Silicon-carbon negative electrode material capable of inducing silane deposition through chemical bonding and preparation method of silicon-carbon negative electrode material

Abstract

The invention belongs to the technical field of energy storage materials, and particularly relates to a silicon-carbon negative electrode material with silane deposition induced by chemical bonding and a preparation method of the silicon-carbon negative electrode material. A porous carbon material obtained through liquid phase mixing and gas corrosion serves as a matrix, silicon particles are induced to be deposited in pores of the porous carbon material through chemical reaction between silane and a doping agent, and the silicon-carbon negative electrode material is prepared. And fully mixing with asphalt to finish coating of an asphalt carbon layer, thereby obtaining the silicon-carbon negative electrode material. Chemical bonding between the nano silicon particles and the porous carbon realizes directional deposition of silane, and is beneficial to transmission of lithium ions; pores of the porous carbon limit the expansion space of the nano silicon particles, and the influence of silicon expansion is reduced; the nitrogen element in the dopant improves the surface roughness of the porous carbon material, so that silicon particles are deposited more uniformly; and the internal porous carbon matrix and the external coated conductive asphalt carbon layer make up for the defect of poor conductivity of silicon. The silicon-carbon material has a more stable electrode structure and higher capacity, and the rate capability and cycling stability of the battery are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage materials, and particularly relates to a silicon-carbon anode material induced by chemical bond to deposit silane and a preparation method thereof. Background Art

[0002] In order to cope with the depletion of reserves of non-renewable energy sources such as coal and oil and severe climate problems such as the "greenhouse effect", more and more clean energy has been developed and used in social production and life. Lithium-ion batteries occupy the dominant position in the electrochemical energy storage market due to their high energy density, long cycle life, low self-discharge, and green and pollution-free advantages, and are widely used in fields such as aerospace, intelligent power generation, transportation, digital products, and flexible wearable devices. With the progress of technology, higher requirements for the energy density of lithium-ion batteries have also been put forward in various fields. However, the specific capacity per gram of traditional graphite anodes has reached the theoretical limit, which greatly restricts the development of high specific capacity lithium-ion batteries.

[0003] Silicon is regarded as the most potential anode material for the next generation due to its ultra-high theoretical specific capacity and rich natural reserves. However, silicon also has the following defects during application: (1) The huge volume expansion during the lithium deintercalation and intercalation processes will cause the active material particles to break and the electrode to powder; (2) The expansion of the active material particles causes the SEI film to break, exposing more interfaces to consume Li + to generate an overly thick SEI film; (3) The intrinsic conductivity of silicon is poor. Using a composite design of carbon materials and silicon to make up for the above defects of silicon anodes is an effective way.

[0004] Patent CN119050290A discloses a porous nano silicon-carbon composite material coated with a carbon layer. The nano-silicon slurry is mixed and stirred with a phenolic resin solution, then spray-dried, and after high-temperature carbonization, a coal tar pitch slurry is added, and the final porous nano silicon-carbon material is obtained through ball milling and mixing carbonization. Although this material can buffer the volume expansion of nano-silicon particles before and after cycling to a certain extent and improve battery stability, ball milling will damage the structure of the active material particles, and ball milling can only achieve uniform mixing of pitch and nano silicon-carbon, and it is difficult to achieve uniform coating. Therefore, the inhibitory effect on electrode expansion is limited. Summary of the Invention

[0005] Aiming at the deficiencies of the above-mentioned prior art, the present invention provides a silicon-carbon anode material induced by chemical bond to deposit silane and a preparation method thereof to solve the problem of uneven deposition and coating of silicon-carbon in the prior art.

[0006] The present invention is specifically implemented by the following technical solutions.

[0007] The present invention provides a preparation method of a silicon-carbon anode material induced by chemical bond to deposit silane, comprising the following steps: Put the binder, asphalt, graphite, dopant and dispersant into a solvent to obtain a mixed system and prepare a precursor of porous carbon material; wherein, the dopant contains alcohol hydroxyl groups and amino groups.

[0008] Put the precursor of porous carbon material into a tubular furnace, introduce CO2, and carry out gas corrosion to form pores on the precursor of porous carbon material at high temperature to obtain a modified porous carbon material.

[0009] Put the modified porous carbon material into a CVD furnace, introduce silane, the chemical bonding between the alcohol hydroxyl groups in the dopant and silane induces the preferential deposition of silane inside the pores of the porous carbon, and the nitrogen element in the dopant is beneficial to improving the surface roughness of the precursor of porous carbon material, making the deposition of silicon particles more uniform, and obtaining a precursor of silicon-carbon anode material.

[0010] First, thoroughly mix the precursor of silicon-carbon anode material and asphalt in a mixer, then add them into a high-temperature coating furnace for asphalt coating and carbonization treatment to obtain an asphalt carbon layer on the outermost layer and get the final silicon-carbon anode material.

[0011] Preferably, the dopant is any one of ethanolamine, methylethanolamine, N,N-dimethylpropanolamine, N,N-diethylpropanolamine, 2-aminon-butanol, isobutanolamine or dibutanolamine.

[0012] Preferably, the binder is any one of sodium carboxymethylcellulose, polyvinylidene chloride, polyacrylic acid, polyvinyl alcohol and polymethyl methacrylate.

[0013] Preferably, the solvent is any one of tetrahydrofuran, cyclohexane or petroleum ether, and is mixed with 1% (mass fraction is 1%) of p-toluenesulfonic acid.

[0014] Preferably, the dispersant is polyvinylpyrrolidone.

[0015] Preferably, in the mixture composed of the binder, asphalt, graphite, dopant and dispersant, the mass percentage of the binder is 1% - 3%, the mass percentage of asphalt is 30% - 60%, the mass percentage of graphite is 20% - 50%, the mass percentage of the dopant is 10% - 20%, and the mass percentage of the dispersant is 1% - 2%, with a total of 100%.

[0016] Preferably, during the gas corrosion to form pores, the temperature is 700°C - 1000°C, the time is 1 h - 2.5 h, and the CO2 flow rate is 40 mL·min -1 ~80 mL·min -1 。

[0017] Preferably, during the silane deposition, the temperature is 500°C - 700°C, the time is 1 h - 3 h, and the silicon source flow rate is 50 mL·min -1~100 mL·min -1 。

[0018] Preferably, in the mixture composed of the silicon-carbon anode material precursor and pitch, the mass percentage of the silicon-carbon anode material precursor is 60% - 90%, and the balance is pitch, totaling 100%.

[0019] Preferably, during the pitch coating and carbonization processes, under a protective gas atmosphere, the temperature in the first half is 150°C - 300°C, the heat preservation time is 1h - 1.5h, and the rotation speed is 250 r·min -1 ~400 r·min -1 ; in the second half, the temperature is 600°C - 800°C, the heat preservation time is 0.5h - 1.5h, and the rotation speed is 100 r·min -1 ~250 r·min -1 ; N2 is used as the protective gas, and the N2 flow rate is 30 mL·min -1 ~50 mL·min -1 。

[0020] When the preferred silicon-carbon anode material precursor and pitch are fully mixed in a mixer first, the rotation speed of the mixer is 450 r·min -1 ~650 r·min -1 ; and the mixing time is 20 min - 40 min.

[0021] Preferably, when preparing the porous carbon material precursor, the binder, pitch, graphite, dopant, and dispersant are dissolved in a solvent to obtain a mixed system. The solid content of the mixed system is 30% - 60% (i.e., the total mass fraction of the binder, pitch, graphite, dopant, and dispersant is 30% - 60%). First, ultrasonic dispersion is carried out, and then stirring and drying are carried out at 50°C - 80°C with a stirring speed of 300 r·min -1 ~400 r·min -1 .

[0022] The present invention also provides a silicon-carbon anode material prepared by the above preparation method. With the porous carbon material as the matrix, silicon nanoparticles are induced to deposit inside the pores through chemical bonding, and the outermost layer of the matrix is wrapped with a pitch carbon layer.

[0023] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a preparation method of a silicon-carbon anode material induced by chemical bond-induced silane deposition. In this method, a porous carbon material obtained through liquid-phase mixing and gas corrosion is used as the matrix, and a dopant is fully mixed inside the porous carbon material. During the deposition of nano-silicon, the chemical bond between the dopant and silane induces the preferential deposition of silane in the pores of the porous carbon, forming a silicon-carbon precursor material. The pores of the porous carbon are used to limit the expansion of nano-silicon particles. At the same time, the chemical bond between the nano-silicon particles and the matrix material is also beneficial to the diffusion and transmission of lithium ions. The nitrogen element in the dopant is beneficial to improving the surface roughness of the porous carbon material, making the deposition of silicon particles more uniform. Finally, the asphalt carbon layer coating carried out in a high-temperature coating machine is divided into two-stage heating. In the first half, it is heated to the softening point of asphalt, and it is fully stirred and coated on the surface of the silicon-carbon precursor in a molten state. In the second half, high-temperature heating is carried out to complete carbonization to obtain the final silicon-carbon anode material, solving the problem of uneven silicon-carbon deposition and coating in the prior art, effectively suppressing the problems brought by electrode expansion, and improving the battery stability. The preparation method of the present invention is simple and suitable for large-scale industrial production.

[0024] The present invention also discloses a silicon-carbon anode material induced by chemical bond-induced silane deposition. This silicon-carbon anode material uses a porous carbon material as the matrix, and nano-scale silicon particles are deposited inside the pores of the porous carbon through chemical bonding, and the outermost layer is uniformly coated with an asphalt carbon layer. The three-dimensional conductive network constructed by the matrix of this material and the external carbon layer make up for the disadvantage of poor intrinsic conductivity of silicon. The chemical bond between the nano-silicon particles and the porous carbon matrix realizes the directional deposition of silane. The pores of the porous carbon are used to limit the expansion space of the nano-silicon particles, alleviating the impact of silicon expansion on the electrode. The nitrogen element in the dopant is beneficial to improving the surface roughness of the porous carbon material, making the deposition of silicon particles more uniform and consistent. The asphalt coating process carried out in a molten state makes the external asphalt carbon layer wrap more evenly. This material has a more stable electrode structure, improves the rate performance and cycle stability of the battery, and has great commercial potential.

[0025] Furthermore, when this anode material is applied in a lithium-ion battery, this anode material combines the high specific capacity of silicon materials and the excellent conductivity and cycle performance of carbon materials. It has a higher initial Coulomb efficiency and capacity, and better cycle stability. It is a very promising anode material for lithium-ion batteries. Description of the Drawings

[0026] Figure 1 It is a scanning electron microscope image of the silicon-carbon anode material prepared in Example 1.

[0027] Figure 2 It is an enlarged scanning electron microscope image of the silicon-carbon anode prepared in Example 1.

[0028] Figure 3BET test result diagram of the silicon-carbon anode material precursor prepared in step 3 of Example 1.

[0029] Figure 4 First Coulomb efficiency diagram of the silicon-carbon anode prepared in Example 1.

[0030] Figure 5 Cyclic discharge specific capacity diagram of the silicon-carbon anode prepared in Example 1. Detailed implementation manners

[0031] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and drawings. However, the specific embodiments cited do not limit the present invention. The experimental methods and detection methods described in the following embodiments are all conventional methods unless otherwise specified; the reagents and materials are all commercially available unless otherwise specified.

[0032] The present invention provides a preparation method of a silicon-carbon anode material induced by chemical bond-induced silane deposition, and the specific steps are as follows: Step 1, put a binder, asphalt, graphite, a dopant and a dispersant into a solvent to obtain a mixed system, seal and ultrasonically disperse for 30 min, physically mix evenly, and stir it at a certain temperature at high speed until the solvent is evaporated to dryness to obtain a porous carbon material precursor.

[0033] Preferably, in the mixture composed of the binder, asphalt, graphite, dopant and dispersant, the mass percentage of the binder is 1% - 3%, the mass percentage of the asphalt is 30% - 60%, the mass percentage of the graphite is 20% - 50%, the mass percentage of the dopant is 10% - 20%, and the mass percentage of the dispersant is 1% - 2%, with a total of 100%.

[0034] Preferably, the binder is any one of sodium carboxymethyl cellulose, polyvinylidene chloride, polyacrylic acid, polyvinyl alcohol and polymethyl methacrylate.

[0035] Among them, the dopant contains alcohol hydroxyl and amino groups; the dopant is any one of ethanolamine, methylethanolamine, N,N-dimethylpropanolamine, N,N-diethylpropanolamine, 2-aminon-butanol, isobutanolamine or dibutanolamine.

[0036] The solvent is any one of tetrahydrofuran, cyclohexane or petroleum ether, and is mixed with 1% of p-toluenesulfonic acid (providing acidic conditions). The dispersant is polyvinylpyrrolidone.

[0037] The solid content of the mixed system is 30% - 60%, that is, the total mass fraction of the binder, asphalt, graphite, dopant and dispersant is 30% - 60%.

[0038] Preferably, the stirring temperature is 50°C to 80°C, and the stirring speed is 300 r·min -1 ~400 r·min -1 .

[0039] Step 2: placing the porous carbon material precursor in a tube furnace, introducing CO2, and subjecting the porous carbon material precursor to gas corrosion to form pores, thereby obtaining a modified porous carbon material.

[0040] In the process of gas corrosion pore formation, the temperature is 700℃~1000℃, the time is 1h~2.5h, and the CO2 flow rate is 40mL·min -1 ~80mL·min -1 The pore size of porous carbon materials can be adjusted by adjusting the temperature and gas flow rate during the corrosion process.

[0041] Step 3: Place the obtained modified porous carbon material in a CVD furnace and heat at 50 mL min -1 ~100mL·min -1 A silicon source is introduced at a flow rate of , and the porous carbon material is subjected to silicon deposition treatment at 500℃~700℃ for 1h~3h to obtain a silicon-carbon negative electrode material precursor with nano-silicon particles deposited inside the pores of the porous carbon.

[0042] Preferably, the silicon source is silane.

[0043] In this process, the dopant doped in the porous carbon first reacts with the silicon source to induce the directional deposition of silane. The subsequent thermal decomposition of silane will continue to deposit atoms on the silicon to form nano-scale silicon particles. The dopant contains alcoholic hydroxyl groups and amino groups. The alcoholic hydroxyl groups can chemically bond with silane under acidic conditions to replace silicon with the dopant. Nitrogen acts as a doping element to improve the surface roughness.

[0044] Step 4: The obtained silicon-carbon negative electrode material precursor is fully mixed with asphalt and then placed in a high-temperature coating machine for carbon layer coating. The stirring speed of the mixer is 450 r·min. -1 ~650r·min -1 The mixing time is 20min~40min, the temperature in the first half of the high-temperature coating process is 150℃~300℃, the holding time is 1h~1.5h, and the rotation speed is 250r·min -1 ~400r·min -1 The temperature in the second half is 600℃~800℃, the holding time is 0.5h~1.5h, and the rotation speed is 100r·min -1 ~250r·min -1 , N2 flow rate is 30 mL·min -1 ~50mL·min -1。The pitch carbon layer coating in the high-temperature coating machine is divided into two-stage heating. In the first half, it is heated to the softening point of the pitch, and it is fully stirred and coated on the surface of the silicon-carbon precursor in a molten state. In the second half, high-temperature heating is carried out to complete carbonization to obtain the final silicon-carbon negative electrode material.

[0045] Preferably, in the mixture composed of the silicon-carbon negative electrode material precursor and pitch, the mass percentage of the silicon-carbon negative electrode material precursor is 60% - 90%, and the balance is pitch, with a total of 100%.

[0046] The present invention also provides a silicon-carbon negative electrode material with chemical bond-induced silane deposition. The material matrix is a hierarchically porous carbon. Nanoscale silicon particles are deposited between the pores of the porous carbon material, and the outermost layer is wrapped with a pitch carbon layer.

[0047] The present invention also provides a lithium-ion battery, which is composed of a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode material is the silicon-carbon negative electrode material prepared by chemical bond-induced silane deposition as described above in the present invention.

[0048] The following further describes the present invention in detail with reference to embodiments: Example 1 A preparation method of a silicon-carbon negative electrode material with chemical bond-induced silane deposition includes the following steps: Step 1: Dissolve sodium carboxymethylcellulose, pitch, graphite, ethanolamine, and polyvinylpyrrolidone in tetrahydrofuran in a mass ratio of 3:35:50:10:2 to obtain a mixed system, where the solid content is 30% (the solid content is the total mass of the binder, pitch, graphite, dopant, and dispersant), the content of tetrahydrofuran is 69%, and the content of p-toluenesulfonic acid is 1%. After sealing the mixed system and ultrasonically dispersing it for 30 min, stir it on a 70°C heating table at a stirring speed of 350 r·min -1 until the solvent is evaporated to dryness to obtain a porous carbon material precursor.

[0049] Step 2: Place the porous carbon material precursor in a tubular furnace at 800°C, introduce CO2, with a gas flow rate of 50 mL·min -1 , and the corrosion time is 1 h to obtain a modified porous carbon material.

[0050] Step 3: Place the obtained modified porous carbon material in a CVD furnace, introduce silane, with a gas flow rate of 80 mL·min -1 , and carry out silane deposition on the porous carbon material at 600°C for 2 h. The chemical bond between silane and the dopant will induce silane to deposit in the pores of the porous carbon to obtain a silicon-carbon negative electrode material precursor with nanoscale silicon materials deposited inside the porous carbon.

[0051] Step 4: Place the silicon-carbon negative electrode material precursor and asphalt in a mixer at a mass ratio of 4:1 and mix thoroughly. The mixer speed is 500 r / min. -1 , the mixing time is 30min. After fully mixing, transfer to the high temperature coating machine, the speed is 250r·min -1 , heat to 200℃, keep warm for 1h, then heat to 650℃, adjust the speed to 150r·min -1 , keep warm for 1h, N2 was used as protective gas during the coating process, and the gas flow rate was 30mL·min -1 , and obtain the final silicon-carbon negative electrode material.

[0052] Figure 1 and Figure 2 This is a scanning electron microscope image of the chemically bonded silane-deposited silicon-carbon negative electrode material prepared in this embodiment. It can be seen from the image that the material has good consistency and the size is 5μm~30μm.

[0053] The silicon-carbon negative electrode material precursor prepared in step 3 of this embodiment was subjected to BET test. The results are as follows: Figure 3 As shown, the distribution of pore sizes of different sizes can be seen more intuitively, indicating that after the deposition of silicon nanoparticles, there is still space to provide expansion for buffering.

[0054] The above silicon-carbon negative electrode material was mixed with a conductive agent and a binder in a ratio of 8:1:1 and deionized water was added to adjust the solid content to 25% to obtain a uniformly dispersed negative electrode slurry. The slurry was coated on a copper foil current collector and vacuum dried to obtain the final electrode. The silicon-carbon composite electrode was transferred to an argon-filled vacuum glove box to assemble a CR2032 button half-cell for testing. The results are shown in Figure 2. Figure 4 and Figure 5 As shown, the specific performance is: in the first cycle current 0.2A g -1 Under the test conditions, the first coulombic efficiency was 91.92%, and the first-week discharge capacity was 1610.26 mAh g -1 , then at a current of 1A·g -1 Under the condition of , the capacity is 820.46mAh·g after 100 cycles. -1 The capacity retention rate is 96.38%, and the cycle stability performance is good.

[0055] Example 2 A method for preparing a silicon-carbon negative electrode material for chemical bonding-induced silane deposition comprises the following steps: Step 1: Dissolve polyacrylic acid, asphalt, graphite, ethanolamine, and polyvinyl pyrrolidone in tetrahydrofuran at a mass ratio of 3:40:35:20:2 to obtain a mixed system with a solid content of 30% (the solid content is the total mass of the binder, asphalt, graphite, dopant, and dispersant), a tetrahydrofuran content of 69%, and a p-toluenesulfonic acid content of 1%. After sealing the mixed system and ultrasonically dispersing it for 30 minutes, the system was heated on a 70°C heating plate at 350 r / min. -1 The mixture is stirred at a stirring speed of 10000 rpm until the solvent is evaporated to dryness to obtain a porous carbon material precursor.

[0056] Step 2: Place the porous carbon material precursor in a 900°C tube furnace and introduce CO2 at a gas flow rate of 70 mL min -1 , the corrosion time is 1.5h, and the modified porous carbon material is obtained.

[0057] Step 3: Place the obtained modified porous carbon material in a CVD furnace and introduce silane at a gas flow rate of 60 mL min -1 Silane deposition is performed on the porous carbon material at 500°C for 1.5 hours. The chemical bonding between silane and the dopant will induce the deposition of silane in the pores of the porous carbon, thereby obtaining a silicon-carbon negative electrode material precursor with nano-silicon material deposited inside the porous carbon.

[0058] Step 4: Place the silicon-carbon negative electrode material precursor and asphalt in a mixer at a mass ratio of 4:1 and mix thoroughly. The mixer speed is 600 r / min. -1 , the mixing time is 30min. After fully mixing, transfer to the high temperature coating machine, the speed is 300r·min -1 , heat to 200℃, keep warm for 1h, then heat to 750℃, adjust the speed to 150r·min -1 , keep warm for 1h, N2 was used as protective gas during the coating process, and the gas flow rate was 30mL·min -1 , and obtain the final silicon-carbon negative electrode material.

[0059] The above silicon-carbon negative electrode material was mixed with a conductive agent and a binder in a ratio of 8:1:1 and deionized water was added to adjust the solid content to 25% to obtain a uniformly dispersed negative electrode slurry. The slurry was coated on a copper foil current collector and vacuum dried to obtain the final electrode. The silicon-carbon composite electrode was transferred to an argon-filled vacuum glove box to assemble a CR2032 button half-cell for testing. The specific performance was: at the first cycle current of 0.2A·g -1 Under the test conditions, the first coulombic efficiency was 89.67%, and the first-week discharge capacity was 1448.37 mAh g -1 , then at a current of 1A·g -1 Under the condition of , the capacity is 743.21mAh·g after 100 cycles. -1, the cycle stability performance is good.

[0060] Example 3 A method for preparing a silicon-carbon negative electrode material for chemical bonding-induced silane deposition comprises the following steps: Step 1: Dissolve polymethyl methacrylate, asphalt, graphite, ethanolamine, and polyvinyl pyrrolidone in tetrahydrofuran at a mass ratio of 3:60:20:15:2 to obtain a mixed system with a solid content of 30% (the solid content is the total mass of the binder, asphalt, graphite, dopant, and dispersant), a tetrahydrofuran content of 69%, and a p-toluenesulfonic acid content of 1%. After the mixture is sealed and ultrasonically dispersed for 30 minutes, the mixture is heated on a heating plate at 70°C at 400 r / min. -1 The mixture is stirred at a stirring speed of 10000 rpm until the solvent is evaporated to dryness to obtain a porous carbon material precursor.

[0061] Step 2: Place the porous carbon material precursor in a 1000°C tube furnace and introduce CO2 at a gas flow rate of 80 mL min -1 , the corrosion time is 1h, and the modified porous carbon material is obtained.

[0062] Step 3: Place the obtained modified porous carbon material in a CVD furnace and introduce silane at a gas flow rate of 100 mL min -1 Silane deposition is performed on the porous carbon material at 550°C for 2 hours. The chemical bonding between silane and the dopant will induce silane to deposit in the pores of the porous carbon, obtaining a silicon-carbon negative electrode material precursor with nano-silicon material deposited inside the porous carbon.

[0063] Step 4: Place the silicon-carbon negative electrode material precursor and asphalt in a mixer at a mass ratio of 9:1 and mix thoroughly. The mixer speed is 650 r / min. -1 , the mixing time is 20min. After fully mixing, transfer to the high temperature coating machine, the speed is 350r·min -1 , heat to 200℃, keep warm for 1h, then heat to 800℃, adjust the speed to 200r·min -1 , keep warm for 1.5h, N2 was used as protective gas during the coating process, and the gas flow rate was 30mL·min -1 , and obtain the final silicon-carbon negative electrode material.

[0064] The above silicon-carbon negative electrode material was mixed with a conductive agent and a binder in a ratio of 8:1:1 and deionized water was added to adjust the solid content to 25% to obtain a uniformly dispersed negative electrode slurry. The slurry was coated on a copper foil current collector and vacuum dried to obtain the final electrode. The silicon-carbon composite electrode was transferred to an argon-filled vacuum glove box to assemble a CR2032 button half-cell for testing. The specific performance was: at the first cycle current of 0.2A·g -1Under the test conditions, the first coulombic efficiency was 90.35%, and the first-week discharge capacity was 1582.48 mAh g -1 , then at a current of 1A·g -1 Under the condition of , the capacity is 797.18mAh·g after 100 cycles. -1 , the cycle stability performance is good.

[0065] Example 4 A method for preparing a silicon-carbon negative electrode material for chemical bonding-induced silane deposition comprises the following steps: Step 1: Sodium carboxymethyl cellulose, asphalt, graphite, ethanolamine, and polyvinyl pyrrolidone were dissolved in tetrahydrofuran at a mass ratio of 3:60:20:15:2 to obtain a mixed system with a solid content of 40% (the solid content is the total mass of the binder, asphalt, graphite, dopant, and dispersant), a tetrahydrofuran content of 59%, and a p-toluenesulfonic acid content of 1%. The mixed solution was sealed and ultrasonically dispersed for 30 minutes, and then heated on a heating plate at 70°C at 400 r / min. -1 The mixture is stirred at a stirring speed of 10000 rpm until the solvent is evaporated to dryness to obtain a porous carbon material precursor.

[0066] Step 2: Place the porous carbon material precursor in a tube furnace at 800°C and introduce CO2 at a gas flow rate of 50 mL min -1 , the corrosion time is 2h, and the modified porous carbon material is obtained.

[0067] Step 3: Place the obtained modified porous carbon material in a CVD furnace and introduce silane at a gas flow rate of 80 mL min -1 Silane deposition is performed on the porous carbon material at 650°C for 2.5 hours. The chemical bonding between silane and the dopant will induce the deposition of silane in the pores of the porous carbon, thereby obtaining a silicon-carbon negative electrode material precursor with nano-silicon material deposited inside the porous carbon.

[0068] Step 4: Place the silicon-carbon negative electrode material precursor and asphalt in a mixer at a mass ratio of 7:3 and mix thoroughly. The mixer speed is 450 r / min. -1 , the mixing time is 30min. After fully mixing, transfer to the high temperature coating machine, the speed is 300r·min -1 , heat to 200℃, keep warm for 1.5h, then heat to 80℃, adjust the speed to 200r·min -1 , keep warm for 1.5h, N2 was used as protective gas during the coating process, and the gas flow rate was 30mL·min -1 , and obtain the final silicon-carbon negative electrode material.

[0069] The above silicon-carbon negative electrode material was mixed with a conductive agent and a binder in a ratio of 8:1:1 and deionized water was added to adjust the solid content to 25% to obtain a uniformly dispersed negative electrode slurry. The slurry was coated on a copper foil current collector and vacuum dried to obtain the final electrode. The silicon-carbon composite electrode was transferred to an argon-filled vacuum glove box to assemble a CR2032 button half-cell for testing. The specific performance was: at the first cycle current of 0.2A·g -1 Under the test conditions, the first coulombic efficiency was 90.39%, and the first-week discharge capacity was 1703.94 mAh g -1 , then at a current of 1A·g -1 Under the condition of , the capacity is 896.45mAh·g after 100 cycles. -1 , the cycle stability performance is good.

[0070] Example 5 A method for preparing a silicon-carbon negative electrode material for chemical bonding-induced silane deposition comprises the following steps: Step 1: Dissolve polyacrylic acid, asphalt, graphite, ethanolamine, and polyvinyl pyrrolidone in tetrahydrofuran at a mass ratio of 3:60:20:15:2 to obtain a mixed system with a solid content of 40% (the solid content is the total mass of the binder, asphalt, graphite, dopant, and dispersant), a tetrahydrofuran content of 59%, and a p-toluenesulfonic acid content of 1%. After sealing the mixed system and ultrasonically dispersing it for 30 minutes, the system was heated on a heating plate at 70°C at 400 r / min. -1 The mixture is stirred at a stirring speed of 10000 rpm until the solvent is evaporated to dryness to obtain a porous carbon material precursor.

[0071] Step 2: Place the porous carbon material precursor in a 950°C tube furnace and introduce CO2 at a gas flow rate of 60 mL min -1 , the corrosion time is 1.5h, and the modified porous carbon material is obtained.

[0072] Step 3: Place the obtained modified porous carbon material in a CVD furnace and introduce silane at a gas flow rate of 90 mL min -1 Silane deposition is performed on the porous carbon material at 500°C for 1.5 hours. The chemical bonding between silane and the dopant will induce the deposition of silane in the pores of the porous carbon, thereby obtaining a silicon-carbon negative electrode material precursor with nano-silicon material deposited inside the porous carbon.

[0073] Step 4: Place the silicon-carbon negative electrode material precursor and asphalt in a mixer at a mass ratio of 9:1 and mix thoroughly. The mixer speed is 500 r / min. -1 , the mixing time is 40 min. After fully mixing, transfer to the high temperature coating machine, the speed is 350r·min -1 , heat to 200℃, keep warm for 1h, then heat to 750℃, adjust the speed to 200r·min-1 , keep warm for 1h, N2 was used as protective gas during the coating process, and the gas flow rate was 30mL·min -1 , and obtain the final silicon-carbon negative electrode material.

[0074] The above silicon-carbon negative electrode material was mixed with a conductive agent and a binder in a ratio of 8:1:1 and deionized water was added to adjust the solid content to 25% to obtain a uniformly dispersed negative electrode slurry. The slurry was coated on a copper foil current collector and vacuum dried to obtain the final electrode. The silicon-carbon composite electrode was transferred to an argon-filled vacuum glove box to assemble a CR2032 button half-cell for testing. The specific performance was: at the first cycle current of 0.2A·g -1 Under the test conditions, the first coulombic efficiency was 89.16%, and the first-week discharge capacity was 1493.28 mAh g -1 , then at a current of 1A·g -1 Under the condition of , the capacity is 732.84mAh·g after 100 cycles. -1 , the cycle stability performance is good.

[0075] Example 6 A method for preparing a silicon-carbon negative electrode material for chemical bonding-induced silane deposition comprises the following steps: Step 1: Dissolve polyvinyl alcohol, asphalt, graphite, ethanolamine, and polyvinyl pyrrolidone in tetrahydrofuran at a mass ratio of 3:30:50:15:2 to obtain a mixed system with a solid content of 35% (the solid content is the total mass of the binder, asphalt, graphite, dopant, and dispersant), a tetrahydrofuran content of 64%, and a p-toluenesulfonic acid content of 1%. After sealing the mixed system and ultrasonically dispersing it for 30 minutes, the system was heated on a heating plate at 70°C at 400 r / min. -1 The mixture is stirred at a stirring speed of 10000 rpm until the solvent is evaporated to dryness to obtain a porous carbon material precursor.

[0076] Step 2: Place the porous carbon material precursor in a tube furnace at 850°C and introduce CO2 at a gas flow rate of 80 mL min -1 , the corrosion time is 1.5h, and the modified porous carbon material is obtained.

[0077] Step 3: Place the obtained modified porous carbon material in a CVD furnace and introduce silane at a gas flow rate of 90 mL min -1 Silane deposition is performed on the porous carbon material at 600°C for 2 hours. The chemical bonding between silane and the dopant will induce silane to deposit in the pores of the porous carbon, obtaining a silicon-carbon negative electrode material precursor with nano-silicon material deposited inside the porous carbon.

[0078] Step 4: Place the silicon-carbon negative electrode material precursor and asphalt in a mixer at a mass ratio of 4:1 and mix thoroughly. The mixer speed is 500 r / min.-1 , The mixing time is 30 min. After thorough mixing, transfer it to a high-temperature coating machine with a rotation speed of 350 r·min -1 , heat to 230 °C, keep warm for 1 h, then raise the temperature to 800 °C, and adjust the rotation speed to 250 r·min -1 , keep warm for 1.5 h. During the coating process, N2 is used as the protective gas with a gas flow rate of 40 mL·min -1 , and the final silicon-carbon anode material is obtained.

[0079] Mix the above-mentioned silicon-carbon anode material with a conductive agent and a binder in a ratio of 8:1:1, and add deionized water to adjust the solid content to 25% to obtain a uniformly dispersed anode slurry. Coat it on a copper foil current collector and obtain the final electrode after vacuum drying. Transfer the silicon-carbon composite electrode to a vacuum glove box filled with argon to assemble a CR2032-type button half-cell for testing. Specifically, at the initial cycle current of 0.2 A·g -1 Under the test conditions, the initial Coulombic efficiency is 89.75%, and the initial cycle discharge capacity is 1567.28 mAh·g -1 , and then under the condition of a current of 1 A·g -1 , after 100 cycles, the capacity is 791.46 mAh·g -1 , and the cycle stability performance is good.

[0080] Comparative Example 1 Do not perform gas corrosion to create pores, including the following steps: Step 1: Dissolve sodium carboxymethylcellulose, asphalt, graphite, ethanolamine, and polyvinylpyrrolidone in tetrahydrofuran in a mass ratio of 3:35:50:10:2 to obtain a mixed system, where the solid content is 30% (the solid content is the total mass sum of the binder, asphalt, graphite, dopant, and dispersant), the content of tetrahydrofuran is 69%, and the content of p-toluenesulfonic acid is 1%. After sealing the mixed system and ultrasonically dispersing it for 30 min, stir it on a 70 °C heating table at a stirring speed of 350 r·min -1 until the solvent evaporates to dryness to obtain a carbon material precursor.

[0081] Step 2: Place the obtained carbon material precursor in a CVD furnace, introduce silane, and the gas flow rate is 80 mL·min -1 , and perform silane deposition on the porous carbon material at 600 °C for 2 h to obtain a silicon-carbon anode material precursor.

[0082] Step 3: Then place the silicon-carbon anode material precursor and asphalt in a mixer in a mass ratio of 4:1 and mix them thoroughly. The rotation speed of the mixer is 500 r·min -1 , and the mixing time is 30 min. After thorough mixing, transfer it to a high-temperature coating machine with a rotation speed of 250 r·min -1, heat it to 200 °C, keep it warm for 1 h, then raise the temperature to 650 °C, and adjust the rotation speed to 150 r·min -1 , keep it warm for 1 h, use N2 as the protective gas during the coating process, and the gas flow rate is 30 mL·min -1 , and obtain the final silicon-carbon anode material.

[0083] Mix the above-mentioned silicon-carbon anode material, conductive agent, and binder in a ratio of 8:1:1, add deionized water to adjust the solid content to 25%, obtain a uniformly dispersed anode slurry, coat it on a copper foil current collector, and after vacuum drying, obtain the final electrode. Transfer the silicon-carbon composite electrode to a vacuum glove box filled with argon to assemble a CR2032 type button half-cell for testing. Specifically, at the initial cycle current of 0.2 A·g -1 Under the test conditions, the initial Coulombic efficiency is 89.51%, and the initial week discharge capacity is 1646.74 mAh·g -1 , and then at a current of 1 A·g -1 Under the condition, the capacity after 100 cycles is 612.35 mAh·g -1 . The battery performance is much lower than that of the battery in Example 1, indicating that the gas corrosion pore formation in the present invention helps to improve the battery performance. This is because the pores of the porous carbon limit the expansion space of the nano-silicon particles and relieve the influence of silicon expansion on the electrode.

[0084] Comparative Example 2 It cannot induce the directional deposition of silane and includes the following steps: Step 1: Dissolve sodium carboxymethylcellulose, asphalt, graphite, and polyvinylpyrrolidone in tetrahydrofuran in a mass ratio of 3:40:55:2 to obtain a mixed system, where the solid content is 30% (the solid content is the total mass of the binder, asphalt, graphite, dopant, and dispersant), the content of tetrahydrofuran is 69%, and the content of p-toluenesulfonic acid is 1%. After sealing the mixed system and ultrasonic dispersing it for 30 min, stir it on a 70 °C heating table at a stirring speed of 350 r·min -1 until the solvent is evaporated to dryness to obtain a porous carbon material precursor.

[0085] Step 2: Place the porous carbon material precursor in a tube furnace at 800 °C, introduce CO2, and the gas flow rate is 50 mL·min -1 , and the corrosion time is 1 h to obtain a modified porous carbon material.

[0086] Step 3: Place the obtained modified porous carbon material in a CVD furnace, introduce silane, and the gas flow rate is 80 mL·min -1 , and carry out silane deposition on the porous carbon material at 600 °C for 2 h to obtain a silicon-carbon anode material precursor.

[0087] Step 4: Place the silicon-carbon negative electrode material precursor and asphalt in a mixer at a mass ratio of 4:1 and mix thoroughly. The mixer speed is 500 r / min. -1 , the mixing time is 30min. After fully mixing, transfer to the high temperature coating machine, the speed is 250r·min -1 , heat to 200℃, keep warm for 1h, then heat to 650℃, adjust the speed to 150r·min -1 , keep warm for 1h, N2 was used as protective gas during the coating process, and the gas flow rate was 30mL·min -1 , and obtain the final silicon-carbon negative electrode material.

[0088] The above silicon-carbon negative electrode material was mixed with a conductive agent and a binder in a ratio of 8:1:1 and deionized water was added to adjust the solid content to 25% to obtain a uniformly dispersed negative electrode slurry. The slurry was coated on a copper foil current collector and vacuum dried to obtain the final electrode. The silicon-carbon composite electrode was transferred to an argon-filled vacuum glove box to assemble a CR2032 button half-cell for testing. The specific performance was: at the first cycle current of 0.2A·g -1 Under the test conditions, the first coulombic efficiency was 90.15%, and the first-week discharge capacity was 1584.37 mAh g -1 , then at a current of 1A·g -1 Under the condition of , the capacity is 702.64mAh·g after 100 cycles. -1 The battery performance is much lower than that of the battery in Example 1, indicating that the use of a dopant containing an alcoholic hydroxyl group in the present invention to induce silane deposition helps improve battery performance. This is because the induction effect enables silane to preferentially deposit in the pores of the porous carbon, utilizing the pores of the porous carbon to limit the expansion of the nano-silicon particles. At the same time, the chemical bonding between the nano-silicon particles and the matrix material is also conducive to the diffusion and transmission of lithium ions. The nitrogen element in the dopant helps to improve the surface roughness of the porous carbon material, making the deposition of silicon particles more uniform.

[0089] Comparative Example 3 Without asphalt coating, the following steps are included: Step 1: Sodium carboxymethyl cellulose, asphalt, graphite, ethanolamine, and polyvinyl pyrrolidone were dissolved in tetrahydrofuran at a mass ratio of 3:35:50:10:2 to obtain a mixed system with a solid content of 30% (the solid content is the total mass of the binder, asphalt, graphite, dopant, and dispersant), a tetrahydrofuran content of 69%, and a p-toluenesulfonic acid content of 1%. The mixed system was sealed and ultrasonically dispersed for 30 minutes, and then heated on a heating plate at 70°C at 350 r / min. -1 The mixture is stirred at a stirring speed of 10000 rpm until the solvent is evaporated to dryness to obtain a porous carbon material precursor.

[0090] Step 2: Place the porous carbon material precursor in a tube furnace at 800 °C, introduce CO2 with a gas flow rate of 50 mL·min -1 , and corrode for 1 h to obtain a modified porous carbon material.

[0091] Step 3: Place the obtained modified porous carbon material in a CVD furnace, introduce silane with a gas flow rate of 80 mL·min -1 , and perform silane deposition on the porous carbon material at 600 °C for 2 h. The chemical bonding between silane and the dopant will induce silane to deposit inside the pores of the porous carbon, obtaining a precursor of a silicon-carbon negative electrode material with nano-silicon material deposited inside the porous carbon.

[0092] Step 4: Then transfer the precursor of the silicon-carbon negative electrode material to a high-temperature coating machine with a rotation speed of 250 r·min -1 , heat to 200 °C, keep warm for 1 h, then raise the temperature to 650 °C, and adjust the rotation speed to 150 r·min -1 , keep warm for 1 h. During the process, N2 is used as a protective gas with a gas flow rate of 30 mL·min -1 to obtain the final silicon-carbon negative electrode material.

[0093] Mix the above-mentioned silicon-carbon negative electrode material, conductive agent, and binder in a ratio of 8:1:1, add deionized water to adjust the solid content to 25% to obtain a uniformly dispersed negative electrode slurry. Coat it on a copper foil current collector and obtain the final electrode after vacuum drying. Transfer the silicon-carbon composite electrode to a vacuum glove box filled with argon to assemble a CR2032 type button half-cell for testing. Specifically: under the test condition of a first-cycle current of 0.2 A·g -1 , the first Coulombic efficiency is 87.25%, and the first-week discharge capacity is 1819.57 mAh·g -1 . Subsequently, under the condition of a current of 1 A·g -1 , the capacity after 100 cycles is 774.53 mAh·g -1 . The battery performance is much lower than that of the battery in Example 1, indicating that coating the asphalt carbon layer in the present invention is beneficial to improving the stability of the battery.

[0094] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and its equivalent technologies, these changes and modifications are also intended to be included.

Claims

1. A preparation method of a silicon-carbon anode material induced by chemical bond-induced silane deposition, characterized in that, It includes the following steps: Put the binder, asphalt, graphite, dopant and dispersant into a solvent to obtain a mixed system. After uniform dispersion, remove the solvent to obtain a precursor of porous carbon material; wherein, the dopant contains alcohol hydroxyl groups and amino groups; Put the precursor of porous carbon material into a tubular furnace, introduce CO2, and carry out gas corrosion and pore formation on the precursor of porous carbon material to obtain a modified porous carbon material; Put the modified porous carbon material into a CVD furnace, introduce silane, and the chemical bonding between the alcohol hydroxyl groups in the dopant and silane induces the preferential deposition of silane in the pores of the porous carbon to obtain a precursor of silicon-carbon anode material; Mix the precursor of silicon-carbon anode material and asphalt first, then add them into a high-temperature coating furnace for asphalt coating and carbonization treatment to obtain the final silicon-carbon anode material.

2. The preparation method according to claim 1, wherein, The dopant is ethanolamine, methylethanolamine, N,N-dimethylpropanolamine, N,N-diethylpropanolamine, 2-aminobutanol, isobutanolamine or dibutanolamine.

3. The preparation method according to claim 1, wherein In the mixture composed of the binder, asphalt, graphite, dopant and dispersant, the mass percentage of the binder is 1% - 3%, the mass percentage of asphalt is 30% - 60%, the mass percentage of graphite is 20% - 50%, the mass percentage of the dopant is 10% - 20%, and the mass percentage of the dispersant is 1% - 2%, with a total of 100%.

4. The preparation method according to claim 1, wherein During the pore formation process by gas corrosion, the temperature is 700°C to 1000°C, the time is 1h to 2.5h, and the CO2 flow rate is 40 mL·min -1 ~80 mL·min -1 .

5. The preparation method according to claim 1, characterized in that, During the silane deposition process, the temperature is 500°C to 700°C, the time is 1 h to 3 h, and the flow rate of the silicon source is 50 mL·min -1 ~100 mL·min -1 .

6. The preparation method according to claim 1, characterized in that, In the mixture composed of the precursor of silicon-carbon anode material and asphalt, the mass percentage of the precursor of silicon-carbon anode material is 60% - 90%, and the balance is asphalt, with a total of 100%.

7. The preparation method according to claim 1, characterized in that During the asphalt coating and carbonization process, under a protective gas atmosphere, the temperature in the first half is 150°C to 300°C, the heat preservation time is 1h to 1.5h, and the rotation speed is 250 r·min -1 ~400 r·min -1 , the temperature in the second half is 600°C to 800°C, the heat preservation time is 0.5h to 1.5h, and the rotation speed is 100 r·min -1 ~250 r·min -1 .

8. The preparation method according to claim 1, characterized in that, When preparing the precursor of porous carbon material, in the mixed system, the total mass fraction of the binder, asphalt, graphite, dopant and dispersant is 30% - 60%.

9. A silicon-carbon anode material induced by chemical bonding for silane deposition, characterized in that, Prepared by the preparation method according to any one of claims 1 - 8.

10. The silicon-carbon anode material with chemically bonded induced silane deposition according to claim 9, characterized in that, Based on the porous carbon material as the matrix, silicon nanoparticles are induced to deposit by chemical bonding inside the pores, and the outermost layer of the matrix is wrapped with an asphalt carbon layer.

Images