Composite active material and preparation method and application thereof

Abstract

The invention belongs to the technical field of negative electrode materials, and provides a composite active material and a preparation method and application thereof. The preparation method comprises the following steps: compounding an active component and a carbon skeleton to obtain composite particles; and performing high-temperature heat treatment or chemical vapor deposition on the carbon precursor, and generating a carbon coating layer on the surface of the composite particle to obtain the composite active material. According to the preparation method disclosed by the invention, the active components with high specific capacity can be uniformly dispersed in the carbon skeleton, nano-scale uniform distribution of the active components in the carbon skeleton is realized by controlling ball milling time, ball milling medium types and the like, and the specific surface area and the pore structure of the composite active material are optimized by regulating and controlling the mass ratio of the active components to the carbon skeleton; by accurately controlling the thickness and the microstructure of the carbon coating layer, the cycle stability is improved, the first-circle specific capacity of the prepared composite negative electrode material at 0.1 C exceeds 1000mAh / g, and the capacity retention ratio after 300 cycles is greater than or equal to 65%.

Description

Technical Field

[0001] The present invention relates to the technical field of anode materials, and particularly to a composite active material, a preparation method thereof, and an application thereof. Background Art

[0002] Anode materials with high specific capacity (such as silicon, silicon oxide, tin-based alloys, red phosphorus, etc.) can theoretically endow lithium-ion batteries with excellent lithium storage capacity, making the lithium storage capacity of lithium-ion batteries far exceed that of traditional graphite anodes. However, high specific capacity anode materials face problems such as volume expansion, poor electrical conductivity, and unstable electrical contact during charge and discharge. At present, uniformly coating, embedding, or compounding high specific capacity active components in a carbon skeleton to form a composite material is a key technical means to improve interfacial stability, inhibit volume expansion, and enhance electron transfer efficiency, and can effectively solve the above problems. However, current composite materials are mostly prepared by mechanical mixing or coating methods, resulting in uneven dispersion of high specific capacity active components, weak interfacial bonding, and poor repeatability of the method, directly affecting the electrochemical performance of the anode material.

[0003] Therefore, providing a preparation method for high specific capacity composite active materials to uniformly load high specific capacity active components on a carbon skeleton is crucial for the development of lithium-ion batteries. Summary of the Invention

[0004] The purpose of the present invention is to provide a composite active material, a preparation method thereof, and an application thereof in view of the deficiencies of the prior art.

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

[0006] The present invention provides a preparation method for a composite active material, comprising the following steps:

[0007] 1) Compounding an active component and a carbon skeleton to obtain composite particles;

[0008] 2) Performing high-temperature heat treatment or chemical vapor deposition on a carbon precursor to form a carbon coating layer on the surface of the composite particles, thereby obtaining the composite active material;

[0009] The compounding in step 1) adopts wet ball milling or sol-gel method.

[0010] Preferably, the active component in step 1) is silicon, silicon oxide, tin-based alloy, or red phosphorus, and the particle size of the active component is 10-100 nm.

[0011] Preferably, the carbon skeleton in step 1) is hard carbon, graphite, carbon black, petroleum coke, needle coke, or microporous carbon, and the specific surface area of the carbon skeleton is 200-500 m 2 / g.

[0012] Preferably, the mass ratio of the active component to the carbon skeleton in step 1) is 1:2 - 5, and the thickness of the carbon coating layer in step 2) is 5 - 30 nm.

[0013] Preferably, the medium used for wet ball milling is anhydrous ethanol or N-methylpyrrolidone. The mass-volume ratio of the carbon skeleton to the medium is 1 g:8 - 12 mL, the ball-to-material ratio is 8 - 12:1, the rotation speed of wet ball milling is 300 - 500 rpm, and the time of wet ball milling is 1 - 3 h.

[0014] Preferably, in the sol-gel method, the active component and the carbon skeleton are dispersed in a precursor solution to form a sol-gel system, and then composite particles are obtained through drying and heat treatment.

[0015] Preferably, when the carbon precursor is glucose, phenolic resin or coal tar pitch, a carbon coating layer is formed by high-temperature heat treatment;

[0016] When the carbon precursor is acetylene, a carbon coating layer is formed by chemical vapor deposition.

[0017] Preferably, the temperature of the high-temperature heat treatment is 600 - 1200 °C, and the time of the high-temperature heat treatment is 1 - 3 h.

[0018] The present invention also provides a composite active material prepared by the preparation method described above.

[0019] The present invention also provides an application of the composite active material in the anode material of a lithium-ion battery.

[0020] The beneficial effects of the present invention include the following points:

[0021] 1) The preparation method of the present invention can uniformly disperse active components with high specific capacity (including silicon, silicon oxide, tin-based alloy, red phosphorus) in the carbon skeleton, achieve stable binding, improve the first-cycle specific capacity and service life of the anode material. The first-cycle specific capacity exceeds 1000 mAh / g at 0.1C, the capacity retention rate after 100 cycles is ≥80%, and the capacity retention rate after 300 cycles is ≥65%.

[0022] 2) The present invention controls the ball milling time, the type of ball milling medium, etc., to achieve a nanoscale uniform distribution of active components in the carbon skeleton and reduce the particle aggregation rate (lower than 10%); by regulating the mass ratio, particle size and interfacial bonding mode of the active component and the carbon skeleton, the specific surface area and pore structure of the composite active material are optimized, thereby improving the conductivity of the composite active material and enhancing the electrochemical performance; by precisely controlling the thickness and microstructure of the carbon coating layer, the electrochemical activity and mechanical stress buffering are balanced, the performance decay caused by material expansion is reduced, and the cycle stability is improved.

[0023] 3) The composite active material of the present invention can be used to prepare a composite negative electrode together with an aqueous binder, a three-dimensional conductive network, and a surface-treated carbon fiber substrate, providing high energy density and long service life in the integrated application of structure and energy storage. Detailed implementation manners

[0024] The present invention provides a preparation method of a composite active material, comprising the following steps:

[0025] 1) Composite the active component and the carbon skeleton to obtain composite particles;

[0026] 2) Perform high-temperature heat treatment or chemical vapor deposition on the carbon precursor to form a carbon coating layer on the surface of the composite particles, thus obtaining the composite active material;

[0027] In step 1), the composite is carried out by wet ball milling or sol-gel method.

[0028] In the present invention, the active component in step 1) is preferably silicon, silicon oxide, tin-based alloy or red phosphorus, and the particle size of the active component is preferably 10-100 nm, more preferably 20-80 nm, and even more preferably 50 nm.

[0029] In the present invention, the carbon skeleton in step 1) is preferably hard carbon, graphite, carbon black, petroleum coke, needle coke or microporous carbon, and the specific surface area of the carbon skeleton is preferably 200-500 m 2 / g, more preferably 300-400 m 2 / g, and even more preferably 350 m 2 / g.

[0030] In the present invention, the mass ratio of the active component to the carbon skeleton in step 1) is preferably 1:2-5, more preferably 1:3-4, and even more preferably 1:3.5; the thickness of the carbon coating layer in step 2) is preferably 5-30 nm, more preferably 10-25 nm, and even more preferably 15-20 nm.

[0031] In the present invention, the medium used for wet ball milling is preferably anhydrous ethanol or N-methylpyrrolidone, and the mass-volume ratio of the carbon skeleton to the medium is preferably 1 g:8-12 mL, more preferably 1 g:9-11 mL, and even more preferably 1 g:10 mL; the ball-to-material ratio is preferably 8-12:1, more preferably 9-11:1, and even more preferably 10:1; the rotation speed of wet ball milling is preferably 300-500 rpm, more preferably 350-450 rpm, and even more preferably 400 rpm; the time of wet ball milling is preferably 1-3 h, more preferably 1.5-2.5 h, and even more preferably 2 h.

[0032] In the present invention, the sol-gel method preferably involves dispersing the active component and the carbon skeleton in a precursor solution to form a sol-gel system, followed by drying and heat treatment to obtain composite particles.

[0033] In the present invention, when the carbon precursor is glucose, phenolic resin or coal tar pitch, high-temperature heat treatment is preferably used to generate a carbon coating layer;

[0034] When the carbon precursor is acetylene, chemical vapor deposition is preferably used to generate a carbon coating layer.

[0035] In the present invention, the temperature of the high-temperature heat treatment is preferably 600-1200 °C, more preferably 800-1000 °C, and even more preferably 900 °C; the time of the high-temperature heat treatment is preferably 1-3 h, more preferably 1.5-2.5 h, and even more preferably 2 h.

[0036] The present invention also provides a composite active material prepared by the preparation method described above.

[0037] The present invention also provides the application of the composite active material in the anode material of a lithium-ion battery.

[0038] 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 protection scope of the present invention.

[0039] Example 1

[0040] Silicon nanoparticles and hard carbon powder with a mass ratio of 1:4 were mixed and placed in a planetary ball mill. The particle size of the silicon nanoparticles was 50 nm, and the specific surface area of the hard carbon powder was 350 m 2 / g. Anhydrous ethanol was added to the planetary ball mill (the mass-volume ratio of hard carbon powder to anhydrous ethanol was 1 g:10 mL), and ball milling was carried out at a ball-to-material ratio of 10:1 and a rotation speed of 400 rpm for 2 h to obtain composite particles.

[0041] Using anhydrous ethanol as a solvent, a Novolak-type phenolic resin solution with a mass fraction of 15% was prepared. In an argon atmosphere, the composite particles were dispersed in the Novolak-type phenolic resin solution, stirred at a rotation speed of 300 rpm for 30 min, and then placed under reduced pressure drying at 70 °C and -0.05 MPa for 4 h. Subsequently, carbonization was carried out at 800 °C for 2 h to form a carbon coating layer with a thickness of 15 nm, thereby obtaining the composite active material.

[0042] Example 2

[0043] Disperse tetraethyl orthosilicate in absolute ethanol (the volume ratio of tetraethyl orthosilicate to absolute ethanol is 1:2), and while stirring at a speed of 30 rpm, dropwise add ammonia water with a mass concentration of 15% (the volume ratio of tetraethyl orthosilicate to ammonia water is 1:5) at a rate of 10 drops / min to cause the hydrolysis and condensation reaction of tetraethyl orthosilicate to obtain a precursor solution.

[0044] Disperse silicon dioxide nanoparticles with a mass ratio of 1:3 (the particle size of the silicon dioxide nanoparticles is 80 nm) and flake graphite powder (the specific surface area of the flake graphite powder is 500 m 2 / g) in the precursor solution, and stir at a speed of 50 rpm for 2 h to form a sol-gel system. Dry the sol-gel system at 80 °C for 6 h to obtain a composite xerogel. In an argon atmosphere, calcine the composite xerogel at 900 °C for 2 h to form a tight intercalated structure between graphite and silicon dioxide to obtain composite particles.

[0045] Place the composite particles in an argon atmosphere, and introduce acetylene gas into the composite particles at a flow rate of 50 mL / min at 600 °C for 1 h of chemical vapor deposition to form a carbon coating layer with a thickness of 20 nm, that is, obtain the composite active material.

[0046] Example 3

[0047] Mix tin-cobalt alloy nanoparticles with a mass ratio of 1:2 and hard carbon powder and place them in a planetary ball mill. The particle size of the tin-cobalt alloy nanoparticles is 20 nm, the mass ratio of tin to cobalt in the tin-cobalt alloy nanoparticles is 6:4, and the specific surface area of the hard carbon powder is 300 m 2 / g. Add absolute ethanol to the planetary ball mill (the mass-volume ratio of hard carbon powder to absolute ethanol is 1 g:10 mL), and ball mill at a ball-to-material ratio of 10:1 and a speed of 300 rpm for 1 h to obtain composite particles.

[0048] Mix coal tar pitch (the coal tar pitch is medium-temperature coal tar pitch produced by Hebei Shengshuhui New Energy Technology Co., Ltd., and the softening point is 110 °C) with the composite particles and place them in an argon atmosphere, and treat them at 1000 °C for 1 h to form a carbon coating layer with a thickness of 15 nm, that is, obtain the composite active material.

[0049] Example 4

[0050] Mix red phosphorus powder and microporous carbon with a mass ratio of 1:5 and place them in a planetary ball mill. The particle size of the red phosphorus powder is 20 nm, and the specific surface area of the microporous carbon is 500 m 2 / g. Add N-methylpyrrolidone to the planetary ball mill (the mass-volume ratio of microporous carbon to N-methylpyrrolidone is 1 g:10 mL), and ball mill at a ball-to-material ratio of 10:1 and a speed of 400 rpm for 3 h to obtain composite particles.

[0051] Mix coal tar pitch (the coal tar pitch is medium-temperature coal tar pitch produced by Hebei Shengshuhui New Energy Technology Co., Ltd., with a softening point of 110 °C) with composite particles and place them in an argon atmosphere, and treat them at 700 °C for 2 h to form a carbon coating layer with a thickness of 15 nm, thus obtaining the composite active material.

[0052] Separate the composite active materials of Examples 1 to 4, Ketjen black, and an aqueous binder to prepare a composite negative electrode. The mass ratio of the composite active material, Ketjen black, and the aqueous binder is 90:5:5. The aqueous binder contains polyacrylic acid (PAA) and sodium carboxymethyl cellulose / styrene-butadiene rubber (CMC / SBR). The mass ratio of PAA is 1.5% (dry basis), and the mass ratio of CMC / SBR is 3.5% (dry basis). Assemble the above composite negative electrode, lithium iron phosphate positive electrode, and bisphenol A epoxy resin-based polymer electrolyte into a lithium-ion battery. Assemble a CT-4008 silicon-carbon composite negative electrode, lithium iron phosphate positive electrode, and bisphenol A epoxy resin-based polymer electrolyte into a lithium-ion battery. Perform electrochemical performance tests on the lithium-ion batteries under 0.1C conditions, and the test results are shown in Table 1.

[0053] Table 1 Electrochemical performance test results of lithium-ion batteries

[0054]

[0055] As can be seen from Table 1, when the composite active materials of Examples 1 to 4 are used in the composite negative electrode of a lithium-ion battery, the initial specific capacity and the capacity retention rate from 100 to 300 cycles are significantly better than those of the CT-4008 silicon-carbon negative electrode. This result indicates that the composite active material prepared by the present invention can significantly improve the specific capacity and cycle stability of a lithium-ion battery when applied to the composite negative electrode.

[0056] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a composite active material, characterized in that: The following steps are included: 1) Compounding the active component and the carbon skeleton to obtain composite particles; 2) subjecting the carbon precursor to high temperature heat treatment or chemical vapor deposition to form a carbon coating layer on the surface of the composite particles to obtain a composite active material; Step 1) The compounding is carried out by wet ball milling or sol-gel method.

2. The preparation method according to claim 1, characterized in that: Step 1) The active component is silicon, silicon oxide, tin-based alloy or red phosphorus, and the particle size of the active component is 10 to 100 nm.

3. The preparation method according to claim 1 or 2, characterized in that: Step 1) The carbon skeleton is hard carbon, graphite, carbon black, petroleum coke, needle coke or microporous carbon, and the specific surface area of ​​the carbon skeleton is 200 to 500 m 2 / g.

4. The preparation method according to claim 3, characterized in that: In step 1), the mass ratio of the active component to the carbon skeleton is 1:2-5, and in step 2), the thickness of the carbon coating layer is 5-30 nm.

5. The preparation method according to claim 4, characterized in that: The medium used in the wet ball milling is anhydrous ethanol or N-methylpyrrolidone, the mass volume ratio of the carbon skeleton and the medium is 1g:8-12mL, the ball-to-material ratio is 8-12:1, the rotation speed of the wet ball milling is 300-500rpm, and the wet ball milling time is 1-3h.

6. The preparation method according to claim 4 or 5, characterized in that: The sol-gel method is to disperse the active components and the carbon skeleton in a precursor solution to form a sol-gel system, and then obtain composite particles through drying and heat treatment.

7. The preparation method according to claim 6, characterized in that: When the carbon precursor is glucose, phenolic resin or coal tar pitch, a high temperature heat treatment is used to generate a carbon coating layer; When the carbon precursor is acetylene, the carbon coating layer is formed by chemical vapor deposition.

8. The preparation method according to claim 7, characterized in that: The temperature of the high temperature heat treatment is 600-1200° C., and the time of the high temperature heat treatment is 1-3 hours.

9. The composite active material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the composite active material according to claim 9 in negative electrode materials for lithium ion batteries.

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