Preparation method of high-power type sodium ion battery hard carbon negative electrode material and sodium ion battery

Abstract

This invention discloses a method for preparing a high-power sodium-ion battery hard carbon anode material: N,N-dimethylformamide, phosphorus oxychloride, and lignin powder are mixed in an anhydrous closed stirring apparatus under an inert atmosphere, heated to 75-83°C and stirred, then filtered to obtain filter residue rich in imine organic compounds; then added to deionized water and stirred, filtered to obtain formylated lignin powder; the formylated lignin powder is then subjected to high-temperature carbonization under an inert atmosphere to obtain the high-power sodium-ion battery hard carbon anode material. This invention also discloses a sodium-ion battery containing this hard carbon anode material. This invention utilizes the aromatic compounds in lignin to carry out electrophilic substitution reactions, thereby increasing the reversible adsorption of Na on the surface of the hard carbon anode material. + Oxygen-containing groups and oxygen atoms, when doped, will increase the number of active adsorption sites in the material, increase the interlayer spacing, improve the rate performance of the material, and also increase the specific capacity of the material.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery materials, and particularly relates to a method for preparing a high-power sodium-ion battery hard carbon anode material and a sodium-ion battery. Background Technology

[0002] As a widely used electrochemical energy storage device in today's society, the demand for lithium-ion batteries is increasing day by day with the development of new energy vehicles, portable electronic devices and large-scale energy storage technologies. This has also driven the increase in the demand for lithium. However, the tense international relations and the shortage of domestic lithium resources have restricted the development of lithium-ion batteries.

[0003] Sodium-ion battery technology, due to the abundance of sodium resources, high safety performance, and wide operating temperature range, is expected to complement lithium-ion batteries in multiple fields such as A00-class new energy vehicles, two-wheeled electric vehicles, and energy storage grids, making it a promising battery technology. The anode material is crucial for the development of sodium-ion batteries, with carbon-based materials being the most commonly used. Among them, hard carbon, an amorphous carbon material with larger interlayer spacing and higher sodium storage capacity, is an ideal anode material for sodium-ion batteries and is currently widely considered the most promising anode material for sodium-ion batteries. The slow kinetics of traditional sodium-ion battery anode materials limit their application under fast-charging conditions. However, the development of electric vehicles and plug-in hybrid electric vehicles (EVs and PHEVs) has increased the demand for fast-charging technology for sodium-ion batteries. Therefore, developing anode materials with rapid sodium-ion diffusion capabilities is key to achieving fast-charging of sodium-ion batteries.

[0004] For hard carbon anode materials, good conductivity and strong fast charging capability require more active sites, higher material conductivity and more ion channels in the carbon-based material. This can be achieved by adjusting the microstructure of the material and introducing heteroatoms.

[0005] Patent application number 202511172189.7 discloses a method for synthesizing a hard carbon material with a carbon coating approximately 37 nm thick on a spherical hard carbon surface by forming a composite precursor from Rhizopus and glucose through hydrothermal synthesis. By constructing a stable artificial interface layer through surface engineering, direct contact between the negative electrode and the electrolyte is effectively isolated, thereby significantly suppressing side reactions and interface degradation. Simultaneously, this coating optimizes the ion transport path, extending the sodium ion diffusion mode from traditional two-dimensional surface diffusion to three-dimensional bulk diffusion, improving the ion diffusion coefficient and enhancing the battery's rate performance and cycle stability. Although this method optimizes the sodium ion transport path, it still cannot guarantee that the battery will ultimately achieve highly efficient fast charge-discharge performance.

[0006] Patent application number 202111038617.9 discloses a process of forming hard carbon material by heating and stirring a polymer precursor and a phase separation promoter, forming a gel film, phase separation, and carbonization. This material possesses numerous vertically ordered macroporous channels, enriching the Na content in the bulk phase. + Although this sodium-ion battery anode material exhibits considerable sodium storage capacity and rate performance, its preparation process has a low material yield, and the constructed macroporous channels lack sufficient control in terms of uniformity and pore size distribution, resulting in uncertainties in ion transport dynamics. Therefore, it is difficult to ensure the stability of the battery under high power conditions.

[0007] Patent application number 201710540998.8 discloses a method for successfully preparing nitrogen-doped porous carbon materials by mixing ammonium salts such as ammonium phosphate and ammonium fluoride as nitrogen sources with suitable carbon source precursors, followed by high-temperature composite carbonization under an inert atmosphere. When used as a negative electrode in sodium-ion batteries, the incorporation of nitrogen effectively improves the conductivity and surface wettability of the material and creates a certain number of active sites. However, its pore structure is not significantly optimized by this doping process, thus limiting its effect on improving the fast-charging performance of the electrode.

[0008] In summary, most current pretreatment and modification strategies for hard carbon anode materials in sodium-ion batteries are insufficient to meet the requirements of high-power applications for hard carbon anodes, especially in improving battery fast-charging performance, as a fast and stable sodium-ion channel system has not yet been achieved. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a high-power sodium-ion battery hard carbon anode material, its preparation method and sodium-ion battery.

[0010] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0011] A method for preparing a hard carbon anode material for high-power sodium-ion batteries includes the following steps: (1) The biomass raw material is crushed to obtain lignin powder; (2) N,N-dimethylformamide, phosphorus oxychloride and the lignin powder are placed in an anhydrous closed stirring device under an inert atmosphere and mixed. The mixture is heated to 75~83℃ and stirred. The mixture is then filtered to obtain filter residue rich in imine organic matter. (3) Add the filter residue rich in imine organic matter obtained in step (2) to deionized water, stir, filter, and obtain formylated lignin powder; (4) The formylated lignin powder obtained in step (3) is placed in an inert atmosphere for high-temperature carbonization to obtain the high-power sodium-ion battery hard carbon anode material.

[0012] In the above preparation method, preferably, in step (2), the mass ratio of N,N-dimethylformamide, phosphorus oxychloride and lignin powder is (10~12):(1~2):(1.8~2.1).

[0013] In the above preparation method, preferably, in step (2), the gas used for the inert atmosphere includes at least one of argon, nitrogen, hydrogen, helium and neon; the stirring speed is 1~15 rpm and the stirring time is 9~12 h.

[0014] In the above preparation method, preferably, in step (3), the stirring speed is 5~35 rpm and the stirring time is 5~6 h.

[0015] In the above preparation method, preferably, in step (3), the mass ratio of filter residue rich in imine organic matter to deionized water is (1~1.5):(10~20).

[0016] In the above preparation method, preferably, in step (4), the heating rate of high-temperature carbonization is 0.5~10℃ / min, the temperature of high-temperature carbonization is 750℃~1350℃, and the holding time of high-temperature carbonization is 2~6h.

[0017] In the above preparation method, preferably, in step (4), the gas used for the inert atmosphere includes at least one of argon, nitrogen, helium, and neon.

[0018] In the above preparation method, preferably, in step (1), the biomass raw material is at least one of peeled bamboo, straw, walnut shell, coconut shell, and reed; and the Dv50 of the lignin powder is 5~10μm.

[0019] The main mechanism involved in this application is as follows: When lignin powder is added to an electrophilic reagent, lignin, as a phenolic polymer cross-linked with p-hydroxyphenylphenylpropane, guaiacolylphenylpropane, and syringylphenylpropane, undergoes an electrophilic substitution reaction with the electrophilic reagent to generate imine organic compounds. These imine organic compounds are easily hydrolyzed, yielding formylated aromatic compounds. This achieves the goal of precisely introducing carbonyl groups (C=O) onto the surface of the lignin material. Figure 1 As shown. During the subsequent carbonization and pyrolysis process, the oxygen element carries away the carbon atoms from the aromatic rings, causing defects and curling when the material grows into graphene sheets at high temperatures. On the one hand, this creates voids in some parts of the graphene sheets, generating additional adsorption capacity. On the other hand, the curled graphene sheets form more "house of cards" pores, increasing the interlayer spacing and increasing the Na content inside the material. +The transmission channel enables the material to have superior rate performance.

[0020] In step (2), N,N-dimethylformamide (DMF) is used as the amide and phosphorus oxychloride as the acyl chloride to prepare the electrophilic reagent. The specific reaction mechanism is as follows: Figure 2 As shown, the electrophilic reagent undergoes an electrophilic substitution (SEAr) reaction with aromatic compounds in lignin. The reaction mechanism is as follows: Figure 3 As shown.

[0021] Based on a general inventive concept, the present invention also provides a sodium-ion battery, comprising a high-power sodium-ion battery hard carbon anode material prepared by the above-described preparation method.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention utilizes the aromatic compounds in lignin to carry out electrophilic substitution reactions, thereby amplifying the reversible adsorption of Na on the surface of hard carbon anode materials. + Oxygen-containing groups and oxygen atoms, when doped, will increase the number of active adsorption sites in the material, increase the interlayer spacing, improve the rate performance of the material, and also increase the specific capacity of the material.

[0023] (2) This invention utilizes the aromatic compounds in lignin to carry out an electrophilic substitution reaction, followed by hydrolysis, which introduces carbonyl groups onto the surface of the lignin material. The hard carbon anode material gains electrons during charging, making the carbonyl groups negatively charged. After combining with sodium ions, they form -CO. - (Na + The structure stores sodium, and during discharge, the carbonyl group itself has electron-withdrawing properties, making the -CO group... - (Na + ) loses electrons and transforms into -CO(Na) + Sodium ions transfer to the positive electrode under the influence of electrical potential, and the carbonyl group restores its original structure, thereby achieving reversible sodium storage; the carbonyl group on the surface of the material effectively improves the adsorption capacity (slope capacity) of the material.

[0024] (3) The high-power sodium-ion battery hard carbon anode material of the present invention is used to prepare a button cell. At 0.1C, its first reversible specific capacity is above 378mAh / g, its first coulombic efficiency is above 89.72%, its specific capacity at ≥0.1V voltage during discharge is above 258mAh / g, and its capacity retention rate at 5C can reach 88.9% at 1C current density of 300mA / g.

[0025] (4) The synthesis process of the present invention is simple, highly operable, and easy to achieve mass production and commercialization. Attached Figure Description

[0026] Figure 1This is a schematic diagram illustrating the principle of introducing carbonyl groups onto the surface of lignin materials according to the present invention.

[0027] Figure 2 This is a schematic diagram illustrating the specific reaction mechanism for the preparation of electrophilic reagents involved in this invention.

[0028] Figure 3 This is a schematic diagram of the mechanism of the electrophilic substitution (SEAr) reaction between the electrophilic reagent and the aromatic compounds in lignin in this invention.

[0029] Figure 4 This is the XPS image of the hard carbon anode material prepared in Comparative Example 2 of this invention.

[0030] Figure 5 This is the XPS image of the hard carbon anode material prepared in Example 2 of the present invention.

[0031] Figure 6 This is the XRD diffraction pattern of the hard carbon anode material prepared in Example 3 of this invention. Detailed Implementation

[0032] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0033] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0035] Example 1: A method for preparing a high-power sodium-ion battery hard carbon anode material according to the present invention includes the following steps: (1) Peeled bamboo is placed in a mechanical mill and pulverized to obtain lignin powder with Dv50=7μm.

[0036] (2) First, evacuate the vacuum mixer, then fill it with nitrogen. Then, place DMF, phosphorus oxychloride and lignin powder in the vacuum mixer at a mass ratio of 10:1:2 and start stirring at a speed of 10 rpm. Heat the mixture to 77°C and stir for 9 hours. The electrophilic reagent Cl-CON(CH3)2 generated by the reaction of DMF and phosphorus oxychloride will then undergo an electrophilic substitution reaction with p-hydroxyphenylphenylpropane, guaiacolylphenylpropane and syringylphenylpropane in the lignin to form imine salts. Then filter the mixture to obtain the filter residue.

[0037] (3) The filter residue obtained in step (2) and deionized water are placed in a mixer at a mass ratio of 10:170 and stirred at a speed of 20 rpm for 5 hours. After stirring, the mixture is filtered to obtain formylated lignin powder.

[0038] (4) The formylated lignin powder was heated to 1280°C in a nitrogen atmosphere at a heating rate of 3°C / min, and held at the temperature for 2 hours for high-temperature carbonization. After cooling to room temperature, the finished high-power hard carbon anode material was obtained.

[0039] Example 2: A method for preparing a high-power sodium-ion battery hard carbon anode material according to the present invention includes the following steps: (1) The coconut shell is crushed in a mechanical mill to Dv50=100μm, and then put into an air jet mill to crush to Dv50=10μm to obtain lignin powder.

[0040] (2) First, evacuate the vacuum mixer, then fill it with nitrogen. Then, place DMF, phosphorus oxychloride and lignin powder in the vacuum mixer at a mass ratio of 10:1.2:1.8 and start stirring at a speed of 6 rpm. Then, heat the mixture to 80°C and stir for 12 hours. This allows the electrophilic reagent Cl-CON(CH3)2 generated by the reaction of DMF and phosphorus oxychloride to undergo an electrophilic substitution reaction with p-hydroxyphenylphenylpropane, guaiacolylphenylpropane and syringylphenylpropane in the lignin to form imine salts. Then, filter the mixture to obtain the filter residue.

[0041] (3) The imine salt filter residue and deionized water were placed in a mixer at a mass ratio of 10:150 and stirred at a speed of 25 rpm for 5 hours. After stirring, the mixture was filtered to obtain formylated lignin powder.

[0042] (4) The formylated lignin powder was placed in a nitrogen atmosphere and heated to 1280°C at a heating rate of 3°C / min. The temperature was kept constant for 2 hours for high-temperature carbonization. After cooling to room temperature, the finished high-power hard carbon anode material was obtained.

[0043] Example 3: A method for preparing a high-power sodium-ion battery hard carbon anode material according to the present invention includes the following steps: (1) The coconut shell was crushed in a mechanical mill to Dv50=80μm, and then crushed in an air jet mill to Dv50=7μm to obtain lignin powder.

[0044] (2) First, evacuate the vacuum mixer, then fill it with nitrogen. Then, place DMF, phosphorus oxychloride and lignin powder in the vacuum mixer at a mass ratio of 10:1.2:1.8 and start stirring at a speed of 5 rpm. Then, heat the mixture to 78°C and stir for 11.5 h. This allows the electrophilic reagent Cl-CON(CH3)2 generated by the reaction of DMF and phosphorus oxychloride to undergo an electrophilic substitution reaction with p-hydroxyphenylphenylpropane, guaiacolylphenylpropane and syringylphenylpropane to form imine salts. Filter the mixture to obtain the filter residue.

[0045] (3) Place the imine salt filter residue and deionized water in a mixer at a mass ratio of 10:180, start stirring at a speed of 20 rpm, stir for 5 hours to allow the imine salt to hydrolyze into formylated lignin, filter, and obtain formylated lignin powder.

[0046] (4) The formylated lignin powder was heated to 1280℃ in a nitrogen atmosphere at a heating rate of 3℃ / min, and held at that temperature for 2 hours for high-temperature carbonization. After cooling to room temperature, the finished high-power hard carbon anode material was obtained. Its structure was characterized by XRD, such as... Figure 6 As shown, the interplanar spacing d of the material is obtained through fitting calculation. 002 =0.389nm.

[0047] Comparative Example 1: The preparation method of the hard carbon anode material in this comparative example includes the following steps: (1) Peeled bamboo is pulverized in a mechanical mill to Dv50=7μm to obtain lignin powder.

[0048] (2) The lignin powder was placed in a nitrogen atmosphere and heated to 1280℃ at 3℃ / min. The temperature was kept constant for 2 hours for high-temperature carbonization. After cooling to room temperature, hard carbon anode material was obtained.

[0049] Comparative Example 2: The preparation method of the hard carbon anode material in this comparative example includes the following steps: (1) The coconut shell is crushed in a mechanical mill to Dv50=100μm, and then put into an air jet mill to crush to Dv50=10μm to obtain lignin powder.

[0050] (2) The lignin powder was heated to 1280°C in a nitrogen atmosphere at a heating rate of 3°C / min and kept at the temperature for 2 hours for high-temperature carbonization. After cooling to room temperature, hard carbon material was obtained.

[0051] (3) First, evacuate the vacuum mixer, then fill it with nitrogen. Then, place DMF, phosphorus oxychloride and hard carbon material in the vacuum mixer at a mass ratio of 10:1.2:1.8 and start stirring at a speed of 6 rpm. Heat the mixture to 80°C and stir for 12 hours. Then filter to obtain hard carbon anode material.

[0052] The particle size of the hard carbon anode materials prepared in the above examples and comparative examples was tested in a Mastersizer 3000+ Ultra, and the interplanar spacing was analyzed after observation using a JEOL F200. Using the hard carbon anode materials prepared in the above examples and comparative examples as the anode, sodium sheet as the cathode, glass fiber as the separator, and 1.0M NaPF6 indiglyme=100Vol% as the electrolyte, coin cells were assembled. The specific capacity at 0.1C, the initial coulombic efficiency, and the specific capacity at 0.1V during discharge were measured. The specific capacity at 5C was then further measured. The results are shown in Table 1.

[0053] Table 1. Particle size, interplanar spacing, and electrochemical performance of the hard carbon anode materials in each embodiment and comparative example.

[0054] The difference between Example 2 and Comparative Example 2 is that Example 2 involves electrophilic substitution of coconut shell lignin and precise introduction of carbonyl groups (C=O) onto the surface of the lignin material through hydrolysis. The surface oxygen-containing functional groups of the hard carbon anode materials prepared in Example 2 and Comparative Example 2 are characterized by X-ray photoelectron spectroscopy (XPS), as shown below. Figure 5 and Figure 4 As shown, the carbonyl (C=O) content in Example 2 is higher than that in Comparative Example 2. Correspondingly, the specific capacity of Example 2 at 0.1V discharge voltage is higher than that of Comparative Example 2, indicating that the introduction of carbonyl (C=O) significantly improves the slope region capacity—adsorption capacity.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a hard carbon anode material for a high-power sodium-ion battery, characterized in that, Includes the following steps: (1) The biomass raw material is crushed to obtain lignin powder; (2) N,N-dimethylformamide, phosphorus oxychloride and the lignin powder are placed in an anhydrous closed stirring device under an inert atmosphere and mixed. The mixture is heated to 75~83℃ and stirred. The mixture is then filtered to obtain filter residue rich in imine organic matter. (3) Add the filter residue rich in imine organic matter obtained in step (2) to deionized water, stir, filter, and obtain formylated lignin powder; (4) The formylated lignin powder obtained in step (3) is placed in an inert atmosphere for high-temperature carbonization to obtain the high-power sodium-ion battery hard carbon anode material.

2. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of N,N-dimethylformamide, phosphorus oxychloride and lignin powder is (10~12):(1~2):(1.8~2.1).

3. The preparation method according to claim 1, characterized in that, In step (2), the gas used for the inert atmosphere includes at least one of argon, nitrogen, hydrogen, helium and neon; the stirring speed is 1~15 rpm and the stirring time is 9~12 h.

4. The preparation method according to claim 1, characterized in that, In step (3), the stirring speed is 5~35 rpm and the stirring time is 5~6 h.

5. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of filter residue rich in imine organic matter to deionized water is (1~1.5):(10~20).

6. The preparation method according to claim 1, characterized in that, In step (4), the heating rate of the high-temperature carbonization is 0.5~10℃ / min, the temperature of the high-temperature carbonization is 750℃~1350℃, and the holding time of the high-temperature carbonization is 2~6h.

7. The preparation method according to claim 1, characterized in that, In step (4), the gas used for the inert atmosphere includes at least one of argon, nitrogen, helium, and neon.

8. The preparation method according to claim 1, characterized in that, In step (1), the biomass raw material is at least one of peeled bamboo, straw, walnut shell, coconut shell, and reed; the Dv50 of the lignin powder is 5~10μm.

9. A sodium-ion battery, characterized in that, This includes high-power sodium-ion battery hard carbon anode materials prepared by the preparation method according to any one of claims 1 to 8.

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