Silicon-carbon negative electrode material, battery negative electrode, battery and preparation method thereof

Abstract

The present invention discloses a method for preparing a silicon-carbon negative electrode material, which uses a porous carbon material as a substrate, and then performs surface carbon coating after staged silicon source deposition; the staged silicon source deposition includes: in the first stage, the temperature in the reactor is controlled to be 300-800°C, the initial pressure is 10-30Kpa, and the flow rate of the raw gas is 2-10L / min; when the pressure in the reactor begins to drop, the next stage is entered; in the second stage, the initial pressure in the reactor is adjusted to 5-8Kpa, and the flow rate of the raw gas is adjusted to 8-20L / min; when the pressure in the reactor begins to rise, the deposition is terminated. The present invention significantly improves the utilization rate of the pore structure of the porous carbon substrate by performing the silicon deposition process in stages and accurately controlling the deposition process parameters of each stage, and the negative electrode sheet prepared by the prepared silicon-carbon negative electrode material and the assembled battery have excellent initial capacity, first effect and cycle stability.

Description

Technical Field

[0001] The present invention relates to the technical field of negative electrode materials, and in particular to a silicon-carbon negative electrode material, a battery negative electrode, a battery and a preparation method thereof. Background Art

[0002] Silicon is currently the negative electrode material with the largest theoretical capacity, with a specific capacity of up to 4200mAh / g, which is much higher than the theoretical capacity of graphite (the theoretical capacity of graphite-based negative electrode materials is only 372mAh / g). Silicon has the advantages of low lithium insertion potential and low cost, and is expected to replace graphite as the next generation of lithium-ion battery negative electrode material. However, as a negative electrode material, silicon is accompanied by severe volume expansion and contraction during the lithium insertion and de-lithiation process, which makes the material easy to pulverize, fall off the current collector, and lose electrochemical performance.

[0003] Due to the structural stability of carbon materials, the volume change during the charge and discharge process is relatively small, and it has good cycle stability. In addition, similar to the chemical properties of silicon, silicon and carbon are often compounded to achieve the purpose of improving the volume expansion effect of silicon and improving its electrochemical stability. Among them, silicon is deposited on porous carbon materials by chemical vapor deposition, which is currently a more commonly used method for preparing silicon-carbon composite materials. However, in the process of chemical vapor deposition, if the process is not finely regulated, a large amount of silicon is deposited on the surface of porous carbon, and the utilization rate of the porous structure of porous carbon is low, so that the surface is silicon-rich, which will seriously hinder the penetration of electrolytes and the diffusion of lithium ions, thereby affecting the electrochemical performance of the battery; the surface-enriched nano-silicon reacts with lithium to form an alloy, causing the volume expansion of the material, causing the porous carbon structure to be destroyed and unstable, resulting in particle aggregation and disintegration of the electrode material, greatly reducing the cycle stability and capacity retention rate of the electrode. In addition, the enrichment of silicon may also lead to uneven charge distribution on the surface of the material, increase the interface impedance between the electrode and the electrolyte, and further affect the electrochemical performance of the battery.

[0004] A silicon-carbon composite material containing ultra-low Z and its related processes are disclosed in the US patent document with patent number US20230219819A1. This scheme selects and optimizes the preparation and selection of porous supports, the doping and modification of porous supports, and the composite method of nano-silicon and porous supports to prepare a silicon-carbon negative electrode material with high stability. This technical scheme takes the selection of process raw materials and composite methods as the main starting point to ensure that silicon is deposited into the porous carbon, effectively avoiding the enrichment of silicon on the surface of porous carbon, and proposes to indirectly judge the deposition position of silicon by thermogravimetric analysis of mass changes. The judgment formula is Z = 1.875 × [(M1100-M800) / M1100] × 100%.

[0005] A Chinese patent document with application publication number CN116111065A discloses a silicon-carbon negative electrode material, a method for preparing the silicon-carbon negative electrode material, and a lithium-ion battery. The silicon-carbon negative electrode material provided by the method, under the action of inorganic salts, nano-silicon is deposited in the pores of porous carbon, and does not fall on the surface of the porous carbon material, thereby greatly reducing the volume expansion of silicon during lithium storage; and because the nano-silicon is not deposited on the surface of the porous carbon, the carbon coating layer is more uniform, thereby improving the cycle performance and rate performance of the negative electrode material.

[0006] Both of the above preparation methods control the deposition of nano-silicon from aspects such as raw material selection and substrate modification, and require the introduction of other heteroatoms besides silicon and carbon, which cannot directly achieve precise deposition of nano-silicon from a process perspective; and the introduction of heteroatoms, while improving the silicon-carbon bonding ability or conductivity, will also cause structural damage to the silicon-carbon negative electrode, making it incapable of long-term cycle stability. Even if more silicon is deposited into the porous carbon, it is impossible to achieve uniform distribution of deposition, which will still lead to a decrease in cycle stability.

[0007] Therefore, how to effectively control the nano-silicon deposition position from a process perspective, ensure the pore structure utilization of the porous carbon substrate, improve the uniformity of silicon deposition, and prepare high-performance silicon-carbon negative electrode materials are technical problems that need to be solved urgently. Summary of the invention

[0008] In view of the above-mentioned problems existing in the prior art, the present invention discloses a method for preparing a silicon-carbon negative electrode material. By carrying out the silicon deposition process in stages and precisely controlling the deposition process parameters of each stage, the pore structure utilization rate of the porous carbon substrate is significantly improved. The lithium-ion battery assembled with the prepared silicon-carbon negative electrode material has excellent initial capacity, first efficiency and cycle stability.

[0009] The specific technical solutions are as follows:

[0010] A method for preparing a silicon-carbon negative electrode material comprises the following steps:

[0011] Using a porous carbon material as a substrate, depositing nano-silicon particles inside the pores of the porous carbon material after silicon source deposition in stages, and then coating the surface with carbon to obtain the high-performance silicon-carbon negative electrode material;

[0012] The staged silicon source deposition uses silicon source gas as raw material gas for vapor phase deposition, including:

[0013] In the first stage, the temperature in the reactor is controlled to be 300-800°C, the initial pressure is 10-30Kpa, and the flow rate of the raw gas is 2-10L / min; when the pressure in the reactor begins to drop and the pressure change value is 10-70% of the initial pressure, the next stage is entered;

[0014] In the second stage, the initial pressure in the reactor is adjusted to 5-8Kpa, and the flow rate of the raw gas is adjusted to 8-20L / min; when the pressure in the reactor begins to rise and the pressure change value is 10-70% of the initial pressure, the deposition is ended.

[0015] The preparation method disclosed in the present invention ensures that nano-silicon can be efficiently deposited in pore structures of different sizes in porous carbon materials by performing the silicon deposition process in stages and accurately regulating the deposition process parameters of each stage, thereby improving the utilization rate of the pore structure of the porous carbon material and ensuring that the nano-silicon is uniformly deposited in the pores of the porous carbon without falling on the surface of the porous carbon material, thereby giving full play to the confinement effect of the porous carbon and improving the electrochemical performance of the silicon-carbon negative electrode; at the same time, the efficient deposition can effectively avoid the gas production phenomenon in the subsequent process and ensure the safety of the overall process.

[0016] Experiments have shown that, compared with traditional one-time deposition, the staged silicon source deposition disclosed in the present invention can make the deposited nano-silicon particles more evenly distributed and significantly improve the utilization rate of the pore structure under the condition of equivalent deposition amount; the lithium-ion battery assembled with the silicon-carbon negative electrode material prepared by the preparation method disclosed in the present invention has better cycle stability, reversible specific capacity and first efficiency.

[0017] The experiment also found that if the deposition order of the two stages is swapped, or the regulation of the process parameters in each deposition stage is no longer within the above-defined range, the electrochemical performance of the lithium-ion battery assembled with the prepared silicon-carbon negative electrode material will be deteriorated, including the impact on capacity, first effect and cycle stability. The above-mentioned effects may be due to improper control of deposition parameters resulting in low pore structure utilization or uneven deposition of nano-silicon, or even enrichment on the porous carbon surface, etc. Therefore, only by adopting the order of staged deposition disclosed in the present invention and precisely regulating the deposition process parameters of each stage, can a lithium-ion battery with significantly improved pore structure utilization of the porous carbon substrate be prepared and assembled with excellent initial capacity, first effect and cycle stability.

[0018] Preferred:

[0019] The SPAN value of the porous carbon material is less than 1.5, and the D50 is 4 to 10 μm;

[0020] The specific surface area of ​​the porous carbon material is 1200 to 2000 m 2 / g, average pore diameter is 1.5~5.0nm, pore volume is 0.6~2.0cm 3 / g, pore concentration is 0.03~1.0, and the calculation formula is as follows:

[0021]

[0022] P: pore volume;

[0023] P all : total pore volume;

[0024] d max* : Maximum pore size of P>0.005;

[0025] d min* : Minimum pore size with P>0.005.

[0026] It has been found through experiments that the preparation process disclosed in the present invention has good adaptability to porous carbon materials with different specific surface areas, average pore sizes, pore volumes, and pore size concentrations. The purpose of maximizing the utilization rate of the pore structure of the porous carbon material can be achieved by the segmented deposition method disclosed in the present invention and by precisely controlling the parameters of the two-stage deposition. The pore structure utilization rate can reach more than 98%.

[0027] However, based on the volume expansion rate under different silicon deposition amounts and the different effects on the initial specific capacity and first efficiency of the assembled battery, it is preferred to use a specific surface area of ​​1500-2000m 2 / g, average pore diameter is 1.5-3.0nm, pore volume is 0.8-1.6cm 3 / g porous carbon material as the substrate. It has been found through experiments that by using the porous carbon material with the above apparent parameters as the substrate, the silicon deposition amount in the prepared silicon-carbon composite material can be controlled between 50 and 55wt% while ensuring a pore structure utilization rate of more than 98%, and the assembled lithium-ion battery has high specific capacity, high initial efficiency and high cycle stability.

[0028] In this preparation method:

[0029] The silicon source gas is selected from one or more of monosilane, disilane, dichlorosilane, and trichlorosilane;

[0030] The raw material gas is a mixed gas including a silicon source gas and an inert gas, in which the silicon source gas accounts for 70 to 99 vol%, preferably 70 to 85 vol%.

[0031] The inert gas is selected from conventional types in the art, such as nitrogen, neon, argon, krypton, xenon, radon, etc.;

[0032] Preferred:

[0033] In the first stage, the initial pressure is 10-25Kpa, and the flow rate of the raw gas is 3-10L / min;

[0034] In the second stage, the initial pressure is 6-8Kpa, and the flow rate of the raw gas is 8-18L / min.

[0035] Preferred:

[0036] In the first stage, when the pressure change in the reactor is 20-67% of the initial pressure, the next stage is entered;

[0037] In the second stage, when the pressure change in the reactor reaches 15-50% of the initial pressure, the deposition is terminated.

[0038] Further preferred:

[0039] In the first stage, when the pressure change in the reactor is 20-50% of the initial pressure, the next stage is entered;

[0040] In the second stage, when the pressure change in the reactor reaches 15-30% of the initial pressure, the deposition is terminated.

[0041] Experiments have shown that with further optimization of the above deposition process parameters, the assembled lithium-ion battery has more excellent electrochemical properties.

[0042] In the preparation method, the surface carbon coating is carried out by vapor deposition at 400-1000°C using a mixed gas consisting of a carbon source gas and an inert gas as a raw gas.

[0043] The carbon source gas is selected from alkane gases with a cracking temperature of 400 to 1200° C., specifically selected from common types such as acetylene and ethylene.

[0044] In the mixed gas, the volume proportion of the carbon source gas is 60 to 99 vol%.

[0045] The flow rate of the mixed gas is 0.1 to 50 L / min, preferably 0.1 to 10 L / min.

[0046] Preferably, the temperature of the vapor deposition is 400-600°C.

[0047] The present invention also discloses a silicon-carbon negative electrode material prepared according to the above method. After testing, the pore structure utilization rate of the silicon-carbon negative electrode material prepared by this method is greater than 98%, the nano-silicon particles are evenly distributed and mostly exist inside the pores of the porous carbon material, and are not deposited on the surface, and the gas production at room temperature is small, and the safety performance is better.

[0048] According to the test, in the silicon-carbon negative electrode material prepared in this embodiment, the mass ratio of the deposited silicon content to the porous carbon content is (0.5-1.4)P all :1.

[0049] The present invention also discloses a negative electrode sheet, comprising a negative electrode current collector and a negative electrode active material layer deposited on the negative electrode current collector; the negative electrode active material layer contains the silicon-carbon negative electrode material.

[0050] The present invention also discloses a battery, comprising the negative electrode sheet as described above. The negative electrode sheet is prepared by using the silicon-carbon negative electrode material and then assembled to obtain a lithium-ion battery, which has excellent cycle stability, high reversible specific capacity and first coulombic efficiency.

[0051] Compared with the prior art, the present invention has the following advantages:

[0052] The preparation method of the silicon-carbon negative electrode material disclosed in the present invention adopts different deposition environments for pore structures of different sizes in the porous carbon material, ensures the transmission and diffusion of gas molecules in the pore structure, improves the pore structure, especially the utilization rate of the micropore (<2nm) part, reduces the agglomeration of nano-silicon inside the porous carbon to block the channel, realizes the uniform dispersion of nano-silicon particles in the porous substrate, reduces the enrichment of nano-silicon on the surface of the porous carbon, gives full play to the limiting effect of the pore structure on the volume expansion of nano-silicon during lithium insertion and extraction, combines with the porous structure with uniform and concentrated pore size, avoids the destruction of the porous substrate structure caused by stress concentration caused by agglomeration, and greatly improves the cycle stability of the final negative electrode material.

[0053] The pore structure utilization rate of the silicon-carbon negative electrode material prepared by the present invention is greater than 98%, and there is no obvious gas production. The lithium-ion battery assembled with the silicon-carbon negative electrode material has excellent cycle stability. The capacity retention rate after 100 cycles is as high as over 90%, and can reach up to 96% at the highest; the capacity retention rate after 500 cycles is as high as over 85%, and can reach up to 90% at the highest; the powder resistance is low, and it has both high reversible specific capacity and first coulombic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 is a pore size distribution diagram of the porous carbon material used in Example 1;

[0055] Figure 2 is a pore size distribution diagram of the porous carbon material used in Comparative Example 3;

[0056] Figure 3 These are Raman spectra of the silicon-carbon negative electrode materials prepared in Example 1 and Comparative Example 13, respectively. DETAILED DESCRIPTION

[0057] The specific implementation method of the present invention is further described below in conjunction with examples. It should be noted here that the specific implementation method described here is only for illustrating and explaining the present invention and is not intended to limit the scope of protection of the present invention.

[0058] Example 1

[0059] (1) Under argon atmosphere, 100 g of porous carbon material as a substrate (D50 = 6 μm, span value < 1.5) was placed in a thermal deposition furnace at a temperature of 500 °C. The specific surface area of ​​the porous carbon material was 1800 m2 / g, average pore diameter is 2nm, pore volume is 1.2cm 3 / g;

[0060] Figure 1 This is the pore size distribution diagram of the porous carbon material used in this embodiment. After testing, the pore volume distribution of the porous carbon material is 10.64% of ultramicropores (<1nm part), 11.71% of micropores (1-2nm part), 62.77% of mesopores (2-10nm part), 13.32% of mesopores (10-50nm part) and 1.56% of macropores (>50nm). According to the following pore size concentration calculation formula, the pore size concentration of the porous carbon material used in this embodiment is 0.092.

[0061]

[0062] P: pore volume;

[0063] P all : total pore volume;

[0064] d max* : Maximum pore size of P>0.005;

[0065] d min* : Minimum pore size with P>0.005.

[0066] (2) Phase I:

[0067] A mixed gas consisting of 80 vol% monosilane and 20 vol% argon is introduced into the thermal deposition furnace at a flow rate of 5 L / min, and the pressure in the furnace is maintained at 15 KPa, so that silicon particles are continuously nucleated and deposited inside the porous carbon pores, and the gas is continuously ventilated until the pressure in the furnace changes;

[0068] Phase 2:

[0069] When the pressure in the furnace changes to 8Kpa, adjust the flow rate of the mixed gas to 12L / min, adjust the pressure in the furnace to 6Kpa, and continue to ventilate. When the pressure in the furnace increases to 8Kpa, the deposition is terminated.

[0070] (3) After silicon deposition is completed, a mixed gas consisting of 70 vol% acetylene and 30 vol% argon is introduced at a flow rate of 1 L / min for high-temperature carbon coating. The ventilation is continued for 2 hours to control the mass of the carbon coating layer to account for 5wt% of the mass of the final prepared silicon-carbon negative electrode material. The temperature is cooled to room temperature, and the material is dispersed, screened, demagnetized, etc. to obtain a silicon-carbon negative electrode material.

[0071] In this embodiment, a silicon-carbon negative electrode material having a deposited silicon content of 53.7 wt%, a porous carbon content of 41.3 wt%, and a surface carbon coating layer content of 5 wt% is prepared.

[0072] The specific surface area and pore volume data of the finished silicon-carbon negative electrode material prepared in this embodiment are listed in the following Table 1, and the pore structure utilization data of the finished silicon-carbon negative electrode material prepared in this embodiment are calculated according to the following calculation formula and are also listed in Table 1.

[0073]

[0074] P1: pore volume of raw porous carbon material;

[0075] P2: Pore volume of finished silicon-carbon negative electrode material.

[0076] Example 2

[0077] (1) Under argon atmosphere, 100 g of porous carbon material as a substrate (D50 = 6 μm, span value < 1.5) was placed in a thermal deposition furnace at a temperature of 500 °C. The specific surface area of ​​the porous carbon material was 2000 m 2 / g, average pore diameter of 1.5nm, pore volume of 1.6cm 3 / g, pore size concentration is 0.076;

[0078] (2) Phase I:

[0079] A mixed gas consisting of 80 vol% monosilane and 20 vol% argon is introduced into the thermal deposition furnace at a flow rate of 10 L / min, and the pressure in the furnace is maintained at 20 KPa, so that silicon particles are continuously nucleated and deposited inside the porous carbon pores, and the gas is continuously ventilated until a pressure change occurs in the furnace;

[0080] Phase 2:

[0081] When the pressure in the furnace changes to 12Kpa, adjust the flow rate of the mixed gas to 18L / min, adjust the pressure in the furnace to 6Kpa, and continue to ventilate. When the pressure in the furnace increases to 8Kpa, the deposition is terminated.

[0082] Step (3) is exactly the same as in Example 1.

[0083] In this embodiment, a silicon-carbon negative electrode material having a deposited silicon content of 54.2 wt%, a porous carbon content of 40.8 wt%, and a surface carbon coating layer content of 5 wt% is prepared.

[0084] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this embodiment are listed in the following Table 1.

[0085] Example 3

[0086] (1) Under argon atmosphere, 100 g of porous carbon material as a substrate (D50 = 6 μm, span value < 1.5) was placed in a thermal deposition furnace at a temperature of 500 °C. The specific surface area of ​​the porous carbon material was 1500 m 2 / g, average pore diameter is 3nm, pore volume is 0.8cm 3 / g, pore size concentration is 0.094;

[0087] (2) Phase I:

[0088] A mixed gas consisting of 80 vol% monosilane and 20 vol% argon is introduced into the thermal deposition furnace at a flow rate of 3 L / min. The pressure in the furnace is maintained at 12 KPa, so that silicon particles are continuously nucleated and deposited inside the porous carbon pores. The gas is continuously ventilated until a pressure change occurs in the furnace.

[0089] Phase 2:

[0090] When the pressure in the furnace changes to 7Kpa, adjust the flow rate of the mixed gas to 8L / min and continue ventilation. When the pressure in the furnace increases to 9Kpa, the deposition is terminated.

[0091] Step (3) is exactly the same as in Example 1.

[0092] In this embodiment, a silicon-carbon negative electrode material having a deposited silicon content of 51.9 wt %, a porous carbon content of 43.1 wt %, and a surface carbon coating layer content of 5 wt % is prepared.

[0093] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this embodiment are listed in the following Table 1.

[0094] Comparative Example 1

[0095] (1) Under argon atmosphere, 100 g of porous carbon material as a substrate (D50 = 6 μm, span value < 1.5) was placed in a thermal deposition furnace at a temperature of 500 °C. The specific surface area of ​​the porous carbon material was 2400 m 2 / g, average pore diameter of 1nm, pore volume of 2.0cm 3 / g, pore size concentration is 0.087;

[0096] (2) Phase I:

[0097] A mixed gas consisting of 80 vol% monosilane and 20 vol% argon is introduced into the thermal deposition furnace at a flow rate of 5 L / min, and the pressure in the furnace is maintained at 25 KPa, so that silicon particles are continuously nucleated and deposited inside the porous carbon pores, and the gas is continuously ventilated until a pressure change occurs in the furnace;

[0098] Phase 2:

[0099] When the pressure in the furnace changes to 15Kpa, adjust the flow rate of the mixed gas to 12L / min, adjust the pressure in the furnace to 6Kpa, and continue to ventilate. When the pressure in the furnace increases to 8Kpa, the deposition is terminated.

[0100] Step (3) is exactly the same as in Example 1.

[0101] In this comparative example, a silicon-carbon negative electrode material having a deposited silicon content of 58.1 wt%, a porous carbon content of 36.9 wt%, and a surface carbon coating layer content of 5 wt% is prepared.

[0102] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this comparative example are listed in the following Table 1.

[0103] Comparative Example 2

[0104] (1) Under argon atmosphere, 100 g of porous carbon material as a substrate (D50 = 6 μm, span value < 1.5) was placed in a thermal deposition furnace at a temperature of 500 °C. The specific surface area of ​​the porous carbon material was 1000 m 2 / g, average pore diameter is 10nm, pore volume is 0.6cm 3 / g, pore size concentration is 0.095;

[0105] (2) Phase I:

[0106] A mixed gas consisting of 80 vol% monosilane and 20 vol% argon is introduced into the thermal deposition furnace at a flow rate of 5 L / min. The pressure in the furnace is maintained at 10 KPa, so that silicon particles are continuously nucleated and deposited inside the porous carbon pores. The gas is continuously ventilated until a pressure change occurs in the furnace.

[0107] Phase 2:

[0108] When the pressure in the furnace changes to 7Kpa, adjust the flow rate of the mixed gas to 12L / min and continue ventilation. When the pressure in the furnace increases to 10Kpa, the deposition is terminated.

[0109] Step (3) is exactly the same as in Example 1.

[0110] In this comparative example, a silicon-carbon negative electrode material having a deposited silicon content of 43.7 wt %, a porous carbon content of 51.3 wt %, and a surface carbon coating layer content of 5 wt % is prepared.

[0111] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this comparative example are listed in the following Table 1.

[0112] Comparative Example 3

[0113] The preparation process is basically the same as that in Example 1, except that the pore size concentration of the porous carbon material selected in step (1) is 0.025 and the specific surface area is 1852 m 2 / g, average pore diameter of 1.9nm, pore volume of 1.2cm 3 / g. Figure 2 This is the pore size distribution diagram of the porous carbon material used in this comparative example.

[0114] In this comparative example, a silicon-carbon negative electrode material having a deposited silicon content of 52.1 wt%, a porous carbon content of 42.9 wt%, and a surface carbon coating layer content of 5 wt% is prepared.

[0115] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this comparative example are listed in the following Table 1.

[0116] Comparative Example 4

[0117] Step (1) is the same as in Example 1;

[0118] (2) A mixed gas consisting of 80 vol% monosilane and 20 vol% argon is introduced into the thermal deposition furnace at a flow rate of 10 L / min, the pressure in the furnace is maintained at 8 KPa, and the ventilation is continued for 10 hours;

[0119] Step (3) is the same as in Example 1.

[0120] In this comparative example, a silicon-carbon negative electrode material having a deposited silicon content of 50.8 wt %, a porous carbon content of 44.2 wt %, and a surface carbon coating layer content of 5 wt % is prepared.

[0121] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this comparative example are listed in the following Table 1.

[0122] Comparative Example 5

[0123] Step (1) is the same as in Example 1;

[0124] (2) Phase I:

[0125] A mixed gas consisting of 80 vol% monosilane and 20 vol% argon was introduced into the thermal deposition furnace at a flow rate of 12 L / min. The pressure in the furnace was maintained at 6 KPa, so that silicon particles were continuously nucleated and deposited inside the porous carbon pores. The gas was continuously ventilated for 7 hours.

[0126] Phase 2:

[0127] Adjust the flow rate of the mixed gas to 5L / min, adjust the pressure in the furnace to 12Kpa, continue ventilation for 3h, and end the deposition;

[0128] Step (3) is the same as in Example 1.

[0129] In this comparative example, a silicon-carbon negative electrode material having a deposited silicon content of 45.7 wt %, a porous carbon content of 49.3 wt %, and a surface carbon coating layer content of 5 wt % is prepared.

[0130] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this comparative example are listed in the following Table 1.

[0131] Comparative Example 6

[0132] The preparation process is basically the same as that in Example 1, except that the flow rate of the mixed gas in the first stage in step (2) is replaced with 12 L / min.

[0133] In this comparative example, a silicon-carbon negative electrode material having a deposited silicon content of 44.9 wt %, a porous carbon content of 50.1 wt %, and a surface carbon coating layer content of 5 wt % is prepared.

[0134] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this comparative example are listed in the following Table 1.

[0135] Comparative Example 7

[0136] The preparation process is basically the same as that in Example 1, except that the flow rate of the mixed gas in the second stage in step (2) is replaced with 3 L / min.

[0137] In this comparative example, a silicon-carbon composite material having a deposited silicon content of 52.7 wt %, a porous carbon content of 42.3 wt %, and a surface carbon coating layer content of 5 wt % was prepared.

[0138] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this comparative example are listed in the following Table 1.

[0139] Comparative Example 8

[0140] The preparation process is basically the same as that in Example 1, except that the furnace pressure in the first stage of step (2) is replaced with 32 KPa.

[0141] In this comparative example, a silicon-carbon negative electrode material having a deposited silicon content of 51.9 wt %, a porous carbon content of 43.1 wt %, and a surface carbon coating layer content of 5 wt % is prepared.

[0142] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this comparative example are listed in the following Table 1.

[0143] Comparative Example 9

[0144] The preparation process is basically the same as that in Example 1, except that the furnace pressure in the first stage of step (2) is replaced with 5 KPa.

[0145] In this comparative example, a silicon-carbon negative electrode material having a deposited silicon content of 48.5 wt %, a porous carbon content of 46.5 wt %, and a surface carbon coating layer content of 5 wt % is prepared.

[0146] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this comparative example are listed in the following Table 1.

[0147] Comparative Example 10

[0148] The preparation process is basically the same as that in Example 1, except that the pressure in the furnace in the second stage of step (2) is replaced with 12 KPa.

[0149] In this comparative example, a silicon-carbon negative electrode material having a deposited silicon content of 54.3 wt%, a porous carbon content of 40.7 wt%, and a surface carbon coating layer content of 5 wt% is prepared.

[0150] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this comparative example are listed in the following Table 1.

[0151] Example 4

[0152] The preparation process is basically the same as that in Example 1, with the only difference being that in the second stage of step (2), when the pressure in the furnace changes to 12 Kpa, the flow rate of the mixed gas is adjusted to 12 L / min, the pressure in the furnace is adjusted to 6 Kpa, and ventilation is continued. When the pressure in the furnace increases to 8 Kpa, the deposition is terminated.

[0153] In this embodiment, a silicon-carbon negative electrode material having a deposited silicon content of 51.3 wt%, a porous carbon content of 43.7 wt%, and a surface carbon coating layer content of 5 wt% is prepared.

[0154] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this embodiment are listed in the following Table 1.

[0155] Example 5

[0156] The preparation process is basically the same as that in Example 1, with the only difference being that in the second stage of step (2), when the pressure in the furnace changes to 5 KPa, the flow rate of the mixed gas is adjusted to 12 L / min, the pressure in the furnace is adjusted to 6 KPa, and ventilation is continued. When the pressure in the furnace increases to 8 KPa, the deposition is terminated.

[0157] In this embodiment, a silicon-carbon negative electrode material having a deposited silicon content of 53.1 wt%, a porous carbon content of 41.9 wt%, and a surface carbon coating layer content of 5 wt% is prepared.

[0158] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this embodiment are listed in the following Table 1.

[0159] Comparative Example 11

[0160] The preparation process is basically the same as that in Example 1, with the only difference being that in the second stage of step (2), when the pressure in the furnace changes to 14 Kpa, the flow rate of the mixed gas is adjusted to 12 L / min, the pressure in the furnace is adjusted to 6 Kpa, and ventilation is continued. When the pressure in the furnace increases to 8 Kpa, the deposition is terminated.

[0161] In this comparative example, a silicon-carbon negative electrode material having a deposited silicon content of 48.9 wt %, a porous carbon content of 46.1 wt %, and a surface carbon coating layer content of 5 wt % is prepared.

[0162] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this comparative example are listed in the following Table 1.

[0163] Comparative Example 12

[0164] The preparation process is basically the same as that in Example 1, with the only difference being that in the second stage of step (2), when the pressure in the furnace changes to 3 Kpa, the flow rate of the mixed gas is adjusted to 12 L / min, the pressure in the furnace is adjusted to 6 Kpa, and ventilation is continued. When the pressure in the furnace increases to 8 Kpa, the deposition is terminated.

[0165] In this comparative example, a silicon-carbon negative electrode material having a deposited silicon content of 53.8 wt %, a porous carbon content of 41.2 wt %, and a surface carbon coating layer content of 5 wt % is prepared.

[0166] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this comparative example are listed in the following Table 1.

[0167] Example 6

[0168] The preparation process is basically the same as that in Example 1, with the only difference being that in the second stage of step (2), when the pressure in the furnace changes to 8 KPa, the flow rate of the mixed gas is adjusted to 12 L / min, the pressure in the furnace is adjusted to 6 KPa, and ventilation is continued. When the pressure in the furnace increases to 7 KPa, the deposition is terminated.

[0169] In this embodiment, a silicon-carbon negative electrode material having a deposited silicon content of 52.8 wt %, a porous carbon content of 42.2 wt %, and a surface carbon coating layer content of 5 wt % is prepared.

[0170] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this embodiment are listed in the following Table 1.

[0171] Example 7

[0172] The preparation process is basically the same as that in Example 1, with the only difference being that in the second stage of step (2), when the pressure in the furnace changes to 8 KPa, the flow rate of the mixed gas is adjusted to 12 L / min, the pressure in the furnace is adjusted to 6 KPa, and ventilation is continued. When the pressure in the furnace increases to 9 KPa, the deposition is terminated.

[0173] In this embodiment, a silicon-carbon negative electrode material having a deposited silicon content of 55.1 wt%, a porous carbon content of 39.9 wt%, and a surface carbon coating layer content of 5 wt% is prepared.

[0174] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this embodiment are listed in the following Table 1.

[0175] Comparative Example 13

[0176] The preparation process is basically the same as that in Example 1, with the only difference being that in the second stage of step (2), when the pressure in the furnace changes to 8 Kpa, the flow rate of the mixed gas is adjusted to 12 L / min, the pressure in the furnace is adjusted to 6 Kpa, and ventilation is continued. When the pressure in the furnace increases to 11 Kpa, the deposition is terminated.

[0177] In this comparative example, a silicon-carbon negative electrode material having a deposited silicon content of 58.4 wt%, a porous carbon content of 36.6 wt%, and a surface carbon coating layer content of 5 wt% is prepared.

[0178] The specific surface area, pore volume and pore structure utilization rate data of the finished silicon-carbon negative electrode material prepared in this comparative example are listed in the following Table 1.

[0179] Figure 3 The Raman spectra of the silicon-carbon negative electrode materials prepared in Example 1 and Comparative Example 13 are shown in Figure 1. -1 The silicon characteristic peak at 480cm-1 is more significant due to the accumulation and enrichment of silicon particles. The higher the accumulation and enrichment of silicon particles, the greater the intensity of the silicon peak. Based on this, by comparing the Raman spectrum curves of Example 1 and Comparative Example 13, it can be clearly seen that silicon-rich conditions appear in the Raman spectrum curve of Comparative Example 13. -1 The intensity of the silicon characteristic peak at the position increases significantly, indicating that during the silicon deposition process, if the process parameters are not properly controlled, it will lead to serious accumulation of silicon particles and silicon-rich appearance on the surface of the porous carbon material.

[0180] Test Case

[0181] In order to verify the accuracy of the conclusion that in the segmented deposition disclosed above, the first stage is used to deposit the microporous part of the porous carbon material, and the second stage is used to deposit the mesoporous part of the porous carbon material, the following verification is performed:

[0182] The preparation process is basically the same as that in Example 1, except that in step (2):

[0183] Phase 1:

[0184] A mixed gas consisting of 80 vol% monosilane and 20 vol% argon is introduced into the thermal deposition furnace at a flow rate of 5 L / min, and the pressure in the furnace is maintained at 15 KPa;

[0185] Phase 2:

[0186] When the pressure in the furnace changes to 8Kpa, a mixed gas consisting of 80vol% acetylene and 20vol% argon is introduced into the thermal deposition furnace at a flow rate of 12L / min, and the pressure in the furnace is adjusted to 6Kpa. The ventilation is continued until the pressure in the furnace increases to 8Kpa, and the deposition is completed.

[0187] After testing, a silicon-carbon negative electrode material with a deposited silicon content of 12.7wt%, a deposited carbon content of 42.1wt%, a porous carbon content of 40.2wt%, and a surface carbon coating content of 5wt% was finally prepared.

[0188] From the parameters of the porous carbon material in Example 1, it can be seen that the ratio of its mesoporous part (2-50nm) to its microporous part (≤2nm) is about 3.404, and the mass ratio of the deposited carbon to the deposited silicon obtained from the above test is about 3.314, and the two values ​​are equivalent. It can be inferred that the judgment basis of the segmented interval of the segmented process of the present invention meets the actual porous carbon pore structure distribution.

[0189] Performance Test:

[0190] 1. The specific surface area and pore volume data of the finished silicon-carbon negative electrode materials prepared in the above embodiments and comparative examples were tested, and the pore structure utilization rate was calculated using the above formula (1), which are listed in the following Table 1.

[0191] Table 1

[0192]

[0193]

[0194] 2. Room temperature gas production test: Add 300 mL of deionized water to a well-sealed bottle, then add 1 g of the silicon-carbon negative electrode material prepared in each embodiment or each comparative example, cover the bottle cap to ensure that there is no air leakage, shake evenly and let it stand for 10 minutes, quickly unscrew the bottle cap, and then insert the instrument for detecting gas concentration into the bottle, read the reading of the instrument, which is the initial gas production value of the silicon-carbon negative electrode material; wait for a while with the bottle open, put the gas detection instrument into the bottle, and tighten the bottle cap when the reading is 0. After 24 hours, shake evenly in the same way, and repeat the above test operation; repeat the 24-hour test operation at 48 hours and 72 hours, and record the initial, 24-hour, 48-hour, and 72-hour gas production values. The test results are shown in Table 2 below.

[0195] Table 2

[0196]

[0197]

[0198] During the silicon-carbon deposition process, if the silicon nanoparticles are well deposited in the porous carbon, that is, evenly distributed, without obvious pore blockage, high pore structure utilization and low porosity, the gas production data is good, and the 24h, 48h and even 72h gas production data are not significantly changed compared with the initial value. If uneven deposition, agglomeration and other conditions occur, the initial gas production value increases significantly, and the gas production increases rapidly as time goes on. Therefore, the normal temperature gas production test can indirectly judge the silicon deposition state. The gas production can effectively illustrate the safety of related materials. The larger the gas production, the worse the safety of the product.

[0199] Application Examples

[0200] The silicon-carbon negative electrode materials prepared in each embodiment and each comparative example were respectively assembled into batteries in the following manner.

[0201] (1) Preparation of positive electrode sheets: The positive electrode active material lithium nickel cobalt manganese oxide (NCM811), the conductive agent SuperP, carbon nanotubes, the binder polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) were mixed in a mass ratio of 97:1:0.5:1.5 to form a positive electrode slurry (solid content of 70wt%), which was coated on both sides of the current collector aluminum foil, dried at 100°C, and cold pressed at 4KPa at room temperature, and then trimmed, cut, and slit, and the tabs were welded to form positive electrode sheets.

[0202] (2) Preparation of negative electrode sheet: Under nitrogen protective atmosphere, the solvent NMP and the binder PVDF are stirred and mixed, and then the conductive agent SuperP is added and stirred and mixed, and then the negative electrode active material is added and stirred and mixed thoroughly to prepare a negative electrode slurry (solid content is 50wt%).

[0203] The negative electrode active material is obtained by fully and uniformly mixing the silicon-carbon negative electrode materials prepared in the above embodiment and comparative example and graphite so that the gram capacity of the negative electrode material is 450 mAh / g.

[0204] The negative electrode slurry is coated on both sides of the current collector copper foil, dried at 100°C, cold pressed at 4Kpa at room temperature, and then trimmed, cut, stripped, and the tabs are welded to make negative electrode sheets.

[0205] (3) Assembly of lithium-ion batteries

[0206] Using PE porous polymer film as a separator, the prepared positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets, and wound to obtain a bare battery cell; the bare battery cell is placed in an aluminum plastic shell package, and dried at 100°C to a moisture content of less than 100 ppm under a relative vacuum pressure of -0.95×105Pa. The electrolyte is injected into the dried bare battery cell, wherein the electrolyte is composed of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC).

[0207] (EC:EMC:DEC volume ratio = 1:1:1) and LiPF6 (1.0M), and are packaged, left to stand, formed (0.02C constant current charging for 2h, 0.1C constant current charging for 2h), shaped, and capacity tested (capacity division) to make a soft-pack liquid lithium-ion battery.

[0208] When assembling the battery, five batteries are prepared for each test, and a total of five sets of data are tested. The final performance is the average value of the five sets of data.

[0209] The battery cycle performance is tested on the Xinwei equipment, specifically:

[0210] At 25°C, first discharge at 0.1C to 0.005V, then discharge at 0.08C to 0.001V, discharge at 0.05C to 0.001V, discharge at 0.02C to 0.001V, and let stand for 10 minutes; then charge to 1.5V at 0.1C, let stand for 10 minutes, record the charge and discharge capacity after the first cycle, and calculate the first coulomb efficiency; cycle 100 times in the above manner, record the charge and discharge capacity after 100 times, calculate the capacity retention rate after 100 cycles, and the test and calculation process of the capacity retention rate after 500 cycles adopt the same method; the powder resistance is measured by a semiconductor powder resistivity tester (30MPa four-probe V1.4), and the test results are shown in Table 3 below.

[0211] Table 3

[0212]

[0213]

[0214] Data Analysis:

[0215] Combined with the data in Tables 1 to 3, the comprehensive performance analysis of silicon-carbon negative electrode materials is carried out. The specific analysis is as follows:

[0216] Comparing the data of Examples 1 to 3 and Comparative Examples 1 to 3, it can be seen that when porous carbon materials with different specific surface areas, average pore sizes, pore volumes, and pore size concentrations are used as substrates, the purpose of maximizing the pore structure utilization rate of the porous carbon substrate can be achieved by accurately controlling the parameters of the two-stage deposition through the segmented deposition method disclosed in the present invention. However, if a porous carbon material with an average pore size that is too small is selected as the substrate (Comparative Example 1), the silicon deposition amount is too large under the condition of high pore structure utilization, and the cycle stability performance of the silicon-carbon negative electrode material is seriously affected by silicon expansion, the performance degradation is accelerated, and the cycle stability becomes poor; when a porous carbon material with an average pore size that is too large is selected as the substrate (Comparative Example 2), due to the limited pore volume, the silicon deposition amount is low, the reversible specific capacity decreases, and the first coulombic efficiency decreases. When the average pore size and pore volume of the selected porous carbon material are appropriate, but the pore size concentration is too low (Comparative Example 3), the uniformity of the deposited silicon is poor, and local stress concentration will occur during expansion, resulting in a decrease in the overall electrochemical performance.

[0217] Comparing the data of Example 1 with those of Examples 4 and 5, and comparing with the traditional single deposition (Comparative Example 4, i.e., non-segmented process), under the condition of equivalent deposition amount, the segmented deposition in Example 1 can make the nano-silicon particles more evenly distributed, the pore structure utilization rate higher, and have more excellent cycle stability; According to the data of Comparative Example 5, it can be seen that the battery assembled with silicon-carbon negative electrode materials prepared by exchanging the segmented deposition sequence has limited cycle stability and greatly increased surface resistance. This may be due to the unreasonable design of deposition process parameters, which leads to pore blocking, silicon surface deposition and other phenomena, which is not conducive to subsequent battery cycle application.

[0218] Comparing Example 1 with Comparative Examples 6 and 7, if a faster gas flow rate is used in the first stage, the utilization rate of the pore structure will be significantly reduced, which may be due to the clogging of the pores caused by too fast deposition, and the utilization rate of the pore structure, especially the micropores, will be significantly reduced; and the gas production will increase significantly, and the safety and cycle stability will be affected; if a lower gas flow rate is used in the second stage, the gas production will increase significantly; this may be because the lower gas flow rate is combined with the lower pressure in the furnace, and the deposition efficiency is low, resulting in uneven distribution of nano-silicon particles and a significant increase in gas production.

[0219] Comparing Example 1 with Comparative Examples 8 to 10, if an excessively high reaction pressure is used in the first stage (Comparative Example 8), the pore structure utilization rate of the prepared silicon-carbon negative electrode material will decrease, and the gas production will increase significantly. This may be because the deposition rate is too fast, the nano-silicon distribution is extremely uneven, and a large number of pore blockages occur, which seriously affects the cycle performance and safety performance of the silicon-carbon negative electrode; if an excessively high reaction pressure is used in the second stage (Comparative Example 10), the gas production will also increase significantly, also because the deposition rate is too fast, the nano-silicon distribution is extremely uneven, and the cycle performance and safety performance of the silicon-carbon negative electrode are seriously affected. If an excessively low reaction pressure is used in the first stage (Comparative Example 9), the decrease in micropore utilization leads to a significant decrease in pore structure utilization, and a significant increase in gas production; the low pore structure utilization leads to a relative decrease in deposition, and a decrease in capacity and first efficiency.

[0220] By comparing Examples 1, 4 to 5 with Comparative Examples 11 to 12, it can be seen that pressure changes occur in the first stage. If the ratio of the pressure change value to the initial pressure is too small (Comparative Example 11), the pore structure utilization rate of the prepared silicon-carbon negative electrode material decreases, and the capacity and first efficiency of the assembled battery both decrease. The possible reasons are: the micropore part is not fully filled, resulting in a decrease in micropore utilization, and the deposited silicon content also decreases accordingly, resulting in a slight decrease in capacity and first efficiency; if the ratio of the pressure change value to the initial pressure is too large (Comparative Example 12), the pore structure utilization rate of the prepared silicon-carbon negative electrode material does not change much, but the cycle stability of the assembled battery is significantly deteriorated. The possible reasons are: after the micropore deposition is completed, the mesoporous part is still deposited at a higher pressure. Combined with the subsequent deposition process, the local deposition amount of the mesoporous part is too large and the distribution is uneven, the gas production increases, and the cycle performance deteriorates significantly.

[0221] By comparing Examples 1, 6, and 7 with Comparative Example 13, it can be seen that in the second stage, the pressure change is used to determine whether to end the deposition. Appropriate pressure changes ensure a higher pore structure utilization rate and a higher silicon deposition amount, thereby ensuring the excellent electrochemical performance of the final assembled battery. However, if the ratio of the pressure change value to the initial pressure is too large, the deposition of silicon on the porous carbon surface increases, the resistance increases significantly, the gas production increases, and the cycle performance deteriorates significantly.

[0222] The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not used to limit the present invention. A technician in the technical field to which the present invention belongs can also make several simple deductions, deformations, substitutions or combinations based on the concept of the present invention. These deductions, deformations, substitutions or combinations also fall within the scope of the claims of the present invention.

Claims

1. A method for preparing a silicon-carbon negative electrode material, characterized in that: The steps include: Using a porous carbon material as a substrate, depositing nano-silicon particles inside the pores of the porous carbon material after silicon source deposition in stages, and then coating the surface with carbon to obtain a silicon-carbon negative electrode material; The SPAN value of the porous carbon material is lower than 1.5, and the D50 is 4-10 μm; The specific surface area of ​​the porous carbon material is 1200-2000 m 2 / g, average pore diameter is 1.5~5.0nm, pore volume is 0.6~2.0cm 3 / g, pore size concentration is 0.03~1.0, and the calculation formula is as follows: ； P: pore volume; P all : total pore volume; d max* : Maximum pore size of P>0.005; d min* : Minimum pore size of P>0.005; The staged silicon source deposition is performed by vapor phase deposition using a raw material gas including a silicon source gas, comprising: In the first stage, the temperature in the reactor is controlled at 300-800°C, the initial pressure is 10-30Kpa, and the flow rate of the raw gas is 2-10L / min; when the pressure in the reactor begins to drop and the pressure change value is 10-70% of the initial pressure, it enters the next stage; The silicon source gas is selected from one or more of monosilane, disilane, dichlorosilane, and trichlorosilane; The raw material gas is a mixed gas including a silicon source gas and an inert gas, wherein the silicon source gas accounts for 70-99 vol% of the mixed gas; In the second stage, the initial pressure in the reactor is adjusted to 5~8Kpa, and the flow rate of the raw gas is adjusted to 8~20L / min; when the pressure in the reactor begins to rise and the pressure change value is 10~70% of the initial pressure, the deposition is ended.

2. The method for preparing the silicon-carbon negative electrode material according to claim 1, characterized in that: In the first stage, when the pressure change value in the reactor is 20-67% of the initial pressure, the next stage is entered; In the second stage, when the pressure change in the reactor reaches 15-50% of the initial pressure, the deposition is terminated.

3. The method for preparing the silicon-carbon negative electrode material according to claim 1, characterized in that: The specific surface area of ​​the porous carbon material is 1500-2000 m 2 / g, average pore diameter is 1.5~3.0nm, pore volume is 0.8~1.6cm 3 / g.

4. The method for preparing the silicon-carbon negative electrode material according to claim 1, characterized in that: In the first stage, when the pressure change value in the reactor is 20-50% of the initial pressure, the next stage is entered; In the second stage, when the pressure change in the reactor reaches 15-30% of the initial pressure, the deposition is terminated.

5. The method for preparing the silicon-carbon negative electrode material according to claim 1, characterized in that: The surface carbon coating is carried out by vapor deposition at 400-1000°C using a mixed gas consisting of a carbon source gas and an inert gas as a raw gas.

6. The method for preparing the silicon-carbon negative electrode material according to claim 5, characterized in that: The surface carbon coating: The carbon source gas is selected from alkane gas with a cracking temperature of 400-1200°C; In the mixed gas, the volume proportion of carbon source gas is 60~99 vol%; The flow rate of the mixed gas is 0.1~50 L / min; The temperature of the vapor deposition is 400-600°C.

7. A silicon-carbon negative electrode material prepared by the method according to any one of claims 1 to 6, characterized in that: The silicon-carbon negative electrode material has a deposited silicon content of 40-60 wt% and a specific surface area of ​​<25 m 2 / g, pore structure utilization rate>96%, powder resistance<35Ω•cm, 72h gas production value<110ppm.

8. The silicon-carbon negative electrode material according to claim 7, characterized in that: The silicon-carbon negative electrode material has a deposited silicon content of 50-55 wt% and a specific surface area of ​​<5.0 m 2 / g, pore structure utilization rate>98%, powder resistance<5Ω•cm, 72h gas production value<90ppm.

9. A negative electrode plate, characterized in that: comprising a negative electrode current collector and a negative electrode active material layer deposited on the negative electrode current collector; The negative electrode active material layer comprises the silicon-carbon negative electrode material as claimed in claim 7 or 8.

10. A battery, characterized in that: Comprising the negative electrode sheet as claimed in claim 9.

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