, wherein the modified gas source is a mixed gas of hydrogen, argon, ammonia and carbon tetrafluoride, with a volume ratio of 1:1:0.05:0.02; after the pressure in the reaction chamber is controlled to 3000 Pa by a vacuum pump, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -200 V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to maintain it at 3000 Pa, and the timing reaction is started. The reaction time is 24 hours, and the reaction temperature is controlled between 450°C and 500°C to obtain a modified product.

[0260] The negative electrode material obtained in Comparative Example 6 has the following characteristics: median particle size of 5.6 μm, carbon content of 4.96 wt%, and tap density of 0.98 g / cm 3 , moisture content is 0.22%, pH=9.83, specific surface area is 1.90m 2 / g.

[0261] In addition, the negative electrode material obtained in Comparative Example 6 as well as There is one pore volume characteristic peak in each pore size range.

[0262] Comparative Example 7

[0263] A method for preparing a negative electrode material comprises the following steps:

[0264] The difference from Example 2 is that:

[0265] (2) The precursor is placed on the bias voltage platform in the plasma reaction chamber, and after vacuum treatment to below 0.1 Pa, a modified gas source is introduced at a flow rate of 1500 ml / min, wherein the modified gas source is a mixed gas of hydrogen, argon, hydrogen sulfide and carbon tetrafluoride, with a volume ratio of 1:1:0.05:0.01; after the pressure in the reaction chamber is controlled to 1000 Pa by a vacuum pump, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -200 V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to maintain it at 1000 Pa, and the timing reaction is started. The reaction time is 24 hours, and the reaction temperature is controlled between 250°C and 300°C to obtain a modified product.

[0266] The negative electrode material obtained in Comparative Example 7 has the following characteristics: median particle size of 5.14 μm, carbon content of 4.75 wt%, and tap density of 0.98 g / cm 3, moisture content is 0.09%, pH=9.43, specific surface area is 1.68m 2 / g.

[0267] In addition, the negative electrode material obtained in Comparative Example 7 There is a large broad peak within the pore size range.

[0268] Comparative Example 8

[0269] A method for preparing a negative electrode material comprises the following steps:

[0270] The difference from Example 2 is that:

[0271] (2) The precursor is placed on the bias voltage platform in the plasma reaction chamber, and after vacuum treatment to below 0.1 Pa, a modified gas phase source is introduced at a flow rate of 3000 ml / min, wherein the modified gas phase source is a mixed gas of hydrogen, argon and hydrogen sulfide with a volume ratio of 1:1:0.05; after the pressure in the reaction chamber is controlled to 2000 Pa by a vacuum pump, the plasma is turned on to generate plasma light, and at the same time, a bias voltage of -200 V is introduced into the reaction platform in the reaction chamber. After the plasma is stabilized, the pressure in the reaction chamber is further adjusted to maintain it at 2000 Pa, and the timing reaction is started. The reaction time is 24 hours, and the reaction temperature is controlled between 350°C and 450°C to obtain a modified product.

[0272] The negative electrode material obtained in Comparative Example 8 has the following characteristics: median particle size of 5.37 μm, carbon content of 4.96 wt%, and tap density of 0.98 g / cm 3 , moisture content is 0.20%, pH=9.61, specific surface area is 1.93m 2 / g.

[0273] In addition, the negative electrode material obtained in Comparative Example 8 There is a large broad peak within the pore size range.

[0274] The negative electrode materials prepared in Examples 1-9 and Comparative Examples 1-8 have sample numbers S1-S9 and R1-R8 in Tables 1 and 2, respectively.

[0275] Table 1: Content and ratio of non-metallic elements in negative electrode materials corresponding to Examples 1-9 and Comparative Examples 1-8

[0276] Table 2: Electrochemical performance characterization of the negative electrode materials prepared in Examples 1-9 and Comparative Examples 1-8

[0277] In combination with Table 1 and Table 2, by comparing Examples 1-9 with Comparative Examples 1-8, it can be concluded that by using plasma-enhanced chemical vapor deposition to modify the surface of the negative electrode material and regulating the mass content ratio of hydrogen to nitrogen, sulfur and halogen elements in the negative electrode material, the capacity, first coulombic efficiency, powder conductivity, cycle performance and rate performance of the negative electrode material can be improved.

[0278] Specifically, by comparing Example 1 with Comparative Example 1, it can be concluded that by using plasma-enhanced chemical vapor deposition to modify the surface of the negative electrode material and regulating the mass content ratio of hydrogen to nitrogen, sulfur and halogen elements in the negative electrode material, the capacity, first coulombic efficiency, powder conductivity, cycle performance and rate performance of the negative electrode material can be comprehensively improved.

[0279] By comparing Comparative Examples 2-8 with Example 2, it can be seen that in order to significantly improve the capacity, initial coulombic efficiency, powder conductivity, cycle performance and rate performance of the negative electrode material, the mass content ratio of hydrogen element to nitrogen element, sulfur element and halogen element in the negative electrode material needs to be controlled within an appropriate range.

[0280] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A negative electrode material, characterized in that, It includes a silicon-based active material and a matrix material, The negative electrode material contains hydrogen element, halogen element, nitrogen element and sulfur element. Among them, the mass content of hydrogen element is m H , the mass content of halogen element is m X , the mass content of sulfur element is m S , the mass content of nitrogen element is m N , and the following relationships are satisfied: 0.02 ≤ m X / m H ≤ 5.00, 0.02 ≤ m N / m H ≤ 20.00, 0.05 ≤ m S / m H ≤ 5.

00.

2. The negative electrode material according to claim 1, wherein The negative electrode material satisfies at least one of the following characteristics: (1) The matrix material is formed on at least part of the surface of the silicon-based active material; (2) The silicon-based active material is formed on the surface of the matrix material; And (3) The silicon-based active material and the matrix material are dispersed with each other.

3. The negative electrode material according to claim 1, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) The negative electrode material contains pores; and (2) In the pore volume distribution curve of the negative electrode material, the pore diameter is and There is a pore volume characteristic peak within the range.

4. The negative electrode material according to claim 1, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) In the negative electrode material, 50 mg / kg ≤ m X ≤ 1500 mg / kg; (2) In the negative electrode material, 100 mg / kg ≤ m N ≤ 4000 mg / kg; And (3) In the negative electrode material, 10 mg / kg ≤ m S ≤ 200 mg / kg.

5. The negative electrode material according to claim 1, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) The silicon-based active material includes at least one of elemental silicon, silicon oxide, silicon alloy, and silicate; and (2) The silicon-based active material includes silicon oxide, and the general formula of the silicon oxide is SiO x , where 0 < x ≤ 2.

6. The negative electrode material according to claim 1, characterized in that The negative electrode material satisfies at least one of the following characteristics: (1) The silicon-based active material includes a doped metal M, and M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu, and Mn; and (2) The silicon-based active material includes a doped metal M, and the mass content of metal M in the negative electrode material is 0 wt% to 15 wt%, and does not include 0 wt%.

7. The negative electrode material according to claim 1, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) The matrix material includes a carbon material, or a mixture of a carbon material and an inorganic oxide; (2) The matrix material includes a carbon material, and the carbon material includes at least one of graphite, graphene, amorphous carbon, diamond-like carbon, carbon nanotubes, and carbon fibers; And (3) The matrix material includes a carbon material, and the carbon material forms a carbon layer by forming on at least part of the surface of the silicon-based active material, and the thickness of the carbon layer is 20 nm - 1000 nm.

8. The negative electrode material according to claim 7, characterized in that, Based on the mass of the negative electrode material, the mass content of carbon element in the negative electrode material is 0.5 wt% to 15 wt%.

9. The negative electrode material according to claim 1, characterized in that, The median particle size of the negative electrode material is 2.0 μm to 12.0 μm.

10. The negative electrode material according to claim 1, characterized in that, The specific surface area of the negative electrode material is 0.50 m 2 / g to 10.00 m 2 / g.

11. The negative electrode material according to claim 1, characterized in that, The tap density of the negative electrode material is 0.75 g / cm 3 ~1.35 g / cm 3 .

12. The negative electrode material according to claim 1, characterized in that, The negative electrode material satisfies at least one of the following characteristics: (1) The powder conductivity of the negative electrode material under 20 kN pressure is 0.01 S / cm to 100.00 S / cm; (2) The mass content of water in the negative electrode material is 0.01 wt% to 0.80 wt%; and (3) The pH of the negative electrode material is 6.00 to 12.

00.

13. A method for preparing a negative electrode material, characterized in that, It includes the following steps: Prepare a precursor, and the precursor includes a silicon-based active material and a matrix material; and Under a modified gas-phase source environment, the precursor is surface-modified by plasma-enhanced chemical vapor deposition to obtain a negative electrode material, wherein the modified gas-phase source includes hydrogen element, sulfur element, nitrogen element and halogen element; in the negative electrode material, the mass content of hydrogen element is m H , the mass content of halogen element is m X , the mass content of sulfur element is m S , the mass content of nitrogen element is m N , and the following relationships are satisfied: 0.02 ≤ m X / m H ≤ 5.00, 0.02 ≤ m N / m H ≤ 20.00, 0.05 ≤ m S / m H ≤ 5.

00.

14. A secondary battery, characterized in that, It includes the negative electrode material according to any one of claims 1 - 12, or the negative electrode material prepared by the preparation method according to claim 13.

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