Porous silicon-carbon negative electrode material coated with fast ion conductor and preparation method therefor

Abstract

The present invention belongs to the technical field of negative electrode materials for lithium-ion batteries, and provides a porous silicon-carbon negative electrode material coated with a fast ion conductor and a preparation method therefor. The preparation method in the present invention comprises: pre-carbonizing a resin in a nitrogen atmosphere to obtain a carbon precursor; crushing the carbon precursor, then subjecting same and an alkali to solid-phase mixing, and sequentially performing an activating treatment and acid pickling on the mixture, so as to obtain a porous carbon material; preparing nano-silicon on the surface of the porous carbon material by subjecting a silane compound to a deposition reaction, so as to obtain a nano-silicon-deposited porous carbon substrate; introducing a carbon source gas under a protective gas atmosphere to perform chemical vapor deposition on the nano-silicon-deposited porous carbon substrate, so as to obtain a silane-deposited porous carbon composite material; and mixing the silane-deposited porous carbon composite material, a metal salt, a phosphate solution and an alkaline precipitant, and then sequentially performing a reflux reaction and a calcination treatment, thereby obtaining a porous silicon-carbon negative electrode material coated with a fast ion conductor. The silane-deposited porous carbon negative electrode material coated with a fast ion conductor prepared in the present invention has a stable structure, a high capacity and good cycle performance.

Description

A porous silicon-carbon negative electrode material coated with a fast ion conductor and a preparation method thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery negative electrode materials, and in particular relates to a porous silicon-carbon negative electrode material coated with a fast ion conductor and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries, as an important energy source for modern portable electronic devices and electric vehicles, have always been the focus of research in terms of energy density and cycle life. Silicon-based negative electrode materials, with a theoretical specific capacity of 4200 mAh / g, ten times that of traditional graphite negative electrodes, have attracted much attention. However, the significant volume change of silicon during charging and discharging leads to material pulverization and electrode failure, severely affecting the cycle life. To overcome these problems, researchers have attempted to improve the stability and conductivity of silicon-based negative electrodes through methods such as nanosizing silicon, composite material design, and surface coating. Despite the challenges, silicon-based negative electrode materials have great potential and application prospects in improving the energy density of lithium ion batteries.

[0003] Currently, the swelling of Si negative electrodes is mainly alleviated by nanosizing methods, such as preparing silicon into nanospheres and nanowires. However, conventional grinding methods can only control the size of Si particles to around 100 nm, and excessive nanosizing process also leads to an increase in the specific surface area of the material, affecting material processing and performance. To solve the bottleneck of controlling Si particle size with traditional grinding methods, patent CN 116314791 A uses porous carbon as a matrix and obtains a silicon-carbon composite material of nanosilicon and soft carbon through silane deposition. The amorphous carbon coating layer used in this preparation method may not provide sufficient mechanical strength and conductivity during high-rate charging and discharging, leading to the destruction of the electrode structure. Patent CN 116525805 A discloses a fast ion conductor coated silicon-based composite material and a preparation method thereof. By uniformly mixing silicon-oxygen materials, lithium-containing binders, and carbon nanotubes and then spray drying, a precursor material is obtained. Then, the precursor material is deposited with a fast ion conductor and amorphous carbon on the surface of the material through plasma method. The electronic conductivity and ionic conductivity of the prepared negative electrode material are both improved, but the high cost of the equipment, the high cost of the precursor, and the limited sample processing capacity limit its application. SUMMARY

[0004] The purpose of the present application is to provide a porous silicon-carbon negative electrode material coated with a fast ion conductor and a preparation method thereof, to solve the technical problems of low mechanical strength and poor ionic conductivity of existing silicon-carbon composite negative electrode materials.

[0005] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0006] The application provides a preparation method of a fast-ion-conductor-coated porous silicon-carbon negative electrode material.

[0007] (1) pre-carbonizing the resin under a nitrogen atmosphere to obtain a carbon precursor;

[0008] (2) crushing the carbon precursor and mixing it with an alkali in a solid phase, and then sequentially performing activation treatment and acid pickling on the mixture to obtain a porous carbon material;

[0009] (3) preparing nano-silicon on the surface of the porous carbon material through a deposition reaction of a silane compound to obtain a nano-silicon-deposited porous carbon substrate;

[0010] (4) performing chemical vapor deposition on the nano-silicon-deposited porous carbon substrate by introducing a carbon source gas under a protective gas atmosphere to obtain a silane-deposited porous carbon composite material;

[0011] (5) mixing the silane-deposited porous carbon composite material, a metal salt, a phosphate solution and an alkaline precipitant, and then sequentially performing a reflux reaction and calcination treatment to obtain the fast-ion-conductor-coated porous silicon-carbon negative electrode material.

[0012] Further, in the step (1), the resin comprises one or more of a phenolic resin, an epoxy resin and a furfural resin, the pre-carbonization temperature is 400-800 ℃, and the pre-carbonization time is 1-2 h.

[0013] Further, in the step (2), the alkali comprises one or more of potassium hydroxide, sodium hydroxide, calcium hydroxide, potassium carbonate and sodium carbonate, the particle size of the crushed carbon precursor is 2-50 μm, and the mass ratio of the carbon precursor to the alkali is 1:1-5.

[0014] The activation treatment temperature is 500-1000 ℃, and the activation treatment time is 1-4 h.

[0015] Further, in the step (3), the silane compound comprises monosilane and / or disilane, the deposition reaction is performed under a protective gas, the protective gas comprises one or more of nitrogen, argon and helium, the volume ratio of the silane compound to the protective gas is 1:10-1:1, and the flow rate of the silane compound is 0.5-2 L / min.

[0016] Further, in the step (3), the deposition reaction temperature is 500-1000 ℃, the deposition reaction time is 1-2 h, and the mass ratio of the Si skeleton in the silane compound to the C skeleton in the porous carbon material is 1:9-9:1.

[0017] Further, in the step (4), the carbon source gas comprises one or more of methane, ethane, propane, acetylene and propyne, the protective gas comprises one or more of nitrogen, argon and helium, the volume ratio of the carbon source gas and the protective gas is 1:10~1:1, the flow rate of the carbon source gas is 0.5~2L / min; the temperature of the chemical vapor deposition is 500~1000℃, and the time is 1~3h.

[0018] Further, in the step (5), the metal salt comprises one or more of chloride salt, nitrate salt, sulfate salt and organic acid salt; the phosphate salt solution comprises one or more of sodium dihydrogen phosphate solution, ammonium dihydrogen phosphate solution, disodium hydrogen phosphate solution and diammonium hydrogen phosphate solution, and the basic precipitant comprises one or more of ammonia, ethanolamine, sodium hydroxide and potassium hydroxide.

[0019] Further, in the step (5), the mixing is carried out in an organic solvent, and the organic solvent comprises one or more of methanol, ethanol, ethylene glycol, propanol, isopropanol, propylene glycol, n-butanol, acetonitrile and acetone.

[0020] In the mixed system, the concentration of the metal salt is 10-6~1.0mol / L, the concentration of the silane-deposited porous carbon composite material is 0.1~1000g / L, the concentration of the phosphate salt solution is 10-6~5mol / L, and the concentration of the basic precipitant is 10-6~10mol / L.

[0021] Further, in the step (5), the temperature of the reflux reaction is 10~200℃, and the time of the reflux reaction is 2~5h.

[0022] The temperature of the calcination treatment is 100~600℃, and the time of the calcination treatment is 1~5h.

[0023] The application provides a porous silicon-carbon negative electrode material coated with a fast ion conductor.

[0024] The application has the following beneficial effects:

[0025] (1) The application adopts a chemical activation method to prepare a high-porosity porous carbon material, and nanosilicon is generated in situ by depositing silane in the pores. Since the high-porosity porous carbon provides abundant deposition sites, the silicon content in the material is significantly increased, thereby effectively improving the capacity of the electrode.

[0026] (2) The present application realizes secondary coating on the surface of silicon-carbon negative electrode material by co-precipitation of phosphorus source and metal salt. The method of the present application is simple, easy to operate, mild, widely applicable, environmentally friendly, and suitable for industrial production. The method of the present application in-situ grows a uniform and continuous fast-ion conductor coating layer on the surface of silicon-carbon negative electrode material by chemical reaction. The coating layer not only prevents direct contact between negative electrode active material and electrolyte solution, thereby reducing side reactions, but also significantly improves the cycle performance and rate performance of negative electrode material by accelerating the diffusion speed of lithium ions. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a flow chart of the preparation of the fast-ion conductor coated porous silicon-carbon negative electrode material of the present application. DETAILED DESCRIPTION

[0028] The present application provides a preparation method of fast-ion conductor coated porous silicon-carbon negative electrode material, comprising the following steps:

[0029] (1) Pre-carbonization of resin under nitrogen atmosphere to obtain carbon precursor;

[0030] (2) Solid-phase mixing of the broken carbon precursor with alkali, followed by activation treatment and acid washing of the mixture to obtain porous carbon material;

[0031] (3) Preparation of nano-silicon on the surface of the porous carbon material by deposition reaction of silane compound to obtain nano-silicon deposited porous carbon substrate;

[0032] (4) Chemical vapor deposition of the nano-silicon deposited porous carbon substrate by introducing carbon source gas under a protective gas atmosphere to obtain silane deposited porous carbon composite material;

[0033] (5) Mixing of the silane deposited porous carbon composite material, metal salt, phosphate solution and alkaline precipitant, followed by reflux reaction and calcination treatment to obtain fast-ion conductor coated porous silicon-carbon negative electrode material.

[0034] In the present application, in step (1), the resin comprises one or more of phenolic resin, epoxy resin and furfural resin, preferably phenolic resin; the pre-carbonization temperature is 400-800℃, preferably 500-700℃, and further preferably 550-650℃; the pre-carbonization time is 1-2h, preferably 1h.

[0035] In the present application, in step (2), the alkali comprises one or more of potassium hydroxide, sodium hydroxide, calcium hydroxide, potassium carbonate and sodium carbonate, preferably potassium hydroxide; the particle size of the broken carbon precursor is 2-50μm, preferably 10-40μm, and further preferably 20-30μm; the mass ratio of the carbon precursor to alkali is 1:1-5, preferably 1:2-4, and further preferably 1:3.

[0036] In the present application, in step (2), the temperature of the activation treatment is 500-1000℃, preferably 600-900℃, and further preferably 700-800℃; the time of the activation treatment is 1-4h, preferably 2-3h.

[0037] In the present application, in step (3), the silane compound comprises monosilane and / or disilane, preferably monosilane; the deposition reaction is carried out under a protective gas, which comprises one or more of nitrogen, argon and helium, preferably nitrogen; the volume ratio of the silane compound to the protective gas is 1:10-1:1, preferably 1:9-1:2, further preferably 1:8-1:5, and more preferably 1:6; the flow rate of the silane compound is 0.5-2L / min, preferably 1L / min.

[0038] In the present application, in step (3), the temperature of the deposition reaction is 500-1000℃, preferably 600-900℃, and further preferably 700-800℃; the time of the deposition reaction is 1-2h, preferably 1h; the mass ratio of the Si skeleton in the silane compound to the C skeleton in the porous carbon material is 1:9-9:1, preferably 2:8-8:2, and further preferably 5:5.

[0039] In the present application, in step (4), the carbon source gas comprises one or more of methane, ethane, propane, acetylene and propyne, preferably acetylene and / or propyne; the protective gas comprises one or more of nitrogen, argon and helium, preferably nitrogen; the volume ratio of the carbon source gas to the protective gas is 1:10-1:1, preferably 1:9-1:2, and further preferably 1:6; the flow rate of the carbon source gas is 0.5-2L / min, preferably 1L / min; the temperature of the chemical vapor deposition is 500-1000℃, preferably 600-900℃, and further preferably 700-800℃; the time is 1-3h, preferably 2h.

[0040] In the present application, in step (5), the metal salt comprises one or more of chloride, nitrate, sulfate and organic acid salt; preferably one or more of lithium nitrate, aluminum chloride and vanadium sulfate.

[0041] In the present application, in step (5), the phosphate solution comprises one or more of sodium dihydrogen phosphate solution, ammonium dihydrogen phosphate solution, disodium hydrogen phosphate solution and diammonium hydrogen phosphate solution, preferably disodium hydrogen phosphate solution; the alkaline precipitant comprises one or more of ammonia, ethanolamine, sodium hydroxide and potassium hydroxide, preferably ethanolamine and / or sodium hydroxide.

[0042] In the present application, the mixing in step (5) is carried out in an organic solvent, which comprises one or more of methanol, ethanol, ethylene glycol, propanol, isopropanol, propylene glycol, n-butanol, acetonitrile and acetone, preferably one or more of methanol, ethanol, ethylene glycol, propanol and isopropanol.

[0043] In the present application, in the mixing system in step (5), the concentration of the metal salt is 10-6~1.0 mol / L, preferably 10-5~0.1 mol / L, and further preferably 10-4~0.01 mol / L; the concentration of the silane-deposited porous carbon composite material is 0.1~1000 g / L, preferably 1~100 g / L, and further preferably 10~80 g / L; the concentration of the phosphate solution is 10-6~5 mol / L, preferably 10-5~1 mol / L, and further preferably 10-4~0.01 mol / L; and the concentration of the alkaline precipitant is 10-6~10 mol / L, preferably 10-5~1 mol / L, and further preferably 10-4~0.1 mol / L.

[0044] In the present application, in step (5), the temperature of the reflux reaction is 10~200℃, preferably 50~150℃, and further preferably 80~100℃; and the time of the reflux reaction is 2~5 h, preferably 3~4 h.

[0045] In the present application, in step (5), the temperature of the calcination treatment is 100~600℃, preferably 200~400℃, and further preferably 300~350℃; and the time of the calcination treatment is 1~5 h, preferably 2~4 h, and further preferably 3 h.

[0046] The present application provides a porous silicon-carbon negative electrode material coated with a fast ion conductor.

[0047] The technical solutions provided by the present application will be described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present application. Example 1

[0048] (1) Dissolve the phenolic resin in ethanol, and dry the mixed solution in which the phenolic resin is dissolved while stirring, with a drying temperature of 100℃, to obtain a carbon source;

[0049] (2) Pre-carbonize the carbon source at a pre-carbonization temperature of 550℃ for 1 h to obtain a pre-carbonized carbon precursor, then crush it, with a crushed particle size controlled at 20 μm, and mix the crushed powder with KOH powder in a solid phase, with a mass ratio of the powder to KOH being 1:2, and place it in an activation furnace for activation at 800℃ for 2 h, and finally wash and remove the residual alkali with hydrochloric acid and deionized water, and dry to obtain a porous carbon material;

[0050] (3) The porous carbon material is placed in a vapor deposition furnace, heated to 500°C under a nitrogen atmosphere, and a deposition reaction is carried out by passing in silane / nitrogen at a flow rate of 0.5 / 3 L / min. After 60 min of heat preservation, silane is stopped, and nitrogen is still passed in at a flow rate of 3 L / min;

[0051] (4) The temperature is raised to 800°C, and a chemical vapor deposition reaction is carried out by passing in acetylene / hydrogen at a flow rate of 0.5 / 3 L / min. After 120 min of heat preservation, hydrogen is kept being passed in at a flow rate of 3 L / min during the cooling process, and the temperature is lowered to room temperature to obtain a silane-deposited porous carbon composite material;

[0052] (5) 0.2 g of the silane-deposited porous carbon composite material, 0.046 g of lithium nitrate, 0.0448 g of disodium hydrogen phosphate, and 0.5 g of a precipitant, ammonia, are mixed in 30 ml of isopropyl alcohol, and the pH is adjusted to about 2 with ammonia. The mixture is stirred and refluxed at 90°C for 3 hours. After centrifugation, washing, and drying, the obtained particles are calcined at 300°C for 2 hours to obtain a fast-ion-conductor-coated porous silicon-carbon negative electrode material. Example 2

[0053] (1) The epoxy resin is dissolved in ethanol, and the mixed solution in which the phenol formaldehyde resin is dissolved is dried while being stirred, with a drying temperature of 100°C, to obtain a carbon source;

[0054] (2) The carbon source is pre-carbonized at a temperature of 550°C for 1 h to obtain a pre-carbonized carbon precursor, which is then pulverized to a particle size of 20 μm. The pulverized powder is mixed with NaOH powder in a solid phase, with a mass ratio of the powder to NaOH being 1:2. The mixture is placed in an activation furnace and activated at 700°C for 2 h. Finally, hydrochloric acid and deionized water are used to wash and remove residual alkali, and the mixture is dried to obtain a porous carbon material;

[0055] (3) The porous carbon material is placed in a vapor deposition furnace, heated to 600°C under an argon atmosphere, and a deposition reaction is carried out by passing in silane / argon at a flow rate of 0.5 / 4 L / min. After 60 min of heat preservation, silane is stopped, and argon is still passed in at a flow rate of 4 L / min;

[0056] (4) The temperature is raised to 900°C, and a chemical vapor deposition reaction is carried out by passing in acetylene / hydrogen at a flow rate of 0.5 / 4 L / min. After 120 min of heat preservation, hydrogen is kept being passed in at a flow rate of 4 L / min during the cooling process, and the temperature is lowered to room temperature to obtain a silane-deposited porous carbon composite material;

[0057] (5) 0.2 g of the silane-deposited porous carbon composite material, 0.046 g of lithium nitrate, 0.0448 g of disodium hydrogen phosphate, and 0.5 g of the precipitant ammonia were mixed in 30 ml of isopropyl alcohol, and the pH was adjusted to about 2 with ammonia; under stirring, the reaction was carried out at 90°C under reflux for 3 hours, and the obtained particles were calcined at 350°C for 2 hours after centrifugation, washing, and drying, to obtain a fast ionic conductor-coated porous silicon-carbon negative electrode material. Example 3

[0058] Compared with Example 1, only the phenolic resin was changed to furfural resin, and the other steps were the same. Example 4

[0059] Compared with Example 1, only the lithium nitrate was changed to aluminum chloride, and the other steps were the same.

[0060] Application Example

[0061] A method for assembling a lithium ion battery from a negative electrode material coated with a fast ionic conductor and testing the charge and discharge performance of the lithium ion battery, comprising the following steps:

[0062] A binder, a conductive agent, and single-walled carbon nanotubes (SCNT) were added to the negative electrode material, and stirring was performed to prepare a slurry, which was coated on a copper foil, and then dried and rolled to obtain a negative electrode sheet; the binder used was LA132, the conductive agent used was conductive carbon black (SP), and the amount ratio of the negative electrode material, LA123, SP, and SCNT was 94:4:1:1. LiPF6 was used as the electrolyte in the electrolyte used, with a concentration of 1.2 mol / L, and the solvent was a mixture of EC and DEC in a volume ratio of 1:1; a lithium metal sheet was used as the counter electrode, a polypropylene (PP) membrane was used as the separator, and a button cell was assembled in an argon-filled glove box. The charge and discharge performance was tested on a Wuhan Lan Battery CT2001A battery tester, the charge and discharge voltage range was 0.005V-2.0V, the charge and discharge rate was 0.1C, and the rate performance (0.1C-2.0C) was tested.

[0063] The performance of the lithium ion battery obtained in the example was tested, and the test results are shown in Table 1 below.

[0064] Table 1 Performance test results

[0065]

[0066] From the above examples, the application provides a kind of fast ion conductor coated porous silicon carbon negative electrode material and its preparation method.The high pore volume porous carbon material is prepared by chemical activation method in the application, and nano-silicon is generated in situ deposition in pore by silane.Due to the high pore volume of porous carbon providing abundant deposition sites, which significantly increases the silicon content in the material, thereby effectively improving the capacity of the electrode.The structure of the fast ion conductor coated silane deposition porous carbon negative electrode material prepared by the method of the application is stable, the capacity is high, and the cycle performance is good.

[0067] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a fast-ion conductor-coated porous silicon-carbon anode material, characterized by, The method comprises the following steps: (1) pre-carbonizing the resin under a nitrogen atmosphere to obtain a carbon precursor; (2) crushing the carbon precursor and mixing it with an alkali in a solid phase, then sequentially performing activation treatment and acid washing on the mixture to obtain a porous carbon material; (3) preparing nano-silicon on the surface of the porous carbon material through a deposition reaction of a silane compound to obtain a nano-silicon deposited porous carbon substrate; (4) performing chemical vapor deposition on the nano-silicon deposited porous carbon substrate by introducing a carbon source gas under a protective gas atmosphere to obtain a silane deposited porous carbon composite material; (5) mixing the silane deposited porous carbon composite material, a metal salt, a phosphate solution and an alkaline precipitant, then sequentially performing a reflux reaction and calcination treatment to obtain a fast ionic conductor coated porous silicon-carbon negative electrode material.

2. The production method according to claim 1, characterized by, In the step (1), the resin comprises one or more of a phenolic resin, an epoxy resin and a furfural resin, the pre-carbonization temperature is 400-800°C, and the pre-carbonization time is 1-2h.

3. The production method according to claim 1 or 2, characterized by, In the step (2), the alkali comprises one or more of potassium hydroxide, sodium hydroxide, calcium hydroxide, potassium carbonate and sodium carbonate, the particle size of the crushed carbon precursor is 2-50μm, and the mass ratio of the carbon precursor to the alkali is 1:1-5; The activation treatment temperature is 500-1000°C, and the activation treatment time is 1-4h.

4. The preparation method according to claim 3, characterized in that, In the step (3), the silane compound comprises monosilane and / or disilane, the deposition reaction is performed under a protective gas, the protective gas comprises one or more of nitrogen, argon and helium, the volume ratio of the silane compound to the protective gas is 1:10-1:1, and the flow rate of the silane compound is 0.5-2L / min.

5. The production method according to claim 1 or 4, characterized by, In the step (3), the deposition reaction temperature is 500-1000°C, the deposition reaction time is 1-2h, and the mass ratio of the Si skeleton in the silane compound to the C skeleton in the porous carbon material is 1:9-9:

1.

6. The production method according to claim 1 or 2 or 4, characterized by, In the step (4), the carbon source gas comprises one or more of methane, ethane, propane, acetylene and propyne, the protective gas comprises one or more of nitrogen, argon and helium, the volume ratio of the carbon source gas to the protective gas is 1:10-1:1, and the flow rate of the carbon source gas is 0.5-2L / min; the chemical vapor deposition temperature is 500-1000°C, and the time is 1-3h.

7. The preparation method according to claim 6, characterized in that, In the step (5), the metal salt comprises one or more of a chloride salt, a nitrate salt, a sulfate salt and an organic acid salt; the phosphate solution comprises one or more of a sodium dihydrogen phosphate solution, an ammonium dihydrogen phosphate solution, a disodium hydrogen phosphate solution and a diammonium hydrogen phosphate solution; and the alkaline precipitant comprises one or more of ammonia, ethanolamine, sodium hydroxide and potassium hydroxide.

8. The production method according to claim 1 or 7, characterized by, In the step (5), the mixing is performed in an organic solvent, and the organic solvent comprises one or more of methanol, ethanol, ethylene glycol, propanol, isopropanol, propylene glycol, n-butanol, acetonitrile and acetone; In the mixed system, the concentration of the metal salt is 10 -6 1.0 mol / L, the concentration of the silane deposition porous carbon composite material is 0.1-1000 g / L, the concentration of the phosphate solution is 10 -6 5 mol / L, and the concentration of the alkaline precipitant is 10 -6 10 mol / L.

9. The production method according to claim 8, characterized by, In the step (5), the reflux reaction temperature is 10-200°C, and the reflux reaction time is 2-5h; The calcination treatment temperature is 100-600°C, and the calcination treatment time is 1-5h.

10. The porous silicon-carbon negative electrode material coated with the fast ionic conductor prepared by the method according to any one of claims 1 to 9.

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