Preparation method of hard carbon negative electrode material for sodium ion battery

Abstract

The application discloses a preparation method of a carbohydrate-based hard carbon negative material of a sodium ion battery, and comprises the following steps: S1, raw material pre-mixing: mixing a carbohydrate precursor, a stabilizer, a crosslinking agent, a defoaming agent, deionized water and ethanol to obtain a mixed solution; S2, spray drying: drying and treating the mixed solution by using spray drying to obtain a mixed precursor; S3, crosslinking reaction: stage-by-stage heat treatment of the mixed precursor to obtain a crosslinked precursor; S4, crushing and refining: crushing the crosslinked precursor to obtain a refined crosslinked precursor; S5, low-temperature sintering: low-temperature sintering of the crosslinked precursor in a protective atmosphere to obtain a pre-carbonized material; and S6, high-temperature sintering: high-temperature sintering of the pre-carbonized material in a protective atmosphere to obtain the hard carbon negative material of the sodium ion battery. The preparation method of the carbohydrate-based hard carbon negative material of the sodium ion battery has the characteristics of high sodium storage capacity, high product purity and green and environment-friendly process.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of sodium ion batteries, in particular to a preparation method of a carbohydrate-based hard carbon negative electrode material of a sodium ion battery. BACKGROUND

[0002] Compared with traditional lithium ion batteries, sodium ion batteries have outstanding advantages in safety performance, low-temperature performance, high-temperature performance, rate performance and the like, and are expected to partially replace lithium ion batteries in the fields of start-stop power supply, large-scale energy storage, household energy storage, low-speed two-wheeled vehicles and the like, and play an important role.

[0003] In the field of negative electrode materials of sodium ion batteries, hard carbon negative electrode materials are currently the first choice for industrialization, and the properties of hard carbon precursors play a decisive role in the structure and electrochemical performance of the finally formed hard carbon materials, so the selection of hard carbon precursors is the key to current industrialization.

[0004] At present, the commonly used hard carbon precursors of sodium ion batteries mainly include resin (polyfurfuryl alcohol, phenolic resin and the like), fossil (natural asphalt, petroleum asphalt, coal pitch, coal and the like) and biomass (coconut shell, walnut shell, lignin, carbohydrate and the like). Among them, the biomass precursor has the advantages of wide raw material source, low price and renewability, and is the layout direction of most negative electrode manufacturers at present.

[0005] In addition to the above advantages, the carbohydrate precursor in biomass (specifically including glucose, sucrose, cellulose, starch and the like) has the advantages of good consistency and low ash content, and does not need to use a large amount of acid liquid to reduce the ash content, so it is highly concerned.

[0006] However, the carbohydrate precursor in biomass will melt, foam and expand seriously and easily adhere to the equipment in the initial pyrolysis, resulting in difficult processing, high energy consumption and low yield. In addition, the carbohydrate component tends to form a structure with small interlayer spacing and large pore size in the high-temperature sintering process, resulting in poor electrochemical performance and low sodium storage capacity. SUMMARY

[0007] The purpose of the present application is to provide a preparation method of a carbohydrate-based hard carbon negative electrode material of a sodium ion battery, which has the characteristics of high sodium storage capacity, high product purity and green and environmentally friendly process.

[0008] The present application can be realized by the following technical solutions:

[0009] The present application discloses a preparation method of a carbohydrate-based hard carbon negative electrode material of a sodium ion battery, comprising the following steps:

[0010] S1, raw material pre-mixing: mixing a carbohydrate precursor, a stabilizer, a crosslinking agent, a defoaming agent, deionized water and ethanol to obtain a mixed solution;

[0011] S2, spray drying: using spray drying to dry the mixed solution obtained in step S1 to obtain a mixed precursor;

[0012] S3, cross-linking reaction: the mixed precursor obtained in step S2 is treated by staged heat treatment to obtain a cross-linked precursor;

[0013] S4, crushing and refining: the cross-linked precursor obtained in step S3 is crushed to obtain a refined cross-linked precursor;

[0014] S5, low-temperature sintering: the cross-linked precursor obtained in step S4 is subjected to low-temperature sintering in a protective atmosphere to obtain a pre-carbonized material;

[0015] S6: high-temperature sintering: the pre-carbonized material obtained in step S5 is subjected to high-temperature sintering in a protective atmosphere to obtain a sodium-ion battery hard carbon negative electrode material.

[0016] Further, in step S3, the first stage of the staged heat treatment has a treatment temperature of 120-160°C and a treatment time of 2-5h; the second stage has a treatment temperature of 150-250°C and a treatment time of 2-8h.

[0017] Specifically, the first stage of the treatment has a temperature lower than the decomposition temperature of the defoaming agent and higher than the decomposition temperature of the carbohydrate. In this process, the treatment temperature is higher than the melting point of the carbohydrate, but the morphology of the stabilizer remains basically unchanged at this temperature, so the molten carbohydrate is adsorbed on the surface of the stabilizer, and under the support of the stabilizer, the precursor does not melt and remains in good powder form. In this process, the carbohydrate decomposes in large quantities, producing a large amount of volatile gas, which, under the action of the defoaming agent, achieves the purpose of not foaming and not expanding. The second stage of the treatment has a temperature higher than the decomposition temperature of the defoaming agent and lower than the combustion temperature of the carbohydrate. In this process, the hydrogen bond network in the carbohydrate is destroyed under the action of oxygen, and a large number of active hydroxyl groups are released, which then undergo polycondensation with the hydroxyl groups in the cross-linking agent to form a cross-linked structure. In addition, the chemical bonds with poor thermal stability continue to break, producing a large amount of escaping gas, which forms a developed interconnected pore structure in the carbon material during the gas escape process.

[0018] Further, in step S1, the stabilizer is one or more of phenolic resin, epoxy resin, polyimide, polyfurfural alcohol, and lignin; the addition amount of the stabilizer is 1-10wt.% of the addition amount of the carbohydrate precursor; specifically, the stabilizer is a carbon-containing raw material rich in polycyclic aromatic hydrocarbons, which has good thermal stability and a high pyrolysis temperature, and its morphology remains basically unchanged at a certain temperature, so it can be used as a supporting agent to keep the morphology of the entire system unchanged.

[0019] Further, in step S1, the cross-linking agent is one or more of phosphoric acid, metaphosphoric acid, pyrophosphoric acid and sulfuric acid; the added amount of the cross-linking agent is 5-20 wt.% of the added amount of the carbohydrate precursor.

[0020] Further, in step S1, the defoaming agent is one or more of polyvinylpyrrolidone, polyethylene glycol, fatty alcohol polyoxyethylene ether, alkyl alcohol amide, fatty alcohol polyethylene glycol ester, fatty acid glyceride and polyhydric alcohol; the added amount of the defoaming agent is 0.5-3 wt.% of the added amount of the carbohydrate precursor.

[0021] Further, in step S1, the added amount of ethanol is 5-20 wt.% of the added amount of the carbohydrate precursor. Specifically, the purpose of adding ethanol is to improve the solubility of the stabilizer in the mixed solution. The added amount of ethanol will affect the effect of the present application: if the added amount of ethanol is too low, the stabilizer is not easy to uniformly disperse in the mixed solution; if the added amount of ethanol is too high, the carbohydrate and the cross-linking agent are not easy to dissolve in the mixed solution, resulting in that the structure of the synthesized hard carbon product is not uniform and the product consistency is poor.

[0022] Further, in step S6, the protective atmosphere is nitrogen and / or argon, the sintering temperature is 900-1600℃, and the sintering time is 2-6h. In this process, the pre-carbonized material is further high-temperature graphitized, and ordered carbon layers are gradually formed to form a developed internal pore structure wrapped by curved carbon layers.

[0023] Further, in step S2, the outlet air temperature of the spray drying is 110-150℃, and the inlet air temperature is 200-320℃. In the spray drying process, after the mixed solution is atomized, the water is rapidly vaporized in the contact process with hot air to obtain a dry sample. Due to the rapid evaporation speed of water, the mixed solution can still maintain the uniformity before drying.

[0024] Further, in step S1, the carbohydrate precursor is one or more of glucose, sucrose, fructose, galactose, starch, cellulose, curdlan, dextran, arabinan and xylose.

[0025] Further, in step S4, the crushing method is one or more of mechanical grinding, air flow powder, Raymond mill, ball mill and stirring mill, and the D50 of the crushed material is 3-10μm.

[0026] Further, in step S5, the protective atmosphere is nitrogen and / or argon, the sintering temperature is 400-800℃, and the sintering time is 1-5h.

[0027] The present application discloses a preparation method of a carbohydrate-based hard carbon negative electrode material for sodium ion batteries, which has the following beneficial effects:

[0028] First, high sodium storage capacity: the carbohydrate precursor forms a relatively stable cross-linked structure under the action of oxygen and cross-linking agent, and a developed interconnected pore structure is formed inside the cross-linked structure during gas escape, thereby improving the sodium storage capacity of the hard carbon material;

[0029] Second, high product purity: compared with other types of biomass-based hard carbon materials, the carbohydrate raw material has a definite and uniform chemical structure, and the impurity content is low, thereby effectively improving the purity of the material.

[0030] Third, green and environmentally friendly process: since the content of metal impurities in the raw material is very low, no additional pickling purification process is needed, and a large amount of acid solution is not needed, the process is simple and green and environmentally friendly. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solutions of the present application, the product of the present application will be further described in detail below in combination with embodiments.

[0032] The present application discloses a preparation method of a carbohydrate-based hard carbon negative material for sodium ion batteries, comprising the following steps:

[0033] S1, raw material pre-mixing: mixing a carbohydrate precursor, a stabilizer, a cross-linking agent, a defoaming agent, deionized water and ethanol to obtain a mixed solution;

[0034] S2, spray drying: using spray drying to dry process the mixed solution obtained in step S1 to obtain a mixed precursor;

[0035] S3, cross-linking reaction: the mixed precursor obtained in step S2 is heat treated in stages to obtain a cross-linked precursor;

[0036] S4, crushing and refining: the cross-linked precursor obtained in step S3 is crushed to obtain a refined cross-linked precursor;

[0037] S5, low-temperature sintering: the cross-linked precursor obtained in step S4 is subjected to low-temperature sintering under a protective atmosphere to obtain a pre-carbonized material;

[0038] S6, high-temperature sintering: the pre-carbonized material obtained in step S5 is subjected to high-temperature sintering under a protective atmosphere to obtain a hard carbon negative material for sodium ion batteries.

[0039] Further, in step S3, the first stage of the staged heat treatment has a treatment temperature of 120-160 DEG C and a treatment time of 2-5 h; the second stage has a treatment temperature of 150-250 DEG C and a treatment time of 2-8 h.

[0040] Further, in step S1, the stabilizer is one or two or more of phenol-formaldehyde resin, epoxy resin, polyimide, polyfurfuryl alcohol, and lignin; the amount of the stabilizer added is 1-10 wt.% of the amount of the carbohydrate precursor added.

[0041] Further, in step S1, the crosslinking agent is one or two or more of phosphoric acid, metaphosphoric acid, pyrophosphoric acid, and sulfuric acid; the amount of the crosslinking agent added is 5-20 wt.% of the amount of the carbohydrate precursor added.

[0042] Further, in step S1, the defoaming agent is one or two or more of polyvinylpyrrolidone, polyethylene glycol, fatty alcohol polyoxyethylene ether, alkylolamide, fatty alcohol polyglycol ester, fatty acid glyceride, and polyol; the amount of the defoaming agent added is 0.5-3 wt.% of the amount of the carbohydrate precursor added.

[0043] Further, in step S1, the amount of ethanol added is 5-20 wt.% of the amount of the carbohydrate precursor added.

[0044] Further, in step S6, the protective atmosphere is nitrogen and / or argon, the sintering temperature is 900-1600°C, and the sintering time is 2-6 h.

[0045] Further, in step S2, the outlet air temperature of the spray drying is 110-150°C, and the inlet air temperature is 200-320°C.

[0046] Further, in step S1, the carbohydrate precursor is one or two or more of glucose, sucrose, fructose, galactose, starch, cellulose, curdlan, dextran, arabinan, and xylose.

[0047] Further, in step S4, the crushing method is one or two or more of mechanical milling, jet milling, Raymond milling, ball milling, and stirring milling, and the D50 of the crushed material is 3-10 μm.

[0048] Further, in step S5, the protective atmosphere is nitrogen and / or argon, the sintering temperature is 400-800°C, and the sintering time is 1-5 h.

[0049] Example 1

[0050] This example relates to a method for preparing a carbohydrate-based sodium-ion battery hard carbon negative electrode material, comprising the following steps:

[0051] S1, raw material pre-mixing: mixing carbohydrate precursor, stabilizer, crosslinking agent, defoaming agent, deionized water and ethanol to obtain a mixed solution. Specifically, the carbohydrate precursor is dextran, arabinan, and xylose; the stabilizer is polyfurfuryl alcohol and lignin, and the addition amount of the stabilizer is 5 wt.% of the addition amount of the carbohydrate precursor; the crosslinking agent is metaphosphoric acid, pyrophosphoric acid and sulfuric acid, and the addition amount of the crosslinking agent is 5 wt.% of the addition amount of the carbohydrate precursor; the defoaming agent is polyvinylpyrrolidone and polyethylene glycol, and the addition amount of the defoaming agent is 3 wt.% of the addition amount of the carbohydrate precursor; and the addition amount of ethanol is 10 wt.% of the addition amount of the carbohydrate precursor.

[0052] S2, spray drying: using spray drying to dry process the mixed solution obtained in step S1 to obtain a mixed precursor. Specifically, the outlet air temperature of spray drying is 130℃, and the inlet air temperature is 200℃.

[0053] S3, crosslinking reaction: the mixed precursor obtained in step S2 is subjected to staged heat treatment to obtain a crosslinked precursor. Specifically, the first stage of the staged heat treatment has a treatment temperature of 140℃ and a treatment time of 2h; the second stage has a treatment temperature of 250℃ and a treatment time of 5h.

[0054] S4, crushing and refining: the crosslinked precursor obtained in step S3 is crushed to obtain a refined crosslinked precursor. Specifically, the crushing method is ball milling or stirring milling, and the material is pulverized to a D50 of 3-10μm.

[0055] S5, low-temperature sintering: the crosslinked precursor obtained in step S4 is subjected to low-temperature sintering in a protective atmosphere to obtain a pre-carbonized material. Specifically, the protective atmosphere is nitrogen, the sintering temperature is 600℃, and the sintering time is 1h.

[0056] S6, high-temperature sintering: the pre-carbonized material obtained in step S5 is subjected to high-temperature sintering in a protective atmosphere to obtain a sodium-ion battery hard carbon negative electrode material. Specifically, the protective atmosphere is argon, the sintering temperature is 1200℃, and the sintering time is 2h.

[0057] Example 2

[0058] This example relates to a method for preparing a carbohydrate-based sodium-ion battery hard carbon negative electrode material, comprising the following steps:

[0059] S1, raw material pre-mixing: mixing carbohydrate precursor, stabilizer, crosslinking agent, defoaming agent, deionized water and ethanol to obtain a mixed solution. Specifically, the carbohydrate precursor is galactose, starch, cellulose, curdlan, dextran, arabinose, xylose; the stabilizer is phenolic resin, polyimide, polyfurfuryl alcohol, lignin, and the addition amount of the stabilizer is 1 wt.% of the addition amount of the carbohydrate precursor; the crosslinking agent is pyrophosphoric acid and sulfuric acid, and the addition amount of the crosslinking agent is 20 wt.% of the addition amount of the carbohydrate precursor; the defoaming agent is polyvinylpyrrolidone, polyethylene glycol, fatty acid glyceride, polyol, and the addition amount of the defoaming agent is 2 wt.% of the addition amount of the carbohydrate precursor; the addition amount of ethanol is 5 wt.% of the addition amount of the carbohydrate precursor.

[0060] S2, spray drying: using spray drying to dry process the mixed solution obtained in step S1 to obtain a mixed precursor. Specifically, the outlet air temperature of spray drying is 110°C, and the inlet air temperature is 320°C.

[0061] S3, crosslinking reaction: the mixed precursor obtained in step S2 is subjected to staged heat treatment to obtain a crosslinked precursor. Specifically, the first stage of the staged heat treatment has a treatment temperature of 120°C and a treatment time of 5h; the second stage has a treatment temperature of 200°C and a treatment time of 2h.

[0062] S4, crushing and refining: the crosslinked precursor obtained in step S3 is crushed to obtain a refined crosslinked precursor. Specifically, the crushing method is ball milling, and the material is pulverized to a D50 of 3-10μm.

[0063] S5, low-temperature sintering: the crosslinked precursor obtained in step S4 is subjected to low-temperature sintering in a protective atmosphere to obtain a pre-carbonized material. Specifically, the protective atmosphere is argon or nitrogen, the sintering temperature is 400°C, and the sintering time is 5h.

[0064] S6, high-temperature sintering: the pre-carbonized material obtained in step S5 is subjected to high-temperature sintering in a protective atmosphere to obtain a sodium ion battery hard carbon negative electrode material. Specifically, the protective atmosphere is nitrogen, the sintering temperature is 900°C, and the sintering time is 6h.

[0065] Example 3

[0066] This example relates to a method for preparing a carbohydrate-based sodium ion battery hard carbon negative electrode material, comprising the following steps:

[0067] S1, raw material pre-mixing: mixing carbohydrate precursor, stabilizer, crosslinking agent, defoaming agent, deionized water and ethanol to obtain a mixed solution. Specifically, the carbohydrate precursor is glucose, sucrose, fructose, galactose, starch, cellulose, curdlan; the stabilizer is phenolic resin, epoxy resin, polyimide, and the addition amount of the stabilizer is 8 wt.% of the addition amount of the carbohydrate precursor; the crosslinking agent is phosphoric acid, metaphosphoric acid, pyrophosphoric acid, and the addition amount of the crosslinking agent is 12 wt.% of the addition amount of the carbohydrate precursor; the defoaming agent is polyvinylpyrrolidone, polyethylene glycol, fatty alcohol polyoxyethylene ether, and the addition amount of the defoaming agent is 1 wt.% of the addition amount of the carbohydrate precursor; the addition amount of ethanol is 8 wt.% of the addition amount of the carbohydrate precursor.

[0068] S2, spray drying: using spray drying to dry process the mixed solution obtained in step S1 to obtain a mixed precursor. Specifically, the outlet air temperature of spray drying is 120℃, and the inlet air temperature is 260℃.

[0069] S3, crosslinking reaction: the mixed precursor obtained in step S2 is subjected to staged heat treatment to obtain a crosslinked precursor. Specifically, the first stage of the staged heat treatment has a treatment temperature of 130℃ and a treatment time of 4h; the second stage has a treatment temperature of 180℃ and a treatment time of 4h.

[0070] S4, crushing and refining: the crosslinked precursor obtained in step S3 is crushed to obtain a refined crosslinked precursor. Specifically, the crushing method is mechanical grinding or air flow powder, and the material is crushed to a D50 of 3-10μm.

[0071] S5, low-temperature sintering: the crosslinked precursor obtained in step S4 is subjected to low-temperature sintering in a protective atmosphere to obtain a pre-carbonized material. Specifically, the protective atmosphere is nitrogen and argon, the sintering temperature is 500℃, and the sintering time is 4h.

[0072] S6, high-temperature sintering: the pre-carbonized material obtained in step S5 is subjected to high-temperature sintering in a protective atmosphere to obtain a sodium ion battery hard carbon negative electrode material. Specifically, the protective atmosphere is nitrogen and argon, the sintering temperature is 1200℃, and the sintering time is 3h.

[0073] Example 4

[0074] This example relates to a method for preparing a carbohydrate-based sodium ion battery hard carbon negative electrode material, comprising the following steps:

[0075] S1, raw material pre-mixing: mixing carbohydrate precursor, stabilizer, crosslinking agent, defoaming agent, deionized water and ethanol to obtain a mixed solution. Specifically, the carbohydrate precursor is glucose, sucrose, fructose, galactose, starch, cellulose, curdlan, dextran, arabinan, xylose; the stabilizer is phenolic resin, epoxy resin, polyimide, polyfurfuryl alcohol, lignin, the addition amount of the stabilizer is 3wt.% of the addition amount of the carbohydrate precursor; the crosslinking agent is phosphoric acid, metaphosphoric acid, pyrophosphoric acid and sulfuric acid, the addition amount of the crosslinking agent is 14wt.% of the addition amount of the carbohydrate precursor; the defoaming agent is polyvinylpyrrolidone, polyethylene glycol, fatty alcohol polyoxyethylene ether, alkyl alcohol amide, fatty alcohol polyethylene glycol ester, fatty acid glyceride, polyol, the addition amount of the defoaming agent is 2wt.% of the addition amount of the carbohydrate precursor; the addition amount of ethanol is 15wt.% of the addition amount of the carbohydrate precursor.

[0076] S2, spray drying: using spray drying to dry process the mixed solution obtained in step S1 to obtain a mixed precursor. Specifically, the outlet air temperature of spray drying is 140℃, and the inlet air temperature is 230℃.

[0077] S3, crosslinking reaction: the mixed precursor obtained in step S2 is treated by staged heat treatment to obtain a crosslinked precursor. Specifically, the first stage treatment temperature of the staged heat treatment is 150℃, and the treatment time is 3h; the second stage treatment temperature is 180℃, and the treatment time is 7h.

[0078] S4, crushing and refining: the crosslinked precursor obtained in step S3 is crushed to obtain a refined crosslinked precursor. Specifically, the crushing method is mechanical grinding or air flow powder, and the material is crushed to D50 of 3-10μm.

[0079] S5, low-temperature sintering: the crosslinked precursor obtained in step S4 is subjected to low-temperature sintering in a protective atmosphere to obtain a pre-carbonized material. Specifically, the protective atmosphere is nitrogen and argon, the sintering temperature is 700℃, and the sintering time is 2h.

[0080] S6, high-temperature sintering: the pre-carbonized material obtained in step S5 is subjected to high-temperature sintering in a protective atmosphere to obtain a sodium ion battery hard carbon negative electrode material. Specifically, the protective atmosphere is nitrogen and argon, the sintering temperature is 1500℃, and the sintering time is 4h.

[0081] Example 5

[0082] This example relates to a preparation method of a carbohydrate-based sodium ion battery hard carbon negative electrode material, comprising the following steps:

[0083] S1, raw material premixing: mixing carbohydrate precursor, stabilizer, crosslinking agent, defoaming agent, deionized water and ethanol to obtain a mixed solution. Specifically, the carbohydrate precursor is glucose, sucrose, fructose, galactose; the stabilizer is phenolic resin, epoxy resin, the addition amount of the stabilizer is 10 wt.% of the addition amount of the carbohydrate precursor; the crosslinking agent is phosphoric acid, metaphosphoric acid, the addition amount of the crosslinking agent is 12 wt.% of the addition amount of the carbohydrate precursor; the defoaming agent is polyvinylpyrrolidone, polyethylene glycol, the addition amount of the defoaming agent is 0.5 wt.% of the addition amount of the carbohydrate precursor; the addition amount of ethanol is 20 wt.% of the addition amount of the carbohydrate precursor.

[0084] S2, spray drying: using spray drying to dry process the mixed solution obtained in step S1 to obtain a mixed precursor. Specifically, the outlet air temperature of spray drying is 150℃, and the inlet air temperature is 260℃.

[0085] S3, crosslinking reaction: the mixed precursor obtained in step S2 is treated by staged heat treatment to obtain a crosslinked precursor. Specifically, the first stage treatment temperature of the staged heat treatment is 160℃, and the treatment time is 3h; the second stage treatment temperature is 150℃, and the treatment time is 8h.

[0086] S4, crushing and refining: the crosslinked precursor obtained in step S3 is crushed to obtain a refined crosslinked precursor. Specifically, the crushing method is mechanical grinding and air flow powder, and the powder is crushed to D50 of 3-10μm.

[0087] S5, low temperature sintering: the crosslinked precursor obtained in step S4 is sintered at low temperature in a protective atmosphere to obtain a pre-carbonized material. Specifically, the protective atmosphere is nitrogen and argon, the sintering temperature is 800℃, and the sintering time is 3h.

[0088] S6, high temperature sintering: the pre-carbonized material obtained in step S5 is sintered at high temperature in a protective atmosphere to obtain a sodium ion battery hard carbon negative electrode material. Specifically, the protective atmosphere is nitrogen and argon, the sintering temperature is 1600℃, and the sintering time is 4h.

[0089] Application Example 1

[0090] This example relates to a carbohydrate-based sodium ion battery hard carbon negative electrode material, and a preparation method thereof includes the following steps:

[0091] S1, raw material premixing: mixing starch precursor, lignin, phosphoric acid, polyvinylpyrrolidone, deionized water and ethanol to obtain a mixed solution. Among them, the addition amounts of lignin, phosphoric acid, polyvinylpyrrolidone and ethanol are 2.3, 6.0, 1.0 and 15 wt.% of the addition amount of starch, respectively.

[0092] S2, spray drying: the mixed solution obtained in step S1 is dried by spray drying to obtain a mixed precursor, wherein the outlet temperature of the spray drying is 120°C, and the inlet temperature is 280°C.

[0093] S3, cross-linking reaction: the mixed precursor obtained in step S2 is subjected to two-stage heat treatment in an air atmosphere to obtain a cross-linked precursor. The first-stage treatment temperature is 130°C, and the treatment time is 3h; the second-stage treatment temperature is 220°C, and the treatment time is 2.5h.

[0094] S4, crushing and refining: the cross-linked precursor obtained in step S3 is crushed by using a mechanical mill and an air flow mill in sequence to obtain a cross-linked precursor with a D50 of 8μm.

[0095] S5, low-temperature sintering: the cross-linked precursor obtained in step S4 is subjected to low-temperature sintering in a nitrogen atmosphere, the sintering temperature is 600°C, and the sintering time is 2h, to obtain a pre-carbonized material.

[0096] S6, high-temperature sintering: the pre-carbonized material obtained in step S5 is subjected to high-temperature sintering in a nitrogen atmosphere, the sintering temperature is 1300°C, and the sintering time is 5h, to obtain the hard carbon negative electrode material of application example 1.

[0097] Comparative example 1

[0098] This example relates to a carbohydrate-based sodium ion battery hard carbon negative electrode material, and a preparation method thereof includes the following steps:

[0099] S1, raw material pre-mixing: starch precursor, deionized water and ethanol are mixed to obtain a mixed solution. The addition amount of phosphoric acid and ethanol is 6.0 and 15wt.% of the addition amount of starch, respectively.

[0100] S2, spray drying: the mixed solution obtained in step S1 is dried by spray drying to obtain a mixed precursor, wherein the outlet temperature of the spray drying is 120°C, and the inlet temperature is 280°C.

[0101] S3, cross-linking reaction: the mixed precursor obtained in step S2 is subjected to two-stage heat treatment in an air atmosphere to obtain a cross-linked precursor. The first-stage treatment temperature is 130°C, and the treatment time is 3h; the second-stage treatment temperature is 220°C, and the treatment time is 2.5h.

[0102] S4, crushing and refining: the cross-linked precursor obtained in step S3 is crushed by using a mechanical mill and an air flow mill in sequence to obtain a cross-linked precursor with a D50 of 8μm.

[0103] S5, low-temperature sintering: the cross-linked precursor obtained in step S4 is subjected to low-temperature sintering in a nitrogen atmosphere, the sintering temperature is 600°C, and the sintering time is 2h, to obtain a pre-carbonized material.

[0104] S6: High-temperature sintering: the pre-carbonized material obtained in step S5 is subjected to high-temperature sintering under a nitrogen atmosphere, the sintering temperature is 1300°C, and the sintering time is 5h, to obtain the hard carbon negative electrode material of Comparative Example 1.

[0105] Comparative Example 2

[0106] The present embodiment relates to a carbohydrate-based sodium-ion battery hard carbon negative electrode material, and a preparation method thereof, which comprises the following steps:

[0107] S1, raw material pre-mixing: starch precursor, lignin, polyvinylpyrrolidone, deionized water and ethanol are mixed to obtain a mixed solution. The addition amounts of lignin, polyvinylpyrrolidone and ethanol are 2.3, 1.0 and 15wt.% of the addition amount of starch, respectively.

[0108] S2, spray drying: the mixed solution obtained in step S1 is subjected to drying treatment by spray drying to obtain a mixed precursor, wherein the outlet air temperature of the spray drying is 120°C, and the inlet air temperature is 280°C.

[0109] S3, cross-linking reaction: the mixed precursor obtained in step S2 is subjected to two-stage heat treatment in an air atmosphere to obtain a cross-linked precursor. The first-stage treatment temperature is 130°C, and the treatment time is 3h; the second-stage treatment temperature is 220°C, and the treatment time is 2.5h.

[0110] S4, crushing: the cross-linked precursor obtained in step S3 is crushed by using a mechanical mill and an air flow mill in sequence to obtain a cross-linked precursor with a D50 of 8μm.

[0111] S5, low-temperature sintering: the cross-linked precursor obtained in step S4 is subjected to low-temperature sintering under a nitrogen atmosphere, the sintering temperature is 600°C, and the sintering time is 2h, to obtain a pre-carbonized material.

[0112] S6, high-temperature sintering: the pre-carbonized material obtained in step S5 is subjected to high-temperature sintering under a nitrogen atmosphere, the sintering temperature is 1300°C, and the sintering time is 5h, to obtain the hard carbon negative electrode material of Comparative Example 2.

[0113] In the S3 step of Application Example 1 and Comparative Example 2, the mixed precursor maintains a good powdery morphology during heat treatment and does not melt or foam. In the S3 step of Comparative Example 2, the mixed precursor melts and foams during pyrolysis, and expands severely. The comparison results show that the supporting agent and the defoaming agent can significantly improve the melting and foaming phenomena and improve the processability of the material.

[0114] In order to effectively evaluate the technical effects of the present application, Application Example 1 and Comparative Examples 1-2 are tested as follows:

[0115] The constant current charge-discharge test measured the first week charge specific capacity of application example 1, comparative example 1 and comparative example 2 to be 364, 312 and 282 mAh / g, respectively. The first week charge specific capacity of application example 1 was significantly improved, which was attributed to the fact that the hydrogen bond network in the carbohydrate was destroyed under the action of oxygen during the crosslinking reaction, and a large number of active hydroxyl groups were released, which then reacted with the hydroxyl groups in the crosslinking agent to form a crosslinked structure. In addition, the chemical bonds with poor thermal stability continued to break, producing a large amount of escape gas, and a developed interconnected pore structure was formed inside the crosslinked structure during the gas escape process. During the subsequent high-temperature sintering process, an ordered carbon layer was gradually formed, which wrapped the pore structure, forming a developed internal pore structure, thereby improving the sodium storage capacity of the hard carbon material.

[0116] The above examples are merely specific embodiments of the present application, which are described in detail and specifically, but should not be construed as limiting the scope of the patent of the present application. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, and these obvious alternative forms all belong to the protection scope of the present application.

Claims

1. A method for preparing a carbohydrate-based sodium-ion battery hard carbon anode material, characterized in that... Includes the following steps: S1. Raw material premixing: A mixture is prepared by mixing a carbohydrate precursor, stabilizer, crosslinking agent, defoamer, deionized water, and ethanol. The stabilizer is one or more of phenolic resin, epoxy resin, polyimide, polyfurfuryl alcohol, and lignin; the amount of stabilizer added is 1-10 wt.% of the amount of carbohydrate precursor added. The crosslinking agent is one or more of phosphoric acid, metaphosphoric acid, pyrophosphoric acid, and sulfuric acid; the amount of crosslinking agent added is 5-20 wt.% of the amount of carbohydrate precursor added. The defoamer is one or more of polyvinylpyrrolidone, polyethylene glycol, fatty alcohol polyoxyethylene ether, alkylolamide, fatty alcohol polyethylene glycol ester, fatty acid glycerol ester, and polyol; the amount of defoamer added is 0.5-3 wt.% of the amount of carbohydrate precursor added. S2. Spray drying: The mixture obtained in step S1 is dried by spray drying to obtain the mixed precursor; S3. Crosslinking reaction: The mixed precursor obtained in step S2 is subjected to staged heat treatment to obtain a crosslinked precursor; the first stage of the staged heat treatment is at a temperature of 120-160℃ and a treatment time of 2-5h; the second stage is at a temperature of 150-250℃ and a treatment time of 2-8h. S4. Crushing and refining: The crosslinking precursor obtained in step S3 is crushed to obtain a refined crosslinking precursor. S5. Low-temperature sintering: The crosslinked precursor obtained in step S4 is sintered at low temperature under a protective atmosphere to obtain a pre-carbonized material. S6: High-temperature sintering: The pre-carbonized material obtained in step S5 is sintered at high temperature under a protective atmosphere to obtain a hard carbon anode material for sodium-ion batteries.

2. The method for preparing the carbohydrate-based sodium-ion battery hard carbon anode material according to claim 1, characterized in that: In step S1, the amount of ethanol added is 5-20 wt. of the amount of carbohydrate precursor added.

3. The method for preparing the carbohydrate-based sodium-ion battery hard carbon anode material according to claim 1, characterized in that: In step S6, the protective atmosphere is nitrogen and / or argon, the sintering temperature is 900-1600℃, and the sintering time is 2-6h.

4. The method for preparing the carbohydrate-based sodium-ion battery hard carbon anode material according to claim 1, characterized in that: In step S2, the outlet air temperature of the spray dryer is 110-150℃, and the inlet air temperature is 200-320℃.

5. The method for preparing the carbohydrate-based sodium-ion battery hard carbon anode material according to claim 1, characterized in that: In step S1, the carbohydrate precursor is one or more of glucose, sucrose, fructose, galactose, starch, cellulose, gelatin, dextran, arabinogalactan, and xylose.

6. The method for preparing the carbohydrate-based sodium-ion battery hard carbon anode material according to claim 1, characterized in that: In step S4, the crushing method is one or more of mechanical milling, air jet milling, Raymond milling, ball milling, and stirred milling, and the material is crushed to a D50 of 3-10μm; In step S5, the protective atmosphere is nitrogen and / or argon, the sintering temperature is 400-800℃, and the sintering time is 1-5h.