Negative electrode material and battery

Abstract

A negative electrode material and a battery. The negative electrode material comprises a carbon matrix and a silicon material. When the negative electrode material is tested by means of Raman spectroscopy, the negative electrode material has a first characteristic peak at 520±10 cm-1, the peak intensity of the first characteristic peak being IA, the negative electrode material has a second characteristic peak at 960±10 cm-1, the peak intensity of the second characteristic peak being IB, and the negative electrode material has a third characteristic peak at 480±10 cm-1, the peak intensity of the third characteristic peak being IC, wherein IA, IB and IC have the following relationship: 0.3≤IA / (IB+IC)≤0.6. The negative electrode material has high initial coulombic efficiency, high reversible capacity and high expansion resistance.

Description

Anode materials and batteries

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed on February 7, 2024, with application number 202410176215.2 and titled “Negative Electrode Materials and Batteries.” Technical Field

[0003] The present invention belongs to the technical field of negative electrode materials, and in particular relates to a negative electrode material and a battery. Background Art

[0004] Lithium-ion batteries are widely used in electric vehicles and consumer electronics due to their high energy density, long cycle life, low environmental impact, and lack of memory effect. However, the low theoretical specific capacity of conventional carbon-based anodes (372 mAh / g) has limited their widespread use. To increase the energy density of lithium-ion batteries, researchers are searching for high-capacity anode materials. Silicon-based anode materials, with their theoretical specific capacity reaching 4200 mAh / g, have become a research hotspot.

[0005] However, silicon-based anode materials experience significant volume expansion during the lithium alloying process, and this significant volume expansion poses a challenge to the structural stability of the material. Furthermore, as the charge and discharge cycles of batteries prepared with these materials progress, silicon-based anode materials can experience attenuation mechanisms such as pulverization, loss of contact with the conductive agent and current collector, and the formation of an unstable solid electrolyte interface (SEI), leading to degradation of the electrochemical performance of the anode materials. Carbon matrices (including non-carbon matrices) have excellent electrical conductivity and mechanical properties. Their composite with silicon can not only effectively mitigate volume expansion, but also improve electrode conductivity and produce a stable SEI film. Silicon-carbon composites were the first commercialized silicon-based anode materials, shortening the Li+ transport distance and improving the material's kinetic properties.

[0006] However, during the vapor deposition process, the size of the silicon-based particles is determined by the pore size of the carbon matrix. Ideally, the silicon-based primary particles are deposited within the pores of the carbon matrix, and no silicon-based particles are deposited on the surface of the carbon matrix. However, in reality, silicon-based particles are deposited on the surface of the carbon matrix to a greater or lesser extent. These exposed silicon-based particles can lead to electrolyte decomposition and thickening of the SEI film on the surface of the negative electrode material, resulting in irreversible loss of active lithium ions and, in turn, deterioration of the electrochemical performance of the negative electrode material.

[0007] Summary of the Invention

[0008] The present application provides a negative electrode material and a battery, which can reduce the excessive local volume change of the negative electrode material caused by uneven stress during the cycle, and can also enhance the structural stability of the negative electrode material, and significantly improve the first coulombic efficiency and capacity of the negative electrode material.

[0009] In a first aspect, the present application provides a negative electrode material, wherein the negative electrode material includes a carbon matrix and a silicon material; or the negative electrode material includes a non-carbon matrix and a silicon material.

[0010] The negative electrode material was tested by Raman spectroscopy. -1 There is a first characteristic peak at the position, and the peak intensity of the first characteristic peak is I A ; at 960±10cm -1 There is a second characteristic peak at the position, and the peak intensity of the second characteristic peak is I B ; at 480±10cm -1 There is a third characteristic peak at the position, and the peak intensity of the third characteristic peak is 1 C , then I A , I B , I C The following relationship exists: 0.3≤I A / (I B +I C In some implementations, the peak intensity can be characterized by peak height.

[0011] In some embodiments, the negative electrode material is tested using Raman spectroscopy, and the negative electrode material is detected at 1350±10 cm -1 There is a characteristic peak D at the position, and the peak intensity of the characteristic peak D is I D , at 1580±10cm -1 There is a characteristic peak G at the position, and the peak intensity of the characteristic peak G is I G , 1≤I D / I G In some implementations, the peak intensity can be characterized by peak area.

[0012] In some embodiments, the negative electrode material and the negative electrode material after the silicon material is removed are tested by N2 adsorption-desorption method, and the ratio of the volume of nitrogen adsorbed by the negative electrode material at 90% partial pressure to the volume of nitrogen adsorbed at 10% partial pressure is A, 1.3≤A≤2.5;

[0013] The ratio of the volume of nitrogen adsorbed by the negative electrode material after the silicon material is removed at a 90% partial pressure to the volume of nitrogen adsorbed at a 10% partial pressure is B, 1≤B≤1.9; and A / B>1.

[0014] In some embodiments, the total pore volume of the negative electrode material after removing the silicon material is Q0 cm 3 / g, the total pore volume of the negative electrode material is Q1 cm 3 / g, 0.1≤Q0-Q1≤2.0.

[0015] In some embodiments, the total pore volume of the negative electrode material after removing the silicon material is Q0 cm 3 / g, 0.2≤Q0≤2.0.

[0016] In some embodiments, the total pore volume of the negative electrode material is Q1 cm 3 / g, 0.001≤Q1≤0.1.

[0017] In some embodiments, the mass content of hydrogen element in the negative electrode material after removing the silicon material is 0.01 wt % to 5 wt %.

[0018] In some embodiments, the mass content of oxygen in the negative electrode material after removing the silicon material is 0.01 wt % to 10 wt %.

[0019] In some embodiments, the mass content of nitrogen in the negative electrode material after removing the silicon material is 0.01 wt % to 0.5 wt %.

[0020] In some embodiments, the negative electrode material after the silicon material is removed has pores, and the volume of pores with a pore diameter of 5 nm or less accounts for ≥90% of all pores.

[0021] In some embodiments, the negative electrode material further includes active particles, and the active particles include at least one of Li, Na, K, Sn, Ge, Fe, Mg, Ti, Zn, Al, P, and Cu.

[0022] In some embodiments, the silicon material includes at least one of amorphous silicon, crystalline silicon, silicon oxide, silicon alloy, and a composite of crystalline silicon and amorphous silicon.

[0023] In some embodiments, the silicon material includes amorphous silicon.

[0024] In some embodiments, the average particle size of the silicon material is 1 nm to 100 nm.

[0025] In some embodiments, the total pore volume of the negative electrode material is 0.001 cm 3 / g~0.1cm 3 / g.

[0026] In some embodiments, the mass proportion of oxygen in the negative electrode material is ≤5 wt %.

[0027] In some embodiments, the mass percentage of carbon element in the negative electrode material is 40 wt% to 60 wt%.

[0028] In some embodiments, the mass of silicon in the negative electrode material accounts for 40 wt% to 60 wt%.

[0029] In some embodiments, the specific surface area of ​​the negative electrode material is 0.5 m 2 / g~10m 2 / g.

[0030] In some embodiments, the compacted density of the negative electrode material is 0.8 g / cm 3 ~1.3g / cm 3 .

[0031] In some embodiments, the tap density of the negative electrode material is 0.5 g / cm 3 ~1.5g / cm 3 .

[0032] In some embodiments, the gas production of the negative electrode slurry prepared from the negative electrode material after being placed in a 25° C. environment for 24 hours is ≤0.5 mL / g, and the gas production of the negative electrode slurry prepared from the negative electrode material after being placed in a 45° C. environment for 24 hours is ≤2 mL / g.

[0033] In a second aspect, the present application provides a battery, comprising the negative electrode material described in the first aspect.

[0034] Compared with the prior art, the present invention has at least the following beneficial effects:

[0035] The negative electrode material provided in this application has a first characteristic peak that can be used to characterize the resonant vibration peak between Si-Si atoms (i.e., unoxidized Si). Its peak intensity (e.g., height) and shape can reflect the crystal structure and impurity content of the active material. When the first characteristic peak deviates, it can reflect the stress distribution on the surface of the Si single crystal. The second characteristic peak is used to characterize the Si-O-Si vibration peak, which represents the structure and quality of silicon oxide; the third characteristic peak is used to characterize the Si-O vibration peak, which represents the thickness and quality of the oxide layer on the surface of the silicon particles. By controlling 0.3≤I A / (I B +I C)≤0.6, which can ensure that the degree of oxidation on the surface of the silicon particles in the negative electrode material is controlled within a reasonable range. The appropriate amount of oxide on the surface of the silicon particles can reduce the side reactions caused by the contact between silicon and the electrolyte, and can also prevent excessive oxides from affecting the specific capacity and initial coulombic efficiency of the negative electrode material. In addition, the appropriate amount of oxide on the surface of the silicon material can play a passivation role, which can reduce the side reactions between the exposed Si and the aqueous solution during the subsequent electrode slurrying process and reduce the gas production problem. The negative electrode material provided by this application can have excellent electrochemical properties, improve the cycle stability of the negative electrode material, and reduce gas production. DETAILED DESCRIPTION

[0036] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] An embodiment of the present application provides a negative electrode material, which includes a carbon matrix and a silicon material; or, the negative electrode material includes a non-carbon matrix and a silicon material.

[0041] The negative electrode material was tested by Raman spectroscopy. -1 There is a first characteristic peak at the position, and the peak intensity of the first characteristic peak is I A ; at 960±10cm -1 There is a second characteristic peak at the position, and the peak intensity of the second characteristic peak is I B ; at 480±10cm -1 There is a third characteristic peak at the position, and the peak intensity of the third characteristic peak is 1 C , then I A , I B , IC The following relationship exists: 0.3≤I A / (I B +I C )≤0.6. Peak intensity can be characterized in a variety of ways. In some embodiments, the peak intensity can be characterized using peak height.

[0042] In the above scheme, the first characteristic peak can be used to characterize the resonant vibration peak between Si-Si atoms (i.e., unoxidized Si), and its peak intensity (such as height) and shape can reflect the crystal structure and impurity content of the active material. When the first characteristic peak deviates, it can reflect the stress distribution on the surface of the Si single crystal. Specifically, if there is stress in the object, certain spectral bands that are sensitive to stress will move and deform. Within the elastic range, the change in Raman peak frequency shift is proportional to the stress. When subjected to compressive stress, the spectral band shifts toward the high frequency direction. On the contrary, when subjected to tensile stress, the spectral band shifts toward the low frequency direction. The second characteristic peak is used to characterize the Si-O-Si vibration peak, which represents the structure and quality of silicon oxide; the third characteristic peak is used to characterize the Si-O vibration peak, which represents the thickness and quality of the oxide layer on the surface of the silicon particles. By controlling 0.3≤I A / (I B +I C )≤0.6, which can ensure that the degree of oxidation on the surface of the silicon particles in the negative electrode material is controlled within a reasonable range. The appropriate amount of oxide on the surface of the silicon particles can reduce the side reactions caused by direct contact between silicon and the electrolyte, and can also reduce the impact of excessive oxides on the specific capacity and initial coulombic efficiency of the negative electrode material; and the appropriate amount of oxide on the surface of the silicon material can play a passivation role, which can reduce the side reactions between the exposed Si and the aqueous solution during the subsequent electrode slurrying process, thereby reducing the gas production problem of the negative electrode material. The negative electrode material provided in this application can have excellent electrochemical properties, improve the cycle stability of the battery prepared by the negative electrode material, and reduce the gas production problem of the negative electrode material.

[0043] In some embodiments, the carbon matrix includes an amorphous carbon material and a graphitized carbon material.

[0044] In some embodiments, the non-carbon matrix includes at least one of metal oxides, silicides, silicates, phosphates, titanates, and aluminum borates. It is understandable that the non-carbon matrix adopts the above materials, which can all play the role of supporting the skeleton, and compared with the existing conductive carbon matrix, the non-carbon matrix adopted in this application has better strength and rigidity, so that the negative electrode material can have a higher compaction density during the battery preparation process, which can improve the structural stability of the negative electrode material, reduce the particle breakage and pulverization of the negative electrode material, and help improve the cycle performance of the negative electrode material. At the same time, the non-carbon matrix usually has good ionic conductivity due to its electronic insulation, and can play a role similar to that of an artificial SEI film, which can slow down the subsequent formation of a natural SEI film, reduce the direct contact between the negative electrode material and the electrolyte, and reduce the occurrence of side reactions. In addition, non-carbon matrices have a lower cost advantage than carbon matrices. Due to the complexity of the activation and pore-forming process, the existing carbon matrices involve high energy consumption and environmental costs. If porous ceramics and other materials with naturally porous pores are used, the complex pore-forming process can be omitted, and the cost can be reduced to 10% of the cost of porous carbon or even lower.

[0045] In some embodiments, the metal oxide includes at least one of aluminum oxide, zirconium oxide, germanium dioxide, and manganese dioxide.

[0046] In some embodiments, the silicide includes at least one of silicon carbide and silicon nitride.

[0047] In some embodiments, the silicate includes at least one of cordierite, mullite, and zeolite. It is understandable that the silicate of the present application is mainly a natural silicate mineral, wherein cordierite (magnesium aluminum silicate) has a chemical formula of Mg2Al4Si5O18, which may contain elements such as Na, K, Ca, Fe, Mn, and H2O; mullite has a chemical formula of 3Al2O3-2SiO2; zeolite (aluminosilicate) has a chemical formula of AmBpO2p.nH2O, wherein A represents a cation, typically including a monovalent or divalent metal ion such as Ca, Na, K, Ba, Sr, B represents the basic unit constituting the zeolite framework structure, i.e., Si and Al atoms, p is the cation valence, m is the number of cations A, and n is the number of water molecules.

[0048] In some embodiments, the phosphate includes at least one of aluminum phosphate, magnesium phosphate, calcium phosphate, titanium phosphate, chromium phosphate, cobalt phosphate, nickel phosphate, germanium phosphate, zirconium phosphate, niobium phosphate, molybdenum phosphate, tantalum phosphate, tungsten phosphate, and lanthanum phosphate.

[0049] In some embodiments, the titanate includes at least one of calcium titanate, iron titanate, lithium titanate, and barium titanate.

[0050] In some embodiments, the negative electrode material is tested using Raman spectroscopy, and the negative electrode material is detected at 1350±10 cm -1 There is a characteristic peak D at the position, and the peak intensity of the characteristic peak D is I D , at 1580±10cm -1 There is a characteristic peak G at the position, and the peak intensity of the characteristic peak G is I G , 1≤I D / I G ≤3.5. In some embodiments, the peak intensity here can be characterized by peak area. D / I G The specific values ​​can be 1.0, 1.2, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.2, 2.4, 2.5, 2.6, 2.8, 3.0, 3.2 or 3.5, etc. Of course, it can also be other values ​​within the above range, which is not limited here. D / I G The ratio of is controlled within the above range, which is conducive to achieving a balance between the graphitized carbon material and the amorphous carbon material, so that the negative electrode material can have both the ductility of the graphitized material and the toughness of the amorphous carbon material. It can also use the amorphous carbon material to improve the electronic conductivity of the negative electrode material and enhance the lithium ion transmission efficiency. It can be understood that in the Raman spectrum, the D band of the carbon material (1350±10cm -1 ) reflects the disordered structure of carbon materials (amorphous carbon materials), G band (1580±10cm -1 ) and the sp 2 The vibration of bonded carbon atoms is related to the vibration of bonded carbon atoms, reflecting the ordered structure of carbon materials (i.e. graphitized carbon materials). D / I G The ratio of can reflect the degree of defects in the carbon coating.

[0051] In some embodiments of the present application, the negative electrode material is added to a concentrated nitric acid with a mass fraction of 68% and soaked for 1 hour, and then a 20% mass fraction HF acid solution is dripped dropwise into the negative electrode material, which will produce yellow smoke. The dripping is repeated several times until no yellow smoke is produced in the solution; finally, the residue is digested with a concentrated nitric acid with a mass fraction of 68%, and then washed and dried to obtain the negative electrode material after the silicon material is removed. Alternatively, in other embodiments, taking the active material as silicon material as an example, 150mL of a 20% mass fraction HF acid solution is dripped dropwise into 10g of the negative electrode material under stirring, SiF4 and H2 gas are generated and heat is released. After no gas is generated, the supernatant acid solution is removed by centrifugation, and 150mL of a 20% mass fraction HF acid solution is added to the negative electrode material again. After stirring for 12 hours, the supernatant acid solution is removed again by centrifugation, and then the negative electrode material is washed with pure water until neutral and dried to obtain the negative electrode material after the silicon material is removed, that is, the matrix.

[0052] In some embodiments, the negative electrode material and the negative electrode material after the silicon material is removed are tested by N2 adsorption-desorption method, and the ratio of the volume of nitrogen adsorbed by the negative electrode material at 90% partial pressure to the volume of nitrogen adsorbed at 10% partial pressure is A, 1.3≤A≤2.5;

[0053] The ratio of the volume of nitrogen adsorbed by the negative electrode material after the silicon material is removed at a 90% partial pressure to the volume of nitrogen adsorbed at a 10% partial pressure is B, 1≤B≤1.9; and A / B>1.

[0054] It can be understood that the physical and chemical state of the negative electrode material after the silicon material is removed is close to the physical and chemical state of the carbon matrix before the silicon material is filled, and its porosity is high. The volume of nitrogen adsorbed by the negative electrode material after the silicon material is removed at 90% partial pressure is P 90 The volume of nitrogen adsorbed at 10% partial pressure P 10 The ratio is B, B is between 1 and 1.9; the volume of nitrogen adsorbed by the negative electrode material after filling the silicon material at 90% partial pressure is P 90 The volume of nitrogen adsorbed at 10% partial pressure P 10 The ratio is A, which is between 1.3 and 2.5. Since the silicon material fills a large number of pores in the carbon matrix, especially the micropores, the pore volume of the negative electrode material is significantly reduced, and the pores are mainly mesopores and macropores. The A value is greater than the B value.

[0055] In some embodiments, the total pore volume of the negative electrode material after removing the silicon material is Q0 cm 3 / g, the total pore volume of the negative electrode material is Q1 cm 3 / g, 0.1≤Q0-Q1≤2.0. The value of Q0-Q1 can be 0.1cm 3 / g, 0.5cm 3 / g, 0.6cm 3 / g, 0.8cm 3 / g, 1.0cm 3 / g, 1.3cm 3 / g, 1.5cm 3 / g, 1.8cm 3 / g or 2.0cm 3 / g, etc., of course, it can also be other values ​​within the above range, without limitation. It can be understood that compared with the negative electrode material after removing the silicon material, the pore volume of the negative electrode material containing silicon material is significantly reduced, indicating that the density of the negative electrode material is increased, the silicon material can be effectively filled into the carbon matrix, and the specific capacity of the negative electrode material can be effectively improved. When the value of Q0-Q1 is too small, it means that the content of silicon material filled in the negative electrode material is small, and there are more remaining pores, which increases the specific surface area of ​​the negative electrode material and increases the side reactions of the negative electrode material. When the value of Q0-Q1 is too large, it means that the content of silicon material filled in the negative electrode material is large, and there is no sufficient pore reserved to alleviate the volume expansion of the silicon material, which easily leads to excessive expansion stress of the local silicon material in the negative electrode material, which reduces the cycle stability of the battery prepared by the negative electrode material and aggravates the capacity decay. Preferably, 0.7≤Q0-Q1≤1.5.

[0056] In some embodiments, the total pore volume of the negative electrode material after removing the silicon material is Q0 cm 3 / g, 0.2≤Q0≤2.0; specifically, it can be 0.2cm 3 / g, 0.5cm 3 / g, 0.6cm 3 / g, 0.8cm 3 / g, 1.0cm 3 / g, 1.3cm 3 / g, 1.5cm 3 / g, 1.8cm 3 / g or 2.0cm 3 / g, etc., and of course, it can also be other values ​​within the above range without limitation.

[0057] In some embodiments, the total pore volume of the negative electrode material is Q1 cm 3 / g, 0.001≤Q1≤0.1; the total pore volume of the negative electrode material can be specifically 0.001cm 3 / g, 0.002cm 3 / g, 0.005cm 3 / g, 0.008cm 3 / g, 0.01cm 3 / g, 0.02cm 3 / g, 0.03cm 3 / g, 0.04cm 3 / g, 0.05cm 3 / g, 0.06cm 3 / g, 0.07cm 3 / g, 0.08cm 3 / g, 0.09cm 3 / g or 0.1cm 3 / g, etc., and of course, it can also be other values ​​within the above range, which is not limited here.

[0058] In some embodiments, the pores in the negative electrode material include micropores and mesopores, the pore volume of the micropores accounts for 2% to 50%, and the pore volume of the mesopores accounts for 50% to 98%.

[0059] Specifically, the volume proportion of the micropores in the total pore volume of the negative electrode material is 2% to 50%, and specifically can be 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%, etc., without limitation herein. Preferably, the volume proportion of the micropores in the total pore volume of the negative electrode material is 2% to 15%.

[0060] The volume proportion of mesopores in the total pore volume of the negative electrode material is 50% to 98%, and specifically can be 50%, 60%, 70%, 75%, 80%, 85%, 90%, 92%, 95% or 98%, etc., without limitation herein. Preferably, the volume proportion of mesopores in the total pore volume of the negative electrode material is 85% to 98%.

[0061] It should be noted that the pores in the negative electrode material are mainly mesopores, which are located inside the carbon matrix or are closed pores. On the one hand, these mesopores can provide a buffer space for the expansion of the active material during charging and discharging, and on the other hand, ensure the stress diffusion distribution. When the negative electrode material is used in a lithium-ion battery, it can improve the specific capacity of the negative electrode material, alleviate the volume expansion of the active material, improve the particle strength of the negative electrode material, and reduce the collapse and breakage of the material structure during the rolling or cycling process of the electrode sheet prepared by the negative electrode material. Therefore, under the synergistic effect of the above-mentioned overall structure, the cycle performance and electrochemical performance of the battery prepared by the negative electrode material are improved.

[0062] In some embodiments, the silicon material includes at least one of amorphous silicon, crystalline silicon, silicon oxide, a silicon alloy, and a composite of crystalline silicon and amorphous silicon. Specifically, the silicon alloy may be a silicon-lithium alloy, a silicon-magnesium alloy, or the like. Of course, it should be noted that in some cases, the silicon alloy includes elemental silicon particles and alloys.

[0063] In some embodiments, the silicon material includes amorphous silicon. It is understood that amorphous silicon expands isotropically during lithium insertion, which can reduce the collapse of the pore structure in the negative electrode material, inhibit the rapid decay of the specific capacity of the battery prepared with the negative electrode material, and improve the lithium insertion cycle performance of the battery prepared with the negative electrode material.

[0064] In some embodiments, the average particle size of the silicon material in the negative electrode material is 1 nm to 100 nm, specifically 1 nm, 10 nm, 20 nm, 50 nm, 70 nm, 100 nm, or any value between 1 nm and 100 nm. Preferably, the average particle size of the silicon material in the negative electrode material is 1 nm to 5 nm.

[0065] In some embodiments, the negative electrode material further includes active particles, and the active particles include at least one of Li, Na, K, Sn, Ge, Fe, Mg, Ti, Zn, Al, P, and Cu. The active particles may be a single metal.

[0066] In some embodiments, the active particles may specifically be Sn particles, Ge particles, or Al particles. In other embodiments, the active particles may also be silicon-lithium alloys, silicon-magnesium alloys, etc. Of course, it should be noted that in some cases, the active particles include elemental particles and alloys.

[0067] Specifically, at least a portion of the active particles are filled within the pores of the carbon matrix. As can be understood, the silicon material and active particles filling the pores of the carbon matrix ensure a dispersed distribution of the silicon material, the active particles, and the carbon. This can, on the one hand, increase the specific capacity of the negative electrode material. On the other hand, the pores of the carbon matrix filled with the silicon material and active particles are reduced, which can increase the density of the negative electrode material, effectively reduce the occurrence of side reactions, and further improve the cycle performance of the negative electrode material.

[0068] In some embodiments, the mass content of hydrogen element in the negative electrode material after removing the silicon material is 0.01wt% to 5wt%, specifically 0.01wt%, 0.02wt%, 0.05wt%, 0.08wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%, etc., which is not limited here.

[0069] In some embodiments, the mass content of oxygen element in the negative electrode material after removing the silicon material is 0.01wt% to 10wt%, specifically 0.01wt%, 0.05wt%, 0.08wt%, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%, etc., which is not limited here.

[0070] In some embodiments, the mass content of nitrogen in the negative electrode material after removing the silicon material is 0.01wt% to 0.5wt%, specifically 0.01wt%, 0.02wt%, 0.05wt%, 0.08wt%, 0.1wt%, 0.2wt%, 0.3wt% or 0.5wt%, etc., which is not limited here.

[0071] In some embodiments, the negative electrode material after removing the silicon material has pores, and the volume proportion of pores with a pore diameter of 5 nm or less in all pores is ≥90%. Specifically, the volume proportion of pores with a pore diameter of 5 nm or less in all pores can be 90%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%, etc., which is not limited here. It can be understood that the pores of the carbon matrix are mainly composed of pores below 5 nm. The pore size distribution within this range helps to adjust the size of the silicon material formed during the deposition process, improve the dispersion uniformity of the carbon matrix and the silicon material, and reduce the segregation of the silicon material in the negative electrode material.

[0072] In some embodiments, the mass proportion of oxygen in the negative electrode material is ≤5wt%. Specifically, the mass proportion of oxygen in the negative electrode material can be 0wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, and is not limited here. It is understandable that if the mass content of oxygen is too high, the silicon-based material in the negative electrode material will be partially oxidized. Controlling the mass content of oxygen in the negative electrode material within the above range is beneficial to improving the specific capacity of the negative electrode material and reducing the formation of less active silicon dioxide.

[0073] In some embodiments, the mass percentage of carbon in the negative electrode material is 40 wt% to 60 wt%. Specifically, the mass percentage of carbon in the negative electrode material can be 40 wt%, 45 wt%, 50 wt%, 52 wt%, 53 wt%, 55 wt%, 56.5 wt%, 58 wt%, or 60 wt%, which is not limited here.

[0074] In some embodiments, the mass percentage of silicon in the negative electrode material is 40 wt% to 60 wt%. Specifically, the mass percentage of silicon in the negative electrode material can be 40 wt%, 41 wt%, 45 wt%, 47 wt%, 50 wt%, 52 wt%, 53 wt%, 55 wt%, 56.5 wt%, 58 wt%, or 60 wt%, which is not limited here.

[0075] In some embodiments, the specific surface area of ​​the negative electrode material is 0.5 m 2 / g~10m 2 / g. Specifically, the specific surface area of ​​the negative electrode material can be 0.5m 2 / g、1m 2 / g, 2m 2 / g、4m 2 / g、5m 2 / g、10m 2 / g, etc., and of course, it can also be other values ​​within the above range, which is not limited here.

[0076] In some embodiments, the compacted density of the negative electrode material is 0.8 g / cm 3 ~1.3g / cm 3 , specifically 0.8g / cm 3 , 0.9g / cm 3 , 1.0g / cm 3 , 1.1g / cm 3 , 1.2g / cm 3 or 1.3 g / cm 3 Of course, it can also be other values ​​within the above range, which is not limited here.

[0077] In some embodiments, the tap density of the negative electrode material is 0.5 g / cm 3 ~1.5g / cm 3 , specifically 0.5g / cm 3 , 0.6g / cm 3 , 0.7g / cm 3 , 0.8g / cm 3 , 0.9g / cm 3 , 1.0g / cm 3 , 1.1g / cm 3 , 1.2g / cm 3 , 1.3g / cm 3 , 1.4g / cm 3 or 1.5g / cm 3 Of course, it can also be other values ​​within the above range, which is not limited here.

[0078] In some embodiments, the gas production of the negative electrode slurry prepared from the negative electrode material after being placed in a 25° C. environment for 24 hours is ≤0.5 mL / g, and the gas production of the negative electrode slurry prepared from the negative electrode material after being placed in a 45° C. environment for 24 hours is ≤2 mL / g.

[0079] Understandably, the more exposed silicon material in the negative electrode material, the lower the negative electrode material's conductivity and the more severe the gas production. This is because silicon hydrolyzes in aqueous solution to produce silicates and hydrogen. The present application controls the gas production of the negative electrode slurry within the above range, indicating that the exposed silicon material in the negative electrode material is minimal, effectively controlling the gas production of the negative electrode material.

[0080] Secondly, the present application also provides a method for preparing a negative electrode material using a chemical vapor deposition process. Chemical vapor deposition (CVD) is to place a carbon matrix in one or more precursor gases, and under set temperature and pressure conditions, the precursor gas reacts and / or decomposes on the carbon matrix to produce the desired deposit, thereby obtaining a high-performance negative electrode material.

[0081] S10, in an inert atmosphere, sintering the pretreated coconut shell at a temperature of 600° C. to 900° C. for 0.5 h to 2 h to obtain a carbonized material.

[0082] In some embodiments, the primary sintering temperature is 600°C to 900°C, specifically 600°C, 650°C, 700°C, 750°C, 800°C, 850°C or 900°C, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0083] In some embodiments, the time for one sintering is 0.5 h to 2 h, specifically 0.5 h, 1 h, 1.5 h or 2 h, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0084] S20, mixing the carbonized material with the activating agent, performing activation treatment, and soaking the activated product in an acid solution to obtain a carbon matrix.

[0085] In some embodiments, the activator includes at least one of potassium hydroxide and sodium hydroxide.

[0086] In some embodiments, the mass ratio of the carbonized material to the activator is 1:(1-10), specifically 1:1, 1:2, 1:3, 1:4, 1:5, 1:7, 1:8, 1:9 or 1:10, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0087] In some embodiments, the activation treatment temperature is 800°C to 900°C, specifically 800°C, 820°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C or 900°C, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0088] In some embodiments, the activation treatment time is 2 hours to 6 hours, specifically 2 hours, 3 hours, 3.5 hours, 4 hours, 5 hours or 6 hours, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0089] In some embodiments, the activated product is subjected to acid leaching in an acid solution, followed by solid-liquid separation to obtain a carbon matrix. The acid used for pickling can be hydrochloric acid, nitric acid, or the like. After sufficient pickling, other impurities can be removed. It should be noted that after pickling, the pickled product needs to be ultrasonically cleaned with ethanol or deionized water until the washing water is neutral.

[0090] In some embodiments, the solid-liquid separation includes filtration and drying. The drying time is 1 hour to 10 hours, and the drying temperature is 70° C. to 150° C.

[0091] In the present application, by controlling the process parameters of the activation treatment, such as temperature and time, the activating agent can be effectively utilized to activate and form pores in the carbonized material, so that the carbon matrix has abundant pores.

[0092] In some embodiments, the total pore volume of the carbon matrix is ​​0.2 cm 3 / g~2cm 3 / g; the total pore volume of the carbon matrix can be specifically 0.2cm 3 / g, 0.3cm 3 / g, 0.4cm 3 / g, 0.5cm 3 / g, 0.6cm 3 / g, 0.9cm 3 / g, 1.0cm 3 / g, 1.2cm 3 / g, 1.5cm 3 / g, 1.8cm 3 / g, 1.9cm 3 / g, 1.95cm 3 / g or 2cm 3 / g, etc., and of course other values ​​within the above range are also possible and are not limited here. The sufficient pore volume of the carbon matrix can provide sufficient accommodation space for the silicon material and can also alleviate the volume expansion caused by the silicon material during lithium insertion and extraction, which is beneficial to improving the cycle performance of the negative electrode material.

[0093] In some embodiments, the mass content of hydrogen element in the carbon matrix is ​​0.01wt% to 5wt%, specifically 0.01wt%, 0.02wt%, 0.05wt%, 0.08wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%, etc., which is not limited here.

[0094] In some embodiments, the mass content of oxygen element in the carbon matrix is ​​0.01wt% to 10wt%, specifically 0.01wt%, 0.05wt%, 0.08wt%, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%, etc., which is not limited here.

[0095] In some embodiments, the mass content of nitrogen in the carbon matrix is ​​0.01wt% to 0.5wt%, specifically 0.01wt%, 0.02wt%, 0.05wt%, 0.08wt%, 0.1wt%, 0.2wt%, 0.3wt% or 0.5%, etc., which is not limited here.

[0096] In some embodiments, the ratio of the volume of nitrogen adsorbed by the carbon matrix at 90% partial pressure to the volume of nitrogen adsorbed at 10% partial pressure is A', 1≤A'≤1.9; it can be understood that the carbon matrix has a higher porosity and a relatively small pore size, which is conducive to the deposition of silicon materials.

[0097] In some embodiments, in the carbon matrix, the volume of pores with a pore diameter of 5 nm or less accounts for ≥ 90% of all pores, and may specifically be 90%, 91%, 92%, 93%, 95%, 96%, 98%, or 99%, etc., without limitation herein.

[0098] It can be understood that the pores of the carbon matrix are mainly composed of pores with a pore diameter of less than 5 nm. The pore size distribution within this range helps to regulate the size of the silicon material formed during the deposition process, improve the dispersion uniformity of the carbon matrix and the silicon material, and reduce the segregation of the silicon material.

[0099] In some embodiments, the pores in the carbon matrix include micropores, wherein the volume proportion of the micropores in all pores is ≥80%, and the volume proportion of the pores in the range of 2 nm to 5 nm is 0% to 10%. Specifically, the volume proportion of the micropores in all pores can be 80%, 81%, 82%, 83%, 84%, 85%, 87%, 88%, 90%, 92%, 93%, 95%, 98% or 99%, etc., without limitation herein. The volume proportion of the pores in the range of 2 nm to 5 nm can be 0%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., without limitation herein.

[0100] It can be understood that the pores of the carbon matrix are mainly micropores. The pore size distribution within this range helps to form gas-phase mass transfer channels inside the carbon matrix during the deposition process, improve the internal diffusion environment of the carbon matrix, reduce the density gradient of the carbon matrix, and thus improve the density of the negative electrode material.

[0101] S30, introducing a reaction gas containing a silicon source gas, and performing vapor deposition on the carbon substrate to obtain a negative electrode material.

[0102] In some embodiments, the deposition temperature of the vapor deposition is 400° C. to 650° C. Specifically, the deposition temperature can be 400° C., 420° C., 450° C., 470° C., 490° C., 500° C., 530° C., 550° C., 580° C., 600° C., 610° C., 620° C., 630° C., 640° C., or 650° C., and of course, other values ​​between 400° C. and 650° C. are also possible, and are not limited thereto.

[0103] In some embodiments, the vapor deposition time is 5 to 50 hours. Specifically, the deposition time can be 5 hours, 8 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, or 50 hours, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0104] It can be understood that the process conditions of vapor deposition (such as deposition temperature and deposition time) will affect the deposition of silicon material in the pores of the carbon matrix. Controlling the temperature and time of vapor deposition within the above range can ensure that the reaction gas does not decompose and deposit before entering the pores of the carbon matrix, but quickly decomposes and deposits after entering the pores.

[0105] In some embodiments, vapor deposition is performed under a protective atmosphere.

[0106] In some embodiments, the protective atmosphere includes at least one of nitrogen, argon, helium, neon, krypton, and xenon.

[0107] In some embodiments, the reaction gas includes a raw material for a silicon source gas, and the raw material for the silicon source gas includes at least one of monosilane, disilane, monochlorosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane. It should be noted that when the raw material for the silicon source gas is monosilane, disilane, monochlorosilane, or dichlorosilane, it is gaseous at room temperature; when the raw material for the silicon source gas is trichlorosilane or tetrachlorosilane, it is liquid at room temperature. During the vapor deposition process, the liquid silicon source gas vaporizes and becomes a gaseous silicon source.

[0108] In some embodiments, the flow rate of the silicon source gas is 5 L / min to 20 L / min, specifically 5 L / min, 6 L / min, 8 L / min, 10 L / min, 12 L / min, 15 L / min, 18 L / min or 20 L / min, etc., which is not limited here.

[0109] The present application also provides a battery comprising the above-mentioned negative electrode material. The battery may be an electrochemical device such as a lithium-ion battery or a sodium-ion battery, which is not limited here.

[0110] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0111] Example 1

[0112] (1) The pretreated coconut shell was placed in a tube furnace and calcined at 750 °C for 0.5 h in an inert atmosphere to obtain a carbonized material.

[0113] (2) The carbonized material and KOH powder in a mass ratio of 1:5 were mixed and activated in a nitrogen atmosphere at an activation temperature of 900°C for 6 hours. After activation, the mixture was cooled to room temperature and ground for 0.5 hours. The mixture was placed in deionized water, and then diluted hydrochloric acid (mass fraction of 10 wt%) was added. The mixture was ultrasonically dispersed until uniform, stirred, washed with water until neutral, filtered, vacuum dried at 110°C for 6 hours, and ground thoroughly to obtain a carbon matrix.

[0114] (3) The carbon substrate was placed in a chemical vapor deposition furnace, monosilane was used as the working gas, the deposition temperature was 500°C, the deposition time was 20 hours, and the flow rate of monosilane was 10 L / min to obtain the negative electrode material.

[0115] The negative electrode material prepared in this embodiment includes a carbon matrix and a silicon material. The carbon matrix has pores, and at least a portion of the silicon material is filled in the pores.

[0116] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 1, and the remaining parameters of the negative electrode material are detailed in Table 2.

[0117] Example 2:

[0118] (1) The pretreated coconut shell was placed in a tube furnace and calcined at 600 °C for 2 h in an inert atmosphere to obtain a carbonized material;

[0119] (2) The carbonized material and KOH powder with a mass ratio of 1:5 were activated in a nitrogen atmosphere at an activation temperature of 900°C for 4 hours. After activation, the carbonized material was cooled to room temperature and ground for 0.5 hours. The carbonized material was placed in deionized water, and then diluted hydrochloric acid (mass fraction of 10 wt%) was added. The carbonized material was ultrasonically dispersed until uniform, stirred, washed with water until neutral, filtered, vacuum dried at 110°C for 6 hours, and ground thoroughly to obtain a carbon matrix.

[0120] (3) The carbon substrate was placed in a chemical vapor deposition furnace, monosilane was used as the working gas, the deposition temperature was 400°C, the deposition time was 40 hours, and the flow rate of monosilane was 5 L / min to obtain the negative electrode material.

[0121] The negative electrode material prepared in this embodiment includes a carbon matrix and a silicon material. The carbon matrix has pores, and at least a portion of the silicon material is filled in the pores.

[0122] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 1, and the remaining parameters of the negative electrode material are detailed in Table 2.

[0123] Example 3

[0124] (1) The pretreated coconut shell was placed in a tube furnace and calcined at 900 °C for 1 h in an inert atmosphere to obtain a carbonized material.

[0125] (2) The carbonized material and KOH powder in a mass ratio of 1:4 were mixed and activated in a nitrogen atmosphere at an activation temperature of 900°C for 2 h. After activation, the mixture was cooled to room temperature and ground for 0.5 h, placed in deionized water, and then diluted hydrochloric acid (mass fraction of 10 wt%) was added, ultrasonically dispersed until uniform, stirred and washed with water until neutral, filtered, vacuum dried at 110°C for 6 h, and then ground thoroughly to obtain a carbon matrix.

[0126] (3) The carbon substrate was placed in a chemical vapor deposition furnace, monosilane was used as the working gas, the deposition temperature was 550°C, the deposition time was 10 h, and the flow rate of monosilane was 5 L / min to obtain the negative electrode material.

[0127] The negative electrode material prepared in this embodiment includes a carbon matrix and a silicon material. The carbon matrix has pores, and at least a portion of the silicon material is filled in the pores.

[0128] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 1, and the remaining parameters of the negative electrode material are detailed in Table 2.

[0129] Example 4

[0130] (1) The pretreated coconut shell was placed in a tube furnace and calcined at 750 °C for 1.5 h in an inert atmosphere to obtain a carbonized material.

[0131] (2) The carbonized material and KOH powder in a mass ratio of 1:10 were mixed and activated in a nitrogen atmosphere at an activation temperature of 900°C for 4 hours. After activation, the mixture was cooled to room temperature and ground for 0.5 hours, placed in deionized water, and then diluted hydrochloric acid (mass fraction of 10 wt%) was added, ultrasonically dispersed until uniform, stirred and washed with water until neutral, filtered, vacuum dried at 110°C for 6 hours, and ground thoroughly to obtain a carbon matrix.

[0132] (3) The carbon substrate was placed in a chemical vapor deposition furnace, monosilane was used as the working gas, the deposition temperature was 400°C, the deposition time was 12 h, and the flow rate of monosilane was 6 L / min to obtain the negative electrode material.

[0133] The negative electrode material prepared in this embodiment includes a carbon matrix and a silicon material. The carbon matrix has pores, and at least a portion of the silicon material is filled in the pores.

[0134] The parameters of the negative electrode material after removing the silicon material in this embodiment are detailed in Table 1, and the remaining parameters of the negative electrode material are detailed in Table 2.

[0135] Example 5

[0136] The difference from Example 1 is that:

[0137] (2) The carbonized material and KOH powder were mixed in a mass ratio of 1:8 and activated under a nitrogen atmosphere at an activation temperature of 900 ° C for 20 h. After activation, the mixture was cooled to room temperature and ground for 0.5 h, placed in deionized water, and then diluted hydrochloric acid (mass fraction of 10 wt%) was added, ultrasonically dispersed until uniform, stirred and washed with water until neutral, filtered, vacuum dried at 110 ° C for 6 h, and then ground thoroughly to obtain a carbon matrix.

[0138] Example 5'

[0139] The difference from Example 1 is that:

[0140] (2) The carbonized material and KOH powder were mixed in a mass ratio of 1:8 and activated under a nitrogen atmosphere at an activation temperature of 900 ° C for 6 h. After activation, the mixture was cooled to room temperature and ground for 0.5 h, placed in deionized water, and then diluted hydrochloric acid (mass fraction of 10 wt%) was added, ultrasonically dispersed until uniform, stirred and washed with water until neutral, filtered, vacuum dried at 110 ° C for 6 h, and then ground thoroughly to obtain a carbon matrix.

[0141] Example 6

[0142] The difference from Example 1 is that:

[0143] (3) The carbon substrate was placed in a chemical vapor deposition furnace, monosilane was used as the working gas, the deposition temperature was 600°C, the deposition time was 18 hours, and the flow rate of monosilane was 15 L / min to obtain the negative electrode material.

[0144] Example 7

[0145] The difference from Example 1 is that:

[0146] (3) The carbon substrate was placed in a chemical vapor deposition furnace, monosilane was used as the working gas, the deposition temperature was 550°C, the deposition time was 15 hours, and the flow rate of monosilane was 5 L / min to obtain the negative electrode material.

[0147] Example 8

[0148] The difference from Example 1 is that non-carbon matrix SiC is used.

[0149] Comparative Example 1

[0150] The difference from Example 1 is that:

[0151] (3) The carbon substrate was placed in a chemical vapor deposition furnace, monosilane was used as the working gas, the deposition temperature was 500°C, the deposition time was 55 hours, and the flow rate of monosilane was 10 L / min to obtain the negative electrode material.

[0152] Comparative Example 2

[0153] The difference from Example 1 is that:

[0154] (3) The carbon substrate was placed in a chemical vapor deposition furnace, monosilane was used as the working gas, the deposition temperature was 500°C, the deposition time was 20 hours, and the flow rate of monosilane was 22 L / min to obtain the negative electrode material.

[0155] Comparative Example 3

[0156] The difference from Example 1 is that:

[0157] (3) The carbon substrate was placed in a chemical vapor deposition furnace, monosilane was used as the working gas, the deposition temperature was 500°C, the deposition time was 5 hours, and the flow rate of monosilane was 10 L / min to obtain the negative electrode material.

[0158] Comparative Example 4

[0159] The difference from Example 1 is that:

[0160] (3) The carbon substrate was placed in a chemical vapor deposition furnace, monosilane was used as the working gas, the deposition temperature was 500°C, the deposition time was 20 h, and the flow rate of monosilane was 2 L / min to obtain the negative electrode material.

[0161] Performance Testing

[0162] (1) Etching treatment:

[0163] Add 68% concentrated nitric acid by mass to the negative electrode material and soak it for 1 hour. Then, add 20% HF acid solution by mass to the negative electrode material drop by drop, which will produce yellow smoke. Repeat the addition several times until no yellow smoke is produced in the solution. Finally, use 68% concentrated nitric acid by mass to digest the residue, then wash and dry it to obtain the negative electrode material after removing the silicon material.

[0164] (2) Testing method for the pore volume of the negative electrode material or the negative electrode material after removing the silicon material:

[0165] The test was carried out using the ASAP2460 equipment from American Micromeritics. The pore volume V was calculated using the BJH Desorption cumulative volume of pores model. Calculated within the pore size range.

[0166] Micropore and mesopore analysis was performed using the Micromeretics ASAP 2460. At liquid nitrogen temperature, the equilibrium amount of nitrogen adsorbed on a surface is correlated with properties such as pore size. By combining the relationship between the amount adsorbed and relative pressure during adsorption, various models can be fitted to calculate pore size. The software generates reports using density functional theory (DFT) to calculate pore size distribution, total pore volume, and pore volume within a specific range.

[0167] (3) Method for testing the pore size of the negative electrode material or the negative electrode material after removing the silicon material:

[0168] An appropriate amount of sample particles was taken and the pore diameter was measured under a transmission electron microscope (TEM).

[0169] (4) Raman test of negative electrode materials:

[0170] The Raman spectrum was measured using the Japan HORIBA XPLORA laser confocal Raman spectrometer, including the Raman peak position, peak intensity (including height and area), half-peak width, etc. Specifically, the sample was placed on the sample stage of the Raman spectrometer to ensure that the sample was aligned with the laser beam. The test conditions were: 532nm laser, test range 100cm -1 ~3000cm -1 . Use standard substances to perform zero point calibration to ensure the precision and accuracy of the spectrum. Use laser to excite the sample and measure the frequency and intensity of the scattered light. The peak height test method here is, for example, for the peak at 520±10cm -1 Within range means retrieving the data within that range and comparing the data to find the maximum value of the ordinate and the corresponding abscissa. For example, if the majority of spectra for a sample have a corresponding maximum ordinate at a certain abscissa, the average of the ordinates corresponding to that abscissa at that point in n spectra (n ≥ 15) will be used as the basis for peak calculation. Peak area measurement can be performed using conventional area measurement methods, such as the integration method.

[0171] (5) Gas production value test

[0172] Disperse carboxymethyl cellulose (CMC) in water at a mass ratio of 1.4% for gluing. After uniform dispersion, take 10g of the glue solution and mix it with 10g of the negative electrode material to obtain a slurry. Put the slurry into an aluminum-plastic film bag and record the slurry mass. Then seal it to form a sealed aluminum-plastic film bag.

[0173] The sealed aluminum-plastic film bag was fixed to the bottom of the container and completely immersed in water, and the volume of the aluminum-plastic film bag was recorded. After a fixed time (24 hours), the volume of the aluminum-plastic film bag was recorded again. The gas production of the silicon negative electrode material was calculated based on the volume change of the aluminum-plastic film, unit: mL / g.

[0174] (6) Test method for the mass content of carbon in negative electrode materials:

[0175] Using Germany's Bruker's G4 ICARUS HF infrared carbon and sulfur analyzer: the sample is burned in a high-temperature, oxygen-rich state, and the carbon and sulfur elements it contains are oxidized to carbon dioxide and sulfur dioxide, respectively. The generated gases enter the infrared detector with the carrier gas. By quantitatively analyzing the changes in the carbon dioxide signal and the sulfur dioxide signal, the carbon and sulfur content can be calculated respectively.

[0176] (7) Test method for the mass content of silicon in negative electrode materials:

[0177] Use Nanyang Xinyu SA2-9-17TP box-type atmosphere furnace: burn in an oxygen atmosphere, so that the silicon and silicon oxide in the sample react to form silicon dioxide, and the carbon is burned and converted into carbon dioxide and discharged. The silicon content is calculated by weighing.

[0178] (8) Test method for specific surface area of ​​negative electrode material:

[0179] The specific surface area was measured using a Micromeritics TriStar 3000 surface area and pore size analyzer.

[0180] (9) Test method for tap density of negative electrode material:

[0181] The tap density was tested using a Meconta DAT-6-220 tap density tester. 100 g of sample was weighed and vibrated 3000 times at 300 times / min.

[0182] (10) Test method for particle size of negative electrode material:

[0183] The D50 was measured using a laser particle size analyzer and showed a symmetrical distribution similar to a normal distribution. In the volume-based distribution, the cumulative 50% diameter is D50, and so on, the cumulative 90% diameter is D90, and the cumulative 10% diameter is D10.

[0184] (11) Test method for the mass content of nitrogen, oxygen and hydrogen elements in the negative electrode material after removing the silicon material:

[0185] Using a German Verder ONH 2000 oxygen, nitrogen, and hydrogen analyzer, the sample is melted in an inert atmosphere while surrounded by flux. The oxygen it contains is reduced to carbon dioxide by the carbon in the graphite crucible. The resulting carbon dioxide enters the infrared detector along with the carrier gas. Quantitative statistics of changes in the carbon dioxide signal are used to calculate the oxygen content. The sample is also melted in an inert atmosphere while surrounded by flux. The nitrogen and hydrogen it contains decompose to form stable elemental nitrogen and hydrogen, respectively. The resulting nitrogen and hydrogen gases enter the thermal conductivity detector along with the carrier gas. Quantitative statistics of changes in the thermal conductivity cell heat allow the mass content of the nitrogen and hydrogen to be calculated, respectively.

[0186] (12) Negative electrode material compaction density test:

[0187] Using the American McNor CARVER 4350.22 powder compaction density tester, a sample of specified mass m is placed in a mold and a pressure of 1.0 T is applied. After maintaining the pressure for 30 seconds, the pressure is removed and the thickness is tested to calculate the compaction density.

[0188] (13) pH test of negative electrode material:

[0189] A Mettler-Toledo FE20 pH meter is used. The potential difference measured in the solution by a working electrode cell consisting of a measuring electrode and a reference electrode is converted to pH using an ammeter, utilizing the linear relationship between the pH value of the solution being measured and the potential of the working cell. A 5g sample is dispersed in 30 / 45mL of water, stirred, and ultrasonicated for 5 minutes, followed by 10 minutes of rest before testing.

[0190] (14) Electrochemical performance test

[0191] 1) The first discharge capacity and first coulombic efficiency (ICE) were measured by preparing a negative electrode slurry containing the negative electrode material, conductive carbon black, and polyacrylic acid (PPA) in a mass ratio of 75:15:10. This slurry was then coated onto copper foil and dried to form a negative electrode sheet. A lithium metal sheet was used as the counter electrode, and button cells were assembled in an argon-filled glove box. The cells were charged and discharged at a current density of 0.1C over the 0.01V-5V range to determine their first discharge capacity and first coulombic efficiency (ICE).

[0192] 2) The test method for the capacity retention rate and the electrode thickness expansion rate after 50 cycles is as follows: according to the mass ratio of negative electrode active material, conductive carbon black (Super-P), conductive graphite (KS-6), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) of 92:2:2:2:2, a negative electrode slurry is prepared, coated on copper foil, and dried to form a negative electrode sheet. The negative electrode active material is a mixture of the negative electrode material of the present application and graphite, wherein the proportion of the negative electrode material and graphite is determined by the initial reversible specific capacity of the two and the capacity required to be matched between the two. A button cell is assembled in an argon-filled glove box using a metal lithium sheet as the counter electrode. The button cell is subjected to 50 repeated charge and discharge tests in the charge and discharge range of 0.01V-5V at a current density of 1C to obtain the capacity retention rate and the electrode thickness expansion rate after 50 cycles of the battery.

[0193] Table 1. Parameters of negative electrode materials after removing silicon material

[0194] Table 2. Parameters of negative electrode materials

[0195] Table 3. Performance test results of examples and comparative examples

[0196] According to the results shown in Tables 1 to 3, by controlling I A / (I B +I C ) ratio, the degree of oxidation on the surface of the silicon particles in the negative electrode material can be controlled within a reasonable range. The appropriate amount of oxide on the surface of the silicon particles can reduce the side reactions caused by the contact between silicon and the electrolyte, and can also reduce the effects of excessive oxides on the specific capacity and initial coulombic efficiency of the battery prepared with the negative electrode material. The appropriate amount of oxide on the surface of the silicon material can play a passivation role, which can reduce the side reactions between the exposed Si and the aqueous solution in the subsequent slurrying process of the negative electrode material to prepare the electrode sheet, thereby reducing the gas production problem of the negative electrode material. The negative electrode material provided by the present application can have excellent electrochemical properties, improve the cycle stability of the negative electrode material, and reduce the gas production of the negative electrode material.

[0197] Compared with Example 1, in Example 4 and Example 5, during the preparation process, the ratio of carbonized material to activator is reduced, that is, the amount of activator added is increased, the pores of the obtained carbon matrix are more sufficient, and the total pore volume of the carbon matrix is ​​increased; the carbon matrix has more space for filling silicon material, thereby improving the specific capacity of the negative electrode material and the first coulombic efficiency is also improved.

[0198] Compared with Example 1, in Example 7, during the preparation process, the flow rate of monosilane and the deposition time are reduced, the amount of silicon material deposited in the carbon matrix decreases, the pore volume difference between the negative electrode material after removing the silicon material and the negative electrode material containing the silicon material is reduced, and the pores in the carbon matrix are not fully filled. Although the cycle performance of the negative electrode material is improved, the specific capacity of the battery prepared with the negative electrode material is reduced compared with Example 1.

[0199] Comparative Example 1 Compared with Example 1, during the preparation process, the silicon material vapor deposition time is increased, the mass content of the silicon material in the negative electrode material is increased, the specific capacity of the battery prepared by the negative electrode material is further improved, and the silicon material on the surface of the negative electrode material is increased. A The intensity of I A / (I B +I C ) is too large, resulting in insufficient oxidation of the silicon material on the surface of the negative electrode material. During the subsequent slurrying process for preparing the electrode sheet, a side reaction occurs between the exposed Si in the negative electrode material and the aqueous solution, significantly increasing gas production. This significantly increases the expansion rate of the electrode sheet prepared with the negative electrode material, and the cycle performance of the battery prepared with the negative electrode material is reduced.

[0200] Comparative Example 2 Compared with Example 1, during the preparation process, the flow rate of monosilane is increased, the vapor deposition time is increased, the mass content of the silicon material in the negative electrode material is increased, the specific capacity of the battery prepared by the negative electrode material is further improved, and the silicon material on the surface of the negative electrode material is increased. A The intensity of I A / (I B +I C ) is too large, resulting in insufficient oxidation of the silicon material on the surface of the negative electrode material. During the subsequent slurrying process for preparing the electrode sheet, a side reaction occurs between the exposed Si in the negative electrode material and the aqueous solution, significantly increasing gas production. This significantly increases the expansion rate of the electrode sheet prepared with the negative electrode material, and the cycle performance of the battery prepared with the negative electrode material is reduced.

[0201] Comparative Example 3 Compared with Example 1, during the preparation of the negative electrode material, the vapor deposition time of the silicon material was insufficient, the mass content of the silicon material in the negative electrode material was reduced, the specific capacity of the battery prepared from the negative electrode material was further reduced, the silicon material in the negative electrode material was reduced, and there was no obvious Si-Si bond. A The intensity of I A / (I B +I C ) is too small, the specific capacity and first coulombic efficiency of the battery prepared by the negative electrode material decrease due to the reduction of silicon content in the negative electrode material.

[0202] Similarly, in Comparative Example 4, compared with Example 1, during the preparation process, the flow rate of monosilane is smaller, the mass content of the silicon material in the negative electrode material is reduced, the specific capacity of the battery prepared by the negative electrode material is further reduced, the silicon material in the negative electrode material is reduced, and there is no obvious Si-Si bond. A The intensity of I A / (I B +I C ) is too small, the specific capacity and first coulombic efficiency of the battery prepared by the negative electrode material decrease due to the reduction of silicon content in the negative electrode material.

[0203] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the scope of the present application shall be included within the scope of protection of the present application.

Claims

1. A negative electrode material, characterized in that The negative electrode material includes a carbon matrix and a silicon material, or the negative electrode material includes a non-carbon matrix and a silicon material; The negative electrode material was tested by Raman spectroscopy. -1 There is a first characteristic peak at the position, and the peak intensity of the first characteristic peak is I A ; at 960±10cm -1 There is a second characteristic peak at the position, and the peak intensity of the second characteristic peak is I B ; at 480±10cm -1 There is a third characteristic peak at the position, and the peak intensity of the third characteristic peak is 1 C , then I A , I B , I C The following relationship exists: 0.3≤I A / (I B +I C )≤0.

6.

2. The negative electrode material according to claim 1, characterized in that The negative electrode material was tested by Raman spectroscopy. -1 There is a characteristic peak D at the position, and the peak intensity of the characteristic peak D is I D , at 1580±10cm -1 There is a characteristic peak G at the position, and the peak intensity of the characteristic peak G is I G , 1≤I D / I G ≤3.

5.

3. The negative electrode material according to claim 1, characterized in that The negative electrode material and the negative electrode material after the silicon material is removed are tested by N2 adsorption-desorption method. The ratio of the volume of nitrogen adsorbed by the negative electrode material at 90% partial pressure to the volume of nitrogen adsorbed at 10% partial pressure is A, and 1.3≤A≤2.5; The ratio of the volume of nitrogen adsorbed by the negative electrode material after the silicon material is removed at 90% partial pressure to the volume of nitrogen adsorbed at 10% partial pressure is B, 1≤B≤1.9; and A / B>1.

4. The negative electrode material according to claim 1, characterized in that The negative electrode material meets at least one of the following technical characteristics: (1) The total pore volume of the negative electrode material after removing the silicon material is Q0cm 3 / g, the total pore volume of the negative electrode material is Q1cm 3 / g, 0.1≤Q0-Q1≤2.0; (2) The total pore volume of the negative electrode material after removing the silicon material is Q0cm 3 / g, 0.2≤Q0≤2.0; (3) The total pore volume of the negative electrode material is Q1cm 3 / g, 0.001≤Q1≤0.

1.

5. The negative electrode material according to any one of claims 1 to 4, characterized in that The negative electrode material after removing the silicon material satisfies at least one of the following characteristics: (1) The mass content of hydrogen in the negative electrode material after removing the silicon material is 0.01wt% to 5wt%; (2) The mass content of oxygen in the negative electrode material after removing the silicon material is 0.01 wt% to 10 wt%; (3) The mass content of nitrogen in the negative electrode material after removing the silicon material is 0.01 wt% to 0.5 wt%.

6. The negative electrode material according to any one of claims 1 to 5, characterized in that The negative electrode material after removing the silicon material has pores, and the volume proportion of pores with a pore diameter of less than 5 nm in all pores is ≥90%.

7. The negative electrode material according to any one of claims 1 to 6, characterized in that The negative electrode material further includes active particles, and the active particles include at least one of Li, Na, K, Sn, Ge, Fe, Mg, Ti, Zn, Al, P and Cu.

8. The negative electrode material according to claim 1, characterized in that The silicon material meets at least one of the following technical characteristics: (1) The silicon material includes at least one of amorphous silicon, crystalline silicon, silicon oxide, silicon alloy, and a composite of crystalline silicon and amorphous silicon; (2) The silicon material includes amorphous silicon; (3) The average particle size of the silicon material is 1 nm to 100 nm.

9. The negative electrode material according to claim 1, characterized in that The negative electrode material meets at least one of the following technical characteristics: (1) The mass percentage of oxygen in the negative electrode material is ≤5wt%; (2) The mass of the carbon element in the negative electrode material accounts for 40wt% to 60wt%; (3) The mass of silicon element in the negative electrode material accounts for 40wt% to 60wt%.

10. The negative electrode material according to claim 1, characterized in that The negative electrode material meets at least one of the following technical characteristics: (1) The pores in the negative electrode material include micropores, and the pore volume of the micropores accounts for 2% to 50%; (2) The pores in the negative electrode material include mesopores, and the pore volume of the mesopores accounts for 50% to 98%.

11. The negative electrode material according to claim 1, characterized in that The specific surface area of the negative electrode material is 0.5 m 2 / g~10m 2 / g.

12. [Corrected 27.09.2024 according to Rule 91] The negative electrode material according to claim 1, characterized in that The compaction density of the negative electrode material is 0.8 g / cm 3 ~1.3g / cm 3 .

13. The negative electrode material according to claim 1, characterized in that The tap density of the negative electrode material is 0.5 g / cm 3 ~1.5g / cm 3 .

14. The negative electrode material according to claim 1, characterized in that The gas production of the negative electrode slurry prepared from the negative electrode material after being placed in a 25° C. environment for 24 hours is ≤0.5 mL / g, and the gas production of the negative electrode slurry prepared from the negative electrode material after being placed in a 45° C. environment for 24 hours is ≤2 mL / g.

15. A battery, characterized in that: The negative electrode material comprises the negative electrode material according to any one of claims 1 to 14.

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