Anode materials and batteries

Abstract

The present application relates to an anode material and a battery, the anode material comprising secondary particles, the secondary particles comprising nano-primary silicon particles, the nano-primary silicon particles comprising at least one silicon crystal grain, the silicon crystal grain having an average particle size Ds nm, the average particle size Dn nm of the nano-primary silicon particles, and a degree of crystallinity A, where A=Dn / Ds and 1≦A≦200. By exploring the relationship between the size of the nano-primary silicon particles and the size of the silicon crystal grain, it is possible to reduce the stress concentration problem that occurs during the lithium release process of the nano-primary silicon particles, further improving the structural stability of the anode material and reducing the expansion rate of the anode material, thereby improving the electrochemical performance and cycle performance of the anode material.

Description

[Technical Field]

[0001] This application relates to the field of anode materials technology, and more particularly to anode materials and batteries. [Background technology]

[0002] Lithium-ion batteries have been widely used in electric vehicles and consumer electronic products due to their advantages of high energy density, high output power, long cycle life, and low environmental pollution.

[0003] To improve the energy density of batteries, research and development of silicon anode materials has become increasingly mature. However, silicon anode materials undergo large volume expansion (>300%) during the lithium release process. During charging and discharging, silicon anode materials pulverize and fall off the current collector, resulting in loss of electrical contact between the active material and the current collector, resulting in poor electrochemical performance, capacity fade, and reduced cycling stability, making them unsuitable for commercial application. To improve the conductivity and cycling stability of silicon anode materials, carbon coatings can be used. However, traditional carbon coating manufacturing methods involve complex steps, and simple carbon coatings cannot effectively improve the electrochemical performance of silicon-carbon anodes.

[0004] Based on the above, there is a strong demand for the development of silicon carbon anode materials that have low expansion performance over long cycles. Summary of the Invention [Problem to be solved by the invention]

[0005] The present application provides a negative electrode material and a battery, which has excellent cycle stability and excellent expansion performance. [Means for solving the problem]

[0006] In a first aspect, the present application provides a negative electrode material, the negative electrode material comprising secondary particles, the secondary particles comprising silicon nano-primary particles; The silicon nano primary particles include at least one silicon crystal grain, the silicon crystal grain having an average particle size of Ds nm, and the silicon nano primary particles having an average particle size of Dn nm; The degree of crystallinity of the silicon nanoparticles is A, where A=Dn / Ds, and 1≦A≦200. [Effects of the Invention]

[0007] The technical solution of the present application has at least the following beneficial effects: The anode material provided herein explores the relationship between the size of nano silicon primary particles and the size of silicon crystal grains, thereby controlling the degree of crystallinity of the nano silicon primary particles for the same size. This can better alleviate the stress concentration problem that occurs during the lithium release process of the nano silicon primary particles, favoring uniform stress release, ensuring the structural stability of the nano silicon primary particles, and reducing particle pulverization. For the same primary particle size, if the degree of crystallinity A of the nano silicon primary particles is too large, it indicates that the silicon crystal grain size is too small. If the silicon crystal grain size is too small, the grain boundaries between the silicon crystal grains will gradually disappear during the lithiation process, eventually forming large-sized crystal grains, i.e., electrochemical sintering. After electrochemical sintering, the grain boundaries between the silicon crystal grains will disappear, and the silicon crystal grains will become larger. This will increase the local stress of the nano silicon primary particles after the anode material absorbs lithium, leading to increased structural instability of the anode material, resulting in a decrease in the cycle performance and capacity of the anode material. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic structural diagram of the negative electrode material provided in this example. [Figure 2a] FIG. 2a is a schematic diagram of the structure of the silicon nanoparticle primary particles in the negative electrode material provided in this example. [Figure 2b] FIG. 2b is a schematic diagram of the structure of the silicon nanoparticle primary particles in the negative electrode material provided in this example. [Figure 3a] FIG. 3a is another schematic structural diagram of the silicon nanoparticles in the negative electrode material provided in this example. [Figure 3b] FIG. 3b is another schematic structural diagram of the silicon nanoparticles in the negative electrode material provided in this example. [Figure 4] FIG. 4 is a schematic diagram of the method for producing the negative electrode material provided in this example. [Figure 5] FIG. 5 is a scanning electron micrograph of the negative electrode material provided in Example 1. [Figure 6] FIG. 6 is an XRD diagram of the negative electrode material provided in Example 1. [Figure 7] FIG. 7 is a graph of the cycling characteristics of the negative electrode material provided in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] In order to better understand the technical solution of the present application, the embodiments of the present application will be described in detail below with reference to the drawings.

[0010] Obviously, the described embodiments are only some of the embodiments of the present application, and not all of the embodiments, and all other embodiments obtained by those skilled in the art based on the embodiments of the present application without any creative effort fall within the scope of protection of the present application.

[0011] The terminology used in the examples herein is for the purpose of describing particular examples only and is not intended to be limiting of the present application. As used in the examples herein and the appended claims, the singular forms "a," "the," and "the" are intended to include the plural forms unless the context clearly dictates otherwise.

[0012] It should be understood that the term "and / or" used herein is only a relational relationship describing related objects, and indicates that three types of relations can exist, for example, A and / or B can indicate three situations: A exists alone, A and B exist together, and B exists alone. In addition, the character " / " in this specification generally indicates that the context is an "or" relationship.

[0013] Currently, in lithium-ion batteries, the anode material is one of the key materials that affect its charge / discharge performance, and research and development of high-capacity anode materials is becoming increasingly mature in order to improve battery energy density. However, these anode materials undergo large volume expansion during the alloying process with lithium, and the anode material pulverizes and falls off the current collector during the charge / discharge process, causing a loss of electrical contact between the anode material and the current collector, resulting in poor electrochemical performance, capacity fade, and reduced cycle stability, making them difficult to commercialize.

[0014] In the process of releasing lithium, silicon materials undergo changes in their macrostructure, and these transformations are closely related to the size of the crystal grains, silicon particles, and the size of the secondary particles formed in the silicon material. Currently, there is no suitable balance point for the size ratio of silicon crystal grains, silicon primary particles, and secondary particles, and in the process of releasing lithium, silicon-containing negative electrode materials experience stress concentration, which makes it easy for the particles of the negative electrode material to crack, resulting in poor structural stability of the negative electrode material.

[0015] In a first aspect, the present application provides a negative electrode material, and as shown in FIG. 1, the negative electrode material includes secondary particles 12, and the secondary particles 12 include silicon nanoprimary particles 11.

[0016] As shown in Figures 2a and 2b, the silicon nano primary particle 11 includes at least one silicon crystal grain 112, the average grain size of the silicon crystal grain 112 is Ds nm, the average grain size of the silicon nano primary particle 11 is Dn nm, and the crystalline degree of the silicon nano primary particle 11 is A, where A = Dn / Ds and 1≦A≦200.

[0017] In the above solution, by exploring the relationship between the size of the nano silicon primary particles 11 and the size of the silicon crystal grains 12, the crystallinity A of the nano silicon primary particles 11 can be controlled for the same nano silicon primary particle size, which can better alleviate the stress concentration problem that occurs during the lithium release process of the nano silicon primary particles 11, favoring uniform stress release of the nano silicon primary particles, ensuring structural stability of the nano silicon primary particles 11, and reducing particle pulverization. For the same nano silicon primary particle size, if the crystallinity A of the nano silicon primary particles 11 is too large, it indicates that the size of the silicon crystal grains 12 is too small. If the size of the silicon crystal grains 12 is too small, the grain boundaries between the silicon crystal grains will gradually disappear during the lithiation process, eventually forming large-sized crystal grains, i.e., electrochemical sintering. After electrochemical sintering, the grain boundaries between the silicon crystal grains will disappear and the silicon crystal grains will become larger. This will increase the local stress of the nano silicon primary particles 11 after the negative electrode material absorbs lithium, leading to increased structural instability of the negative electrode material and resulting in a decrease in the cycle performance and capacity of the negative electrode material. Current research has shown that when the size of silicon crystal grains is less than 10 nm, significant electrochemical sintering occurs, and the degree of sintering cannot be reduced unless the charging current is controlled, or the silicon crystal grains or silicon particles are isolated by carbon.

[0018] In some embodiments, the average particle size of the silicon nano primary particles 11 is Dn nm, where 1≦Dn≦200, and may be specifically 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 190 nm, or 200 nm, etc., but is not limited thereto.

[0019] In some embodiments, the average particle size of the silicon crystal grains 112 is Ds nm, where 1 ≤ Ds ≤ 100. Specifically, it may be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm, etc., and is not limited herein.

[0020] In some embodiments, the degree of crystallinity of the silicon nano primary particles 11 is A, where A = Dn / Ds, and 1 ≤ A ≤ 200. The range of the value of A may specifically be 1, 5, 10, 15, 20, 30, 40, 50, 80, 100, 120, 150, 180, or 200, etc. Of course, it may also be other values within the above range and is not limited herein.

[0021] In some embodiments, as shown in FIGS. 3a and 3b, the degree of crystallinity A of the silicon nano primary particles 11 is 1, and the silicon nano primary particles are single crystal silicon. The secondary particles 12 include a plurality of single crystal silicon primary particles 11a.

[0022] In some embodiments, the degree of crystallinity of the silicon nano primary particles is 1 < A ≤ 200, the silicon nano primary particles include silicon crystal grains, and the silicon crystal grains include polycrystalline silicon.

[0023] In some embodiments, as shown in FIG. 1, the negative electrode material includes secondary particles 12, the secondary particles 12 include silicon nano primary particles 11, the average particle size of the silicon nano primary particles 11 is Dn nm, the average particle size of the secondary particles 12 is Dm nm, the degree of deposition of the secondary particles 12 is B, B = Dm / Dn, and 5 ≤ B ≤ 400.

[0024] In the above solution, by considering the relationship between the size of the secondary particles and the size of the silicon nano-primary particles, it is possible to reduce the value of the deposition degree B and reduce the expansion rate of the anode material for the same silicon primary particle size. The compressive stress and tensile stress experienced by the secondary particles after lithiation are cumulative stresses. The lower the deposition degree, the fewer the primary particles and the lower the cumulative stress, resulting in a smaller expansion rate of the anode material. This is beneficial for forming a stable solid electrolyte film on the surface of the anode material, thereby improving the rate performance and cycle stability of the anode material.

[0025] In some embodiments, the average particle size of the secondary particles 12 is Dm nm, and 500≦Dm≦25000, and specifically may be 500 nm, 1000 nm, 1500 nm, 2000 nm, 3000 nm, 5000 nm, 8000 nm, 10000 nm, 15000 nm, 20000 nm, 23000 nm, or 25000 nm, etc., but is not limited thereto.

[0026] In some embodiments, the deposition degree of the secondary particles 12 is B, where B = Dm / Dn and 5≦B≦400. Specific values ​​for B may be 5, 10, 20, 50, 80, 100, 150, 200, 300, 350, or 400, and of course other values ​​within the above range are also possible and are not limited thereto. Controlling the deposition degree of the secondary particles 12 can ensure the structural stability of the secondary particles, which is beneficial for the formation of a stable SEI film, reduces the overall expansion coefficient of the anode material, and improves the initial efficiency and cycle performance of the anode material. If the deposition degree of the secondary particles 12 is too high, the specific surface area of ​​the secondary particles 12 will increase due to the small size of the silicon nanoparticles 11 for the same secondary particle size, which will increase the specific surface area of ​​the anode material. This will result in more side reactions during lithium release, consume more active lithium ions, and reduce the initial Coulombic efficiency of the anode material. If the deposition rate of the secondary particles 12 is too low, the size of the silicon nanoparticles will be large for the same secondary particle size, and the expansion stress of the secondary particles 12 will be more concentrated, which will easily cause the secondary particles to collapse and pulverize, which is detrimental to improving the structural stability of the negative electrode material and will reduce the cycle stability of batteries manufactured using the negative electrode material.

[0027] In some embodiments, the negative electrode material further includes a conductive layer 111 located on at least a portion of the surface of the silicon nanoparticles 11, the conductive layer 111 including at least one of an amorphous carbon material, a graphitized carbon material, and a conductive ceramic material. The conductive layer 111 has a porous structure, which is advantageous for the transport of lithium ions and electrons. Furthermore, by constructing the conductive layer 111 on the surface of the silicon nanoparticles, the conductive layer 111 can improve the conductivity of the silicon nanoparticles 11 and can also effectively mitigate the volume expansion of the silicon nanoparticles 11.

[0028] In some embodiments, the conductive layer 111 includes a graphitized carbon material, which is graphene, and the number of graphene layers is less than 20. The number of graphene layers may be, for example, 1, 2, 3, 5, 8, 10, 12, 15, 18, or 19 layers, and may of course be other values ​​within the above range, and is not limited thereto.

[0029] In some embodiments, the thickness of the conductive layer is 1 nm to 200 nm, and specifically may be 1 nm, 10 nm, 20 nm, 40 nm, 50 nm, 80 nm, 100 nm, 150 nm, 180 nm, or 200 nm, etc., but is not limited thereto.

[0030] In some embodiments, the conductive ceramic material comprises at least one of a metal oxide, a transition metal nitride, and a sulfide.

[0031] In some embodiments, the metal oxide comprises at least one of V2O5, TiO2, Nb2O5, CdO, CsO, MoO3, WO3, BaO, SnO2, Cr2O3, MnO, Ag2O, CoO, NiO, Cu2O, and SnO.

[0032] In some embodiments, the transition metal nitride comprises at least one of VN, TiN, CoN, Fe3N, Co4N, and WN.

[0033] In some embodiments, the sulfide comprises at least one of CdS, Ag2S, Sb2S3, TiS2, Li2S.

[0034] In some embodiments, the negative electrode material further includes a coating layer 121 located on the surface of at least a portion of the secondary particles 12, and the coating layer 121 includes at least one of an amorphous carbon material, a graphitized carbon material, and a polymer.

[0035] As can be seen, a coating layer is constructed on the surface of the secondary particles, and the coating layer can further mitigate the volume expansion of the negative electrode material. The conductive layer and the coating layer are used to synergistically modify the negative electrode material, and the conductivity of the conductive layer 111 is utilized to mitigate the volume expansion of the silicon nano primary particles, ensuring that the negative electrode material still has excellent electrical contact performance after absorbing lithium. Combined with the outermost coating layer 121, this can effectively avoid side reactions between the silicon nano primary particles and the electrolyte, and also improve the structural stability of the negative electrode material.

[0036] In some embodiments, the coating layer 121 includes a polymer, and illustratively the polymer may be at least one of a diblock copolymer, a triblock copolymer, and a multiblock copolymer.

[0037] In some embodiments, the mass content of the polymer in the negative electrode material is 1% to 20%, and specifically, may be 1%, 3%, 4%, 5%, 6%, 7%, 10%, 12%, 15%, 18%, or 20%, etc., but is not limited thereto. The thickness of the coating layer 121 is 5 nm to 300 nm, and specifically, may be 5 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, or 300 nm, etc., but is not limited thereto.

[0038] In some embodiments, the polymer comprises at least one of polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polydopamine, xanthan gum, polypyrrole, polythiophene, polyphenylacetylene, polyaniline, polyacetylene, and tannic acid. The polymer is preferably at least one of polypyrrole, polythiophene, polyaniline, polyaniline, and polyacetylene.

[0039] In some embodiments, the coating layer 121 includes a graphitized carbon material, and the thickness of the coating layer is 5 nm to 100 nm, and specifically may be 5 nm, 10 nm, 30 nm, 50 nm, 70 nm, 80 nm, 90 nm, or 100 nm, etc., but is not limited thereto.

[0040] In some embodiments, the coating layer 121 includes an amorphous carbon material, and the thickness of the coating layer is 10 nm to 500 nm, specifically, 10 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 450 nm, or 500 nm, etc., but is not limited thereto.

[0041] In some embodiments, the mass content of carbon element in the negative electrode material is 5% to 80%. Specifically, it may be 5%, 8%, 10%, 15%, 20%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, or 80%, but is not limited thereto. Note that the carbon in the negative electrode material is derived from a carbon material.

[0042] In some embodiments, the powder tap density of the negative electrode material is 0.3 g / cm 3 ~1.3g / cm 3 Specifically, 0.3 g / cm 3 , 0.5g / cm 3 , 0.6g / cm 3 , 0.7g / cm 3 , 0.8g / cm 3 , 1.0g / cm 3 , 1.3g / cm 3 etc. Preferably 0.5 g / cm 3 ~0.8g / cm 3 is.

[0043] In some embodiments, the powder pressed density of the negative electrode material is 1.2 g / cm 3 ~1.8g / cm 3 For example, 1.2 g / cm 3 , 1.3g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 or 1.8 g / cm 3 and the like, preferably 1.45 g / cm 3 ~1.75g / cm 3 is.

[0044] In some embodiments, the median diameter of the negative electrode material is 0.5 μm to 25 μm, and may optionally be, specifically, 0.5 μm, 1 μm, 3 μm, 4 μm, 5 μm, 7 μm, 10 μm, 13 μm, 15 μm, 20 μm, or 25 μm, etc., but is not limited thereto. The median diameter of the negative electrode material is preferably 0.5 μm to 10 μm, and more preferably 1 μm to 5 μm.

[0045] In some embodiments, the specific surface area ratio of the negative electrode material is 1 m 2 / g~50m 2 / g. Alternatively, the specific surface area ratio of the negative electrode material is 1 m 2 / g, 5m 2 / g, 8m 2 / g, 10m 2 / g, 15m 2 / g, 20m 2 / g, 25m 2 / g, 30m 2 / g, 35m 2 / g, 40m 2 / g, 45m 2 / g or 50m 2 / g, etc., and is not limited thereto. As can be understood, the smaller the specific surface area, the better. A specific surface area that is too large is likely to cause the formation of an SEI film, excessive consumption of irreversible lithium salt, and low initial efficiency that reduces the battery. Taking into consideration the cost of the manufacturing process, the specific surface area should be set to 2 m 2 / g~15m 2 Control to / g.

[0046] In some embodiments, the mass content of oxygen element in the negative electrode material is less than 15%, and specifically, it may be 5%, 6%, 8%, 10%, 12%, 13%, 14%, or 15%, etc., but is not limited thereto.

[0047] The present application further provides a method for manufacturing a negative electrode material, as shown in FIG. 4, the method comprising: Step S10: preparing silicon nano-primary particles, the silicon nano-primary particles including at least one silicon crystal grain, the silicon crystal grain having an average particle size Ds nm, 1≦Ds≦100, the silicon nano-primary particles having an average particle size Dn nm, 1≦Dn≦200, and the silicon nano-primary particles having a crystalline degree A, A=Dn / Ds, and 1≦A≦200; and step S20 of assembling the silicon nanoparticles into secondary particles to obtain a negative electrode material.

[0048] In this solution, by exploring the relationship between the size of the silicon nano primary particles and the size of the silicon crystal grains, and the equilibrium relationship between the sizes of the secondary particles and the silicon nano primary particles, it is possible to weaken the stress concentration that occurs during the lithiation process of the silicon nano primary particles, improve the structural stability of the silicon nano primary particles during the lithiation process, reduce the expansion rate of the negative electrode material, and be advantageous in forming a stable solid electrolyte film on the surface of the negative electrode material, so that the negative electrode material combines low expansion, high cycle stability, high rate performance, and high initial coulombic efficiency.

[0049] The method for producing the negative electrode material provided herein not only improves the electrochemical performance of the material, but is also suitable for large-scale production of the negative electrode material, and can effectively improve the rate performance and cycle stability of lithium batteries.

[0050] The manufacturing method of the present invention will be specifically described below with reference to examples. In step S10, silicon nano-primary particles are produced, and the silicon nano-primary particles include at least one silicon crystal grain, and the silicon crystal grain has an average grain size Ds nm, where 1≦Ds≦100, the silicon nano-primary particles have an average grain size Dn nm, where 1≦Dn≦200, and the crystallinity of the silicon nano-primary particles is A, where A=Dn / Ds, and 1≦A≦200.

[0051] In some embodiments, the average particle size of the silicon nanoparticles is Dn nm, where 1≦Dn≦200, and may be, for example, 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 190 nm, or 200 nm, but is not limited thereto.

[0052] In some embodiments, the average grain size of the silicon crystal grains is Ds nm, where 1≦Ds≦100, and may be, for example, 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm, but is not limited thereto.

[0053] In some embodiments, the degree of crystallinity of the silicon nanoparticles is A, where A=Dn / Ds and 1≦A≦200. The range of A may be, for example, 1, 5, 10, 15, 20, 30, 40, 50, 80, 100, 120, 150, 180, or 200, and may also be other values ​​within the above range, and is not limited thereto.

[0054] In some embodiments, the step of producing silicon nanoprimary particles includes vapor deposition using a silicon source gas to obtain silicon nanoprimary particles.

[0055] In some embodiments, the silicon source gas comprises at least one of silane, disilane, trichlorosilane, dichlorosilane, and silicon tetrachloride.

[0056] In some embodiments, the vacuum pressure before chemical vapor deposition may be less than 1.0 Torr, specifically, 0.9 Torr, 0.8 Torr, 0.7 Torr, 0.6 Torr, 0.5 Torr, 0.4 Torr, 0.3 Torr, or 0.1 Torr, etc., but is not limited thereto. As will be understood, before chemical vapor deposition, the pressure inside the furnace can be evacuated to a vacuum state, which is advantageous for improving the purity of the silicon nanoparticles. Subsequently, heating is performed, and an appropriate amount of silicon source gas is introduced as the growth material for the silicon nanoparticles, which are grown for a certain period of time to obtain the silicon nanoparticles.

[0057] In some embodiments, the heating rate during vapor phase growth is 1°C / min to 20°C / min, and specifically may be 1°C / min, 3°C / min, 5°C / min, 8°C / min, 10°C / min, 15°C / min, or 20°C / min, but is not limited thereto.

[0058] In some embodiments, the temperature during vapor phase growth is 300°C to 1000°C, and specifically may be 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, or 1000°C, etc., but is not limited thereto.

[0059] In some embodiments, the temperature of the vapor deposition is between 600°C and 1000°C, and may be specifically 400°C, 500°C, 600°C, 700°C, 800°C, or 1000°C.

[0060] In some embodiments, the flow rate of the silicon source gas is 0.05 L / min to 10 L / min, and specifically may be 0.05 L / min, 0.1 L / min, 0.5 L / min, 1 L / min, 2 L / min, 3 L / min, 5 L / min, 7 L / min, 8 L / min, or 10 L / min, but is not limited thereto.

[0061] In some embodiments, the flow time of the silicon source gas (i.e., the vapor deposition time) is 0.1 to 10 hours, and specifically may be 0.1, 0.5, 1, 2, 4, 6, 8, or 10 hours, but is not limited thereto.

[0062] In some embodiments, the pressure during vapor deposition is 100 Torr to 500 Torr, and specifically may be 100 Torr, 150 Torr, 200 Torr, 250 Torr, 300 Torr, 350 Torr, 400 Torr, 450 Torr, or 500 Torr, etc., but is not limited thereto.

[0063] In other embodiments, primary silicon nanoparticles can be produced using a plasma heating method, and the size ratio (degree of crystallinity A) between the primary silicon nanoparticles and silicon crystal grains may be controlled within the above range.

[0064] Furthermore, before step S20, the method further includes forming a conductive layer on the surface of the silicon nanoparticles, where the conductive layer includes at least one of an amorphous carbon material, a graphitized carbon material, and a conductive ceramic material.

[0065] In some embodiments, the step of forming a conductive layer on the surface of the silicon nanoparticles includes growing a first gaseous carbon source on the surface of the silicon nanoparticles by vapor deposition in a protective atmosphere to form a conductive layer.

[0066] In some embodiments, the concentration of the first gas-phase carbon source is 0.1 L / min to 10 L / min, and specifically may be 0.1 L / min, 1 L / min, 3 L / min, 5 L / min, 8 L / min, or 10 L / min, but is not limited thereto.

[0067] In some embodiments, the incubation time for vapor phase growth is 1 hour to 48 hours, and specifically may be 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, 12 hours, 18 hours, 24 hours, or 48 hours, but is not limited thereto.

[0068] In some embodiments, the temperature of the vapor deposition is 200°C to 1050°C, and specifically may be 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 950°C, or 1050°C, but is not limited thereto.

[0069] In some embodiments, the heating rate for vapor deposition is 1°C / min to 30°C / min, and specifically may be 1°C / min, 3°C / min, 5°C / min, 8°C / min, 10°C / min, 15°C / min, 20°C / min, 25°C / min, or 30°C / min, but is not limited thereto.

[0070] In some embodiments, the protective atmosphere comprises at least one of helium gas, neon gas, argon gas, krypton gas, and xenon gas.

[0071] In some embodiments, the volume ratio of the protective atmosphere to the first gas-phase carbon source is 10:(0.5 to 10), specifically, it may be 10:0.5, 10:1, 10:2, 10:3, 10:4, 10:5, 10:7, 10:8, 10:9, or 10:10, and is not limited thereto.

[0072] In some embodiments, the first vapor-phase carbon source comprises at least one of acetylene, methane, toluene, cyclohexane, ethanol, ethylene, and propylene.

[0073] In some embodiments, the step of forming a conductive layer on the surface of the silicon nanoparticles comprises flowing a conductive material at a predetermined pulse frequency and performing atomic layer deposition on the surface of the silicon nanoparticles to form the conductive layer. As can be seen, the atomic layer deposition technique is advantageous for growing and forming a conductive layer on the surface of the silicon nanoparticles to improve the conductivity of the silicon nanoparticles, and further improve the conductivity and rate performance of the negative electrode material.

[0074] Specifically, silicon nanoparticles are placed in an atomic layer deposition chamber, which is then evacuated and replaced with an inert gas. The chamber is then heated and held at a constant pulse frequency for a certain period of time, and one or more conductive materials are introduced as raw materials for the conductive layer. By controlling the amount of conductive material, one or more conductive layers are grown on the surface of the silicon nanoparticles.

[0075] In some embodiments, the temperature for atomic layer deposition is 200°C to 750°C, and may be, for example, 200°C, 300°C, 400°C, 450°C, 500°C, 550°C, 600°C, or 750°C, and may of course be other values ​​within the above range, and is not limited thereto.

[0076] In some embodiments, the time for atomic layer deposition is 1 hour to 48 hours, and specifically may be 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, 12 hours, 18 hours, 24 hours, or 48 hours, but is not limited thereto.

[0077] In some embodiments, the pulse frequency is 40 kHz to 500 kHz, and specifically may be 40 kHz, 60 kHz, 80 kHz, 100 kHz, 150 kHz, 200 kHz, 250 kHz, 300 kHz, 400 kHz, or 500 kHz, etc., but is not limited thereto.

[0078] In some embodiments, the pulse time of the conductive material is 10 ms to 800 ms, and may be, for example, 10 ms, 50 ms, 100 ms, 200 ms, 300 ms, 400 ms, 500 ms, 600 ms, 700 ms, or 800 ms, but is not limited thereto.

[0079] By controlling each parameter of atomic layer deposition, it is advantageous to form silicon nanoparticles in which the ratio of silicon nanoparticle size to silicon crystal grain size is within an appropriate range, and it is advantageous to alleviate the stress concentration problem of the silicon nanoparticles.

[0080] In some embodiments, the conductive layer comprises a conductive ceramic material, which comprises at least one of a metal oxide, a transition metal nitride, and a sulfide.

[0081] In some embodiments, the conductive material comprises an oxygen-containing organic compound of a transition metal, the oxygen-containing organic compound of the transition metal comprising at least one of titanium tetramethoxide, vanadium acetate, tetrabutyl titanate, and niobium oxalate. A metal oxide can be formed on the surface of the silicon nanoparticles by an atomic layer deposition process, the metal oxide comprising at least one of VO, TiO, NbO, CdO, CsO, MoO, WO, BaO, SnO, CrO, MnO, AgO, CoO, NiO, CuO, and SnO.

[0082] In some embodiments, the conductive material comprises a nitrogen-containing organic compound of a transition metal, the nitrogen-containing organic compound of the transition metal comprising at least one of ammonium metavanadate, ammonium titanate, ammonium cobaltate, ammonium iron trioxalate, tetraethylammonium tetrachlorocobaltate, and ammonium tungstate. Atomic layer deposition can be used to form a transition metal nitride on the surface of the silicon nanoparticles, the transition metal nitride comprising at least one of VN, TiN, CoN, FeN, CoN, and WN.

[0083] In some embodiments, the conductive material includes a transition metal organic compound and a sulfur-containing gas, the sulfur-containing gas including at least one of gaseous sulfur vapor, hydrogen sulfide, and sulfur dioxide. Sulfides can be formed on the surface of the silicon nanoparticles by an atomic layer deposition process, the sulfides including at least one of CdS, Ag2S, Sb2S3, TiS2, and Li2S.

[0084] In step S20, the silicon nano primary particles are assembled to form secondary particles to obtain a negative electrode material.

[0085] The silicon nano primary particles can be assembled to form secondary particles by methods such as self-assembly, melt assembly, electrostatic adsorption, or spray granulation coating, and the methods are not limited thereto.

[0086] In some embodiments, the step of assembling the silicon nano primary particles to form secondary particles comprises mixing a first solution containing the silicon nano primary particles and an anionic surfactant with a second solution containing the silicon nano primary particles and a cationic surfactant, and obtaining secondary particles after solid-liquid separation.

[0087] In some embodiments, the anionic surfactant comprises at least one of cetyltrimethylammonium bromide, sodium cetyl sulfate, polyvinylpyrrolidone, and sodium polystyrene sulfonate.

[0088] In some embodiments, the cationic surfactant comprises at least one of polydiallyldimethylammonium chloride, aminopropyltriethoxysilane, and a silane coupling agent.

[0089] In some embodiments, the mass ratio of the anionic surfactant to the silicon nanoparticles is (0.05 to 5):1, and specifically may be 0.05:1, 0.08:1, 1:1, 1.5:1, 2:1, 3:1, 4:1, or 5:1, etc., but is not limited thereto.

[0090] In some embodiments, the mass ratio of the cationic surfactant to the silicon nanoparticles is (0.05 to 10):1, and may be, for example, 0.05:1, 0.08:1, 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, 8:1, 9:1, or 10:1, but is not limited thereto.

[0091] In some embodiments, the first solution and / or the second solution includes a solvent, which may be a polar solvent, such as at least one of water, absolute ethanol, methanol, and isopropyl alcohol.

[0092] In some embodiments, the mass ratio of the silicon nanoparticles in the first solution to the silicon nanoparticles in the second solution is 1:(0.5 to 1.5), specifically, 1:0.5, 1:0.8, 1:0.9, 1:1, 1:1.2, 1:1.3, or 1:1.5, and is not limited thereto.

[0093] In some embodiments, the solid content of the first solution is 2% to 50%, and specifically may be 2%, 5%, 8%, 10%, 15%, 18%, 20%, 25%, 30%, 40%, 45%, 49%, or 50%, etc., but is not limited thereto. In some embodiments, the solids content in the second solution is 0.5% to 25%, and specifically may be 0.5%, 0.8%, 1%, 5%, 8%, 9%, 10%, 12%, 13%, 15%, 18%, 20%, 24%, or 25%, etc., but is not limited thereto.

[0094] In some embodiments, the solid content of the mixed slurry is 5% to 60%, and specifically may be 5%, 8%, 10%, 15%, 18%, 20%, 25%, 30%, 40%, 45%, 50%, 54%, 59%, or 60%, etc., but is not limited thereto.

[0095] In some embodiments, the step of assembling the silicon nano primary particles to form secondary particles includes spray granulating a mixed slurry containing the silicon nano primary particles and an anionic surfactant or a cationic surfactant to obtain secondary particles.

[0096] The types and contents of the cationic surfactant and anionic surfactant are as described above, and therefore, a detailed description thereof will be omitted here.

[0097] In some embodiments, the step of assembling the silicon nano primary particles to form secondary particles further includes subjecting the mixed slurry to a dispersion and centrifugation process, and the dispersion method includes at least one of mechanical stirring and ultrasonic dispersion.

[0098] In some embodiments, the mixed slurry further comprises a solvent, and the solvent is at least one selected from water, absolute ethanol, methanol, and isopropyl alcohol.

[0099] In some embodiments, the drying temperature for spray granulation is 100°C to 200°C, and specifically may be 100°C, 120°C, 130°C, 140°C, 150°C, 160°C, 180°C, or 200°C, but is not limited thereto.

[0100] In some embodiments, the supply rate for spray granulation is 100 mL / min to 1000 mL / min, and specifically may be 100 mL / min, 200 mL / min, 300 mL / min, 400 mL / min, 600 mL / min, 800 mL / min, or 1000 mL / min, etc., but is not limited thereto.

[0101] In some embodiments, the secondary particles comprise silicon nano primary particles, the silicon nano primary particles having an average particle size of Dn nm, the secondary particles having an average particle size of Dm nm, and the degree of deposition of the secondary particles is B, where B=Dm / Dn, and 5≦B≦400.

[0102] In the above solution, by considering the relationship between the size of the secondary particles and the size of the silicon nano-primary particles, it is possible to reduce the value of the deposition degree B and reduce the expansion rate of the anode material for the same silicon primary particle size. The compressive stress and tensile stress experienced by the secondary particles after lithiation are cumulative stresses. The lower the deposition degree, the fewer the primary particles and the lower the cumulative stress, resulting in a smaller expansion rate of the anode material. This is beneficial for forming a stable solid electrolyte film on the surface of the anode material, thereby improving the rate performance and initial coulombic efficiency of the anode material.

[0103] In some embodiments, the average particle size of the secondary particles is Dm nm, and 500≦Dm≦25000. Specifically, the average particle size may be 500 nm, 1000 nm, 1500 nm, 2000 nm, 3000 nm, 5000 nm, 8000 nm, 10000 nm, 15000 nm, 20000 nm, 23000 nm, or 25000 nm, etc., but is not limited thereto.

[0104] In some embodiments, the secondary particle deposition degree is B, where B = Dm / Dn and 5≦B≦400. Specific values ​​for B can be 5, 10, 20, 50, 80, 100, 150, 200, 300, 350, or 400, and of course other values ​​within the above range are also possible and are not limited thereto. Controlling the secondary particle deposition degree can ensure the structural stability of the secondary particles, which is beneficial for the formation of a stable SEI film, reducing the expansion rate of the anode material, and improving the initial efficiency and cycling performance of the anode material. If the secondary particle deposition degree is too high, the size of the silicon nanoparticles will be small for the same secondary particle size, resulting in an increased specific surface area of ​​the secondary particles and an increased specific surface area of ​​the anode material. This will increase side reactions during lithium release, consume more active lithium ions, and reduce the initial Coulombic efficiency of the anode material. If the deposition rate of secondary particles is too small, the size of the silicon nanoparticles will be large for the same secondary particle size, and the expansion stress of the secondary particles will be more concentrated, easily causing the secondary particles to collapse and pulverize, which is detrimental to improving the structural stability of the negative electrode material and reduces the cycle stability of batteries manufactured with the negative electrode material.

[0105] After step S20, the method further includes forming a coating layer on the surface of the secondary particles, the coating layer including at least one of an amorphous carbon material, a graphitized carbon material, and a polymer.

[0106] In some embodiments, the step of forming a coating layer on the surface of the secondary particles includes spray-drying a mixed coating liquid containing the secondary particles and a polymer, thereby forming a coating layer containing the polymer on the surface of the secondary particles.

[0107] In some embodiments, the solid content of the mixed coating solution of the secondary particles is 5% to 50%, and specifically may be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%, etc., and is not limited thereto.

[0108] In some embodiments, the coating mixture includes a polar solvent.

[0109] In some embodiments, the polar solvent comprises at least one of water, absolute ethanol, methanol, and isopropyl alcohol.

[0110] In some embodiments, the mass ratio of the secondary particles to the polymer is 10:(0.1 to 5), and specifically may be 10:0.1, 10:1, 10:2, 10:3, 10:4, or 10:5, and is not limited thereto.

[0111] In some embodiments, the drying temperature for spray drying is 60°C to 200°C, and specifically may be 60°C, 80°C, 100°C, 120°C, 150°C, 180°C, or 200°C.

[0112] In some embodiments, the polymer comprises at least one of a diblock copolymer, a triblock copolymer, and a multiblock copolymer.

[0113] In some embodiments, the polymer comprises at least one of polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polydopamine, xanthan gum, polypyrrole, polythiophene, polyphenylacetylene, polyaniline, polyacetylene, and tannic acid.

[0114] In some embodiments, the step of forming a coating layer on the surface of the secondary particles includes flowing a second gaseous carbon source through the secondary particles and heating the second gaseous carbon source until a pyrolysis reaction occurs, causing a coating layer including at least one of an amorphous carbon material and a graphitized carbon material to grow and form on the surface of the secondary particles.

[0115] In some embodiments, the second gas phase carbon source comprises at least one of acetylene, methane, toluene, cyclohexane, ethanol, ethylene, and propylene.

[0116] In some embodiments, the heating rate of the pyrolysis reaction is 1°C / min to 20°C / min, and may be, for example, 1°C / min, 3°C / min, 5°C / min, 8°C / min, 10°C / min, 15°C / min, or 20°C / min, but is not limited thereto.

[0117] In some embodiments, the temperature of the pyrolysis reaction is 600°C to 1000°C. Specifically, the reaction temperature may be 600°C, 650°C, 700°C, 750°C, 800°C, 890°C, 900°C, 960°C, or 1000°C. Through multiple experiments, the applicant has found that controlling the reaction temperature within the range of 600°C to 1000°C can improve the reaction efficiency and form a uniform carbon layer on the surface of the secondary particles, which may be amorphous carbon. Preferably, the reaction temperature is 700°C to 900°C.

[0118] In some embodiments, the incubation time for the thermal decomposition reaction is 1 hour to 48 hours, and specifically may be 1 hour, 4 hours, 8 hours, 12 hours, 16 hours, 24 hours, 28 hours, 32 hours, 38 hours, or 48 hours, but is not limited thereto.

[0119] In some embodiments, the concentration of the second gas-phase carbon source is 0.1 L / min to 10 L / min, and specifically may be 0.1 L / min, 0.4 L / min, 0.6 L / min, 0.8 L / min, 1.0 L / min, 2 L / min, 5 L / min, 6 L / min, 8 L / min, 9 L / min, or 10 L / min, etc., but is not limited thereto.

[0120] In some embodiments, the pyrolysis reaction is carried out in a protective atmosphere.

[0121] In some embodiments, the protective atmosphere comprises at least one of helium gas, neon gas, argon gas, krypton gas, and xenon gas.

[0122] The present application also provides a battery using the negative electrode material provided in the above examples of the present application or the negative electrode material manufactured by the method for manufacturing the negative electrode material provided in the above examples of the present application. The battery provided in the examples of the present application has the advantages of high capacity, high initial efficiency, long cycle life, excellent rate performance, and low expansion. The battery may be a lithium ion battery, a sodium ion battery, a solid electrolyte battery, etc., but is not limited thereto.

[0123] The present invention will be further described below in several examples. The present invention is not limited to the following specific examples. The present invention can be implemented with appropriate modifications within the scope of the independent claims.

[0124] Example 1 (1) After the chemical vapor deposition furnace was lowered to 0.5 Torr, it was heated to 600°C at a temperature increase rate of 3°C / min, and then silane gas was introduced at 0.5 L / min. The vapor deposition pressure of the entire growth furnace was controlled at 300 Torr. The growth retention time was 2 hours, and the primary silicon nanoparticles were collected after cooling. (2) The silicon nanoparticles were placed in a rotary atmosphere furnace and heated to 950°C at a heating rate of 3°C / min under the protection of an argon gas atmosphere. Then, acetylene gas was introduced at a rate of 0.5 L / min, and the volume ratio of argon gas to acetylene in the rotary atmosphere furnace was 9:1. The temperature was maintained for 4 hours, and then the material was cooled to obtain a precursor, which included silicon nanoparticles and a carbon layer located on their surface. (3) 10 g of the precursor and cetyltrimethylammonium bromide were dispersed in 200 ml of deionized water at a mass ratio of 10:2, stirred for 30 minutes, sonicated for 10 minutes, and centrifuged to dry. This resulted in modified precursor A1. 10 g of the precursor and 1 g of polydiallyldimethylammonium chloride were dissolved in 100 ml of deionized water, stirred for 30 minutes, sonicated for 20 minutes, and centrifuged to dry. This resulted in modified precursor B2. 10 g of modified precursor A1 was dissolved in 100 ml of deionized water and stirred for 10 minutes to obtain solution E. 10 g of modified precursor B2 was dispersed in 100 ml of deionized water and stirred for 10 minutes to obtain solution F. Solution E was slowly added dropwise to solution F, and the mixture was rapidly stirred for 40 minutes. The mixture was then centrifuged to dry. (4) 10 g of the composite was dissolved in 100 g of absolute ethanol, and 1 g of polyacrylic acid was added. The mixture was then mechanically stirred for 30 minutes, and the drying temperature was controlled to 100°C using a spray drying method to coat the surface of the composite with the polymer, thereby obtaining a negative electrode material. The negative electrode material produced by this embodiment includes secondary particles and a coating layer located on at least a portion of the surface of the secondary particles, the coating layer being a polymer layer, the secondary particles including silicon nano primary particles and a conductive layer located on at least a portion of the surface of the silicon nano primary particles, the conductive layer being an amorphous carbon layer, and the silicon nano primary particles including a plurality of silicon crystal grains.

[0125] FIG. 5 is a scanning electron microscope photograph of the negative electrode material prepared in Example 1, FIG. 6 is an XRD diagram of the negative electrode material prepared in Example 1, and FIG. 7 is a graph of the cycle characteristics of the negative electrode material prepared in Example 1, where the charge / discharge current is 1000 mA / g.

[0126] As can be seen from the scanning electron microscope photograph in FIG. 5, the surface of the produced negative electrode material has a spherical structure and is covered with one dense coating layer.

[0127] As can be seen from the XRD map in FIG. 6, the three intensity peaks at 28.4°, 47.3°, and 56.1° correspond to the three intensity peaks of silicon (JCPDS No. 27-1402). There is essentially no impurity phase. The size of the silicon crystal grains is calculated to be 5 nm based on the Scherrer equation.

[0128] As can be seen from FIG. 7, the material has excellent cycling performance, with a capacity of 1255 mAh / g up to 100 cycles at a current of 0.25 C, and a capacity retention of 75%. Table 1 shows the details of the parameters of the negative electrode material in this example.

[0129] Example 2 (1) After the chemical vapor deposition furnace was lowered to 0.5 Torr, it was heated to 700°C at a temperature increase rate of 3°C / min, and then silane gas was introduced at 1.5 L / min. The pressure of the entire furnace was controlled at 200 Torr. The growth retention time was 2 hours, and after cooling, primary silicon nanoparticles were collected. (2) The silicon nanoparticles were placed in a rotary atmosphere furnace and heated to 950°C at a heating rate of 3°C / min under the protection of an argon gas atmosphere. Then, acetylene gas was introduced at a rate of 1.5 L / min, and the volume ratio of argon gas to acetylene in the rotary atmosphere furnace was set to 9:1. The temperature was maintained for 3 hours, and then the material was cooled to obtain a precursor, which included silicon nanoparticles and a carbon layer located on their surface. (3) 10 g of the precursor was dissolved in 200 ml of absolute ethanol, 2 g of polyvinylpyrrolidone was added, and the mixture was stirred for 30 minutes and then ultrasonicated for 10 minutes to obtain a mixed slurry. The mixed slurry was then spheronized by spray granulation under drying conditions at 130°C to obtain Complex H. (4) 100 g of the composite was placed in a rotary atmosphere furnace and heated to 900°C at a temperature increase rate of 3°C / min under the protection of an argon gas atmosphere. After that, methane gas was flowed at 0.5 L / min to make the volume ratio of argon gas to acetylene in the rotary atmosphere furnace 9:1. After keeping the temperature for 6 hours, the acetylene gas was shut off and the material was cooled to obtain the negative electrode material. The negative electrode material manufactured according to this embodiment includes secondary particles and a coating layer located on at least a portion of the surface of the secondary particles, the coating layer being an amorphous carbon layer, the secondary particles including silicon nano primary particles and a conductive layer located on at least a portion of the surface of the silicon nano primary particles, the conductive layer being an amorphous carbon layer, and the silicon nano primary particles including a plurality of silicon crystal grains. Table 1 shows the details of the parameters of the negative electrode material in this example.

[0130] Example 3 (1) After the chemical vapor deposition furnace was lowered to 0.5 Torr, it was heated to 600°C at a temperature increase rate of 3°C / min, and then silane gas was introduced at 0.5 L / min, the pressure of the entire furnace was controlled at 300 Torr, and the holding time was 2 hours. After cooling, primary silicon nanoparticles were collected. (2) 100g of silicon nanoparticles were placed in the processing chamber of an atomic layer deposition device, evacuated to 0.5mbar, and then heated to 250°C. Subsequently, reactive gaseous titanium tetramethoxide was injected into the processing chamber as a conductive material at a frequency of 500Hz using a pulser. The pulse time was 200ms and the flow rate of the gaseous titanium tetramethoxide was 200sccm. Finally, the gaseous titanium tetramethoxide was closed and the remaining reactive gas in the chamber was replaced with argon gas. After cooling, a precursor was obtained, which included silicon nanoparticles and a titanium oxide layer on their surfaces. (3) 10 g of precursor was dissolved in 300 ml of absolute ethanol, 2 g of polyvinylpyrrolidone was added, and the mixture was stirred for 30 minutes and then ultrasonicated for 10 minutes to obtain a mixed slurry. The mixed slurry was then spheronized using a spray granulation method (feed rate: 500 mL / min) at 150°C under drying conditions to obtain a composite. (4) 100 g of the composite was placed in a rotary atmosphere furnace and heated to 950°C at a temperature increase rate of 5°C / min under the protection of an argon gas atmosphere. Then, acetylene gas was introduced at a rate of 2.5 L / min, and the volume ratio of argon gas to acetylene in the rotary atmosphere furnace was set to 8:2. After keeping the temperature for 6 hours, the acetylene gas was shut off and the composite was cooled to obtain the negative electrode material. The negative electrode material manufactured according to this embodiment includes secondary particles and a coating layer located on at least a portion of the surface of the secondary particles, the coating layer being an amorphous carbon layer, the secondary particles including silicon nano primary particles and a conductive layer located on at least a portion of the surface of the silicon nano primary particles, the conductive layer being a titanium oxide layer, and the silicon nano primary particles including a plurality of silicon crystal grains. Table 1 shows the details of the parameters of the negative electrode material in this example.

[0131] Example 4 (1) A silicon substrate plated with a thin layer of metallic copper was placed in the cavity of a chemical vapor deposition furnace, which was then pulled out to 0.5 Torr and heated to 1000°C at a heating rate of 20°C / min. Silane gas was then introduced at a rate of 0.5 L / min, and the pressure of the entire furnace was controlled at 100 Torr. The holding time was 2 hours. After cooling, primary silicon nanoparticles were collected. (2) 100g of silicon nanoparticles were placed in the processing chamber of an atomic layer deposition device, which was then evacuated to 0.5mbar and heated to 250°C. Subsequently, titanium tetramethoxide gas was injected into the processing chamber as a conductive material at a frequency of 500Hz using a pulser. The pulse time was 200ms and the flow rate of titanium tetramethoxide gas was 200sccm. Finally, the titanium tetramethoxide gas was closed and the remaining reaction gas in the chamber was replaced with argon gas. After cooling, a precursor was obtained, which contained silicon nanoparticles and a titanium oxide layer on their surface. (3) 10 g of the precursor was dissolved in 300 mL of absolute ethanol, 2 g of polyvinylpyrrolidone was added, and the mixture was stirred for 30 minutes and then ultrasonicated for 10 minutes to obtain a mixed slurry. The mixed slurry was then spheronized using a spray granulation method (feed rate 300 mL / min) at 150°C under drying conditions to obtain a composite. (4) 100 g of the composite was placed in a rotary atmosphere furnace and heated to 950°C at a temperature increase rate of 5°C / min under the protection of an argon gas atmosphere. Then, acetylene gas was introduced at a rate of 2.5 L / min, and the volume ratio of argon gas to acetylene in the rotary atmosphere furnace was set to 8:2. After keeping the temperature for 6 hours, the acetylene gas was shut off and the composite was cooled to obtain the negative electrode material. The negative electrode material manufactured in this embodiment includes secondary particles and a coating layer located on at least a portion of the surface of the secondary particles, the coating layer being an amorphous carbon layer, the secondary particles include silicon nanoparticles and a conductive layer located on at least a portion of the surface of the silicon nanoparticles, the conductive layer being a titanium oxide layer, and the silicon nanoparticles are single-crystalline silicon particles. Table 1 shows the details of the parameters of the negative electrode material in this example.

[0132] Example 5 (1) A silicon substrate plated with a thin layer of metallic copper was placed in the cavity of a chemical vapor deposition furnace, which was then pulled out to 0.5 Torr and heated to 1000°C at a heating rate of 20°C / min. Silane gas was then introduced at a rate of 0.5 L / min, and the pressure of the entire furnace was controlled at 100 Torr. The holding time was 2 hours. After cooling, primary silicon nanoparticles were collected. (2) 100 g of silicon nanoparticles were placed in a rotary atmosphere furnace and heated to 1050°C at a heating rate of 3°C / min under the protection of an argon gas atmosphere. Methane gas was then introduced at a rate of 0.5 L / min, and the volume ratio of argon gas to acetylene in the rotary atmosphere furnace was adjusted to 9:1. The temperature was maintained for 3 hours, and then the material was cooled to obtain a precursor. The precursor contained silicon nanoparticles and a graphitized carbon layer located on their surface. (3) 10 g of the precursor was dissolved in 300 ml of absolute ethanol, 2 g of polyvinylpyrrolidone was added, and the mixture was stirred for 30 minutes and then ultrasonicated for 10 minutes to obtain a mixed slurry. The mixed slurry was then spheronized using a spray granulation method (feed rate: 800 mL / min) at 150°C under drying conditions to obtain a composite. (4) 100 g of the composite was placed in a rotary atmosphere furnace and heated to 950°C at a temperature increase rate of 5°C / min under the protection of an argon gas atmosphere. Then, acetylene gas was introduced at a rate of 2.5 L / min, and the volume ratio of argon gas to acetylene in the rotary atmosphere furnace was set to 8:2. After keeping the temperature for 6 hours, the acetylene gas was shut off and the composite was cooled to obtain the negative electrode material. The negative electrode material manufactured according to this embodiment includes secondary particles and a coating layer located on at least a portion of the surface of the secondary particles, the coating layer being an amorphous carbon layer, the secondary particles include silicon nanoparticles and a conductive layer located on at least a portion of the surface of the silicon nanoparticles, the conductive layer being a graphitized carbon layer, and the silicon nanoparticles are single-crystalline silicon particles. Table 1 shows the details of the parameters of the negative electrode material in this example.

[0133] Example 6 The differences from the third embodiment are as follows. (2) 100g of silicon nanoparticles were placed in the processing chamber of an atomic layer deposition system, evacuated to 0.5mbar, and then heated to 250°C. Ammonium metavanadate was then injected into the processing chamber as a conductive material using a pulser at a frequency of 500kHz. The pulse time was 200ms and the flow rate of ammonium metavanadate was 200sccm. Finally, the ammonium metavanadate was closed and the remaining reaction gas in the chamber was replaced with argon gas. After cooling, a precursor was obtained, which contained silicon nanoparticles and a vanadium nitride (VN) layer on their surface. Table 1 shows the details of the parameters of the negative electrode material in this example.

[0134] Example 7 The differences from the third embodiment are as follows. (2) 100g of silicon nanoparticles were placed in the processing chamber of an atomic layer deposition system, evacuated to 0.5mbar, and then heated to 250°C. Subsequently, gaseous titanium tetramethoxide and gaseous sulfur vapor were injected into the processing chamber at a frequency of 500Hz using a pulser. The pulse time was 220ms, and the flow rates of the gaseous titanium tetramethoxide and gaseous sulfur vapor were 200sccm and 100sccm, respectively. Finally, the gaseous titanium tetramethoxide and gaseous sulfur vapor were closed, and the remaining reaction gas in the chamber was replaced with argon gas. After cooling, a precursor was obtained, which included silicon nanoparticles and a LiS layer located on their surface. Table 1 shows the details of the parameters of the negative electrode material in this example.

[0135] Example 8 The differences from the third embodiment are as follows. (2) The silicon nanoparticles are placed in a rotary atmosphere furnace and heated to 1050°C at a heating rate of 3°C / min under the protection of an argon gas atmosphere. Then, methane gas is introduced at a rate of 0.1 L / min, so that the volume ratio of argon gas to methane in the rotary atmosphere furnace is 9:1. The temperature is maintained for 2 hours, and then the precursor is cooled to obtain a precursor, which includes silicon nanoparticles and graphene carbon layers located on their surfaces, with the number of graphene layers being 5. Table 1 shows the details of the parameters of the negative electrode material in this example.

[0136] Example 9 The differences from the third embodiment are as follows. (4) 100 g of the composite was placed in a rotary atmosphere furnace and heated to 1050°C at a heating rate of 10°C / min under the protection of an argon gas atmosphere. Then, acetylene gas was introduced at a rate of 2.5 L / min, so that the volume ratio of argon gas to acetylene in the rotary atmosphere furnace was 8:2. After keeping the temperature for 6 hours, the acetylene gas was shut off and the composite was cooled to obtain a negative electrode material. The coating layer contained graphitized carbon and amorphous carbon. Table 1 shows the details of the parameters of the negative electrode material in this example.

[0137] Example 10 (1) After the chemical vapor deposition furnace was lowered to 0.5 Torr, it was heated to 600°C at a temperature increase rate of 3°C / min, and then silane gas was introduced at 0.5 L / min. The vapor deposition pressure of the entire growth furnace was controlled at 300 Torr. The growth retention time was 2 hours, and the primary silicon nanoparticles were collected after cooling. (2) 10 g of silicon nanoparticles and cetyltrimethylammonium bromide were dispersed in 200 ml of deionized water in a mass ratio of 10:2, stirred for 30 minutes, sonicated for 10 minutes, and centrifuged to dry. This resulted in modified silicon nanoparticles A1. 10 g of silicon nanoparticles and 1 g of polydiallyldimethylammonium chloride were dissolved in 100 ml of deionized water, stirred for 30 minutes, sonicated for 20 minutes, and centrifuged to dry. This resulted in modified silicon nanoparticles B2. 10 g of modified silicon nanoparticles A were dissolved in 100 ml of deionized water and stirred for 10 minutes to obtain solution E. 10 g of modified silicon nanoparticles B2 were dispersed in 100 ml of deionized water and stirred for 10 minutes to obtain solution F. Solution E was slowly added dropwise to solution F, and the mixture was rapidly stirred for 40 minutes. The mixture was then centrifuged to dry. The secondary particles were then used to obtain the anode material. The negative electrode material manufactured according to this embodiment includes secondary particles, and the secondary particles include silicon nano-primary particles, and the silicon nano-primary particles include a plurality of silicon crystal grains. Table 1 shows the details of the parameters of the negative electrode material in this example.

[0138] Example 11 The differences from the third embodiment are as follows. (1) After the chemical vapor deposition furnace was lowered to 0.5 Torr, it was heated to 500°C at a temperature increase rate of 3°C / min, and then silane gas was introduced at 0.5 L / min, the pressure of the entire furnace was controlled at 500 Torr, and the holding time was 2 hours. After cooling, primary silicon nanoparticles were collected. The negative electrode material manufactured according to this embodiment includes secondary particles and a coating layer located on at least a portion of the surface of the secondary particles, the coating layer being an amorphous carbon layer, the secondary particles including silicon nano primary particles and a conductive layer located on at least a portion of the surface of the silicon nano primary particles, the conductive layer being a titanium oxide layer, and the silicon nano primary particles including a plurality of silicon crystal grains. Table 1 shows the details of the parameters of the negative electrode material in this example.

[0139] Example 12 The differences from the third embodiment are as follows. (1) After the chemical vapor deposition furnace was lowered to 0.5 Torr, it was heated to 500°C at a temperature increase rate of 3°C / min, and then silane gas was introduced at 3.5 L / min. The pressure of the entire furnace was controlled at 100 Torr, and the holding time was 5 hours. After cooling, primary silicon nanoparticles were collected. The negative electrode material manufactured according to this embodiment includes secondary particles and a coating layer located on at least a portion of the surface of the secondary particles, the coating layer being an amorphous carbon layer, the secondary particles including silicon nano primary particles and a conductive layer located on at least a portion of the surface of the silicon nano primary particles, the conductive layer being a titanium oxide layer, and the silicon nano primary particles including a plurality of silicon crystal grains. Table 1 shows the details of the parameters of the negative electrode material in this example.

[0140] Example 13 (1) 100g of silica with an average particle size of 8um was mixed with 100g of magnesium powder uniformly, and then, through the magnesium thermal reduction silica process, it was placed in an atmospheric furnace filled with a protective atmosphere, heated to 650°C at a heating rate of 3°C / min, kept at that temperature for 3 hours, and then cooled to room temperature, obtaining micron silicon secondary particles composed of nano silicon. (2) The reaction product was dissolved in 1 mol / L dilute hydrochloric acid solution and stirred for 3 hours, then suction filtered and dried to obtain micron silicon secondary particles. (3) 100 g of pickled micron silicon secondary particles were placed in a rotary atmosphere furnace, and heated to 950°C at a heating rate of 5°C / min under the protection of an argon gas atmosphere. Then, acetylene gas was introduced at a rate of 2.5 L / min, and the volume ratio of argon gas to acetylene in the rotary atmosphere furnace was set to 8:2. After keeping the temperature for 6 hours, the acetylene gas was shut off and the material was cooled to obtain the negative electrode material. The negative electrode material manufactured in this example includes secondary particles and a coating layer located on at least a portion of the surface of the secondary particles, the coating layer being an amorphous carbon layer, and the secondary particles including silicon nanoparticles. Table 1 shows the details of the parameters of the negative electrode material in this example.

[0141] About performance tests 1) The specific surface area of ​​the negative electrode material was tested as follows: The equipment used was the TriStar3000&3020 fully automatic specific surface and pore size analyzer from Micromeritics Co., Ltd., USA, which implemented the national standard GB / T 19587-2017 to measure the amount of gas adsorbed on solid surfaces at different relative pressures at constant temperature and low temperature. After that, the amount of adsorption of the sample monolayer was calculated based on the Brunauer-Emmett-Teller adsorption theory and its formula (BET formula), and the specific surface area of ​​the material was then calculated.

[0142] 2) The test method for tap density is as follows: The tap density of the powder was tested using the DAT-6-220 powder tap density instrument from Quantachrome, USA. In accordance with the national standard GB / T 5162-2006 / ISO 3953:1993, a certain amount of sample was weighed and the tap density was tested by vibrating 300 times / min 3000 times.

[0143] 3) The test method for oxygen content and carbon content is as follows: The oxygen content was measured using a Nicolet Is10 Fourier infrared spectrometer from Thermo Fisher, USA, and the content of the carbon layer was tested by thermogravimetric analysis.

[0144] 4) Regarding SEM testing, Scanning electron microscopy was performed on a Hitachi S4800 field emission electron microscope from Japan, with an operating voltage of 200 kV to observe the structure of the negative electrode material and scale the thickness of the coating layer.

[0145] 5) The test method for the average size of primary particles and secondary particles is as follows: The average particle size was measured using an E3500 ion milling and S4800 field emission electron microscope from Hitachi, Japan.

[0146] 6) The test method for the average size of silicon crystal grains is as follows. The XRD spectrum of the sample was measured using a TD-3600 X-ray diffractometer from Dandong Tongda Co., Ltd., China, and the half-width and corresponding Bragg angle of the sample diffraction peak were obtained using Jade software, and the average crystal size of nanosilicon was calculated using the Scherrer formula D = Kγ / B cosθ.

[0147] 7) The test method for the thickness of the conductive layer and the coating layer is as follows: The materials were subjected to tangential surface processing using Hitachi E3500 ion milling and S4800 field emission electron microscope, both from Japan, and the layer thicknesses of the particle modification layer and the protective layer were measured by SEM.

[0148] 8) The particle size test method for the negative electrode material is as follows: D50 was measured using a laser granulometer, and it has a symmetric distribution similar to a normal distribution. In the volume-based distribution, the cumulative 50% diameter is D50, and by analogy, the cumulative 90% diameter is D90, and the cumulative 10% diameter is D10.

[0149] According to the above tests, the negative electrode materials prepared in Examples 1 to 13 correspond to sample numbers S1 to S13, and the performance parameters of the negative electrode materials are as shown in Table 1.

[0150] [Table 1]

[0151] 10) Regarding electrochemical testing, The negative electrode materials were sodium carboxymethylcellulose, styrene butadiene rubber, conductive graphite (KS-6), and carbon black (SP) in a 92:2:2:2:2 ratio, which was then uniformly coated on copper foil and dried to form a negative electrode sheet. This was then assembled into a button battery in an argon gas glove box. The separator used was a polypropylene microporous membrane, the electrolyte used was 1 mol / L lithium hexafluorophosphate (the solvent was a mixture of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate), and the counter electrode was a metallic lithium sheet.

[0152] A discharge specific capacity test was performed on the above 13 batteries using a Land CT2001A battery test system, and the ratio of the amount of electricity discharged in one hour to the battery capacity was taken as the discharge specific capacity.

[0153] The above 13 sets of batteries were subjected to an initial coulombic efficiency test using a Land CT2001A battery test system, and the charge / discharge current was 0.05C, and the initial coulombic efficiency was measured.

[0154] The 13 batteries were subjected to a 100-cycle test using a Land CT2001A battery test system, with a charge / discharge current of 0.2 C. After 100 cycles, the battery capacity after cycling and the capacity retention rate after cycling were calculated.

[0155] Among these, the capacity retention rate after 100 cycles at 0.2 C=discharge capacity at 100th cycle / discharge capacity at 1st cycle*100%. The results are shown in Table 2.

[0156] [Table 2]

[0157] As shown in Table 2, the anode materials prepared in Examples 1 to 9 can reduce stress concentration during the lithiation process of the nano-sized primary silicon particles by controlling the relationship between the size of the nano-sized primary silicon particles and the size of the silicon crystal grains, thereby improving the structural stability of the nano-sized primary silicon particles. Controlling the size relationship between the secondary particles and the nano-sized primary silicon particles can improve the structural stability of the anode material during the lithiation process, reduce the expansion rate of the material, and favor the formation of a stable solid electrolyte film on the surface of the anode material. By constructing a conductive layer on the surface of the nano-sized primary silicon particles and a coating layer on the surface of the secondary particles, the conductive layer and the coating layer synergistically modify the anode material. The conductive layer's conductivity and its ability to mitigate the volume expansion of the nano-sized primary silicon particles ensure that the anode material maintains excellent electrical contact performance after lithium absorption. Combined with the outermost coating layer, this effectively reduces side reactions between the nano-sized primary silicon particles and the electrolyte, reinforcing the structural stability of the anode material. Batteries prepared using these anode materials exhibit low expansion, high cycle stability, high rate capability, and initial coulombic efficiency.

[0158] In Example 10, there is no conductive layer on the surface of the primary particles of the negative electrode material, and there is no coating layer on the surface of the secondary particles. Therefore, the initial coulombic efficiency of the negative electrode material is roughly the same as that of Example 1. However, the cycle capacity retention rate and the capacity after 200 cycles are lower than those of Example 1. This is because the protection of the coating layer is insufficient, the side reaction between the electrolyte and the negative electrode material increases, the volume expansion of the negative electrode material becomes severe, and the electrochemical performance is significantly reduced.

[0159] During the manufacturing process of the anode material of Example 11, the deposition degree B of the secondary particles was too large and the size of the primary silicon nanoparticles was small, which caused an increase in the specific surface area of ​​the secondary particles and an increase in the specific surface area of ​​the anode material. As a result, during the lithium release process of the anode material, more side reactions occurred between the anode material and the electrolyte, and more active lithium ions were consumed, resulting in a decrease in the initial coulombic efficiency of the battery manufactured using the anode material.

[0160] In the manufacturing process of the negative electrode material of Example 12, the degree of crystallinity A of the silicon nano-primary particles was too large, and the size of the silicon crystal grains was too small, which made it easy for electrochemical sintering to occur on the surface of the silicon nano-primary particles, resulting in larger silicon crystal grains after sintering. After the negative electrode material intercalated lithium, the local stress of the silicon nano-primary particles increased, making the entire structure more unstable, resulting in a decrease in the cycle performance and capacity of the negative electrode material and a deterioration in the electrochemical performance of the negative electrode material.

[0161] During the manufacturing process of the negative electrode material of Example 13, the deposition degree B of the secondary particles is too small, the size of the primary silicon nanoparticles is large, and the expansion stress of the secondary particles is more concentrated, which is likely to cause the secondary particles to collapse and pulverize. This is unfavorable for improving the structural stability of the negative electrode material and reduces the cycle stability of the battery manufactured using the negative electrode material.

[0162] As claimed by the applicant, the present application describes the detailed process equipment and process flow of the present application through the above examples, but the present application is not limited to the above detailed process equipment and process flow, that is, it does not mean that the present application can be implemented without relying on the above detailed process equipment and process flow. It should be clear to those skilled in the art that any improvements to the present application, equivalent substitution of each raw material of the product of the present application, addition of auxiliary components, selection of specific methods, etc. are all within the protection scope and disclosure scope of the present application.

[0163] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to a Chinese patent application bearing application number 202311125354.4 and entitled "Negative electrode material and manufacturing method thereof, battery," filed with the State Intellectual Property Office of the People's Republic of China on August 31, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. secondary particles, the secondary particles including silicon nano primary particles; The silicon nano primary particles include at least one silicon crystal grain, the silicon crystal grain having an average grain size of Ds nm, and the silicon nano primary particles having an average grain size of Dn nm; The degree of crystallinity of the silicon nanoparticles is A, where A=Dn / Ds, and 1≦A≦200.

2. 2. The negative electrode material according to claim 1, wherein the degree of crystallinity of the silicon nanoparticles is A=1, and the silicon nanoparticles are single-crystal silicon.

3. The negative electrode material according to claim 1 , wherein the degree of crystallinity of the silicon nanoparticles is 1<A≦200, and the silicon nanoparticles include polycrystalline silicon.

4. (1) The average grain size of the silicon crystal grains is Ds nm, and 1≦Ds≦100; (2) The average particle size of the silicon nanoparticles is Dn nm, and 1≦Dn≦200. The negative electrode material according to claim 1 .

5. The negative electrode material according to any one of claims 1 to 4, wherein the average particle size of the secondary particles is Dm nm, the deposition degree of the secondary particles is B, B = Dm / Dn, and 5 ≦ B ≦ 400.

6. 6. The negative electrode material according to claim 5, wherein the average particle size of the secondary particles is Dm nm, and 500≦Dm≦25,000.

7. The negative electrode material according to claim 1 , further comprising a conductive layer located on at least a portion of the surface of the silicon nanoparticles.

8. The negative electrode material is (1) The conductive layer contains at least one of an amorphous carbon material, a graphitized carbon material, and a conductive ceramic material; (2) The conductive layer includes a graphitized carbon material, the graphitized carbon material is graphene, and the number of graphene layers is less than 20. (3) The conductive layer has a thickness of 1 nm to 200 nm. (4) The conductive layer includes a conductive ceramic material, and the conductive ceramic material includes at least one of a metal oxide, a transition metal nitride, and a sulfide. (5) The conductive layer includes a conductive ceramic material, the conductive ceramic material includes a metal oxide, and the metal oxide is V ２ O ５ , TiO ２ , Nb ２ O ５ , CdO, CsO, MoO ３ , W.O. ３ , BaO, SnO ２ , Cr ２ O ３ , MnO, Ag ２ O, CoO, NiO, Cu ２ the characteristic that it contains at least one of O and SnO; (6) The conductive layer includes a conductive ceramic material, and the conductive ceramic material includes a transition metal nitride, and the transition metal nitride is VN, TiN, CoN, Fe ３ N, Co ４ 8. The negative electrode material according to claim 7, wherein the negative electrode material satisfies at least one of the following characteristics:

9. The negative electrode material further includes a coating layer located on at least a portion of the surface of the secondary particles, the coating layer including at least one of an amorphous carbon material, a graphitized carbon material, and a polymer, and the negative electrode material includes: (1) The mass content of carbon element in the negative electrode material is 5% to 80%; (2) The coating layer includes a polymer, and the polymer includes at least one of polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polydopamine, xanthan gum, polypyrrole, polythiophene, polyphenylacetylene, polyaniline, polyacetylene, and tannic acid; (3) The coating layer includes a polymer, and the mass content of the polymer in the negative electrode material is 1% to 20%. (4) The coating layer contains a graphitized carbon material, and the thickness of the coating layer is 5 nm to 100 nm. (5) The coating layer contains an amorphous carbon material, and the thickness of the coating layer is 10 nm to 500 nm. (6) The negative electrode material according to claim 1, wherein the coating layer contains a polymer and has a thickness of 5 nm to 300 nm.

10. The powder tap density of the negative electrode material is 0.3 g / cm ３ ~1.3g / cm ３ 2. The negative electrode material according to claim 1, wherein

11. The powder compressed density of the negative electrode material is 1.2 g / cm ３ ~1.8g / cm ３ 2. The negative electrode material according to claim 1, wherein

12. 2. The negative electrode material according to claim 1, wherein the median diameter of the negative electrode material is 0.5 μm to 25 μm.

13. The specific surface area of ​​the negative electrode material is 1.0 m ２ / g to 50m ２ 2. The negative electrode material according to claim 1, wherein the Cr content is 1.0 / g.

14. 2. The negative electrode material according to claim 1, wherein the mass content of oxygen element in the negative electrode material is less than 15%.

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

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