Porous carbon material, silicon carbon negative electrode, battery negative electrode plate, battery and method of manufacturing the same

Abstract

A porous carbon material, wherein the pore diameter concentration of the porous carbon material is 0.03 to 1.0, and the calculation formula is as follows, in which P: pore volume; P all : total pore volume; d max* : Maximum pore diameter when P>0.005; d min* The lithium ion batteries assembled with the anode materials manufactured by the method for manufacturing various silicon carbon anode materials using the porous carbon material as a substrate all have high capacity, high initial coulombic efficiency, and excellent cycle stability. JPEG2026505513000011.jpg46169

Description

[Technical Field]

[0001] The present invention relates to the technical field of secondary batteries, and in particular to porous carbon materials, silicon carbon negative electrodes, battery negative electrode plates, batteries, and methods for manufacturing the same. [Background technology]

[0002] Silicon is currently the anode material with the highest theoretical capacity, reaching a maximum of 4200 mAh / g, far exceeding the theoretical capacity of graphite (graphite-based anode materials have a theoretical capacity of only 372 mAh / g). Silicon also boasts the advantages of low lithium absorption potential and low cost, making it expected to replace graphite as the anode material for next-generation lithium-ion batteries. However, as anode materials, silicon experiences severe volume expansion and contraction during lithium absorption and desorption, leading to material pulverization and detachment from the current collector, resulting in a loss of electrochemical performance. Due to the structural stability of carbon materials, their volume change during charging and discharging is relatively small, resulting in excellent cycling stability. Their chemical properties are similar to those of silicon. To improve the volume expansion effect of silicon and enhance its electrochemical stability, silicon is often composited with carbon.

[0003] Currently, the main methods for silicon-carbon composites are as follows: 1) Nanosilicon is ground to less than 100 nm using a ball mill to reduce the silicon crystal grains to about 20 nm, and then coated with amorphous carbon to obtain a silicon-carbon composite. However, this method has problems with the nanosilicon agglomerating and being susceptible to oxidation, resulting in low initial coulombic efficiency. 2) Silicon is decomposed using gaseous silane, i.e., silicon is decomposed at high temperatures to form silicon crystal grains with a particle size of less than 5 nm, which are then deposited on porous carbon to obtain a silicon-carbon composite. This method has the advantages of high specific capacity and high initial coulombic efficiency. However, if the particle size of the deposited silicon is limited only by the pore size of the carbon substrate, excessive particle size caused by agglomeration during silicon deposition cannot be avoided. The silicon will still be present in the porous carbon substrate with a large size, and the silicon particles will easily melt together after deposition. Reducing the size of the internal pore voids is also unfavorable for buffering the volume change of silicon during the lithium absorption / desorption process. At the same time, the increase in silicon crystal grain size will further worsen the expansion of silicon and damage the material structure. Summary of the Invention

[0004] In response to the shortcomings of the prior art, the present invention discloses a porous carbon material, which has a concentrated pore structure with a high concentration of pore diameters and an optimized pore size and distribution. The porous carbon material is used as a substrate to prepare a silicon carbon anode material, which can be further assembled into a battery with high capacity, high initial coulombic efficiency, and excellent cycle stability.

[0005] The specific technical proposals are as follows: A porous carbon material, The pore diameter concentration of the porous carbon material is 0.03 to 1.0, and the calculation formula is as follows: JPEG2026505513000002.jpg46169P:Pore volume; P all : total pore volume; d max* : Maximum pore size when P>0.005; dmin* :Minimum pore size when P>0.005.

[0006] Preferably, the porous carbon material has a SPAN value of less than 1.5 and a D50 of 4 to 10 μm; The specific surface area of ​​the porous carbon material is 300 to 3000 m 2 / g, the average pore diameter is 1 to 10 nm, and the pore volume is 0.5 to 2.0 cm 3 / g.

[0007] More preferably, The specific surface area of ​​the porous carbon material is 1200 to 2000 m 2 / g, the average pore diameter is 1.5 to 5.0 nm, and the pore volume is 0.6 to 2.0 cm 3 / g.

[0008] The porous carbon material disclosed in the present invention has a high concentration of pore diameters, an optimized pore diameter size and distribution, and a concentrated pore structure.

[0009] The present invention discloses a method for producing a silicon-carbon anode material based on the porous carbon material, the method comprising: The method includes using a porous carbon material as a substrate, depositing a silicon source in stages, depositing nanosilicon particles inside the pores of the porous carbon material, and further coating the surface with carbon to obtain the high-performance silicon-carbon anode material.

[0010] The stepwise silicon source deposition is performed by vapor-phase deposition using a silicon source gas as a raw material gas, The temperature in the reactor is controlled to 300 to 800°C, the initial pressure is controlled to 10 to 30 Kpa, and the flow rate of the introduced raw material gas is controlled to 2 to 10 L / min. When the pressure in the reactor starts to decrease and the pressure change value reaches 10 to 70% of the initial pressure, the next stage is started. a second stage in which the initial pressure in the reactor is adjusted to 5-8 Kpa, the flow rate of the introduced raw material gas is adjusted to 8-20 L / min, the pressure in the reactor starts to increase, and deposition is terminated when the pressure change value reaches 10-70% of the initial pressure.

[0011] This manufacturing method divides the silicon deposition process into stages, and precisely adjusts the deposition process parameters for each stage to ensure that nanosilicon can be efficiently deposited in the different sized pore structures of the porous carbon material, improving the pore structure utilization rate of the porous carbon material and ensuring that the nanosilicon does not fall onto the surface of the porous carbon material but is uniformly deposited within the pores of the porous carbon, fully utilizing the confining effect of the porous carbon and improving the electrochemical performance of the silicon carbon anode. At the same time, efficient deposition can effectively avoid gas generation during subsequent processes and ensure the safety of the entire process.

[0012] Tests have shown that compared with conventional bulk deposition, the stepwise silicon source deposition disclosed in the present invention can more uniformly distribute the deposited nanosilicon particles and significantly improve the pore structure utilization rate under the same deposition amount, and that lithium ion batteries assembled with the silicon carbon anode material prepared by the method disclosed in the present invention have better cycle stability, reversible specific capacity, and first coulombic efficiency.

[0013] Tests have also shown that if the deposition sequence of the two steps is reversed or the process parameters for each deposition step are not adjusted within the above-mentioned ranges, the electrochemical performance of lithium-ion batteries assembled with the silicon-carbon anode material will deteriorate, affecting capacity, initial coulombic efficiency, and cycling stability. These effects may be due to poor control of the deposition parameters, resulting in low pore structure utilization, uneven deposition of nanosilicon, or even concentration on the surface of the porous carbon. Therefore, only by adopting the step-by-step deposition sequence disclosed in the present invention and precisely adjusting the deposition process parameters for each step can the pore structure utilization of the porous carbon substrate be significantly improved, allowing the fabrication and assembly of lithium-ion batteries with excellent initial capacity, initial coulombic efficiency, and cycling stability.

[0014] Tests have shown that the manufacturing process disclosed in the present invention is well suited to porous carbon materials with different specific surface areas, average pore diameters, pore volumes, and pore diameter concentrations. By precisely controlling the deposition parameters of the two stages of the step-by-step deposition method disclosed in the present invention, the goal of maximizing the utilization rate of the pore structure of the porous carbon material can be achieved, with the utilization rate reaching 98% or more. However, considering the volume expansion rate under different silicon deposition amounts and the various effects on the initial specific capacity and initial coulombic efficiency of the assembled battery, it is preferable to use a specific surface area of ​​1500-2000 m 2 / g, the average pore diameter is 1.5 to 3.0 nm, and the pore volume is 0.8 to 1.6 cm 3 A porous carbon material with a specific surface area of ​​0.1 wt% / g is used as the substrate. Tests have shown that when a porous carbon material with the above apparent parameters is used as the substrate, the silicon deposition amount in the manufactured silicon carbon composite can be controlled to between 50 and 55 wt% while ensuring a pore structure utilization rate of 98% or more, and the assembled lithium-ion battery exhibits high specific capacity, high initial coulombic efficiency, and high cycle stability.

[0015] In this manufacturing method, the silicon source gas is selected from one or more of monosilane, disilane, dichlorosilane, and trichlorosilane; The source gas is a mixed gas containing a silicon source gas and an inert gas, and the silicon source gas accounts for 70 to 99 vol %, preferably 70 to 85 vol %, of the mixed gas.

[0016] The inert gas is selected from common types in the art, such as nitrogen gas, neon gas, argon gas, krypton gas, xenon gas, and radon gas.

[0017] Preferably, In the first stage, the initial pressure is 10 to 25 Kpa, and the flow rate of the introduced raw material gas is 3 to 10 L / min; In the second stage, the initial pressure is 6 to 8 Kpa, and the flow rate of the introduced raw material gas is 8 to 18 L / min.

[0018] Preferably, In the first step, if the pressure change value in the reactor is 20 to 67% of the initial pressure, proceed to the next step, In the second stage, deposition is completed when the pressure change value in the reactor reaches 15 to 50% of the initial pressure.

[0019] More preferably, In the first step, if the pressure change value in the reactor is 20 to 50% of the initial pressure, the next step is started. In the second stage, deposition is completed when the pressure change value in the reactor reaches 15 to 30% of the initial pressure.

[0020] Tests have shown that with further optimization of the above deposition process parameters, the assembled lithium ion batteries have better electrochemical performance.

[0021] In the present production method, the surface carbon coating is performed by vapor-phase deposition at 400 to 1000°C using a mixed gas composed of a carbon source gas and an inert gas as a raw material gas, The carbon source gas is selected from alkane gases having a decomposition temperature of 400 to 1200° C., and specifically, is selected from common types such as acetylene and ethylene.

[0022] In the mixed gas, the volume of the carbon source gas accounts for 60 to 99 vol%. The flow rate of the mixed gas is 0.1 to 50 L / min, and preferably 0.1 to 10 L / min.

[0023] The temperature of the vapor deposition is 400 to 600°C.

[0024] The present invention further discloses a silicon carbon anode material prepared by the above method, in which the deposited silicon content is 40-60wt% and the specific surface area is <25m 2 / g, pore structure utilization rate >96%, powder resistivity <35 Ω·cm, and gas generation rate after 72 hours <110 ppm. Nano silicon particles are uniformly distributed, with most existing inside the pores of the porous carbon material and not deposited on the surface, resulting in low gas generation at room temperature and superior safety performance.

[0025] Preferably, the silicon content of the silicon-carbon anode material is 50-55 wt% and the specific surface area is <5.0 m 2 / g, the pore structure utilization rate is >98%, the powder resistivity is <5 Ω·cm, and the gas generation value after 72 h is <90 ppm.

[0026] According to the measurement, in the silicon carbon anode material prepared in this example, the mass ratio of the deposited silicon content to the porous carbon content is (0.5~1.4)P all : 1.

[0027] The present invention further discloses a negative electrode plate manufactured using the silicon carbon negative electrode material as an active component, and a lithium battery assembled with the negative electrode plate, which has excellent cycle stability, high reversible specific capacity, and high initial coulombic efficiency.

[0028] The present invention discloses another method for producing a silicon-carbon anode material based on the porous carbon material, the method comprising: Step 1: placing a porous carbon material as a substrate in a deposition furnace under an inert atmosphere and heating the furnace to 400 to 700°C; Step 2: Introduce mixed gas A containing silicon source gas and carbon source gas into the deposition furnace, adjust the pressure valve of the exhaust pipe to maintain the furnace pressure at 5 to 10 kPa during deposition, continue introducing gas, and obtain an intermediate product after vapor deposition; and step 3, in which the temperature is lowered to 200-300°C, a mixed gas B containing an oxygen-containing gas and a carrier gas is introduced into the deposition furnace, and after surface passivation and post-treatment, a silicon carbon anode material is obtained.

[0029] This manufacturing method uses a porous carbon material as a substrate and adopts a method of codepositing nanosilicon particles and nanocarbon particles, where the rich pore structure of the porous carbon material serves as the first confinement to the silicon particles. The silicon-carbon bonds formed between the nanosilicon particles and the nanocarbon particles during the silicon-carbon codeposition (there is no coating structure between the nanosilicon and nanocarbon) further limit the increase in particle size of the silicon particles during thermal deposition, resulting in a second confinement to the silicon particles. Finally, an oxide layer is deposited at low temperature to passivate the surface, preventing direct contact between the anode material and the electrolyte, improving the stability of the material and preventing the formation of silicon carbide by-product, thereby ensuring the capacity and initial coulombic efficiency of the anode material.

[0030] The first confinement in the present invention is due to the pore structure of the porous carbon material, and the selection of the pore diameter and pore volume (the effect of the specific surface area is clearly weaker than that of the other two parameters) significantly affects the deposition of Si and C, which further affects the size of the generated silicon crystal grains, and ultimately significantly affects the electrochemical performance of the assembled lithium battery.

[0031] In step 1, The porous carbon material has a pore size of 3 to 10 nm and a pore volume of 0.5 to 1.2 cm 3 / g, and the specific surface area is 500 to 2000 m 2 / g, and tests have shown that when a porous carbon material having the above-mentioned preferred parameters is employed, a battery assembled with the produced silicon carbon anode material has excellent electrochemical performance.

[0032] More preferably, the pore diameter of the porous carbon material is 5 to 10 nm and the pore volume is 0.5 to 0.8 cm 3 / g, and the specific surface area is 1000 to 1800 m 2 / g. Tests have shown that when a porous carbon material having the above-mentioned preferred parameters is used, a lithium battery assembled with the produced carbon anode material can more easily control the change in the expansion rate of the electrode plate within a narrower range, and furthermore, can achieve better cycle stability.

[0033] Preferably, the pore diameter of the porous carbon material is 5 nm and the pore volume is 0.8 cm 3 / g, and the specific surface area is 1800m 2 / g. Tests have shown that when a porous carbon material having these parameters is used, a battery assembled with the produced negative electrode material exhibits high capacity, high initial coulombic efficiency, and excellent cycle stability.

[0034] Preferably, the porous carbon material is produced by the following method, specifically: Step (A) of placing asphalt in a reactor, evacuating the reactor, and then raising the temperature to the softening point of the asphalt; Step (B) of introducing a gas into a molecular sieve to form a nanogas, and then introducing the nanogas into a reactor to form nanobubbles in the softened asphalt, and controlling the pressure inside the reactor to reach a predetermined level; and (C) continuing to heat the mixture to a temperature 50°C higher than the softening point of the asphalt, maintaining the temperature for a certain period of time, and then cooling the mixture to room temperature to obtain a porous material, which is then subjected to a carbonization treatment to obtain the porous carbon material.

[0035] The method for producing a porous carbon material disclosed in the invention uses a molecular sieve to generate nanogas, which then forms a pore-rich structure in the softened asphalt, with a uniform pore size and resistance to collapse. Furthermore, by controlling the pore size of the molecular sieve in step (B), the flow rate of the nanogas, and the pressure inside the reactor, the pore volume, pore size, and specific surface area of ​​the produced porous carbon material can be adjusted.

[0036] In step (A), the asphalt used in the present invention includes types such as high temperature asphalt, medium temperature asphalt, low temperature asphalt, etc. The amount of asphalt charged occupies 10 to 90% of the reactor volume.

[0037] In step (B), The gas is selected from one or more of nitrogen, carbon monoxide, carbon dioxide, water vapor, and an inert gas, and the inert gas is selected from helium gas, neon gas, argon gas, and the like.

[0038] The pore size of the molecular sieve is 5 to 30 nm.

[0039] The flow rate of the nanogas is 12 to 22 L / min, the introduction time is 30 to 50 min, and the pressure inside the reactor is controlled to 5 to 12 MPa; preferably, the flow rate of the nanogas is 15 to 18 L / min, the introduction time is 30 to 40 min, and the pressure inside the reactor is controlled to 7 to 9 MPa; In step (C), The temperature is raised to 60 to 100°C higher than the softening point of the asphalt, and the temperature is maintained for 1 to 10 hours. The carbonization treatment is carried out in an inert atmosphere at a carbonization temperature of 650 to 950°C.

[0040] Tests have shown that, compared to commercially available porous carbon materials, the porous carbon materials manufactured using the special process disclosed in the present invention have more uniform pore size and narrower pore size distribution, even when they achieve the same or equivalent pore size, pore volume, and specific surface area as commercially available products. Comparative measurements have shown that lithium batteries assembled with the porous carbon material manufactured using the special process as a base material and the final negative electrode material have better cycle stability. This may be because the more uniform pore size better ensures the uniformity of silicon particle size in the manufactured silicon carbon negative electrode material.

[0041] In step 2, the silicon source gas is selected from one or more of monosilane, disilane, dichlorosilane, and trichlorosilane; The carbon source gas is selected from alkane gases that decompose at 400 to 800°C, In the mixed gas A, the volume of the silicon source gas is 1 to 99%, and the volume of the carbon source gas is 1 to 99%; The flow rate of the mixed gas A is 0.1 to 50 L / min, The vapor deposition time is 2 to 16 hours, By adjusting the volume ratio of the silicon source gas to the carbon source gas and the vapor deposition time in step 2, it is possible to control the silicon content in the final silicon-carbon anode material, and more importantly, the size of the silicon crystal grains in the final silicon-carbon anode material. Both of these changes directly affect the electrochemical performance of the final assembled lithium battery. Further texts have shown that if the ratio of the two gases in mixed gas A is not appropriate, it is difficult to achieve both a high and appropriate silicon content and a small silicon crystal grain size, resulting in poor electrochemical performance of the assembled lithium battery. Further testing has shown that without codeposition, i.e., when only silicon source gas is introduced without carbon source gas, the cycling stability of lithium batteries assembled with the anode material produced using the produced anode material is significantly worse than that produced by codeposition, and the calculated silicon crystal grain size in the anode material is 5.44 nm, significantly larger than that produced by codeposition.

[0042] Preferably, In the mixed gas A, the volume of the silicon source gas is 60-90%, and the volume of the carbon source gas is 10-40%; The flow rate of the mixed gas A is 5 to 20 L / min, The vapor deposition time is 6 to 12 hours; More preferably, In the mixed gas A, the volume of the silicon source gas accounts for 60-70%, the volume of the carbon source gas accounts for 30-40%, and the vapor deposition time is 6-9 hours. Tests have shown that when the above preferred parameters are adopted, lithium batteries assembled with the produced negative electrode material can more easily control the change in the expansion rate of the electrode plate within a narrower range and also achieve better cycle stability.

[0043] More preferably, the volume ratio of the carbon source gas to the silicon source gas in the mixed gas A is 70:30. Tests have shown that a battery assembled with a negative electrode material manufactured using these more preferred parameters exhibits high capacity, high initial coulombic efficiency, and excellent cycle stability.

[0044] During the deposition process, the exhaust pipe is immersed in water while still connected to the water tank, and the pressure inside the furnace is stably maintained at 5 to 10 KPa by introducing the mixed gas into the exhaust pipe to form a liquid seal with water.

[0045] Preferably, the pressure inside the furnace is constantly maintained at 5 to 8 KPa during the deposition process, and more preferably, 8 KPa.

[0046] With the continuous optimization of the above parameters, the electrochemical performance of the lithium battery assembled with the prepared negative electrode material will be further optimized.

[0047] In step 3, the oxygen-containing gas is selected from one or more of oxygen, carbon monoxide, carbon dioxide, ethanol gas, and isopropanol gas; the carrier gas is selected from nitrogen gas and / or an inert gas; In the mixed gas B, the volume ratio of the oxygen-containing gas is 1 to 10%, and the volume ratio of the carrier gas is 90 to 99%, the flow rate of the mixed gas B is 0.1 to 50 L / min; The surface passivation time is 0.5 to 5.0 hours.

[0048] Tests have shown that if the content of the oxide layer formed by surface passivation is too low, it does not provide sufficient protection for the negative electrode material, resulting in poor long-term cycle stability; however, if the content of the oxide layer formed by surface passivation is too high, the first coulomb efficiency will be significantly reduced.

[0049] Preferably, The flow rate of mixed gas B is 10 to 30 L / min, and the surface passivation time is 1 to 3 hours.

[0050] More preferably, the flow rate of mixed gas B is 20 L / min and the surface passivation time is 1.5 to 2.0 hours.

[0051] The present invention further discloses a silicon carbon negative electrode material produced by the above method, a negative electrode plate produced using the negative electrode material as an active component, and a lithium battery assembled with the negative electrode plate.

[0052] According to calculations, the silicon crystal grain size in this silicon carbon anode material is less than 3.0 nm. The lithium battery assembled with this anode material has a small change rate of the plate expansion rate after 100 cycles relative to the expansion rate at full charge at the first cycle, which can be controlled to be at most 10% or less, and after 500 cycles, the capacity retention rate can reach up to 85%, which has excellent cycle stability, high reversible specific capacity and high initial coulombic efficiency.

[0053] The present invention discloses a prelithiated silicon-carbon anode material produced based on the porous carbon material, which comprises a porous carbon material substrate, a thin layer of metallic lithium coating the outer surface and inner wall of the porous carbon material substrate, nanosilicon particles deposited on the thin layer of metallic lithium, and an outermost carbon coating layer.

[0054] The present invention discloses a prelithiated silicon carbon anode material, in which a thin layer of metallic lithium with an appropriate content (thickness) is coated (or deposited) on the surface of a porous carbon material substrate, which isolates the porous carbon material substrate from the subsequently deposited nanosilicon, fully exerting the effect of lithium replenishment, while preventing the nanosilicon and the porous carbon from directly contacting each other and reacting at high temperatures, ensuring a high reversible specific capacity and a high initial coulombic efficiency. The presence of the thin layer of metallic lithium further limits the particle size of the deposited nanosilicon particles, which can improve the cycle stability of the final anode material.

[0055] Tests have shown that if the content (thickness) of the metallic lithium thin layer is too large, it will block the pore structure of some of the porous carbon materials, affecting the amount of nanosilicon deposition, thereby reducing both the reversible specific capacity and cycle stability of lithium-ion batteries assembled with the resulting anode material; if the content (thickness) of the metallic lithium thin layer is too small, it will reduce its limiting effect on the particle size of the subsequently deposited nanosilicon particles, thereby reducing the cycle stability of lithium-ion batteries assembled with the resulting anode material. Tests have also shown that if the vapor deposition on the surface of a porous carbon material substrate results in discrete nanoparticles or a coating layer assembled with discrete nanoparticles rather than a continuous thin layer, the cycle stability of lithium-ion batteries assembled with the resulting anode material will be significantly reduced and will lose their practical value.

[0056] Preferably, the porous carbon material substrate has an average pore diameter of 1.5 to 10.0 nm and a pore volume of 0.5 to 1.5 cm. 3 / g, and the specific surface area is 300 to 3000 m 2 / g, the particle size concentration SPAN value of the porous carbon material substrate is <1.5, D50 is 4 to 10 μm, and more preferably the average pore diameter is 2.0 to 5.0 nm and the pore volume is 0.7 to 1.2 cm 3 / g, and the specific surface area is 1200-1600m 2 / g.

[0057] Preferably, the porous carbon material has through-holes to facilitate the absorption and desorption of lithium ions.

[0058] Preferably, Based on the total mass of the prelithiated silicon carbon anode material, the content of the metallic lithium thin layer is 1-10 wt%, the content of silicon is 30-90 wt%, the content of the carbon coating layer is 1-10 wt%, and the remainder is the porous carbon material substrate; The silicon crystalline domains of the nanosilicon particles are ≦5 nm.

[0059] More preferably, The metallic lithium thin layer contains 3.0 to 5.5 wt % and silicon contains 40 to 60 wt %.

[0060] Tests have shown that when the above content is used, the reversible specific capacity and capacity retention rate of the lithium ion battery assembled with the prelithiated silicon carbon anode material thus prepared are both higher.

[0061] The present invention further discloses a method for preparing the prelithiated silicon carbon anode material, the method comprising: Step (1) of placing a porous carbon material substrate in a deposition furnace under an inert atmosphere and raising the temperature to 200 to 800°C; (2) introducing a lithium source gas into a deposition furnace and depositing it on the surface of the porous carbon substrate to form a thin layer of metallic lithium; Step (3) after the lithium deposition is completed, adjust the temperature of the deposition furnace to 400 to 800°C, introduce a silicon source gas, and deposit silicon, so that the amount of deposited nanosilicon occupies 40 to 90% of the pore volume of the porous carbon substrate; After the silicon deposition is completed, the temperature of the deposition furnace is adjusted to 400 to 1000°C, a carbon source gas is introduced, and a carbon coating process is performed to obtain a prelithiated silicon carbon negative electrode material (4).

[0062] In step (1), The inert atmosphere is selected from one or more of a nitrogen gas atmosphere, a neon gas atmosphere, an argon gas atmosphere, a krypton gas atmosphere, a xenon gas atmosphere, and a radon gas atmosphere.

[0063] Preferably, the temperature of the deposition furnace is increased to 300 to 600°C.

[0064] In step (2), The lithium source gas is obtained by heating and gasifying metallic lithium or lithium hydride as a raw material, The flow rate of the lithium source gas is 5 to 50 L / min, and the specific introduction time is adaptively adjusted according to the flow rate and the content of the metallic lithium thin layer that needs to be achieved.

[0065] Preferably, the flow rate of the lithium source gas is 10 to 50 L / min.

[0066] In step (3), the silicon source gas is selected from one or more of monosilane, disilane, dichlorosilane, and trichlorosilane; The flow rate of the silicon source gas is 0.1 to 50 L / min, and the specific introduction time is adaptively adjusted according to the flow rate and the silicon content that needs to be achieved.

[0067] Preferably, the flow rate of the silicon source gas is 10 to 50 L / min.

[0068] Preferably, the temperature of the deposition furnace is adjusted to 400 to 600° C., and the amount of deposited nanosilicon is controlled so that it occupies 60 to 80% of the pore volume of the porous carbon substrate.

[0069] In step (4), The carbon source gas is selected from alkane gases that can be decomposed at 400 to 800° C., and specific examples thereof include ethylene, propylene, and acetylene.

[0070] Preferably, the flow rate of the carbon source gas is 0.1 to 50 L / min.

[0071] Considering the influence of the carbon coating temperature on the lithium-silicon alloying reaction, the temperature of the deposition furnace is preferably adjusted to 400 to 600°C.

[0072] The present invention further discloses a negative electrode plate manufactured using the prelithiated silicon carbon negative electrode material as the active component, and a lithium battery assembled with the negative electrode plate, which has excellent cycle stability, high reversible specific capacity, and high initial coulombic efficiency.

[0073] The present invention has the following advantageous effects compared to the prior art.

[0074] The porous carbon material disclosed in the present invention has a high pore size concentration, which can promote lithium ion diffusion, allowing lithium ions to diffuse and move more quickly and uniformly during charge and discharge, which not only improves the charge and discharge efficiency of the electrode but also reduces polarization, further improving the energy density and cycle stability of the battery and helping to improve the specific capacity of the electrode. Furthermore, porous carbon materials with a high pore size concentration are stable and less likely to deform or break, which can ensure the stability of silicon carbon anode materials manufactured using them during the charge and discharge processes and improve the cycle stability of anode materials in application. The optimized pore size and distribution can better accommodate silicon elements, improving the specific capacity of the electrode, reducing polarization during the charge and discharge processes and improving energy density. The concentrated pore structure effectively ensures the uniform deposition of nanosilicon, avoiding uneven silicon deposition and distribution due to different pore sizes and avoiding stress concentration caused by volume expansion during the silicon lithium absorption process.

[0075] The method for manufacturing silicon-carbon anode materials disclosed in the present invention employs different deposition environments for different sized pore structures in porous carbon materials, thereby ensuring the transmission and diffusion of gas molecules within the pore structures, improving the utilization rate of the pore structure, especially the micropores (<2 nm), reducing the clogging of passages caused by the aggregation of nanosilicon inside the porous carbon, achieving a uniform dispersion of nanosilicon particles within the porous substrate, reducing the concentration of nanosilicon on the surface of the porous carbon, fully utilizing the pore structure's confining effect on the volumetric expansion of nanosilicon during lithium desorption and absorption, achieving a porous structure with uniform and concentrated pore sizes, avoiding the destruction of the porous substrate structure caused by stress concentration due to aggregation, and significantly improving the cycle stability of the final anode material. The silicon carbon anode material prepared by the present invention has a pore structure utilization rate of >98% and no obvious gas generation. The lithium ion battery assembled using it has excellent cycle stability, with a capacity retention rate of over 90% after 100 cycles, and can reach a maximum of 96%, and a capacity retention rate of over 85% after 500 cycles, and can reach a maximum of 90%. It also has low powder resistance, high reversible specific capacity, and high initial coulombic efficiency.

[0076] The present invention discloses a co-deposition method for fabricating silicon-carbon anode materials. Using a porous carbon material as a substrate, silicon particles and carbon particles are deposited within the pores of the porous carbon material. The pore structure and carbon particles create a double confinement, limiting the particle size of the silicon during bulk deposition, preventing silicon particles from fusing together and enlarging their size, and maximizing the volumetric expansion of the silicon. Finally, an oxidized passivation layer is applied as an outer layer, improving material stability and preventing the formation of by-products during the high-temperature carbon coating process. The fabrication process is simple and controllable, making it suitable for industrial production. Lithium-ion batteries fabricated using the silicon-carbon anode materials fabricated by the present invention exhibit a small change in the plate expansion rate after 100 cycles relative to the expansion rate at the first full charge cycle, exhibiting excellent cycle stability, high reversible specific capacity, and high initial coulombic efficiency.

[0077] The prelithiated silicon-carbon anode material disclosed in the present invention first forms a thin layer of metallic lithium on the outer surface of the porous carbon substrate and the inner surface of the pores as a passivation layer, and then deposits pure silicon. This fully utilizes the lithium replenishment effect while effectively preventing direct contact between the carbon substrate and the deposited silicon and limiting the size of the nanosilicon particles. By precisely controlling the content (thickness) of the thin metallic lithium layer through chemical vapor deposition, the degree of nanosilicon alloying can be effectively controlled, avoiding the embrittlement of the material structure and the impact on cycle stability due to high alloying. The manufacturing process is simple and controllable, making it suitable for industrial production. The lithium ion battery assembled with the silicon carbon anode material prepared in accordance with the present invention has excellent electrochemical performance, with a reversible specific capacity of >1800mAh / g, an initial coulombic efficiency of over 98% and a maximum of 105%, a capacity retention rate after 100 cycles of ≥85% and a maximum of 92%, and a capacity retention rate after 500 cycles of ≥78% and a maximum of 87%, combining high initial coulombic efficiency, reversible specific capacity and high cycle stability. [Brief explanation of the drawings]

[0078] [Figure 1] FIG. 2 is a diagram showing the pore size distribution of the porous carbon material employed in Example 1. [Figure 2] FIG. 10 is a diagram showing the pore size distribution of a porous carbon material employed in Comparative Example 3. [Figure 3] FIG. 1 shows Raman spectra of silicon carbon anode materials produced in Example 1 and Comparative Example 13, respectively. [Figure 4] FIG. 1 shows the pore size distribution of the asphalt-based porous carbon material produced in Example 8. [Figure 5] FIG. 5 is an enlarged view of the region surrounded by a box in the pore size distribution diagram shown in FIG. [Figure 6] FIG. 10 shows the XPS of the silicon carbon anode material prepared in Example 8. [Figure 7]FIG. 10 is a Raman spectrum of the silicon carbon negative electrode material produced in Example 8. [Figure 8] FIG. 8 is an enlarged view of the region surrounded by a box in the Raman spectrum shown in FIG. [Figure 9] FIG. 10 is a diagram showing the pore size distribution of a commercially available porous carbon material employed in Example 9. [Figure 10] FIG. 10 is an enlarged view of the region surrounded by a box in the pore size distribution diagram shown in FIG. [Figure 11] FIG. 10 is a Raman spectrum of the silicon carbon negative electrode material prepared in Comparative Example 18. [Figure 12] FIG. 12 is an enlarged view of the region surrounded by a box in the Raman spectrum shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0079] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0080] Example 1 (1) Under an argon gas atmosphere, 100 g of porous carbon material was used as a substrate (D50 = 6 μm, span value < 1.5) and placed in a thermal deposition furnace at a temperature of 500 °C. The specific surface area of ​​the porous carbon material was 1800 m 2 / g, the average pore diameter is 2 nm, and the pore volume is 1.2 cm 3 / g, Fig. 1 shows the pore size distribution of the porous carbon material used in this example. Measurements showed that the pore volume distribution of the porous carbon material was 10.64% ultramicropores (<1 nm), 11.71% micropores (1-2 nm), 62.77% mesopores (2-10 nm), 13.32% mesopores (10-50 nm), and 1.56% macropores (>50 nm). According to the following formula for calculating the pore size concentration, the pore size concentration of the porous carbon material used in this example was 0.092. JPEG2026505513000003.jpg46169P:Pore volume; P all : total pore volume; d max* : Maximum pore size when P>0.005; d min* :Minimum pore size when P>0.005.

[0081] (2) First stage: A mixed gas consisting of 80 vol% monosilane and 20 vol% argon gas was introduced into the thermal deposition furnace at a flow rate of 5 L / min, and the furnace pressure was maintained at 15 KPa. Silicon particles were continuously nucleated and deposited inside the pores of the porous carbon, and the gas was continued to be introduced until the furnace pressure changed. Second stage: When the pressure inside the furnace changes to 8 Kpa, adjust the flow rate of the mixed gas to 12 L / min, adjust the pressure inside the furnace to 6 Kpa, continue introducing gas, and when the pressure inside the furnace rises to 8 Kpa, deposition is completed. (3) After silicon deposition is completed, a mixed gas consisting of 70 vol% acetylene and 30 vol% argon gas is introduced at a flow rate of 1 L / min to perform high-temperature carbon coating. The gas is continuously introduced for 2 hours, so that the mass of the carbon coating layer accounts for 5 wt% of the mass of the final silicon-carbon anode material. The material is then cooled to room temperature, and the silicon-carbon anode material is obtained after being crushed, sieved, demagnetized, and other processes.

[0082] In this example, a silicon-carbon anode material is produced and obtained, in which the content of deposited silicon is 53.7 wt%, the content of porous carbon is 41.3 wt%, and the content of surface carbon coating layer is 5 wt%.

[0083] The specific surface area and pore volume data of the finished silicon carbon anode material prepared in this example are shown in Table 1 below. According to the following calculation formula, the pore structure utilization data of the finished silicon carbon anode material prepared in this example was calculated and shown in Table 1. JPEG2026505513000004.jpg20157P1: The pore volume of the raw porous carbon material; P2: the pore volume of the finished silicon carbon anode material.

[0084] The room temperature gas generation performance of the silicon carbon anode material manufactured in this example was measured. Specifically, Add 300mL of deionized water into a bottle with good sealing properties, add 1g of the silicon carbon anode material prepared in this embodiment, close the bottle cap to prevent leakage, shake evenly and leave for 10 minutes, immediately remove the bottle cap, insert a gas concentration detector into the bottle, read the value displayed by the instrument, this is the initial gas generation value of the silicon carbon anode material, open the bottle and wait for a while, insert the gas detector into the bottle, when the value displayed becomes 0, close the bottle cap again, shake evenly in the same way after 24 hours, repeat the above measurement operation again, repeat the 24-hour measurement operation at 48 hours and 72 hours, and record the gas generation values ​​at the initial, 24 hours, 48 ​​hours and 72 hours, the measurement results are shown in Table 2 below.

[0085] Example 2 (1) Under an argon gas atmosphere, 100 g of porous carbon material was used as a substrate (D50 = 6 μm, span value < 1.5) and 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, the average pore diameter was 1.5 nm, and the pore volume was 1.6 cm 3 / g, and the pore size concentration is 0.076, (2) First stage: A mixed gas consisting of 80 vol% monosilane and 20 vol% argon gas was introduced into the thermal deposition furnace at a flow rate of 10 L / min, and the furnace pressure was maintained at 20 Kpa. Silicon particles were continuously nucleated and deposited inside the pores of the porous carbon, and the gas was continued to be introduced until the furnace pressure changed. Second stage: When the furnace pressure changes to 12 Kpa, the flow rate of the mixed gas is adjusted to 18 L / min, the furnace pressure is adjusted to 6 Kpa, and the gas is continued to be introduced. When the furnace pressure rises to 8 Kpa, the deposition is completed. Step (3) is completely the same as in the first embodiment.

[0086] Example 3 (1) Under an argon gas atmosphere, 100 g of porous carbon material was used as a substrate (D50 = 6 μm, span value < 1.5) and 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, the average pore diameter is 3 nm, and the pore volume is 0.8 cm 3 / g, and the pore size concentration is 0.094, (2) First stage: A mixed gas consisting of 80 vol% monosilane and 20 vol% argon gas was introduced into the thermal deposition furnace at a flow rate of 3 L / min, and the furnace pressure was maintained at 12 KPa. Silicon particles were continuously nucleated and deposited inside the pores of the porous carbon, and the gas was continued to be introduced until the furnace pressure changed. Second stage: When the pressure inside the furnace changes to 7 Kpa, the flow rate of the mixed gas is adjusted to 8 L / min and the gas continues to be introduced. When the pressure inside the furnace rises to 9 Kpa, the deposition is completed. Step (3) is completely the same as in the first embodiment.

[0087] Comparative Example 1 (1) Under an argon gas atmosphere, 100 g of porous carbon material was used as a substrate (D50 = 6 μm, span value < 1.5) and 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, the average pore diameter was 1 nm, and the pore volume was 2.0 cm 3 / g, and the pore size concentration is 0.087, (2) First stage: A mixed gas consisting of 80 vol% monosilane and 20 vol% argon gas was introduced into the thermal deposition furnace at a flow rate of 5 L / min, and the furnace pressure was maintained at 25 Kpa. Silicon particles were continuously nucleated and deposited inside the pores of the porous carbon, forming silicon particles. The gas was continued to be introduced until the furnace pressure changed. Second stage: When the furnace pressure changes to 15 Kpa, the flow rate of the mixed gas is adjusted to 12 L / min, the furnace pressure is adjusted to 6 Kpa, and the gas is continued to be introduced. When the furnace pressure rises to 8 Kpa, the deposition is completed. Step (3) is completely the same as in the first embodiment.

[0088] Comparative Example 2 (1) Under an argon gas atmosphere, 100 g of porous carbon material was used as a substrate (D50 = 6 μm, span value < 1.5) and 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, the average pore diameter is 10 nm, and the pore volume is 0.6 cm 3 / g, and the pore size concentration is 0.095, (2) First stage: A mixed gas consisting of 80 vol% monosilane and 20 vol% argon gas was introduced into the thermal deposition furnace at a flow rate of 5 L / min, and the furnace pressure was maintained at 10 KPa. Silicon particles were continuously nucleated and deposited inside the pores of the porous carbon, and the gas was continued to be introduced until the furnace pressure changed. Second stage: When the pressure inside the furnace changes to 7 Kpa, the flow rate of the mixed gas is adjusted to 12 L / min and the gas continues to be introduced. When the pressure inside the furnace rises to 10 Kpa, the deposition is completed. Step (3) is completely the same as in the first embodiment.

[0089] Comparative Example 3 The manufacturing process was basically the same as in Example 1, except that the pore size concentration of the porous carbon material selected in step (1) was 0.025 and the specific surface area was 1852 m 2 / g, the average pore diameter is 1.9 nm, and the pore volume is 1.2 cm 3 / g. Fig. 2 is a diagram showing the pore size distribution of the porous carbon material employed in this comparative example.

[0090] Comparative Example 4 Step (1) is the same as in Example 1, (2) A mixed gas consisting of 80 vol% monosilane and 20 vol% argon gas was introduced into the thermal deposition furnace at a flow rate of 10 L / min, the pressure inside the furnace was maintained at 8 KPa, and the gas was continuously introduced for 10 h. Step (3) is the same as in the first embodiment.

[0091] Comparative Example 5 Step (1) is the same as in Example 1, (2) First stage: A mixed gas consisting of 80 vol% monosilane and 20 vol% argon gas was introduced into the thermal deposition furnace at a flow rate of 12 L / min, the pressure inside the furnace was maintained at 6 Kpa, and silicon particles were continuously nucleated and deposited inside the pores of the porous carbon. The gas was continuously introduced for 7 h. Second stage: The flow rate of the mixed gas was adjusted to 5 L / min, the pressure inside the furnace was adjusted to 12 Kpa, and the gas was introduced for 3 hours until the deposition was completed. Step (3) is the same as in the first embodiment.

[0092] Comparative Example 6 The manufacturing process was basically the same as in Example 1, with the only difference being that the flow rate of the mixed gas in the first stage in step (2) was changed to 12 L / min.

[0093] Comparative Example 7 The manufacturing process was basically the same as in Example 1, with the only difference being that the flow rate of the mixed gas in the second stage in step (2) was changed to 3 L / min.

[0094] Comparative Examples 8-9 The manufacturing process was basically the same as in Example 1, with the only difference being that the furnace pressure in the first stage of step (2) was changed to 32 Kpa (Comparative Example 8) and 5 Kpa (Comparative Example 9), respectively.

[0095] Comparative Example 10 The manufacturing process is basically the same as in Example 1, with the only difference being that the furnace pressure in the second stage of step (2) is changed to 12 Kpa.

[0096] Example 4 The manufacturing process is basically the same as in Example 1, with the only difference being that in the second stage of step (2), when the furnace pressure changes to 12 Kpa, the flow rate of the mixed gas is adjusted to 12 L / min, the furnace pressure is adjusted to 6 Kpa, the gas continues to be introduced, and when the furnace pressure rises to 8 Kpa, deposition is completed.

[0097] Example 5 The manufacturing process is basically the same as in Example 1, with the only difference being that in the second stage of step (2), when the furnace pressure changes to 5 Kpa, the flow rate of the mixed gas is adjusted to 12 L / min, the furnace pressure is adjusted to 6 Kpa, the gas continues to be introduced, and when the furnace pressure rises to 8 Kpa, deposition is completed.

[0098] Comparative Example 11 The manufacturing process is basically the same as in Example 1, with the only difference being that in the second stage of step (2), when the furnace pressure changes to 14 Kpa, the flow rate of the mixed gas is adjusted to 12 L / min, the furnace pressure is adjusted to 6 Kpa, the gas continues to be introduced, and when the furnace pressure rises to 8 Kpa, deposition is completed.

[0099] Comparative Example 12 The manufacturing process is basically the same as in Example 1, with the only difference being that in the second stage of step (2), when the furnace pressure changes to 3 Kpa, the flow rate of the mixed gas is adjusted to 12 L / min, the furnace pressure is adjusted to 6 Kpa, the gas continues to be introduced, and when the furnace pressure rises to 8 Kpa, deposition is completed.

[0100] Example 6 The manufacturing process is basically the same as in Example 1, with the only difference being that in the second stage of step (2), when the furnace pressure changes to 8 Kpa, the flow rate of the mixed gas is adjusted to 12 L / min, the furnace pressure is adjusted to 6 Kpa, the gas continues to be introduced, and when the furnace pressure rises to 7 Kpa, deposition is completed.

[0101] Example 7 The manufacturing process is basically the same as in Example 1, with the only difference being that in the second stage of step (2), when the furnace pressure changes to 8 Kpa, the flow rate of the mixed gas is adjusted to 12 L / min, the furnace pressure is adjusted to 6 Kpa, the gas continues to be introduced, and when the furnace pressure rises to 9 Kpa, deposition is completed.

[0102] Comparative Example 13 The manufacturing process is basically the same as in Example 1, with the only difference being that in the second stage of step (2), when the furnace pressure changes to 8 Kpa, the flow rate of the mixed gas is adjusted to 12 L / min, the furnace pressure is adjusted to 6 Kpa, the gas continues to be introduced, and when the furnace pressure rises to 11 Kpa, deposition is completed.

[0103] FIG. 3 shows the Raman spectra of the silicon carbon anode materials produced in Example 1 and Comparative Example 13. -1 Regarding the characteristic silicon peak at 480 cm, the intensity of the characteristic peak becomes more pronounced due to the deposition and concentration of silicon particles, and the higher the deposition and concentration of silicon particles, the greater the intensity of the silicon peak. Based on this, when comparing the Raman spectrum curves of Example 1 and Comparative Example 13, the silicon concentration phenomenon appears in the Raman spectrum curve of Comparative Example 13, and the silicon concentration phenomenon appears at 480 cm. -1 It can be clearly seen that the intensity of the characteristic peak of silicon at 1000 kJ / cm2 increases significantly, which indicates that if the process parameters are not properly adjusted in the silicon deposition process, silicon particles will be seriously deposited, resulting in silicon concentration on the surface of the porous carbon material.

[0104] Test Example To verify the accuracy of the conclusion that in the staged deposition disclosed above, the first stage is used to deposit the microporous portion of the porous carbon material and the second stage is used to deposit the mesoporous portion of the porous carbon material, the following verification is performed: The manufacturing process is basically the same as that of Example 1, except that in step (2): First stage: A mixed gas consisting of 80 vol% monosilane and 20 vol% argon gas was introduced into the thermal deposition furnace at a flow rate of 5 L / min, and the pressure inside the furnace was maintained at 15 Kpa. Second stage: When the furnace pressure changes to 8 Kpa, a mixed gas consisting of 80 vol% monosilane and 20 vol% argon gas is introduced into the thermal deposition furnace at a flow rate of 12 L / min, the furnace pressure is adjusted to 6 Kpa, and the gas continues to be introduced. When the furnace pressure rises to 8 Kpa, the deposition is completed.

[0105] According to the measurement, the silicon carbon anode material is finally produced and obtained, with the deposited silicon content being 12.7 wt%, the deposited carbon content being 42.1 wt%, the porous carbon content being 40.2 wt%, and the surface carbon coating layer content being 5 wt%.

[0106] As can be seen from the parameters of the porous carbon material of Example 1, the ratio of its mesopore portion (2-50 nm) to its micropore portion (≦2 nm) is about 3.404, and the mass ratio of the deposited carbon to the deposited silicon obtained by the above measurement is about 3.314, which are equivalent values. This shows that the basis for determining the stage division sections of the stage division process of the present invention is compatible with the pore structure distribution of actual porous carbon.

[0107] Example 8 (1) In an argon gas atmosphere, 100 g of the asphalt-based porous carbon material as the substrate was placed in a deposition furnace at a temperature of 500°C. The asphalt-based porous carbon material used in this example is produced and obtained by the following method.

[0108] (A) The hot asphalt powder, which occupies 60% of the reactor volume, is placed in the reactor, and after vacuuming, the procedure is set and the temperature is raised to 120°C. The hot asphalt powder gradually softens completely. (B) Nitrogen gas is introduced into a molecular sieve with a pore size of 10 nm to form nanogas, which is then introduced into the reactor. The flow rate of the introduced nanogas is 17 L / min, and the introduction time is 35 minutes. Nanobubbles are formed inside the softened asphalt, and the pressure inside the reactor is controlled to 8 MPa. (C) Set the procedure in the reactor, heat it to 200 ° C, keep it warm for 4 hours, cool it to room temperature after keeping it warm, take it out, and obtain a block-shaped porous asphalt material. (D) The block-shaped porous asphalt material is crushed and the particle size of the crushed material is controlled to be 2 to 10 μm. The crushed material is placed in a carbonization furnace, heated to 850°C in a nitrogen gas atmosphere, and reacted for 2 hours until completely carbonized. The material is then cooled to room temperature and removed to obtain an asphalt-based porous carbon material.

[0109] According to the BET test, the specific surface area of ​​the asphalt-based porous carbon material produced in this example is 1800 m 2 / g, the average pore diameter was 4.8 nm, and the pore volume was 0.8 cm 3 / g.

[0110] Fig. 4 is a diagram showing the pore size distribution of the porous carbon material produced in this example, and Fig. 5 is an enlarged view of the area surrounded by a frame in the pore size distribution diagram shown in Fig. 4. From the diagram, it can be seen that the pore size concentration of the asphalt-based porous carbon material produced in this example is 0.107, the pore sizes are concentrated in the range of 3 to 7 nm, the pore sizes are uniform, and the pore size distribution is narrow.

[0111] (2) A mixed gas consisting of 70 vol% monosilane and 30 vol% acetylene was introduced into the deposition furnace at a flow rate of 10 L / min. The pressure inside the furnace was maintained at 8 KPa by adjusting the pressure valve of the exhaust pipe. The gas was continuously introduced for 9 hours, allowing nucleation and deposition to occur continuously inside the pores of the porous carbon, forming silicon particles and carbon particles. (3) After the deposition of silicon and carbon is completed, the deposition furnace is cooled to 300°C, and a mixed gas consisting of 1 vol% CO and 99 vol% argon gas is introduced at a flow rate of 20 L / min. The gas is continuously introduced for 1.5 hours to perform passivation treatment. (4) After passivation is complete, the temperature is lowered to room temperature, and the material is crushed, sieved, demagnetized, and other processes to obtain the silicon carbon anode material.

[0112] FIG. 6 shows the XPS data of the product produced in this example. From the figure, it can be seen that the silicon-carbon anode material produced in this example contains obvious silicon-carbon bonds, which originate from the bonds between silicon particles and carbon particles formed by thermal deposition in step (2). The presence of silicon-carbon bonds effectively limits the particle size growth of silicon particles during the deposition process.

[0113] FIG. 7 shows the Raman spectrum of the product produced in this example, and FIG. 8 is an enlarged view of the framed area in FIG. 7. It can be seen from the figure that the silicon carbon anode material produced in this example has a Raman spectrum of 480 cm -1 It was found that a clear absorption peak was observed around 1000 .mu.m, proving that the deposited silicon was amorphous silicon.

[0114] Because amorphous materials lack long-range order, their structure cannot be analyzed by conventional methods such as X-ray diffraction (XRD). However, the size of silicon crystal grains (111) can be calculated using the Debye-Scherrer equation, as follows: D=Kλ / (β cos θ) K is the Scherrer constant, K=0.89 when β is the full width at half maximum of the diffraction peak, and K=1 when β is the integral width of the diffraction peak; D is the average thickness of the crystal grains perpendicular to the crystal plane (grain size, nm), β is the full width at half maximum of the diffraction peak of the measured sample (dual line calibration and instrument coefficient calibration are required), which must be converted to radians (rad) during calculation, i.e., (β / 180) × 3.14; θ is the Bragg diffraction angle in degrees; λ is the wavelength of X-rays, which is 0.154056 nm, From this, the size of the silicon crystal grains in the silicon carbon negative electrode material obtained in Example 1 is calculated: D=Kλ / (β cos θ) =(0.89×0.154056) / ((3.406 / 180)×3.14×cos(0.4794)) =2.6008nm According to the measurement, the silicon content of the silicon-carbon anode material finally produced in this example is 53 wt%, the deposited carbon content is 10.5 wt%, the porous carbon content is 35 wt%, and the surface oxide layer content is 1.5 wt%.

[0115] Example 9 The manufacturing process was basically the same as in Example 8, except that in step (1), a commercially available porous carbon material (with a specific surface area of ​​1800 m) was used. 2 / g, the average pore diameter is 5 nm, and the pore volume is 0.8 cm 3 / g).

[0116] Fig. 9 shows the pore size distribution of the commercially available porous carbon material used in this example, and Fig. 10 is an enlarged view of the boxed area in Fig. 9. It can be seen from the figure that the pore sizes of the porous carbon material are concentrated in the range of 2 to 10 nm. Calculations show that the silicon crystal grain size in the silicon-carbon anode material finally produced in this example is 2.6153 nm.

[0117] Example 10 The production process was basically the same as in Example 8, with the only difference being that step (B) in the production of the asphalt-based porous carbon material was replaced with the following.

[0118] Nitrogen gas is introduced into a molecular sieve with a pore size of 5 nm to form nanogas, which is then introduced into the reactor. The flow rate of the introduced nanogas is 18 L / min, and the introduction time is 40 minutes. Nanobubbles are formed inside the softened asphalt, and the pressure inside the reactor is controlled to 9 MPa.

[0119] Measurements showed that the specific surface area of ​​the asphalt-based porous carbon material produced in this example was 2000 m 2 / g, the average pore diameter was 3.0 nm, and the pore volume was 1.1 cm 3 / g. The pore size concentration is 0.113, with the pore sizes concentrated in the range of 2 to 5 nm, the pore sizes are uniform, and the pore size distribution is narrow. According to calculations, the silicon crystal grain size in the silicon carbon anode material finally produced in this example is 2.4206 nm.

[0120] Example 11 The production process was basically the same as in Example 8, with the only difference being that step (B) in the production of the asphalt-based porous carbon material was replaced with the following.

[0121] Nitrogen gas is introduced into a molecular sieve with a pore size of 30 nm to form nanogas, which is then introduced into the reactor. The flow rate of the introduced nanogas is 15 L / min, and the introduction time is 30 minutes. Nanobubbles are formed inside the softened asphalt, and the pressure inside the reactor is controlled to 9 MPa.

[0122] Measurements showed that the specific surface area of ​​the asphalt-based porous carbon material produced in this example was 1000 m 2 / g, the average pore diameter was 10.2 nm, and the pore volume was 0.59 cm 3 / g. The pore size concentration is 0.108, with the pore sizes concentrated in the range of 8 to 15 nm, the pore sizes are uniform, and the pore size distribution is narrow. According to calculations, the silicon crystal grain size in the silicon carbon anode material finally produced in this example is 2.9879 nm.

[0123] Comparative Examples 14-15 The manufacturing process was basically the same as in Example 9, with the only difference being that the commercially available porous carbon materials in step (1) were replaced with commercially available porous carbon materials of equivalent mass and having the following apparent performance:

[0124] Comparative Example 14: Specific surface area is 450 m 2 / g, the average pore diameter was 15 nm, and the pore volume was 0.4 cm 3 / g, Comparative Example 15: Specific surface area is 2400 m 2 / g, the average pore diameter was 1.5 nm, and the pore volume was 1.8 cm 3 / g.

[0125] According to calculations, the silicon crystal grain size in the silicon carbon anode material finally prepared in Comparative Example 14 is 3.1573 nm, and that in Comparative Example 15 is 2.0186 nm.

[0126] Examples 12-13 The manufacturing process was basically the same as in Example 9, with the only difference being that the continuous introduction time of the mixed gas in step (2) was changed to 12 hours (Example 12) and 6 hours (Example 13), respectively.

[0127] According to calculations, the silicon crystal grain size of the silicon carbon anode material finally prepared in Example 12 is 2.8962 nm, and that of Comparative Example 13 is 2.6279 nm.

[0128] Examples 14-15 The manufacturing process was basically the same as in Example 9, with the only difference being that the composition of the mixed gas introduced in step (2) was replaced with the following:

[0129] Example 14: 90 vol% monosilane and 10 vol% acetylene; Example 15: 60 vol% monosilane and 40 vol% acetylene; According to calculations, the silicon crystal grain size of the silicon carbon anode material finally prepared in Example 14 is 2.9948 nm, and that of Comparative Example 15 is 2.467 nm.

[0130] Comparative Examples 16 to 18 The manufacturing process was basically the same as in Example 9, with the only difference being that the composition of the mixed gas introduced in step (2) was replaced with the following:

[0131] Comparative Example 16: 50 vol% monosilane and 50 vol% acetylene; Comparative Example 17: 95 vol% monosilane and 5 vol% acetylene; Comparative Example 18: 100 vol% monosilane (silicon deposition only).

[0132] According to calculations, the size of the silicon crystal grains in the final product produced in Comparative Example 16 is 2.139 nm, that in Comparative Example 17 is 4.581 nm, and that in Comparative Example 18 is 5.44 nm.

[0133] Fig. 11 shows the Raman spectrum of the silicon-carbon anode material prepared in Comparative Example 18, and Fig. 12 is an enlarged view of the framed area in Fig. 11. From the figure, it can be seen that the absorption peak is clearly shifted compared to that in Fig. 7 (Example 8), and the peak position is at 480 cm -1 From 500cm -1 It can be seen that the absorption peak intensity increases, the full width at half maximum narrows, and it can be concluded that the size of the silicon crystal grains in the product produced in this comparative example is significantly larger than that in Example 8. This conclusion is consistent with the change trend of the silicon crystal grain size obtained by calculation.

[0134] Examples 16 to 18 The manufacturing process was basically the same as in Example 9, with the only difference being that the continuous introduction time of the mixed gas in step (3) was changed to 1 hour (Example 16), 2 hours (Example 17), and 3 hours (Example 18), respectively.

[0135] According to calculations, the silicon crystal grain size of the silicon carbon anode material finally prepared in Example 16 is 2.6135 nm, that of Example 17 is 2.6147 nm, and that of Example 18 is 2.6098 nm.

[0136] Comparative Example 19 The manufacturing process was basically the same as in Example 9, except that the continuous introduction time of the mixed gas in step (3) was changed to 0.5 h. Calculations showed that the silicon crystal grain size of the silicon carbon anode material finally manufactured in this comparative example was 2.9125 nm.

[0137] Examples 19-20 The manufacturing process was basically the same as in Example 9, with the only difference being that in step (2), the pressure valve in the exhaust pipe was adjusted to maintain the furnace pressure at 5 KPa (Example 19) and 10 KPa (Example 20) in sequence.

[0138] According to calculations, the silicon crystal grain size of the silicon carbon anode material finally prepared in Example 19 is 2.5472 nm, and that of Example 20 is 2.9879 nm.

[0139] Example 21 (1) Under an argon gas atmosphere, 100 g of a porous carbon substrate with a D50 of 6.5 μm and a SPAN value of <1.5 was placed in a deposition furnace at a temperature of 400°C, and the specific surface area of ​​the porous carbon substrate was 800 m 2 / g, the average pore diameter was 5 nm, and the pore volume was 0.9 cm 3 / g, including through holes, (2) The gasified metallic lithium is introduced into a deposition furnace at a flow rate of 10 L / min, and the gas is continued to be introduced until nucleation and deposition occur continuously on the outer surface and inner pore surfaces of the porous carbon substrate to form a thin layer of metallic lithium. The gas is continued to be introduced for 3 hours, and the content of the thin layer of metallic lithium is controlled so that it becomes 5 wt% of the final negative electrode material.

[0140] (3) After lithium deposition is completed, the temperature is raised to 600°C, and monosilane is introduced into the deposition furnace at a flow rate of 20 L / min. The gas is continuously introduced for 10 h, and the deposition amount of nanosilicon particles is controlled so that it occupies 50% of the pore volume of the porous carbon substrate.

[0141] (4) After silicon deposition is completed, acetylene is introduced at a flow rate of 1 L / min to perform carbon coating at high temperature. The gas is continuously introduced and controlled so that the coating layer accounts for 5 wt% of the final anode material.

[0142] (5) After the deposition is completed, the temperature is lowered to room temperature, and the material is crushed, sieved, demagnetized, and other processes to obtain the silicon carbon anode material.

[0143] In the silicon-carbon anode material produced in this example, the content of the porous carbon substrate is 42.75 wt%, the content of the metallic lithium thin layer is 4.75 wt%, the content of the silicon is 47.5 wt%, and the content of the carbon coating layer is 5 wt%.

[0144] The silicon-carbon anode material produced in this example uses porous carbon as a substrate, and the outer and inner surfaces of the porous carbon substrate are uniformly coated with a thin layer of metallic lithium, nanosilicon particles are uniformly deposited on the thin layer of metallic lithium, and finally, a carbon coating layer is coated on the outermost surface.

[0145] Examples 22-23 The manufacturing process was basically the same as in Example 21, with the only difference being that the gas introduction time in step (2) was changed to 4 hours (Example 22) and 2 hours (Example 23), respectively.

[0146] Comparative Examples 20-21 The manufacturing process was basically the same as in Example 21, with the only difference being that the gas introduction time in step (2) was changed to 0.5 hours (Comparative Example 20) and 6 hours (Comparative Example 21), respectively.

[0147] Comparative Example 22 The manufacturing process was basically the same as in Example 21, with the only difference being that the deposition temperature in step (3) was changed to 1000°C.

[0148] Comparative Example 23 The manufacturing process is basically the same as in Example 21, with the following differences: In step (2), the gasified metallic lithium is introduced into the thermal deposition furnace at a flow rate of 0.5 L / min, and the gas is continued to be introduced for 40 h.

[0149] Comparative Example 24 (1) Under an argon gas atmosphere, 100 g of porous carbon substrate with D50 = 6.5 μm and SPAN value < 1.5 was placed in a thermal deposition furnace at a temperature of 400 °C, and the specific surface area of ​​the porous carbon substrate was 800 m 2 / g, the average pore diameter was 5 nm, and the pore volume was 1.0 cm 3 / g, including through holes, (2) The deposition furnace was heated to 800°C, and gasified metallic lithium was introduced into the deposition furnace at a flow rate of 0.5 L / min. The deposition time was 20 hours. (3) After lithium deposition is completed, the deposition furnace is cooled to 600°C, and monosilane is introduced into the deposition furnace at a flow rate of 0.5 L / min. The deposition time is 20 h. The alternate deposition process of step (2) and step (3) was repeated three times, with the gaseous lithium metal and monosilane introduced at 0.5 hour intervals, respectively, to uniformly deposit lithium metal particles and nanosilicon particles in the through-holes of the porous carbon microspheres. Steps (4) to (5) are completely the same as those in Example 21.

[0150] Comparative Example 25 Step (1) is exactly the same as in Example 21, In step (2), gaseous lithium is introduced into the thermal deposition furnace at a flow rate of 10 L / min, and the deposition time is 1 h; In step (3), after the lithium deposition is completed, monosilane is introduced into the deposition furnace at a flow rate of 20 L / min, and the deposition time is 2 h; The alternate deposition process of step (2) and step (3) was repeated three times, with gaseous metallic lithium and monosilane introduced at 0.5 hour intervals, respectively. Steps (4) to (5) are completely the same as those in Example 21.

[0151] The data of the specific surface area, pore volume, and pore structure utilization rate of the silicon carbon negative electrode materials produced in Examples 1 to 7 and Comparative Examples 1 to 13 are shown in Table 1 below.

[0152] Table 1 JPEG2026505513000005.jpg155170

[0153] The room temperature gas generation performance of the silicon carbon negative electrode materials produced in Examples 1 to 7 and Comparative Examples 1 to 13 was measured and the results are shown in Table 2 below.

[0154] Table 2 JPEG2026505513000006.jpg229170

[0155] During the silicon carbon deposition process, if silicon nanoparticles are well deposited within the porous carbon, i.e., uniformly distributed, without obvious pore blockage, with a high pore structure utilization rate and a low void ratio, the gas generation data will be good, and the gas generation data after 24 hours, 48 ​​hours, or 72 hours will show no significant change from the initial value. If uneven deposition or aggregation occurs, the initial gas generation value will increase significantly, and the gas generation rate will increase rapidly over time. Therefore, measuring gas generation at room temperature can indirectly determine the silicon deposition state. The gas generation rate can effectively determine the safety of the related material, and the higher the gas generation rate, the lower the safety of the product.

[0156] Application Examples The negative electrode materials produced in each of the examples and comparative examples were assembled into batteries.

[0157] (1) Manufacturing of positive electrode plate: Positive electrode active material nickel cobalt manganese oxide lithium (NCM811), conductive agent SuperP, carbon nanotubes, adhesive polyvinylidene fluoride (PVDF) are uniformly mixed in N-methylpyrrolidone (NMP) in a mass ratio of 97:1:0.5:1.5 to prepare positive electrode slurry (solid content 70 wt%), which is applied to both sides of the current collector copper foil, dried at 100°C, and cold pressed at room temperature at 4 MPa, followed by deburring, cutting, slitting, and welding of tabs to produce the positive electrode plate.

[0158] (2) Preparation of negative electrode plate: Under a nitrogen gas protective atmosphere, the solvent N-methylpyrrolidone and adhesive PVDF are stirred to homogeneity, the conductive agent SuperP is added and stirred to homogeneity, and then the negative electrode active material is added and stirred thoroughly to homogeneity to prepare a negative electrode slurry (solid content 50 wt%).

[0159] The negative electrode active material is obtained by thoroughly and uniformly mixing the silicon carbon negative electrode material and graphite prepared in the above examples and comparative examples, respectively, so that the gram capacity of the prepared negative electrode material is 450 mAh / g.

[0160] The negative electrode slurry is applied to both sides of a current collector copper foil, dried at 100°C, and then cold pressed at room temperature at 4 MPa. After that, deburring, cutting, and slitting are performed, and a tab is welded to produce a negative electrode plate.

[0161] (3) Lithium-ion battery assembly The PE porous polymer film was used as a separator, and the prepared positive electrode plate, separator, and negative electrode plate were stacked in order, with the separator positioned between the positive and negative electrode plates, and wound up to obtain a bare cell. The bare cell was then placed in an aluminum plastic shell package and cooled to -0.95 × 10 5The cells are dried at 100°C under a relative vacuum of 100 Pa until the moisture content is 100 ppm or less. An electrolyte consisting of ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) (volume ratio of EC:EMC:DEC = 1:1:1) and LiPF6 (1.0 M) is poured into the dried bare cells. The cells are then packaged, left to stand, chemically formed (charged at a constant current of 0.02 C for 2 hours, then charged at a constant current of 0.1 C for 2 hours), molded, and capacity measured (capacity grading) to produce pouch-type liquid lithium-ion batteries.

[0162] When assembling the battery, five batteries are manufactured for each measurement, and a total of five sets of data are measured, and the average of the five sets of data is used as the final performance data.

[0163] We measured the cycle performance of the battery using Xinwei's equipment, and specifically, At 25°C, discharge at 0.1C until the voltage reaches 0.005V, then discharge at 0.08C until the voltage reaches 0.001V, discharge at 0.05C until the voltage reaches 0.001V, discharge at 0.02C until the voltage reaches 0.001V, let stand for 10 minutes, charge at 0.1C until the voltage reaches 1.5V, let stand for 10 minutes, record the charge / discharge capacity after the first cycle, and calculate the initial coulombic efficiency. Cycle the battery 100 times using the above method, record the charge / discharge capacity after the 100th cycle, and calculate the capacity retention after the 100th cycle. The measurement and calculation process for the capacity retention after 500th cycle are the same.

[0164] The method for measuring the full charge expansion at the first cycle was to charge and discharge at a constant current of 0.1 C at room temperature, with the charge and discharge voltage limited to 0.005 to 1.5 V. After one cycle, the thickness of the plate was measured in the fully charged state and the full charge expansion rate was calculated as follows: full charge expansion rate = (plate thickness in the fully charged state - roll-pressed plate thickness) / (roll-pressed plate thickness - copper foil thickness) × 100%; plate expansion rate after one cycle = (plate thickness after one cycle - roll-pressed plate thickness) / (roll-pressed plate thickness - copper foil thickness) × 100%.

[0165] The powder resistance is measured by a semiconductor powder resistivity tester (30 MPa four-probe V1.4).

[0166] The electrochemical performance and powder resistance data of the lithium ion batteries assembled with the negative electrode materials prepared in Examples 1 to 7 and Comparative Examples 1 to 13, respectively, are shown in Table 3 below.

[0167] Table 3 JPEG2026505513000007.jpg179160

[0168] Data Analysis: Combining the data in Tables 1 to 3, the overall performance of silicon carbon anode materials is analyzed, and the specific analysis is as follows: Comparing the data from Examples 1-3 with Comparative Examples 1-3, it was found that when porous carbon materials with different specific surface areas, average pore diameters, pore volumes, and pore diameter concentrations were used as substrates, the step-by-step deposition method disclosed in the present invention achieved the goal of maximizing the pore structure utilization of the porous carbon substrate by precisely controlling the deposition parameters in the two stages. However, when a porous carbon material with a too small average pore diameter was selected as the substrate (Comparative Example 1), the amount of silicon deposited was too large at high pore structure utilization, and the cycle stability of the silicon-carbon anode material was severely affected by silicon expansion, resulting in rapid performance degradation and poor cycle stability. When a porous carbon material with a too large average pore diameter was selected as the substrate (Comparative Example 2), the limited pore volume resulted in a small amount of silicon deposited, reducing the reversible specific capacity and initial coulombic efficiency. Although the average pore size and pore volume of the selected porous carbon material are appropriate, if the concentration of pore sizes is too low (Comparative Example 3), the uniformity of the deposited silicon will be poor, and some stress will be concentrated during expansion, which will result in a deterioration of the overall electrochemical performance.

[0169] Comparing the data of Example 1 with Comparative Examples 4 and 5, it was found that compared to conventional bulk deposition (Comparative Example 4, i.e., a process without stepwise deposition), the stepwise deposition in Example 1, when used at the same deposition amount, can achieve a more uniform distribution of nanosilicon particles, a higher pore structure utilization rate, and better cycle stability. The data of Comparative Example 5 showed that a battery assembled using a silicon carbon anode material manufactured by reversing the stepwise deposition order exhibited limited cycle stability and a significant increase in surface resistance. This may be due to irrational design of the deposition process parameters, resulting in pore blockage and silicon deposition on the surface.

[0170] Comparing Example 1 with Comparative Examples 6 and 7, when a high gas flow rate is used in the first stage, the pore structure utilization rate is significantly reduced. This may be because the deposition is too fast, blocking the pore channels and significantly reducing the utilization rate of the pore structure, especially the micropores. Gas generation increases significantly, affecting safety and cycle stability. When a low gas flow rate is used in the second stage, gas generation increases significantly. This may be because the low gas flow rate, combined with the low furnace pressure, reduces the deposition efficiency, leading to uneven deposition and distribution of nanosilicon particles and significantly increasing gas generation.

[0171] Comparing Example 1 with Comparative Examples 8-10, when a reaction pressure that is too high in the first step (Comparative Example 8) was used, the pore structure utilization rate of the produced silicon carbon anode material decreased, and at the same time, gas generation significantly increased. This is likely due to the deposition rate being too fast, resulting in a very uneven distribution of nanosilicon and blocking many pore paths, which seriously impacts the cycle performance and safety performance of the silicon carbon anode. When a reaction pressure that is too high in the second step (Comparative Example 10) was used, gas generation also significantly increased. This is also due to the deposition rate being too fast, resulting in a very uneven distribution of nanosilicon, which seriously impacts the cycle performance and safety performance of the silicon carbon anode. When a reaction pressure that is too low in the first step (Comparative Example 9) was used, the pore structure utilization rate decreased, which significantly reduced the pore structure utilization rate and significantly increased gas generation. The low pore structure utilization rate further led to a relative decrease in the deposition amount and a decrease in capacity and initial coulombic efficiency.

[0172] Comparing Examples 1, 4, and 5 with Comparative Examples 11 and 12, it was found that a pressure change occurred in the first stage. When the ratio of the pressure change value to the initial pressure was too small (Comparative Example 11), the pore structure utilization rate of the fabricated silicon carbon anode material decreased, and both the capacity and initial coulombic efficiency of the assembled battery decreased. This was likely due to insufficient filling of the micropores, resulting in a decrease in the pore utilization rate and a corresponding decrease in the deposited silicon content, resulting in a slight decrease in both the capacity and initial coulombic efficiency. When the ratio of the pressure change value to the initial pressure was too large (Comparative Example 12), the pore structure utilization rate of the fabricated silicon carbon anode material did not change significantly, but the cycle stability of the assembled battery significantly deteriorated. This was likely due to the fact that after the deposition of the micropores was completed, the deposition of the mesopores was carried out at a high pressure. When the subsequent deposition process was combined, the mesopores were deposited in an excessive amount, resulting in uneven distribution, increased gas generation, and significantly deteriorated cycle performance.

[0173] Comparing Examples 1, 6, and 7 with Comparative Example 13, it was found that whether deposition was completed or not was determined by the pressure change in the second stage, and that an appropriate pressure change ensured high pore structure utilization and high silicon deposition, and ultimately ensured excellent electrochemical performance of the assembled battery. However, if the ratio of the pressure change value to the initial pressure was too large, silicon deposition on the porous carbon surface increased, resulting in a significant increase in resistance, an increase in gas generation, and a significant deterioration in cycle performance.

[0174] The electrochemical performance and electrode plate expansion coefficient data of the lithium ion batteries assembled using the negative electrode materials produced in Examples 8 to 20 and Comparative Examples 14 to 19 are shown in Table 4 below.

[0175] Table 4 JPEG2026505513000008.jpg163170

[0176] The electrochemical performance, lithium content and silicon crystalline domain data of the lithium ion batteries assembled with the negative electrode materials prepared in Examples 21 to 23 and Comparative Examples 20 to 25, respectively, are shown in Table 5 below.

[0177] Table 5 JPEG2026505513000009.jpg100170 a: Measurement of silicon crystalline domains: Because amorphous materials lack long-range ordered structures, their structure cannot be analyzed by conventional methods such as X-ray diffraction (XRD). However, the present invention calculates the size of silicon crystal grains (111) using the Debye-Scherrer equation. b: / means that specific data cannot be measured because the powder of the electrode plate has fallen off.

[0178] Analysis of the data in Table 5 above, comparing Examples 21 to 23 with Comparative Examples 20 and 21, shows that the content (corresponding to thickness) of the produced metallic lithium layer can be adjusted by adjusting the continuous gas introduction time in step (2). It was found that a metallic lithium layer that was too thick or too thin would affect the initial Coulombic efficiency of the material. Further analysis of the data revealed that if the metallic lithium layer was too thick, the pore size of the porous carbon could not be changed, and the thick metallic lithium layer would occupy and block some of the pores. This would prevent some of the deposited silicon from entering the pore structure of the porous carbon, affecting the cycling stability of the material. However, if the metallic lithium layer was too thin, the limiting effect on the nanosilicon particle size would be reduced, and the deposited silicon would still maintain a relatively large particle size, which would also affect the cycling stability of the material.

[0179] Comparing Example 21 and Comparative Example 22, it was found that when silicon was deposited at high temperatures, the deposited silicon existed in the form of crystalline silicon, and the nanosilicon particle size was large, so it could not be deposited inside the porous carbon substrate, and its cycle stability was significantly reduced.

[0180] Comparing Example 21 with Comparative Example 23, it was found that when gasified metallic lithium was introduced into a thermal deposition furnace at a very low flow rate for lithium deposition, the cycle stability and reversible specific capacity of the lithium-ion battery finally assembled with the silicon carbon anode material were significantly reduced. Analysis of the reason for this revealed that the low-rate deposition resulted in discrete lithium particles, which on the one hand did not completely cover the porous carbon surface, and during the subsequent high-temperature silicon deposition and carbon coating process, some silicon was in contact with the porous carbon substrate and was prone to react, forming chemically inert silicon carbide, which reduced the reversible specific capacity; on the other hand, compared with the metallic lithium thin layer, the lithium particles had a larger specific surface area, which resulted in a higher degree of lithium-silicon alloying, which significantly reduced the cycle stability.

[0181] Comparing Example 21 with Comparative Examples 23 and 24, it was found that in Comparative Example 23, lithium and silicon were alternately deposited, and the high temperature accelerated the lithium-silicon alloying reaction, which resulted in a large volume expansion and contraction of the nano-silicon before the subsequent lithium absorption and desorption process, making the structure of the anode material brittle and resulting in extremely poor cycle stability and no future application.

[0182] Comparing Example 21 with Comparative Example 25, it can be seen that the cycle stability and reversible specific capacity of the lithium ion battery assembled with the silicon carbon anode material obtained after alternate deposition are both obviously deteriorated.

[0183] The above disclosure is a preferred embodiment, but the scope of protection of the present invention is not limited thereto. Those skilled in the art can easily understand the spirit of the present invention based on the above embodiment and make various derivations and modifications, and any of them fall within the scope of protection of the present invention as long as they do not deviate from the spirit of the present invention.

Claims

1. A porous carbon material, The pore diameter concentration of the porous carbon material is 0.03 to 1.0, and the concentration is defined by the following calculation formula: P: pore volume, P ａｌｌ : total pore volume, d ｍａｘ＊ : Maximum pore diameter when P>0.005, d ｍｉｎ＊ : A porous carbon material characterized in that the minimum pore diameter is when P>0.

005.

2. the porous carbon material has a SPAN value of less than 1.5 and a D50 of 4 to 10 μm; The specific surface area of ​​the porous carbon material is 300 to 3000 m ２ / g, the average pore diameter is 1 to 10 nm, and the pore volume is 0.5 to 2.0 cm ３ The porous carbon material according to claim 1, characterized in that the molecular weight of the porous carbon material is 1 / g.

3. The specific surface area of ​​the porous carbon material is 1200 to 2000 m ２ / g, the average pore diameter is 1.5 to 5.0 nm, and the pore volume is 0.6 to 2.0 cm ３ / g, and the pore size concentration is 0.03 to 1.

0.

4. A method for producing a silicon-carbon anode material using the porous carbon material according to any one of claims 1 to 3, comprising: The method includes the steps of depositing a silicon source in stages using the porous carbon material as a substrate, depositing nanosilicon particles inside the pores of the porous carbon material, and further coating the surface of the nanosilicon particles with carbon to obtain a high-performance silicon-carbon anode material; The stepwise silicon source deposition is performed by vapor-phase deposition using a silicon source gas as a raw material gas, (1) A first stage in which the temperature in the reactor is controlled to 300 to 800°C, the initial pressure is controlled to 10 to 30 Kpa, and the flow rate of the introduced raw material gas is controlled to 2 to 10 L / min, and the pressure in the reactor starts to decrease, and when the pressure change value reaches 10 to 70% of the initial pressure, the process proceeds to the next stage; (2) a second step of adjusting the initial pressure in the reactor to 5 to 8 Kpa, adjusting the flow rate of the introduced raw material gas to 8 to 20 L / min, and terminating deposition when the pressure in the reactor starts to increase and the pressure change value reaches 10 to 70% of the initial pressure.

5. the silicon source gas is selected from one or more of monosilane, disilane, dichlorosilane, and trichlorosilane; the source gas is a mixed gas containing a silicon source gas and an inert gas, the silicon source gas occupies 70 to 99 vol % in the mixed gas; In the first stage, when the pressure change value in the reactor reaches 20 to 67% of the initial pressure, the process proceeds to the next stage; 5. The method for producing a silicon-carbon anode material according to claim 4, wherein in the second stage, deposition is terminated when the pressure change value in the reactor reaches 15 to 50% of the initial pressure.

6. the surface carbon coating is carried out by vapor-phase deposition at a temperature of 400 to 1000°C using a mixed gas composed of a carbon source gas and an inert gas as a raw material gas; The carbon source gas is selected from alkane gases having a decomposition temperature of 400 to 1200°C; the volume ratio of the carbon source gas in the mixed gas is 60 to 99 vol %, The flow rate of the mixed gas is 0.1 to 50 L / min.

5. The method for preparing a silicon-carbon anode material as claimed in claim 4, wherein the temperature of the vapor deposition is 400-600°C.

7. A silicon carbon anode material produced by the method according to any one of claims 4 to 6, The silicon-carbon anode material has a deposited silicon content of 40-60 wt % and a specific surface area of ​​<25 m ２ / g, pore structure utilization rate is >96%, powder resistivity is <35 Ω cm, and gas generation value after 72 h is <110 ppm.

8. Step 1: placing a porous carbon material as a substrate in a deposition furnace under an inert atmosphere and heating the furnace to 400 to 700°C; Step 2: introducing a mixed gas A containing a silicon source gas and a carbon source gas into the deposition furnace, adjusting a pressure valve of an exhaust pipe to constantly maintain the furnace pressure during deposition at 5 to 10 kPa while continuing to introduce the gas, thereby performing vapor phase deposition and obtaining an intermediate product; and step 3, after the furnace temperature is lowered to 200 to 300°C, a mixed gas B containing an oxygen-containing gas and a carrier gas is introduced into the deposition furnace, and surface passivation and post-treatment are performed to obtain a silicon-carbon anode material.

9. In step 2, the silicon source gas is selected from one or more of monosilane, disilane, dichlorosilane, and trichlorosilane; The carbon source gas is selected from alkane gases that decompose at 400 to 800°C; In the mixed gas A, the volume ratio of the silicon source gas is 1 to 99%, and the volume ratio of the carbon source gas is 1 to 99%, The flow rate of the mixed gas A is 0.1 to 50 L / min, The vapor deposition time is 2 to 16 hours; In step 3, the oxygen-containing gas is selected from one or more of oxygen, carbon monoxide, carbon dioxide, ethanol gas, and isopropanol gas; the carrier gas is selected from nitrogen gas and / or an inert gas; In the mixed gas B, the volume ratio of the oxygen-containing gas is 1 to 10%, and the volume ratio of the carrier gas is 90 to 99%, the flow rate of the mixed gas B is 0.1 to 50 L / min; 9. The method for preparing a silicon-carbon anode material as claimed in claim 8, wherein the surface passivation time is 0.5-5.0 hours.

10. 10. A silicon carbon anode material produced by the method of claim 8 or 9.

11. 4. A prelithiated silicon carbon anode material produced by using the porous carbon material according to claim 1, comprising a porous carbon material substrate, a thin layer of metallic lithium coating the outer surface and inner wall of the porous carbon material substrate, nanosilicon particles deposited on the thin layer of metallic lithium, and an outermost carbon coating layer.

12. Based on the total mass of the prelithiated silicon carbon anode material, the content of the metallic lithium thin layer is 1-10 wt %, the content of silicon is 30-90 wt %, the content of the carbon coating layer is 1-10 wt %, and the remainder is the porous carbon material substrate; 12. The prelithiated silicon carbon anode material of claim 11, wherein the silicon crystalline domains of the nanosilicon particles are ≦5 nm.

13. 13. A method for producing the prelithiated silicon carbon anode material of claim 11 or 12, comprising: Step (1) of placing a porous carbon material substrate in a deposition furnace under an inert atmosphere and raising the temperature to 200 to 800°C; (2) introducing a lithium source gas into a deposition furnace and depositing it on the surface of the porous carbon substrate to form a thin layer of metallic lithium; (3) after the lithium deposition is completed, adjusting the temperature of the deposition furnace to 400-800°C, and introducing a silicon source gas to deposit silicon so that the amount of deposited nanosilicon occupies 40-90% of the pore volume of the porous carbon substrate; and (4) after completion of silicon deposition, adjusting the temperature of the deposition furnace to 400 to 1000°C, and introducing a carbon source gas to perform a carbon coating treatment, thereby obtaining a prelithiated silicon carbon anode material.

14. In step (2), The lithium source gas is obtained by heating and gasifying metallic lithium or lithium hydride as a raw material, the flow rate of the lithium source gas is 5 to 50 L / min; In step (3), the silicon source gas is selected from one or more of monosilane, disilane, dichlorosilane, and trichlorosilane; the flow rate of the silicon source gas is 0.1 to 50 L / min; In step (4), The carbon source gas is selected from alkane gases that can be decomposed at 400 to 800°C; 14. The method for preparing a prelithiated silicon-carbon anode material according to claim 13, wherein the flow rate of the carbon source gas is 0.1 to 50 L / min.

15. a negative electrode plate including a negative electrode current collector and a negative electrode active material layer deposited on the negative electrode current collector; A negative electrode plate, characterized in that the negative electrode active material layer contains the silicon carbon negative electrode material according to any one of claims 7 and 10 to 12.

16. A battery comprising the negative electrode plate of claim 15.

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