Modified three-dimensional porous carbon-based silicon-carbon negative electrode material and preparation method thereof

Abstract

The invention provides a modified three-dimensional porous carbon-based silicon-carbon negative electrode material and a preparation method thereof, and belongs to the technical field of lithium ion battery negative electrode materials. The preparation method comprises the following steps: mixing an organic carbon source and a conductive agent in a solution, and sequentially drying, curing and carbonizing the obtained mixture under an inert gas condition to obtain a modified carbon precursor; carrying out activating treatment on the modified carbon precursor under an inert gas condition to obtain a modified three-dimensional porous carbon skeleton; under the condition of protective gas, introducing silane gas into the modified three-dimensional porous carbon skeleton, and carrying out vapor deposition to obtain a silicon / modified three-dimensional porous composite material; and under the condition of protective gas, introducing carbon source gas into the silicon / modified three-dimensional porous composite material, and carrying out vapor deposition to obtain the modified three-dimensional porous carbon-based silicon-carbon negative electrode material. The prepared modified three-dimensional porous carbon-based silicon-carbon negative electrode material is low in expansion rate, good in cycle performance and excellent in conductivity.

Description

Technical Field

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

[0002] Lithium-ion batteries are widely used in various energy storage devices due to their high energy density and long cycle life. Existing lithium-ion battery storage devices with graphite anodes are no longer able to meet the demand for high-capacity storage devices. There is an urgent need to develop anode materials with higher energy density, higher specific capacity, and longer cycle life. Silicon anodes, as abundant, safe, and non-toxic resources with a theoretical specific capacity of 4200 mAh / g, are considered one of the most promising materials to replace graphite anodes.

[0003] However, existing silicon anodes exhibit significant volume expansion and material pulverization during charge and discharge, limiting their large-scale commercial application. Currently, a common solution is to combine silicon nanoparticles with carbon materials to create silicon-carbon composites, which can alleviate the issues of excessive expansion and poor rate performance to a certain extent.

[0004] Patent CN 117976881 A obtains nano-silicon powder by ball milling metallurgical silicon powder in a planetary ball mill, and then mixes it with a skeleton carbon source and a coating carbon source and performs high-temperature transient sintering to obtain a carbon-coated silicon-carbon composite material. However, the material obtained by this method may result in some silicon not being completely coated, thereby resulting in a decrease in the initial coulombic efficiency; Patent CN 116826017A effectively alleviates the volume effect of silicon nanomaterials on the secondary carbon carrier through the design of a secondary structure, but due to the high silicon content, the electrode expansion rate remains a major challenge. Summary of the Invention

[0005] The purpose of the present invention is to provide a modified three-dimensional porous carbon-based silicon-carbon negative electrode material and a preparation method thereof, so as to solve the technical problems of the existing silicon-carbon negative electrode material having high volume expansion rate and poor conductivity.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a modified three-dimensional porous carbon-based silicon-carbon negative electrode material, comprising the following steps:

[0008] (1) mixing an organic carbon source and a conductive agent in a solution, and sequentially drying, solidifying, and carbonizing the obtained mixture under inert gas conditions to obtain a modified carbon precursor;

[0009] (2) activating the modified carbon precursor under inert gas conditions to obtain a modified three-dimensional porous carbon skeleton;

[0010] (3) introducing silane gas into the modified three-dimensional porous carbon skeleton under protective gas conditions to perform vapor deposition to obtain a silicon / modified three-dimensional porous composite material;

[0011] (4) Under protective gas conditions, a carbon source gas is introduced into the silicon / modified three-dimensional porous composite material to perform vapor deposition to obtain a modified three-dimensional porous carbon-based silicon-carbon negative electrode material.

[0012] Furthermore, the organic carbon source comprises one or more of cellulose, glucose, asphalt, resin and lignin; the conductive agent comprises one or more of multi-walled carbon nanotubes, single-walled carbon nanotubes, graphene, vapor-grown carbon fibers and carbon fibers; the solution is an aqueous solution or an organic solution, and the mass ratio of the organic carbon source to the solution is 1:8 to 12.

[0013] Furthermore, the content of the conductive agent is 0.01 to 10% of the mass of the organic carbon source, and the mixing time is 2 to 12 hours.

[0014] Furthermore, the drying and curing temperature is 130-180°C, and the drying and curing time is 1-20 hours; the carbonization temperature is 650-1100°C, and the carbonization time is 1-5 hours, and the heating rate to the carbonization temperature is 2-5°C / min.

[0015] Furthermore, the activation treatment includes physical activation or alkaline activation, the physical activation is activation by passing CO2 or water vapor, and the flow rate is 0.5~5L / min; the alkaline activation is activation by using an alkaline reagent, and the alkaline reagent includes NaOH, KOH or K2CO3, and the mass ratio of the modified carbon precursor and the alkaline reagent is 1:10~1:1.

[0016] Furthermore, the activation treatment is high-temperature activation, the temperature of the high-temperature activation is 650-1100° C., and the time of the high-temperature activation is 1-5 hours.

[0017] Furthermore, in the step (3), the silane gas comprises one or more of monosilane, disilane, disilane, trisilane and chlorosilane, the mass ratio of Si in the silane gas to the modified three-dimensional porous carbon skeleton is 1:9 to 9:1, and the flow ratio of the silane gas to the protective gas is 1:10 to 1:1;

[0018] The temperature of the vapor deposition is 400-1000° C., the heating rate is 4-10° C. / min, and the flow rate of the silane gas is 0.5-8 L / min.

[0019] Furthermore, in step (4), the carbon source gas comprises one or more of methane, ethane, acetylene and propyne, the flow ratio of the carbon source gas to the protective gas is 1:10 to 1:1, the flow rate of the carbon source gas is 0.5 to 8 L / min, the temperature of the vapor deposition is 500 to 1000°C, and the heating rate is 4 to 10°C / min.

[0020] Furthermore, the inert gas in step (1) and step (2) independently comprises one or more of nitrogen, argon and helium;

[0021] The protective gas in step (3) and step (4) independently comprises one or more of nitrogen, argon and helium.

[0022] The present invention provides a modified three-dimensional porous carbon-based silicon-carbon negative electrode material.

[0023] Beneficial effects of the present invention:

[0024] (1) The modified three-dimensional porous carbon-based silicon-carbon negative electrode material prepared by the present invention takes porous skeleton carbon as the core, provides more pore defects for silicon deposition, improves the ability of the silicon-carbon negative electrode to desorb / adsorb lithium ions, and finally coats a carbon layer on the surface of the silicon-carbon negative electrode to avoid direct contact between active silicon and electrolyte, reduce the consumption of active lithium, achieve structural stability of the silicon-carbon negative electrode during charge and discharge, and improve the rate charge and discharge performance and cycle stability of the silicon-carbon negative electrode during charge and discharge; at the same time, due to the addition of the conductive agent, an excellent conductive network is provided for the silicon-carbon negative electrode;

[0025] (2) The modified three-dimensional porous carbon-based silicon-carbon negative electrode material prepared by the present invention has a porous carbon skeleton, which provides more conduction / transmission paths for electrons / ions; at the same time, the presence of the porous carbon skeleton can provide a higher compaction density for the silicon-carbon negative electrode;

[0026] (3) The modified three-dimensional porous carbon-based silicon-carbon negative electrode material prepared by the present invention has low expansion rate, good cycle performance and excellent conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention provides a flow chart for preparing modified three-dimensional porous carbon-based silicon-carbon negative electrode materials. DETAILED DESCRIPTION

[0028] The present invention provides a method for preparing a modified three-dimensional porous carbon-based silicon-carbon negative electrode material, comprising the following steps:

[0029] (1) mixing an organic carbon source and a conductive agent in a solution, and sequentially drying, solidifying, and carbonizing the obtained mixture under inert gas conditions to obtain a modified carbon precursor;

[0030] (2) activating the modified carbon precursor under inert gas conditions to obtain a modified three-dimensional porous carbon skeleton;

[0031] (3) introducing silane gas into the modified three-dimensional porous carbon skeleton under protective gas conditions to perform vapor deposition to obtain a silicon / modified three-dimensional porous composite material;

[0032] (4) Under protective gas conditions, a carbon source gas is introduced into the silicon / modified three-dimensional porous composite material to perform vapor deposition to obtain a modified three-dimensional porous carbon-based silicon-carbon negative electrode material.

[0033] In the present invention, the organic carbon source comprises one or more of cellulose, glucose, asphalt, resin and lignin; the conductive agent comprises one or more of multi-walled carbon nanotubes, single-walled carbon nanotubes, graphene, vapor-grown carbon fibers and carbon fibers; preferably one or more of cellulose, glucose and resin; the resin is preferably phenolic resin or epoxy resin; the solution is an aqueous solution or an organic solution, preferably ethanol and / or methanol; the mass ratio of the organic carbon source to the solution is 1:8 to 12, preferably 1:10.

[0034] In the present invention, the content of the conductive agent is 0.01-10% of the mass of the organic carbon source, preferably 0.01-1%, more preferably 0.01-0.5%; the mixing time is 2-12 hours, preferably 5-10 hours, more preferably 6-8 hours.

[0035] In the present invention, the drying and curing temperature is 130-180°C, preferably 140-160°C, and more preferably 150°C; the drying and curing time is 1-20h, preferably 2-15h, and more preferably 5-10h; the carbonization temperature is 650-1100°C, preferably 700-1000°C, and more preferably 800-900°C; the carbonization time is 1-5h, preferably 2-4h, and more preferably 3h; the heating rate to the carbonization temperature is 2-5°C / min, and preferably 3-4°C / min.

[0036] In the present invention, the activation treatment includes physical activation or alkaline activation, and the physical activation is to activate by passing CO2 or water vapor, and the flow rate is 0.5~5L / min, preferably 1~4L / min, and more preferably 1~3L / min; the alkaline activation is to activate by using an alkaline reagent, and the alkaline reagent includes NaOH, KOH or K2CO3, preferably NaOH; the mass ratio of the modified carbon precursor and the alkaline reagent is 1:10~1:1, preferably 1:9~1:2, and more preferably 1:8~1:5.

[0037] In the present invention, the activation treatment is high-temperature activation, the temperature of high-temperature activation is 650-1100°C, preferably 700-1000°C, more preferably 800-900°C; the time of high-temperature activation is 1-5h, preferably 2-4h, more preferably 3h.

[0038] In the present invention, in step (3), the silane gas contains one or more of monosilane, disilane, disilane, trisilane and chlorosilane, preferably monosilane; the mass ratio of Si in the silane gas to the modified three-dimensional porous carbon skeleton is 1:9 to 9:1, preferably 2:8 to 8:2, and more preferably 3:7 to 7:3; the flow ratio of the silane gas to the protective gas is 1:10 to 1:1, preferably 1:9 to 1:2, and more preferably 1:8 to 1:5.

[0039] In the present invention, in step (3), the temperature of vapor deposition is 400-1000°C, preferably 500-900°C, and more preferably 500-700°C; the heating rate is 4-10°C / min, preferably 4-8°C / min, and more preferably 4-6°C / min; the flow rate of silane gas is 0.5-8 L / min, preferably 1-7 L / min, and more preferably 2-6 L / min.

[0040] In the present invention, in step (4), the carbon source gas comprises one or more of methane, ethane, acetylene and propyne, preferably methane; the flow ratio of the carbon source gas to the protective gas is 1:10 to 1:1, preferably 1:9 to 1:2, and more preferably 1:8 to 1:5; the flow rate of the carbon source gas is 0.5 to 8 L / min, preferably 1 to 7 L / min, and more preferably 2 to 6 L / min; the temperature of the vapor deposition is 500 to 1000°C, preferably 500 to 900°C, and more preferably 500 to 800°C; the heating rate is 4 to 10°C / min, preferably 4 to 8°C / min, and more preferably 4 to 6°C / min.

[0041] In the present invention, the inert gas in step (1) and step (2) independently comprises one or more of nitrogen, argon and helium, preferably nitrogen;

[0042] The protective gas in step (3) and step (4) independently comprises one or more of nitrogen, argon and helium, preferably nitrogen.

[0043] The present invention provides a modified three-dimensional porous carbon-based silicon-carbon negative electrode material.

[0044] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0045] Example 1

[0046] (1) Phenolic resin and single-walled carbon nanotubes (CNTs) (mass ratio of 1:0.03) were added to an organic solution (ethanol solution, mass ratio of phenolic resin to ethanol of 1:10) and stirred for 6 h for dispersion, followed by drying and curing at 150 °C for 12 h under the condition of N2; then, the temperature was raised to 800 °C at a heating rate of 4 °C / min under the protection of N2 for pre-carbonization for 3 h to obtain a modified carbon precursor.

[0047] (2) The modified carbon precursor was placed in a rotary kiln, heated to 850°C at a heating rate of 4°C / min under the condition of passing N2, and then activated by passing 1L / min of CO2 for 3 hours; after the activation was completed, it was washed with water for 2 hours and dried at 150°C for 3 hours to obtain a modified three-dimensional porous carbon skeleton.

[0048] (3) The modified three-dimensional porous carbon skeleton was placed in a rotary furnace and heated to 550°C at a heating rate of 4°C / min. Monosilane was introduced under the condition of N2 (monosilane gas flow rate: N2 flow rate = 1:1), and the monosilane gas flow rate was 5 L / min. Silicon deposition was carried out for 4 hours to obtain a silicon / modified three-dimensional porous carbon composite material.

[0049] (4) The silicon / modified three-dimensional porous carbon composite material was placed in a rotary furnace and heated to 850°C at a heating rate of 4°C / min. Acetylene gas was introduced under the condition of N2 (acetylene gas flow rate: N2 flow rate = 1:1), the acetylene gas flow rate was 5 L / min, and carbon coating was performed for 4 hours; a modified three-dimensional porous carbon-based silicon-carbon negative electrode material was obtained, with a Si content of 42% and a carbon content of 58%.

[0050] Example 2

[0051] The only difference from Example 1 is that the phenolic resin in step (1) is replaced by epoxy resin; the carbonization temperature is 600°C, the holding time is 2h, and the prepared modified three-dimensional porous carbon-based silicon-carbon negative electrode material has a Si content of 45% and a carbon content of 55%.

[0052] Example 3

[0053] The only difference from Example 2 is that in step (1), single-walled carbon nanotubes CNT are replaced by vapor-grown carbon fibers VGCF; the conditions for the drying and curing stage of the mixture are: drying and curing at 120°C for 5 hours under the condition of passing N2, and the prepared modified three-dimensional porous carbon-based silicon-carbon negative electrode material has a Si content of 48% and a carbon content of 52%.

[0054] Example 4

[0055] The only difference from Example 1 is that in step (1), the phenolic resin is replaced by cellulose; NaOH is used for activation, the mass ratio of the modified carbon precursor to NaOH is 1:1, the activation temperature is 1000°C, and the activation time is 2h. The prepared modified three-dimensional porous carbon-based silicon-carbon negative electrode material has a Si content of 52% and a carbon content of 48%.

[0056] Example 5

[0057] The only difference from Example 1 is that in the vapor deposition in step (3), the temperature is raised to 650°C at a heating rate of 4°C / min, and monosilane is introduced under the condition of N2 (monosilane gas flow rate: N2 flow rate = 1:1), the monosilane gas flow rate is 8 L / min, and silicon deposition is carried out for 3 hours. The prepared modified three-dimensional porous carbon-based silicon-carbon negative electrode material has a Si content of 50% and a carbon content of 50%.

[0058] Example 6

[0059] The only difference from Example 1 is that in the vapor deposition in step (4), methane gas is used, the flow rate of methane gas is 6 L / min, the vapor deposition temperature is 700°C, and the prepared modified three-dimensional porous carbon-based silicon-carbon negative electrode material has a Si content of 40% and a carbon content of 60%.

[0060] Comparative Example 1

[0061] The asphalt-based porous carbon material (without adding a conductive agent) was added to a rotary kiln, and monosilane was introduced under nitrogen protection, with the monosilane gas flow rate: nitrogen flow rate = 1:5, and the deposition temperature was 650°C; after the silane deposition was completed, acetylene gas was introduced under nitrogen protection, with the acetylene gas flow rate: nitrogen flow rate = 1:5; a silicon-carbon negative electrode material was prepared with a Si content of 50% and a carbon content of 50%.

[0062] Comparative Example 2

[0063] A phenolic resin-based porous carbon material (without adding a conductive agent) was added to a rotary kiln, and monosilane was introduced under nitrogen protection, with the monosilane gas flow rate: nitrogen flow rate = 1:5, and the deposition temperature was 650°C; after the silane deposition was completed, acetylene gas was introduced under nitrogen protection, with the acetylene gas flow rate: nitrogen flow rate = 1:5; a silicon-carbon negative electrode material was prepared with a Si content of 50% and a carbon content of 50%.

[0064] The modified three-dimensional porous carbon-based silicon-carbon negative electrode materials obtained in Examples 1 to 6 and the silicon-carbon negative electrode materials obtained in Comparative Examples 1 to 2 were subjected to performance tests, and the results are shown in Table 1 below.

[0065] Table 1 Test results

[0066]

[0067] As can be seen from Table 1, the silicon-carbon negative electrode material prepared in the embodiment of the present invention exhibits more excellent electrochemical performance (first charge specific capacity, first efficiency and capacity retention rate) than the comparative example.

[0068] As can be seen from the above embodiments, the present invention provides a modified three-dimensional porous carbon-based silicon-carbon negative electrode material and a preparation method thereof. The modified three-dimensional porous carbon-based silicon-carbon negative electrode material prepared by the present invention uses porous skeleton carbon as the core, provides more pore defects for silicon deposition, improves the ability of the silicon-carbon negative electrode to desorb / adsorb lithium ions, and finally coats a layer of carbon on the surface of the silicon-carbon negative electrode to avoid direct contact between active silicon and electrolyte, reduce the consumption of active lithium, achieve structural stability during the charge and discharge process of the silicon-carbon negative electrode, and improve the rate charge and discharge performance and cycle stability of the silicon-carbon negative electrode during the charge and discharge process; at the same time, due to the addition of the conductive agent, an excellent conductive network is provided for the silicon-carbon negative electrode.

[0069] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a modified three-dimensional porous carbon-based silicon-carbon negative electrode material, It is characterized in that The following steps are involved: (1) mixing an organic carbon source and a conductive agent in a solution, and sequentially drying, curing, and carbonizing the obtained mixture under an inert gas condition to obtain a modified carbon precursor; (2) activating the modified carbon precursor under inert gas conditions to obtain a modified three-dimensional porous carbon skeleton; (3) Under protective gas conditions, introducing silane gas into the modified three-dimensional porous carbon skeleton to perform vapor deposition to obtain a silicon / modified three-dimensional porous composite material; (4) Under protective gas conditions, a carbon source gas is introduced into the silicon / modified three-dimensional porous composite material to perform vapor deposition to obtain a modified three-dimensional porous carbon-based silicon-carbon negative electrode material.

2. The preparation method according to claim 1, It is characterized in that The organic carbon source comprises one or more of cellulose, glucose, asphalt, resin and lignin; the conductive agent comprises one or more of multi-walled carbon nanotubes, single-walled carbon nanotubes, graphene, vapor-grown carbon fibers and carbon fibers; the solution is an aqueous solution or an organic solution, and the mass ratio of the organic carbon source to the solution is 1:8 to 12.

3. The preparation method according to claim 1 or 2, It is characterized in that The content of the conductive agent is 0.01-10% of the mass of the organic carbon source, and the mixing time is 2-12 hours.

4. The preparation method according to claim 3, It is characterized in that The drying and curing temperature is 130-180° C., and the drying and curing time is 1-20 hours; the carbonization temperature is 650-1100° C., and the carbonization time is 1-5 hours, and the heating rate to the carbonization temperature is 2-5° C. / min.

5. The preparation method according to claim 1, 2 or 4, It is characterized in that The activation treatment comprises physical activation or alkali activation, wherein the physical activation is to pass CO 2 or water vapor for activation, with an inlet flow rate of 0.5 to 5 L / min; the alkali activation is activated by using an alkali reagent, and the alkali reagent includes NaOH, KOH or K 2 CO 3 The mass ratio of the modified carbon precursor to the alkaline reagent is 1:10 to 1:

1.

6. The preparation method according to claim 5, It is characterized in that The activation treatment is high-temperature activation, the temperature of the high-temperature activation is 650-1100° C., and the time of the high-temperature activation is 1-5 hours.

7. The preparation method according to claim 1 or 6, It is characterized in that In the step (3), the silane gas comprises one or more of monosilane, disilane, disilane, trisilane and chlorosilane, the mass ratio of Si in the silane gas to the modified three-dimensional porous carbon skeleton is 1:9 to 9:1, and the flow ratio of the silane gas to the protective gas is 1:10 to 1:1; The temperature of vapor deposition is 400-1000° C., the heating rate is 4-10° C. / min, and the flow rate of silane gas is 0.5-8 L / min.

8. The preparation method according to claim 7, It is characterized in that In the step (4), the carbon source gas comprises one or more of methane, ethane, acetylene and propyne, the flow ratio of the carbon source gas to the protective gas is 1:10 to 1:1, the flow rate of the carbon source gas is 0.5 to 8 L / min, the temperature of the vapor deposition is 500 to 1000°C, and the heating rate is 4 to 10°C / min.

9. The preparation method according to claim 1, 2 or 8, It is characterized in that In step (1) and step (2), the inert gas independently comprises one or more of nitrogen, argon and helium; The protective gas in step (3) and step (4) independently comprises one or more of nitrogen, argon and helium.

10. The modified three-dimensional porous carbon-based silicon-carbon negative electrode material prepared by the preparation method according to any one of claims 1 to 9.

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