A high-Fischer-Grain-Size Core-Ring Structure Hard Carbon Material and Its Application

Abstract

The present invention belongs to the technical field of hard carbon negative electrode materials, and relates to a high-Fischer particle size core ring structure hard carbon material and its application. The preparation method thereof comprises the following steps: (1) crushing biomass raw materials to obtain precursor raw materials; (2) mixing the precursor raw materials and an organic solution containing a catalyst to obtain pre-treated powder; (3) heat-treating the pre-treated powder raw materials to obtain a core homogeneous layer, and performing high-temperature treatment to obtain a transition layer on its surface; (4) rapidly nitriding the raw materials wrapped with the transition layer; (5) sintering the raw materials after rapid nitriding at high temperature in an inert atmosphere; (6) introducing carbon source gas and continuing carbonization at high temperature. The obtained material is a core ring structure, the outer surface is a surface layer of a porous mesh hard sphere layer, which plays a supporting and protective role, the middle is a transition layer, which plays a buffering and protective role, and plays a fixing role on the internal core homogeneous area, and the innermost layer is a homogeneous flaky hard carbon structure with a large number of holes for sodium storage.

Description

Technical Field

[0001] The invention belongs to the technical field of hard carbon negative electrode materials and relates to a hard carbon material with a core ring structure and a high Fischer particle size and an application thereof. Background Art

[0002] In recent years, due to the high development of photovoltaic power generation and the widespread popularity of hydropower generation, the demand for energy storage has increased dramatically, and electrochemical energy storage is now recognized as a more effective way of energy storage. Lithium batteries are currently the most popular new energy. They have always been widely used and studied. The invention and preparation of lithium cobalt oxide and ternary lithium batteries have changed the rhythm of people's production and life. However, the growing and already high prices, as well as the large demand for energy storage, make lithium batteries less suitable for the field of energy storage. Therefore, sodium-ion batteries, which work in a similar principle to lithium-ion batteries, have received widespread attention.

[0003] The extremely abundant reserves of sodium have resulted in extremely low costs, a higher overall cost-effectiveness, and broad prospects for sodium-ion batteries. Sodium-ion batteries have not made much progress over the years because their energy density is slightly lower than that of lithium-ion batteries. At the same time, in terms of materials, the research and development of some positive electrode materials has basically met the needs of applications, but negative electrode materials still restrict the practical application of sodium-ion batteries.

[0004] At present, hard carbon materials are considered to be the most promising negative electrode materials for sodium batteries. First, they can show electrochemical properties close to those of graphite negative electrodes for lithium batteries, and their performance is stable. Secondly, the high-temperature treatment has low energy consumption and temperature, the raw materials are abundant and easy to obtain, and the sodium embedding content is high. However, hard carbon has low specific capacity, and the first-round charge and discharge efficiency is lower than that of graphite. Therefore, how to improve the electrochemical performance of hard carbon materials is an urgent problem to be solved. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a high-Fischer-Tropsch core-ring structure hard carbon material and its application.

[0006] The technical solution adopted by the present invention is as follows: A high-Fischer-Grain-Size Core-Ring Structure Hard Carbon Material, the preparation method of which comprises the following steps:

[0007] (1) crushing the biomass raw material using a ball mill to obtain a precursor raw material;

[0008] (2) mixing the precursor raw material and an organic solution containing a catalyst, soaking and uniformly granulating the mixture to obtain a pretreated powder;

[0009] (3) placing the pretreated powder raw material into a muffle furnace for heat treatment to obtain a core homogeneous layer, and then subjecting the homogeneous layer to high temperature treatment to obtain a transition layer on its surface;

[0010] (4) using low-pressure gas to rapidly nitride the raw material covering the transition layer;

[0011] (5) placing the rapidly nitrided raw material into a high-temperature carbonization furnace, heating it at a constant heating rate, and sintering the raw material at high temperature in an inert atmosphere;

[0012] (6) introducing a carbon source gas into the high-temperature carbonization furnace to continue carbonization at high temperature;

[0013] (7) Cooling to room temperature to obtain a hard carbon material with a core-ring structure and high Fischer-Lehr particle size.

[0014] The present invention deposits a catalyst in the raw material and realizes the generation of the core ring by a vapor deposition method. The outer part of the core ring structure is a surface layer of a porous mesh hard sphere layer, which plays a supporting and protective role. The middle part is a transition layer, which plays a buffering and protective role and plays a fixing role for the internal core homogeneous area. The innermost layer is a homogeneous flaky hard carbon structure with a large number of holes for sodium storage.

[0015] In step (1), the biological raw material is any one selected from basswood, rice husk, straw, grapefruit peel, durian peel, spotted bamboo, and oak, or a combination of at least two thereof; the ball mill has a rotation speed of 100-500 r / min, and the ball milling time is 2-10 h.

[0016] The precursor raw material in step (1) is first screened and refined to obtain a biomass precursor fine powder raw material with a particle size in the range of 100 to 800 meshes, which is then used in step (2).

[0017] In step (2), the catalyst is any one of ferric chloride, nickel chloride, cobalt chloride, magnesium chloride or molybdenum chloride, or a combination of at least two thereof;

[0018] The organic solvent used in the organic solution containing the catalyst is any one of N-methylpyrrolidone, carbon tetrachloride, cyclohexane or tetrahydrofuran, or a combination of at least two thereof;

[0019] The mass fraction of the catalyst in the organic solution containing the catalyst is 0.5-5wt%;

[0020] In step (2), the soaking time is 1-8 hours; the mass ratio of the organic solution containing the catalyst to the precursor raw material is (1-5):100.

[0021] If the precursor fine powder raw material is soaked in the salt solution for too short a time, it is difficult for the catalyst to enter the material, which is not conducive to the subsequent growth of carbon nanotubes. However, if the soaking time is too long, the preparation process time is longer.

[0022] In step (3), the heat treatment temperature is 200-400°C, and the heat treatment time is 2-8h; the temperature of the further high temperature treatment is 700-900°C, the treatment time is 20-40min, and the heating rate is 3-5°C / min.

[0023] In step (5), the high temperature sintering temperature is 1000-1200° C., and the high temperature sintering time is 2-10 hours.

[0024] In step (6), the carbon source gas includes any one of methane, ethylene or acetylene or a combination of at least two of them; the carbonization temperature is 600-1000°C, and the carbonization time is 1-6 hours.

[0025] A hard carbon negative electrode material comprises the hard carbon material with a high Fischer-Strauss particle size core ring structure as described above.

[0026] A sodium ion battery, wherein the negative electrode of the sodium ion battery is prepared by using the hard carbon negative electrode material mentioned above.

[0027] By preparing the negative electrode of the sodium ion battery using the high Fischer-Tropsch core-ring structure hard carbon material as described above, the energy density and the first coulombic efficiency of the sodium ion battery can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying creative labor, other drawings obtained based on these drawings still belong to the scope of the present invention.

[0029] Figure 1 This is a schematic structural diagram of the high Fischer-Strauss grain size core ring structure hard carbon material provided by the present invention. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0031] Example 1

[0032] 100 g of straw was washed and dried, and then crushed in a ball mill at 300 r / min to obtain coarse powder. The coarse powder was sieved to obtain a biomass precursor subdivided raw material between 100 and 200 meshes. The precursor subdivided raw material was mixed with a tetrahydrofuran solution with a nickel chloride mass fraction of 1 wt%, and soaked for 1 hour to obtain a further pre-treated granulated fine powder raw material. The pre-treated fine powder raw material was placed in a muffle furnace at 300 oC for 2h. The heat-treated raw material is heated at 800℃ for 30min, and then subjected to rapid low-pressure nitriding. The low-pressure nitrided raw material is placed in a high-temperature carbonization furnace at 3 o The heating rate was increased to 1000 C / min. o C, sinter the raw materials at high temperature in an inert atmosphere for 3 hours. o C is fired for 1 hour and cooled to room temperature to obtain a carbon material with irregular block morphology, which is the above-mentioned high Fischer-Tropsch core-ring structure hard carbon material.

[0033] The hard carbon negative electrode material is assembled into a button battery, and the mass ratio of the raw material hard carbon negative electrode material to CMC (sodium carboxymethyl cellulose) and Ketjen black of the button battery is 8:1:1. The electrochemical performance of the button battery is tested.

[0034] Example 2

[0035] The precursor infiltration solvent of Example 1 was changed to N-methylpyrrolidone to prepare the hard carbon material, and the rest of the preparation method and parameters remained the same.

[0036] Example 3

[0037] The catalyst content in Example 2 was reduced to 0.5 wt % to prepare the hard carbon material, and the rest of the preparation method and parameters remained the same.

[0038] Example 4

[0039] The hard carbon material was prepared by replacing the catalyst in Example 1 with a mixed material of ferric chloride:cobalt chloride in a mass ratio of 1:1, and the rest of the preparation method and parameters remained the same.

[0040] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A high-Fischer-Tropsch core-ring structure hard carbon material, characterized in that The preparation method comprises the following steps: (1) crushing the biomass raw material using a ball mill to obtain a precursor raw material; (2) mixing the precursor raw material and an organic solution containing a catalyst, soaking and uniformly granulating the mixture to obtain a pretreated powder; (3) placing the pretreated powder raw material into a muffle furnace for heat treatment to obtain a core homogeneous layer, and then subjecting the homogeneous layer to high temperature treatment to obtain a transition layer on its surface; (4) using low-pressure gas to rapidly nitride the raw material wrapping the transition layer; (5) placing the rapidly nitrided raw material into a high-temperature carbonization furnace, heating it at a constant heating rate, and sintering the raw material at high temperature in an inert atmosphere; (6) introducing a carbon source gas into the high-temperature carbonization furnace to continue carbonization at high temperature; (7) Cooling to room temperature to obtain a hard carbon material with a core-ring structure and high Fischer-Lehr particle size.

2. The high Fischer-Tropsch core-ring structure hard carbon material according to claim 1, characterized in that: In step (1), the biomass raw material is any one or a combination of at least two selected from basswood, rice husk, straw, grapefruit peel, durian peel, spotted bamboo, and oak; the ball mill speed is 100-500 r / min, and the ball milling time is 2-10 h.

3. The high Fischer-Tropsch core-ring structure hard carbon material according to claim 1, characterized in that: The precursor raw material in step (1) is first screened and refined to obtain a biomass precursor fine powder raw material with a particle size in the range of 100 to 800 meshes, which is then used in step (2).

4. The high Fischer-Tropsch core-ring structure hard carbon material according to claim 3, characterized in that: In step (2), the catalyst is any one of ferric chloride, nickel chloride, cobalt chloride, magnesium chloride or molybdenum chloride, or a combination of at least two thereof; The organic solvent used in the organic solution containing the catalyst is any one of N-methylpyrrolidone, carbon tetrachloride, cyclohexane or tetrahydrofuran, or a combination of at least two thereof; The mass fraction of the catalyst in the organic solution containing the catalyst is 0.5-5wt%.

5. The high Fischer-Tropsch core-ring structure hard carbon material according to claim 4, characterized in that: In step (2), the soaking time is 1 to 8 hours; the mass ratio of the organic solution containing the catalyst to the precursor raw material is (1 to 5):

100.

6. The high Fischer-Tropsch core-ring structure hard carbon material according to claim 1, characterized in that: In step (3), the heat treatment temperature is 200-400°C, and the heat treatment time is 2-8h; the temperature of further high temperature treatment is 700-900°C, the treatment time is 20-40min, and the heating rate is 3-5°C / min.

7. The high Fischer-Tropsch core-ring structure hard carbon material according to claim 1, characterized in that: In step (5), the high temperature sintering temperature is 1000-1200° C., and the high temperature sintering time is 2-10 hours.

8. The high Fischer-Tropsch core-ring structure hard carbon material according to claim 1, characterized in that: In step (6), the carbon source gas includes any one of methane, ethylene or acetylene or a combination of at least two of them; the carbonization temperature is 600-1000° C., and the carbonization time is 1 to 6 hours.

9. A hard carbon negative electrode material, characterized in that: The hard carbon negative electrode material comprises a high-Fischer-Strauss core ring structure hard carbon material as claimed in any one of claims 1 to 8.

10. A sodium ion battery, characterized in that: The negative electrode of the sodium ion battery is prepared using the hard carbon negative electrode material as claimed in claim 9.

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