A phycocyanin-based pea-shaped sodium ion battery hard carbon negative electrode material and its preparation method

Abstract

The present invention discloses a phycocyanin-based pea-shaped hard carbon anode material for sodium ion batteries and its preparation method, belonging to the technical field of sodium ion batteries. The anode material is prepared by calcining and ball-milling phycocyanin in an air atmosphere, followed by a secondary calcination in an inert gas atmosphere. The preparation method of the present invention is simple, and the entire preparation process does not require the use of acids or bases, making it suitable for large-scale production. Furthermore, the phycocyanin precursor used can allow the prepared hard carbon anode material to be self-doped with nitrogen, eliminating the need for an additional nitrogen-doping step to obtain a hard carbon anode material with excellent performance.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a phycocyanin-based pea-shaped hard carbon negative electrode material for sodium ion batteries and a preparation method thereof. Background Art

[0002] Sodium ranks seventh in abundance in the Earth's crust, accounting for approximately 2.5% of its total mass. Compared to lithium, sodium resources are more abundant and widespread. Therefore, the development of sodium-ion batteries is a key means of reducing dependence on lithium resources, ensuring resource supply security, and reducing costs and increasing efficiency. When sodium-ion batteries establish an industrial chain driven by economies of scale, they will complement the strengths of lithium-ion batteries and have promising applications in low-speed vehicles and large-scale energy storage.

[0003] Sodium ion battery negative electrode materials mainly include: hard carbon, soft carbon, transition metal oxides and alloy materials. Among the existing methods, hard carbon negative electrodes have been widely studied due to their advantages such as a wide range of biomass precursor sources and rich sodium storage sites. They are currently the negative electrode materials with the greatest potential for large-scale production. However, the preparation process of many biomass precursor-based hard carbon negative electrode materials is relatively complicated, and most of them contain acid washing and alkaline activation steps, which cause environmental pollution. In addition, the electrochemical performance of the obtained hard carbon materials is poor, making it difficult to be widely used in sodium ion batteries. Patent CN 106744934 A discloses a method for preparing sodium ion battery electrode carbon materials using bamboo. The preparation process is relatively complicated, and the use of acid and alkali will lead to the generation of wastewater and waste gas. Therefore, it is not an ideal large-scale application method. CN 113292064A discloses a method for preparing sodium ion battery negative electrode materials, but the fermentation cycle is too long and the first coulombic efficiency of the obtained hard carbon negative electrode material is low, which is not suitable for large-scale preparation scenarios. Therefore, it is of great practical significance to develop new biomass precursors and optimize the preparation process of hard carbon negative electrodes. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention proposes a phycocyanin-based pea-shaped hard carbon negative electrode material for sodium ion batteries and a preparation method thereof. The purpose is to use phycocyanin extracted from Spirulina platensis as a precursor, and obtain a sodium ion hard carbon negative electrode material self-doped with nitrogen element through a simple and pollution-free preparation process. When applied to sodium ion batteries, the negative electrode material exhibits relatively excellent electrochemical performance.

[0005] To achieve the purpose, the present invention adopts the following technical solutions:

[0006] A method for preparing a phycocyanin-based pea-shaped hard carbon negative electrode material for sodium ion batteries, comprising the following steps:

[0007] 1) heating the phycocyanin in a muffle furnace at a heating rate of 2-5°C / min to 200-250°C, maintaining the temperature for 4-8 hours in an air atmosphere, and then cooling the mixture to room temperature to obtain a first intermediate product;

[0008] 2) ball milling the first intermediate product for 0.25 to 1 hour to obtain a second intermediate product;

[0009] 3) The second intermediate product is placed in a tubular furnace, heated to 1200-1500°C at a heating rate of 2-5°C / min under an inert gas atmosphere, kept at this temperature for 2-4 hours, then cooled to 40-60°C at a cooling rate of 2-5°C / min, and then cooled to room temperature with the furnace to obtain a phycocyanin-based pea-shaped sodium ion battery hard carbon negative electrode material.

[0010] Furthermore, in the above technical solution, the phycocyanin in step 1) is extracted from Spirulina platensis.

[0011] Furthermore, in the above technical solution, in step 2), the ball-to-material ratio of the ball milling (ie, the mass ratio of the ball milling beads to the second intermediate to be ball milled) is 4 to 6:1.

[0012] Furthermore, in the above technical solution, in step 3), the inert gas is argon.

[0013] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0014] 1. The preparation process is simple and suitable for large-scale production.

[0015] 2. The entire preparation process avoids the use of acid and alkali, reducing environmental pressure.

[0016] 3. The phycocyanin precursor can enable the prepared hard carbon negative electrode material to be self-doped with nitrogen elements, and a hard carbon negative electrode material with excellent performance can be obtained without the need for an additional nitrogen doping step. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the SEM image of the hard carbon negative electrode material for sodium ion batteries prepared in Example 1.

[0018] Figure 2 This is the EDS spectrum of the hard carbon negative electrode material for sodium ion batteries prepared in Example 1.

[0019] Figure 3 The first cycle charge and discharge curves of the hard carbon negative electrode materials for sodium ion batteries prepared in Examples 1-3 and Comparative Examples 1-3.

[0020] Figure 4 This is a long cycle performance diagram of the sodium ion battery hard carbon negative electrode material prepared in Example 1. DETAILED DESCRIPTION

[0021] The technical solutions of the present invention are further described and explained below in conjunction with examples, but these examples are not intended to limit the scope of protection of the present invention.

[0022] Example 1

[0023] 1) Weigh 5 g of commercial phycocyanin extracted from Spirulina platensis, place the mixture in a muffle furnace and heat it to 230° C. at a heating rate of 3° C. / min, keep the temperature under air atmosphere for 6 h, and then cool it to room temperature to obtain a first intermediate product.

[0024] 2) Weigh 2 g of the first intermediate product and 10 g of ball mill beads, and ball mill them for 0.5 h to obtain the second intermediate product.

[0025] 3) The second intermediate product was placed in a tubular furnace, heated to 1300°C at a heating rate of 3°C / min under an argon atmosphere, kept warm for 3 hours, then cooled to 50°C at a cooling rate of 3°C / min and then cooled to room temperature with the furnace, finally obtaining a phycocyanin-based pea-shaped sodium ion battery hard carbon negative electrode material product.

[0026] Figure 1 This is an SEM image of the hard carbon negative electrode material for sodium ion batteries prepared in Example 1. It can be seen that the hard carbon material exhibits a typical pea-shaped morphology.

[0027] Figure 2 This is the EDS spectrum of the hard carbon negative electrode material for sodium ion batteries prepared in Example 1. The results show that the C, O, and N elements are evenly distributed in the hard carbon material, and the N content is about 2.7%. The presence of the N element can increase the charge transfer capacity of the material and provide more active sites for the embedding of sodium ions.

[0028] Example 2

[0029] 1) Weigh 5 g of commercial phycocyanin extracted from Spirulina platensis, place the mixture in a muffle furnace and heat it to 230° C. at a heating rate of 3° C. / min, keep the temperature under air atmosphere for 6 h, and then cool it to room temperature to obtain a first intermediate product.

[0030] 2) Weigh 2 g of the first intermediate product and 10 g of ball mill beads, and ball mill them for 0.5 h to obtain the second intermediate product.

[0031] 3) The second intermediate product was placed in a tubular furnace, heated to 1500°C at a heating rate of 3°C / min under an argon atmosphere, kept warm for 3 hours, then cooled to 50°C at a cooling rate of 3°C / min and then cooled to room temperature with the furnace, finally obtaining a phycocyanin-based pea-shaped sodium ion battery hard carbon negative electrode material product.

[0032] Example 3

[0033] 1) Weigh 5 g of commercial phycocyanin extracted from Spirulina platensis, place the mixture in a muffle furnace and heat it to 230° C. at a heating rate of 3° C. / min, keep the temperature under air atmosphere for 8 h, and then cool it to room temperature to obtain a first intermediate product.

[0034] 2) Weigh 2 g of the first intermediate product and 10 g of ball mill beads, and ball mill them for 1 h to obtain the second intermediate product.

[0035] 3) The second intermediate product was placed in a tubular furnace, heated to 1500°C at a heating rate of 3°C / min under an argon atmosphere, kept warm for 3 hours, then cooled to 50°C at a cooling rate of 3°C / min and then cooled to room temperature with the furnace, finally obtaining a phycocyanin-based pea-shaped sodium ion battery hard carbon negative electrode material product.

[0036] Comparative Example 1

[0037] 1) Weigh 5 g of commercial phycocyanin extracted from Spirulina platensis, place the mixture in a muffle furnace and heat it to 230° C. at a heating rate of 3° C. / min, keep the temperature under air atmosphere for 6 h, and then cool it to room temperature to obtain a first intermediate product.

[0038] 2) Weigh 2 g of the first intermediate product and 10 g of ball milling beads, and use a ball mill to ball mill for 0.5 h to obtain a second intermediate product.

[0039] 3) The second intermediate product was placed in a tubular furnace, heated to 1100°C at a heating rate of 3°C / min under an argon atmosphere, then kept warm for 3 hours, and then cooled to 50°C at a cooling rate of 3°C / min and then cooled to room temperature with the furnace, finally obtaining a phycocyanin-based pea-shaped sodium ion battery hard carbon negative electrode material product.

[0040] Comparative Example 2

[0041] 1) Weigh 5 g of commercial corn starch, place it in a muffle furnace, heat it to 230° C. at a heating rate of 3° C. / min, keep it at this temperature for 6 h in an air atmosphere, and then cool it to room temperature in the furnace to obtain a first intermediate product.

[0042] 2) Weigh 2 g of the first intermediate product and 10 g of ball milling beads, and use a ball mill to ball mill for 0.5 h to obtain a second intermediate product.

[0043] 3) The second intermediate product was placed in a tubular furnace, heated to 1300°C at a heating rate of 3°C / min under an argon atmosphere, kept warm for 3 hours, then cooled to 50°C at a cooling rate of 3°C / min and then cooled to room temperature with the furnace, finally obtaining a finished starch-based sodium ion battery hard carbon negative electrode material.

[0044] Comparative Example 3

[0045] 1) Weigh 5 g of commercial sucrose and place it in a muffle furnace. Heat the temperature to 230° C. at a rate of 3° C. / min, maintain the temperature for 6 h in an air atmosphere, and then cool it to room temperature in the furnace to obtain a first intermediate product.

[0046] 2) Weigh 2 g of the first intermediate product and 10 g of ball milling beads, and use a ball mill to ball mill for 0.5 h to obtain a second intermediate product.

[0047] 3) The second intermediate product was placed in a tubular furnace, heated to 1300°C at a heating rate of 3°C / min under an argon atmosphere, kept warm for 3 hours, then cooled to 50°C at a cooling rate of 3°C / min and cooled to room temperature with the furnace, finally obtaining a finished product of a sucrose-based sodium ion battery hard carbon negative electrode material.

[0048] The sodium-ion battery hard carbon anode material obtained in the above examples and comparative examples was added to deionized water at a mass ratio of 8:1:1, along with carbon black and sodium carboxymethyl cellulose. The mixture was stirred for 1 hour. The resulting slurry was then applied to the surface of a copper current collector using a spatula and dried in a forced-air drying oven for 8 hours before being formed into electrode sheets with a diameter of 14 mm. CR2032 button cells were assembled in an argon-filled glove box using the resulting electrode sheets as working electrodes and the sodium sheet as counter electrodes. The separator used was glass fiber, and the electrolyte was a 1 mol / L solution of sodium hexafluorophosphate in diethylene glycol dimethyl ether. Electrochemical testing was performed on a Newway CT-4008 tester over a charge and discharge voltage range of 0.01 to 3 V.

[0049] Figure 3 The first-cycle charge-discharge curves of the hard carbon negative electrode materials for sodium ion batteries prepared in Examples 1-3 and Comparative Examples 1-3 are shown. As can be seen from the figure, the hard carbon negative electrode materials in Examples 1, 2, and 3 exhibit relatively high first-cycle coulombic efficiencies (85.0%, 84.0%, and 83.7%, respectively), while the coulombic efficiencies of the comparative examples are relatively low (74.7%, 78.9%, and 73.1%, respectively). The higher coulombic efficiencies of Examples 1-3 indicate that irreversible sodium consumption due to defects, side reactions, etc. is relatively low.

[0050] Figure 4 This is a graph showing the long-cycle performance of the hard carbon anode material for sodium-ion batteries prepared in Example 1. It can be seen that at a current density of 150 mA / g, the hard carbon material still has a reversible capacity of 265 mAh / g after 200 cycles, with a capacity retention rate of up to 95.5%, indicating that this hard carbon anode material for sodium-ion batteries has good cycling stability.

[0051] The above embodiments are only preferred embodiments of the present invention and are intended to illustrate the technical concept and features of the present invention, and are not intended to limit the present invention. It should be noted that any simple variations, replacements, and improvements made based on the spirit of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a phycocyanin-based pea-shaped hard carbon negative electrode material for sodium ion batteries, characterized in that: The following steps are involved: 1) heating the phycocyanin in a muffle furnace at a heating rate of 2-5°C / min to 200-250°C, maintaining the temperature for 4-8 hours in an air atmosphere, and then cooling the mixture to room temperature to obtain a first intermediate product; 2) ball milling the first intermediate product for 0.25 to 1 hour to obtain a second intermediate product; 3) The second intermediate product is placed in a tubular furnace, heated to 1200-1500°C at a heating rate of 2-5°C / min under an inert gas atmosphere, kept at this temperature for 2-4 hours, then cooled to 40-60°C at a cooling rate of 2-5°C / min, and then cooled to room temperature with the furnace to obtain a phycocyanin-based pea-shaped sodium ion battery hard carbon negative electrode material.

2. The method for preparing a phycocyanin-based pea-shaped hard carbon negative electrode material for sodium ion batteries according to claim 1, characterized in that: The phycocyanin in step 1) is extracted from Spirulina platensis.

3. The method for preparing a phycocyanin-based pea-shaped hard carbon negative electrode material for sodium ion batteries according to claim 1, characterized in that: In step 2), the ball-to-material ratio of the ball milling is 4 to 6:

1.

4. The method for preparing a phycocyanin-based pea-shaped hard carbon negative electrode material for sodium ion batteries according to claim 1, characterized in that: In step 3), the inert gas is argon.

5. A phycocyanin-based pea-shaped hard carbon negative electrode material for sodium ion batteries, characterized by: The method according to any one of claims 1 to 4 is prepared.

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