A wood-based hard carbon anode material, its preparation method, and its application in sodium-ion batteries.

Abstract

This invention belongs to the field of battery manufacturing technology, specifically relating to a wood-based hard carbon anode material, its preparation method, and its application in sodium-ion batteries. Addressing the high cost of hard carbon material precursors, this invention proposes a method for preparing a wood-based hard carbon anode material, comprising: using natural wood particles as a carbon source precursor, first subjecting them to hydrothermal treatment in a strong acid solution containing hydrogen peroxide, followed by high-temperature carbonization to obtain the wood-based hard carbon anode material. This invention uses natural wood as a raw material, eliminating the need for pore-blocking agents, and thus forming a wood-based hard carbon anode material with a closed-cell structure, providing a better environment for sodium ion insertion and extraction.

Description

Technical Field

[0001] This invention belongs to the field of battery manufacturing technology, specifically relating to a wood-based hard carbon anode material, its preparation method, and its application in sodium-ion batteries. Background Technology

[0002] With the rapid expansion of renewable energy generation from solar and wind power, rechargeable batteries are attracting increasing attention. Lithium-ion batteries, with their high specific capacity and good cycle stability, are considered the most promising and growth-oriented rechargeable batteries. my country is rich in sodium resources, and sodium-ion batteries are considered the most suitable new type of battery for large-scale energy storage, potentially alleviating the limitations on energy storage development caused by lithium resource shortages and uneven distribution.

[0003] Hard carbon refers to non-graphitized carbon, a pyrolytic carbon derived from polymers, possessing advantages such as high specific capacity, good cycle performance, and good cycle stability at high rates. It belongs to the category of non-graphitized amorphous carbon materials, formed by the disordered arrangement of graphite microcrystals. Unlike graphite materials, hard carbon has a large interlayer spacing and numerous micropores, correspondingly providing more sodium ion insertion / extraction sites for sodium storage, resulting in a higher specific capacity. Compared to other materials, hard carbon is more suitable for low-temperature operation and also exhibits good high-rate charge / discharge performance and long cycle life. However, the atomic radius of sodium ions is more than 35% larger than that of lithium ions. The mainstream graphite anode in lithium-ion batteries, due to its smaller pore size and interlayer spacing, cannot meet the requirements of sodium-ion battery anodes. Therefore, hard carbon anodes are the mainstream choice for sodium batteries. Hard carbon precursors are abundant, commonly including biomass, resins, and polymer precursors. Hard carbon materials obtained from different precursors exhibit significant performance differences, and the performance and cost structure also vary significantly depending on the source of the raw materials. Biomass precursors have moderate performance and a wide range of raw materials, such as coconut shells, walnut shells, fruit shells, grapefruit peels, and animal and plant tissues. They are relatively inexpensive and have become the preferred choice for preparing hard carbon materials. Summary of the Invention

[0004] To address the issue of high precursor costs for hard carbon materials, this invention proposes a wood-based hard carbon anode material, its preparation method, and its application in sodium-ion batteries, demonstrating feasibility for large-scale production.

[0005] In a first aspect, the present invention provides a method for preparing a wood-based hard carbon anode material, comprising: using natural wood particles as a carbon source precursor, first placing them in a strong acid solution containing hydrogen peroxide for hydrothermal treatment, and then carbonizing them at high temperature to obtain the wood-based hard carbon anode material.

[0006] In this invention, natural wood (granular) is used as the carbon source precursor. Hydrogen peroxide solution is used for hydrothermal treatment under strong acid conditions. During this hydrothermal treatment, lignin, metallic impurities, and oxidation are removed from the natural wood. Then, high-temperature carbonization is performed to finally prepare a hard carbon anode material. When the carbonization product is used as an anode material for sodium-ion batteries, it exhibits ultra-high capacity and initial coulombic efficiency.

[0007] Preferably, the natural wood particles are made of at least one of bamboo, elm, willow, boxwood, catalpa, paulownia, oak, birch, camphor, nanmu, ginkgo, pine, cypress, cedar, teak, and sandalwood; the particle size of the natural wood particles is at least 1 cm, preferably 3-6 cm, and more preferably 5 cm.

[0008] The method for preparing the natural wood particles includes: drying and pulverizing natural wood to obtain natural wood particles; preferably, the drying temperature is 80-150℃ and the time is 1-24 hours. For example, after drying at 150℃, the wood is then pulverized to the centimeter level.

[0009] Preferably, the concentration of hydrogen peroxide solution in the strong acid solution containing hydrogen peroxide is 0.01–0.9 mol / L;

[0010] The concentration of acid in the strong acid solution containing hydrogen peroxide is 0.1–6 mol / L;

[0011] The strong acid includes at least one of the following: hydrochloric acid, nitric acid, sulfuric acid, hydroiodic acid, hydrobromic acid, and perchloric acid;

[0012] Preferably, the molar ratio of hydrogen peroxide to acid is 3:(5-50).

[0013] Preferably, the ratio of the natural wood to the strong acid solution containing hydrogen peroxide is (100-500) g : (100-200) mL.

[0014] Preferably, the hydrothermal treatment temperature is 150–250°C, and the hydrothermal time is 6–24 hours.

[0015] Preferably, the high-temperature carbonization temperature is 1350–1550°C; the high-temperature carbonization time is 1–12 hours; and the high-temperature carbonization atmosphere contains at least one of Ar, He, N2, NH3, H2, and CO2.

[0016] Preferably, the heating rate of the high-temperature carbonization is 1 to 20°C / minute.

[0017] Secondly, the present invention provides a wood-based hard carbon anode material prepared according to the above preparation method, wherein the specific surface area of ​​the wood-based hard carbon anode material is <10m². 2 / g.

[0018] Thirdly, the present invention provides an application of a wood-based hard carbon anode material in sodium-ion batteries.

[0019] Fourthly, the present invention provides a sodium-ion battery, characterized in that: the negative electrode comprises a wood-based hard carbon negative electrode material.

[0020] The above-described method provides a wood-based hard carbon anode material, its preparation method, and a sodium-ion battery. This synthesis method yields an optimized anode material. Its beneficial effects are as follows:

[0021] 1. The natural wood used in this invention is widely available and inexpensive;

[0022] 2. In this invention, natural wood is treated with hydrogen peroxide solution and under strong acid conditions to remove impurities such as lignin and metals and reduce its ash content. It also oxidizes the cellulose and hemicellulose in the natural wood, thereby increasing the yield of natural wood-based carbonization and significantly reducing the cost of hard carbon.

[0023] 3. The hard carbon synthesis process of this invention is simple and easy to implement in large quantities, and has industrialization prospects;

[0024] 4. The hard carbon anode material prepared by this invention has a performance of 30 mA g. -1 At current density, the capacity is 340 mAh g. -1 The above shows that the coulomb efficiency is greater than 92%.

[0025] 5. This invention uses natural wood as raw material, eliminating the need for pore-blocking agents to form a wood-based hard carbon anode material with a closed-cell structure, providing a better environment for sodium ion insertion and extraction. Specifically, natural wood contains a large amount of lignin, whose disordered structure results in a low sp2 carbon content in the final hard carbon during the carbonization process. After removing the lignin, the cellulose and hemicellulose in the centimeter-sized natural wood particles are exposed, mainly composed of C, H, and O elements. These elements are converted into water through high-temperature hydrothermal oxidation with hydrogen peroxide, which not only helps increase the carbon content but also contributes to the formation of numerous closed pores. The strong acid used is to remove metallic impurities from the wood (weak acids cannot remove them completely). The strong acid solution of hydrogen peroxide can remove lignin while simultaneously oxidizing cellulose and hemicellulose, significantly increasing the residual carbon content (by approximately 100%). The number of closed pores is related to the carbonization temperature; the higher the temperature, the smaller the specific surface area, and the more closed pores. Attached Figure Description

[0026] Figure 1 The image shows the XRD pattern of the hard carbon anode material obtained in Example 1. Detailed Implementation

[0027] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0028] In this disclosure, natural wood is mainly used as a carbon source precursor. A hydrogen peroxide solution is used to remove impurities and oxidize the natural wood under strong acid conditions, followed by high-temperature carbonization. No pore-blocking agent is needed to prepare hard carbon anode materials.

[0029] In optional embodiments, the natural wood includes any one of bamboo, elm, willow, boxwood, catalpa, paulownia, oak, birch, camphor, nanmu, ginkgo, pine, cypress, cedar, teak, and sandalwood. The natural wood is dried and pulverized to obtain natural wood particles. The particle size of the natural wood particles is at least 1 cm, preferably 3–10 cm, and more preferably 5 cm. Preferably, the drying temperature is 80–150°C, and the drying time is 1–24 hours.

[0030] In an optional embodiment, the concentration of the hydrogen peroxide aqueous solution is 0.01–0.9 mol / L.

[0031] In an optional embodiment, the concentration of the strong acid solution is 0.1–6 mol / L.

[0032] In an optional embodiment, the hydrothermal temperature is 120–250°C, and the hydrothermal time is 6–24 hours.

[0033] In an optional embodiment, the high-temperature carbonization temperature is 1350–1550°C. Preferably, the heating rate is 1–20°C / min. The carbonization atmosphere is any one or more of the protective gas Ar, He, N2, NH3, H2, and CO2. It should be noted that the high-temperature carbonization temperature should not be too high; around 1400°C (1350–1550°C) is more suitable. Too high a temperature reduces the interlayer spacing, which also affects capacity. If the high-temperature carbonization temperature is too low, the hard carbon will contain a large amount of H and O elements, reducing the initial efficiency.

[0034] In this invention, a fully automated specific surface area measuring instrument was used to test the specific surface area of ​​the hard carbon anode material, which was found to be <10 m². 2 / g.

[0035] In this invention, the carbonization efficiency of the hard carbon anode material was measured to be 10-40% using thermogravimetric analysis. The carbonization efficiency is related to the degree of oxidation; the more thorough the oxidation, the higher the carbonization yield.

[0036] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are all within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below. In the following examples and comparative examples, unless otherwise specified, the natural wood particles used are all 5cm.

[0037] Example 1

[0038] 500g of dried bamboo was placed in a strong acid solution (0.5mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 180℃ for 12 hours. After washing, the material was dried at 100℃. The treated material was then placed in a tube furnace under a N2 atmosphere and heated to 1400℃ at a rate of 2.5℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0039] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 342.4 mAh g. -1 The initial efficacy rate was 92.1%. For example... Figure 1 The XRD pattern of the synthesized hard carbon anode material shows typical hard carbon characteristics.

[0040] Example 2

[0041] 500g of dried bamboo was placed in a strong acid solution (1mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 180℃ for 12 hours. After washing, it was dried at 100℃. The treated material was then placed in a tube furnace under a N2 atmosphere and heated to 1400℃ at a rate of 2.5℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0042] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 343.1 mAh g. -1 The initial efficacy rate was 92.4%.

[0043] Example 3

[0044] 500g of dried bamboo was placed in a strong acid solution (3mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 180℃ for 12 hours. After washing, the material was dried at 100℃. The treated material was then placed in a tube furnace under a N2 atmosphere and heated to 1400℃ at a rate of 2.5℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0045] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 343.8 mAh g. -1 The initial efficacy rate was 92.5%.

[0046] Example 4

[0047] 500g of dried bamboo was placed in a strong acid solution (5mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 180℃ for 12 hours. After washing, it was dried at 100℃. The treated material was then placed in a tube furnace under a N2 atmosphere and heated to 1400℃ at a rate of 2.5℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0048] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 346.2 mAh g. -1 The initial efficacy rate was 92.5%.

[0049] Example 5

[0050] 500g of dried bamboo was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.6mol / L) and hydrothermally heated at 180℃ for 12 hours. After washing, the material was dried at 100℃. The treated material was then placed in a tube furnace under a nitrogen atmosphere and heated to 1400℃ at a rate of 2.5℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0051] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg.-1 The initial discharge specific capacity at the current density is 340.9 mAh g. -1 The initial efficacy rate was 92.4%.

[0052] Example 6

[0053] 500g of dried willow wood was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 160℃ for 15 hours. After washing, the wood was dried at 100℃. The treated material was then placed in a tube furnace under a N2 atmosphere and heated to 1400℃ at a rate of 1.5℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0054] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 342.4 mAh g. -1 The initial efficacy rate was 92.3%.

[0055] Example 7

[0056] 500g of dried oak was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 180℃ for 12 hours. After washing, it was dried at 100℃. The treated material was then placed in a tube furnace under a N2 atmosphere and heated to 1500℃ at a rate of 2.5℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0057] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 342.7 mAh g. -1 The initial efficacy rate was 92.2%.

[0058] Example 8

[0059] 500g of dried birch wood was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 180℃ for 15 hours. After washing, the wood was dried at 100℃. The treated material was then placed in a tube furnace under an Ar atmosphere and heated to 1450℃ at a rate of 1.5℃ per minute, and held at that temperature for 6 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0060] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 340.6 mAh g. -1 The initial efficacy rate was 92.0%.

[0061] Example 9

[0062] 500g of dried paulownia wood was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 200℃ for 15 hours. After washing, the wood was dried at 100℃. The treated material was then placed in a tube furnace under an Ar atmosphere and heated to 1400℃ at a rate of 5℃ per minute, holding for 3 hours. After cooling to room temperature, hard carbon anode material was obtained.

[0063] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 341.3 mAh g. -1 The initial efficacy rate was 92.2%.

[0064] Example 10

[0065] 500g of dried Phoebe zhennan wood was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 200℃ for 15 hours. After washing, it was dried at 100℃. The treated material was then placed in a tube furnace under an Ar atmosphere and heated to 1400℃ at a rate of 2℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0066] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 345.2 mAh g. -1 The initial efficacy rate was 92.1%.

[0067] Example 11

[0068] 500g of dried pine wood was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 200℃ for 15 hours. After washing, the wood was dried at 100℃. The treated material was then placed in a tube furnace under an Ar atmosphere and heated to 1400℃ at a rate of 2℃ per minute, and held for 3 hours. After cooling to room temperature, hard carbon anode material was obtained.

[0069] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 344.8 mAh g. -1 The initial efficacy rate was 92.3%.

[0070] Example 12

[0071] 500g of dried cypress wood was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 200℃ for 15 hours. After washing, the wood was dried at 100℃. The treated material was then placed in a tube furnace under an Ar atmosphere and heated to 1400℃ at a rate of 2℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0072] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 343.9 mAh g. -1 The initial efficacy rate was 92.4%.

[0073] Example 13

[0074] 500g of dried bamboo was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.6mol / L) and hydrothermally heated at 150℃ for 12 hours. After washing, it was dried at 100℃. The treated material was then placed in a tube furnace under a N2 atmosphere and heated to 1400℃ at a rate of 2.5℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0075] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 343.6 mAh g.-1 The initial efficacy rate was 92.3%.

[0076] Example 14

[0077] 500g of dried bamboo was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 150℃ for 18 hours. After washing, it was dried at 100℃. The treated material was then placed in a tube furnace under a N2 atmosphere and heated to 1400℃ at a rate of 2.5℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0078] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 344.3 mAh g. -1 The initial efficacy rate was 92.4%.

[0079] Example 15

[0080] 500g of dried bamboo was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 180℃ for 18 hours. After washing, it was dried at 100℃. The treated material was then placed in a tube furnace under a N2 atmosphere and heated to 1400℃ at a rate of 2.5℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0081] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 345.6 mAh g. -1 The initial efficacy rate was 92.5%.

[0082] Example 16

[0083] 500g of dried bamboo was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 200℃ for 12 hours. After washing, it was dried at 100℃. The treated material was then placed in a tube furnace under a N2 atmosphere and heated to 1400℃ at a rate of 2.5℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0084] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 346.6 mAh g. -1 The initial efficacy rate was 92.5%.

[0085] Example 17

[0086] 500g of dried bamboo was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 200℃ for 18 hours. After washing, it was dried at 100℃. The treated material was then placed in a tube furnace under a N2 atmosphere and heated to 1400℃ at a rate of 2.5℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0087] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 348.3 mAh g. -1 The initial efficacy rate was 92.7%.

[0088] Example 18

[0089] 500g of dried bamboo was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 240℃ for 12 hours. After washing, it was dried at 100℃. The treated material was then placed in a tube furnace under a N2 atmosphere and heated to 1400℃ at a rate of 2.5℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0090] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 345.6 mAh g. -1 The initial efficacy rate was 92.5%.

[0091] Example 19

[0092] 500g of dried bamboo was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 200℃ for 18 hours. After washing, it was dried at 100℃. The treated material was then placed in a tube furnace under an Ar atmosphere and heated to 1400℃ at a rate of 1.5℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0093] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 345.6 mAh g. -1 The initial efficacy rate was 92.4%.

[0094] Example 20

[0095] 500g of dried bamboo was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 200℃ for 18 hours. After washing, it was dried at 100℃. The treated material was then placed in a tube furnace under an Ar atmosphere and heated to 1450℃ at a rate of 2℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0096] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 345.0 mAh g. -1 The initial efficacy rate was 92.2%.

[0097] Example 21

[0098] 500g of dried bamboo was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 200℃ for 18 hours. After washing, the material was dried at 100℃. The treated material was then placed in a tube furnace under an Ar atmosphere and heated to 1350℃ at a rate of 2℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0099] The sodium-ion battery uses hard carbon anode material as the anode material, sodium metal sheet as the cathode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) electrolyte, and Celgard 2400 separator for electrochemical testing.

[0100] Example 22

[0101] 500g of dried bamboo was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 200℃ for 18 hours. After washing, the material was dried at 100℃. The treated material was then placed in a tube furnace under an Ar atmosphere and heated to 1550℃ at a rate of 2℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0102] The sodium-ion battery uses hard carbon anode material as the anode material, sodium metal sheet as the cathode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) electrolyte, and Celgard 2400 separator for electrochemical testing.

[0103] Comparative Example 1

[0104] 500g of dried bamboo was placed in a tube furnace under an Ar atmosphere, and the temperature was increased to 1450℃ at a rate of 2℃ per minute and held for 3 hours. After cooling to room temperature, hard carbon anode material was obtained.

[0105] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 302.3 mAh g. -1 The initial efficacy rate was 87.6%.

[0106] Comparative Example 2

[0107] 500g of dried bamboo was placed in a strong acid solution (2mol / L) and hydrothermally heated at 200℃ for 18 hours, then washed and dried at 100℃. The treated material was then placed in a tube furnace under an Ar atmosphere, heated to 1450℃ at a rate of 2℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, hard carbon anode material was obtained.

[0108] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 312.6 mAh g. -1 The initial efficacy rate was 88.3%.

[0109] Comparative Example 3

[0110] 500g of dried bamboo was placed in a 0.3mol / L hydrogen peroxide solution and hydrothermally heated at 200℃ for 18 hours, then washed and dried at 100℃. The treated material was then placed in a tube furnace under an Ar atmosphere and heated to 1450℃ at a rate of 2℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, hard carbon anode material was obtained.

[0111] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on this hard carbon anode material at 30 mAg. -1 The initial discharge specific capacity at the current density is 316.4 mAh g. -1 The initial efficacy rate was 88.5%.

[0112] Comparative Example 4

[0113] 500g of dried bamboo was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 200℃ for 18 hours. After washing, it was dried at 100℃. The treated material was then placed in a tube furnace under an Ar atmosphere and heated to 1300℃ at a rate of 2℃ per minute, and held for 3 hours. After cooling to room temperature, hard carbon anode material was obtained.

[0114] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on the hard carbon anode material. The initial discharge specific capacity of this material at a current density of 30 mA g⁻¹ was 314.7 mAh g⁻¹. -1 The initial efficacy rate was 87.5%.

[0115] Comparative Example 5

[0116] 500g of dried bamboo was placed in a strong acid solution (2mol / L) of 200mL hydrogen peroxide (0.3mol / L) and hydrothermally heated at 200℃ for 18 hours. After washing, the material was dried at 100℃. The treated material was then placed in a tube furnace under an Ar atmosphere and heated to 1600℃ at a rate of 2℃ per minute, and held at that temperature for 3 hours. After cooling to room temperature, the hard carbon anode material was obtained.

[0117] A sodium-ion battery was tested using hard carbon anode material as the negative electrode, sodium metal sheet as the positive electrode, 1M NaFP6 dissolved in DMC:EC:EMC (1:1:1) as the electrolyte, and Celgard 2400 as the separator. Electrochemical tests were performed on the hard carbon anode material. The initial discharge specific capacity of this material at a current density of 30 mA g⁻¹ was 315.2 mAh g⁻¹. -1 The initial efficacy rate was 88.9%.

[0118] Table 1:

[0119]

[0120]

[0121] Table 2:

[0122]

[0123]

[0124] The above description describes specific embodiments formed by combining some of the features and methods provided in this invention. It should be noted that for those skilled in the art, several implementation methods can be formed without departing from the principle of this invention, and these implementation methods based on this invention should also be considered within the scope of protection of this invention.

Claims

1. A method for preparing a wood-based hard carbon anode material, characterized in that, The specific surface area of ​​the wood-based hard carbon anode material is <10 m². 2 / g and has a closed-cell structure; the preparation method includes: using natural wood particles as a carbon source precursor, first placing them in a strong acid solution containing hydrogen peroxide for hydrothermal treatment, and then carbonizing them at high temperature to obtain the wood-based hard carbon anode material. The concentration of hydrogen peroxide in the strong acid solution containing hydrogen peroxide is 0.3–0.6 mol / L; The concentration of acid in the strong acid solution containing hydrogen peroxide is 0.1–6 mol / L; The molar ratio of hydrogen peroxide to acid is 3:(5-50); The ratio of the natural wood to the strong acid solution containing hydrogen peroxide is (100-500) g : (100-200) mL; The high-temperature carbonization temperature is 1350–1550 °C; the high-temperature carbonization time is 1–12 hours.

2. The preparation method according to claim 1, characterized in that, The natural wood particles are made of at least one of the following materials: bamboo, elm, willow, boxwood, catalpa, paulownia, oak, birch, camphor, nanmu, ginkgo, pine, cypress, cedar, teak, and sandalwood; the particle size of the natural wood particles is at least 1 cm. The method for preparing the natural wood particles includes: drying and crushing natural wood to obtain natural wood particles; The drying temperature is 80–150°C, and the time is 1–24 hours.

3. The preparation method according to claim 1 or 2, characterized in that, The strong acid includes at least one of the following: hydrochloric acid, nitric acid, sulfuric acid, hydroiodic acid, hydrobromic acid, and perchloric acid.

4. The preparation method according to claim 1 or 2, characterized in that, The hydrothermal treatment temperature is 150–250°C, and the hydrothermal time is 6–24 hours.

5. The preparation method according to claim 1 or 2, wherein the high-temperature carbonization atmosphere comprises at least one of Ar, He, N2, NH3, H2 and CO2; and the heating rate of the high-temperature carbonization is 1 to 20 °C / min.

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