Preparation method of sodium-ion battery negative electrode material with high capacity and high first effect

Abstract

The invention provides a preparation method of a sodium-ion battery negative electrode material with both high capacity and high first effect. According to the invention, biomass is used as a precursor of the hard carbon negative electrode material, the precursor is subjected to acid pickling purification, then is subjected to pre-oxidation treatment, and then is subjected to high-temperature secondary carbonization to prepare the hard carbon material with excellent electrochemical performance. The preparation method is simple to operate and low in cost, the obtained biomass derived hard carbon negative electrode material is applied to the sodium-ion battery, high capacity and high first efficiency can be both considered, meanwhile, excellent rate capability is shown, and reference significance is provided for preparation of the high-performance sodium-ion battery.

Description

Technical Field

[0001] The present invention relates to the field of preparation of sodium ion negative electrode materials, and in particular to a method for preparing a negative electrode material for a sodium ion battery with both high capacity and high initial efficiency. Background Art

[0002] As environmental pollution becomes increasingly serious, the development of sustainable clean energy has attracted more and more attention. As a result, energy storage equipment has entered a golden period of development. Sodium-ion batteries have shown great potential in achieving large-scale energy storage due to their advantages such as low cost and abundant sodium resources. However, the graphite anode that has been commercialized in lithium-ion batteries is not suitable for sodium-ion batteries. Therefore, finding high-performance anode materials is crucial to the development of sodium-ion batteries. The microstructure of hard carbon is composed of pores, defects and graphite-like microcrystals. It has the advantages of abundant resources, low cost, low discharge voltage and high capacity. It has the potential for commercial application. However, the development of hard carbon materials still faces many problems, such as unsatisfactory rate performance, high initial efficiency and high capacity cannot be taken into account at the same time. In order to promote the practical application of hard carbon anode materials, it is necessary to further explore the preparation methods to improve electrochemical performance. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing a hard carbon negative electrode material for a sodium ion battery with both high capacity and high initial efficiency, which method has the characteristics of low cost, high efficiency, and simple process. The method can be used to prepare a biomass hard carbon material with high initial coulombic efficiency, high reversible specific capacity, and high rate performance.

[0004] In order to achieve the above technical objectives, the specific technical solutions of the present invention are as follows: (1) The biomass precursor is crushed, washed and dried after acid washing and purification; (2) pre-oxidizing the purified biomass in an oxidizing atmosphere to obtain a pre-treated material; (3) The pretreated material is subjected to high-temperature carbonization treatment in an inert atmosphere to obtain a hard carbon material.

[0005] Furthermore, the biomass in step (1) is one or more of gourd, bamboo, straw, walnut shell, bagasse, corn cob, sawdust, and coconut shell.

[0006] Furthermore, in the pickling treatment of step (1), the acid solution is one or more of nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid, and phosphoric acid (pH = 1-5), the concentration is 1-10 M, the mass proportion of the biomass raw material in the acid solution is 5-20%, and the pickling time is 1-12 h.

[0007] Furthermore, the oxidizing atmosphere in step (2) is oxygen or air, and the heating device used includes but is not limited to a tubular furnace, a rotary kiln, a slide rail furnace, etc.

[0008] Furthermore, the pre-oxidation temperature in step (2) is 100-500°C, the time is 0.5 h-10 h, the heating rate is 1°C / min-10°C / min, and the gas flow rate is 50-300 mL / min.

[0009] Furthermore, the inert atmosphere in step (3) is nitrogen, argon, etc., and the heating device used includes but is not limited to a tubular furnace, a rotary furnace, a slide rail furnace, etc.

[0010] Furthermore, the carbonization temperature in step (3) is 1000-1600°C, the time is 1 h-5 h, and the heating rate is 1°C / min-10°C / min.

[0011] The present invention provides a method for preparing a hard carbon negative electrode material for a sodium ion battery with both high capacity and high initial efficiency. The precursor is pre-oxidized to introduce oxygen-containing functional groups, thereby changing the microstructure of the hard carbon material and providing more reversible sodium storage active sites. The interlayer spacing of the obtained hard carbon material is 0.34-0.43 nm, and the specific surface area is 10-500 m 2 / g, first coulombic efficiency ≥90%, first-cycle reversible specific capacity ≥360 mAh / g.

[0012] Compared with the prior art, the preparation method of the hard carbon negative electrode material of the present invention has the following advantages: the hard carbon negative electrode material of the sodium ion battery described in the present invention has low cost and can effectively adjust the structure of the hard carbon material. The hard carbon material can be used as the negative electrode material of the sodium ion battery to achieve both high capacity and high first coulombic efficiency, and effectively reduce electrochemical polarization and improve the rate performance of the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The Fourier transform infrared spectra of the pretreated materials in Example 2 and Comparative Example 1 are shown; Figure 2 High-resolution transmission electron microscopy images of the sodium ion battery hard carbon negative electrode materials prepared in Example 2 and Comparative Example 1; Figure 3 X-ray diffraction patterns of the hard carbon negative electrode materials for sodium ion batteries prepared in Example 2 and Comparative Example 1; Figure 4 This is a comparison diagram of the first cycle charge and discharge curves of the sodium ion battery hard carbon negative electrode material prepared in Example 2 and Comparative Example 1 at a current density of 20 mA / g; Figure 5 This is a comparison chart of the cycle performance of the sodium ion battery hard carbon negative electrode material prepared in Example 2 and Comparative Example 1 at a current density of 1 A / g; Figure 6The first cycle charge-discharge curve at 0.1 C of the full battery assembled with Prussian blue positive electrode material in Example 2; Figure 7 This is the cyclability curve of the full battery assembled with Prussian blue positive electrode material in Example 2 at 1 C. DETAILED DESCRIPTION

[0014] In order to better understand the present invention, the present invention is described in detail below in conjunction with embodiments and drawings. The embodiments are only used to explain the present invention and do not constitute a limitation of the present invention. Example 1

[0015] A method for preparing a hard carbon negative electrode material for a sodium ion battery having both high capacity and high initial efficiency, the steps are as follows: (1) Using bamboo powder as a precursor, prepare 100 mL of 3 M hydrochloric acid solution, add 10 g of bamboo powder, and stir for 6 hours. Then wash the bamboo powder with distilled water until pH = 7, then filter and dry.

[0016] (2) The material prepared in step (1) was placed in a tubular furnace for pre-oxidation treatment. Air atmosphere was introduced at a gas flow rate of 100-150 mL / min. The temperature was raised to 200°C at a heating rate of 5°C / min, kept at this temperature for 2 hours, and naturally cooled to room temperature. The obtained material was named A-1.

[0017] (3) The material prepared in step (2) was introduced into a nitrogen atmosphere at a gas flow rate of 80-100 mL / min, and the temperature was increased to 1400°C at a heating rate of 5°C / min, and the mixture was kept at this temperature for 3 hours and naturally cooled to room temperature. The obtained material was named HC-1. Example 2

[0018] A method for preparing a hard carbon negative electrode material for a sodium ion battery having both high capacity and high initial efficiency, the steps are as follows: (1) Using bamboo powder as a precursor, prepare 100 mL of 3 M hydrochloric acid solution, add 10 g of bamboo powder, and stir for 6 hours. Then wash the bamboo powder with distilled water until pH = 7, then filter and dry.

[0019] (2) The material prepared in step (1) was placed in a tubular furnace for pre-oxidation treatment. Air atmosphere was introduced at a gas flow rate of 100-150 mL / min. The temperature was raised to 250°C at a heating rate of 5°C / min, kept at that temperature for 2 hours, and naturally cooled to room temperature. The obtained material was named A-2.

[0020] (3) The material prepared in step (2) was introduced into a nitrogen atmosphere at a gas flow rate of 80-100 mL / min, and the temperature was increased to 1400°C at a heating rate of 5°C / min, and the temperature was kept at that for 3 hours, and the material was naturally cooled to room temperature. The obtained material was named HC-2. Example 3

[0021] A method for preparing a hard carbon negative electrode material for a sodium ion battery having both high capacity and high initial efficiency, the steps are as follows: (1) Using bamboo powder as a precursor, prepare 100 mL of 3 M hydrochloric acid solution, add 10 g of bamboo powder, and stir for 6 hours. Then wash the bamboo powder with distilled water until pH = 7, then filter and dry.

[0022] (2) The material prepared in step (1) was placed in a tubular furnace for pre-oxidation treatment. Air atmosphere was introduced at a gas flow rate of 100-150 mL / min. The temperature was raised to 300 °C at a heating rate of 5 °C / min, kept at this temperature for 2 hours, and naturally cooled to room temperature. The obtained material was named A-3.

[0023] (3) The material prepared in step (2) was introduced into a nitrogen atmosphere at a gas flow rate of 80-100 mL / min, and the temperature was increased to 1400°C at a heating rate of 5°C / min, and the mixture was kept at this temperature for 3 hours and naturally cooled to room temperature. The obtained material was named HC-3.

[0024] Comparative Example 1 A method for preparing a hard carbon negative electrode material for a sodium ion battery having both high capacity and high initial efficiency, the steps are as follows: (1) Using bamboo powder as a precursor, prepare 100 mL of 3 M hydrochloric acid solution, add 10 g of bamboo powder, and stir for 6 hours. Then wash the bamboo powder with distilled water until pH = 7, then filter and dry.

[0025] (2) The material prepared in step (1) was placed in a tubular furnace for pre-carbonization treatment. A nitrogen atmosphere was introduced with a gas flow rate of 100-150 mL / min. The temperature was raised to 250 °C at a heating rate of 5 °C / min, and the temperature was kept at that temperature for 2 hours. The material was naturally cooled to room temperature. The obtained material was named N-1.

[0026] (3) The material prepared in step (2) was introduced into a nitrogen atmosphere at a gas flow rate of 80-100 mL / min, and the temperature was increased to 1400°C at a heating rate of 5°C / min, and the temperature was kept at that temperature for 3 hours, and the material was naturally cooled to room temperature. The obtained material was named HC-4.

[0027] Application Example 1 (1) The prepared hard carbon samples HC-2 and HC-4 were ground into fine particles and sieved with a 300-mesh sieve. The active material, conductive agent (super P), and binder (2% sodium alginate) were used to prepare the electrode slurry in a mass ratio of 8:1:1. The slurry was evenly coated on aluminum foil, dried at 90 °C in a vacuum oven for 12 h, cut into 10 mm round electrodes, and assembled into sodium ion half-cells in a glove box under argon protection.

[0028] (2) Assembly of sodium ion half-cells: Sodium metal was used as the counter electrode and 1M NaPF6+DEGDME as the electrolyte. The sodium ion half-cells were assembled in a glove box under argon protection. The assembled cells were sealed using a button cell sealing machine and allowed to stand at room temperature for 12 h.

[0029] (3) Assembly of sodium ion full battery: Prussian blue was used as the positive electrode and 1M NaPF6+DEGDME was used as the electrolyte. The sodium ion full battery was assembled in a glove box under argon protection. The assembled battery was sealed using a button cell sealing machine and allowed to stand at room temperature for 12 h.

[0030] As shown in the attached figure, pre-oxidation introduces abundant oxygen-containing functional groups ( Figure 1 ), which reduces the graphitization degree of the hard carbon material after carbonization ( Figure 2 ), the interlayer spacing increases ( Figure 3 ), while introducing a rich pore structure to provide more sodium storage active sites, showing high capacity and high first efficiency performance.

[0031] like Figure 4 The pre-oxidized hard carbon material has a reversible specific capacity of 369 mAh / g and a high first efficiency of 91%, taking into account both high capacity and high first efficiency performance, and exhibits excellent cycle stability ( Figure 5 ). In addition, the full battery assembled with the hard carbon material prepared by the pre-oxidation strategy and the Prussian blue cathode material also exhibited excellent electrochemical performance ( Figure 6 , Figure 7 ).

[0032] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a negative electrode material for a sodium ion battery having both high capacity and high initial efficiency, characterized in that: The steps include: (1) crushing the biomass precursor, washing and drying it after acid washing and purification; (2) pre-oxidizing the purified biomass in an oxidizing atmosphere to obtain a pre-treated material; (3) The pretreated material is subjected to high-temperature carbonization treatment in an inert atmosphere to obtain a hard carbon material.

2. The method for preparing a negative electrode material for a sodium ion battery having both high capacity and high initial efficiency according to claim 1, characterized in that: The biomass in step (1) includes one or more of bamboo, gourd shells, walnut shells, corn cobs, coconut shells, straw, wood, and bagasse.

3. The method for preparing a negative electrode material for a sodium ion battery having both high capacity and high initial efficiency according to claim 1, characterized in that: The acid solution in step (1) includes one or more of hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid, with a concentration of 1-10M, and the pickling treatment time is 1-12 h.

4. The method for preparing a negative electrode material for a sodium ion battery having both high capacity and high initial efficiency according to claim 1, characterized in that: The oxidation atmosphere in step (2) includes air and oxygen, the oxidation temperature is 100-500°C, the time is 0.5 h-10 h, the heating rate is 1°C / min-10°C / min, and the gas flow rate is 50-300 mL / min.

5. The method for preparing a negative electrode material for a sodium ion battery having both high capacity and high initial efficiency according to claim 1, characterized in that: The inert atmosphere in step (3) includes nitrogen and argon, the carbonization temperature is 1000-1600°C, the time is 1 h-5 h, and the heating rate is 1°C / min-10°C / min.

6. The pre-oxidized material obtained by the preparation method according to claim 1-4, characterized in that: The obtained material after pre-oxidation treatment contains oxygen-containing functional groups.

7. The sodium ion battery hard carbon negative electrode material obtained by the preparation method according to claims 1-5, characterized in that: The interlayer spacing of the obtained hard carbon material is 0.34-0.43 nm and the specific surface area is 10-500 m 2 / g, first coulombic efficiency ≥90%, first-cycle reversible specific capacity ≥360 mAh / g.

8. Application of the sodium ion battery negative electrode material prepared according to the preparation method according to any one of claims 1 to 5 in the field of energy storage.

Images