Negative electrode material with high initial charge / discharge efficiency for lithium-ion secondary batteries and method for preparing same

Abstract

A negative electrode material for lithium ion secondary batteries with high initial charge / discharge efficiency and a method for preparing the same are provided. [Solution] The anode material with high initial charge-discharge efficiency comprises a porous carbon matrix, metallic lithium particles, nanosilicon particles, and a carbon shell, wherein the porous carbon matrix is ​​porous carbon microspheres with through-holes, the through-holes having an average pore size of 1 nm to 50 nm, the metallic lithium particles are formed in the through-holes by deposition of gaseous lithium, and the nanosilicon particles are formed in the through-holes by deposition of a silicon-containing gas, the mass of the metallic lithium particles accounting for 10% to 50% of the total mass of the anode material with high initial charge-discharge efficiency, the particle size of the nanosilicon particles being 0.1 nm to 45 nm, and the mass of the nanosilicon particles accounting for 20% to 70% of the total mass of the anode material with high initial charge-discharge efficiency, and when this anode material with high initial charge-discharge efficiency is used in a lithium-ion secondary battery, it can improve the coulombic efficiency of the battery on the first cycle, with the coulombic efficiency on the first cycle being 99% to 105%.

Description

[Technical Field]

[0001] (cross reference) This application claims priority to a Chinese patent application filed with the China Patent Office on December 19, 2022, bearing application number 202211633601.7 and entitled "Negative electrode material with high initial charge / discharge efficiency for lithium-ion secondary batteries and preparation method thereof."

[0002] (Technical field) The present invention relates to the technical field of lithium battery materials, and more particularly to a negative electrode material with high initial charge-discharge efficiency for lithium ion secondary batteries and a method for preparing the same. [Background technology]

[0003] Silicon has a theoretical specific capacity of 4200mAh / g, which allows it to store more lithium ions than graphite anodes, and its relatively high energy density effectively improves the driving time and range of batteries. With its advantages of high theoretical capacity, low lithium insertion and extraction potential, environmental friendliness, and abundant reserves, silicon is considered the most promising anode material for next-generation lithium batteries.

[0004] The alloying reaction between lithium ions and silicon causes a large volume expansion, generating large amounts of shear and compressive stress, which fractures the material particles and inhibits direct electron transfer to them. As the number of charge / discharge cycles increases, the impact of volume expansion increases, causing significant particle fracture and even pulverization, leading to some materials completely losing their electrochemical activity, resulting in a decrease in battery capacity and poor cycling performance. At the same time, during the initial charge process of a lithium-ion battery, a solid electrolyte interface (SEI) film forms on the surface of the anode, consuming some of the lithium ions, resulting in irreversible capacity and reduced Coulombic efficiency.

[0005] Although nanosizing silicon can solve the volume expansion problem to some extent, it remains difficult to uniformly disperse it in carbon materials. The decrease in coulomb efficiency due to lithium ion consumption can be improved by replenishment with lithium. Existing lithium replenishment methods generally include lithium foil replenishment, lithium powder replenishment, electrochemical lithium replenishment, and positive electrode lithium replenishment, but these methods are complicated and the effectiveness is unclear. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides an anode material for lithium-ion secondary batteries with high initial charge-discharge efficiency and a preparation method thereof. The material comprises gaseous lithium and silicon-containing gases deposited in the through-pores of porous carbon microspheres at intervals to form metallic lithium particles and nanosilicon particles. The resulting nano-sized silicon particles have a crystal grain size of less than 45 nm, effectively reducing the volume expansion effect. The alternate deposition of nanosilicon and metallic lithium ensures uniform distribution within the porous carbon microspheres, preventing nanosilicon aggregation. The co-deposition of metallic lithium and silicon in the porous carbon microspheres at intervals prevents the formation of lithium dendrites due to uneven lithium distribution, while fully utilizing the lithium replenishment effect, thereby improving the initial coulombic efficiency of the anode material.

[0007] The above method of lithium supplementation to negative electrode materials according to embodiments of the present invention is simple to operate, applicable to batch quantification production, distributes metallic lithium particles uniformly within the nanosilicon particles, and avoids the formation of lithium dendrites. [Means for solving the problem]

[0008] In a first aspect, an embodiment of the present invention provides a negative electrode material having high initial charge-discharge efficiency for a lithium-ion secondary battery, the negative electrode material having high initial charge-discharge efficiency comprising a porous carbon matrix, metallic lithium particles, nanosilicon particles, and a carbon shell; wherein the porous carbon matrix is ​​porous carbon microspheres having through-holes, the through-holes having an average pore size of 1 nm to 50 nm; the metallic lithium particles are formed in the through-holes by deposition of gaseous lithium, and the nanosilicon particles are formed in the through-holes by deposition of a silicon-containing gas; the mass of the metallic lithium particles accounts for 10% to 50% of the total mass of the high initial charge-discharge efficiency negative electrode material; The nanosilicon particles have a particle diameter of 0.1 nm to 45 nm, and the mass of the nanosilicon particles accounts for 20% to 70% of the total mass of the high initial charge-discharge efficiency negative electrode material; The negative electrode material with high initial charge / discharge efficiency has a coulombic efficiency of 99% to 105% in the first cycle in a lithium ion secondary battery.

[0009] Preferably, the mass of the carbon shell accounts for 1% to 20% of the total mass of the negative electrode material with high initial charge-discharge efficiency; The particle size of the negative electrode material with high initial charge-discharge efficiency is 1 μm to 100 μm.

[0010] In a second aspect, an embodiment of the present invention provides a method for preparing a negative electrode material having high initial charge-discharge efficiency for a lithium ion secondary battery according to the first aspect, the preparation method being a vapor deposition method, specifically comprising: Step S1: placing porous carbon microspheres having through-holes in a deposition chamber of a deposition device under an argon atmosphere; placing metallic lithium in a second furnace chamber of the deposition device and evaporating it at high temperature to form gaseous lithium; transporting the gaseous lithium from the second furnace chamber to the deposition chamber by a carrier gas; and depositing the gaseous lithium in the through-holes of the porous carbon microspheres to form metallic lithium particles. Step S2: introducing a silicon-containing gas into the deposition chamber and depositing it in the pores of the through-holes of the porous carbon microspheres to form nanosilicon particles; Step S3: alternately repeating Step S1 and Step S2, and introducing gaseous lithium and silicon-containing gases at intervals to uniformly deposit metallic lithium particles and nanosilicon particles in the through-holes of the porous carbon microspheres to obtain a precursor material. Step S4: applying a carbon coating to the precursor material by a gas phase method to form a dense carbon shell on the outer surface of the porous carbon microspheres, thereby obtaining a negative electrode material with high initial charge-discharge efficiency; Includes:

[0011] Preferably, the deposition apparatus comprises any of a vapor deposition furnace, a tubular furnace, a rotary furnace, a bell furnace, or a fluidized bed; wherein the deposition chamber and the second furnace chamber are connected via a first inlet, and the deposition amount of the gaseous lithium can be controlled by adjusting parameters of an automatic intake valve of the first inlet; a second intake port is provided outside the deposition chamber, and a deposition amount of the silicon-containing gas is controlled by adjusting parameters of an automatic intake valve of the second intake port; The temperature at which the lithium is evaporated to gaseous state at a high temperature is 800°C to 1500°C, and the temperature retention time is 1 hour to 20 hours. The carrier gas is argon gas, and the flow rate is 1 L / min to 50 L / min.

[0012] Preferably, the silicon-containing gas includes one or more silane gases selected from the group consisting of monosilane, disilane, trisilane, dichlorosilane, trichlorosilane, and tetrachlorosilane.

[0013] Preferably, the deposition temperature of the silicon-containing gas is 600° C. to 1500° C., the vapor phase growth time is 1 hour to 20 hours, and the gas flow rate is 0.5 L / min to 50 L / min.

[0014] Preferably, the method for applying carbon coating to the precursor material by a vapor phase method specifically includes depositing a carbon source gas at a temperature of 450°C to 1000°C on the outer surfaces of the porous carbon microspheres on which metallic lithium particles and nanosilicon particles are uniformly deposited in the through-pores to form a carbon shell; Here, the carbon source gas includes one or more of methane, ethane, propane, butane, acetylene, and propylene, the flow rate of the carbon source gas is 1 L / min to 50 L / min, and the deposition time is 1 hour to 15 hours.

[0015] Preferably, in steps 1 and 2, the precursor material is obtained by a thermal plasma method using industrial silicon powder and metallic lithium as raw materials in a thermal plasma treatment device, by depositing gaseous lithium and silicon vapor in the pores of the through-holes of the porous carbon microspheres.

[0016] In a third aspect, an embodiment of the present invention provides a negative electrode sheet comprising the negative electrode material with high initial charge-discharge efficiency described in the first aspect above.

[0017] In a fourth aspect, an embodiment of the present invention provides a lithium ion secondary battery comprising the negative electrode sheet according to the third aspect above. [Effects of the Invention]

[0018] The present invention provides an anode material for lithium-ion secondary batteries with high initial charge-discharge efficiency and a preparation method thereof. The material comprises gaseous lithium and silicon-containing gases deposited in the through-pores of porous carbon microspheres at intervals to form metallic lithium particles and nanosilicon particles. The resulting nano-sized silicon particles have a crystal grain size of less than 45 nm, effectively reducing the volume expansion effect. The alternate deposition of nanosilicon and metallic lithium ensures uniform distribution within the porous carbon microspheres, preventing nanosilicon aggregation. The co-deposition of metallic lithium and silicon in the porous carbon microspheres at intervals prevents the formation of lithium dendrites due to uneven lithium distribution, while fully utilizing the lithium replenishment effect, thereby improving the initial coulombic efficiency of the anode material.

[0019] The above method of lithium supplementation to negative electrode materials according to embodiments of the present invention is simple to operate, applicable to batch quantification production, distributes metallic lithium particles uniformly within the nanosilicon particles, and avoids the formation of lithium dendrites. [Brief explanation of the drawings]

[0020] The technical solutions of the embodiments of the present invention will be described in more detail below with reference to the drawings and examples.

[0021] [Figure 1] 1 is a flowchart of a method for preparing a negative electrode material with high initial charge-discharge efficiency by chemical vapor deposition according to an embodiment of the present invention. [Figure 2] 1 is a schematic structural diagram showing a cross section of a negative electrode material with high initial charge-discharge efficiency according to an embodiment of the present invention. [Figure 3] FIG. 2 is a charge / discharge curve diagram of a battery assembled using the negative electrode material with high initial charge / discharge efficiency prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, the present invention will be described in more detail with reference to the drawings and specific examples. However, it should be understood that these examples are merely for the purpose of explaining the present invention in more detail and are not intended to limit the present invention in any way, i.e., they are not intended to limit the protection scope of the present invention.

[0023] An embodiment of the present invention provides a negative electrode material with high initial charge-discharge efficiency for a lithium ion secondary battery, the negative electrode material with high initial charge-discharge efficiency comprising a porous carbon matrix, metallic lithium particles, nanosilicon particles, and a carbon shell, the particle size of the negative electrode material with high initial charge-discharge efficiency being 1 μm to 100 μm, and the negative electrode material with high initial charge-discharge efficiency has a first cycle Coulombic efficiency of 99% to 105% in a lithium ion secondary battery.

[0024] Here, the porous carbon matrix is ​​a porous carbon microsphere having through-holes, the through-holes having an average pore size of 1 nm to 50 nm, The metallic lithium particles are formed in the through-holes by deposition of gaseous lithium, and the particle diameter of the metallic lithium particles is 0.1 nm to 45 nm. The nanosilicon particles are formed in the through-holes by deposition of a silicon-containing gas, and the particle diameter of the nanosilicon particles is 0.1 nm to 45 nm.

[0025] The mass of the metallic lithium particles accounts for 10% to 50%, preferably 20% to 40%, of the total mass of the negative electrode material with high initial charge / discharge efficiency; the mass of the nanosilicon particles accounts for 20% to 70%, preferably 40 to 65%, of the total mass of the negative electrode material with high initial charge / discharge efficiency; and the mass of the carbon shell accounts for 1% to 20%, preferably 15 to 20%, of the total mass of the negative electrode material with high initial charge / discharge efficiency.

[0026] An embodiment of the present invention provides a method for preparing the above-mentioned negative electrode material with high initial charge-discharge efficiency, which is a vapor deposition method, and specifically includes the following steps, as shown in FIG.

[0027] In step S1, porous carbon microspheres having through-holes are placed in a deposition chamber of a deposition apparatus under an argon atmosphere, metallic lithium is placed in a second furnace chamber of the deposition apparatus and evaporated at high temperature to form gaseous lithium, and the gaseous lithium is transported from the second furnace chamber to the deposition chamber by a carrier gas, and the gaseous lithium is deposited in the pores of the through-holes of the porous carbon microspheres to form metallic lithium particles. Here, the deposition apparatus includes any of a vapor deposition furnace, a tube furnace, a rotary furnace, a bell furnace, or a fluidized bed. Here, the deposition chamber and the second furnace chamber are connected via a first inlet, and the deposition amount of gaseous lithium can be controlled by adjusting the parameters of the automatic intake valve of the first inlet. A second intake port is provided outside the deposition chamber, and the deposition amount of the silicon-containing gas is controlled by adjusting the parameters of an automatic intake valve of the second intake port. The temperature at which the lithium is evaporated to form gaseous lithium is 800°C to 1500°C, and the temperature retention time is 1 hour to 20 hours. The carrier gas is argon gas, and the flow rate is 1 L / min to 50 L / min.

[0028] In step S2, a silicon-containing gas is introduced into the deposition chamber and deposited in the pores of the through-holes of the porous carbon microspheres to form nanosilicon particles. Here, the silicon-containing gas includes one or more silane gases selected from the group consisting of monosilane, disilane, trisilane, dichlorosilane, trichlorosilane, and tetrachlorosilane.

[0029] The deposition temperature of the silicon-containing gas is 600° C. to 1200° C., the vapor phase growth time is 1 hour to 20 hours, and the gas flow rate is 0.5 L / min to 50 L / min.

[0030] In step S3, steps S1 and S2 are alternately repeated, and lithium- and silicon-containing gases are introduced at intervals to uniformly deposit metallic lithium particles and nanosilicon particles in the through-holes of the porous carbon microspheres, thereby obtaining a precursor material. Here, within the range of the deposition time, the time intervals at which the gaseous lithium and silicon-containing gas are introduced at intervals of 0.5 to 1 hour.

[0031] In step S4, the precursor material is coated with carbon by a vapor phase method to form a dense carbon shell on the outer surface of the porous carbon microspheres, thereby obtaining a negative electrode material with high initial charge-discharge efficiency. Specifically, the vapor-phase deposition method for carbon-coating a precursor material involves depositing a carbon source gas at a temperature of 450°C to 1000°C on the outer surface of porous carbon microspheres with lithium metal particles and nanosilicon particles uniformly deposited in the through-pores to form a carbon shell. The carbon source gas includes one or more of methane, ethane, propane, butane, acetylene, and propylene. The flow rate of the carbon source gas is 1 L / min to 50 L / min, and the deposition time is 1 hour to 15 hours.

[0032] In the present application, in step S2, the deposition temperature of the silicon-containing gas is 600°C to 1500°C, preferably 600°C to 1200°C, such as 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, or any temperature within the range. If the temperature is below 600°C, the silicon-containing gas material will not be completely decomposed. If the temperature is above 1200°C, the nano-silicon produced by the decomposition and reduction of the silicon-containing gas material will be severely crystallized, resulting in large silicon crystal grains, which will affect the cycling performance of the material. Furthermore, silicon and carbon will react at high temperatures to produce silicon carbide, which will affect the conductive properties of the material.

[0033] In the present application, in step S3 of the preparation method, steps S1 and S2 are alternately repeated, and the order can be any, such as performing step S2 first and then S1, as long as the lithium metal particles and nanosilicon particles can be uniformly deposited in the through-holes of the porous carbon microspheres at a certain time interval, thereby improving the Coulomb efficiency of the first cycle and avoiding the formation of lithium dendrites.

[0034] Alternatively, in steps 1 and 2 of the preparation method, a precursor material can be obtained by using industrial silicon powder and metallic lithium as raw materials in a thermal plasma treatment device, and depositing gaseous lithium and silicon vapor into the pores of the through-holes of the porous carbon microspheres in a thermal plasma treatment device.

[0035] The schematic structure of the negative electrode material for lithium-ion secondary batteries with high initial charge-discharge efficiency prepared by the above-mentioned preparation method is shown in Figure 2. It shows that metallic lithium particles and nanosilicon particles are deposited over time in the through-pores of the porous carbon microspheres.

[0036] The negative electrode material having high initial charge-discharge efficiency according to the embodiment of the present invention can be used as a negative electrode active material in a lithium battery negative electrode material and can be used to prepare a negative electrode sheet for a lithium-ion secondary battery. The negative electrode sheet of the present application further includes a negative electrode current collector. The present application does not particularly limit the negative electrode current collector as long as it can achieve the objectives of the present application, and examples thereof include, but are not limited to, copper foil, copper alloy foil, nickel foil, stainless steel foil, nickel foam, copper foam, or a composite current collector. A lithium ion secondary battery using the negative electrode material with high initial charge / discharge efficiency according to the embodiment of the present invention as the negative electrode active material has a high coulombic efficiency in the first cycle.

[0037] In order to better understand the technical solution of the present invention, several specific examples will be given below to respectively illustrate the preparation process of the negative electrode material with high initial charge-discharge efficiency for lithium ion secondary batteries of the present invention, as well as the application method and properties of the same in lithium batteries.

[0038] Example 1 This example provides a preparation process and characteristic test of a negative electrode material with high initial charge-discharge efficiency for a lithium ion secondary battery, and the specific steps are as follows:

[0039] In step S1, porous carbon microspheres having through-holes are placed in a deposition chamber of a deposition apparatus under an argon atmosphere. Metallic lithium is placed in a second furnace chamber of the deposition apparatus and evaporated at a high temperature of 800°C to form gaseous lithium. The gaseous lithium is transported from the second furnace chamber to the deposition chamber by argon gas, a carrier gas, at a flow rate of 0.5 L / min. The gaseous lithium is deposited in the pores of the porous carbon microspheres to form metallic lithium particles. The deposition time is 20 hours.

[0040] In step S2, monosilane is introduced into the deposition chamber at a flow rate of 0.5 L / min and a temperature of 600° C. to deposit it in the pores of the through-holes of the porous carbon microspheres to form nanosilicon particles, and the deposition time is 20 hours.

[0041] In step S3, steps S1 and S2 are alternately repeated, introducing gaseous lithium and silicon-containing gases at 0.5-hour intervals, respectively, to uniformly deposit metallic lithium particles and nanosilicon particles in the through-holes of the porous carbon microspheres, thereby obtaining the precursor material.

[0042] In step S4, the precursor material is subjected to a carbon coating process using a gas-phase method, in which deposition is performed at 450°C for 15 hours using methane at a flow rate of 1 L / min, to form a dense carbon shell on the outer surface of the porous carbon microspheres, thereby obtaining a negative electrode material with high initial charge-discharge efficiency.

[0043] A negative electrode sheet was produced using the negative electrode material with high initial charge-discharge efficiency prepared in this example, and a battery was assembled and tested. The results were as follows:

[0044] To prepare the negative electrode sheet, the obtained high initial charge / discharge efficiency negative electrode material, carbon black as a conductive additive, and adhesive (1:1 sodium cellulose and styrene butadiene rubber) were weighed in a mass ratio of 95:2:3, and a slurry was prepared in a beater at room temperature. The prepared slurry was uniformly applied to copper foil and dried in a fan dryer at 50°C for 2 hours. After that, the foil was cut into 8 x 8 mm pole pieces and dried in a vacuum dryer at 100°C for 10 hours under vacuum. The dried pole pieces were immediately transferred into a glove box for battery assembly.

[0045] The battery was assembled in a glove box containing a high-purity Ar atmosphere. Metallic lithium was used as the counter electrode, and a solution of ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio v:v = 1:1) containing 1 mol / L of LiPF6 was used as the electrolyte.

[0046] The test was conducted in a constant current charge / discharge mode using a charger / discharger, with the discharge end voltage being 0.005 V and the charge end voltage being 1.5 V. The charge / discharge test was conducted at a current density of C / 10, and the charge / discharge curves are shown in Figure 3. The test data are shown in Table 1.

[0047] Example 2 This example provides a preparation process and characteristic test of a negative electrode material with high initial charge-discharge efficiency for a lithium ion secondary battery, and the specific steps are as follows:

[0048] In step S1, porous carbon microspheres having through-holes are placed in a deposition chamber of a deposition apparatus under an argon atmosphere. Metallic lithium is placed in a second furnace chamber of the deposition apparatus and evaporated at a high temperature of 900°C to form gaseous lithium. The gaseous lithium is then transported from the second furnace chamber to the deposition chamber by argon gas, a carrier gas, at a flow rate of 5 L / min. The gaseous lithium is then deposited in the pores of the porous carbon microspheres to form metallic lithium particles. The deposition time is 18 hours.

[0049] In step S2, trisilane gas is introduced into the deposition chamber at a flow rate of 5 L / min and a temperature of 650° C. to deposit it in the pores of the porous carbon microspheres to form nanosilicon particles, and the deposition time is 18 hours.

[0050] In step S3, steps S1 and S2 are alternately repeated, introducing gaseous lithium and silicon-containing gases at intervals of 1 hour, respectively, to uniformly deposit metallic lithium particles and nanosilicon particles in the through-holes of the porous carbon microspheres, thereby obtaining the precursor material.

[0051] In step S4, the precursor material is subjected to a carbon coating process using a vapor deposition method, in which carbon is deposited at 500°C for 14 hours using ethane at a flow rate of 5 L / min to form a dense carbon shell on the outer surface of the porous carbon microspheres, thereby obtaining a negative electrode material with high initial charge-discharge efficiency.

[0052] The negative electrode material with high initial charge-discharge efficiency prepared in this example was used to prepare a negative electrode sheet, and a battery was assembled and tested. The specific process was the same as in Example 1, and the test results are shown in Table 1.

[0053] Example 3 This example provides a preparation process and characteristic test of a negative electrode material with high initial charge-discharge efficiency for a lithium ion secondary battery, and the specific steps are as follows:

[0054] In step S1, porous carbon microspheres having through-holes are placed in a deposition chamber of a deposition apparatus under an argon atmosphere. Metallic lithium is placed in a second furnace chamber of the deposition apparatus and evaporated at a high temperature of 1000°C to form gaseous lithium. The gaseous lithium is then transported from the second furnace chamber to the deposition chamber by argon gas, a carrier gas, at a flow rate of 10 L / min. The gaseous lithium is then deposited in the pores of the porous carbon microspheres to form metallic lithium particles. The deposition time is 16 hours.

[0055] In step S2, dichlorosilane is introduced into the deposition chamber at a flow rate of 10 L / min and a temperature of 700° C. to deposit it in the pores of the through-holes of the porous carbon microspheres to form nanosilicon particles, and the deposition time is 16 hours.

[0056] In step S3, steps S1 and S2 are alternately repeated, introducing gaseous lithium and silicon-containing gases at 0.5-hour intervals, respectively, to uniformly deposit metallic lithium particles and nanosilicon particles in the through-holes of the porous carbon microspheres, thereby obtaining the precursor material.

[0057] In step S4, the precursor material is subjected to a carbon coating process using a vapor deposition method. The carbon is deposited at 550°C for 12 hours using propane at a flow rate of 10 L / min. This forms a dense carbon shell on the outer surface of the porous carbon microspheres, resulting in a negative electrode material with high initial charge-discharge efficiency.

[0058] The negative electrode material with high initial charge-discharge efficiency prepared in this example was used to prepare a negative electrode sheet, and a battery was assembled and tested. The specific process was the same as in Example 1, and the test results are shown in Table 1.

[0059] Example 4 This example provides a preparation process and characteristic test of a negative electrode material with high initial charge-discharge efficiency for a lithium ion secondary battery, and the specific steps are as follows:

[0060] In step S1, porous carbon microspheres having through-holes are placed in a deposition chamber of a deposition apparatus under an argon atmosphere. Metallic lithium is placed in a second furnace chamber of the deposition apparatus and evaporated at a high temperature of 1100°C to form gaseous lithium. The gaseous lithium is then transported from the second furnace chamber to the deposition chamber by argon gas, a carrier gas, at a flow rate of 15 L / min. The gaseous lithium is then deposited in the pores of the porous carbon microspheres to form metallic lithium particles. The deposition time is 14 hours.

[0061] In step S2, trichlorosilane gas is introduced into the deposition chamber at a flow rate of 15 L / min and a temperature of 750° C. to deposit it in the pores of the porous carbon microspheres to form nanosilicon particles, and the deposition time is 14 hours.

[0062] In step S3, steps S1 and S2 are alternately repeated, introducing gaseous lithium and silicon-containing gases at intervals of 1 hour, respectively, to uniformly deposit metallic lithium particles and nanosilicon particles in the through-holes of the porous carbon microspheres, thereby obtaining the precursor material.

[0063] In step S4, the precursor material is subjected to a carbon coating process using a vapor deposition method. The carbon is deposited at 600°C for 10 hours using butane at a flow rate of 15 L / min to form a dense carbon shell on the outer surface of the porous carbon microspheres, thereby obtaining a negative electrode material with high initial charge-discharge efficiency.

[0064] The negative electrode material with high initial charge-discharge efficiency prepared in this example was used to prepare a negative electrode sheet, and a battery was assembled and tested. The specific process was the same as in Example 1, and the test results are shown in Table 1.

[0065] Example 5 This example provides a preparation process and characteristic test of a negative electrode material with high initial charge-discharge efficiency for a lithium ion secondary battery, and the specific steps are as follows:

[0066] In step S1, porous carbon microspheres having through-holes are placed in a deposition chamber of a deposition apparatus under an argon atmosphere. Metallic lithium is placed in a second furnace chamber of the deposition apparatus and evaporated at a high temperature of 1200°C to form gaseous lithium. The gaseous lithium is then transported from the second furnace chamber to the deposition chamber by argon gas, a carrier gas, at a flow rate of 20 L / min. The gaseous lithium is then deposited in the pores of the porous carbon microspheres to form metallic lithium particles. The deposition time is 12 hours.

[0067] In step S2, monosilane is introduced into the deposition chamber at a flow rate of 20 L / min and a temperature of 800° C. to deposit in the pores of the porous carbon microspheres to form nanosilicon particles, and the deposition time is 12 hours.

[0068] In step S3, steps S1 and S2 are alternately repeated, introducing gaseous lithium and silicon-containing gases at intervals of 1 hour, respectively, to uniformly deposit metallic lithium particles and nanosilicon particles in the through-holes of the porous carbon microspheres, thereby obtaining the precursor material.

[0069] In step S4, the precursor material is subjected to a carbon coating process using a vapor phase method, in which deposition is performed at 650°C for 15 hours using acetylene at a flow rate of 20 L / min, to form a dense carbon shell on the outer surface of the porous carbon microspheres, thereby obtaining an anode material with high initial charge / discharge efficiency.

[0070] The negative electrode material with high initial charge-discharge efficiency prepared in this example was used to prepare a negative electrode sheet, and a battery was assembled and tested. The specific process was the same as in Example 1, and the test results are shown in Table 1.

[0071] Example 6 This example provides a preparation process and characteristic test of a negative electrode material with high initial charge-discharge efficiency for a lithium ion secondary battery, and the specific steps are as follows:

[0072] In step S1, porous carbon microspheres having through-holes are placed in a deposition chamber of a deposition apparatus under an argon atmosphere. Metallic lithium is placed in a second furnace chamber of the deposition apparatus and evaporated at a high temperature of 1300°C to form gaseous lithium. The gaseous lithium is transported from the second furnace chamber to the deposition chamber by argon gas, a carrier gas, at a flow rate of 25 L / min. The gaseous lithium is deposited in the pores of the porous carbon microspheres to form metallic lithium particles. The deposition time is 10 hours.

[0073] In step S2, monosilane is introduced into the deposition chamber at a flow rate of 25 L / min and a temperature of 900° C. to deposit it in the pores of the porous carbon microspheres to form nanosilicon particles, and the deposition time is 10 hours.

[0074] In step S3, steps S1 and S2 are alternately repeated, introducing gaseous lithium and silicon-containing gases at 0.5-hour intervals, respectively, to uniformly deposit metallic lithium particles and nanosilicon particles in the through-holes of the porous carbon microspheres, thereby obtaining the precursor material.

[0075] In step S4, the precursor material is subjected to a carbon coating process using a gas-phase method, in which deposition is performed at 700°C for 6 hours using propylene at a flow rate of 25 L / min, to form a dense carbon shell on the outer surface of the porous carbon microspheres, thereby obtaining a negative electrode material with high initial charge-discharge efficiency.

[0076] The negative electrode material with high initial charge-discharge efficiency prepared in this example was used to prepare a negative electrode sheet, and a battery was assembled and tested. The specific process was the same as in Example 1, and the test results are shown in Table 1.

[0077] Example 7 This example provides a preparation process and characteristic test of a negative electrode material with high initial charge-discharge efficiency for a lithium ion secondary battery, and the specific steps are as follows:

[0078] In step S1, porous carbon microspheres having through-holes are placed in a deposition chamber of a deposition apparatus under an argon atmosphere. Metallic lithium is placed in a second furnace chamber of the deposition apparatus and evaporated at a high temperature of 1400°C to form gaseous lithium. The gaseous lithium is then transported from the second furnace chamber to the deposition chamber by argon gas, a carrier gas, at a flow rate of 30 L / min. The gaseous lithium is then deposited in the pores of the porous carbon microspheres to form metallic lithium particles. The deposition time is 5 hours.

[0079] In step S2, monosilane is introduced into the deposition chamber at a flow rate of 30 L / min and a temperature of 1000° C. to deposit it in the pores of the porous carbon microspheres to form nanosilicon particles, and the deposition time is 5 hours.

[0080] In step S3, steps S1 and S2 are alternately repeated, introducing gaseous lithium and silicon-containing gases at intervals of 1 hour, respectively, to uniformly deposit metallic lithium particles and nanosilicon particles in the through-holes of the porous carbon microspheres, thereby obtaining the precursor material.

[0081] In step S4, the precursor material is subjected to a carbon coating process using a gas-phase method, in which a mixture of methane and ethane (volume ratio 1:1) is deposited at 800°C for 4 hours at a flow rate of 15 L / min to form a dense carbon shell on the outer surface of the porous carbon microspheres, thereby obtaining a negative electrode material with high initial charge-discharge efficiency.

[0082] The negative electrode material with high initial charge-discharge efficiency prepared in this example was used to prepare a negative electrode sheet, and a battery was assembled and tested. The specific process was the same as in Example 1, and the test results are shown in Table 1.

[0083] Example 8 This example provides a preparation process and characteristic test of a negative electrode material with high initial charge-discharge efficiency for a lithium ion secondary battery, and the specific steps are as follows:

[0084] In step S1, porous carbon microspheres having through-holes are placed in a deposition chamber of a deposition apparatus under an argon atmosphere. Metallic lithium is placed in a second furnace chamber of the deposition apparatus and evaporated at a high temperature of 1450°C to form gaseous lithium. The gaseous lithium is then transported from the second furnace chamber to the deposition chamber by argon gas, a carrier gas, at a flow rate of 40 L / min. The gaseous lithium is then deposited in the pores of the porous carbon microspheres to form metallic lithium particles. The deposition time is 3 hours.

[0085] In step S2, monosilane is introduced into the deposition chamber at a flow rate of 40 L / min and a temperature of 1100° C. to deposit it in the pores of the through-holes of the porous carbon microspheres to form nanosilicon particles, and the deposition time is 3 hours.

[0086] In step S3, steps S1 and S2 are alternately repeated, introducing gaseous lithium and silicon-containing gases at intervals of 1 hour, respectively, to uniformly deposit metallic lithium particles and nanosilicon particles in the through-holes of the porous carbon microspheres, thereby obtaining the precursor material.

[0087] In step S4, the precursor material is subjected to a carbon coating process using a vapor deposition method, in which methane is deposited at a flow rate of 20 L / min at 900°C for 2 hours to form a dense carbon shell on the outer surface of the porous carbon microspheres, thereby obtaining a negative electrode material with high initial charge-discharge efficiency.

[0088] The negative electrode material with high initial charge-discharge efficiency prepared in this example was used to prepare a negative electrode sheet, and a battery was assembled and tested. The specific process was the same as in Example 1, and the test results are shown in Table 1.

[0089] Example 9 This example provides a preparation process and characteristic test of a negative electrode material with high initial charge-discharge efficiency for a lithium ion secondary battery, and the specific steps are as follows:

[0090] In step S1, porous carbon microspheres having through-holes are placed in a deposition chamber of a deposition apparatus under an argon atmosphere. Metallic lithium is placed in a second furnace chamber of the deposition apparatus and evaporated at a high temperature of 1500°C to form gaseous lithium. The gaseous lithium is transported from the second furnace chamber to the deposition chamber by argon gas, a carrier gas, at a flow rate of 50 L / min. The gaseous lithium is deposited in the pores of the porous carbon microspheres to form metallic lithium particles. The deposition time is 1 hour.

[0091] In step S2, monosilane is introduced into the deposition chamber at a flow rate of 50 L / min and a temperature of 1200° C. to deposit in the pores of the porous carbon microspheres to form nanosilicon particles, and the deposition time is 1 hour.

[0092] In step S3, steps S1 and S2 are alternately repeated, introducing gaseous lithium and silicon-containing gases at 0.5-hour intervals, respectively, to uniformly deposit metallic lithium particles and nanosilicon particles in the through-holes of the porous carbon microspheres, thereby obtaining the precursor material.

[0093] In step S4, the precursor material is subjected to a carbon coating process using a gas-phase method, in which deposition is performed at 1000°C for 1 hour using methane at a flow rate of 12.5 L / min, to form a dense carbon shell on the outer surface of the porous carbon microspheres, thereby obtaining a negative electrode material with high initial charge-discharge efficiency.

[0094] The negative electrode material with high initial charge-discharge efficiency prepared in this example was used to prepare a negative electrode sheet, and a battery was assembled and tested. The specific process was the same as in Example 1, and the test results are shown in Table 1.

[0095] Example 10 This example provides a preparation process and characteristic test of a negative electrode material with high initial charge-discharge efficiency for lithium ion secondary batteries, using a thermal plasma method. The specific process is as follows:

[0096] 400 g of industrial silicon powder was used as the silicon source, 300 g of metallic lithium sheet was used as the lithium source, and the industrial silicon powder and lithium sheet were each placed in the high-temperature region of a plasma treatment device. 1 kg of porous carbon microspheres with through-holes was placed in the condensation region of the plasma treatment device. Under an argon atmosphere, the industrial silicon powder and metallic lithium sheet were each vaporized through the plasma treatment device and dissociated into a silicon-containing gas and gaseous lithium. The silicon-containing gas and gaseous lithium were then transported alternately to the condensation region 10 times using argon gas as a carrier gas. The metallic lithium particles and nanosilicon particles were uniformly deposited in the through-holes of the porous carbon microspheres to obtain a precursor material. Methane, the carbon source, was then introduced at a flow rate of 12 L / min, and the deposition was carried out at 1000°C for 1 hour. The precursor material was then carbon-coated to obtain an anode material with high initial charge-discharge efficiency.

[0097] The negative electrode material with high initial charge-discharge efficiency prepared in this example was used to prepare a negative electrode sheet, and a battery was assembled and tested. The specific process was the same as in Example 1, and the test results are shown in Table 1.

[0098] To better illustrate the effects of the embodiments of the present invention, comparative examples are compared with the embodiments.

[0099] (Comparative Example 1) This comparative example provides a preparation method and property test of a conventional silicon-carbon composite material, specifically including the following steps: In step S1, 200g of nanosilicon particles and 500g of phenolic resin powder are placed in a hydrothermal reactor and subjected to hydrothermal treatment, with the pressure set to 5MPa, the heating temperature set to 300°C, and the incubation time set to 8 hours. The material is then removed, washed and filtered until the filtrate becomes colorless and transparent, and then dried to obtain spherical precursor material. In step S2, the spherical precursor material is placed in a reactor, heated to 900°C at a heating rate of 3°C / min, and kept at that temperature for 6 hours in a nitrogen atmosphere to carbonize it, thereby obtaining a conventional silicon-carbon composite material.

[0100] The conventional silicon-carbon composite material prepared in this comparative example was used to fabricate a negative electrode sheet, and a battery was assembled and tested. The specific process was the same as in Example 1, and the test results are shown in Table 1.

[0101] (Comparative Example 2) This comparative example provides a preparation process and property test of a silicon-carbon composite material. Unlike Example 1, in this comparative example, only nanosilicon particles are deposited in the through-pores of the porous carbon microspheres, and no metallic lithium particles are deposited. The specific steps are as follows: 1. Under an argon atmosphere, monosilane is transported to the deposition chamber of a vapor phase growth furnace using argon gas as a carrier gas at a flow rate of 0.5 L / min, and vapor phase growth is carried out at 800°C for 20 hours. The silicon-containing gas is deposited in the pores of the through-holes of the porous carbon microspheres to form nanosilicon particles, thereby obtaining a precursor material. 2. The precursor material is vapor-coated to form a carbon shell, resulting in a silicon-carbon composite material.

[0102] The silicon-carbon composite material prepared in this comparative example was used to prepare a negative electrode sheet, and a button battery was assembled and tested. The specific process was the same as in Example 1, and the test results are shown in Table 1.

[0103] (Comparative Example 3) This comparative example provides a preparation process and characteristic test of a negative electrode material. Unlike Example 1, in this comparative example, nanosilicon particles and metallic lithium particles are alternately deposited in the pores of porous carbon microspheres without through-holes, and the negative electrode material is obtained after vapor-phase carbon coating.

[0104] The negative electrode sheet was prepared using the negative electrode material prepared in this comparative example, and a button battery was assembled and tested. The specific process was the same as in Example 1, and the test results are shown in Table 1.

[0105] Table 1 shows the test results of the charge specific capacity and first cycle coulombic efficiency of the batteries assembled in Examples 1 to 10 and Comparative Examples 1 to 3.

[0106] [Table 1]

[0107] Comparing the test data in Table 1, it can be seen that the batteries assembled with the anode materials with high initial charge-discharge efficiency according to Examples 1 to 10 of the present invention have significantly higher initial charge-discharge efficiency than those of Comparative Examples 1 and 2, and higher charge specific capacity than those of Comparative Examples 1 and 3. This is because, in the anode materials with high initial charge-discharge efficiency prepared in Examples 1 to 10 of the present invention, lithium metal particles and nanosilicon particles are formed by depositing gaseous lithium and silicon-containing gas into the through-holes of porous carbon microspheres at intervals. On the one hand, the resulting nanoscale silicon particles have a crystal grain size of less than 45 nm, which effectively reduces the volume expansion effect. At the same time, the nanosilicon and lithium metal are alternately deposited at intervals, which ensures a uniform distribution within the porous carbon microspheres and prevents the aggregation of nanosilicon. On the other hand, the lithium metal and silicon are co-deposited at intervals within the porous carbon microspheres, which prevents the formation of lithium dendrites due to non-uniform lithium distribution and fully exerts the lithium replenishment effect, thereby improving the initial coulombic efficiency of the anode material.

[0108] The above specific embodiments further describe the objectives, technical solutions and beneficial effects of the present invention, and it should be understood that the above are only specific embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0109] (Addendum) (Appendix 1) A negative electrode material for a lithium ion secondary battery having high initial charge / discharge efficiency, The negative electrode material with high initial charge-discharge efficiency comprises a porous carbon matrix, metallic lithium particles, nanosilicon particles, and a carbon shell; wherein the porous carbon matrix is ​​porous carbon microspheres having through-holes, the through-holes having an average pore size of 1 nm to 50 nm; the metallic lithium particles are formed in the through-holes by deposition of gaseous lithium, and the nanosilicon particles are formed in the through-holes by deposition of a silicon-containing gas; the mass of the metallic lithium particles accounts for 10% to 50% of the total mass of the high initial charge-discharge efficiency negative electrode material; The nanosilicon particles have a particle diameter of 0.1 nm to 45 nm, and the mass of the nanosilicon particles accounts for 20% to 70% of the total mass of the high initial charge-discharge efficiency negative electrode material; The negative electrode material with high initial charge / discharge efficiency has a coulombic efficiency of 99% to 105% in the first cycle in a lithium ion secondary battery. A negative electrode material for a lithium ion secondary battery having high initial charge / discharge efficiency.

[0110] (Appendix 2) the mass of the carbon shell accounts for 1% to 20% of the total mass of the high initial charge-discharge efficiency negative electrode material; The particle diameter of the negative electrode material with high initial charge / discharge efficiency is 1 μm to 100 μm. 2. A negative electrode material for a lithium ion secondary battery having high initial charge-discharge efficiency according to claim 1.

[0111] (Appendix 3) A method for preparing a negative electrode material having high initial charge-discharge efficiency for a lithium ion secondary battery according to Supplementary Note 1 or 2, comprising: The preparation method is a vapor phase growth method, specifically: Step S1: placing porous carbon microspheres having through-holes in a deposition chamber of a deposition device under an argon atmosphere; placing metallic lithium in a second furnace chamber of the deposition device and evaporating it at high temperature to form gaseous lithium; transporting the gaseous lithium from the second furnace chamber to the deposition chamber by a carrier gas; and depositing the gaseous lithium in the pores of the porous carbon microspheres to form metallic lithium particles; Step S2: introducing a silicon-containing gas into the deposition chamber and depositing it in the pores of the through-holes of the porous carbon microspheres to form nanosilicon particles; Step S3: alternately repeating Step S1 and Step S2, and introducing gaseous lithium and silicon-containing gases at intervals to uniformly deposit metallic lithium particles and nanosilicon particles in the through-holes of the porous carbon microspheres to obtain a precursor material. Step S4: applying a carbon coating to the precursor material by a gas phase method to form a dense carbon shell on the outer surface of the porous carbon microspheres, thereby obtaining a negative electrode material with high initial charge-discharge efficiency; Including, A preparation method characterized by:

[0112] (Appendix 4) the deposition apparatus comprises any of a vapor deposition furnace, a tubular furnace, a rotary furnace, a bell furnace, or a fluidized bed; wherein the deposition chamber and the second furnace chamber are connected via a first inlet, and the deposition amount of the gaseous lithium can be controlled by adjusting parameters of an automatic intake valve of the first inlet; a second intake port is provided outside the deposition chamber, and a deposition amount of the silicon-containing gas is controlled by adjusting parameters of an automatic intake valve of the second intake port; The temperature at which the lithium is evaporated to gaseous state at a high temperature is 800°C to 1500°C, and the temperature retention time is 1 hour to 20 hours. The carrier gas is argon gas, and the flow rate is 1 L / min to 50 L / min. 4. The method of claim 3,

[0113] (Appendix 5) The silicon-containing gas includes one or more silane gases selected from the group consisting of monosilane, disilane, trisilane, dichlorosilane, trichlorosilane, and tetrachlorosilane. 4. The method of claim 3,

[0114] (Appendix 6) The deposition temperature of the silicon-containing gas is 600°C to 1500°C, the vapor phase growth time is 1 hour to 20 hours, and the gas flow rate is 0.5 L / min to 50 L / min. 4. The method of claim 3,

[0115] (Appendix 7) Specifically, the method for applying carbon coating to the precursor material by a gas phase method includes depositing a carbon source gas at a temperature of 450°C to 1000°C on the outer surface of the porous carbon microspheres on which metallic lithium particles and nanosilicon particles are uniformly deposited in the through-pores to form a carbon shell; wherein the carbon source gas includes one or more of methane, ethane, propane, butane, acetylene, and propylene, the flow rate of the carbon source gas is 1 L / min to 50 L / min, and the deposition time is 1 hour to 15 hours; 4. The method of claim 3,

[0116] (Appendix 8) In the steps 1 and 2, industrial silicon powder and metallic lithium are used as raw materials in a thermal plasma treatment device, and gaseous lithium and silicon vapor are deposited in the pores of the through-holes of the porous carbon microspheres to obtain the precursor material. 4. The method of claim 3,

[0117] (Appendix 9) The negative electrode material for a lithium ion secondary battery having high initial charge-discharge efficiency according to Supplementary Note 1 or 2 is included. A negative electrode sheet characterized by:

[0118] (Appendix 10) Including the negative electrode sheet described in Appendix 9, A lithium-ion secondary battery characterized by:

Claims

1. A negative electrode material for a lithium ion secondary battery having high initial charge / discharge efficiency, The negative electrode material with high initial charge-discharge efficiency comprises a porous carbon matrix, metallic lithium particles, nanosilicon particles, and a carbon shell; wherein the porous carbon matrix is ​​porous carbon microspheres having through-holes, the through-holes having an average pore size of 1 nm to 50 nm; the metallic lithium particles are formed in the through-holes by deposition of gaseous lithium, and the nanosilicon particles are formed in the through-holes by deposition of a silicon-containing gas; the mass of the metallic lithium particles accounts for 10% to 50% of the total mass of the high initial charge-discharge efficiency negative electrode material; The nanosilicon particles have a particle diameter of 0.1 nm to 45 nm, and the mass of the nanosilicon particles accounts for 20% to 70% of the total mass of the high initial charge-discharge efficiency negative electrode material; The negative electrode material with high initial charge / discharge efficiency has a coulombic efficiency of 99% to 105% in the first cycle in a lithium ion secondary battery. A negative electrode material for a lithium ion secondary battery having high initial charge / discharge efficiency.

2. the mass of the carbon shell accounts for 1% to 20% of the total mass of the high initial charge-discharge efficiency negative electrode material; The particle size of the negative electrode material with high initial charge / discharge efficiency is 1 μm to 100 μm.

2. The negative electrode material for a lithium ion secondary battery according to claim 1, which has high initial charge-discharge efficiency.

3. 3. A method for preparing a negative electrode material having high initial charge-discharge efficiency for a lithium ion secondary battery according to claim 1 or 2, comprising: The preparation method is a vapor phase growth method, specifically: Step S1: placing porous carbon microspheres having through-holes in a deposition chamber of a deposition device under an argon atmosphere; placing metallic lithium in a second furnace chamber of the deposition device and evaporating it at high temperature to form gaseous lithium; transporting the gaseous lithium from the second furnace chamber to the deposition chamber by a carrier gas; and depositing the gaseous lithium in the pores of the porous carbon microspheres to form metallic lithium particles; Step S2: introducing a silicon-containing gas into the deposition chamber and depositing it in the pores of the through-holes of the porous carbon microspheres to form nanosilicon particles; Step S3: alternately repeating step S1 and step S2, introducing gaseous lithium and silicon-containing gases at intervals, and uniformly depositing metallic lithium particles and nanosilicon particles in the through-holes of the porous carbon microspheres to obtain a precursor material; Step S4: carbon-coating the precursor material by a gas-phase method to form a dense carbon shell on the outer surface of the porous carbon microspheres, thereby obtaining a negative electrode material with high initial charge-discharge efficiency; Including, A preparation method characterized by:

4. the deposition apparatus comprises any of a vapor deposition furnace, a tubular furnace, a rotary furnace, a bell furnace, or a fluidized bed; wherein the deposition chamber and the second furnace chamber are connected via a first inlet, and the deposition amount of the gaseous lithium can be controlled by adjusting parameters of an automatic intake valve of the first inlet; a second intake port is provided outside the deposition chamber, and a deposition amount of the silicon-containing gas is controlled by adjusting parameters of an automatic intake valve of the second intake port; The temperature at which the lithium is evaporated to gaseous form at a high temperature is 800°C to 1500°C, and the temperature retention time is 1 hour to 20 hours. The carrier gas is argon gas, and the flow rate is 1 L / min to 50 L / min.

4. The method of claim 3.

5. The silicon-containing gas includes one or more silane gases selected from the group consisting of monosilane, disilane, trisilane, dichlorosilane, trichlorosilane, and tetrachlorosilane.

4. The method of claim 3.

6. The deposition temperature of the silicon-containing gas is 600°C to 1500°C, the vapor phase growth time is 1 hour to 20 hours, and the gas flow rate is 0.5 L / min to 50 L / min; 4. The method of claim 3.

7. The method for applying carbon coating to the precursor material by a gas phase method specifically includes depositing a carbon source gas at a temperature of 450°C to 1000°C on the outer surface of the porous carbon microspheres on which metallic lithium particles and nanosilicon particles are uniformly deposited in the through-pores to form a carbon shell; wherein the carbon source gas includes one or more of methane, ethane, propane, butane, acetylene, and propylene, the flow rate of the carbon source gas is 1 L / min to 50 L / min, and the deposition time is 1 hour to 15 hours; 4. The method of claim 3.

8. In the steps 1 and 2, industrial silicon powder and metallic lithium are used as raw materials in a thermal plasma treatment device, and gaseous lithium and silicon vapor are deposited in the pores of the through-holes of the porous carbon microspheres to obtain the precursor material.

4. The method of claim 3.

9. The negative electrode material for a lithium ion secondary battery having high initial charge / discharge efficiency according to claim 1 or 2, A negative electrode sheet characterized by:

10. The negative electrode sheet according to claim 9, A lithium-ion secondary battery characterized by:

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