A high-capacity hard carbon negative electrode material for sodium-ion batteries and a preparation method thereof

Abstract

A high-capacity hard carbon negative electrode material for sodium-ion batteries and a preparation method thereof belong to the technical field of sodium-ion batteries. The specific scheme is as follows: A high-capacity hard carbon negative electrode material for sodium-ion batteries includes granular porous hard carbon materials, carbon nanotubes, and organic pyrolysis carbon. The carbon nanotubes are interspersed between the granular porous hard carbon materials and the organic pyrolysis carbon, and the organic pyrolysis carbon is embedded or attached inside or on the surface of the granular porous hard carbon materials. For the hard carbon negative electrode material provided by the present invention, the granular porous structure provides a large number of active sites for sodium ions during the charge and discharge process, improving the capacity of the material. By adjusting the proportion of different pore types through a high-temperature carbonization process, the sodium storage sites of the material are increased. At the same time, the organic pyrolysis carbon and highly conductive carbon nanotubes are embedded therein, improving the conductivity of the material, reducing the internal resistance of the particles, and improving the rate performance of the material.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium-ion batteries, and particularly relates to a high-capacity hard carbon negative electrode material for sodium-ion batteries and a preparation method thereof. Background Art

[0002] With the depletion of fossil fuels and the exacerbation of environmental pollution problems, the utilization of renewable clean energies such as wind energy and solar energy has attracted more and more attention. However, these renewable energies are volatile and intermittent due to the influence of the natural environment, and it is difficult to achieve a stable output to the power grid. Energy storage systems are crucial for the efficient utilization of renewable energies. Among many energy storage technologies, lithium-ion batteries have fully occupied the markets of portable electronic devices and new energy electric vehicles due to their advantages such as high energy density, high power density, and long cycle life. However, the limited reserves and uneven distribution of lithium limit the large-scale application of lithium-ion batteries in the energy storage field. Sodium, which has similar physical and chemical properties to lithium, is rich in reserves, widely distributed, and low in cost, making sodium-ion batteries have broad application prospects in large-scale power grid energy storage.

[0003] At present, hard carbon materials have the advantages of rich raw material resources, low cost, and good rate performance, and are expected to become candidates for commercial negative electrode materials for sodium-ion batteries. However, hard carbon materials have problems such as low reversible capacity and too large specific surface area, resulting in low initial Coulomb efficiency, thereby affecting the long cycle performance of sodium-ion batteries. Summary of the Invention

[0004] The first object of the present invention is to solve the problems of low reversible specific capacity, too large specific surface area, and low initial Coulomb efficiency of existing hard carbon negative electrode materials, and to provide a high-capacity hard carbon negative electrode material for sodium-ion batteries.

[0005] The second object of the present invention is to provide a preparation method of a high-capacity hard carbon negative electrode material for sodium-ion batteries.

[0006] To achieve the above objects, the technical solutions adopted by the present invention are as follows:

[0007] A high-capacity hard carbon negative electrode material for sodium-ion batteries, comprising granular porous hard carbon materials, carbon nanotubes, and organic pyrolysis carbon. The carbon nanotubes are interspersed between the granular porous hard carbon materials and the organic pyrolysis carbon, and the organic pyrolysis carbon is embedded in or attached to the inside or surface of the granular porous hard carbon materials.

[0008] Further, the granular porous hard carbon materials have a short-range ordered and long-range disordered microstructural feature, and the average pore diameter of the granular porous hard carbon materials is 1-150 nm, and the volume ratio of micropores, mesopores, and macropores is 1:(50-100):(5-50).

[0009] Furthermore, the BET specific surface area of the granular porous hard carbon material is 1 to 200 m 2 / g.

[0010] Furthermore, the granular porous hard carbon material has a layered structure, and the layer spacing d 002 value is 0.345 to 0.385 nm.

[0011] A preparation method of the hard carbon negative electrode material for a high-capacity sodium-ion battery, characterized by comprising the following steps:

[0012] Step 1: Treat plant materials through a high-temperature carbonization process in an inert atmosphere to obtain a granular porous hard carbon material;

[0013] Step 2: Mix the granular porous hard carbon material evenly with a pyrolytic carbon organic precursor and carbon nanotubes, and then perform high-temperature pyrolysis in an inert atmosphere to obtain a primary pyrolysis product;

[0014] Step 3: After crushing the primary pyrolysis product, mix it evenly with the pyrolytic carbon organic precursor and carbon nanotubes again, and perform high-temperature pyrolysis in an inert atmosphere to obtain a secondary pyrolysis product;

[0015] Step 4: Calcinate the secondary pyrolysis product at a high temperature in an inert atmosphere, and obtain the hard carbon negative electrode material for a high-capacity sodium-ion battery after sieving.

[0016] Furthermore, in Step 1, the plant materials include one of corn stalks, corn cobs, pomelo peels, rice husks, walnut shells, cotton, chestnut shells, coconut shells, peanut shells, apricot shells, peach shells, and sugarcane bagasse.

[0017] Furthermore, in Step 1, the specific steps of the high-temperature carbonization process are: carbonize at 500 to 2200 °C for 1 to 10 h, and when the temperature is lowered to 100 - 350 °C, introduce a nitrogen-oxygen mixed gas with a ratio of (5 - 10):1, and keep it warm for 1 - 5 h to obtain the granular porous hard carbon material.

[0018] Furthermore, in Step 2 and Step 3, the pyrolytic carbon organic precursor includes resin materials or asphalt materials. The resin materials include one of epoxy resin, acrylic resin, polyester resin, phenolic resin, and amino resin; the asphalt materials include petroleum asphalt or coal tar pitch.

[0019] Furthermore, in Step 2 and Step 3, the high-temperature pyrolysis temperature is 200 to 2000 °C, and the time is 1 to 10 h; in Step 4, the high-temperature calcination temperature is 1000 to 3000 °C, and the time is 1 to 10 h.

[0020] Further, in step two, the pyrolytic carbon organic precursor accounts for 1%-20% of the granular porous hard carbon material, and the carbon nanotubes account for 0.1%-10% of the granular porous hard carbon material; in step three, the pyrolytic carbon organic precursor accounts for 1%-20% of the primary pyrolysis material, and the carbon nanotubes account for 0.1%-10% of the primary pyrolysis material.

[0021] The beneficial effects of the present invention compared with the prior art are as follows:

[0022] The hard carbon negative electrode material provided by the present invention has a granular porous structure that provides a large number of active sites for sodium ions during charge and discharge, improving the capacity of the material. By adjusting the ratio of different pore types through a high-temperature carbonization process, the carbon layer spacing is improved. Low-temperature oxidation can react with the organic matter forming closed pores, opening the closed pores in the material and increasing the number of micropores and mesopores, further improving the sodium storage sites of the material. At the same time, the pyrolytic carbon of the organic matter and the highly conductive carbon nanotubes are embedded therein, improving the conductivity of the material, reducing the internal resistance of the particles, and improving the rate performance of the material. The hard carbon negative electrode material of the present invention not only has a high capacity, but also reduces the volume expansion of the material during charge and discharge through a porous structure design. At the same time, highly conductive carbon nanotubes and microcrystalline pyrolytic carbon are filled on the surface and inside of the material to form a good conductive network with the conductive agent in the battery slurry, effectively reducing the internal resistance and improving the rate performance of the material. The raw materials of the present invention are inexpensive, the preparation process is simple, and it is easy to mass-produce. Description of the Drawings

[0023] Figure 1 The first charge and discharge curve of the coin-type half-cell prepared in Example 1;

[0024] Figure 2 The pore size distribution diagram of the negative electrode material prepared in Example 1. Detailed Embodiments

[0025] The following combines the attached Figure 1-2 drawings and specific examples to introduce the present invention in detail. Detailed Embodiment One

[0027] A high-capacity sodium-ion battery hard carbon negative electrode material includes a granular porous hard carbon material, carbon nanotubes, and pyrolytic carbon of an organic matter. The carbon nanotubes are interspersed between the granular porous hard carbon material and the pyrolytic carbon of the organic matter to form a good conductive network; the pyrolytic carbon of the organic matter is embedded or attached inside or on the surface of the granular porous hard carbon material to form a stable porous structure. The granular porous hard carbon material has a short-range ordered and long-range disordered microstructural feature; the average pore diameter of the granular porous hard carbon material is 1-150 nm, and the volume ratio of micropores, mesopores, and macropores is 1:(50-100):(5-50), and can be adjusted according to the high-temperature carbonization process.

[0028] Furthermore, the BET specific surface area of the granular porous hard carbon material is 1 to 200 m 2 / g.

[0029] Furthermore, the granular porous hard carbon material has a layered structure with a layer spacing d 002 The value is 0.345~0.385nm, where d 002 Refers to the 002 crystal plane peak of carbon material. Specific implementation method 2

[0031] A method for preparing a high-capacity sodium ion battery hard carbon negative electrode material according to a specific embodiment 1 is characterized by comprising the following steps:

[0032] Step 1: Processing the plant material through a high-temperature carbonization process under an inert atmosphere to obtain a granular porous hard carbon material;

[0033] Step 2: fully and evenly mix the granular porous hard carbon material with a pyrolytic carbon organic precursor and highly conductive carbon nanotubes, and then pyrolyze them at high temperature under an inert atmosphere to obtain a primary pyrolysis material, wherein the pyrolytic carbon organic precursor accounts for 1%-20% of the granular porous hard carbon material, and the carbon nanotubes account for 0.1%-10% of the granular porous hard carbon material;

[0034] Step 3: After the primary pyrolysis material is crushed, it is mixed evenly with the pyrolysis carbon organic matter precursor and the carbon nanotubes again, and pyrolyzed at high temperature under an inert atmosphere to obtain a secondary pyrolysis material, wherein the pyrolysis carbon organic matter precursor accounts for 1%-20% of the primary pyrolysis material, and the carbon nanotubes account for 0.1%-10% of the primary pyrolysis material;

[0035] Step 4: calcine the secondary pyrolysis material at high temperature in an inert atmosphere, and obtain a high-capacity sodium ion battery hard carbon negative electrode material after screening.

[0036] Furthermore, in step one, the plant material includes one of corn stalks, corn cobs, grapefruit peels, rice husks, walnut shells, cotton, chestnut shells, coconut shells, peanut shells, apricot shells, peach shells, and sugarcane bagasse.

[0037] Furthermore, the carbonization equipment for high-temperature carbonization in step one, the pyrolysis equipment for high-temperature pyrolysis in steps two and three, and the roasting equipment for high-temperature roasting in step four all include one of a tubular furnace, a box furnace, a push plate furnace, a VCJ heating mixer, a tunnel furnace, and a roller furnace.

[0038] Furthermore, the inert atmosphere in steps 1 to 4 includes one or more combinations of N2, Ar2, H2, and O2. In the present invention, the inert atmosphere is relative to the hard carbon negative electrode material, and the atmosphere that does not react with the hard carbon negative electrode material is defined as an inert atmosphere.

[0039] Further, in Step 1, the specific steps of the high-temperature carbonization process are as follows: The plant-based materials are carbonized at a high temperature of 500-2200°C for 1-10 h under an inert atmosphere. When the temperature is cooled to 100-350°C, a nitrogen-oxygen mixed gas with a ratio of (5-10):1 is introduced, and the temperature is kept for 1-5 h to obtain granular porous hard carbon materials. The purpose of introducing the nitrogen-oxygen mixed gas with a ratio of (5-10):1 and keeping the temperature for 1-5 h when the temperature is cooled to 100-350°C is to adjust the ratio of various types of pores.

[0040] Further, in Steps 2 and 3, the pyrolytic carbon organic precursor includes resin materials or asphalt materials. The resin materials include one of epoxy resin, acrylic resin, polyester resin, phenolic resin, and amino resin; the asphalt materials include petroleum asphalt or coal asphalt. The softening point of the asphalt materials is 80-280°C; the particle size of the resin materials or asphalt materials is 1-500 nm;

[0041] Further, in Steps 2 and 3, the high-temperature pyrolysis temperature is 200-2000°C, and the time is 1-10 h for both.

[0042] Further, in Step 3, the crushing equipment used to crush the primary pyrolysis material includes one or a combination of a jaw crusher, a hammer crusher, a toothed disc crusher, a pair-roll crusher, and a jet mill.

[0043] Further, in Step 4, the high-temperature roasting temperature is 1000-3000°C, and the time is 1-10 h.

[0044] In the preparation method of the high-capacity sodium-ion battery hard carbon negative electrode material described in the present invention, after the granular porous hard carbon material undergoes the first mixed high-temperature pyrolysis, the primary pyrolysis material needs to be crushed, classified, and then subjected to secondary mixed pyrolysis. The purpose is to improve the surface defects of the porous structure and form a more uniform and dense high-conductivity structure, thereby improving the first-cycle efficiency of the material. The secondary pyrolysis material also needs to be roasted at a high temperature for a period of time under an inert atmosphere to make the carbon nanotubes and the organic pyrolytic carbon form a partially parallel graphite structure, improving the rate performance of the material.

[0045] Example 1

[0046] A preparation method of a high-capacity sodium-ion battery hard carbon negative electrode material includes the following preparation steps:

[0047] Step 1: The apricot shells are carbonized at a high temperature of 500°C for 4 h in an N2 atmosphere box furnace, cooled to 300°C, a nitrogen-oxygen mixed gas with a ratio of 5:1 is introduced, the temperature is kept for 1 h, and then cooled naturally to obtain porous hard carbon materials;

[0048] Step 2: Thoroughly mix the above-mentioned porous hard carbon material with coal tar pitch with a softening point of 250°C and carbon nanotubes until evenly distributed, press into blocks, and then carbonize at a high temperature of 600°C for 2 h in a box furnace under N2 atmosphere and naturally cool to obtain a primary pyrolysis material; among them, the coal tar pitch accounts for 10% of the porous hard carbon material, and the carbon nanotubes account for 2% of the porous hard carbon material.

[0049] Step 3: After crushing the above primary pyrolysis material by a toothed disk crusher and an air flow pulverizer, mix it again with coal tar pitch with a softening point of 250°C and carbon nanotubes until evenly distributed, where the coal tar pitch accounts for 10% of the primary pyrolysis material, and the carbon nanotubes account for 2% of the primary pyrolysis material; then carbonize at a high temperature of 600°C for 2 h in a VCJ heating mixer filled with N2 and naturally cool to obtain a secondary pyrolysis material.

[0050] Step 4: Roast the above secondary pyrolysis material at a high temperature of 1300°C for 2 h in a box furnace under N2 atmosphere, naturally cool, and then sieve to obtain the hard carbon negative electrode material for the high-capacity sodium-ion battery.

[0051] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a hard carbon negative electrode material for a high-capacity sodium ion battery, characterized in that: The high-capacity sodium-ion battery hard carbon anode material includes granular porous hard carbon material, carbon nanotubes, and pyrolytic carbon of organic matter. The carbon nanotubes are interspersed between the granular porous hard carbon material and the pyrolytic carbon of organic matter, and the pyrolytic carbon of organic matter is embedded inside the granular porous hard carbon material or attached to the surface of the granular porous hard carbon material; The preparation method of the high-capacity sodium-ion battery hard carbon anode material includes the following steps: Step 1: Carbonize plant materials at a high temperature of 500-2200°C for 1-10 h in an inert atmosphere. When the temperature is lowered to 100-350°C, introduce a nitrogen-oxygen mixed gas with a ratio of (5-10):1 and keep it warm for 1-5 h to obtain granular porous hard carbon material; Step 2: Mix the granular porous hard carbon material, pyrolytic carbon organic matter precursor, and carbon nanotubes evenly, and then pyrolyze them at a high temperature in an inert atmosphere to obtain a primary pyrolysis product; Step 3: After crushing the primary pyrolysis product, mix it evenly with the pyrolytic carbon organic matter precursor and carbon nanotubes again, and pyrolyze them at a high temperature in an inert atmosphere to obtain a secondary pyrolysis product; Step 4: Roast the secondary pyrolysis product at a high temperature in an inert atmosphere, and obtain the high-capacity sodium-ion battery hard carbon anode material after sieving; In Step 2 and Step 3, the high-temperature pyrolysis temperature is 200-2000°C, and the time is 1-10 h; in Step 4, the high-temperature roasting temperature is 1000-3000°C, and the time is 1-10 h; In Step 2, the pyrolytic carbon organic matter precursor accounts for 1%-20% of the granular porous hard carbon material, and the carbon nanotubes account for 0.1%-10% of the granular porous hard carbon material; in Step 3, the pyrolytic carbon organic matter precursor accounts for 1%-20% of the primary pyrolysis product, and the carbon nanotubes account for 0.1%-10% of the primary pyrolysis product.

2. The preparation method of the hard carbon negative electrode material for the high-capacity sodium ion battery according to claim 1, characterized in that: The granular porous hard carbon material has a microscopic structural feature of short-range order and long-range disorder. The average pore diameter of the granular porous hard carbon material is 1-150 nm, and the volume ratio of micropores, mesopores, and macropores is 1:(50-100):(5-50).

3. The preparation method of the hard carbon negative electrode material for the high-capacity sodium ion battery according to claim 1, characterized in that: The BET specific surface area of the granular porous hard carbon material is 1 to 200 m 2 / g.

4. The preparation method of the hard carbon negative electrode material for the high-capacity sodium ion battery according to claim 1, characterized in that: The granular porous hard carbon material has a layered structure, and the interlayer spacing value is 0.345 to 0.385 nm.

5. The preparation method of the hard carbon negative electrode material for a high-capacity sodium ion battery according to claim 1, characterized in that: In Step 1, the plant materials include one of corn stalks, corn cobs, pomelo peels, rice husks, walnut shells, cotton, chestnut shells, coconut shells, peanut shells, apricot shells, peach shells, and bagasse.

6. The preparation method of the hard carbon anode material for the high-capacity sodium-ion battery according to claim 1, wherein: In Step 2 and Step 3, the pyrolytic carbon organic matter precursor includes resin materials or asphalt materials. The resin materials include one of epoxy resin, acrylic resin, polyester resin, phenolic resin, and amino resin; the asphalt materials include petroleum asphalt or coal asphalt.

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