Preparation method of high-performance bagasse hard carbon negative electrode material

Abstract

The invention discloses a preparation method of a high-performance bagasse hard carbon negative electrode material. According to the invention, bagasse is taken as a raw material, constant-temperature pickling treatment is carried out, carbonization conditions are accurately controlled, an oil bath auxiliary activator is adopted to activate the carbon material, carbon layer spacing is specifically enlarged, closed pores are constructed, and the structure and electrochemical performance of the hard carbon material are significantly improved. The solid activating agent is decomposed under the oil bath condition to generate a gas-phase oxidizing agent, hard carbon is mildly and uniformly etched and modified from the interior of particles, pores are created, meanwhile, a graphite microcrystalline structure beneficial to sodium storage is better reserved and optimized, and the first effect, the reversible specific capacity, the cycling stability and the platform capacity ratio of the hard carbon negative electrode material are improved.

Description

Technical Field

[0001] This invention belongs to the technical field of sodium-ion battery anode materials, specifically relating to a method for preparing a high-performance bagasse hard carbon anode material. Background Technology

[0002] Lithium-ion batteries are widely used in portable devices due to their high power density, high energy density, low self-discharge, and low maintenance requirements.

[0003] Energy storage is crucial for electronic devices and electric vehicles. However, lithium resources are limited in their grid-scale applications due to their uneven distribution, limited availability, and high cost. With the rapid development of energy storage systems, there is an urgent need to develop high-performance electrochemical batteries. Sodium, due to its abundant resources, uniform distribution, low cost, and chemical properties similar to lithium, is considered an effective alternative to lithium-ion batteries in some fields. However, the larger radius of sodium ions (0.102 nm) compared to lithium ions (0.076 nm) severely hinders their insertion into anode materials, resulting in unsatisfactory specific capacity and cycle performance of sodium-ion batteries. Therefore, finding suitable anode materials is a key issue in the development of sodium-ion batteries.

[0004] Biomass hard carbon has become a research hotspot for sodium-ion battery anode materials due to its renewability, low cost, and environmental friendliness. Its relatively large interlayer spacing (d...) 002 Its surface area (>0.37 nm) makes it suitable for sodium storage, while its unique microporous-mesoporous structure promotes sodium ion adsorption and migration, providing excellent electrochemical performance. Furthermore, the structural tunability of biomass hard carbon materials further enhances their potential for optimizing sodium storage performance. Existing technologies often employ traditional liquid-phase oxidation activation to increase the specific surface area of ​​biomass hard carbon, which often damages the graphitic microcrystalline structure of the carbon material, leading to a decrease in plateau capacity and reduced first-efficiency. Summary of the Invention

[0005] This invention provides a method for preparing high-performance bagasse hard carbon anode material, by precisely controlling the carbonization conditions, and

[0006] A solid activator that can decompose to generate a gaseous oxidant is used to activate carbonized materials. While creating pores, the graphite microcrystalline structure is preserved, which improves the plateau capacity and first-efficiency of hard carbon anode materials. This solves the problem that the plateau capacity and first-efficiency of hard carbon materials are reduced due to the use of traditional liquid-phase oxidation activation in existing technologies.

[0007] This invention is achieved through the following technical solutions:

[0008] A method for preparing a high-performance bagasse hard carbon anode material includes the following steps:

[0009] 1) Pre-carbonization: Sugarcane bagasse is heated to 400-600℃ under an inert atmosphere and held for 0.5-5 hours to obtain pre-carbonized material;

[0010] 2) Secondary carbonization: The pre-carbonized material is acid-washed, then cleaned until neutral and dried. Under an inert atmosphere, the temperature is programmed to rise to 1200-1600℃ and held for 0.5-4 h to obtain the secondary carbonized material.

[0011] 3) Activation: The secondary carbonized material is physically mixed with a solid activator that can decompose to produce a gaseous oxidant, and then treated in an oil bath at 80-150℃ for 0.5-2 h. After cleaning until neutral and drying, hard carbon anode material is obtained.

[0012] Preferably, in step 1), the programmed heating rate is 1-10℃ / min.

[0013] Preferably, in step 2), the acid used for pickling is an inorganic acid or an organic acid, and the inorganic acid is one or more of sulfuric acid, hydrochloric acid, and nitric acid. Further, the acid concentration is 1-30 wt%.

[0014] Preferably, in step 2), the pickling conditions are: temperature 25-90℃, time 1-8 h.

[0015] Preferably, in step 2), the programmed heating rate is 1-10℃ / min.

[0016] Preferably, in steps 1) and 2), the inert atmosphere is one of nitrogen, argon, and helium.

[0017] Preferably, in step 3), the solid activator that can decompose to generate a gaseous oxidant is one or more of ammonium nitrate, sodium peroxide, and cobalt trifluoride.

[0018] Preferably, in step 3), the mass ratio of the secondary carbonization material to the solid activator that can decompose to generate a gaseous oxidant is 1:(0.5~3).

[0019] This invention also protects the hard carbon anode material prepared by the above preparation method.

[0020] This invention also protects the application of the hard carbon anode material prepared by the above preparation method in the preparation of sodium-ion batteries.

[0021] Beneficial effects:

[0022] 1. This invention uses sugarcane bagasse as raw material and optimizes the pretreatment, carbonization and activation processes. Specifically, it uses constant temperature acid washing and precise control of carbonization conditions (temperature, time and atmosphere), and uses an oil bath assisted activator to activate the carbon material, which specifically expands the carbon layer spacing and constructs closed pores, significantly improving the structure and electrochemical properties of hard carbon materials.

[0023] 2. This invention utilizes a solid activator decomposed under oil bath conditions to generate a gaseous phase (e.g., NO2 and O2), which can gently and uniformly etch and modify hard carbon from within the particles, creating pores. Compared to traditional liquid-phase oxidation activation, which increases the specific surface area of ​​carbon materials but damages the graphite microcrystalline structure, leading to a decrease in plateau capacity and initial efficiency, the hard carbon anode material prepared by the method of this invention better retains and optimizes the graphite microcrystalline structure conducive to sodium storage, exhibiting higher initial efficiency, reversible specific capacity, cycle stability, and plateau capacity ratio, laying a material foundation for the preparation of high-performance sodium-ion batteries.

[0024] 3. The method of this invention provides a new solution for the commercial application of biomass hard carbon materials in the energy storage market, helping to break through the performance bottlenecks of existing domestic hard carbon materials and foreign patent barriers, and forming an independent intellectual property system. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope image of the bagasse hard carbon anode material prepared in Example 1.

[0026] Figure 2 The results are from long-cycle tests of a coin cell assembled with the bagasse hard carbon anode material prepared in Example 1 at a current density of 0.35 A / g. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and examples.

[0028] Example 1

[0029] 1. Preparation of sugarcane bagasse hard carbon anode material

[0030] 1) Pre-carbonization: Weigh a certain amount of bagasse and put it into a tube furnace. Under an argon atmosphere, heat the material to 500℃ at 10℃ / min and hold for 3 hours to obtain pre-carbonized material.

[0031] 2) Secondary carbonization: After cooling, the pre-carbonized material is taken out and acid-washed with 10wt% hydrochloric acid at 90℃ for 2 h. Then it is washed until neutral and dried. It is placed in a tube furnace and heated to 1300℃ at 5℃ / min under argon atmosphere and held for 4 h to obtain secondary carbonized material.

[0032] 3) Activation: After cooling, the secondary carbonization material and ammonium nitrate are physically mixed at a mass ratio of 1:1, heated in an oil bath at 150℃ for 0.5 h, and then washed until neutral and dried to obtain sugarcane bagasse hard carbon anode material.

[0033] 2. Electrochemical testing.

[0034] Electrochemical tests were conducted on the bagasse hard carbon anode material prepared in step 1: the hard carbon electrode sheets were assembled into a half-cell in a glove box and then charged and discharged at a current density of 50 mA / g. The rate performance was tested using a current density of 0.1-10.0 A / g. The initial efficiency of the hard carbon anode material was 92%, the reversible specific capacity was 432 mAh / g, the plateau capacity ratio was 45.5%, and the capacity retention rate was 90% after 10,000 cycles.

[0035] Comparative Example 1

[0036] 1. Preparation of sugarcane bagasse hard carbon anode material

[0037] 1) Pre-carbonization: Weigh a certain amount of bagasse and put it into a tube furnace. Under an argon atmosphere, heat the material to 500℃ at 10℃ / min and hold for 3 hours to obtain pre-carbonized material.

[0038] 2) Secondary carbonization: After cooling, the pre-carbonized material is taken out and acid-washed with 10wt% hydrochloric acid at 90℃ for 2 h. Then it is washed until neutral and dried. It is placed in a tube furnace and heated to 1300℃ at 5℃ / min under argon atmosphere and held for 4 h to obtain secondary carbonized material.

[0039] 3) Activation: After cooling, the secondary carbonization material is physically mixed with concentrated nitric acid at a mass ratio of 1:1, heated in an oil bath at 150℃ for 0.5 h, and then washed until neutral and dried to obtain sugarcane bagasse hard carbon anode material.

[0040] 2. Electrochemical testing.

[0041] Electrochemical tests were conducted on the bagasse hard carbon anode material prepared in step 1: the hard carbon electrode sheets were assembled into a half-cell in a glove box and then charged and discharged at a current density of 50 mA / g. The rate performance was tested using a current density of 0.1-10.0 A / g. The initial efficiency of the hard carbon anode material was 73%, the reversible specific capacity was 282 mAh / g, the plateau capacity ratio was 28.9%, and the capacity retention rate after 10,000 cycles was 50.8%.

[0042] Comparative Example 2

[0043] 1. Preparation of sugarcane bagasse hard carbon anode material

[0044] 1) Pre-carbonization: Weigh a certain amount of bagasse and put it into a tube furnace. Under an argon atmosphere, heat the material to 500℃ at 10℃ / min and hold for 3 hours to obtain pre-carbonized material.

[0045] 2) Secondary carbonization: After cooling, the pre-carbonized material is taken out and acid-washed with 10wt% hydrochloric acid at 90℃ for 2 h. Then it is washed until neutral and dried. It is placed in a tube furnace and heated to 1300℃ at 5℃ / min under argon atmosphere and held for 4 h to obtain secondary carbonized material.

[0046] 3) Activation: After cooling, the secondary carbonized material is physically mixed with hydrogen peroxide solution at a mass ratio of 1:1, heated in an oil bath at 150℃ for 0.5 h, and then washed until neutral and dried to obtain bagasse hard carbon anode material.

[0047] 2. Electrochemical testing.

[0048] Electrochemical tests were conducted on the bagasse hard carbon anode material prepared in step 1. Specifically, the hard carbon electrode sheets were assembled into a half-cell in a glove box and then charged and discharged at a current density of 50 mA / g. Rate performance tests were conducted using current densities ranging from 0.1 to 10.0 A / g. The initial efficiency of the hard carbon anode material was 70%, the reversible specific capacity was 311 mAh / g, the plateau capacity ratio was 33.1%, and the capacity retention rate after 10,000 cycles was 73.2%.

[0049] Example 2:

[0050] The preparation of sugarcane bagasse hard carbon anode material is based on step 1 of Example 1, with the following differences: Step 1) pre-carbonization involves heating sugarcane bagasse to 600℃ at 10℃ / min and holding for 5 h in a nitrogen atmosphere; Step 2) secondary carbonization involves acid washing the pre-carbonized material with 30wt% acetic acid at 60℃ for 8 h, cleaning until neutral, drying, and then heating to 1200℃ at 1℃ / min and holding for 4 h in a nitrogen atmosphere; Step 3) activation involves physically mixing the secondary carbonized material with ammonium nitrate at a mass ratio of 1:2, heating in an oil bath at 100℃ for 2 h, cleaning until neutral, and then drying to obtain the sugarcane bagasse hard carbon anode material.

[0051] Electrochemical tests were conducted on the bagasse hard carbon anode material (same as in Example 1). At a current density of 50 mA / g, the hard carbon anode material exhibited an initial efficiency of 82%, a reversible specific capacity of 400.7 mAh / g, a plateau capacity ratio of 52.3%, and a capacity retention rate of 82.5% after 10,000 cycles.

[0052] Example 3:

[0053] The preparation of sugarcane bagasse hard carbon anode material is based on step 1 of Example 1, with the following differences: Step 1) pre-carbonization involves heating sugarcane bagasse to 600℃ at 10℃ / min and holding for 0.5 h in an argon atmosphere; Step 2) secondary carbonization involves acid washing the pre-carbonized material with 10wt% sulfuric acid at 80℃ for 5 h, cleaning until neutral, drying, and then heating to 1600℃ at 1℃ / min in an argon atmosphere and holding for 0.5 h; Step 3) activation involves physically mixing the secondary carbonized material with cobalt trifluoride at a mass ratio of 1:0.5, heating in an oil bath at 80℃ for 1 h, cleaning until neutral, and then drying to obtain the sugarcane bagasse hard carbon anode material.

[0054] Electrochemical tests were conducted on the bagasse hard carbon anode material (same as in Example 1). At a current density of 50 mA / g, the hard carbon anode material exhibited an initial efficiency of 87%, a reversible specific capacity of 364 mAh / g, a plateau capacity ratio of 58.3%, and a capacity retention rate of 81% after 10,000 cycles.

[0055] Example 4:

[0056] The preparation of sugarcane bagasse hard carbon anode material is based on step 1 of Example 1, with the following differences: Step 1) pre-carbonization involves heating sugarcane bagasse to 400℃ in a helium atmosphere at 1℃ / min and holding for 2 h; Step 2) secondary carbonization involves acid washing the pre-carbonized material with 10wt% nitric acid at 90℃ for 4 h, cleaning until neutral, drying, and then heating to 1400℃ in an argon atmosphere at 10℃ / min and holding for 2 h; Step 3) activation involves physically mixing the secondary carbonized material with cobalt trifluoride at a mass ratio of 1:3, heating in an oil bath at 100℃ for 0.5 h, cleaning until neutral, and then drying to obtain the sugarcane bagasse hard carbon anode material.

[0057] Electrochemical tests were conducted on the bagasse hard carbon anode material (same as in Example 1). At a current density of 50 mA / g, the hard carbon anode material exhibited a first-cycle efficiency of 95%, a reversible specific capacity of 450 mAh / g, a plateau capacity ratio of 50.1%, and a capacity retention rate of 95.7% after 10,000 cycles.

[0058] Example 5:

[0059] The preparation of sugarcane bagasse hard carbon anode material is based on step 1 of Example 1, with the following differences: Step 1) pre-carbonization involves heating sugarcane bagasse to 400℃ in a helium atmosphere at 3℃ / min and holding for 2 hours; Step 2) secondary carbonization involves acid washing the pre-carbonized material with 1wt% hydrochloric acid at 25℃ for 1 hour, cleaning until neutral, drying, and then heating to 1400℃ in a nitrogen atmosphere at 10℃ / min and holding for 2 hours; Step 3) activation involves physically mixing the secondary carbonized material with sodium peroxide at a mass ratio of 1:1.5, heating in an oil bath at 150℃ for 1 hour, cleaning until neutral, and then drying to obtain the sugarcane bagasse hard carbon anode material.

[0060] Electrochemical tests were conducted on the bagasse hard carbon anode material (same as in Example 1). At a current density of 50 mA / g, the hard carbon anode material exhibited an initial efficiency of 88.7%, a reversible specific capacity of 385 mAh / g, a plateau capacity ratio of 55%, and a capacity retention rate of 89.8% after 10,000 cycles.

Claims

1. A method for preparing high-performance bagasse hard carbon negative electrode material, characterized in that, The method comprises the following steps: 1) pre-carbonization: heating the bagasse to 400-600℃ under an inert atmosphere at a programmed rate, and keeping the temperature for 0.5-5 h to obtain a pre-carbonized material; 2) secondary carbonization: acid washing the pre-carbonized material, then cleaning it to neutral and drying, heating the material to 1200-1600℃ under an inert atmosphere at a programmed rate, and keeping the temperature for 0.5-4 h to obtain a secondary carbonized material; 3) activation: physically mixing the secondary carbonized material with a solid activator that can decompose to produce a gaseous oxidizing agent, and treating the mixture in an oil bath at 80-150℃ for 0.5-2 h, then cleaning it to neutral and drying to obtain a hard carbon negative electrode material.

2. The method of claim 1, wherein, In step 2), the acid used for acid washing is an inorganic acid or an organic acid, and the inorganic acid is one or more of sulfuric acid, hydrochloric acid, and nitric acid.

3. The method of claim 2, wherein, The acid concentration is 1-30wt%.

4. The method of claim 1, wherein, In step 2), the acid washing conditions are: temperature 25-90℃, and time 1-8 h.

5. The method of claim 1, wherein, In steps 1) and 2), the programmed heating rate is 1-10℃ / min.

6. The method of claim 1, wherein, In steps 1) and 2), the inert atmosphere is one of nitrogen, argon, and helium.

7. The method of claim 1, wherein, In step 3), the solid activator that can decompose to produce a gaseous oxidizing agent is one or more of ammonium nitrate, sodium peroxide, and cobalt trifluoride.

8. The method of claim 1, wherein, In step 3), the mass ratio of the secondary carbonized material to the solid activator that can decompose to produce a gaseous oxidizing agent is 1: (0.5-3).

9. The hard carbon negative electrode material of bagasse prepared by the method of any one of claims 1-8.

10. The use of the hard carbon negative electrode material of claim 9 in the preparation of a sodium ion battery.

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