Anode materials and batteries

Abstract

The present disclosure provides a negative electrode material and a battery, the negative electrode material including a carbon material and silicon particles, the negative electrode material having pores, and an average shape factor of the negative electrode material is F0, where 0.65≦F0<1. The average shape factor of the negative electrode material is measured by the following method: randomly selecting 10 negative electrode material particles, and calculating the cross-sectional area S of each negative electrode material particle. n and circumference C n Measure F n =4*π*S n / C n 2 where n is a natural number selected from 1 to 10, and the shape factor F of 10 particles is n The average value of is calculated, and this average value is referred to as the average shape factor F0 of the negative electrode material. The negative electrode material provided in the present disclosure has a stable structure, reduces the collapse of the negative electrode material structure due to the volume expansion of silicon particles during lithium release, and effectively reduces the occurrence of side reactions, thereby improving the cycle performance of the negative electrode material.

Description

[Technical Field]

[0001] The present disclosure relates to the field of anode materials, and more particularly to anode materials and batteries. [Background technology]

[0002] Lithium-ion batteries have advantages such as high energy density, long cycle life, minimal environmental pollution, and no memory effect, making them widely used in electric vehicles and household appliances. Conventional carbon anode materials have a low theoretical specific capacity (372 mAh / g), limiting their widespread use. To improve the energy density of lithium-ion batteries, researchers have begun to search for high-capacity anode materials. Silicon-based anode materials, with a theoretical specific capacity of up to 4200 mAh / g, have gradually become a hot research topic.

[0003] However, silicon-based anode materials experience relatively severe volume expansion during the alloying process with lithium. As cycling progresses, silicon-based anode materials experience decay mechanisms such as pulverization, contact loss with the conductive material and current collector, and the formation of an unstable solid electrolyte interface (SEI), which leads to degradation of the electrochemical performance of the anode materials.

[0004] Among them, carbon materials have excellent electrical conductivity and mechanical properties, and when combined with silicon, they can effectively mitigate the volume expansion of silicon, and can also improve the conductivity of the electrode and obtain a stable SEI film. Silicon-carbon composite materials are the first silicon-based anode materials to be commercialized, and are widely used in Li +This can shorten the transport distance of the silicon dioxide, which is beneficial for improving the dynamic performance of the material. However, nano-silicon particles have a large specific surface area, which makes it easy for the SEI film to consume excessive amounts of lithium salt, and the volume effect can easily cause electrical desorption between particles, resulting in a decrease in reversible capacity and Coulombic efficiency. Furthermore, nano-sized silicon particles tend to be distributed and aggregated in the carbon material, which causes the material to have a high volume expansion effect and ultimately leads to material fracture, thereby reducing the structural stability and cycle performance of the negative electrode material.

[0005] Therefore, there is an urgent need for a silicon-carbon anode material that can have low expansion, high capacity, and good cycle characteristics. Summary of the Invention [Problem to be solved by the invention]

[0006] The present disclosure provides a negative electrode material and a battery, which have a stable structure and reduce the collapse of the negative electrode material structure caused by the volume expansion of silicon particles during lithium release, effectively reducing the occurrence of side reactions, thereby improving the cycle performance of the negative electrode material. [Means for solving the problem]

[0007] In a first aspect, the present disclosure provides an anode material, the anode material comprising a carbon material and silicon particles, the anode material having pores; The negative electrode material has an average shape factor F0, and the average shape factor F0 is 0.65≦F0<1; The average shape factor F0 of the negative electrode material is measured by the following method: Ten negative electrode material particles were randomly selected, and the cross-sectional area S of each negative electrode material particle was calculated. n and circumference C n Measure F n =4*π*S n / C n 2 where n is a natural number selected from 1 to 10, and the shape factor F of 10 particles is nThe average value is calculated and is referred to as the average shape factor F0 of the negative electrode material. [Effects of the Invention]

[0008] The technical solution of the present disclosure has at least the following beneficial effects: The negative electrode material provided in the present disclosure includes a carbon material and silicon particles. By controlling the shape factor of the negative electrode material, the apparent corners of the particles can be effectively reduced and the isotropy of the negative electrode material particles can be increased. During charging and discharging, the negative electrode material can shrink and expand relatively uniformly along the radial direction, which can reduce the stress concentration problem caused by the volume expansion of the active material silicon particles in the negative electrode material, and is beneficial to maintaining the stability of the particle structure of the negative electrode material and reducing the pulverization of the particles of the negative electrode material. Furthermore, the stress concentration problem around the corners caused by the volume expansion of the silicon particles in the negative electrode material can be reduced, which is beneficial to maintaining the stability of the particle structure of the negative electrode material. DETAILED DESCRIPTION OF THE INVENTION

[0009] In order to better explain the present disclosure and facilitate understanding of the technical solutions of the present disclosure, the present disclosure will be described in more detail below. However, the following examples are merely simple examples of the present disclosure, and do not represent or limit the scope of protection of the present disclosure, and the scope of protection of the present disclosure is subject to the scope of the claims.

[0010] An embodiment of the present disclosure provides a negative electrode material, the negative electrode material including a carbon material and silicon particles, the negative electrode material having pores; The average shape factor of the negative electrode material is F0, and 0.65≦F0<1; The average shape factor F0 of the negative electrode material is measured by the following method: Ten negative electrode material particles were randomly selected, and the cross-sectional area S of each negative electrode material particle was calculated. n and circumference C n Measure F n =4*π*S n / C n 2 where n is a natural number selected from 1 to 10, and the shape factor F of 10 particles isn Calculate the average value, and denote the average value as the average shape factor F0 of the negative electrode material.

[0011] The negative electrode material provided in the present disclosure includes a carbon material and silicon particles. By controlling the shape factor of the negative electrode material, obvious corners of the particles can be effectively reduced, the isotropy of the negative electrode material particles can be increased, and the battery manufactured with the negative electrode material can make the negative electrode material shrink and expand relatively uniformly along the radial direction during the charge and discharge process, reducing the stress concentration problem caused by the volume expansion of the active material in the negative electrode material, such as silicon particles, maintaining the stability of the particle structure of the negative electrode material, and being advantageous for reducing the pulverization of the particles of the negative electrode material. It can reduce the stress concentration problem near the corners caused by the volume expansion of the silicon particles in the negative electrode material and is advantageous for maintaining the stability of the particle structure of the negative electrode material.

[0012] Specifically, the average shape factor F0 of the negative electrode material may be 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.72, 0.73, 0.74, 0.75, 0.76, 0.78, 0.79, 0.8, 0.81, 0.82, 0.85, 0.89, 0.90, 0.92, 0.93, 0.94, 0.95, 0.96, 0.98, 0.99, etc., and is not limited herein. The cross-sectional area S and perimeter C of the particles can be automatically picked up by software, and the shape factor F n is used to characterize the roundness of the boundary of the particles. Therefore, when the average shape factor of the negative electrode material is controlled within the range of 0.65 to 1, obvious corners of the particles can be effectively reduced, and when the average shape factor of the negative electrode material particles is maintained within the above range, the gap between the negative electrode material particles can be reduced, ensuring that the electrolyte fully infiltrates the negative electrode material, improving the tap density of the negative electrode material, and being advantageous for improving the cycle performance of the negative electrode material.

[0013] In some embodiments, the fractal dimension of the particles of the negative electrode material is X0, 1 < X0 < 3, and the fractal dimension X0 of the particles of the negative electrode material is obtained by measuring in the following manner. <所

[0014] Ten negative electrode material particles were randomly selected, and the cross-sectional area S of each negative electrode material particle was calculated. n and circumference C n Measure X n =(log(C n )-b)*2 / log(S n ) where b is a constant and the cross-sectional area S of each negative electrode material particle n and circumference C n is plotted on a double logarithmic graph, and the slope φ of the fitting line is obtained using the least squares method, and the fractal dimension of the particles of the negative electrode material is X0=2*φ.

[0015] As will be understood, the fractal dimension X0 of a particle is used to characterize the self-similarity of the particle contour and typically reflects the rate of change in length (e.g., perimeter) at different measurement scales (e.g., different areas). For negative electrode materials, the fractal dimension (X) based on the area-perimeter method is adopted to reflect the change pattern of the particle complexity with the particle area. When X0 = 1, the fractal dimension of all particles in the negative electrode material is the same. When 3 > X0 > 1, the fractal dimension of the particles in the negative electrode material decreases with increasing particle area, resulting in a lower degree of similarity in particle shape. Controlling the fractal dimension of the particles in the negative electrode material in this disclosure within the above range results in a higher degree of similarity in particle shape, i.e., a higher degree of uniformity in particle shape.

[0016] The negative electrode material provided in the present disclosure has a controlled fractal dimension of the particles of the negative electrode material. The fractal dimension X0 of the particles is used to characterize the self-similarity of the particle contours. The higher the similarity of the particle shapes of the negative electrode material particles, the higher the uniformity of the particle shapes. During charging and discharging, the negative electrode material can shrink and expand relatively uniformly along the radial direction, which can reduce the stress concentration problem caused by the volume expansion of the silicon particles of the active material in the negative electrode material. This is advantageous for maintaining the stability of the particle structure of the negative electrode material and reducing the pulverization of the negative electrode material particles, and is advantageous for the negative electrode material to exhibit excellent electrochemical performance in a cell.

[0017] In this disclosure, the negative electrode material is immersed in a 1M nitric acid solution for 4 hours, and then a 20% mass fraction HF acid solution is added drop by drop to the negative electrode material until yellow smoke is generated and the solution no longer generates yellow smoke. Finally, the residue is decomposed with a 1M nitric acid solution, washed, and dried to obtain a negative electrode material from which silicon particles have been removed.

[0018] In some embodiments, when the negative electrode material satisfies 0.65≦F0<1, the negative electrode material and the negative electrode material from which silicon particles have been removed are measured using an N adsorption / desorption method, and the negative electrode material has a ratio of the volume of nitrogen gas adsorbed at 90% partial pressure to the volume of nitrogen gas adsorbed at 10% partial pressure of A, where A is 1.3≦A≦2.5; In the negative electrode material from which silicon particles have been removed, the ratio of the volume of nitrogen gas adsorbed at 90% partial pressure to the volume of nitrogen gas adsorbed at 10% partial pressure is B, where 1≦B≦1.9 and A / B>1.

[0019] As can be seen, the physicochemical state of the anode material from which the silicon particles have been removed is close to that of the carbon material before the silicon particles are filled, and its porosity is high. The anode material from which the silicon particles have been removed has a volume P of nitrogen gas adsorbed at 90% partial pressure. 90 and the volume P of nitrogen gas adsorbed at 10% partial pressure 10 The ratio of the volume of nitrogen gas adsorbed at 90% partial pressure to the volume of nitrogen gas adsorbed at the negative electrode material after silicon particle filling is between 1 and 1.9. 90 and the volume P of nitrogen gas adsorbed at 10% partial pressure 10 The ratio of SiO2 to SiO2 is between 1.3 and 2.5, and the silicon particles fill a large amount of voids in the carbon material, especially micropores, so the pore volume of the negative electrode material is significantly reduced and mainly consists of mesopores and macropores, resulting in an increased A value.

[0020] In some embodiments, when a negative electrode material satisfies 0.65≦F0<1, the amount of gas generated when a negative electrode slurry made from the negative electrode material is placed in a 25°C environment for 24 hours is ≦1 mL / g, and the amount of gas generated when a negative electrode slurry made from the negative electrode material is placed in a 45°C environment for 24 hours is ≦2 mL / g.

[0021] The gas generation value is measured by dispersing carboxymethyl cellulose (CMC) in water at a mass ratio of 1.4% to form an adhesive. After uniform dispersion, 10 g of the adhesive is mixed with 10 g of anode material to obtain a slurry. The slurry is placed in an aluminum plastic film bag, the mass of the slurry is recorded, and then sealed to form a sealed aluminum plastic film bag. The sealed aluminum plastic film bag is fixed to the bottom of a container and completely immersed in water. The volume of the aluminum plastic film bag is recorded. After 24 hours of fixation, the volume of the aluminum plastic film bag is recorded again. The gas generation amount of the silicon anode material is calculated based on the volume change of the aluminum plastic film bag, and the unit is mL / g.

[0022] In some embodiments, the average pore size of the pores in the negative electrode material is 0.5 nm to 50 nm. For example, the average pore size of the pores in the negative electrode material may be 0.5 nm, 0.8 nm, 1.0 nm, 1.3 nm, 1.5 nm, 1.8 nm, 2.0 nm, 3.0 nm, 4.0 nm, 5.0 nm, 8.0 nm, 10.0 nm, 15 nm, 20 nm, 25 nm, 30 nm, 40 nm, or 50 nm, etc., but is not limited thereto. Controlling the average pore size of the pores in the negative electrode material is advantageous for improving the multiplication performance of the negative electrode material, mitigating the volume expansion of silicon particles, and improving the structural stability of the negative electrode material. The average pore size of the pores in the negative electrode material is preferably 0.5 nm to 20 nm. The average pore size of the pores in the negative electrode material is more preferably 1.6 nm to 5 nm.

[0023] In some embodiments, the average pore size of the pores in the negative electrode material from which the silicon particles have been removed is 1.7 nm to 2.2 nm. Specific examples include, but are not limited to, 1.7 nm, 1.8 nm, 1.9 nm, 2.0 nm, 2.1 nm, and 2.2 nm. If the pore size of the carbon material is too small, the gaseous precursors of the silicon particles are less likely to penetrate the pores and gather on the surface of the carbon material, forming a shell structure. This reduces the silicon particle content inside the negative electrode material and reduces the specific capacity of the negative electrode material. If the pore size of the carbon material is too large, although it is advantageous for silicon particle filling, it may lead to problems such as uneven distribution and concentration of silicon particles. This results in uneven expansion of the negative electrode material, excessive local expansion stress, particle fracture, and further deterioration of the electrochemical performance of the negative electrode material. Therefore, controlling the average pore size of the pores of the carbon material within the above range is advantageous for combining the carbon material with silicon particles, improving the multiplication performance of the negative electrode material, and alleviating the volume expansion of the silicon particles, thereby improving the structural stability of the negative electrode material.

[0024] In some embodiments, the total pore volume of the negative electrode material is less than or equal to 0.001 cm 3 / g~0.4cm 3 / g, and the total pore volume of the negative electrode material is specifically 0.001 cm 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, 0.1cm 3 / g, 0.2cm 3 / g or 0.4cm 3 / g, etc., and of course, other values ​​within the above ranges are also possible and are not limited thereto. The total pore volume of the negative electrode material is 0.001 cm 3 / g~0.1cm 3 / g is preferred.

[0025] In some embodiments, the total pore volume of the negative electrode material from which the silicon particles have been removed is less than or equal to 0.2 cm 3 / g~2.0cm 3 / g. Specifically, 0.2 cm 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 thereto. Compared with a negative electrode material from which silicon particles have been removed, a negative electrode material containing silicon particles has a significantly reduced pore volume and an increased density of the negative electrode material, effectively improving the specific capacity of the negative electrode material. By controlling the total pore volumes of the negative electrode material filled with silicon particles and the negative electrode material from which silicon particles have been removed within the above range, the present disclosure not only improves the specific capacity of the negative electrode material, but also ensures that the negative electrode material retains an appropriate amount of void space to cushion the volume expansion of the silicon particles caused by the lithium release process, which is beneficial to improving the cycle performance of the negative electrode material. The total pore volume of the negative electrode material from which silicon particles have been removed is 0.5 cm 3 / g~2.0cm 3 / g is preferred.

[0026] In some embodiments, the pores in the negative electrode material from which silicon particles have been removed include micropores, and the micropores account for a volumetric occupancy of ≥ 80% of all pores. Specifically, the volumetric occupancy of micropores with a pore size of 2.0 nm or less may be 80%, 81%, 82%, 83%, 84%, 85%, 87%, 88%, 90%, 92%, 93%, 95%, 98%, or 99%, etc., without limitation, herein. As can be understood, the pores in the negative electrode material from which silicon particles have been removed are mainly micropores, and a pore size distribution within this range is beneficial for the growth of silicon particles during the growth process, for adjusting the size of silicon particles, and for reducing silicon particle segregation, thereby improving the compactness of the negative electrode material and alleviating excessive local expansion stress in the negative electrode material.

[0027] In some embodiments, in the negative electrode material from which silicon particles have been removed, pores with a pore size of 5.0 nm or less account for a volumetric occupancy of ≥ 90% of the total pore volume. Specifically, the volumetric occupancy of pores with a pore size of 5.0 nm or less may be 80%, 81%, 82%, 83%, 84%, 85%, 87%, 88%, 90%, 92%, 93%, 95%, 98%, or 99%, etc., without limitation. As can be understood, the pores in the negative electrode material (carbon material) from which silicon particles have been removed are primarily pores with a size of 5.0 nm or less. A pore size distribution within this range helps form pathways for gas-phase mass transfer within the carbon material during the growth process and improves the diffusion environment within the carbon material, thereby improving the compactness of the negative electrode material.

[0028] In some embodiments, the porosity of the negative electrode material from which the silicon particles have been removed is 40% to 60%. Specifically, the porosity may be 40%, 45%, 48%, 50%, 52%, 55%, 56%, 57%, 58%, or 60%, etc., and of course, other values ​​within the above ranges may also be used, and are not limited thereto.

[0029] In some embodiments, the pores in the negative electrode material include at least one of micropores, mesopores, and macropores.

[0030] In some embodiments, the volume of the micropores is ≦5% of the total pore volume, and may be, but is not limited to, 5%, 4%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, or 0.1%.

[0031] In some embodiments, the volume occupancy of mesopores in all pores is 87% to 97%, and specifically may be 87%, 88%, 89%, 90%, 92%, 93%, 94%, 95%, 96%, or 97%, etc., and of course, may be other values ​​within the above range, and is not limited thereto.

[0032] In some embodiments, the macropores occupy a volume of less than 13% of all pores, and may be, for example, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, or 1%, and of course, may be other values ​​within the above range, and are not limited thereto.

[0033] As can be seen, the pores of the negative electrode material are mainly composed of mesopores and macropores, since the silicon particles fill a large amount of voids, especially micropores, in the carbon material. In some embodiments, the specific surface area of ​​the negative electrode material from which the silicon particles have been removed is 1300 m 2 / g~2500m 2 / g. Specifically, the specific surface area of ​​the carbon material is 1300 m 2 / g, 1500m 2 / g, 2000m 2 / g, 2100m 2 / g, 2200m 2 / g, 2300m 2 / g, 2400m 2 / g or 2500m 2 / g, etc., and of course, other values ​​within the above ranges are also possible and are not limited here.

[0034] In some embodiments, the tap density of the negative electrode material from which the silicon particles have been removed is ≥ 0.30 g / cm 3 Specifically, it is 0.4 g / cm 3 , 0.5g / cm 3 , 0.6g / cm 3 , 0.7g / cm 3 , 0.8g / cm 3 , 0.9g / cm 3 , 1.0g / cm 3 , 1.10g / cm 3 , 1.20g / cm 3 , 1.30g / cm 3 , 1.40g / cm 3 or 1.50 g / cm 3 As will be understood, the carbon material has a large amount of pores, the presence of the pores reduces the density of the carbon material, and sufficient voids are favorable for the growth of silicon particles.

[0035] In some embodiments, the tap density of the negative electrode material is 0.5 g / cm 3 ~1.5g / cm 3 Specifically, it is 0.5 g / 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 As can be seen, the silicon particles are filled into the pores of the carbon material, increasing the density of the carbon material, and the tap density of the negative electrode material increases by 80% to 120% compared to the initial carbon material.

[0036] In some embodiments, the carbon material comprises at least one of amorphous carbon, crystalline carbon, and mesocarbon microbeads. The carbon material can improve the conductivity of the negative electrode material.

[0037] In some embodiments, at least some silicon particles are filled into the pores of the carbon material. As can be understood, the filling of the silicon particles into the pores of the carbon material ensures a diffuse distribution between the silicon particles and the carbon material, which can improve the specific capacity of the negative electrode material, while the reduction of voids after the silicon particles are filled into the carbon material can improve the density of the negative electrode material, effectively reducing the occurrence of side reactions between the negative electrode material and the electrolyte, and further improving the cycle performance of the material. In some embodiments, the silicon particles include at least one of amorphous silicon, crystalline silicon, silicon oxide, silicon alloy, and composite of crystalline silicon and amorphous silicon. Specifically, the silicon alloy may be, for example, a silicon-lithium alloy, a silicon-magnesium alloy, etc., and it should be understood that in some cases, the silicon alloy may include both single silicon particles and alloys.

[0038] In some embodiments, the silicon particles comprise amorphous silicon, which can be understood to expand isotropically during lithium absorption, reduce the collapse of the pore structure in the negative electrode material, suppress rapid decay of the specific capacity of the negative electrode material, and improve the lithium absorption cycle characteristics of the negative electrode material.

[0039] In some embodiments, the negative electrode material may further comprise other active materials, which are materials that can react with lithium to release lithium. Specifically, the active materials include Li, Na, K, S, and the like. n The active material may contain at least one of Ge, Fe, Mg, Ti, Zn, Al, P, and Cu, and the active material may be a simple metal.

[0040] In some embodiments, the active material may specifically be Sn particles, Ge particles, Al particles, and in other embodiments, the active material may be a silicon-lithium alloy, a silicon-magnesium alloy, etc., and of course, it should be mentioned that in some cases the active material includes simple particles and alloys.

[0041] In some embodiments, the average particle size of the silicon particles is less than 50 nm. Specifically, the average particle size of the silicon particles may be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 46 nm, 47 nm, 48 nm, or 49 nm, etc., but is not limited thereto. The average particle size of the silicon particles is determined by observing the silicon particles with a field emission scanning electron microscope or a transmission electron microscope, directly measuring the particle sizes of 5 to 10 silicon particles using a scale, and averaging the particle sizes.

[0042] In some embodiments, the mass percentage of carbon elements in the negative electrode material is 40% to 80%, and may be specifically 40%, 50%, 60%, 70%, or 80%, etc., and may of course be other values ​​within the above range, and is not limited thereto. The mass percentage of carbon elements in the negative electrode material is preferably 40% to 60%.

[0043] In some embodiments, the mass percentage of silicon in the negative electrode material is 20% to 55%, specifically, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or 55%, etc., and may be other values ​​within the above range, and is not limited thereto. Preferably, the mass content of silicon in the negative electrode material is greater than 35% and less than 55%.

[0044] In some embodiments, the mass ratio of silicon to carbon in the negative electrode material is 0.9 to 1.10, including, but not limited to, 0.9, 0.92, 0.95, 0.98, 1.0, 1.01, 1.02, 1.05, 1.07, 1.08, or 1.10. When the mass ratio of silicon to carbon in the negative electrode material is ≦0.9, the specific capacity of the negative electrode material decreases, but the overall cycling performance improves. When the mass ratio of silicon to carbon in the negative electrode material is ≧1.1, the specific capacity of the negative electrode material increases with increasing silicon particle content, but the volume expansion effect of silicon is significant, affecting the cycling performance of the negative electrode material. Controlling the mass ratio within the above range is beneficial to improving the overall specific capacity and cycling stability of the negative electrode material.

[0045] In some embodiments, the mass content of oxygen element in the negative electrode material is ≦6%. Specifically, the mass content of oxygen element in the negative electrode material may be 1%, 2%, 3%, 4%, 5%, or 6%, without limitation. It is understood that if the mass occupancy of oxygen element is too high, the active material (e.g., silicon) in the negative electrode material will be partially oxidized, causing at least some of the pores to be destroyed, thereby affecting the cycling stability of the material. Controlling the mass occupancy of oxygen element in the negative electrode material within the above range can ensure that a large amount of inert SiO2 is not produced in the material, thereby reducing the cycling characteristics of the negative electrode material. The presence of a small amount of oxygen element can reduce side reactions between the electrolyte and silicon particles by utilizing passivated silicon oxide on the surface. Therefore, the mass content of oxygen element in the negative electrode material is preferably ≦5%.

[0046] In some embodiments, the mass content of water in the negative electrode material is ≦5%, and specifically may be 5%, 4%, 3%, 2.5%, 2%, 1.5%, 1.0%, 0.5%, etc., but is not limited thereto.

[0047] In some embodiments, the ash content of the negative electrode material is ≦1%, and specifically may be 1%, 0.9%, 0.8%, 0.6%, 0.5%, 0.4%, 0.2%, 0.1%, etc., but is not limited thereto.

[0048] In some embodiments, the specific surface area of ​​the negative electrode material is 0.5 m 2 / g~10m 2 Specifically, the specific surface area of ​​the negative electrode material is 0.5 m 2 / g, 1m 2 / g, 2m 2 / g, 3m 2 / g, 4m 2 / g, 5m 2 / g, 6m 2 / g, 7m 2 / g, 8m 2 / g, 9m 2 / g, 400m 2 / g, or 10m 2 / g, etc., and of course, other values ​​within the above range are also possible, and are not limited thereto. 2 / g~10m 2 / g is preferred.

[0049] In some embodiments, the aqueous solution of the negative electrode material has Fe≦100 ppm, Na≦50 ppm, K≦100 ppm, Cu≦25 ppm, Cr≦20 ppm, Co≦1 ppm, Ni≦5 ppm, Al≦5 ppm, Bi≦2 ppm, Mg≦5 ppm, Pb≦1 ppm, Sb≦1 ppm, Sn≦10 ppm, Ti≦1 ppm, V≦1 ppm, and S≦20 ppm. Because metal impurity ions such as iron, nickel, sodium, and aluminum salts have a lower reduction potential than lithium ions, they are first absorbed into the negative electrode during charging, which reduces the number of lithium ion absorption sites in the negative electrode, affecting the battery capacity of the negative electrode material and reducing the reversible capacity of the lithium battery. Metal impurity ions such as iron, copper, and zinc cause self-discharge. The grown iron ions are also prone to breaking through the separator, causing micro-short circuits and safety issues. Furthermore, the deposition of metal impurity ions prevents the electrode surface from forming an effective passivation layer, leading to the destruction of the entire battery. Therefore, controlling the content of the above-mentioned metal impurities is beneficial to improving the electrochemical performance of the negative electrode material.

[0050] In some embodiments, the aqueous solution of the negative electrode material has Li≦5 ppm, Mn≦20 ppm, Na≦10 ppm, Ca≦20 ppm, K≦1 ppm, and Sr≦1 ppm. By controlling the residual amount of each type of impurity, the purity of the negative electrode material can be ensured and the impact of the impurities on the electrochemical performance of the negative electrode material can be reduced.

[0051] In some embodiments, the particle size D of the negative electrode material 50 2μm≦D 50 ≦20 μm and 0.9≦(D 90 -D 10 ) / D 50 ≦5. Specifically, (D 90 -D 10 ) / D 50Specifically, the ratio may be 0.9, 1.0, 1.1, 1.3, 1.5, 1.6, 1.7, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5, etc., but is not limited thereto. As can be understood, the larger the particle size of the negative electrode material particles, the longer the lithium ion diffusion path, and the inevitable existence of fractures and other defects in the Si / C lattice structure. These defects increase with the changes in the lattice structure due to expansion and contraction during charging. Lithium ions are more likely to encounter such defects when diffusing into large particles, thus making the diffusion kinetics more difficult and causing more irreversible lithium loss than diffusion into small particles. Relatively small particles have more defects, which increases the resistance to lithium ion diffusion and prevents some active lithium ions from escaping smoothly during charging and discharging, increasing the irreversible capacity. Furthermore, the fine particles also increase the contact area between the electrode and the electrolyte, which is detrimental to the cycle performance of the battery. Combining these two factors, the above range allows the anode material to achieve better electrochemical performance. Furthermore, when the anode material is fabricated into an anode sheet and the anode sheet is applied to a battery, the anode sheet has a uniform local current density distribution in the early stage of discharge. However, in the later stage of discharge, the local current density difference between particles of different sizes becomes large, resulting in a large overvoltage for large particles, i.e., large polarization. Therefore, by controlling the particle size of the anode material particles to be uniformly distributed, the severity of polarization caused by large particles in the later stage of discharge can be reduced. D 10 ≧1.5μm, 5μm≦D 50 ≦9μm, D 90 ≦20μm and 0.9≦(D 90 -D 10 ) / D 50 It is preferred that it is ≦1.7.

[0052] In some embodiments, 0.7≦F0<1. As can be seen, the negative electrode material particles are closer to spherical particles, which can increase the isotropy of the negative electrode material particles. During charging and discharging, the negative electrode material can shrink and expand relatively more uniformly along the radial direction, which can reduce the stress concentration problem caused by the volume expansion of the active material in the negative electrode material, maintain the stability of the particle structure of the negative electrode material, and reduce particle powdering. From the perspective of production cost, it is preferable that 0.7≦F0≦0.8.

[0053] In some embodiments, when 0.7≦F0<1, the specific surface area of ​​the negative electrode material is S1m 2 / g, and the total pore volume of the negative electrode material is P1cm 3 / g, C1=S1 / (P1*100), and 8≦C1≦20.

[0054] In the present disclosure, the negative electrode material satisfies 0.7≦F0<1 and 8≦C1≦20, and by controlling the specific surface area and total pore volume of the negative electrode material, the negative electrode material has an appropriate pore volume, and the negative electrode material has enough space to cushion the volume expansion of the silicon particles in the negative electrode material, but the specific surface area of ​​the negative electrode material is not too large, thereby reducing the occurrence of side reactions between the negative electrode material and the electrolyte and thereby comprehensively improving the performance of the negative electrode material in all aspects. The negative electrode material of the present disclosure controls the surface shape of the negative electrode material and the internal pore distribution of the negative electrode material, so that the two work synergistically to better cushion the volume expansion of the silicon particles, thereby improving the strength, structural stability, and cycle performance of the negative electrode material and comprehensively improving the performance of the negative electrode material in all aspects.

[0055] Specifically, the possible values ​​of C1 are 8, 9, 10, 11, 12, 15, 16, 18, and 20, etc., and are not limited thereto. The total pore volume and specific surface area are very important parameters for characterizing the properties of a negative electrode material, and they are closely related. The larger the total pore volume and the more pores there are in the negative electrode material, the larger the specific surface area, and therefore the more likely the carbon material is to adsorb the gaseous precursor of silicon particles (e.g., silicon source gas), and the more likely the gaseous precursor of silicon particles is to undergo decomposition and growth reactions in the pores of the carbon material. However, the larger the specific surface area of ​​the negative electrode material, the lower the strength and hardness of the negative electrode material particles and the more side reactions of the negative electrode material occur, which causes the cycle stability of batteries manufactured with the negative electrode material to deteriorate. If the C1 value of the negative electrode material is too large, the total pore volume of the negative electrode material will be too small or the specific surface area of ​​the negative electrode material will be too large, resulting in too few voids and large pore diameters in the negative electrode material, which will reduce the amount of active material carried in the negative electrode material and be unfavorable for mitigating the volume expansion of the negative electrode material during charging and discharging, causing some deterioration in the capacity, scalability, and cycle performance of the negative electrode material.If the C1 value of the negative electrode material is too small, the total pore volume of the negative electrode material will be too large or the specific surface area of ​​the negative electrode material will be too small, resulting in too many voids and small pore diameters in the negative electrode material, which will reduce the structural stability of the negative electrode material, making the negative electrode material prone to structural collapse during charging and discharging, resulting in reduced cycle performance of the negative electrode material, and will increase side reactions between the negative electrode material and the electrolyte, resulting in increased consumption of active lithium ions and reduced initial efficiency of the negative electrode material.

[0056] In some embodiments, when 0.7≦F0<1, the specific surface area of ​​the negative electrode material from which the silicon particles have been removed is S2m 2 / g, and the total pore volume of the negative electrode material after removing the silicon particles is P2cm 3 / g, where C2 = S2 / (P2 * 100), and 10≦C2≦25. Specifically, C2 can be 10, 12, 13, 14, 15, 18, 20, 21, 23, 25, etc., and of course, can be other values ​​within the above range and are not limited thereto. Controlling C2 of the anode material (i.e., carbon material) from which silicon particles have been removed within the above-mentioned range is advantageous in controlling the total pore volume and specific surface area of ​​the carbon material to be in a balanced state, increasing the occupancy rate of micropores and small mesopores (<5 nm) within the carbon material, improving the loading and distribution uniformity of silicon particles in the carbon material, and reducing local stress concentration. It is also advantageous in mitigating volume expansion of the active material during charging and discharging, and in maintaining the shape of the carbon material during charging and discharging. The anode material disclosed herein controls the surface shape of the anode material and the internal pore distribution of the carbon material, allowing the two to work synergistically, which is advantageous in maintaining the shape of the anode material particles and reducing the crushing of the anode material particles during charging and discharging. It also better mitigates the volume expansion of the silicon particles, thereby improving the strength, structural stability, and cycle performance of the anode material and comprehensively improving the performance of the anode material in all aspects.

[0057] In some embodiments, when 0.7≦F0<1, the tap density of the negative electrode material is 0.8 g / cm 3 ~1.3g / cm 3 Specifically, it is 0.8g / cm 3 , 0.9g / cm 3 , 1.0g / cm 3 , 1.2g / cm 3 or 1.3 g / cm 3 It is understood that the tap density of the negative electrode material can be increased by 80% to 120% compared to the initial carbon material, since the silicon particles and / or other active materials are filled into the pores of the carbon material.

[0058] In some embodiments, when 0.65≦F0<0.7, the average shape factor F0 of the negative electrode material decreases, but the corners on the surface of the negative electrode material particles become smoother or have no obvious corners. During charging and discharging, the negative electrode material can still shrink and expand relatively uniformly along the radial direction, reducing the problem of stress concentration near the corners caused by the volume expansion of the silicon particles in the negative electrode material, which is beneficial to maintaining the stability of the particle structure of the negative electrode material and reducing the powdering of the negative electrode material particles. Furthermore, maintaining the average shape factor of the negative electrode material particles within this range can reduce the gaps between the negative electrode material particles, which is beneficial to improving the green density of the negative electrode material and improving the cycle performance of the negative electrode material.

[0059] In some embodiments, when 0.65≦F0<0.7, the oil absorption of the negative electrode material is Q1 mL / 100 g, 30≦Q1≦80, and the oil absorption of the negative electrode material from which silicon particles have been removed is Q2 mL / 100 g, 120≦Q2≦200, and (Q2−Q1) / Q1>0.5. Specifically, Q1 can have a value of 30, 32, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, etc., and is not limited thereto. Q2 can have a value of 120, 130, 140, 150, 160, 170, 180, 190, or 200, and is not limited thereto. Possible values ​​for (Q2-Q1) / Q1 include, specifically, 0.51, 0.55, 0.6, 0.7, 0.8, 0.9, 0.95, 1.0, 1.2, 1.5, 1.8, 2.0, or 3, and of course may be other values ​​within the above range.

[0060] In the present disclosure, (Q2-Q1) / Q1 is controlled to be greater than 0.5. Generally, the more voids within the material are developed, the greater its oil absorption. Limiting the change in oil absorption within the material before and after growth ensures that the voids within the material are effectively filled, reflecting the uniform distribution of silicon particles and carbonaceous material within the material. Anode materials from which silicon particles have been removed, i.e., anode materials, have developed voids before silicon particle filling, which causes a change in the oil absorption of the anode material before and after silicon particle filling. In electrochemical devices, lithium ion release not only requires diffusion channels and reaction interfaces, but also requires the electrolyte as a medium. Through experimental research, the applicant has found that while ensuring excellent infiltration performance of anode materials, improving the packing of silicon particles can improve the specific capacity of the anode material, thereby achieving both high specific capacity and excellent infiltration performance.

[0061] In some embodiments, when 0.65≦F0<0.7, the green density of the negative electrode material is 0.80 g / cm 3 ~1.30g / cm 3 Specifically, 0.8 g / cm 3 , 0.9g / cm 3 , 1.0g / cm 3 , 1.05g / cm 3 , 1.1g / cm 3 , 1.2g / cm 3 , 1.25g / cm 3 or 1.3 g / cm 3 The density of the green compact of the negative electrode material may be within the above range, and is not limited thereto. Controlling the green compact density of the negative electrode material within the above range is advantageous in improving the energy density of the negative electrode material and improving the cycle characteristics of the negative electrode material.

[0062] In some embodiments, when 0.65≦F0<0.7, the powder conductivity of the negative electrode material at 20 kN is 0.5 S / cm to 2.0 S / cm, specifically, 0.5 S / cm, 0.6 S / cm, 0.71 S / cm, 0.75 S / cm, 0.79 S / cm, 0.8 S / cm, 0.9 S / cm, 1.0 S / cm, 1.1 S / cm, 1.2 S / cm, 1.4 S / cm, 1.5 S / cm, 1.8 S / cm, or 2.0 S / cm, etc., and of course, other values ​​within the above range are also possible, and are not limited thereto. Preferably, the powder conductivity of the negative electrode material at 20 kN is greater than 0.7 S / cm and less than 1.5 S / cm.

[0063] In a second aspect, the present disclosure further provides a method for manufacturing anode materials, employing a chemical vapor deposition process. Chemical vapor deposition (CVD) involves placing a carbon material in the presence of one or more precursor gases, which react and / or decompose on the surface of the carbon material under set temperature and pressure conditions to produce a desired growth product, thereby obtaining a high-performance anode material.

[0064] The manufacturing method specifically includes the following steps: In S10, a carbon material having pores is provided. In some embodiments, the carbon material production process includes the following steps: A certain amount of carbon-grade phenolic resin is weighed, and the surfactant Span 85 is added and mixed uniformly. The mass ratio of the phenolic resin to the surfactant is less than 6:1, and the dispersion ratio (defined as the mass ratio of the phenolic resin to the 201-methyl silicone oil (used as a dispersant)) is adjusted to 0.08-0.12. The 201-methyl silicone oil is then added and stirred uniformly. The mixture is then placed in a three-neck flask. After uniform stirring, the curing temperature is increased to 120-150°C, and the mixture is allowed to react at this temperature for a certain period of time (60 minutes), after which it is cooled to room temperature. The 201-methyl silicone oil is extracted using a Soxhlet extractor to obtain phenolic resin microspheres. The phenolic resin microspheres are placed in a box furnace and carbonized at 500-900°C for 0.5-2.5 hours to obtain a carbonized material. The carbonized material is then heated to 500-800°C and activated with steam for 2-10 hours to obtain activated carbon. Activated carbon is placed in a furnace and heated to 400-600°C at a rate of 2-10°C / min, the growth pressure is set to 0.05-10 kPa, the growth time is set to 2-1000 h, and the silicon source gas flow rate is set to 0.1-10 L / min.

[0065] In some other embodiments, the carbon material production process includes the following steps: The carbon source precursor is placed in a grinder, pulverized in an automatic mortar, and then sieved to a size of 45 μm or less. It is then freeze-dried in a vacuum freeze dryer for 24 hours. The freeze-dried carbon source precursor is placed in a tubular furnace and treated at 750°C for 120 minutes under an argon gas atmosphere. It is then immersed in dilute hydrochloric acid (10 wt%) for 6 hours to remove inorganic impurities from the carbon source precursor. It is then washed with deionized water and absolute ethanol until the filtrate becomes neutral, and placed in a ventilated oven at 60°C to thoroughly dry it, yielding an intermediate. The intermediate is placed in a quartz boat and placed in the center of the quartz tube in the tubular furnace. Prior to heating, high-purity argon gas is passed through the tube for 30 minutes to purge the air. The temperature is then increased to 700°C-1300°C at a rate of 10°C / min, and a single carbonization treatment is performed at constant temperature for 1 hour. The resulting carbonized material is then cooled to room temperature. Finally, a mixture of the carbonized material and a sodium hydroxide solution or potassium hydroxide solution with a concentration of 0.2 g / mol to 0.5 g / mol is dried, and the temperature is raised to 800 to 900°C for two carbonization treatments. The carbonized product is then immersed in a hydrochloric acid solution and pickled, and then ultrasonically washed with ethanol or deionized water until the pickling water becomes neutral. After solid-liquid separation, the product is dried by raising the temperature to 70 to 90°C, and the dried carbon material is pulverized using a ball mill-type fluidized bed jet mill. In other words, the carbon material is bombarded with gas so that the particles of the carbon material have a predetermined particle size, thereby obtaining the carbon material.

[0066] In other embodiments, the carbon material can be purchased directly from conventional, meet-the-needs carbon material.

[0067] In some embodiments, the specific surface area of ​​the carbon material is S2'm 2 / g, and the total pore volume of the negative electrode material after removing the silicon particles is P2'cm 3 / g, where C2' = S2' / (P2'*100), and 10≦C2'≦25. Specifically, C2' can be 10, 12, 13, 14, 15, 18, 20, 21, 23, 25, etc., and of course, other values ​​within the above range are also possible and are not limited thereto. Controlling the C2' of the carbon material within the above-mentioned range is advantageous in controlling the total pore volume and specific surface area of ​​the carbon material to be in a balanced state, increasing the occupancy rate of micropores and small mesopores (<5 nm) within the carbon material, improving the loading and distribution uniformity of silicon particles in the carbon material, and reducing local stress concentration. It is also advantageous in mitigating volume expansion during charge and discharge of the active material and maintaining the shape of the carbon material during charge and discharge.

[0068] In some embodiments, the oil absorption of the carbon material is Q2'mL / 100g, and 120≦Q2'≦200. Specifically, the possible values ​​of Q2' may be 120, 130, 140, 150, 160, 170, 180, 190, or 200, and are not limited thereto.

[0069] In some embodiments, the carbon material has a ratio B' between the volume of nitrogen gas adsorbed at 90% partial pressure and the volume of nitrogen gas adsorbed at 10% partial pressure, and B' is 1≦B'≦1.9, and B' may be, for example, 1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, or 1.9, without being limited thereto. As can be understood, before being filled with silicon particles, the carbon material has a high porosity and relatively large pore sizes, which is advantageous for the active material to grow uniformly in the pores.

[0070] In some embodiments, the average pore size of the carbon material is 1.7 nm to 2.2 nm, specifically 1.7 nm, 1.8 nm, 1.9 nm, 2.0 nm, 2.1 nm, 2.2 nm, etc., but is not limited thereto. If the pore size of the carbon material is too small, the gaseous precursor of the active material (e.g., silicon-oxygen gas) will not easily penetrate the pores, resulting in a decrease in the active material content in the negative electrode material and a decrease in the specific capacity of the negative electrode material. If the pore size of the carbon material is too large, although advantageous for filling the active material, it can lead to problems such as uneven distribution and segregation of the active material, which can result in uneven expansion of the negative electrode material, excessive localized expansion stress, particle crushing, and further deterioration of the electrochemical performance of the negative electrode material. Therefore, controlling the average pore size of the carbon material within the above range is advantageous for combining the carbon material with the active material, improving the multiplier performance of the negative electrode material, mitigating the volumetric expansion of the active material, and improving the structural stability of the negative electrode material.

[0071] In some embodiments, the total pore volume of the carbon material is less than or equal to 0.2 cm 3 / g~2.0cm 3 / g. Specifically, 0.2 cm 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 2.0cm 3 / g, etc., and of course, other values ​​within the above ranges are also possible and are not limited thereto. The total pore volume of the negative electrode material from which the silicon particles have been removed is 0.5 cm 3 / g~2.0cm 3 / g is preferred.

[0072] In some embodiments, in the carbon material, the volume occupancy of micropores with a pore size of 2.0 nm or less is ≥ 80% of the total pore volume. Specifically, the volume occupancy of micropores with a pore size of 2.0 nm or less may be 80%, 81%, 82%, 83%, 84%, 85%, 87%, 88%, 90%, 92%, 93%, 95%, 98%, or 99%, etc., without limitation. As can be understood, the pores in the carbon material are mainly micropores, and a pore size distribution within this range is beneficial to the growth of silicon particles during the growth process, adjusting the size of the silicon particles, and reducing the segregation of silicon particles, thereby improving the compactness of the negative electrode material and alleviating excessive local expansion stress.

[0073] In some embodiments, in the carbon material, the pores having a diameter of 5.0 nm or less occupy a volume of ≥ 90% of the total pore volume. Specifically, the pores having a diameter of 5.0 nm or less may occupy a volume of 80%, 81%, 82%, 83%, 84%, 85%, 87%, 88%, 90%, 92%, 93%, 95%, 98%, or 99% of all pores, etc., but this is not limited thereto.

[0074] In some embodiments, in the carbon material, pores with a pore size of 1.5 nm or less account for 20% to 25% of the total pore volume, and pores with a pore size of 1.6 nm or less account for 20% to 50% of the total pore volume. It is understood that the pores in the carbon material are mainly micropores, and a pore size distribution within this range helps to form pathways for gas-phase mass transfer within the carbon material during the growth process and improve the diffusion environment within the carbon material, thereby improving the density of the negative electrode material.

[0075] In some embodiments, the porosity of the carbon material is 40% to 60%. Specifically, the porosity may be 40%, 45%, 48%, 50%, 52%, 55%, 56%, 57%, 58%, or 60%, and of course, may be other values ​​within the above range, and is not limited thereto.

[0076] In some embodiments, the specific surface area of ​​the carbon material is 1300 m 2 / g~2500m 2 / g. Specifically, the specific surface area of ​​the carbon material is 1300 m 2 / g, 1500m 2 / g, 2000m 2 / g, 2100m 2 / g, 2200m 2 / g, 2300m 2 / g, 2400m 2 / g or 2500m 2 / g, etc., and of course, other values ​​within the above ranges are also possible and are not limited here. In some embodiments, the tap density of the carbon material is ≥ 0.30 g / cm 3 Specifically, it is 0.4 g / cm 3 , 0.5g / cm 3 , 0.6g / cm 3 , 0.7g / cm 3 , 0.8g / cm 3 , 0.9g / cm 3 , 1.0g / cm 3 , 1.10g / cm 3 , 1.20g / cm 3 , 1.30g / cm 3 , 1.40g / cm 3 or 1.50 g / cm 3 As will be appreciated, the carbon material has a large amount of pores, the presence of the pores reduces the density of the carbon material, and sufficient voids are favorable for the growth of silicon particles.

[0077] In some embodiments, the carbon material comprises at least one of amorphous carbon, crystalline carbon, and mesocarbon microbeads. The carbon material can improve the electrical conductivity of the negative electrode material.

[0078] In some embodiments, the pH value of the carbon material is 6 to 9, and specifically may be 6, 6.5, 7, 7.5, 8, 8.5, or 9, etc., but is not limited thereto.

[0079] In some embodiments, the mass content of hydrogen element in the carbon material is 0.01% to 5%, and specifically may be 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, etc., but is not limited thereto.

[0080] In some embodiments, the mass content of oxygen element in the carbon material is 0.01% to 10%, and specifically may be 0.01%, 0.05%, 0.08%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, etc., but is not limited thereto.

[0081] In some embodiments, the mass content of nitrogen element in the carbon material is 0.01% to 0.5%, and specifically may be 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, etc., and is not limited thereto.

[0082] In S20, a reactive gas containing a silicon source gas is flowed to perform vapor deposition on the carbon material, thereby obtaining a negative electrode material.

[0083] In some embodiments, the growth temperature for vapor deposition is 400° C. to 650° C. Specifically, the growth temperature may 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, may be other values ​​between 400° C. and 650° C., and is not limited thereto.

[0084] In some embodiments, the temperature rise rate for the vapor phase growth is 2°C / min to 20°C / min, and specifically may be 2°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, 13°C / min, 15°C / min, 16°C / min, 17°C / min, 18°C / min, 19°C / min, or 20°C / min, etc., but is not limited thereto.

[0085] In some embodiments, the growth pressure of the vapor deposition is 0.05 kPa to 101 kPa. Specifically, the growth pressure may be 0.05 kPa, 0.1 kPa, 0.5 kPa, 1 kPa, 5 kPa, 10 kPa, 15 kPa, 20 kPa, 25 kPa, 30 kPa, 35 kPa, 40 kPa, 45 kPa, 50 kPa, 80 kPa, or 101 kPa, or may be other values ​​within the above range, and is not limited thereto.

[0086] In some embodiments, the growth time of the vapor phase epitaxy is 2 hours to 1000 hours. Specifically, the growth time may be 2 hours, 5 hours, 10 hours, 50 hours, 100 hours, 150 hours, 200 hours, 250 hours, 300 hours, 350 hours, 400 hours, 500 hours, 600 hours, 650 hours, 700 hours, 800 hours, 900 hours, or 1000 hours, and of course, other values ​​between 2 hours and 1000 hours are also possible and are not limited here. The growth time of the vapor phase epitaxy is preferably 2 hours to 50 hours.

[0087] As can be understood, the process conditions of vapor phase growth (e.g., growth temperature, growth pressure, and growth time) all affect the growth of the silicon-based material in the pores of the carbon material, and controlling the vapor phase growth temperature, pressure, and time within the above ranges can ensure that decomposition growth does not occur before the reactive gas containing the active material enters the pores of the carbon material, and that decomposition growth occurs rapidly after entering the pores.

[0088] In some embodiments, the vapor deposition is performed in a protective atmosphere.

[0089] In some embodiments, the protective atmosphere comprises at least one of nitrogen gas, argon gas, helium gas, neon gas, krypton gas, and xenon gas.

[0090] In some embodiments, the reaction gas contains a silicon source gas raw material, and the silicon source gas raw material contains at least one of monosilane, disilane, monochlorosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane. When the silicon source gas raw material is monosilane, disilane, monochlorosilane, or dichlorosilane, it is in a gaseous state at room temperature. When the silicon source gas raw material is trichlorosilane or tetrachlorosilane, it is in a liquid state at room temperature. During the vapor phase growth process, the liquid silicon source is vaporized to become a gaseous silicon source.

[0091] In some embodiments, the flow rate of the silicon source gas is 1 L / min to 20 L / min, and specifically may be 1 L / min, 1.5 L / min, 2 L / min, 5 L / min, 6 L / min, 8 L / min, 10 L / min, 12 L / min, 15 L / min, 18 L / min, 20 L / min, etc., and is not limited thereto.

[0092] In some embodiments, the method further comprises cooling, washing, and drying the vapor deposited reaction product.

[0093] In some embodiments, the cleaning regimen comprises ultrasonic cleaning.

[0094] In some embodiments, the washing solvent comprises absolute ethanol.

[0095] In some embodiments, the washing time is 30 to 60 minutes, and may be specifically 30, 35, 40, 45, 50, 51, 53, 55, 56, 57, 58, 59, or 60 minutes, and of course, may be other values ​​within the above range and are not limited thereto.

[0096] In some embodiments, the drying time is 20 to 100 minutes. Specifically, the drying time may be 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 minutes, and is not limited thereto.

[0097] In some embodiments, the temperature of the drying treatment is 70°C to 90°C, and specifically may be 70°C, 75°C, 80°C, 81°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, or 90°C, or may be other values ​​between 70°C and 90°C, and is not limited thereto.

[0098] The present disclosure further provides a battery, the battery including the above-described negative electrode material.

[0099] The above are only preferred embodiments of the present disclosure, and do not limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present disclosure should be included within the protection scope of the present disclosure.

[0100] Performance Measurement (1) Regarding the etching process for the negative electrode material, The negative electrode material is immersed in a 1M nitric acid solution for 4 hours, and then a 20% mass fraction HF acid solution is added drop by drop to the negative electrode material until yellow smoke is generated and the solution no longer generates yellow smoke. Finally, the residue is decomposed with a 1M nitric acid solution, and then washed and dried to obtain a negative electrode material from which the silicon particles have been removed, i.e., a carbon material.

[0101] (2) Regarding the method for measuring the specific surface area of ​​the negative electrode material or the negative electrode material from which silicon particles have been removed, The specific surface area is measured using a Micromeritics TriStar 3000 specific surface area and pore size analysis instrument from the United States.

[0102] (3) Regarding the method for measuring the pore volume of the negative electrode material or the negative electrode material from which silicon particles have been removed, Measurements are made using an ASAP2460 instrument manufactured by Micromeritics, USA, and the pore volume V is calculated within the pore diameter range of 17 Å to 3000 Å using the BJH Desorption cumulative volume of pores model.

[0103] Micropore and mesopore analysis was performed using a Micromeretics ASAP2460. At liquid nitrogen temperatures, the equilibrium adsorption of nitrogen gas on a surface correlates with its pore size and other properties. The pore size can be calculated by combining the rules governing how the adsorption volume varies with relative pressure during the adsorption process and fitting multiple models. The software generates reports that use density functional theory (DFT) to calculate the pore size distribution, total pore volume, and pore volume within a certain range.

[0104] The true density P of the negative electrode material is measured, and the porosity of the negative electrode material = V / (V+1 / P) is calculated.

[0105] (4) Regarding the method for measuring the pore size of the negative electrode material or the negative electrode material from which silicon particles have been removed, An appropriate amount of sample particles is taken and the pore size is measured using a transmission electron microscope (TEM).

[0106] (5) The method for measuring the oil absorption of the negative electrode material or the negative electrode material from which silicon particles have been removed Using a Japanese Asahi Souken S-500 oil absorption analyzer, a certain mass of powder sample is placed in the mixing chamber, and oil (DBP) is added dropwise to the sample at a constant rate while the rotor is stirred at a constant speed. As the sample's oil absorption increases, the mixture changes from a free-flowing state to a semi-plastic aggregate, and during this process, the viscosity of the mixture gradually increases and reaches a peak. At the end of the measurement, the oil absorption of the sample (mL / 100g) is calculated from the amount of oil added at 70% of the maximum torque obtained from the torque curve generated by the change in viscosity characteristics.

[0107] (6) Regarding the method for measuring the average particle size of silicon particles, The nanosilicon particles are observed using a field emission scanning electron microscope or a transmission electron microscope, and the particle sizes of 5 to 10 nanosilicon particles are directly measured using a scale, and the average particle size is calculated as the final particle size of the nanosilicon particles.

[0108] (7) Regarding the method for measuring the particle size of the negative electrode material, The cumulative particle size distribution on a volume basis was measured using a laser particle size analyzer. 10 indicates the particle size corresponding to the cumulative particle size distribution percentage of the powder being 10%, and D 50 indicates the particle size corresponding to 50% of the cumulative particle size distribution percentage, and D 90 indicates the particle size corresponding to 90% of the cumulative particle size distribution percentage.

[0109] (8) The method for measuring the mass content of carbon elements in the negative electrode material: Using a German manufacturer Bruker's G4ICARUS HF infrared carbon and sulfur analyzer, the sample is burned under high-temperature, oxygen-enriched conditions, and the carbon and sulfur elements contained in the sample are oxidized to carbon dioxide and sulfur dioxide, respectively. The resulting gases enter the infrared detector along with the carrier gas, and the carbon and sulfur element contents can be calculated by quantitatively analyzing the changes in the carbon dioxide and sulfur dioxide signals.

[0110] (9) Regarding the method for measuring the mass content of silicon element in the negative electrode material, Using a Nanyang Kinyu SA2-9-17TP box-type atmosphere furnace, the sample is cauterized in an oxygen atmosphere, causing the silicon in the sample to react with silicon monoxide to form silica, and the carbon is burned and emitted as carbon dioxide, which is then weighed to calculate the silicon content.

[0111] (10) Regarding the method for measuring the tap density of the negative electrode material or the negative electrode material from which silicon particles have been removed, Using a special tap density meter manufactured by Hyaku, 100 g of sample is weighed and the tap density is measured by vibrating 3,000 times at 300 times / min.

[0112] (11) The method for measuring the mass content of nitrogen, oxygen, and hydrogen elements in the negative electrode material from which silicon particles have been removed. Using a German Verder ONH2000 oxygen, nitrogen, and hydrogen elemental analyzer, the sample is wrapped in flux and melted in an inert atmosphere, and the oxygen contained in the sample is reduced to carbon in a graphite crucible to form carbon dioxide. The resulting carbon dioxide enters the infrared detector along with the carrier gas, and the oxygen content can be calculated by quantitatively analyzing the carbon dioxide signal. The sample is wrapped in flux and melted in an inert atmosphere, and the nitrogen and hydrogen contained in the sample decompose to form stable nitrogen and hydrogen gases, respectively. The resulting nitrogen and hydrogen gases enter the thermal conductivity detector along with the carrier gas, and the mass content of the nitrogen and hydrogen elements can be calculated by quantitatively analyzing the change in heat quantity in the thermal conductivity detector.

[0113] (13) Regarding the measurement of the green density of negative electrode materials, Using a CARVER4350.22 green density meter manufactured by Micro, USA, a sample of a predetermined mass m is placed in a mold, a pressure of 1.0 T is applied, and after holding the pressure for 30 seconds, the pressure is removed and the thickness is measured to calculate the green density.

[0114] (14) Regarding pH measurement of negative electrode materials, Using a Mettler-Toledo FE20 pH meter, the potential difference measured in the solution by a working electrode cell consisting of a measurement electrode and a reference electrode is used to convert the pH value of the solution to be measured into a pH value using a linear relationship between the pH value of the solution to be measured and the magnitude of the potential of the working electrode, which is then converted into a pH value using an ammeter. 5 g of sample and 45 mL of water are weighed and stirred to disperse, then ultrasonicated for 5 minutes and allowed to stand for 10 minutes before measurement.

[0115] (15) Regarding the measurement of gas generation values, Carboxymethyl cellulose CMC was dispersed in water at a mass ratio of 1.4% to prepare an adhesive. After uniform dispersion, 10 g of the adhesive solution was mixed with 10 g of the negative electrode material to obtain a slurry. The slurry was placed in an aluminum plastic film bag, the mass of the slurry was recorded, and then sealed to form a sealed aluminum plastic film bag. The sealed aluminum plastic film bag was fixed to the bottom of a container and completely immersed in water. The volume of the aluminum plastic film bag was recorded. After being fixed for 24 hours, the volume of the aluminum plastic film bag was recorded again. The gas generation rate of the silicon negative electrode material was calculated based on the volume change of the aluminum plastic film bag, and the unit is mL / g.

[0116] (16) Regarding electrochemical performance measurements, 1) The initial discharge specific capacity and initial coulombic efficiency (ICE) were measured as follows: A negative electrode slurry was prepared using a mass ratio of 75:15:10 of negative electrode material, conductive carbon black, and polyacrylic acid (PPA), which was then applied to copper foil and dried to produce a negative electrode sheet. A metal lithium sheet was used as the counter electrode, and a button battery was assembled in a glove box filled with argon gas. Charge and discharge measurements were performed on the button battery within the charge and discharge range of 0.01 V to 5 V at a current density of 0.1 C, and the initial discharge specific capacity and initial coulombic efficiency (ICE) of the button battery were obtained.

[0117] 2) The capacity retention rate and electrode sheet thickness expansion rate after 50 cycles were measured as follows. A negative electrode slurry was prepared using a 92:2:2:2:2 mass ratio of negative electrode material, conductive carbon black (Super-P), conductive graphite (KS-6), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR). This slurry was then applied to copper foil and dried to produce a negative electrode sheet. The Si-C and graphite occupancy ratios in the mixture of the negative electrode material with a carbon coating layer and graphite were determined based on the initial reversible specific capacity of each material and the intended capacity of their blend. A lithium metal sheet was used as the counter electrode, and a button battery was assembled in a glove box filled with argon gas. The button battery was subjected to 50 charge-discharge measurements at a current density of 1 C between 0.01 V and 5 V, and the capacity retention rate and electrode sheet thickness expansion rate after 50 cycles were measured.

[0118] (17) Regarding the method for measuring complete dissolution of negative electrode materials, A PE / Agilent OPTIMA 8000 / 5000 inductively coupled plasma optical emission spectrometer and a Sigma SGM.M8 / 10A muffle furnace are used. The sample is first calcined in the muffle furnace to remove carbon (if present), then decomposed with HF to remove silicon, and the residue is further decomposed with nitric acid. The volume is then measured using an ICP spectrometer.

[0119] (18) ICP measurement method for negative electrode materials The negative electrode material sample is dissolved in aqua regia, filtered, and the volume is measured, and the element contents are measured using an ICP spectrometer.

[0120] (19) A method for measuring the fractal dimension of particles in negative electrode materials. To measure the fractal dimension of particles, use the Fractal Box Count plugin. Open the picture, convert it to 8-bit, and binarize it (Image → Adjust → Threshold), then open the plugin (Analyze → Tools → Fractal Box Count). After initializing the parameters and binarizing the picture, the white area (pixel value = 255) is the desired signal, and the black area is the background; check Black Background. Perform linear regression on the data within the selected frame to obtain the linear regression result and fractal dimension X0.

[0121] (Example 1-1) (1) Specific surface area is 1800m 2 / g and pore volume of 1.2 cm 3 / g, maximum pore size 9 nm, average pore size 1.81 nm, porosity 50%, pH 8, tap density 0.39 g / cm 3 A porous carbon material was selected, in which pores with a pore size of 1.5 nm or less accounted for 22% of the total pore volume, pores with a pore size of 1.6 nm or less accounted for 35% of the total pore volume, pores with a pore size of 2 nm or less accounted for 82% of the total pore volume, and pores with a pore size of 5 nm or less accounted for 95% of the total pore volume, and the B' of the carbon material was 1.5, the C2' of the carbon material was 18, and the average shape factor of the carbon material was 0.89.

[0122] (2) The porous carbon was placed in a chemical vapor deposition furnace, and monosilane was used as the working gas. The growth temperature was 500°C, the growth time was 10 hours, and the flow rate of monosilane was 2 L / min to obtain the negative electrode material. The negative electrode material prepared in this example includes a carbon material and a silicon-based material, the carbon material has pores, and at least a portion of the silicon-based material is filled in the pores. The average shape factor F0 of the negative electrode material is 0.9. Other parameters of the negative electrode material in this example are shown in detail in Table 2.

[0123] (Example 1-2) The differences from Example 1-1 are as follows: a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. The detailed parameters of the negative electrode material in this example are shown in Table 2.

[0124] (Examples 1-3) The differences from Example 1-1 are as follows: a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. The detailed parameters of the negative electrode material in this example are shown in Table 2.

[0125] (Examples 1-4) The differences from Example 1-1 are as follows: a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. The detailed parameters of the negative electrode material in this example are shown in Table 2.

[0126] (Examples 1-5) The differences from Example 1-1 are as follows: a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. The detailed parameters of the negative electrode material in this example are shown in Table 2.

[0127] (Examples 1 to 6) The differences from Example 1-1 are as follows: a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. The detailed parameters of the negative electrode material in this example are shown in Table 2.

[0128] (Examples 1-7) The differences from Example 1-1 are as follows: a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. The detailed parameters of the negative electrode material in this example are shown in Table 2.

[0129] (Examples 1-8) The differences from Example 1-1 are as follows: a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. The detailed parameters of the negative electrode material in this example are shown in Table 2.

[0130] Examples 1-9 The differences from Example 1-1 are as follows: a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. The detailed parameters of the negative electrode material in this example are shown in Table 2.

[0131] Examples 1-10 The differences from Example 1-1 are as follows: a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. The detailed parameters of the negative electrode material in this example are shown in Table 2.

[0132] (Examples 1-11) The differences from Example 1 are as follows: a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. Table 2 shows the details of the parameters of the negative electrode material in this example.

[0133] (Examples 1-12) The differences from Example 1 are as follows: a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. Table 2 shows the details of the parameters of the negative electrode material in this example.

[0134] (Examples 1-13) The differences from Example 1 are as follows: a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. Table 2 shows the details of the parameters of the negative electrode material in this example.

[0135] (Examples 1-14) The differences from Example 1 are as follows: a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. Table 2 shows the details of the parameters of the negative electrode material in this example.

[0136] (Examples 1-15) The differences from Example 1 are as follows: a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. The porous carbon was placed in a chemical vapor deposition furnace, and monosilane was used as the working gas. The growth temperature was 550°C, the growth time was 9 hours, and the flow rate of monosilane was 1 L / min to obtain the negative electrode material. Table 2 shows the details of the parameters of the negative electrode material in this example.

[0137] (Examples 1-16) Unlike Example 1, a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. Table 2 shows the details of the parameters of the negative electrode material in this example.

[0138] (Examples 1-17) The differences from Example 1 are as follows: a carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. Table 2 shows the details of the parameters of the negative electrode material in this example.

[0139] (Comparative Example 1-1) The differences from Example 1 are as follows: A carbon material having pores was selected, and the specific parameters of the pore structure of the carbon material are shown in Table 1. Table 2 shows the details of the parameters of the negative electrode material in this example.

[0140] [Table 1]

[0141] [Table 2]

[0142] [Table 3]

[0143] [Table 4]

[0144] As can be seen from the results shown in Tables 1 to 3, the negative electrode materials produced in Examples 1-1 to 1-15 of the present disclosure all had high initial discharge specific capacity, initial coulombic efficiency, and capacity retention rate after 50 cycles, and the thickness expansion rate of the electrode sheet after 50 cycles of the material was low. This is because the particle shape of the negative electrode material prepared in this example is close to spherical particles, and a pore structure with an appropriate number and appropriate pore size is distributed inside the spherical particles. The spherical particles can increase the isotropy of the negative electrode material, and during charging and discharging, the negative electrode material can shrink and expand relatively uniformly along the radial direction, reducing the stress concentration problem caused by the volume expansion of the silicon-based material. Furthermore, the average shape factor of the negative electrode material particles is maintained within the above range, and the higher the shape similarity of each negative electrode material particle, the more uniform the stress in each direction experienced by each negative electrode material particle in the negative electrode active material layer on the surface of the electrode sheet after the negative electrode material is applied to form a negative electrode sheet. This is beneficial for the uniform release of expansion stress in each direction, maintaining the stability of the particle structure, reducing particle powdering, and thereby improving the cycle performance of the material.

[0145] As can be seen from the measurement data of Examples 1-1, 1-14, 1-15, and 1-16 to 1-17, when the average shape factor F0 of the negative electrode material is controlled within the range of 0.65 to 1, the negative electrode material simultaneously satisfies 8≦C1≦20, the negative electrode material has an appropriate number of pores with an appropriate pore size, and the negative electrode material has enough space to alleviate the expansion of the active material in the negative electrode material, and at the same time, the occurrence of side reactions between the negative electrode material and the electrolyte due to the negative electrode material's excessively large specific surface area is reduced, thereby comprehensively improving the performance of the negative electrode material in all aspects. Therefore, the data of Examples 1-16 and 1-17 are more clearly shown.

[0146] The average shape factor F0 of the negative electrode material of Comparative Example 1-1 was too small, and the particle shape was obviously angular. During the roll pressing process of the electrode sheet, the negative electrode material particles were prone to partial rupture, which led to increased side reactions between the negative electrode material and the electrolyte and the consumption of more active lithium ions, resulting in a decrease in the initial efficiency of the negative electrode material. During the charge and discharge process, local stress concentration occurred in the negative electrode material particles, causing the particles to further fracture and powder, and the cycle performance of the material was reduced.

[0147] In an ideal state, the closer the average shape factor of the negative electrode material is to 1, the more spherical the particles become, and the more uniformly the negative electrode material can contract and expand in the radial direction, the less negative electrode material particle fracture occurs. In the above-mentioned Examples 1-1 to 1-17, the applicant selected and combined appropriate carbon material and silicon particles through pre-sorting of the carbon material, which can improve the average shape factor of the negative electrode material, but this also increases production costs. In addition, pre-sorting of the carbon material is time-consuming.

[0148] Generally, to improve the average shape factor of a negative electrode material, the negative electrode material is subjected to a spheroidizing process, but a large amount of heat is generated during the spheroidizing process, causing partial oxidation of silicon particles in the negative electrode material and a decrease in the specific capacity of the negative electrode material. Furthermore, during the spheroidizing process, some of the negative electrode material is powdered, increasing side reactions in the negative electrode material and affecting the cycle characteristics of the negative electrode material.

[0149] Therefore, the present inventor has found from further research into negative electrode materials that even when the average shape factor F0 of the negative electrode material is controlled within the range of 0.65 to 0.79, the negative electrode material can still meet the expected usage needs and significantly reduce production costs.

[0150] Example 2-1 (1) Coconut shells were crushed in a crusher and ground in an automatic mortar, then sieved to a particle size of 45 μm or less for use. The crushed coconut shells were placed in a vacuum freeze dryer and freeze-dried for 24 hours. They were then placed in a tubular furnace and treated in an argon gas atmosphere at 750°C for 120 minutes. They were then immersed in dilute hydrochloric acid (10 wt%) for 6 hours to remove inorganic impurities. They were then washed with deionized water and absolute ethanol until the filtrate became neutral, and left overnight in a 60°C fan oven to obtain an intermediate.

[0151] (2) The intermediate was placed on a quartz boat and placed in the center of a quartz tube in a tubular furnace. Before heating, high-purity argon gas was passed through the boat for 30 minutes to purge the air inside the tube. The temperature was then increased to 1000°C at a rate of 10°C / min, and the intermediate was carbonized at a constant temperature for 1 hour. The carbonized material was then cooled to room temperature.

[0152] (3) The carbonized material was mixed with a KOH solution (KOH concentration in the solution was 0.2 g / ml) in a mass ratio of 1:2, and evaporated at 60°C for 24 hours to obtain a dry mixed sample. The mixed sample was placed in a tubular furnace, heated to 800°C at a heating rate of 5°C / min, maintained at that temperature for 2 hours, and then allowed to cool naturally to room temperature. The black powder sample was placed in dilute hydrochloric acid (mass fraction 10 wt%) and immersed for 24 hours. After washing and drying, it was ground in a ball mill-type fluidized bed jet mill to obtain a carbon material.

[0153] (4) The carbon material was placed in a chemical vapor deposition furnace, and monosilane was used as the working gas. The growth temperature was 500°C, the growth time was 10 hours, and the flow rate of monosilane was 2 L / min to obtain the negative electrode material. The negative electrode material prepared in this example includes a carbon material and silicon particles, the carbon material has pores, and at least some of the silicon particles are filled in the pores. The negative electrode material has an average shape factor F0 of 0.7. The remaining parameters of the negative electrode material in this example are detailed in Table 2.

[0154] (Example 2-2) (1) Coconut shells were crushed in a crusher and ground in an automatic mortar, then sieved to a particle size of 45 μm or less for use. The crushed coconut shells were placed in a vacuum freeze dryer and freeze-dried for 24 hours. They were then placed in a tubular furnace and treated in an argon gas atmosphere at 750°C for 120 minutes. They were then immersed in dilute hydrochloric acid (10 wt%) for 6 hours to remove inorganic impurities. They were then washed with deionized water and absolute ethanol until the filtrate became neutral, and left overnight in a 60°C fan oven to obtain an intermediate.

[0155] (2) The intermediate was placed on a quartz boat and placed in the center of a quartz tube in a tubular furnace. Before heating, high-purity argon gas was passed through the boat for 30 minutes to purge the air inside the tube. The temperature was then increased to 700°C at a rate of 10°C / min, held at this temperature for 1 hour, and then cooled to room temperature to obtain a carbonized material.

[0156] (3) The carbonized material was mixed with a KOH solution (KOH concentration in the solution was 0.2 g / ml) in a mass ratio of 1:4, and evaporated at 60°C for 24 hours to obtain a dry mixed sample. The mixed sample was placed in a tubular furnace, heated to 800°C at a heating rate of 5°C / min, maintained at that temperature for 2 hours, and then allowed to cool naturally to room temperature. The black powder sample was placed in dilute hydrochloric acid (mass fraction 10 wt%) and immersed for 24 hours. After washing and drying, it was ground in a ball mill-type fluidized bed jet mill to obtain a carbon material.

[0157] (4) The carbon material was placed in a chemical vapor deposition furnace, disilane was used as the working gas, the growth temperature was 450°C, the growth time was 16 hours, and the flow rate of disilane was 3 L / min to obtain the negative electrode material. The negative electrode material prepared in this example includes a carbon material and silicon particles, the carbon material has pores, and at least some of the silicon particles are filled in the pores. The negative electrode material has an average shape factor F0 of 0.73. The remaining parameters of the negative electrode material in this example are detailed in Table 2.

[0158] (Example 2-3) (1) Coconut shells were crushed in a crusher and ground in an automatic mortar, then sieved to a particle size of 45 μm or less for use. The crushed coconut shells were placed in a vacuum freeze dryer and freeze-dried for 24 hours. They were then placed in a tubular furnace and treated in an argon gas atmosphere at 750°C for 120 minutes. They were then immersed in dilute hydrochloric acid (10 wt%) for 6 hours to remove inorganic impurities. They were then washed with deionized water and absolute ethanol until the filtrate became neutral, and left overnight in a 60°C fan oven to obtain an intermediate.

[0159] (2) The intermediate was placed on a quartz boat and placed in the center of a quartz tube in a tubular furnace. Before heating, high-purity argon gas was passed through the boat for 30 minutes to purge the air inside the tube. The temperature was then increased to 1300°C at a rate of 10°C / min, held at that temperature for 1 hour, and then cooled to room temperature to obtain a carbonized material.

[0160] (3) The carbonized material was mixed with a KOH solution (KOH concentration in the solution was 0.2 g / ml) in a mass ratio of 1:6, and evaporated at 60°C for 24 hours to obtain a dry mixed sample. The mixed sample was placed in a tubular furnace, heated to 800°C at a heating rate of 5°C / min, maintained at that temperature for 2 hours, and then allowed to cool naturally to room temperature. The black powder sample was placed in dilute hydrochloric acid (mass fraction 10 wt%) and immersed for 24 hours. After washing and drying, it was ground in a ball mill-type fluidized bed jet mill to obtain a carbon material.

[0161] (4) The carbon material was placed in a chemical vapor deposition furnace, and monosilane was used as the working gas. The growth temperature was 550°C, the growth time was 6 hours, and the flow rate of monosilane was 1 L / min to obtain the negative electrode material. The negative electrode material prepared in this example includes a carbon material and silicon particles, the carbon material has pores, and at least some of the silicon particles are filled in the pores. The negative electrode material has an average shape factor F0 of 0.66.

[0162] (Examples 2-4) (1) Coconut shells were crushed in a crusher and ground in an automatic mortar, then sieved to a particle size of 45 μm or less for use. The crushed coconut shells were placed in a vacuum freeze dryer and freeze-dried for 24 hours. They were then placed in a tubular furnace and treated in an argon gas atmosphere at 750°C for 120 minutes. They were then immersed in dilute hydrochloric acid (10 wt%) for 6 hours to remove inorganic impurities. They were then washed with deionized water and absolute ethanol until the filtrate became neutral, and left overnight in a 60°C fan oven to obtain an intermediate.

[0163] (2) The intermediate was placed on a quartz boat and placed in the center of a quartz tube in a tubular furnace. Before heating, high-purity argon gas was passed through the boat for 30 minutes to purge the air inside the tube. The temperature was then increased to 900°C at a rate of 10°C / min, held at that temperature for 1 hour, and then cooled to room temperature to obtain a carbonized material.

[0164] (3) The carbonized material was mixed with a KOH solution (KOH concentration in the solution was 0.2 g / ml) in a mass ratio of 1:2, and evaporated at 60°C for 24 hours to obtain a dry mixed sample. The mixed sample was placed in a tubular furnace, heated to 800°C at a heating rate of 5°C / min, maintained at that temperature for 2 hours, and then allowed to cool naturally to room temperature. The black powder sample was placed in dilute hydrochloric acid (mass fraction 10 wt%) and immersed for 24 hours. After washing and drying, it was ground in a ball mill-type fluidized bed jet mill to obtain a carbon material.

[0165] (4) The carbon material was placed in a chemical vapor deposition furnace, and monosilane was used as the working gas. The growth temperature was 400°C, the growth time was 18 hours, and the flow rate of monosilane was 3 L / min to obtain the negative electrode material. The negative electrode material prepared in this example includes a carbon material and silicon particles, the carbon material has pores, and at least some of the silicon particles are filled in the pores. The negative electrode material has an average shape factor F0 of 0.79.

[0166] (Examples 2-5) The differences from Example 2-1 are as follows: The carbon source precursor employed was different, with bamboo being the carbon source precursor.

[0167] (Examples 2-6) The differences from Example 2-1 are as follows: Step (1) was not performed.

[0168] (Examples 2-7) The differences from Example 2-1 are as follows: (3) The carbonized material and KOH solution (the KOH concentration in the solution was 0.2 g / ml) were mixed in a mass ratio of 1:10, and the mixture was evaporated at 60°C for 24 h to obtain a dry mixed sample.

[0169] (Examples 2-8) The differences from Example 2-1 are as follows: (3) The carbonized material and KOH solution (the KOH concentration in the solution was 0.2 g / ml) were mixed in a mass ratio of 1:0.2, and the mixture was evaporated at 60°C for 24 hours to obtain a dry mixed sample.

[0170] (Examples 2-9) The differences from Examples 2-3 are as follows: (3) The carbonized material was mixed with a KOH solution (KOH concentration in the solution was 0.2 g / ml) in a mass ratio of 1:1.5, and evaporated at 60°C for 24 hours to obtain a dry mixed sample. The mixed sample was placed in a tubular furnace, heated to 800°C at a heating rate of 5°C / min, maintained at that temperature for 2 hours, and then allowed to cool naturally to room temperature. The black powder sample was placed in dilute hydrochloric acid (mass fraction 10 wt%) and immersed for 24 hours. After washing and drying, it was ground in a ball mill-type fluidized bed jet mill to obtain a carbon material.

[0171] (Comparative Example 2-1) The differences from Example 2-1 are as follows: (3) The carbonized material was mixed with a KOH solution (KOH concentration in the solution was 0.2 g / ml) in a mass ratio of 1:4, and evaporated at 60°C for 24 hours to obtain a dry mixed sample. The mixed sample was placed in a tubular furnace, heated to 800°C at a heating rate of 5°C / min, maintained at that temperature for 2 hours, and then allowed to cool naturally to room temperature. The black powder sample was placed in dilute hydrochloric acid (mass fraction 10 wt%) and immersed for 24 hours. After washing and drying, it was crushed in a ball mill-type impact nail jet mill to obtain a carbon material.

[0172] (Comparative Example 2-2) The differences from Example 2-1 are as follows: (4) The carbon material was placed in a chemical vapor deposition furnace, and monosilane was used as the working gas. The growth temperature was 500°C, the growth time was 10 hours, and the flow rate of monosilane was 2 L / min. The growth product was then pulverized using a ball mill-type fluidized bed jet mill to obtain a carbon material. The negative electrode material prepared in this example includes a carbon material and silicon particles, the carbon material has pores, and at least some of the silicon particles are filled in the pores. The negative electrode material has an average shape factor F0 of 0.86.

[0173] [Table 5]

[0174] [Table 6]

[0175] [Table 7]

[0176] [Table 8]

[0177] As can be seen from the results shown in Tables 4 to 6, the negative electrode materials prepared in the examples of the present disclosure have high initial discharge specific capacity, high initial coulombic efficiency, and high capacity retention after 50 cycles, and the thickness expansion rate of the electrode sheet after 50 cycles is low. This is because controlling the average shape factor of the negative electrode material prepared in this example within the range of 0.65 to 0.79 effectively reduces the apparent corners of the particles, allowing the negative electrode material to shrink and expand relatively uniformly along the radial direction during charging and discharging, reducing the stress concentration problem near the corners caused by the volume expansion of the silicon particles in the negative electrode material. This is beneficial to maintaining the stability of the particle structure of the negative electrode material and reducing particle pulverization of the negative electrode material. Furthermore, maintaining the average shape factor of the negative electrode material particles within this range reduces the gaps between the negative electrode material particles, which is beneficial to improving the green density of the negative electrode material, allowing for sufficient electrolyte infiltration, and improving the cycle performance of the negative electrode material.

[0178] As can be seen from the measurement data of Example 2-1 and Example 2-6, the negative electrode material prepared in Example 2-6 without performing step (1) had a high impurity content. The high impurity content reduced the conductivity of the material and also caused some of the voids in the carbon material to be occupied by impurity elements, resulting in a slightly low Si content in the carbon material. As a result, the initial charge-discharge specific capacity and initial coulombic efficiency of the negative electrode material prepared in Example 2-6 were slightly low.

[0179] As can be seen from the measurement data of Examples 2-1 to 2-7 and Example 2-8, the carbon material of Example 2-8 has too low an oil absorption capacity, causing the oil absorption capacity of the negative electrode material after filling with silicon particles to be somewhat too low, resulting in a decrease in the specific capacity of the negative electrode material, a decrease in the infiltration characteristics of the negative electrode material, and a somewhat lower initial coulombic efficiency of the negative electrode material than in Example 2-1.

[0180] Comparative Example 2-1 uses ball mill-type impact nail jet mill grinding, and the carbon material has obvious corners. The average shape factor of the produced negative electrode material is too small, that is, the particles have obvious corners. During the charge and discharge process, the local expansion stress of the negative electrode material is too large, which reduces the stability of the particle structure of the negative electrode material and significantly increases the expansion rate of the negative electrode material.

[0181] In Comparative Example 2-2, after vapor growth of silicon particles, the grown product was pulverized using a ball mill-type fluidized bed jet mill, which improved the average shape factor of the negative electrode material. However, a large amount of heat was generated during the spheroidization process, which caused partial oxidation of the silicon particles in the negative electrode material and reduced the specific capacity of the negative electrode material. In addition, some of the negative electrode material was powdered during the spheroidization process, which also caused an increase in side reactions in the negative electrode material and affected the cycle characteristics of the negative electrode material.

[0182] As can be seen from the measurement data of Examples 2-1 to 2-8, when the average shape factor of the negative electrode material particles is controlled within the above range, the problem of stress concentration near the corners due to volume expansion of the silicon particles in the negative electrode material can be reduced, which is advantageous for maintaining the stability of the particle structure of the negative electrode material and reducing the powdering of the negative electrode material particles. It also reduces the gaps between the negative electrode material particles, which is advantageous for improving the green density of the negative electrode material, allowing sufficient electrolyte infiltration, and improving the cycle characteristics of the negative electrode material.

[0183] [CROSS-REFERENCE TO RELATED APPLICATIONS] This disclosure claims priority to a Chinese patent application filed with the State Intellectual Property Office of the People's Republic of China on August 29, 2023, bearing application number 202311101191.6, entitled "Anode Material and Battery," and to a Chinese patent application filed with the State Intellectual Property Office of the People's Republic of China on November 29, 2023, bearing application number 202311605506.0, entitled "Anode Material and Battery," and to a Chinese patent application filed with the State Intellectual Property Office of the People's Republic of China on February 7, 2024, bearing application number 202410172027.2, entitled "Anode Material and Battery," the entire contents of which are incorporated herein by reference.

Claims

1. an anode material comprising a carbon material and silicon particles, the anode material having pores; The average shape factor of the negative electrode material is F ０ and 0.65≦F ０ <1, The average shape factor F of the negative electrode material ０ is measured in the following manner: Ten negative electrode material particles were randomly selected, and the cross-sectional area S of each negative electrode material particle was calculated. ｎ and circumference C ｎ Measure F ｎ = 4 * π * S ｎ / C ｎ ２ where n is a natural number selected from 1 to 10, and the shape factor F ｎ The average value is calculated as the average shape factor F of the negative electrode material. ０ A negative electrode material characterized by:

2. N ２ the negative electrode material and the negative electrode material from which the silicon particles have been removed are measured using an adsorption / desorption method, and it is found that the ratio of the volume of nitrogen gas adsorbed at 90% partial pressure to the volume of nitrogen gas adsorbed at 10% partial pressure of the negative electrode material is A, and 1.3≦A≦2.5; 2. The negative electrode material according to claim 1, wherein the negative electrode material from which silicon particles have been removed has a ratio B of the volume of nitrogen gas adsorbed at 90% partial pressure to the volume of nitrogen gas adsorbed at 10% partial pressure, where 1≦B≦1.9 and A / B>1.

3. At least some of the silicon particles are filled within the pores of the carbon material; and / or 2. The negative electrode material according to claim 1, wherein the silicon particles include at least one of amorphous silicon, crystalline silicon, silicon oxide, silicon alloy, and a composite of crystalline silicon and amorphous silicon.

4. The total pore volume of the negative electrode material is 0.001 cm ３ / g to 0.4 cm ３ 2. The negative electrode material according to claim 1, wherein the Cr content is 1.0 / g.

5. The negative electrode material is (1) The pores in the negative electrode material include micropores, and the volume occupancy of the micropores in all pores is ≦5%; (2) The pores in the negative electrode material include mesopores, and the volume occupancy rate of the mesopores in all pores is 87% to 97%; (3) The negative electrode material according to claim 1, wherein the pores in the negative electrode material include macropores, and the macropores occupy a volume ratio of all pores of ≦13%.

6. The negative electrode material is (1) The total pore volume of the negative electrode material after removing the silicon particles is 0.2 cm ３ / g to 2.0 cm ３ / g, (2) The pores in the negative electrode material from which the silicon particles have been removed include micropores, and the volume occupancy rate of the micropores in all pores is ≥ 80%; (3) In the anode material from which silicon particles have been removed, the pores having a diameter of 5.0 nm or less account for ≥ 90% of the total pore volume.

7. The particle size D of the negative electrode material ５０ 2 μm≦D ５０ ≦20 μm, and 0.9≦(D ９０ -D １０ ) / D ５０ 2. The negative electrode material according to claim 1, wherein the ionic liquid has a molecular weight of ≦5.

8. 2. The negative electrode material according to claim 1, wherein an amount of gas generated from a negative electrode slurry produced from the negative electrode material after being placed in a 25°C environment for 24 hours is ≦1 mL / g, and an amount of gas generated from a negative electrode slurry produced from the negative electrode material after being placed in a 45°C environment for 24 hours is ≦2 mL / g.

9. The average shape factor of the negative electrode material is F ０ and 0.65≦F ０ 9. The negative electrode material according to claim 1, wherein the ρ is less than 0.

7.

10. The oil absorption of the negative electrode material is Q １ mL / 100g, 30≦Q １ ≦80, and the oil absorption of the negative electrode material from which the silicon particles have been removed is Q ２ mL / 100g, 120≦Q2≦200, and (Q ２ -Q １ ) / Q １ 10. The negative electrode material according to claim 9, wherein the ρ is >0.

5.

11. The negative electrode material is (1) The green density of the negative electrode material is 0.80 g / cm ３ ~1.30 g / cm ３ The characteristic that (2) The negative electrode material has a powder conductivity of 0.5 S / cm to 2 S / cm at 20 kN; (3) The mass content of carbon element in the negative electrode material is 40% to 60%; (4) The negative electrode material according to claim 9, wherein the mass content of silicon element in the negative electrode material is 35% to 55%.

12. The average shape factor of the negative electrode material is F ０ and 0.7≦F ０ ≦0.8, and the specific surface area of ​​the negative electrode material is S1m ２ / g, and the total pore volume of the negative electrode material is P1cm ３ / g, C1=S1 / (P1*100), and 8≦C1≦20.

13. The specific surface area of ​​the negative electrode material from which the silicon particles have been removed is S2m ２ / g, and the total pore volume of the negative electrode material from which the silicon particles have been removed is P2 cm ３ / g, C2=S2 / (P2*100), and 10≦C2≦25.

14. 14. The negative electrode material according to claim 13, wherein 5≦S1≦10, 0.001≦P1≦0.1, 1300≦S2≦2500, and 0.5≦P2≦2.

0.

15. A battery comprising the negative electrode material according to any one of claims 1 to 14.

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