Composite silicon carbon electrode material and preparation method thereof

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a composite silicon-carbon electrode material and a preparation method thereof.The preparation method comprises the following steps that silane gas serves as a deposition precursor, first-time deposition treatment is conducted through a chemical vapor deposition method, and a first silicon-carbon intermediate is prepared; taking long-chain alkane as a deposition precursor, and carrying out secondary deposition treatment by using a chemical vapor deposition method to prepare a second silicon-carbon intermediate; taking short-chain alkyne as a deposition precursor, and carrying out third deposition treatment by a chemical vapor deposition method to prepare a silicon-carbon core; carrying out spray coating treatment on a titanium source to prepare a composite silicon-carbon core; and uniformly mixing the composite silicon-carbon inner core with an amorphous carbon precursor, and performing carbonization heat treatment to prepare the composite silicon-carbon electrode material. The problems of poor conductivity, volume expansion and interface side reaction of the silicon-based material are systematically solved, so that the technical problem of poor electrochemical performance of the traditional silicon-carbon composite material is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a composite silicon-carbon electrode material and a preparation method thereof. BACKGROUND

[0002] In the field of lithium ion battery negative electrode materials, silicon-based materials are highly concerned due to their high theoretical specific capacity. However, the existing silicon-carbon negative electrode materials face many technical bottlenecks in practical application. First, silicon materials have a serious volume expansion effect during charging and discharging, which leads to electrode structure damage and rapid cycle performance degradation. Second, the intrinsic conductivity of silicon materials is poor, which limits the rate performance. In addition, the side reaction between silicon and electrolyte can further deteriorate the electrochemical performance.

[0003] Traditional silicon-carbon composite materials are mainly prepared by simple mechanical mixing or physical coating, which is difficult to effectively solve the above problems. Although some studies attempt to improve the conductivity by carbon coating, the conventional carbon layer often cannot adapt to the volume change of silicon and is easily broken and failed during the cycle process, resulting in poor electrochemical performance of traditional silicon-carbon composite materials and difficulty in practical application. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and provides a composite silicon-carbon electrode material and a preparation method thereof, which solves the technical problem of poor electrochemical performance of traditional silicon-carbon composite materials.

[0005] To achieve the above-mentioned purpose, the following technical solutions are adopted: The present application provides a preparation method of a composite silicon-carbon electrode material, comprising the following steps: Silane gas is used as a deposition precursor to perform a first deposition treatment by chemical vapor deposition to deposit nanosilicon on the surface of the porous carbon material, thereby preparing a first silicon-carbon intermediate; long-chain alkane is used as a deposition precursor to perform a second deposition treatment by chemical vapor deposition to deposit long-chain carbon on the surface of the first silicon-carbon intermediate, thereby preparing a second silicon-carbon intermediate; short-chain alkyne is used as a deposition precursor to perform a third deposition treatment by chemical vapor deposition to deposit short-chain carbon on the surface of the second silicon-carbon intermediate, thereby preparing a silicon-carbon inner core; a titanium source is coated by spraying to form a nanometer titanium dioxide layer on the surface of the silicon-carbon inner core, thereby preparing a composite silicon-carbon inner core; and the composite silicon-carbon inner core is mixed uniformly with an amorphous carbon precursor and then subjected to carbonization heat treatment to form an amorphous soft carbon layer on the surface of the composite silicon-carbon inner core, thereby preparing a composite silicon-carbon electrode material.

[0006] In one possible implementation manner, the porous carbon material is at least one of coconut shell carbon, resin carbon and petroleum coke, and the pore size of the porous carbon material is microporous or mesoporous.

[0007] In a possible implementation, the long-chain alkane is at least one of ethane, propane, butane and pentane, and the short-chain alkyne is at least one of acetylene, propyne, 1-butyne and 1-pentyne.

[0008] In a possible implementation, the deposition temperature of the first deposition process is 500-800 DEG C, and the deposition time is 0.5-24 h.

[0009] In a possible implementation, the titanium source is at least one of isopropyl titanate, tetrabutyl titanate and nano-titanium dioxide.

[0010] In a possible implementation, the flow rate of the carrier gas in the spray coating process is 2-10 L / min, and the flow rate of the titanium source sprayed is 1-15 mL / min.

[0011] In a possible implementation, the amorphous carbon precursor is at least one of petroleum pitch, coal tar pitch, phenolic resin and furan resin, and the mass ratio of the composite silicon-carbon core to the amorphous carbon precursor is 19:1.

[0012] In a possible implementation, after the carbonization heat treatment, the method further comprises a sieving process. The particle size of the composite silicon-carbon electrode material after the sieving process is 11-15 µm.

[0013] The application further provides a composite silicon-carbon electrode material prepared by the method.

[0014] In a possible implementation, in the composite silicon-carbon electrode material, the mass percentage of Si is 30-60%, the mass percentage of C is 30-60%, and the mass percentage of the titanium dioxide layer is 1‰-10‰.

[0015] The application has the advantages that, compared with the prior art, the application forms a rigid-flexible composite carbon layer by adopting a three-stage chemical vapor deposition of silane-long-chain alkane-short-chain alkyne, constructs a lithium ion rapid channel by combining a spray-coated nano-titanium dioxide layer, and finally forms a stress buffering and conductive synergic network by secondary granulation of amorphous soft carbon. The system realizes four technical synergies of accommodating volume change by microporous carbon skeleton, dispersing stress concentration by gradient carbon layer, improving ion transmission efficiency by titanium dioxide, and realizing structure stability by soft carbon coating, systematically solves the problems of poor conductivity, volume expansion and interface side reaction of silicon-based materials, and solves the technical problem of poor electrochemical performance of traditional silicon-carbon composite materials. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 FIG. 1 is a structure diagram of a composite silicon-carbon electrode material provided by the application. DETAILED DESCRIPTION

[0017] To solve the above technical problems, the application provides a composite silicon-carbon electrode material and a preparation method thereof, and the technical solutions and examples of the application will be described in detail in combination with the drawings.

[0018] In the description of the present application, it should be understood that the terms "first", "second" and the like are only used to distinguish description, and cannot be understood as indicating or implying relative importance.

[0019] In the field of lithium ion battery negative electrode materials, the traditional silicon-carbon composite system faces technical bottlenecks such as discontinuous conductive network, structure collapse caused by silicon phase volume expansion, and intensified solid-liquid interface side reactions. Silicon particles produce more than 300% volume change during lithiation / delithiation, resulting in mechanical stress concentration between active materials and conductive matrix, causing particle breakage and electrode structure damage. At the same time, the intrinsic electrical conductivity of silicon material is low, and local current density difference is formed during charging and discharging, causing lithium ion transport dynamics delay. The thick SEI film formed by continuous decomposition of electrolyte on the surface of silicon further increases the interface impedance, resulting in exponential decay of capacity retention rate.

[0020] In the face of the above problems, the application first considers building a multi-stage buffer structure to cope with the mechanical stress caused by silicon volume expansion. Traditional single-layer carbon coating cannot effectively disperse local stress concentration, and needs to realize step-by-step stress dissipation through gradient modulus design. For this purpose, different carbon sources are used to form a composite carbon layer in stages, in which the flexible carbon layer generated by long-chain alkanes can absorb deformation energy, and the high-strength carbon layer formed by short-chain alkynes can maintain structural integrity. At the same time, the interfacial bonding strength between silicon particles and carbon matrix directly affects the electron transport efficiency, and the deposition process needs to be optimized to ensure uniform growth of nano-silicon on the surface of porous carbon. In addition, the electrolyte penetration problem requires the construction of a dense and ion-conducting protective layer, which needs to introduce metal oxides as ion transport channels in the carbon skeleton. By comparing the process characteristics of liquid phase coating and gas phase deposition, chemical vapor deposition method is selected to realize precise and controllable growth of nano-silicon and carbon layer, and spray coating technology is used to ensure uniform coverage of the titanium dioxide layer.

[0021] For this purpose, the application provides a preparation method of a composite silicon-carbon electrode material, comprising the following steps: The silane gas is used as a deposition precursor to perform a first deposition treatment by chemical vapor deposition to deposit nanosilicon on the surface of the porous carbon material to obtain a first silicon-carbon intermediate; the long-chain alkane is used as a deposition precursor to perform a second deposition treatment by chemical vapor deposition to deposit long-chain carbon on the surface of the first silicon-carbon intermediate to obtain a second silicon-carbon intermediate; the short-chain alkyne is used as a deposition precursor to perform a third deposition treatment by chemical vapor deposition to deposit short-chain carbon on the surface of the second silicon-carbon intermediate to obtain a silicon-carbon core; the titanium source is coated by spraying to form a nanometer titanium dioxide layer on the surface of the silicon-carbon core to obtain a composite silicon-carbon core; and the composite silicon-carbon core is mixed with an amorphous carbon precursor, and then subjected to carbonization heat treatment to form an amorphous soft carbon layer on the surface of the composite silicon-carbon core to obtain a composite silicon-carbon electrode material.

[0022] The core innovation of the present application is to construct a gradient buffer system through multi-level structure design and step-by-step deposition process, to form a rigid-flexible composite carbon layer by three-stage chemical vapor deposition of silane-long-chain alkane-short-chain alkyne, to construct a lithium ion rapid channel by spraying a nanometer titanium dioxide layer, and finally to form a stress buffer and conductive synergistic network by secondary granulation of amorphous soft carbon. The system realizes four technical synergies of accommodating volume change by microporous carbon skeleton, dispersing stress concentration by gradient carbon layer, improving ion transmission efficiency by titanium dioxide, and realizing structure stability by soft carbon coating, and systematically solves the problems of poor conductivity, volume expansion and interface side reaction of silicon-based materials.

[0023] The working process and principle of the present application are to construct a composite silicon-carbon electrode material with gradient buffer and conductivity optimization through multi-level structure design and step-by-step deposition process. First, nanosilicon is deposited on the surface of porous carbon by chemical vapor deposition to form a silicon-carbon conductive skeleton. The microporous or mesoporous structure of the porous carbon provides accommodation space for the volume expansion of silicon and enhances the efficiency of electron transmission. Second, a flexible long-chain carbon layer is formed by deposition of long-chain alkane to relieve the stress concentration of the silicon core. Then, a short-chain carbon layer is formed by deposition of short-chain alkyne to further strengthen the structural rigidity and form a stable silicon-carbon core. Next, a uniform nanometer titanium dioxide layer is formed by spraying a titanium source, and titanium dioxide serves as a lithium ion transmission channel to reduce diffusion resistance and improve the chemical stability of the material. Finally, secondary granulation is achieved by coating with an amorphous soft carbon layer, and the elastic buffer properties of soft carbon and the three-dimensional conductive network synergistically inhibit the volume effect of silicon while optimizing the lithium ion diffusion path.

[0024] The present application will be described in detail below through specific examples, which are exemplary and intended to explain the present application, and cannot be understood as a limitation of the present application.

[0025] In the following examples, the methods are conventional methods unless otherwise specified; and the reagents and materials are commercially available unless otherwise specified.

[0026] Example 1 The present embodiment provides a preparation method of a composite silicon-carbon electrode material, comprising the following steps: Step 1, preparation of a first silicon-carbon intermediate.

[0027] Put 1 kg of coconut shell microporous carbon material into a fluidized bed device, and introduce 3 L / min of silane gas into the device. Under the condition of 600 DEG C high temperature, make the elemental silicon formed by the cracking of silane adhere to the microporous carbon pore channel and surface. The silane deposition time is 5 h. After the end of silane deposition, the first silicon-carbon intermediate is obtained.

[0028] Step 2, preparation of a silicon-carbon core.

[0029] After the end of silane deposition in step 1, continue to introduce 3 L / min of propane into the fluidized bed device for long-chain carbon coating under the condition of keeping the temperature at 600 DEG C. The deposition time is 1 h. Then continue to introduce 3 L / min of acetylene for short-chain carbon coating. The deposition time is 1 h. Then cool down to obtain the silicon-carbon core.

[0030] Step 3, preparation of a composite silicon-carbon core.

[0031] Take the material in step 2 and put it into a spray coating machine. The rotating speed is set to 1000 r / min, and the carrier gas flow is set to 500 L / min. 10 ml of isopropyl titanate is configured into 150 ml of isopropyl titanate ethanol solution, and then spray coating is carried out at a speed of 5 ml / min. After the completion of the spray coating operation, the material is dried at 200 DEG C under the protection of nitrogen for 2 h. The dried composite silicon-carbon core is obtained.

[0032] Step 4, preparation of a composite silicon-carbon electrode material. Take the material in step 3 and mix it with petroleum pitch at a mass ratio of 19:1. After uniform mixing, put it into an amorphous carbon carbon coating and secondary granulation device for carbonization heat treatment. The heating rate of carbonization heat treatment is 10 DEG C / min, the heat treatment temperature is 800 DEG C, and the time is 15 hours. After carbonization heat treatment, cool to room temperature. After mixing and sieving, the D50 size is 11-15 um. Thus, the composite silicon-carbon electrode material is obtained.

[0033] Example 2 The present embodiment provides a preparation method of a composite silicon-carbon electrode material, comprising the following steps: Step 1, preparation of a first silicon-carbon intermediate.

[0034] Put 1 kg of coconut shell microporous carbon material into a fluidized bed device, and introduce 3 L / min of silane gas into the device. Under the condition of 600 DEG C high temperature, make the elemental silicon formed by the cracking of silane adhere to the microporous carbon pore channel and surface. The silane deposition time is 5 h. After the end of silane deposition, the first silicon-carbon intermediate is obtained.

[0035] Step 2, preparation of the silicon-carbon core.

[0036] After the end of silane deposition in step 1, the temperature is kept at 600℃, and 3L / min of propane is continuously introduced into the fluidized bed device for long-chain carbon coating, with a deposition time of 1h. Then 3L / min of acetylene is continuously introduced for short-chain carbon coating, with a deposition time of 1h, and then the temperature is lowered to obtain the silicon-carbon core.

[0037] Step 3, preparation of the composite silicon-carbon core.

[0038] The material in step 2 is put into a spray coating machine, with a rotation speed of 1000r / min and a carrier gas flow rate of 500L / min. 10ml of isopropyl titanate is configured into 150ml of isopropyl titanate ethanol solution, and then sprayed at a speed of 5ml / min. After the completion of the spray coating operation, the material is dried at 200℃ under nitrogen protection for 2h, and the dried composite silicon-carbon core is obtained.

[0039] Step 4, preparation of the composite silicon-carbon electrode material. The material in step 3 is mixed with coal tar pitch at a mass ratio of 19:1, and then put into an amorphous carbon coating and secondary granulation device for carbonization heat treatment. The heating rate is 10℃ / min, the heat treatment temperature is 800℃, and the time is 15 hours. After cooling to room temperature, the mixture is sieved to obtain a composite silicon-carbon electrode material with a D50 size of 11μm-15μm.

[0040] Example 3 The present embodiment provides a method for preparing a composite silicon-carbon electrode material, comprising the following steps: Step 1, preparation of the first silicon-carbon intermediate.

[0041] 1kg of coconut shell microporous carbon material is put into a fluidized bed device, and 3L / min of silane gas is introduced into the device at a high temperature of 600℃, so that the elemental silicon formed by the cracking of silane is attached to the microporous carbon pores and surface. The silane deposition time is 5h, and the first silicon-carbon intermediate is obtained after the end of silane deposition.

[0042] Step 2, preparation of the silicon-carbon core.

[0043] After the end of silane deposition in step 1, the temperature is kept at 600℃, and 3L / min of propane is continuously introduced into the fluidized bed device for long-chain carbon coating, with a deposition time of 1h. Then 3L / min of acetylene is continuously introduced for short-chain carbon coating, with a deposition time of 1h, and then the temperature is lowered to obtain the silicon-carbon core.

[0044] Step 3, preparation of the composite silicon-carbon core.

[0045] Take the material in step 2 into the spray coating machine, set the rotating speed to 1000r / min, and set the carrier gas flow to 500L / min. Prepare 10ml of titanium tetrabutoxide into 150ml of titanium tetrabutoxide ethanol solution, and then spray coat at a speed of 5ml / min. After the spray coating operation is completed, dry the material at 200℃ under nitrogen protection for 2h, and the dried composite silicon-carbon inner core is obtained.

[0046] Step 4, preparation of composite silicon-carbon electrode material.

[0047] Take the material in step 3 and mix with petroleum pitch at a mass ratio of 19:1. After mixing evenly, put it into the amorphous carbon coating and secondary granulation equipment for carbonization heat treatment. The carbonization heat treatment temperature is 800℃, the heating rate is 10℃ / min, and the time is 15 hours. After carbonization heat treatment, cool to room temperature, mix and sieve to make the D50 size 11μm-15μm, and the composite silicon-carbon electrode material is obtained.

[0048] Example 4 The present embodiment provides a preparation method of a composite silicon-carbon electrode material, comprising the following steps: Step 1, preparation of first silicon-carbon intermediate.

[0049] Put 1kg of coconut shell mesoporous carbon material into the fluidized bed equipment, and introduce 3L / min of silane gas into the equipment. At 600℃ high temperature, the elemental silicon formed by the cracking of silane is attached to the pore channels and surface of the microporous carbon. The silane deposition time is 5h, and the first silicon-carbon intermediate is obtained after the silane deposition is completed.

[0050] Step 2, preparation of silicon-carbon inner core.

[0051] After the silane deposition in step 1 is completed, continue to introduce 3L / min of propane into the fluidized bed equipment for long-chain carbon coating at a temperature of 600℃. The deposition time is 1h. Then continue to introduce 3L / min of ethyne for short-chain carbon coating, and the deposition time is 1h. Then cool down to obtain the silicon-carbon inner core.

[0052] Step 3, preparation of composite silicon-carbon inner core.

[0053] Take the material in step 2 into the spray coating machine, set the rotating speed to 1000r / min, and set the carrier gas flow to 500L / min. Prepare 10ml of titanium tetrabutoxide into 150ml of titanium tetrabutoxide ethanol solution, and then spray coat at a speed of 5ml / min. After the spray coating operation is completed, dry the material at 200℃ under nitrogen protection for 2h, and the dried composite silicon-carbon inner core is obtained.

[0054] Step 4, preparation of composite silicon-carbon electrode material. The material in step 3 is mixed with petroleum pitch at a mass ratio of 19:1, and then is put into the amorphous carbon carbon-coated secondary granulation equipment after being uniformly mixed, and is subjected to carbonization heat treatment, the carbonization heat treatment temperature is 10℃ / min, the heat treatment temperature is 800℃, and the time is 15 hours; after the carbonization heat treatment, it is cooled to room temperature, and is mixed and sieved to make the D50 size 11μm-15μm, and then the composite silicon-carbon electrode material is obtained.

[0055] Example 5 The difference from example 1 is only that the porous carbon material in step 1 is a resin microporous carbon material.

[0056] Example 6 The difference from example 1 is only that the porous carbon material in step 1 is a resin mesoporous carbon material.

[0057] Example 7 The difference from example 1 is only that the porous carbon material in step 1 is a petroleum coke microporous carbon material.

[0058] Example 8 The difference from example 1 is only that the porous carbon material in step 1 is a petroleum coke mesoporous carbon material.

[0059] Example 9 The difference from example 1 is only that the long-chain alkane in step 2 is ethane.

[0060] Example 10 The difference from example 1 is only that the long-chain alkane in step 2 is butane.

[0061] Example 11 The difference from example 1 is only that the long-chain alkane in step 2 is pentane.

[0062] Example 12 The difference from example 1 is only that the short-chain alkyne in step 2 is propyne.

[0063] Example 13 The difference from example 1 is only that the short-chain alkyne in step 2 is 1-butyne.

[0064] Example 14 The difference from example 1 is only that the short-chain alkyne in step 2 is 1-pentyne.

[0065] Example 15 The difference from example 1 is only that the titanium source in step 3 is nano-silicon dioxide.

[0066] Example 16 The difference from example 1 is only that the amorphous carbon precursor in step 4 is phenolic resin.

[0067] Example 17 The difference from Example 1 is that the amorphous carbon precursor in step 4 is furan resin.

[0068] It should be noted that there is no obvious difference in the performance of the composite silicon-carbon electrode material prepared in Examples 5-17 compared with Example 1.

[0069] Comparative Example 1 The present embodiment provides a preparation method of a composite silicon-carbon electrode material, comprising the following steps: Put 1 kg of coconut shell microporous carbon material into a fluidized bed device, introduce 3 L / min of silane gas into the device, and form elemental silicon attached to the microporous carbon pore channel and surface under high temperature conditions of 600 DEG C, the silane deposition time is 5 h, and the silicon-carbon material is obtained after the silane deposition is completed.

[0070] Then continue to introduce 3 L / min of acetylene for short-chain carbon coating, the deposition time is 1 h, and then cool down to obtain a silicon-carbon inner core material, mix the silicon-carbon inner core material with petroleum pitch at a mass ratio of 19:1, uniformly mix, and then put into an amorphous carbon coating and secondary granulation device, perform carbonization heat treatment, the carbonization heat treatment temperature is 800 DEG C, the heating rate is 10 DEG C / min, and the time is 15 hours; cool to room temperature after the carbonization heat treatment, mix and sieve to make the D50 size 11-15 μm, and the finished product silicon-carbon negative electrode material is obtained.

[0071] The composite silicon-carbon electrode material is tested for the discharge performance: Specific surface area test: the composite silicon-carbon electrode materials prepared in Examples 1-4 and the silicon-carbon negative electrode material prepared in Comparative Example 1 are used as test materials. Take 2 g of the test material and bake for 2 h, and then use a BET 2000A specific surface tester to test, and the test results are shown in Table 1.

[0072] Alkali solution gas production test: the composite silicon-carbon electrode materials prepared in Examples 1-4 and the silicon-carbon negative electrode material prepared in Comparative Example 1 are used as test materials. In a room temperature environment, take 1 g of the test material and add to 20 g of a potassium hydroxide solution with a solid content of 20% and stir uniformly, and test the 24 h gas production. The greater the gas production, the more incomplete the surface coating of the silicon-carbon negative electrode material, and the more easily the alkali solution penetrates and reacts with silicon.

[0073] Button test: the composite silicon-carbon electrode material prepared by example 1 to example 4 and the silicon-carbon negative electrode material prepared by comparative example 1 were used as electrode materials. The electrode material, conductive agent SP and binder CMC were fully ground into a slurry in a mass ratio of 8:1:1, and then the mixed slurry was coated on a copper foil to prepare an electrode sheet. The electrode sheet was dried in a vacuum drying oven at 80 DEG C for 12 hours, and then punched into a circular electrode sheet with a diameter of 16 mm. The punched electrode sheet with a diameter of 16 mm was used as a positive electrode, and a lithium metal sheet was used as a negative electrode to assemble a CR2032 type button half battery.

[0074] The charge and discharge cut-off voltages were 1.5 V and 0.005 V respectively, and after 3 activation cycles of the battery under a current density of 0.1 C, the rate performance was tested under a current density of 1 C, 2 C and 5 C, and then the cycle stability test was carried out under a current density of 0.5 C. The specific capacity, initial efficiency, rate and cycle retention rate obtained by the test are shown in table 1.

[0075] Table 1: electrochemical performance test results From table 1, compared with comparative example 1, the initial efficiency, discharge retention rate under different rates and 100 cycle retention rate of the composite silicon-carbon electrode material prepared by example 1 to example 4 were obviously improved, which indicated that the preparation method provided by the present application could improve the electrochemical performance of the composite silicon-carbon electrode material, so as to solve the technical problem of poor electrochemical performance of the traditional silicon-carbon composite material. In addition, compared with comparative example 1, the gas production of the composite silicon-carbon electrode material prepared by example 1 to example 4 was decreased, which indicated that the outer coating effect of the composite silicon-carbon electrode material prepared by the preparation method provided by the present application was good, and the internal silicon material was well protected.

[0076] The above description is only the preferred embodiment of the present application, and the above specific embodiment is not a limitation of the present application. Various modifications and changes can occur within the technical concept of the present application, and any modification, change or equivalent replacement made by those skilled in the art according to the above description shall fall within the scope of the present application.

Claims

1. A method for preparing a composite silicon-carbon electrode material, characterized in that, The method comprises the following steps: a first deposition treatment is performed on the porous carbon material by chemical vapor deposition using silane gas as a deposition precursor to deposit nanosilicon on the surface of the porous carbon material, thereby obtaining a first silicon-carbon intermediate; a second deposition treatment is performed on the first silicon-carbon intermediate by chemical vapor deposition using long-chain alkane as a deposition precursor to deposit long-chain carbon on the surface of the first silicon-carbon intermediate, thereby obtaining a second silicon-carbon intermediate; a third deposition treatment is performed on the second silicon-carbon intermediate by chemical vapor deposition using short-chain alkyne as a deposition precursor to deposit short-chain carbon on the surface of the second silicon-carbon intermediate, thereby obtaining a silicon-carbon core; a nanometer titanium dioxide layer is formed on the surface of the silicon-carbon core by spray coating using a titanium source, thereby obtaining a composite silicon-carbon core; the composite silicon-carbon core is mixed with an amorphous carbon precursor, and then subjected to carbonization heat treatment to form an amorphous soft carbon layer on the surface of the composite silicon-carbon core, thereby obtaining a composite silicon-carbon electrode material.

2. The production method according to claim 1, characterized by, The porous carbon material is at least one of coconut shell carbon, resin carbon and petroleum coke, and the porous carbon material has micropores or mesopores.

3. The preparation method according to claim 1, characterized in that, The long-chain alkane is at least one of ethane, propane, butane and pentane, and the short-chain alkyne is at least one of ethyne, propyne, 1-butyne and 1-pentyne.

4. The method of claim 1, wherein, The deposition temperature of the first deposition treatment is 500-800°C, and the deposition time is 0.5-24h.

5. The preparation method according to claim 1, characterized in that, The titanium source is at least one of isopropyl titanate, tetrabutyl titanate and nanometer titanium dioxide.

6. The method of claim 1, wherein, The flow rate of the carrier gas in the spray coating treatment is 2-10L / min, and the flow rate of the titanium source sprayed is 1-15mL / min.

7. The preparation method according to claim 1, characterized in that, The amorphous carbon precursor is at least one of petroleum pitch, coal tar pitch, phenolic resin and furan resin, and the mass ratio of the composite silicon-carbon core to the amorphous carbon precursor is 19:

1.

8. The method of claim 1, wherein, After the carbonization heat treatment, the method further comprises a sieving treatment. The particle size of the composite silicon-carbon electrode material after the sieving treatment is 11-15µm.

9. A composite silicon-carbon electrode material, characterized in that, The composite silicon-carbon electrode material is a multi-core type core-shell structure prepared by the preparation method of any one of claims 1-8.

10. The composite silicon-carbon electrode material of claim 9, wherein, In the composite silicon-carbon electrode material, the mass percentage of Si is 30-60%, the mass percentage of C is 30-60%, and the mass percentage of the titanium dioxide layer is 1‰-10‰.

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