Preparation method and application of sodium ion battery hard carbon negative electrode material

Abstract

The invention relates to a preparation method of a sodium ion battery hard carbon negative electrode material, and belongs to the field of new materials. Aiming at the problems of complex preparation process, high cost and insufficient electrochemical performance of the existing hard carbon material, the preparation method comprises the following steps: mixing soybean gum biomass, anhydrous citric acid and urea according to a mass ratio, grinding, and carrying out a two-stage gradient carbonization process: pre-carbonizing at a low temperature of 100-400 DEG C for 1-5 hours, carbonizing at a high temperature of 800-1700 DEG C for 1-5 hours, and carrying out high-temperature carbonization at a high temperature of 800-1700 DEG C for 1-5 hours. And the hard carbon material with the optimized pore structure and interlayer spacing is constructed. The obtained material still keeps the reversible specific capacity of 308.01 mAh / g after 50 cycles under the current density of 30mA / g, and still has the capacity retention rate of 79.85 mAh / g under the high rate of 1.5 A / g. Compared with a traditional single-time carbonization process, the method has the advantages that the diffusion dynamic performance of sodium ions is remarkably improved by synergistically regulating and controlling the microstructure of the material through stage carbonization, and meanwhile, the industrial production potential is achieved by adopting cheap biomass raw materials and a simple preparation process. The hard carbon material can be applied to manufacturing of a sodium-ion battery negative plate and a button battery, and has important significance for promoting the development of a novel energy storage device.

Description

Technical Field

[0001] The present invention belongs to the field of new materials, and relates to a preparation method and application of a hard carbon anode material for a sodium-ion battery. Background Art

[0003] With the in-depth development of the research on anode materials for sodium-ion batteries, it has been found that hard carbon has advantages such as rich raw materials, low cost, and relatively stable structure, which makes it the primary anode material attracting much attention in the field of sodium-ion batteries. However, currently, commercially available hard carbon produced on a large scale is difficult to meet the electrochemical performance requirements of anode materials for sodium-ion batteries, showing a low specific capacity and poor rate performance. Moreover, the preparation process of commercially available hard carbon materials is complex and costly, restricting the further application of sodium-ion batteries. Therefore, there is an urgent need to find a high-performance hard carbon anode material for sodium-ion batteries that can be prepared by a simple process method, which will further promote the large-scale commercial application of hard carbon materials. Numerous studies have shown that through secondary high-temperature carbonization, the defects and interlayer spacing of hard carbon can be changed to provide more active sites, promoting electron conductivity and diffusion kinetics, and ultimately obtaining more excellent electrochemical performance.

[0004] Li et al. synthesized N, S-doped carbon using a simple one-step high-temperature pyrolysis method with walnut shells as raw materials. After 1500 charge-discharge cycles at a current density of 1000 mA / g, the reversible specific capacity was only 182 mAh / g, and the rate performance was poor. Zhang et al. prepared a hard carbon spherical structure by an emulsion method and high-temperature pyrolysis using (NH4)2HPO4 as a nitrogen dopant. The nitrogen content was extremely low, and the crystal plane spacing was only 0.375 nm. The charge-discharge specific capacity at a current density of 800 mA / g was only 100 mAh / g, and the charge-discharge cycle stability was poor. This was because the insertion and extraction of sodium ions with a large ionic radius damaged the internal microstructure of hard carbon, resulting in a loss of reversible capacity.

[0005] The patent with the application number 202311615951.5 reports that using saccharide substances as precursors, a porous carbon nanosheet structure is constructed by igniting a carbon source, heteroatom dopants, and a structure modifier, and a large number of active sites are generated by the high temperature of the flame to form N, S, O heteroatom-doped hard carbon. The patent with the application number 202310301037.7 mixes rosin, a nitrogen source, metal salts, alkali metal hydroxides, and a solvent and then carbonizes them at a high temperature of 600 - 900 °C to obtain a rosin-based nitrogen-doped porous hard carbon material. The patent with the application number 202211676320.X selects biomass materials and organic carbon sources as raw materials, and through two high-temperature calcinations, the elements of iron, cobalt, and nickel further catalyze the biomass precursor materials to form a composite biomass hard carbon material with organic hard carbon coated on biomass hard carbon. The biomass hard carbon inhibits the side reaction between biomass carbon and the electrolyte by coating the surface with organic carbon, removes the residual metal on the surface by acid treatment, and further dopes boron, sulfur, phosphorus, and nitrogen elements on the surface by microwave treatment to improve its conductivity.

[0006] There are some deficiencies in the method of preparing hard carbon materials by high temperature. For example, the synthesis of element-doped hard carbon materials requires many additives, has a high cost, and complex process conditions. In addition to the above patents, there are also many preparation methods for hard carbon materials. These methods are time-consuming and costly in the actual doping process, and the electrochemical performance of the finally obtained electrode materials tested is not ideal, and the preparation yield is low. Summary of the Invention

[0007] In view of this, one of the purposes of the present invention is to provide a preparation method for a hard carbon negative electrode material for a sodium-ion battery, and the second purpose is to provide an application of the hard carbon negative electrode material for a sodium-ion battery in the preparation of a negative electrode for a sodium-ion battery.

[0008] To achieve the above objectives, the present invention provides the following technical solutions:

[0009] The present invention provides a preparation method for a hard carbon negative electrode material for a sodium-ion battery, and the specific steps are as follows: Mix a legume-based biomass, anhydrous citric acid, and urea according to a mass ratio and place them in a grinding dish to grind evenly. Subsequently, perform staged temperature-raising carbonization in a high-temperature tube furnace. After the carbonization is completed, the hard carbon negative electrode material for the sodium-ion battery can be obtained;

[0010] Preferably, the legume-based biomass is at least one of plant gum-based biomasses such as locust bean gum, tamarind gum, sesbania gum, guar gum, linseed gum, coumarin gum, and Chinese honey locust bean gum;

[0011] Preferably, the mass ratio of the legume-based biomass, anhydrous citric acid, and urea is 1:0.1 - 1:0.1 - 1;

[0012] Preferably, the stepwise temperature-rising carbonization process is as follows: under an argon atmosphere, first heat to 100-400°C at a rate of 1-5°C / min and carbonize for 1-5 h, and then continue to heat to 800-1700°C at a rate of 1-5°C / min and carbonize for 1-5 h;

[0013] Furthermore, the application of the hard carbon negative electrode material for sodium-ion batteries in the preparation of the negative electrode material for sodium-ion batteries;

[0014] Furthermore, the present invention also provides a hard carbon negative electrode sheet for sodium-ion batteries, which is prepared by mixing the hard carbon negative electrode material for sodium-ion batteries, conductive carbon black, and polyvinylidene fluoride in a mass ratio of 8:1:1, adding N-methylpyrrolidone, mixing evenly, coating on a copper foil, and drying in a vacuum oven at 60-90°C;

[0015] Furthermore, the present invention also provides a button cell, which includes a negative electrode sheet prepared from the hard carbon negative electrode material for sodium-ion batteries, the electrolyte is a solution of 1M NaPF6 dissolved in ethylene glycol dimethyl ether (DME), and the separator is a glass fiber separator.

[0016] The beneficial effects of the present invention are as follows:

[0017] A high-performance hard carbon negative electrode material for sodium-ion batteries is prepared by a simple stepwise temperature-rising carbonization method. The process is simple and low-cost, and can meet large-scale industrial production. The sodium-ion half-cell assembled with the hard carbon material prepared by the present invention is tested in the voltage range of 0.01-3V and is found to still have a specific capacity of 308.01 mAh / g after 50 cycles at a current density of 30 mA / g, and has reversible sodium storage capacities of 304.06, 291.1, 255.56, 213.05, 148.63, 106.16, and 79.85 mAh / g at current densities of 0.03, 0.06, 0.15, 0.3, 0.6, 1.0, and 1.5 A / g, respectively. The prepared hard carbon material has higher specific capacity and rate performance.

[0018] The process innovation and cost advantages of the present invention are as follows: Simplification of the preparation process: simple grinding + two-stage carbonization is adopted, reducing 1 / 3 of the production processes compared with the existing three-stage calcination process; Reduction of raw material cost: selecting gum-based biomass (such as locust bean gum) to replace precious metal catalysts, reducing the raw material cost by 60% compared with the metal salt catalytic system; Improvement of energy consumption efficiency: two-stage gradient temperature-rising reduces the peak temperature by 200-300°C compared with the traditional high-temperature one-step method, and reduces the comprehensive energy consumption by 25%.

[0019] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the examination and research of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. Brief Description of the Drawings

[0020] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0021] Figure 1 is the cyclic voltammetry curve of the hard carbon materials prepared in Example 1 and Example 2 at a current density of 30 mA / g for 50 cycles;

[0022] Figure 2 is the rate performance diagram of the hard carbon materials prepared in Example 1 and Example 2 at different current densities;

[0023] Figure 3 is the HRTEM diagram of the hard carbon material prepared in Example 1;

[0024] Figure 4 is the XRD diagram of the hard carbon materials prepared in Example 1 and Example 2. Detailed Description of the Embodiments

[0025] The following specific examples illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following examples only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following examples and the features in the examples can be combined with each other.

[0026] Among them, the drawings are only used for exemplary illustration, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation to the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged, or reduced, which do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0027] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and cannot be construed as a limitation on the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0028] Example 1

[0029] (1) Place a certain mass of well-dried locust bean gum, anhydrous citric acid, and urea in a mortar in a mass ratio of 1:0.2:0.225 and grind them evenly.

[0030] (2) Under an argon atmosphere, first heat it from room temperature to 100 - 400 °C at a rate of 1 - 5 °C / min for carbonization for 1 - 5 h, and then continue to heat it to 800 - 1700 °C at a rate of 1 - 5 °C / min for carbonization for 1 - 5 h to obtain the hard carbon material.

[0031] (3) Mix the hard carbon material prepared in step (2) with conductive carbon black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, add an appropriate amount of N-methylpyrrolidone (NMP), mix evenly, coat it on a copper foil, dry it in a vacuum oven at 60 - 90 °C, use a Na sheet as the negative electrode, the electrolyte is a mixed system containing 1 M NaPF6 / DME, the separator is a glass fiber separator, and assemble it into a CR2032 button cell in a glove box with the water and oxygen content less than 0.01 ppm and filled with argon.

[0032] (4) As Figure 1 shown, the half-cell assembled with the hard carbon material (Example 1) prepared by two-step carbonization was tested in the voltage range of 0.01 - 3 V, and it was found that it still had a reversible specific capacity of 308.01 mAh / g after cycling 50 times at a current density of 30 mA / g. Figure 3 This is the HRTEM image of the hard carbon material prepared in Example 1. It can be seen that carbon dots are successfully synthesized and evenly distributed around it. Figure 4 This is the XRD pattern of the hard carbon materials prepared in Example 1 and Example 2. It can be found that the hard carbon material modified with carbon dots has a larger carbon layer spacing.

[0033] Example 2

[0034] (1) Place a certain mass of well-dried locust bean gum in a porcelain boat.

[0035] (2) Under an argon atmosphere, it is heated to 800 - 1700 °C at a rate of 1 - 5 °C / min for carbonization for 1 - 5 h to obtain the required hard carbon material.

[0036] (3) Mix the hard carbon material prepared in step (2) with conductive carbon black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, then add an appropriate amount of N-methylpyrrolidone (NMP), mix evenly, coat it on a copper foil, dry it in a vacuum oven at 60 - 90 °C, use a Na sheet as the negative electrode, the electrolyte is a mixed system containing 1 M NaPF6 / DME, the separator is a glass fiber separator, and assemble it into a CR2032 button cell in a glove box with the water and oxygen content both less than 0.01 ppm and filled with argon.

[0037] (4) As Figure 1 shown, the hard carbon material prepared by one-time carbonization (Example 2) is used to assemble a half-cell and tested in the voltage range of 0.01 - 3 V. It is found that it still has a reversible specific capacity of 252.86 mAh / g after 50 cycles at a current density of 30 mA / g. Figure 1 The cycle curve diagram of the hard carbon materials prepared in Example 1 and Example 2 at a current density of 30 mA / g. It can be clearly seen that the hard carbon material prepared in Example 1 has a discharge specific capacity of 308.01 mAh / g after 50 cycles of assembling and testing the half-cell, while the hard carbon prepared in Example 2 only has a reversible specific capacity of 252.86 mAh / g.

[0038] Figure 2 The rate performance diagram of the hard carbons prepared in Example 1 and Example 2 at different current densities. The figure shows that the hard carbon prepared in Example 1 has reversible sodium storage capacities of 304.06, 291.1, 255.56, 213.05, 148.63, 106.16, 79.85 mAh / g at current densities of 0.03, 0.06, 0.15, 0.3, 0.6, 1.0, 1.5 A / g respectively, while the hard carbon prepared in Example 2 has reversible sodium storage capacities of 270.66, 259.65, 238.89, 209.01, 149.99, 111.91, 83.77 mAh / g at current densities of 0.03, 0.06, 0.15, 0.3, 0.6, 1.0, 1.5 A / g respectively.

[0039] Example 3

[0040] (1) Place at least one of dried tamarind gum, sesbania gum, guar gum, linseed gum, coumarin gum, and Gleditsia sinensis gum, anhydrous citric acid, and urea in a mortar in a mass ratio of 1:0.2:0.225 and grind them evenly.

[0041] (2) Under an argon atmosphere, first heat it from room temperature to 100 - 400 °C at a rate of 1 - 5 °C / min for carbonization for 1 - 5 h, and then continue to heat it to 800 - 1700 °C at a rate of 1 - 5 °C / min for carbonization for 1 - 5 h.

[0042] (3) Mix the hard carbon material prepared in step (2) with conductive carbon black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, add an appropriate amount of N-methylpyrrolidone (NMP), mix evenly, coat it on a copper foil, dry it in a vacuum oven at 60 - 90 °C, use a Na sheet as the negative electrode, the electrolyte is a mixed system containing 1 M NaPF6 / DME, the separator is a glass fiber separator, and assemble it into a CR2032 coin-type battery in a glove box filled with argon with the water and oxygen contents both less than 0.01 ppm. The assembled battery is tested within a voltage range of 0.01 - 3 V.

[0043] Example 4

[0044] (1) Place at least one of dried tamarind gum, sesbania gum, guar gum, linseed gum, coumarin gum, and Chinese honey locust gum with a certain mass in a porcelain boat;

[0045] (2) Under an argon atmosphere, heat it from room temperature to 800 - 1700 °C at a rate of 1 - 5 °C / min for carbonization for 1 - 5 h to prepare a hard carbon material.

[0046] (3) Mix the hard carbon material prepared in step (2) with conductive carbon black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, add an appropriate amount of N-methylpyrrolidone (NMP), mix evenly, coat it on a copper foil, dry it in a vacuum oven at 60 - 90 °C, use a Na sheet as the negative electrode, the electrolyte is a mixed system containing 1 M NaPF6 / DME, the separator is a glass fiber separator, and assemble it into a CR2032 coin-type battery in a glove box filled with argon with the water and oxygen contents both less than 0.01 ppm. The assembled battery is tested within a voltage range of 0.01 - 3 V.

[0047] The above examples only list some methods for preparing hard carbon from legume gum-based biomass materials. The preparation methods for unlisted legume gum-based biomass materials are similar to the above.

[0048] Table 1 Electrochemical performance of sodium-ion batteries

[0049]

[0050] As can be seen from Table 1, the hard carbon materials prepared in Example 1 all have relatively high initial discharge specific capacity, initial charge specific capacity, and initial efficiency; while the initial charge specific capacity and initial efficiency of the materials in Example 2 are lower than those in Example 1. This is because the hard carbon materials prepared in Example 2 do not adopt stepwise temperature rise to regulate the pore structure, layer spacing, etc. of the hard carbon, which results in the reduction of its initial charge-discharge specific capacity and initial efficiency. This shows that the hard carbon materials prepared by one-step simple stepwise temperature rise carbonization have more excellent rate performance and cycle stability.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered by the scope of the claims of the present invention.

Claims

1. Preparation method of hard carbon negative electrode material for sodium ion battery, characterized in that The specific steps are as follows: Mix the gum-based biomass, anhydrous citric acid, and urea in a mass ratio and place them in a grinding dish to grind evenly. Then, perform staged temperature-raising carbonization in a high-temperature tube furnace. After the carbonization is completed, the sodium-ion battery hard carbon negative electrode material can be obtained.

2. The preparation method of the hard carbon anode material for a sodium-ion battery according to claim 1, characterized in that: The gum-based biomass is at least one of locust bean gum, tamarind gum, sesbania gum, guar gum, linseed gum, coumarin gum, and Gleditsia sinensis gum.

3. The preparation method of the hard carbon negative electrode material for a sodium ion battery according to claim 1, wherein: The mass ratio of the gum-based biomass, anhydrous citric acid, and urea is 1:0.1 - 1:0.1 - 1.

4. The preparation method of the hard carbon negative electrode material for a sodium-ion battery according to claim 1, wherein: The staged temperature-raising carbonization process is as follows: Under an argon atmosphere, first heat up to 100 - 400 °C at a rate of 1 - 5 °C / min for carbonization for 1 - 5 h, and then continue to heat up to 800 - 1700 °C at a rate of 1 - 5 °C / min for carbonization for 1 - 5 h.

5. The sodium-ion battery hard carbon negative electrode material prepared by the preparation method of the sodium-ion battery hard carbon negative electrode material according to any one of claims 1 - 4.

6. The application of the sodium-ion battery hard carbon negative electrode material according to claim 5 in the preparation of a sodium-ion battery negative electrode material.

7. Hard carbon negative electrode sheet for sodium ion battery, characterized in that: It is prepared by mixing the sodium-ion battery hard carbon negative electrode material according to claim 5, conductive carbon black, and polyvinylidene fluoride in a mass ratio of 8:1:1, adding N-methylpyrrolidone, mixing evenly, coating it on a copper foil, and drying it in a vacuum oven at 60 - 90 °C.

8. Button-type sodium-ion battery, characterized in that: It includes the sodium-ion battery hard carbon negative electrode sheet according to claim 7, the electrolyte is a solution of 1 M NaPF6 dissolved in ethylene glycol dimethyl ether, and the separator is a glass fiber separator.

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