Silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution and preparation method thereof

Abstract

The invention discloses a preparation method of a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution, which comprises the following steps: designing a multi-layer coating structure with gradient carbon nanotube distribution, and combining the conductivity and flexibility of polyaniline; the gradient carbon nanotube distributed silicon-carbon polyaniline composite material with high capacity, low expansion and excellent cycle stability is provided, the composite material is applied to a high-capacity negative electrode of a lithium ion battery, and the bottleneck problems of low first efficiency and short cycle life caused by volume expansion and poor conductivity of a silicon-based negative electrode are systematically solved.

Description

Technical Field

[0001] This invention relates to the field of battery material preparation, and more specifically, to a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution and its preparation method. Background Technology

[0002] Silicon-based anode materials have become a research hotspot due to their high theoretical capacity (4200 mAh / g), but they suffer from significant volume expansion (>300%) and poor conductivity. Traditional silicon-carbon composites rely on high carbon nanotube (CNT) content to improve conductivity, but the high cost and uneven distribution of CNTs can lead to interfacial stress concentration, which in turn reduces cycle performance. For example, in current technologies, the carbon nanotube content in coating processes is typically 0.2%, which not only increases production costs but also affects the bonding strength of the silicon-carbon interface due to excessive carbon nanotube agglomeration. For example, Chinese patent application number CN201810794569.8 discloses a method for preparing a conductive polymer-coated silicon composite carbon nanotube anode material. The method involves in-situ polymerization of submicron or nano-sized silicon on the surface without the use of organic solvents, and simultaneous doping with conductive polymer polyaniline. The coating of polyaniline effectively suppresses the volume expansion of silicon and provides good conductivity to silicon. Then, by utilizing the π-π conjugation effect of polyaniline and carbon nanotubes, pre-dispersed carbon nanotubes are added, so that the polyaniline-coated silicon particles are uniformly dispersed and firmly fixed in the carbon nanotube dispersion system. For example, Chinese patent application CN201710542784.4 discloses a composite conductive and thermally conductive particle made of polyaniline-encapsulated silicon carbide-multi-walled carbon nanotubes and its preparation method. The method is characterized by: immersing silicon carbide in hydrofluoric acid solution, rinsing and drying with acetone, and calcining to obtain thermally conductive microparticles; mixing and hydrolyzing a silane coupling agent, ethanol, and water, and then adding the mixture to the thermally conductive microparticles to obtain surface-treated thermally conductive microparticles; immersing carbon fibers in acetone and then in concentrated nitric acid to obtain surface-oxidized carbon fibers; adding hydrochloric acid solution to multi-walled carbon nanotubes and ultrasonically homogenizing the dispersion; adding hydrochloric acid solution to ammonium persulfate and stirring to dissolve it to obtain an ammonium persulfate hydrochloric acid solution; adding aniline monomer to the multi-walled carbon nanotube dispersion, ultrasonically treating it with stirring, placing it in an ice-water bath for magnetic stirring, slowly adding the ammonium persulfate hydrochloric acid solution, and after the addition is complete, adding the thermally conductive microparticles, magnetically stirring the reaction, and mixing with the carbon fibers to obtain composite conductive microparticles. However, the existing technology still has the following technical problems that urgently need to be solved: the high carbon nanotube content leads to increased material costs; the system is prone to agglomeration, which in turn exacerbates the structural damage caused by volume expansion; and it is difficult to balance the interfacial conductivity and mechanical stability between components. Summary of the Invention

[0003] In order to solve one of the above problems, this invention provides a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution and its preparation method, the specific technical solution of which is as follows:

[0004] A method for preparing silicon-carbon polyaniline composite materials based on gradient carbon nanotube distribution, the method comprising the following steps:

[0005] The resin material is dispersed in deionized water, a curing agent is added under stirring, and the material is cured, centrifuged, dried and carbonized, then pulverized to obtain carbonized material.

[0006] The carbonized material is activated and cooled to obtain a porous carbon material.

[0007] The porous carbon material was placed in a reaction vessel, first purged with nitrogen, then heated to 300℃~500℃ at a heating rate of 5℃ / min~10℃ / min, and a mixture of silane and argon was introduced for deposition treatment for 10h~30h. Then, the temperature was raised to 500℃~700℃ at a heating rate of 5℃ / min~15℃ / min, and a mixture of acetylene and argon was introduced for encapsulation treatment for 8h~12h to obtain a silicon-carbon composite material.

[0008] The silicon-carbon composite material was pre-dispersed, and then modified by adding silane coupling agent and carbon nanotubes to obtain a modified silicon-carbon composite material.

[0009] Aniline, ammonium persulfate and hydrochloric acid were added to the modified silicon-carbon composite material, and in-situ polymerization was initiated in an ice-water bath. After a first stirring treatment, washing and annealing treatment were performed to obtain a silicon-carbon polyaniline composite material.

[0010] Carboxymethyl cellulose and carbon black were added to a mixer for a second stirring process. Then, carbon nanotubes, modified silicon-carbon composite material, and deionized water were added for a third stirring process. Styrene-butadiene rubber was then added for a fourth stirring process. The mixture was then sieved and air bubbles were removed to obtain a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution.

[0011] Furthermore, the resin material is phenolic resin; the mass ratio of the phenolic resin to deionized water is 1:(3-9).

[0012] Furthermore, the curing agent is a citric acid solution;

[0013] The mass ratio of citric acid to phenolic resin is (0.03-0.1):1;

[0014] In the citric acid solution, the mass ratio of citric acid to deionized water is 1:(2-20).

[0015] Furthermore, the carbonization process is as follows: first, the temperature is increased to 600℃ at a heating rate of 5℃ / min and held for 2h to 6h, then the temperature is increased to 1000℃ to 1050℃ and held for 6h to 10h.

[0016] Further, the activation treatment is as follows: after the carbonized material is purged with nitrogen to remove oxygen, it is heated to 700℃~1200℃ at a heating rate of 5℃ / min, nitrogen is introduced and kept at this temperature for 0.5h~2h, and then carbon dioxide is introduced for activation treatment for 10h~30h.

[0017] Furthermore, the flow rate of the nitrogen gas is (50-500) mL / min; the flow rate of the carbon dioxide gas is (100-800) mL / min.

[0018] Furthermore, in the mixture of silane and argon, the volume ratio of silane to argon is (1-3):1; the flow rate of the silane is (10-40) mL / min.

[0019] Furthermore, in the mixture of acetylene and argon, the volume ratio of acetylene to argon is (1-3):1; and the flow rate of acetylene is (10-40) mL / min.

[0020] Furthermore, the mass ratio of the silicon-carbon composite material, silane coupling agent, and carbon nanotubes is 1:(0.005~0.02):(0.00001~0.0001).

[0021] The present invention also provides a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution, wherein the silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution is obtained by the preparation method described above.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. This invention provides a silicon-carbon-polyaniline composite material with gradient carbon nanotube distribution, which combines the conductivity and flexibility of polyaniline with a multilayer coating structure of gradient carbon nanotube distribution, and has high capacity, low expansion and excellent cycle stability. When applied to the high-capacity anode of lithium-ion batteries, it systematically solves the bottleneck problems of low initial efficiency and short cycle life of silicon-based anodes caused by volume expansion and poor conductivity.

[0024] 2. This invention prepares porous carbon with adjustable pore size to ensure a high specific surface area and introduces silicon source gas to undergo decomposition and deposition reactions inside the porous carbon, thereby achieving uniform loading of silicon in the porous carbon pore structure. Subsequently, under the action of silane coupling agent and polyaniline, an excellent encapsulation effect is formed, which can significantly improve the electrical conductivity, mechanical properties and cycle stability of silicon-carbon polyaniline composite materials. Attached Figure Description

[0025] Figure 1 Schematic diagrams of the initial coulombic efficiency of Examples 1-3 and Comparative Examples 1-3;

[0026] Figure 2Schematic diagrams of charging cycle life curves for Examples 1-3 and Comparative Examples 1-3. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] A method for preparing a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution according to an embodiment of the present invention includes the following steps:

[0030] The resin material is dispersed in deionized water, a curing agent is added under stirring, and the material is cured, centrifuged, dried and carbonized, then pulverized to obtain carbonized material.

[0031] The carbonized material is activated and cooled to obtain a porous carbon material.

[0032] The porous carbon material was placed in a reaction vessel, first purged with nitrogen, then heated to 300℃~500℃ at a heating rate of 5℃ / min~10℃ / min, and a mixture of silane and argon was introduced for deposition treatment for 10h~30h. Then, the temperature was raised to 500℃~700℃ at a heating rate of 5℃ / min~15℃ / min, and a mixture of acetylene and argon was introduced for encapsulation treatment for 8h~12h to obtain a silicon-carbon composite material.

[0033] The silicon-carbon composite material was pre-dispersed, and then modified by adding silane coupling agent and carbon nanotubes to obtain a modified silicon-carbon composite material.

[0034] Aniline, ammonium persulfate and hydrochloric acid were added to the modified silicon-carbon composite material, and in-situ polymerization was initiated in an ice-water bath. After a first stirring treatment, washing and annealing treatment were performed to obtain a silicon-carbon polyaniline composite material.

[0035] Carboxymethyl cellulose and carbon black were added to a mixer for a second stirring process. Then, carbon nanotubes, modified silicon-carbon composite material, and deionized water were added for a third stirring process. Styrene-butadiene rubber was then added for a fourth stirring process. The mixture was then sieved and air bubbles were removed to obtain a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution.

[0036] In one embodiment, the resin material is phenolic resin; the mass ratio of the phenolic resin to deionized water is 1:(3-9).

[0037] In one embodiment, the curing agent is a citric acid solution;

[0038] The mass ratio of citric acid to phenolic resin is (0.03-0.1):1;

[0039] In the citric acid solution, the mass ratio of citric acid to deionized water is 1:(2-20).

[0040] In one embodiment, the carbonization process is as follows: first, the temperature is increased to 600°C at a heating rate of 5°C / min and held for 2h to 6h, then the temperature is increased to 1000°C to 1050°C and held for 6h to 10h.

[0041] In one embodiment, the activation treatment is as follows: after the carbonized material is purged with nitrogen to remove oxygen, it is heated to 700℃~1200℃ at a heating rate of 5℃ / min, nitrogen is introduced and kept at this temperature for 0.5h~2h, and then carbon dioxide is introduced for activation treatment for 10h~30h.

[0042] In one embodiment, the flow rate of nitrogen is (50-500) mL / min; the flow rate of carbon dioxide is (100-800) mL / min.

[0043] In one embodiment, the volume ratio of silane to argon in the mixture is (1-3):1; the flow rate of the silane is (10-40) mL / min.

[0044] In one embodiment, the volume ratio of acetylene to argon in the mixture is (1-3):1; and the flow rate of acetylene is (10-40) mL / min.

[0045] In one embodiment, the mass ratio of the silicon-carbon composite material, the silane coupling agent, and the carbon nanotubes is 1:(0.005-0.02):(0.00001-0.0001).

[0046] In one embodiment, the pre-dispersion is performed by adding the silicon-carbon composite material to deionized water and ultrasonically treating it at a power of 400W for 5 minutes.

[0047] In one embodiment, the mass ratio of the silicon-carbon composite material to deionized water is (5-15):(50-100).

[0048] In one embodiment, the modification treatment conditions are: power of 500W to 600W and time of 10min to 15min.

[0049] In one embodiment, the mass ratio of the modified silicon-carbon composite material, aniline, ammonium persulfate, and hydrochloric acid is 1-2:0.5:0.5:1-2, preferably 1:0.5:0.5:1.

[0050] In one embodiment, the conditions for the first stirring treatment are: a stirring rate of 500 r / min to 1500 r / min and a time of 12 h to 24 h.

[0051] In one embodiment, the mass ratio of the modified silicon-carbon composite material, carbon black, carbon nanotubes, sodium carboxymethyl cellulose, and styrene-butadiene rubber is (50-65):(15-20):(0-0.3):(5-10):(5.7-9.9), preferably 60:20:0.2:10:9.8.

[0052] In one embodiment, the conditions for the second stirring treatment are: stirring for 30 min to 90 min at a revolution speed of 10 r / min to 40 r / min and a rotation speed of 1000 r / min to 4000 r / min.

[0053] In one embodiment, the conditions for the third stirring treatment are: stirring for 30 min to 90 min at a revolution speed of 30 r / min to 60 r / min and a rotation speed of 1500 r / min to 4000 r / min.

[0054] In one embodiment, the conditions for the fourth stirring process are: stirring for 10 min to 60 min at a revolution speed of 10 r / min to 20 r / min and a rotation speed of 1000 r / min to 4000 r / min.

[0055] In one embodiment, the present invention also provides a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution, wherein the silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution is obtained by the preparation method described above.

[0056] The silicon-carbon polyaniline composite material obtained by the above scheme has high capacity, low expansion and excellent cycle stability, and has better application in lithium-ion batteries.

[0057] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0058] Example 1:

[0059] A method for preparing a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution, the method comprising the following steps:

[0060] 100g of phenolic material was dispersed in 500g of deionized water. 114mL of citric acid solution was added under stirring to induce coagulation (the citric acid solution was obtained by dissolving 12g of citric acid in 228mL of deionized water). Then, the material was centrifuged, vacuum dried, pulverized, and subjected to two-stage carbonization in a tube furnace: first, the temperature was increased to 600℃ at 5℃ / min and held for 1h, then increased to 1050℃ and held for 8h. The material was then pulverized to 7-8μm using an air jet mill to obtain the carbonized material.

[0061] 200g of the carbonized material was fed into the equipment. After nitrogen purging and deoxygenation, the temperature was increased to 1000℃ at 5℃ / min. Nitrogen gas was first introduced (flow rate 100mL / min) and kept at this temperature for 1 hour. Then, carbon dioxide was introduced (flow rate 400mL / min) for activation treatment for 20 hours to obtain porous carbon material. The specific surface area of ​​the porous carbon material was 1900m². 2 / g, with a microporosity of 92%;

[0062] 200g of the porous carbon material was placed in a reaction vessel, purged with nitrogen, and then heated to 460°C at a rate of 5°C / min. A mixture of silane and argon (silane:argon volume ratio of 1:1, silane flow rate of 30mL / min) was introduced, and the mixture was deposited for 12h. Then, the mixture was heated to 600°C at a rate of 10°C / min, and a mixture of acetylene and argon (acetylene:argon volume ratio of 1:1, acetylene flow rate of 30mL / min) was introduced, and the mixture was encapsulated for 12h to obtain a silicon-carbon composite material.

[0063] 10g of the silicon-carbon composite material was added to 50g of deionized water and ultrasonically treated for 5min at 400W power to avoid sudden breakage of agglomerates leading to excessively high local concentrations. Then, 0.1g of silane coupling agent and 0.0083g of carbon nanotubes were added and treated for 10min at 600W power. Then, 5g of aniline, 5g of ammonium persulfate and 10g of hydrochloric acid were added and placed in an ice-water bath to initiate in-situ polymerization. The mixture was treated at 800r / min for 12h. After washing and annealing, the silicon-carbon polyaniline composite material was obtained.

[0064] Add 10g of carboxymethyl cellulose and 20g of carbon black to a mixer and stir for 60min at a revolution speed of 20r / min and a rotation speed of 3000r / min. Then add 0.1g of carbon nanotubes and 60.1g of modified silicon-carbon composite material, and add deionized water to adjust the solid content to 20%. Stir for 60min at a revolution speed of 30r / min and a rotation speed of 3000r / min. Then add 9.8g of styrene-butadiene rubber and stir for 10min at a revolution speed of 10r / min and a rotation speed of 1000r / min. Sieve and remove air bubbles to obtain silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution.

[0065] Example 2:

[0066] A method for preparing a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution, the method comprising the following steps:

[0067] 100g of phenolic material was dispersed in 500g of deionized water. 114mL of citric acid solution was added under stirring to induce coagulation (the citric acid solution was obtained by dissolving 12g of citric acid in 228mL of deionized water). Then, the material was centrifuged, vacuum dried, pulverized, and subjected to two-stage carbonization in a tube furnace: first, the temperature was increased to 600℃ at 5℃ / min and held for 1h, then increased to 1050℃ and held for 8h. The material was then pulverized to 7-8μm using an air jet mill to obtain the carbonized material.

[0068] 200g of the carbonized material was fed into the equipment. After nitrogen purging and deoxygenation, the temperature was increased to 1000℃ at 5℃ / min. Nitrogen gas was first introduced (flow rate 100mL / min) and kept at this temperature for 1 hour. Then, carbon dioxide was introduced (flow rate 400mL / min) for activation treatment for 20 hours to obtain porous carbon material. The specific surface area of ​​the porous carbon material was 1900m². 2 / g, with a microporosity of 92%;

[0069] 200g of the porous carbon material was placed in a reaction vessel, purged with nitrogen, and then heated to 460°C at a rate of 5°C / min. A mixture of silane and argon (silane:argon volume ratio of 1:1, silane flow rate of 30mL / min) was introduced, and the mixture was deposited for 12h. Then, the mixture was heated to 600°C at a rate of 10°C / min, and a mixture of acetylene and argon (acetylene:argon volume ratio of 1:1, acetylene flow rate of 30mL / min) was introduced, and the mixture was encapsulated for 12h to obtain a silicon-carbon composite material.

[0070] 10g of the silicon-carbon composite material was added to 50g of deionized water and ultrasonically treated for 5min at 400W power to avoid sudden breakage of agglomerates leading to excessively high local concentrations. Then, 0.1g of silane coupling agent and 0.0083g of carbon nanotubes were added and treated for 10min at 600W power. Then, 5g of aniline, 5g of ammonium persulfate and 10g of hydrochloric acid were added and placed in an ice-water bath to initiate in-situ polymerization. The mixture was treated at 800r / min for 12h. After washing and annealing, the silicon-carbon polyaniline composite material was obtained.

[0071] Add 10g of carboxymethyl cellulose and 20g of carbon black to a mixer and stir for 60min at a revolution speed of 20r / min and a rotation speed of 3000r / min. Then add 0.15g of carbon nanotubes and 60.05g of modified silicon-carbon composite material, and add deionized water to adjust the solid content to 20%. Stir for 60min at a revolution speed of 30r / min and a rotation speed of 3000r / min. Then add 9.8g of styrene-butadiene rubber and stir for 10min at a revolution speed of 10r / min and a rotation speed of 1000r / min. Sieve and remove air bubbles to obtain silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution.

[0072] Example 3:

[0073] A method for preparing a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution, the method comprising the following steps:

[0074] 100g of phenolic material was dispersed in 500g of deionized water. 114mL of citric acid solution was added under stirring to induce coagulation (the citric acid solution was obtained by dissolving 12g of citric acid in 228mL of deionized water). Then, the material was centrifuged, vacuum dried, pulverized, and subjected to two-stage carbonization in a tube furnace: first, the temperature was increased to 600℃ at 5℃ / min and held for 1h, then increased to 1050℃ and held for 8h. The material was then pulverized to 7-8μm using an air jet mill to obtain the carbonized material.

[0075] 200g of the carbonized material was fed into the equipment. After nitrogen purging and deoxygenation, the temperature was increased to 1000℃ at 5℃ / min. Nitrogen gas was first introduced (flow rate 100mL / min) and kept at this temperature for 1 hour. Then, carbon dioxide was introduced (flow rate 400mL / min) for activation treatment for 20 hours to obtain porous carbon material. The specific surface area of ​​the porous carbon material was 1900m². 2 / g, with a microporosity of 92%;

[0076] 200g of the porous carbon material was placed in a reaction vessel, purged with nitrogen, and then heated to 460°C at a rate of 5°C / min. A mixture of silane and argon (silane:argon volume ratio of 1:1, silane flow rate of 30mL / min) was introduced, and the mixture was deposited for 12h. Then, the mixture was heated to 600°C at a rate of 10°C / min, and a mixture of acetylene and argon (acetylene:argon volume ratio of 1:1, acetylene flow rate of 30mL / min) was introduced, and the mixture was encapsulated for 12h to obtain a silicon-carbon composite material.

[0077] 10g of the silicon-carbon composite material was added to 50g of deionized water and ultrasonically treated for 5min at 400W power to avoid sudden breakage of agglomerates leading to excessively high local concentrations. Then, 0.1g of silane coupling agent and 0.0083g of carbon nanotubes were added and treated for 10min at 600W power. Then, 5g of aniline, 5g of ammonium persulfate and 10g of hydrochloric acid were added and placed in an ice-water bath to initiate in-situ polymerization. The mixture was treated at 800r / min for 12h. After washing and annealing, the silicon-carbon polyaniline composite material was obtained.

[0078] Add 10g of carboxymethyl cellulose and 20g of carbon black to a mixer and stir for 60min at a revolution speed of 20r / min and a rotation speed of 3000r / min. Then add 0g of carbon nanotubes and 60.2g of modified silicon-carbon composite material, and add deionized water to adjust the solid content to 20%. Stir for 60min at a revolution speed of 30r / min and a rotation speed of 3000r / min. Then add 9.8g of styrene-butadiene rubber and stir for 10min at a revolution speed of 10r / min and a rotation speed of 1000r / min. Sieve and remove air bubbles to obtain silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution.

[0079] Comparative Example 1:

[0080] A method for preparing a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution, the method comprising the following steps:

[0081] 100g of phenolic material was dispersed in 500g of deionized water. 114mL of citric acid solution was added under stirring to induce coagulation (citric acid solution was obtained by dissolving 12g of citric acid in 228mL of deionized water). Then, the material was centrifuged, vacuum dried, pulverized, and subjected to two-stage carbonization in a tube furnace: first, the temperature was raised to 600℃ at 5℃ / min and held for 1h, then raised to 1050℃ and held for 8h. The material was then pulverized to 7-8μm using an air jet mill to obtain the carbonized material.

[0082] 200g of the carbonized material was fed into the equipment. After nitrogen purging and deoxygenation, the temperature was increased to 1000℃ at 5℃ / min. Nitrogen gas was first introduced (flow rate 100mL / min) and kept at this temperature for 1 hour. Then, carbon dioxide was introduced (flow rate 400mL / min) for activation treatment for 20 hours to obtain porous carbon material. The specific surface area of ​​the porous carbon material was 1900m². 2 / g, with a microporosity of 92%;

[0083] 200g of the porous carbon material was placed in a reaction vessel, purged with nitrogen, and then heated to 460°C at a rate of 5°C / min. A mixture of silane and argon (silane:argon volume ratio of 1:1, silane flow rate of 30mL / min) was introduced, and the mixture was deposited for 12h. Then, the mixture was heated to 600°C at a rate of 10°C / min, and a mixture of acetylene and argon (acetylene:argon volume ratio of 1:1, acetylene flow rate of 30mL / min) was introduced, and the mixture was encapsulated for 12h to obtain a silicon-carbon composite material.

[0084] 10g of the silicon-carbon composite material was added to 50g of deionized water and ultrasonically treated for 5min at 400W power to avoid sudden breakage of agglomerates leading to excessively high local concentrations. Then, 0.1g of silane coupling agent was added and treated for 10min at 600W power. Next, 5g of aniline, 5g of ammonium persulfate and 10g of hydrochloric acid were added and placed in an ice-water bath to initiate in-situ polymerization. The mixture was treated at 800r / min for 12h. After washing and annealing, the silicon-carbon polyaniline composite material was obtained.

[0085] Add 10g of carboxymethyl cellulose and 20g of carbon black to a mixer and stir for 60min at a revolution speed of 20r / min and a rotation speed of 3000r / min. Then add 0.2g of carbon nanotubes and 60g of modified silicon-carbon composite material, and add deionized water to adjust the solid content to 20%. Stir for 60min at a revolution speed of 30r / min and a rotation speed of 3000r / min. Then add 9.8g of styrene-butadiene rubber and stir for 10min at a revolution speed of 10r / min and a rotation speed of 1000r / min. Sieve and remove air bubbles to obtain silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution.

[0086] Comparative Example 2:

[0087] A method for preparing a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution, the method comprising the following steps:

[0088] 100g of phenolic material was dispersed in 500g of deionized water. 114mL of citric acid solution was added under stirring to induce coagulation (citric acid solution was obtained by dissolving 12g of citric acid in 228mL of deionized water). Then, the material was centrifuged, vacuum dried, pulverized, and subjected to two-stage carbonization in a tube furnace: first, the temperature was raised to 600℃ at 5℃ / min and held for 1h, then raised to 1050℃ and held for 8h. The material was then pulverized to 7-8μm using an air jet mill to obtain the carbonized material.

[0089] 200g of the carbonized material was fed into the equipment. After nitrogen purging and deoxygenation, the temperature was increased to 1000℃ at 5℃ / min. Nitrogen gas was first introduced (flow rate 100mL / min) and kept at this temperature for 1 hour. Then, carbon dioxide was introduced (flow rate 400mL / min) for activation treatment for 20 hours to obtain porous carbon material. The specific surface area of ​​the porous carbon material was 1900m². 2 / g, with a microporosity of 92%;

[0090] 200g of the porous carbon material was placed in a reaction vessel, purged with nitrogen, and then heated to 460°C at a rate of 5°C / min. A mixture of silane and argon (silane:argon volume ratio of 1:1, silane flow rate of 30mL / min) was introduced, and the mixture was deposited for 12h. Then, the mixture was heated to 600°C at a rate of 10°C / min, and a mixture of acetylene and argon (acetylene:argon volume ratio of 1:1, acetylene flow rate of 30mL / min) was introduced, and the mixture was encapsulated for 12h to obtain a silicon-carbon composite material.

[0091] 10g of the silicon-carbon composite material was added to 50g of deionized water and ultrasonically treated for 5min at 400W power to avoid sudden breakage of agglomerates leading to excessively high local concentrations. Then, 0.1g of silane coupling agent was added and treated for 10min at 600W power. Next, 5g of aniline, 5g of ammonium persulfate and 10g of hydrochloric acid were added and placed in an ice-water bath to initiate in-situ polymerization. The mixture was treated at 800r / min for 12h. After washing and annealing, the silicon-carbon polyaniline composite material was obtained.

[0092] Add 10g of carboxymethyl cellulose and 20g of carbon black to a mixer and stir for 60min at a revolution speed of 20r / min and a rotation speed of 3000r / min. Then add 0.1g of carbon nanotubes and 60.1g of modified silicon-carbon composite material, and add deionized water to adjust the solid content to 20%. Stir for 60min at a revolution speed of 30r / min and a rotation speed of 3000r / min. Then add 9.8g of styrene-butadiene rubber and stir for 10min at a revolution speed of 10r / min and a rotation speed of 1000r / min. Sieve and remove air bubbles to obtain silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution.

[0093] Comparative Example 3:

[0094] A method for preparing a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution, the method comprising the following steps:

[0095] 100g of phenolic material was dispersed in 500g of deionized water. 114mL of citric acid solution was added under stirring to induce coagulation (citric acid solution was obtained by dissolving 12g of citric acid in 228mL of deionized water). Then, the material was centrifuged, vacuum dried, pulverized, and subjected to two-stage carbonization in a tube furnace: first, the temperature was raised to 600℃ at 5℃ / min and held for 1h, then raised to 1050℃ and held for 8h. The material was then pulverized to 7-8μm using an air jet mill to obtain the carbonized material.

[0096] 200g of the carbonized material was fed into the equipment. After nitrogen purging and deoxygenation, the temperature was increased to 1000℃ at 5℃ / min. Nitrogen gas was first introduced (flow rate 100mL / min) and kept at this temperature for 1 hour. Then, carbon dioxide was introduced (flow rate 400mL / min) for activation treatment for 20 hours to obtain porous carbon material. The specific surface area of ​​the porous carbon material was 1900m². 2 / g, with a microporosity of 92%;

[0097] 200g of the porous carbon material was placed in a reaction vessel, purged with nitrogen, and then heated to 460°C at a rate of 5°C / min. A mixture of silane and argon (silane:argon volume ratio of 1:1, silane flow rate of 30mL / min) was introduced, and the mixture was deposited for 12h. Then, the mixture was heated to 600°C at a rate of 10°C / min, and a mixture of acetylene and argon (acetylene:argon volume ratio of 1:1, acetylene flow rate of 30mL / min) was introduced, and the mixture was encapsulated for 12h to obtain a silicon-carbon composite material.

[0098] 10g of the silicon-carbon composite material was added to 50g of deionized water and ultrasonically treated for 5min at 400W power to avoid sudden breakage of agglomerates leading to excessively high local concentrations. Then, 0.1g of silane coupling agent was added and treated for 10min at 600W power. Next, 5g of aniline, 5g of ammonium persulfate and 10g of hydrochloric acid were added and placed in an ice-water bath to initiate in-situ polymerization. The mixture was treated at 800r / min for 12h. After washing and annealing, the silicon-carbon polyaniline composite material was obtained.

[0099] Add 10g of carboxymethyl cellulose and 20g of carbon black to a mixer and stir for 60min at a revolution speed of 20r / min and a rotation speed of 3000r / min. Then add 60.2g of modified silicon-carbon composite material and deionized water (adjust the solid content to 20% by deionization) and stir for 60min at a revolution speed of 30r / min and a rotation speed of 3000r / min. Then add 9.8g of styrene-butadiene rubber and stir for 10min at a revolution speed of 10r / min and a rotation speed of 1000r / min. Sieve the mixture and remove air bubbles to obtain a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution.

[0100] Figure 1 Schematic diagrams of the initial coulombic efficiency of Examples 1-3 and Comparative Examples 1-3; Figure 2 Schematic diagrams of charge cycle life curves for Examples 1-3 and Comparative Examples 1-3. The silicon-carbon polyaniline composite materials based on gradient carbon nanotube distribution prepared in Examples 1-3 and Comparative Examples 1-3 were applied to the negative electrode materials. In the electrochemical performance testing of the lithium-ion battery negative electrode materials, a CR2032 button half-cell system was used, and assembly was completed in a high-purity argon glove box with an oxygen content below 0.01 ppm. A lithium metal sheet was used as the counter electrode, and a 1 mol / L LiPF6 EC / EMC (V(EC):V(EMC) = 1:1) mixed solution was selected as the electrolyte. A Celgard 2400 membrane was used as the separator. The specific assembly process is as follows: First, stack the negative electrode shell, spring sheet, gasket, and lithium sheet in sequence. Add an appropriate amount of electrolyte to the surface of the lithium sheet, then cover with a separator. After the separator is fully wetted with electrolyte, place the 12mm diameter test electrode sheet on top of the separator. Finally, snap the positive electrode shell shut and press it firmly, then seal it in a plastic sample bag. Use an MSK-110 button cell sealing machine at 0.8MPa pressure to complete the sealing. The assembled battery is left to stand for 24 hours to ensure the electrode materials are fully wetted. Electrochemical performance testing includes charge-discharge curves and cycle stability analysis. Constant current charge-discharge tests are performed at a current density of 0.1A / g, with a test voltage window of 0.01-2.5V. Figure 1 as well as Figure 2 Analysis shows that this application provides a silicon-carbon polyaniline composite material with gradient carbon nanotube distribution that combines high capacity, low expansion, and excellent cycling stability by designing a multilayer coating structure with gradient carbon nanotube distribution and combining it with the conductivity and flexibility of polyaniline.

[0101] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0102] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing silicon-carbon polyaniline composite materials based on gradient carbon nanotube distribution, characterized in that, The preparation method includes the following steps: The resin material is dispersed in deionized water, a curing agent is added under stirring, and the material is cured, centrifuged, dried and carbonized, then pulverized to obtain carbonized material. The carbonized material is activated and cooled to obtain a porous carbon material. The porous carbon material was placed in a reaction vessel, first purged with nitrogen, then heated to 300℃~500℃ at a heating rate of 5℃ / min~10℃ / min, and a mixture of silane and argon was introduced for deposition treatment for 10h~30h. Then, the temperature was raised to 500℃~700℃ at a heating rate of 5℃ / min~15℃ / min, and a mixture of acetylene and argon was introduced for encapsulation treatment for 8h~12h to obtain a silicon-carbon composite material. The silicon-carbon composite material was pre-dispersed, and then modified by adding silane coupling agent and carbon nanotubes to obtain a modified silicon-carbon composite material. Aniline, ammonium persulfate and hydrochloric acid were added to the modified silicon-carbon composite material, and in-situ polymerization was initiated in an ice-water bath. After a first stirring treatment, washing and annealing treatment were performed to obtain a silicon-carbon polyaniline composite material. Carboxymethyl cellulose and carbon black were added to a mixer for a second stirring process. Then, carbon nanotubes, modified silicon-carbon composite material, and deionized water were added for a third stirring process. Styrene-butadiene rubber was then added for a fourth stirring process. The mixture was then sieved and air bubbles were removed to obtain a silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution.

2. The preparation method according to claim 1, characterized in that, The resin material is phenolic resin; the mass ratio of the phenolic resin to deionized water is 1:(3-9).

3. The preparation method according to claim 2, characterized in that, The curing agent is a citric acid solution; The mass ratio of citric acid to phenolic resin is (0.03-0.1):1; In the citric acid solution, the mass ratio of citric acid to deionized water is 1:(2-20).

4. The preparation method according to claim 2, characterized in that, The carbonization process is as follows: first, the temperature is increased to 600℃ at a heating rate of 5℃ / min and held for 2h to 6h, then the temperature is increased to 1000℃ to 1050℃ and held for 6h to 10h.

5. The preparation method according to claim 2, characterized in that, The activation treatment is as follows: after the carbonized material is purged with nitrogen to remove oxygen, it is heated to 700℃~1200℃ at a heating rate of 5℃ / min, nitrogen is introduced and kept at this temperature for 0.5h~2h, and then carbon dioxide is introduced for activation treatment for 10h~30h.

6. The preparation method according to claim 5, characterized in that, The flow rate of nitrogen is (50-500) mL / min; the flow rate of carbon dioxide is (100-800) mL / min.

7. The preparation method according to claim 2, characterized in that, In the mixture of silane and argon, the volume ratio of silane to argon is (1-3):1; the flow rate of the silane is (10-40) mL / min.

8. The preparation method according to claim 2, characterized in that, In the mixture of acetylene and argon, the volume ratio of acetylene to argon is (1-3):1; the flow rate of acetylene is (10-40) mL / min.

9. The preparation method according to claim 2, characterized in that, The mass ratio of the silicon-carbon composite material, silane coupling agent, and carbon nanotubes is 1:(0.005~0.02):(0.00001~0.0001).

10. A silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution, characterized in that, The silicon-carbon polyaniline composite material based on gradient carbon nanotube distribution is obtained by the preparation method described in any one of claims 1 to 9.

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