Preparation method of electrode composite material, electrode composite material and application of electrode composite material

Abstract

The invention discloses a preparation method of an electrode composite material, the electrode composite material and application of the electrode composite material, and the preparation method comprises the following steps: sequentially crushing and pickling a soft carbon raw material to obtain a soft carbon precursor; placing the soft carbon precursor, a hard carbon material and absolute ethyl alcohol in a sand mill for sanding treatment, and uniformly mixing to obtain a mixed dispersion liquid; carrying out drying treatment on the mixed dispersion liquid to obtain a composite carbon matrix precursor; placing the composite carbon matrix precursor in a rotary furnace, performing carbonization treatment in an inert gas environment, and performing grinding, crushing and sieving to obtain a carbonized compound; placing the carbonized compound in a rotary furnace, and activating under the condition of carbon dioxide gas and / or water vapor to obtain a composite carbon matrix containing a pore structure; and introducing gas containing a silicon source into the rotary furnace, depositing nano silicon in pores of the composite carbon matrix through chemical vapor deposition, and crushing to obtain the electrode composite material.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage, and particularly relates to a preparation method of an electrode composite material, the electrode composite material and its application. Background Art

[0002] A supercapacitor is a new type of energy storage material, which has attracted much attention due to a series of characteristics such as long cycle life, high power density, and wide working temperature range. The performance of a supercapacitor depends to a great extent on the composition of the electrode material and the design of the electrode structure. By changing the composition, morphology, content, etc. of the active material of the supercapacitor, the performance of the supercapacitor can be effectively improved.

[0003] The negative electrode material in the supercapacitor electrode is one of the main places where electrochemical reactions occur in the supercapacitor, playing a key role in energy conversion and storage. In order to meet the performance requirements of the battery, an ideal negative electrode material should have a series of characteristics, such as having a low lithium intercalation potential, allowing more lithium ions to undergo reversible deintercalation and intercalation, maintaining a stable structure during charge and discharge, and having high electron / ion conductivity, etc. The presence of these characteristics directly affects the energy density, cycle life, and safety performance of the supercapacitor.

[0004] The interlayer spacing of soft carbon is 0.34 nm - 0.37 nm, which is usually prepared by high-temperature carbonization of thermoplastic precursors such as petroleum coke, pitch, and anthracite, and has the advantages of low cost and high carbon yield. Soft carbon belongs to easily graphitizable carbon, that is, it can complete the orderly arrangement of the amorphous carbon lattice under high-temperature treatment above 2500 °C. Soft carbon has low crystallinity, small grain size, high compatibility with the electrolyte, and a large specific surface area, showing high reversible capacity, power density, and first Coulomb efficiency.

[0005] The interlayer spacing of hard carbon is 0.37 nm - 0.42 nm, which is usually prepared using thermosetting precursors such as phenolic resin, biomass, and sucrose. After high-temperature treatment above 2500 °C, the microcrystalline structure still remains highly disordered and has few graphite sheet stacks. Compared with soft carbon, hard carbon has higher crystal structure stability and is not prone to lattice expansion and contraction phenomena, so it has good cycle stability. Due to the problems of low first Coulomb efficiency and low carbon yield of hard carbon materials, its economic benefits are slightly poor. At the same time, the rate performance at low voltage is not very ideal.

[0006] By using a hard carbon source to coat a soft carbon source, a composite carbon matrix is prepared. The composite carbon matrix is then subjected to medium-temperature carbonization, physical activation, and chemical vapor deposition to obtain a composite material. The soft carbon source in this composite material has a relatively large specific surface area (1000 m 2 / g - 2500 m 2The characteristics of / g enable silicon to be effectively loaded inside the composite carbon matrix, while the stable crystal structure of the hard carbon source can effectively inhibit silicon expansion. The combined effect makes this composite material have excellent electrical properties. Summary of the Invention

[0007] Embodiments of the present invention provide a preparation method of an electrode composite material, the electrode composite material and its application, aiming to solve the problems of low energy density, unsatisfactory cycle life existing in existing supercapacitors.

[0008] In the first aspect, embodiments of the present invention provide a preparation method of an electrode composite material, and the preparation method includes:

[0009] Step S1: Crushing and pickling the soft carbon raw material in sequence to obtain a soft carbon precursor;

[0010] Step S2: Placing the soft carbon precursor, hard carbon material and absolute ethanol in a sand mill in a certain proportion, performing sand milling treatment, and mixing evenly to obtain a mixed dispersion;

[0011] Step S3: Drying the mixed dispersion to obtain a composite carbon matrix precursor;

[0012] Step S4: Placing the composite carbon matrix precursor in a rotary furnace, performing carbonization treatment in an inert gas environment, grinding, pulverizing and sieving to obtain a carbonized composite;

[0013] Step S5: Placing the carbonized composite in the rotary furnace again, performing activation treatment under the condition of carbon dioxide gas and / or water vapor to obtain a composite carbon matrix with a pore structure;

[0014] Step S6: Introducing a gas containing a silicon source into the rotary furnace, depositing nano-silicon in the pores of the composite carbon matrix by chemical vapor deposition, and pulverizing to obtain an electrode composite material.

[0015] Preferably, the soft carbon raw material includes one or more of petroleum coke, pitch or anthracite;

[0016] The hard carbon material includes one or more of phenolic resin, biomass carbon or sucrose;

[0017] The mass ratio of the soft carbon precursor, hard carbon material and absolute ethanol is [1-6]:[2-5]:[5-60].

[0018] Preferably, the equipment for crushing in step S1 includes any one of a jet mill, a jaw crusher or a pair-roll crusher;

[0019] The particle size Dv50 of the soft carbon precursor is 6 μm - 15 μm, and the ash content is ≤ 0.2%;

[0020] The rotation speed of the sanding treatment in step S2 is 1100 rpm - 4000 rpm, and the time of the sanding treatment is 1 hour - 5 hours.

[0021] Preferably, the drying treatment method in step S3 includes oven drying or closed spray drying;

[0022] The temperature of the oven drying is 80°C - 120°C, and the drying time is 7 hours - 24 hours;

[0023] The equipment used for the closed spray drying is a closed-loop spray dryer; the specific conditions for the closed spray drying are: set the inlet air temperature to 150°C - 180°C, the outlet air temperature to 75°C - 140°C, and the frequency of the atomizer to 220 Hz - 280 Hz.

[0024] Preferably, the inert gas in step S4 includes nitrogen and / or argon; the flow rate of the inert gas is 0.5 L / min - 5 L / min;

[0025] The specific process of the carbonization treatment is: heating at a heating rate of 2°C / min - 5°C / min to 400°C - 800°C, holding for 2 hours - 7 hours, and then naturally cooling to room temperature;

[0026] The mesh number of the sieving is 80 mesh - 200 mesh.

[0027] Preferably, the specific process of the activation treatment in step S5 is: placing the carbonized composite in a rotary furnace again, introducing carbon dioxide gas to maintain a carbon dioxide gas environment in the rotary furnace, heating at a heating rate of 1°C / min - 5°C / min to 800°C - 1100°C, and / or turning on a peristaltic pump to drop deionized water so that the deionized water generates water vapor when heated, and the carbonized composite undergoes an activation reaction under the action of carbon dioxide atmosphere and / or water vapor. Subsequently, turn off the peristaltic pump, switch the gas introduced into the rotary furnace from carbon dioxide gas to a protective gas, and naturally cool in an inert gas environment to obtain a composite carbon matrix with a pore structure;

[0028] Among them, the gas flow rate of the carbon dioxide is 2 L / min - 16 L / min, and the dropping amount of the deionized water is 6 g / min - 42 g / min;

[0029] The holding time of the activation reaction is 6 hours - 18 hours.

[0030] Preferably, the silicon source-containing gas is a mixed gas of a protective gas and a silicon source gas; the volume ratio of the protective gas to the silicon source gas is [1 - 10]:1, and the flow rate of the mixed gas is 8 L / h - 50 L / h;

[0031] The protective gas is any one of hydrogen, nitrogen, and argon;

[0032] The silicon source gas is one or more of silane, disilane, trisilane, tetrasilane, chlorosilane, and hexachlorosilane;

[0033] The heating temperature for the chemical vapor deposition is 500°C - 950°C, and the heat preservation time is 4 hours - 12 hours.

[0034] In a second aspect, an electrode composite material prepared by the preparation method according to the first aspect described above is provided in an embodiment of the present invention. The electrode composite material includes a soft carbon material, a hard carbon material coated on the surface of the soft carbon material, and nano-silicon particles deposited in the pores of the hard carbon material and the pores of the soft carbon material.

[0035] Preferably, the particle size Dv50 of the electrode composite material is 5 μm - 13 μm;

[0036] The percentage of the mass of the soft carbon material in the total mass of the electrode composite material is 5% - 55%;

[0037] The percentage of the mass of the hard carbon material in the total mass of the electrode composite material is 4% - 45%;

[0038] The percentage of the mass of the nano-silicon particles in the total mass of the electrode composite material is 5% - 45%;

[0039] The specific surface area of the electrode composite material is 1500 m 2 / g - 2000 m 2 / g; the pore diameter of the pores of the electrode composite material is between 2 nm and 5 nm.

[0040] In a third aspect, a supercapacitor is provided in an embodiment of the present invention. The supercapacitor includes the electrode composite material described in the second aspect above.

[0041] An embodiment of the present invention provides a preparation method of an electrode composite material, the electrode composite material and its application. By uniformly mixing a soft carbon precursor, a hard carbon material, and absolute ethanol to obtain a mixed dispersion liquid, then drying, carbonizing, grinding, pulverizing, and sieving the mixed dispersion liquid to obtain a carbonized composite, and then activating and pore-forming under carbon dioxide gas and / or water vapor, and finally depositing nano-silicon particles in the pores by chemical vapor deposition to obtain the electrode composite material.

[0042] The electrode composite material of the present invention is obtained by coating a hard carbon material on the surface of soft carbon. Both the soft carbon and the hard carbon have a pore structure in each group, and there is a through-hole structure between the soft carbon and the hard carbon, which can inhibit the expansion of silicon particles deposited in the pores, improve the stability of the material structure, and is not prone to problems such as pulverization and cracking. In addition, the electrode composite material of the present invention combines the characteristics of soft carbon and hard carbon. Soft carbon has the characteristics of low crystallinity, small grain size, high compatibility with the electrolyte, and a large specific surface area, which can improve the reversible capacity, power density, and first Coulomb efficiency of the material. The hard carbon coated on the surface of soft carbon has a stable crystal structure and is not prone to lattice expansion and contraction phenomena, which can further improve the stability of the material, thereby improving the electrochemical performance of the material. Using the electrode composite material of the present invention in a supercapacitor can improve the cycling performance of the supercapacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The technical solutions of the embodiments of the present invention will be further described in detail below with reference to the drawings and embodiments.

[0044] Figure 1 It is a flowchart of the preparation method of the electrode composite material provided by the embodiment of the present invention.

[0045] Figure 2 It is a schematic structural diagram of the cross-section of the electrode composite material provided by the embodiment of the present invention.

[0046] Figure 3 It is a scanning electron microscope (SEM) image of the electrode composite material provided by Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] The present invention will be further described in detail below with reference to the drawings and specific embodiments, but it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention.

[0048] The embodiment of the present invention provides a preparation method of an electrode composite material, as Figure 1 shown, which specifically includes the following steps:

[0049] Step S1, successively pulverize and acid-wash the soft carbon raw material to obtain a soft carbon precursor;

[0050] Among them, the soft carbon raw material includes one or more of petroleum coke, pitch, or anthracite;

[0051] The purpose of acid-washing the soft carbon raw material is to remove impurities in the soft carbon material, so that the content of impurities, that is, ash, in the obtained soft carbon precursor is less than or equal to 0.2%;

[0052] The crushing equipment used in this step includes any one of a jet mill, a jaw crusher, and a roll crusher; the particle size Dv50 of the obtained soft carbon precursor is 6 μm-15 μm.

[0053] Step S2, placing the soft carbon precursor, the hard carbon material, and anhydrous ethanol in a sand mill according to a certain ratio, performing sand milling treatment, and mixing them evenly to obtain a mixed dispersion;

[0054] Wherein, the hard carbon material includes: one or more of phenolic resin, biochar or sucrose;

[0055] The mass ratio of the soft carbon precursor, the hard carbon material and anhydrous ethanol is [1-6]: [2-5]: [5-60];

[0056] The rotation speed of the sand grinding treatment is 1100 rpm-4000 rpm, and the time of the sand grinding treatment is 1 hour-5 hours.

[0057] Step S3, drying the mixed dispersion to obtain a composite carbon matrix precursor;

[0058] Wherein, the drying method includes oven drying or closed spray drying;

[0059] The oven drying temperature is 80℃-120℃, and the drying time is 7 hours-24 hours;

[0060] The equipment used for closed spray drying is a closed cycle spray dryer; the specific conditions of closed spray drying are: setting the air inlet temperature to 150℃-180℃, the air outlet temperature to 75℃-140℃, and the atomizer frequency to 220Hz-280Hz.

[0061] Step S4, placing the composite carbon matrix precursor in a rotary kiln, performing carbonization treatment under an inert gas environment, grinding, crushing and screening to obtain a carbonized composite;

[0062] Wherein, the inert gas includes nitrogen and / or argon; the flow rate of the inert gas is 0.5L / min-5L / min;

[0063] The specific process of carbonization treatment is: heating to 400-800°C at a heating rate of 2°C / min-5°C / min, keeping the temperature for 2 hours-7 hours, and then naturally cooling to room temperature;

[0064] The composite carbon matrix precursor of this step is subjected to high-temperature carbonization treatment in an inert gas environment, so that the composite carbon matrix precursor can be formed into a single carbon substance;

[0065] The mesh size of the sieving is 80-200 meshes. Sieving can prevent the carbonized material from agglomerating, which is beneficial for a more complete reaction in the subsequent activation process.

[0066] Step S5: Place the carbonized composite in a rotary kiln again and perform activation treatment under carbon dioxide gas and / or water vapor conditions to obtain a composite carbon matrix with a pore structure.

[0067] Specifically, the specific process of the activation treatment can be divided into three cases:

[0068] The first case is to perform activation treatment on the carbonized composite under the combined action of carbon dioxide and water vapor. Specifically: Place the carbonized composite in a rotary kiln again, introduce carbon dioxide gas to maintain a carbon dioxide gas environment in the rotary kiln, heat it at a heating rate of 1 °C / min - 5 °C / min to 800 °C - 1100 °C, and / or turn on a peristaltic pump to drip deionized water so that the deionized water generates water vapor when heated. Under the carbon dioxide atmosphere and / or water vapor conditions, make the carbonized composite undergo an activation reaction. After keeping warm for 6 hours - 18 hours, turn off the peristaltic pump, switch the gas introduced into the rotary kiln from carbon dioxide gas to an inert gas, and naturally cool it in an inert gas environment to obtain a composite carbon matrix with a pore structure.

[0069] The second case is to perform activation treatment on the carbonized composite under the sole action of carbon dioxide. Specifically: Place the carbonized composite in a rotary kiln again, introduce carbon dioxide gas to maintain a carbon dioxide gas environment in the rotary kiln, heat it at a heating rate of 1 °C / min - 5 °C / min to 800 °C - 1100 °C, make the carbonized composite undergo an activation reaction under the carbon dioxide atmosphere conditions. After keeping warm for 6 hours - 18 hours, turn off the peristaltic pump, switch the gas introduced into the rotary kiln from carbon dioxide gas to an inert gas, and naturally cool it in an inert gas environment to obtain a composite carbon matrix with a pore structure.

[0070] The third case is to perform activation treatment on the carbonized composite under the sole action of water vapor. Specifically: Place the carbonized composite in a rotary kiln again, turn on a peristaltic pump to drip deionized water in an inert gas environment so that the deionized water generates water vapor when heated. Under the action of water vapor, make the carbonized composite undergo an activation reaction. After keeping warm for 6 hours - 18 hours, turn off the peristaltic pump, and naturally cool it in an inert gas environment to obtain a composite carbon matrix with a pore structure.

[0071] Among them, the gas flow rate of the above-mentioned carbon dioxide is 2 L / min - 16 L / min, the dropping amount of deionized water is 6 g / min - 42 g / min; the heat preservation time of the activation reaction is 6 hours - 18 hours.

[0072] The activation reaction of the present invention is to make the carbon element in the carbonized composite in step S4 react with carbon dioxide gas and / or water vapor at high temperature. The generated carbon monoxide gas is discharged from the position of the carbon element, leaving pores, so as to obtain a composite carbon matrix containing a pore structure. The specific reaction equation of the activation reaction is as follows:

[0073]

[0074]

[0075] Step S6: Introduce a gas containing a silicon source into the rotary furnace, and deposit nano-silicon in the pores of the composite carbon matrix by chemical vapor deposition, and then obtain the electrode composite material after pulverization;

[0076] Among them, the gas containing a silicon source is a mixed gas of a protective gas and a silicon source gas; the volume ratio of the protective gas to the silicon source gas is [1-10]:1, and the flow rate of the mixed gas is 8 L / h - 50 L / h; the protective gas is any one of hydrogen, nitrogen, and argon; the silicon source gas is one or more of silane, disilane, trisilane, tetrasilane, chlorosilane, and hexachlorosilane;

[0077] The heating temperature of the chemical vapor deposition is 500°C - 950°C, and the heat preservation time is 4 hours - 12 hours;

[0078] Finally, the particle size Dv50 of the electrode composite material obtained by pulverization in this step S6 is between 5 μm and 13 μm, and the pulverization is a conventional method.

[0079] The embodiment of the present invention provides an electrode composite material prepared by the above preparation method. The electrode composite material includes a soft carbon material, a hard carbon material coated on the surface of the soft carbon material, and nano-silicon particles deposited in the pores of the hard carbon material and the pores of the soft carbon material.

[0080] The particle size Dv50 of the electrode composite material is 5 μm - 13 μm;

[0081] The percentage of the mass of the soft carbon material in the total mass of the electrode composite material is 5% - 55%;

[0082] The percentage of the mass of the hard carbon material in the total mass of the electrode composite material is 4% - 45%;

[0083] The percentage of the mass of the nano-silicon particles in the total mass of the electrode composite material is 5% - 45%;

[0084] The specific surface area of the electrode composite material is 1500 m 2 / g - 2000 m 2 / g; the pore diameter of the pores of the electrode composite material is between 2 nm and 5 nm.

[0085] The schematic structural diagram of the cross-section of the electrode composite material provided by the embodiment of the present invention is as follows Figure 2 As shown, it can be seen that the soft carbon material is coated with hard carbon material, both the soft carbon material and the hard carbon material have pore structures, and a through-hole structure is formed between some of the pores in the soft carbon material and the hard carbon material, and the nano-silicon particles are distributed in the pores.

[0086] The electrode composite material prepared above in the present invention can be used as an electrode material for preparing a supercapacitor electrode. The supercapacitor electrode can be assembled with a positive electrode, an electrolyte, and a separator into a supercapacitor. The electrode composite material contained in the supercapacitor electrode can enable the supercapacitor to have better energy density and cycling performance. The supercapacitor provided by the present invention can be applied to electronic devices, electric vehicles or power storage systems.

[0087] In addition, the electrode composite material provided by the embodiment of the present invention can also be used as an active material in the negative electrode plate of a lithium-ion battery, which can improve the cycling performance of the lithium-ion battery.

[0088] To better understand the technical solution provided by the present invention, the preparation process and characteristics of the electrode composite material of the present invention are described below with multiple specific examples respectively.

[0089] Example 1

[0090] This example provides a preparation process and performance test of an electrode composite material. The specific preparation process is as follows.

[0091] (1) The soft carbon raw material anthracite was successively crushed and pickled to obtain 1 kg of soft carbon precursor, with a particle size Dv50 of 6 μm and an ash content ≤ 0.06%.

[0092] (2) Weigh the soft carbon precursor, the hard carbon material phenolic resin, and absolute ethanol according to a mass ratio of 2:4:48, place them in a sand mill, and perform sand milling treatment at a rotation speed of 1100 rpm for 3 hours to obtain a uniformly mixed dispersion liquid.

[0093] (3) The mixed dispersion liquid was subjected to closed spray drying, with an inlet air temperature of 170 °C, an outlet air temperature of 85 °C, and an atomizer frequency of 230 Hz to obtain a composite carbon matrix precursor.

[0094] (4) The composite carbon matrix precursor was placed in a rotary furnace, and under a nitrogen gas environment with a gas flow rate of 5 L / min, it was heated to 500 °C at a rate of 3 °C / min, held for 4 hours for carbonization treatment, naturally cooled to room temperature, and after discharging, grinding and pulverizing, and then sieving (200 mesh) to obtain a carbonized composite.

[0095] (5) The carbonized composite is then placed in a rotary furnace under a nitrogen atmosphere. After switching the inlet gas to carbon dioxide gas to displace nitrogen, it is heated to 900 °C at a heating rate of 3 °C / min. The peristaltic pump is turned on to drip deionized water, causing the deionized water to generate water vapor when heated. Under the action of carbon dioxide atmosphere and water vapor, the carbonized composite undergoes an activation reaction. Among them, the gas flow rate of carbon dioxide is 8 L / min, the dropping amount of deionized water is 34 g / min. After the activation reaction is kept warm for 14 hours, the peristaltic pump is turned off, and the inlet gas of the rotary furnace is switched from carbon dioxide gas to nitrogen, and it is naturally cooled under a nitrogen gas atmosphere to obtain a composite carbon matrix with a pore structure.

[0096] (6) A mixed gas of nitrogen gas and silane with a volume ratio of 3:1 is introduced into the rotary furnace, and the flow rate of the mixed gas is 30 L / h. It is heated to 800 °C and kept warm for 4 hours. Nano-silicon is deposited in the pores of the composite carbon matrix by chemical vapor deposition. After natural cooling to room temperature, it is pulverized to obtain an electrode composite material with a Dv50 particle size of 5 μm, the pore diameter of its pores is between 2 nm and 3 nm, and the specific surface area is 1800 m 2 / g.

[0097] The SEM image of the electrode composite material prepared in this example is as Figure 3 shown.

[0098] The supercapacitor electrode is prepared using the electrode composite material prepared in this example and tested. The specific process is as follows:

[0099] Preparing a supercapacitor electrode, specifically: the obtained composite material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are added to ethanol and mixed evenly according to a mass ratio of 85:5:15, and then N-methylpyrrolidone (NMP) is added to obtain a mixture. Then the mixture is evenly coated on nickel foam. It is vacuum dried at 85 °C for 12 hours, and finally pressed into a supercapacitor electrode.

[0100] Testing the supercapacitor electrode, specifically: using a three-electrode test system to evaluate the electrochemical performance of the supercapacitor electrode in this example. The electrolyte uses a 1 mol / L Na2SO4 solution, the charging cut-off voltage is 2 V, the discharging cut-off voltage is 0.05 V, the specific capacitance is measured at a current density of 0.01 A / g, the discharging capacity is measured at a current density of 0.05 A / g, and it is cycled 4000 times at a current density of 0.5 A / g to test the cycle capacity retention rate. Among them, a saturated calomel electrode is used as the reference electrode, and a graphite rod is used as the counter electrode. Before testing, the supercapacitor electrode is soaked in the above electrolyte for 3 hours to make the supercapacitor electrode fully contact with the electrolyte. The test data is shown in Table 1.

[0101] Example 2

[0102] This embodiment provides a preparation process and performance test of an electrode composite material. The specific preparation process is as follows.

[0103] (1) The soft carbon raw material, petroleum coke, is successively crushed and pickled to obtain 1 kg of soft carbon precursor with a Dv50 particle size of 5 μm and an ash content of ≤0.08%.

[0104] (2) Weigh the soft carbon precursor, the hard carbon material phenolic resin, and absolute ethanol according to a mass ratio of 1:4:34, place them in a sand mill, and perform sand milling treatment at a speed of 1200 rpm for 4 hours to obtain a uniformly mixed dispersion liquid.

[0105] (3) The mixed dispersion liquid is subjected to closed - type spray drying with an inlet air temperature of 180 °C, an outlet air temperature of 80 °C, and an atomizer frequency of 220 Hz to obtain a composite carbon matrix precursor.

[0106] (4) The composite carbon matrix precursor is placed in a rotary furnace. Under a nitrogen gas environment with a gas flow rate of 5 L / min, it is heated to 500 °C at a rate of 3 °C / min, held for 4 hours for carbonization treatment, naturally cooled to room temperature, and after discharging, grinding and pulverizing, and then sieving (200 mesh) to obtain a carbonized composite.

[0107] (5) The carbonized composite is placed in a rotary furnace under a nitrogen environment again. After switching the inlet gas to carbon dioxide gas to displace nitrogen, it is heated to 1000 °C at a heating rate of 3 °C / min, and a peristaltic pump is started to drip deionized water to make the deionized water generate water vapor when heated. Under the action of carbon dioxide atmosphere and water vapor, the carbonized composite undergoes an activation reaction. Among them, the gas flow rate of carbon dioxide is 15 L / min, the dropping amount of deionized water is 38 g / min. After the activation reaction is held for 15 hours, the peristaltic pump is closed, and the inlet gas of the rotary furnace is switched from carbon dioxide gas to nitrogen, and it is naturally cooled under a nitrogen gas environment to obtain a composite carbon matrix with a pore structure.

[0108] (6) A mixed gas of nitrogen gas and silane with a volume ratio of 3:1 is introduced into the rotary furnace with a mixed gas flow rate of 30 L / h, heated to 800 °C, held for 4 hours, and nano - silicon is deposited in the pores of the composite carbon matrix through chemical vapor deposition. After natural cooling to room temperature, it is pulverized to obtain an electrode composite material with a Dv50 particle size of 8 μm, the pore diameter of its pores is between 2 nm - 3 nm, and the specific surface area is 1500 m 2 / g.

[0109] The supercapacitor electrode is prepared using the electrode composite material prepared in this embodiment and tested. The specific process is the same as that in Example 1, and the test data are shown in Table 1.

[0110] Example 3

[0111] This embodiment provides a preparation process and performance test of an electrode composite material. The specific preparation process is as follows.

[0112] (1) The soft carbon raw material asphalt is successively crushed and pickled to obtain 1 kg of soft carbon precursor with a Dv50 particle size of 9 μm and an ash content of ≤0.08%.

[0113] (2) Weigh the soft carbon precursor, hard carbon material phenolic resin, and absolute ethanol according to a mass ratio of 3:4:52, place them in a sand mill, and perform sand milling treatment at a speed of 1200 rpm for 4 hours to obtain a uniformly mixed dispersion liquid.

[0114] (3) The mixed dispersion liquid is subjected to closed - type spray drying with an inlet air temperature of 185 °C, an outlet air temperature of 75 °C, and an atomizer frequency of 220 Hz to obtain a composite carbon matrix precursor.

[0115] (4) The composite carbon matrix precursor is placed in a rotary kiln. Under a nitrogen gas environment with a gas flow rate of 5 L / min, it is heated to 500 °C at a rate of 3 °C / min, held for 4 hours for carbonization treatment, naturally cooled to room temperature, and after discharging, grinding and sieving (200 - mesh) are carried out to obtain a carbonized composite.

[0116] (5) The carbonized composite is placed in a rotary kiln in a nitrogen environment again. After switching the inlet gas to carbon dioxide gas to remove nitrogen, it is heated to 850 °C at a heating rate of 5 °C / min. The peristaltic pump is turned on to drip deionized water, so that the deionized water generates water vapor when heated. Under the action of carbon dioxide atmosphere and water vapor, the carbonized composite undergoes an activation reaction. Among them, the gas flow rate of carbon dioxide is 10 L / min, the deionized water dropping amount is 40 g / min. After the activation reaction is held for 12 hours, the peristaltic pump is turned off, and the inlet gas of the rotary kiln is switched from carbon dioxide gas to nitrogen, and it is naturally cooled in a nitrogen gas environment to obtain a composite carbon matrix with a pore structure.

[0117] (6) A mixed gas of nitrogen gas and silane with a volume ratio of 3:1 is introduced into the rotary kiln with a mixed gas flow rate of 30 L / h, heated to 800 °C, held for 4 hours, and nano - silicon is deposited in the pores of the composite carbon matrix by chemical vapor deposition. After natural cooling to room temperature, it is pulverized to obtain an electrode composite material with a Dv50 particle size of 5 μm, the pore diameter of its pores is between 3 nm and 5 nm, and the specific surface area is 1800 m 2 / g.

[0118] The supercapacitor electrode is prepared using the electrode composite material prepared in this embodiment and tested. The specific process is the same as that in Example 1, and the test data are shown in Table 1.

[0119] Example 4

[0120] This embodiment provides a preparation process and performance test of an electrode composite material. The specific preparation process is as follows.

[0121] (1) The anthracite, a soft carbon raw material, is successively crushed and pickled to obtain 1 kg of soft carbon precursor with a Dv50 particle size of 6 μm and an ash content of ≤0.08%.

[0122] (2) The soft carbon precursor, hard carbon material phenolic resin, and absolute ethanol are weighed according to a mass ratio of 3:4:52 and placed in a sand mill, and sanded at a speed of 1100 rpm for 5 hours to obtain a uniformly mixed dispersion liquid.

[0123] (3) The mixed dispersion liquid is subjected to closed spray drying with an inlet air temperature of 180 °C, an outlet air temperature of 85 °C, and an atomizer frequency of 230 Hz to obtain a composite carbon matrix precursor.

[0124] (4) The composite carbon matrix precursor is placed in a rotary furnace. Under a nitrogen gas environment with a gas flow rate of 5 L / min, it is heated to 500 °C at a rate of 3 °C / min, held for 4 hours for carbonization treatment, naturally cooled to room temperature, and after discharging, grinding and sieving (200 mesh) are carried out to obtain a carbonized composite.

[0125] (5) The carbonized composite is placed in a rotary furnace under a nitrogen environment again. After switching the inlet gas to carbon dioxide gas to remove nitrogen, it is heated to 1100 °C at a heating rate of 3 °C / min, and a peristaltic pump is started to dropwise add deionized water to generate water vapor by heating the deionized water. Under the action of carbon dioxide atmosphere and water vapor, the carbonized composite undergoes an activation reaction. Among them, the gas flow rate of carbon dioxide is 8 L / min, the dropping amount of deionized water is 25 g / min. After the activation reaction is held for 18 hours, the peristaltic pump is closed, and the inlet gas of the rotary furnace is switched from carbon dioxide gas to nitrogen, and it is naturally cooled under the nitrogen gas environment to obtain a composite carbon matrix with a pore structure.

[0126] (6) A mixed gas of nitrogen gas and silane with a volume ratio of 3:1 is introduced into the rotary furnace with a mixed gas flow rate of 30 L / h, heated to 800 °C, and held for 4 hours. Nano-silicon is deposited in the pores of the composite carbon matrix by chemical vapor deposition. After naturally cooling to room temperature, it is pulverized to obtain an electrode composite material with a Dv50 particle size of 6 μm, the pore diameter of its pores is between 2 nm and 3 nm, and the specific surface area is 1500 m 2 / g.

[0127] The supercapacitor electrode is prepared using the electrode composite material prepared in this embodiment and tested. The specific process is the same as that in Example 1, and the test data are shown in Table 1.

[0128] To better illustrate the effects of the embodiments of the present invention, Comparative Example 1 is compared with the above embodiments.

[0129] Comparative Example 1

[0130] This comparative example provides a preparation process and performance test of a traditional silicon-carbon electrode material, including the following steps:

[0131] (1) Silicon particles, carbon source precursor polyvinylpyrrolidone, phenolic resin, and antioxidant citric acid were weighed according to a mass ratio of 1:1:1:0.1, placed in a sand mill, and an ethanol solution was added for sand milling treatment to obtain a dispersion.

[0132] (2) The dispersion was spray-dried to obtain a precursor material.

[0133] (3) The precursor material was subjected to gas-phase coating. Specifically, 1 kg of the precursor material was placed in a rotary furnace, heated to 850 °C under a protective atmosphere, and argon and acetylene gases were introduced in a volume ratio of 2:1 for gas-phase coating. After maintaining the temperature for 1.5 hours, the organic gas source was turned off, and after cooling to room temperature, the material was discharged and classified to obtain the silicon-carbon electrode material.

[0134] The supercapacitor electrode was prepared using the silicon-carbon electrode material prepared in the comparative example and tested. The specific process was the same as that in Example 1, and the test data are shown in Table 1.

[0135] Table 1 is a summary of the electrochemical test data of the supercapacitor electrodes assembled in Examples 1-4 and Comparative Example 1:

[0136]

[0137] Table 1

[0138] From the comparison of the test data in Table 1, it can be seen that the specific capacitance of the supercapacitor electrodes in Examples 1-4 of the present invention at a current density of 0.01 A / g and the cycle capacity retention rate after 4000 cycles at a current density of 0.5 A / g are both greater than those in Comparative Example 1. This is because the electrode composite material of the present invention is included in the electrode plates of the supercapacitors assembled in Examples 1-4. This material coats hard carbon on the surface of soft carbon. Both soft carbon and hard carbon have pore structures in each group, and there are through-hole structures between soft carbon and hard carbon, which can inhibit the expansion of silicon particles deposited in the pores, improve the stability of the material structure, and are not prone to problems such as pulverization and cracking. In addition, the electrode composite material of the present invention combines the characteristics of soft carbon and hard carbon. Soft carbon has the characteristics of low crystallinity, small grain size, high compatibility with the electrolyte, and a large specific surface area, which can improve the reversible capacity, power density, and initial Coulomb efficiency of the material. The hard carbon coated on the surface of soft carbon has the characteristic of a stable crystal structure and is not prone to lattice expansion and contraction phenomena, which can further improve the stability of the material and thus improve the cycle performance. It should be noted that the discharge capacity of the supercapacitor electrode in Example 3 is slightly less than that in Comparative Example 1 at a current density of 0.05 A / g, and its performance is slightly worse than that in Examples 1, 2, and 4. This is because the soft carbon raw material used in Example 3 is asphalt, and microcracks may have occurred during the preparation of the electrode composite material, resulting in a relatively decreased performance of the material. However, due to the good comprehensive performance of the electrode composite material of the present invention, the cycle performance of the supercapacitor electrode in Example 3 is still better than that in Comparative Example 1.

[0139] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing an electrode composite material, characterized in that, The preparation method includes: Step S1: Crushing and pickling the soft carbon raw material in sequence to obtain a soft carbon precursor; Step S2: Placing the soft carbon precursor, hard carbon material, and absolute ethanol in a sand mill in a certain proportion, performing sand milling treatment, and mixing evenly to obtain a mixed dispersion; Step S3: Drying the mixed dispersion to obtain a composite carbon matrix precursor; Step S4: Placing the composite carbon matrix precursor in a rotary furnace, performing carbonization treatment in an inert gas environment, grinding, pulverizing, and sieving to obtain a carbonized composite; Step S5: Placing the carbonized composite in the rotary furnace again, performing activation treatment under the conditions of carbon dioxide gas and / or water vapor to obtain a composite carbon matrix with a pore structure; Step S6: Introducing a gas containing a silicon source into the rotary furnace, depositing nano-silicon in the pores of the composite carbon matrix by chemical vapor deposition, and pulverizing to obtain an electrode composite material.

2. The preparation method according to claim 1, characterized in that, The soft carbon raw material includes one or more of petroleum coke, pitch, or anthracite; The hard carbon material includes one or more of phenolic resin, biomass carbon, or sucrose; The mass ratio of the soft carbon precursor, hard carbon material, and absolute ethanol is [1-6]:[2-5]:[5-60].

3. The preparation method according to claim 1, characterized in that, The equipment for crushing in Step S1 includes any one of a jet mill, a jaw crusher, or a pair-roll crusher; The particle size Dv50 of the soft carbon precursor is 6 μm - 15 μm, and the ash content is ≤ 0.2%; The rotation speed of the sand milling treatment in Step S2 is 1100 rpm - 4000 rpm, and the sand milling treatment time is 1 hour - 5 hours.

4. The preparation method according to claim 1, characterized in that, The drying treatment method in Step S3 includes oven drying or closed spray drying; The temperature of the oven drying is 80°C - 120°C, and the drying time is 7 hours - 24 hours; The equipment used for the closed spray drying is a closed-loop spray dryer; the specific conditions for the closed spray drying are: setting the inlet air temperature to 150°C - 180°C, the outlet air temperature to 75°C - 140°C, and the frequency of the atomizer to 220 Hz - 280 Hz.

5. The preparation method according to claim 1, characterized in that, The inert gas in Step S4 includes nitrogen and / or argon; the flow rate of the inert gas is 0.5 L / min - 5 L / min; The specific process of the carbonization treatment is: heating at a heating rate of 2°C / min - 5°C / min to 400°C - 800°C, holding for 2 hours - 7 hours, and then naturally cooling to room temperature; The mesh number of the sieving is 80 mesh - 200 mesh.

6. The preparation method according to claim 1, characterized in that, The specific process of the activation treatment in Step S5 is: placing the carbonized composite in the rotary furnace again, introducing carbon dioxide gas to keep a carbon dioxide gas environment in the rotary furnace, heating at a heating rate of 1°C / min - 5°C / min to 800°C - 1100°C, and / or turning on a peristaltic pump to drip deionized water to generate water vapor by heating the deionized water, and performing an activation reaction on the carbonized composite under the action of carbon dioxide atmosphere and / or water vapor. Subsequently, turn off the peristaltic pump, switch the gas introduced into the rotary furnace from carbon dioxide gas to a protective gas, and naturally cool in an inert gas environment to obtain a composite carbon matrix with a pore structure; Among them, the gas flow rate of the carbon dioxide is 2 L / min - 16 L / min, and the dropping amount of the deionized water is 6 g / min - 42 g / min; The heat preservation time of the activation reaction is 6 hours - 18 hours.

7. The preparation method according to claim 1, characterized in that, The gas containing the silicon source is a mixed gas of a protective gas and a silicon source gas; the volume ratio of the protective gas to the silicon source gas is [1 - 10]:1, and the flow rate of the mixed gas is 8 L / h - 50 L / h; The protective gas is any one of hydrogen, nitrogen, and argon; The silicon source gas is one or more of silane, disilane, trisilane, tetrasilane, chlorosilane, and hexachlorosilane; The heating temperature of the chemical vapor deposition is 500 °C - 950 °C, and the heat preservation time is 4 hours - 12 hours.

8. An electrode composite material prepared by the preparation method according to any one of claims 1-7 above, characterized in that, The electrode composite material includes a soft carbon material, a hard carbon material coated on the surface of the soft carbon material, and nano-silicon particles deposited in the pores of the hard carbon material and the pores of the soft carbon material.

9. The electrode composite material according to claim 8, characterized in that, The particle size Dv50 of the electrode composite material is 5 μm - 13 μm; The percentage of the mass of the soft carbon material in the total mass of the electrode composite material is 5% - 55%; The percentage of the mass of the hard carbon material in the total mass of the electrode composite material is 4% - 45%; The percentage of the mass of the nano-silicon particles in the total mass of the electrode composite material is 5% - 45%; The specific surface area of the electrode composite material is 1500 m 2 / g - 2000 m 2 / g; the pore diameter of the pores of the electrode composite material is between 2 nm and 5 nm.

10. A supercapacitor, characterized in that, The supercapacitor includes the electrode composite material described in claim 8 above.

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