Mechanical surface-modified biomass hard carbon material and preparation method and application thereof

Abstract

The application discloses a mechanical surface modification biomass hard carbon material and a preparation method and application thereof. The method comprises the following steps: drying a biomass raw material, and then putting the biomass raw material into a ball milling tank to perform high-pressure ball milling to obtain a precursor; and performing multi-section continuous carbonization and crushing on the precursor to obtain the biomass hard carbon material. The atmosphere of the high-pressure ball milling is single or mixed. The method has the advantages of wide raw material source, low cost, simple process and the like, does not need chemical reagents, and does not produce secondary pollution. The hard carbon material has rich surface functional groups and suitable interlayer spacing while ensuring high closed porosity of the material by adjusting the carbon chain structure and surface modification, and effectively solves the problems of low embedding and disembedding efficiency of sodium ions of the hard carbon material and easy formation of dendrites. Based on the hard carbon material, a sodium ion battery is prepared, and the sodium ion battery has excellent electrochemical performance, and can effectively improve the capacity and first circle coulomb efficiency of the sodium ion battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrode materials, and particularly relates to a preparation method of a biomass-based hard carbon negative electrode material for a sodium ion battery. BACKGROUND

[0002] In recent years, with the large-scale application of renewable energy, developing safe and reliable energy storage devices is of great significance to solve the intermittency and instability of renewable energy and realize the sustainable output of energy. Lithium ion batteries, as an important energy storage device, have been successfully applied in many fields. However, the limited reserves and uneven distribution of lithium resources and the high cost make it difficult to meet the application demand in the future. Sodium ion batteries have entered the researchers' field of vision again. The energy storage mechanism of sodium ion batteries is similar to that of lithium ion batteries, and sodium reserves are abundant and the cost is low. Therefore, developing a negative electrode material with high capacity, excellent rate performance and long service life is the key to the industrialization of sodium ion batteries.

[0003] Among the many materials used as negative electrodes of sodium ion batteries, carbon-based negative electrode materials synthesized from abundant, low-cost and renewable biomass have been widely studied. Biomass waste has the characteristics of wide source, sustainable regeneration, low pollution and low price. Preparing carbon materials from them can not only save costs, but also alleviate environmental pollution caused by a large amount of waste incineration. Secondly, biomass materials form special texture structure and texture characteristics during growth, and can still maintain the original microstructure after carbonization. The rich closed pore structure formed during heat treatment has excellent sodium storage performance and is expected to become the most potential new low-cost high-performance negative electrode material for sodium ion batteries.

[0004] For the prior art, there are still many problems in preparing hard carbon from biomass. Since biomass materials contain rich impurity elements in addition to carbon chains, the pretreatment process and carbonization process of the raw materials need to be strictly controlled, otherwise the pore structure will be complex and cannot adapt to the embedding and extraction of sodium ions. Chinese patent (CN115064667A) discloses a biomass hard carbon based on low crystalline cellulose content and its preparation method and application. The biomass is pretreated by acidolysis and alkaline hydrolysis, and then carbonized and pyrolyzed in an inert atmosphere to obtain the hard carbon. The high-closed-pore hard carbon is obtained by solution pretreatment and high-temperature carbonization, and the hard carbon material is used as a negative electrode material for sodium ion batteries, which effectively improves the capacity and rate performance of the battery. However, there are still problems such as low specific discharge capacity and poor first-cycle coulombic efficiency in the patent, which cannot meet the industrial application. SUMMARY

[0005] In view of the problems existing in the prior art, a first object of the present application is to provide a mechanical surface modified biomass hard carbon material. The hard carbon material uses biomass as a raw material, adjusts the carbon chain structure and surface modification, ensures high closed porosity of the material, and has abundant surface functional groups and suitable interlayer spacing, effectively solving the problems of low sodium ion embedding and disembedding efficiency of the hard carbon material and easy formation of dendrites. The capacity of the sodium ion battery hard carbon negative material is not high, and the first circle coulombic efficiency is low.

[0006] A second object of the present application is to provide a preparation method of the mechanical surface modified biomass hard carbon material. The method uses biomass as a carbon source, first dries the biomass, introduces a certain pressure of non-air atmosphere into a sealed ball mill tank, and simultaneously performs ball milling treatment on the raw material, then pyrolyzes under an inert gas atmosphere to obtain a hard carbon with abundant closed pore structure and suitable interlayer spacing. The method is simple, low in cost, does not introduce chemical reagents in the treatment process, is friendly to the environment, and does not produce secondary pollution.

[0007] A third object of the present application is to provide an application of the mechanical surface modified biomass hard carbon material. Based on the special physicochemical properties of the biomass hard carbon material provided by the present application, the sodium ion battery negative electrode prepared by using the material has excellent electrochemical performance, and the first circle coulombic efficiency is above 90%, and the first circle charge specific capacity is 315.17 mAh / g.

[0008] To achieve the above technical purposes, the present application provides a preparation method of a mechanical surface modified biomass hard carbon material. The biomass raw material is dried and then put into a ball mill tank for high-pressure ball milling to obtain a precursor. The precursor is subjected to multi-stage continuous carbonization and crushing to obtain the mechanical surface modified biomass hard carbon material. The atmosphere of the high-pressure ball milling is single or mixed.

[0009] The preparation method adopted by the present application is based on the synergistic effect between the steps, and under the premise of ensuring the skeleton structure of the biomass raw material unchanged, a hard carbon material with high closed porosity and low specific surface area is obtained. The high-pressure ball milling not only can make the biomass raw material more uniform, but also can modify the surface of the raw material and adjust the interlayer spacing in the subsequent carbonization process, further adapting the embedding and disembedding of sodium ions.

[0010] The high-pressure ball milling atmosphere used in the present application is one of the surface modified raw materials. The molecular chains of the biomass raw material are broken during the ball milling process. The mechanical energy of the ball milling is partially converted into the surface activation energy of the material, which promotes the surface oxygen functional group grafting or heteroatom doping of the biomass raw material. These abundant surface structures are mainly concentrated in the cross section of the biomass material. On the one hand, it helps to improve the closed porosity of the material, and on the other hand, it can well adjust the interlayer spacing of the carbon layer formed after carbonization of the material, thereby greatly improving the electrochemical performance of the hard carbon.

[0011] As a preferred scheme, the biomass raw material is various plant organisms naturally synthesized by air, water and soil.

[0012] As a preferred scheme, the atmosphere of the high-pressure ball milling is at least one of CO2, NH3 and O2. The addition of CO2 can perform carboxylation modification on the free radicals formed at the fracture of the biomass macromolecules, thereby forming C=O bonds; the addition of O2 can incorporate active oxygen atoms on the surface and fracture of the biomass macromolecules, and further form oxygen-containing functional groups on the surface of the material; and the addition of NH3 can complete nitrogen doping during the ball milling process, and build defect sites. The incorporation of oxygen-containing functional groups and heteroatoms can improve the interlayer spacing and closed pore structure of the hard carbon material, and finally optimize its performance as a battery negative electrode.

[0013] As a preferred scheme, the biomass raw material is one of starch, bamboo, wood, peanut shell and wheat shell.

[0014] As a preferred scheme, the drying condition is that the temperature is 70-80℃, and the time is 2-3h.

[0015] As a preferred scheme, the high-pressure ball milling is dry-based ball milling, and the conditions are that the rotation speed is 100-1000rpm, the time is 12-48h, the ball-to-material ratio is 1:0.05-20, and the pressure is 0.1-0.7MPa. Further preferably, the conditions of the high-pressure ball milling are that the rotation speed is 400-600rpm, the time is 36-48h, the ball-to-material ratio is 1:3-10, and the pressure is 0.3-0.6MPa.

[0016] The high-pressure ball milling process parameters provided by the application are strictly executed according to the above requirements. If the pressure is too low, the reaction threshold of gas molecules and biomass may not be reached, affecting the performance of the final material. If the time is too short, the reaction of gas molecules and biomass is not sufficient, and oxygen-containing functional groups and heteroatoms cannot be fully incorporated.

[0017] As a preferred scheme, the multi-stage continuous carbonization includes a pre-carbonization stage and a high-temperature carbonization stage, and after the carbonization is completed, the furnace is cooled to room temperature. Further, the carbonization process is completed in a tube furnace or an atmosphere furnace, and the heating rate is 2-5℃ / min.

[0018] As a preferred scheme, the pre-carbonization condition is that the temperature is 200-600℃, and the treatment time is 2-3h.

[0019] As a preferred scheme, the high-temperature carbonization condition is that the temperature is 1000-1700℃, and the carbonization time is 2-5h.

[0020] As a preferred scheme, the ball milling medium and the tank body of the high-pressure ball milling are one of agate, zirconia and stainless steel.

[0021] The application further provides a detailed preparation method of the mechanical surface modified biomass hard carbon material, comprising the following steps:

[0022] Step 1, drying, the biomass raw material is placed in a forced air oven for drying to remove water, the drying temperature is 70-80 DEG C, and the drying time is 2-3 h;

[0023] Step 2, ball milling treatment, the biomass raw material obtained after step 1 is added into a ball milling tank together with a ball milling medium in a ball-to-material ratio of 1:(0.05-20), a non-air atmosphere is introduced to reach a pressure of 0.1-0.7 MPa, and the ball milling treatment is carried out at a rotating speed of 100-1000 rpm for 12-48 h; after the ball milling, the material and the ball milling medium are separated through a screen to obtain a ball-milled material.

[0024] Step 3, carbonization, the carbonization process mainly comprises pre-carbonization and high-temperature carbonization; the sample obtained after step 2 is placed in a tube furnace, an inert gas is introduced for protection, the pre-carbonization temperature is 200-600 DEG C, and the treatment time is 2-3 h; the high-temperature carbonization temperature is 1000-1700 DEG C, the carbonization time is 2-5 h, and the heating rate is 2-5 DEG C / min; the sample is cooled to room temperature to obtain the ball-milled biomass hard carbon negative electrode material.

[0025] The application further provides a mechanical surface modified biomass hard carbon material, which is prepared by the preparation method in any one of the above. 2 / g.

[0026] The application further provides an application of the mechanical surface modified biomass hard carbon material, and the hard carbon is used as a battery negative electrode material to prepare a sodium ion battery.

[0027] Compared with the prior art, the application has the beneficial technical effects that:

[0028] 1) The biomass hard carbon material provided by the application uses biomass as a raw material, adjusts the carbon chain structure and surface modification, has rich surface functional groups and suitable interlayer spacing while ensuring high closed porosity, effectively solves the problems of low embedding and extraction efficiency of sodium ions and easy formation of dendrites of the hard carbon material, and mainly overcomes the problems of low capacity and low first circle coulomb efficiency of the sodium ion battery hard carbon negative electrode material in the prior art.

[0029] 2) The preparation method of the biomass hard carbon material provided by the application, wherein biomass is used as a carbon source, first dried, and then subjected to ball milling treatment in a sealed ball milling tank with a certain pressure of non-air atmosphere and raw materials at the same time, followed by pyrolysis under inert gas atmosphere, to obtain hard carbon with rich closed pore structure and suitable interlayer spacing. The method has the advantages of wide raw material sources, low cost, simple process, etc., is suitable for large-scale industrial production, and has less use of chemical reagents in the ball milling process, does not produce secondary pollution, and is more friendly to the environment.

[0030] 3) In the technical scheme provided by the application, the cellulose and other high molecular substances in the biomass will be broken due to the action of shearing force in the ball milling process, and the free radicals at the broken ends of the high molecular substances can react with the chemical substances simultaneously added into the ball milling tank. According to the different atmospheres added, oxygen-containing functional groups or atomic doping can be doped in the precursor. These doped oxygen-containing functional groups and atoms can act as pinning sites to promote the formation of closed pore structure in the carbonization process, and the doping of heteroatoms can adjust the interlayer spacing of the hard carbon material. The rich closed pore structure and suitable interlayer spacing are beneficial to the embedding and separation of ions in the battery charging and discharging process, thereby improving the electrochemical performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a flowchart of the application;

[0032] Figure 2 is the first circle charge-discharge curve of the battery prepared in the comparative example 1 of the application;

[0033] Figure 3 is the first circle charge-discharge curve of the battery prepared in the comparative example 2 of the application;

[0034] Figure 4 is the first circle charge-discharge curve of the battery prepared in the example 1 of the application;

[0035] Figure 5 is the first circle charge-discharge curve of the battery prepared in the example 2 of the application;

[0036] Figure 6 is the first circle charge-discharge curve of the battery prepared in the example 3 of the application;

[0037] Figure 7 is the first circle charge-discharge curve of the battery prepared in the example 4 of the application;

[0038] Figure 8 is the first circle charge-discharge curve of the battery prepared in the example 5 of the application;

[0039] Figure 9 is the first circle charge-discharge curve of the battery prepared in the example 6 of the application;

[0040] Figure 10 is the first circle charge-discharge curve of the battery prepared in Example 7 of the present application;

[0041] Figure 11 is the first circle charge-discharge curve of the battery prepared in Example 8 of the present application. Specific implementation method

[0042] The present application is further explained in conjunction with actual implementation, but not limited to the present application.

[0043] Comparative Example 1

[0044] The present application provides a preparation method of a biomass-based hard carbon negative electrode material for a sodium ion battery, and the steps thereof include:

[0045] Step 1, drying, 10g of peanut shell powder is placed in a forced air drying oven, the drying temperature is 80℃, and the drying time is 2h, and the water is removed by drying;

[0046] Step 2, carbonization, the peanut shell powder obtained after step 1 is placed in a tube furnace, and heated to 400℃ at a heating rate of 2℃ / min under argon atmosphere, pre-carbonization for 3h, and then heated to 1300℃ at a heating rate of 2℃ / min after cooling to room temperature, high-temperature carbonization for 3h, and grinding to obtain peanut shell pyrolysis hard carbon electrode material;

[0047] Step 3, the carbon material prepared above is used as an active substance of a battery negative electrode material for the preparation of a sodium ion battery.

[0048] According to the mass ratio of 92%:3%:1.5%:3.5%, 184mg of carbon material powder, 6mg of conductive carbon black, 6mg of 2%(w / w) carboxymethyl cellulose solution, 17.5mg of 40%(w / w) butadiene rubber, and an appropriate amount of deionized water are added, stirred for 20min to form a uniform slurry, and then coated on the surface of a copper(Cu) foil using a 100μm doctor blade, and dried in a 105℃ air drying oven for 2h. The Cu foil with active material is cut into a circular negative electrode sheet, and then transferred to a glove box for standby.

[0049] The assembly of the simulated battery is carried out in an Ar atmosphere filled MIKROUNA glove box, the prepared carbon material electrode sheet is used as the negative electrode, the commercial electrolyte 1.0mol / L NaPF6 / EC:DMC(1:1)(V:V) is used as the electrolyte, and the Na metal sheet is used as the counter electrode to assemble a 2016 button cell. The assembled half-cell has a first coulombic efficiency of 72.22% and a first circle charge specific capacity of 235.53mAh / g at a current density of 20mA / g.

[0050] Comparative Example 2

[0051] The embodiment of the present application provides a preparation method of a biomass-based hard carbon negative electrode material for a sodium ion battery, and the steps comprise:

[0052] Step 1, drying, 10g of peanut shell powder is placed in a forced air drying oven, the drying temperature is 80 DEG C, the drying time is 2h, and the water is removed by drying;

[0053] Step 2, ball milling treatment, the peanut shell powder obtained after step 1 is placed in a stainless steel ball mill tank together with stainless steel balls at a ball-to-material ratio of 1:5, and ball milling treatment is carried out at a speed of 500 rpm for 48h, and the material is separated from the ball milling medium after sieving to obtain a ball milling material;

[0054] Step 3, carbonization, the peanut shell powder obtained after step 2 is placed in a tube furnace, and the temperature is raised to 400 DEG C at a heating rate of 2 DEG C / min under an argon atmosphere, and pre-carbonization is carried out for 3h, and then the temperature is raised to 1300 DEG C at a heating rate of 2 DEG C / min after cooling to room temperature, and high-temperature carbonization is carried out for 3h, and then the temperature is cooled to room temperature, and grinding and crushing are carried out to obtain a peanut shell pyrolysis hard carbon electrode material;

[0055] Step 4, the carbon material prepared above is used as an active substance of a battery negative electrode material for the preparation of a sodium ion battery, and the specific method is the same as that of the comparative example 1.

[0056] Example 1

[0057] The embodiment of the present application provides a preparation method of a biomass-based hard carbon negative electrode material for a sodium ion battery, and the steps comprise:

[0058] Step 1, drying, 10g of peanut shell powder is placed in a forced air drying oven, the drying temperature is 80 DEG C, the drying time is 2h, and the water is removed by drying;

[0059] Step 2, ball milling treatment, the peanut shell powder obtained after step 1 is placed in a stainless steel ball mill tank together with stainless steel balls at a ball-to-material ratio of 1:5, and ball milling treatment is carried out at a speed of 500 rpm for 48h, and the material is separated from the ball milling medium after sieving to obtain a ball milling material;

[0060] Step 3, carbonization, the peanut shell powder obtained after step 2 is placed in a tube furnace, and the temperature is raised to 400 DEG C at a heating rate of 2 DEG C / min under an argon atmosphere, and pre-carbonization is carried out for 3h, and then the temperature is raised to 1300 DEG C at a heating rate of 2 DEG C / min after cooling to room temperature, and high-temperature carbonization is carried out for 3h, and then the temperature is cooled to room temperature, and grinding and crushing are carried out to obtain a peanut shell pyrolysis hard carbon electrode material;

[0061] Step 4, the carbon material prepared above is used as an active substance of a battery negative electrode material for the preparation of a sodium ion battery, and the specific method is the same as that of Comparative Example 1. The assembled half battery has a first coulombic efficiency of 91.06% and a first circle charge specific capacity of 315.17 mAh / g at a current density of 20 mA / g.

[0062] Example 2

[0063] The embodiment of the present application provides a preparation method of a biomass-based hard carbon negative electrode material for a sodium ion battery, and the steps include:

[0064] Step 1, drying, 10 g of peanut shell powder is placed in a forced air drying oven, the drying temperature is 80 DEG C, the drying time is 2 h, and the water is removed by drying;

[0065] Step 2, ball milling treatment, the peanut shell powder obtained after step 1 is placed in a stainless steel ball mill tank together with stainless steel balls according to a ball-to-material ratio of 1:10, CO2 is introduced into the stainless steel ball mill tank to reach a pressure of 0.5 MPa, ball milling treatment is carried out at a rotating speed of 500 rpm for 48 h, and the material and the ball milling medium are separated by sieving to obtain a ball milling material;

[0066] Step 3, carbonization, the ball milling material obtained after step 2 is placed in a tube furnace, heated to 400 DEG C at a heating rate of 2 DEG C / min under an argon atmosphere, pre-carbonized for 3 h, cooled to room temperature, heated to 1300 DEG C at a heating rate of 2 DEG C / min, high-temperature carbonized for 3 h, cooled to room temperature, and ground and crushed to obtain a peanut shell pyrolytic hard carbon electrode material;

[0067] Step 4, the carbon material prepared above is used as an active substance of a battery negative electrode material for the preparation of a sodium ion battery, and the specific method is the same as that of Comparative Example 1.

[0068] Example 3

[0069] The embodiment of the present application provides a preparation method of a biomass-based hard carbon negative electrode material for a sodium ion battery, and the steps include:

[0070] Step 1, drying, 10 g of peanut shell powder is placed in a forced air drying oven, the drying temperature is 80 DEG C, the drying time is 2 h, and the water is removed by drying;

[0071] Step 2, ball milling treatment, the peanut shell powder obtained after step 1 is placed in a stainless steel ball mill tank together with stainless steel balls according to a ball-to-material ratio of 1:10, CO2 is introduced into the stainless steel ball mill tank to reach a pressure of 0.5 MPa, ball milling treatment is carried out at a rotating speed of 500 rpm for 48 h, and the material and the ball milling medium are separated by sieving to obtain a ball milling material;

[0072] Step 3, carbonization, the ball milling material obtained after step 2 is placed in a tube furnace, and heated to 400 DEG C at a heating rate of 2 DEG C / min under an argon atmosphere, pre-carbonization for 3h, after cooling to room temperature, heated to 1300 DEG C at a heating rate of 2 DEG C / min, high-temperature carbonization for 3h, cooled to room temperature, ground and crushed to obtain peanut shell pyrolysis hard carbon electrode material;

[0073] Step 4, the carbon material prepared above is used as an active substance of a battery negative electrode material for the preparation of a sodium ion battery, and the specific method is the same as that of Comparative Example 1.

[0074] Example 4

[0075] The embodiment of the present application provides a preparation method of a biomass-based hard carbon negative electrode material for a sodium ion battery, and the steps include:

[0076] Step 1, drying, 10g of peanut shell powder is placed in a forced air drying oven, the drying temperature is 80 DEG C, and the drying time is 2h, and the water is removed by drying;

[0077] Step 2, ball milling treatment, the peanut shell powder obtained after step 1 is placed in a stainless steel ball milling tank together with stainless steel balls at a ball-to-material ratio of 1:5, and CO2 is introduced into the stainless steel ball milling tank to reach a pressure of 0.5MPa, and the ball milling treatment is carried out at a rotating speed of 1000rpm for 48h, and the material and the ball milling medium are separated by sieving to obtain a ball milling material;

[0078] Step 3, carbonization, the ball milling material obtained after step 2 is placed in a tube furnace, and heated to 400 DEG C at a heating rate of 2 DEG C / min under an argon atmosphere, pre-carbonization for 3h, after cooling to room temperature, heated to 1300 DEG C at a heating rate of 2 DEG C / min, high-temperature carbonization for 3h, cooled to room temperature, ground and crushed to obtain peanut shell pyrolysis hard carbon electrode material;

[0079] Step 4, the carbon material prepared above is used as an active substance of a battery negative electrode material for the preparation of a sodium ion battery, and the specific method is the same as that of Comparative Example 1.

[0080] Example 5

[0081] The embodiment of the present application provides a preparation method of a biomass-based hard carbon negative electrode material for a sodium ion battery, and the steps include:

[0082] Step 1, drying, 10g of peanut shell powder is placed in a forced air drying oven, the drying temperature is 80 DEG C, and the drying time is 2h, and the water is removed by drying;

[0083] Step 2, ball milling treatment, the peanut shell powder obtained after step 1 is placed in a stainless steel ball mill tank with a ball-to-material ratio of 1:5 and stainless steel balls, and CO2 is introduced into the stainless steel ball mill tank to reach a pressure of 0.5 MPa, and the ball milling treatment is carried out at a speed of 500 rpm for 24 h, and the material is separated from the ball milling medium by sieving to obtain a ball-milled material;

[0084] Step 3, carbonization, the ball-milled material obtained after step 2 is placed in a tube furnace, heated to 400℃ at a heating rate of 2℃ / min under an argon atmosphere, pre-carbonized for 3 h, cooled to room temperature, then heated to 1300℃ at a heating rate of 2℃ / min, high-temperature carbonized for 3 h, cooled to room temperature, and ground and crushed to obtain a peanut shell pyrolytic hard carbon electrode material;

[0085] Step 4, the carbon material prepared above is used as an active substance of a battery negative electrode material for the preparation of a sodium ion battery, and the specific method is the same as that of Comparative Example 1.

[0086] Example 6

[0087] The embodiment of the present application provides a preparation method of a biomass-based hard carbon negative electrode material for a sodium ion battery, and the steps include:

[0088] Step 1, drying, 10 g of peanut shell powder is placed in a forced air drying oven, the drying temperature is 80℃, and the drying time is 2 h to remove water;

[0089] Step 2, ball milling treatment, the peanut shell powder obtained after step 1 is placed in a stainless steel ball mill tank with a ball-to-material ratio of 1:5 and stainless steel balls, and O2 is introduced into the stainless steel ball mill tank to reach a pressure of 0.5 MPa, and the ball milling treatment is carried out at a speed of 500 rpm for 48 h, and the material is separated from the ball milling medium by sieving to obtain a ball-milled material;

[0090] Step 3, carbonization, the ball-milled material obtained after step 2 is placed in a tube furnace, heated to 400℃ at a heating rate of 2℃ / min under an argon atmosphere, pre-carbonized for 3 h, cooled to room temperature, then heated to 1300℃ at a heating rate of 2℃ / min, high-temperature carbonized for 3 h, cooled to room temperature, and ground and crushed to obtain a peanut shell pyrolytic hard carbon electrode material;

[0091] Step 4, the carbon material prepared above is used as an active substance of a battery negative electrode material for the preparation of a sodium ion battery, and the specific method is the same as that of Comparative Example 1.

[0092] Example 7

[0093] The embodiment of the present application provides a preparation method of a biomass-based hard carbon negative electrode material for a sodium ion battery, and the steps include:

[0094] Step 1, drying, take peanut shell powder 10g placed in the drying oven, drying temperature 80℃, drying time 2h, drying to remove water;

[0095] Step 2, ball milling, the peanut shell powder obtained after step 1 is placed in a stainless steel ball mill tank according to a ball-to-material ratio of 1:5 with stainless steel balls, and NH3 is introduced into the stainless steel ball mill tank to reach a pressure of 0.5 MPa, and ball milling is performed at a speed of 500 rpm for 48 h, and the material is separated from the ball milling medium by sieving to obtain a ball-milled material;

[0096] Step 3, carbonization, the ball-milled material obtained after step 2 is placed in a tube furnace, heated to 400℃ at a heating rate of 2℃ / min under an argon atmosphere, pre-carbonized for 3h, cooled to room temperature, then heated to 1300℃ at a heating rate of 2℃ / min, high-temperature carbonized for 3h, cooled to room temperature, ground and crushed to obtain peanut shell powder pyrolytic hard carbon electrode material;

[0097] Step 4, the carbon material prepared above is used as an active substance of a battery negative electrode material for the preparation of a sodium ion battery, and the specific method is the same as that of Comparative Example 1.

[0098] Example 8

[0099] The embodiment of the present application provides a preparation method of a biomass-based hard carbon negative electrode material for a sodium ion battery, and the steps include:

[0100] Step 1, drying, take bamboo powder 10g placed in the drying oven, drying temperature 80℃, drying time 2h, drying to remove water;

[0101] Step 2, ball milling, the bamboo powder obtained after step 1 is placed in a stainless steel ball mill tank according to a ball-to-material ratio of 1:5 with stainless steel balls, and CO2 is introduced into the stainless steel ball mill tank to reach a pressure of 0.5 MPa, and ball milling is performed at a speed of 500 rpm for 48 h, and the material is separated from the ball milling medium by sieving to obtain a ball-milled material;

[0102] Step 3, carbonization, the ball-milled material obtained after step 2 is placed in a tube furnace, heated to 400℃ at a heating rate of 2℃ / min under an argon atmosphere, pre-carbonized for 3h, cooled to room temperature, then heated to 1300℃ at a heating rate of 2℃ / min, high-temperature carbonized for 3h, cooled to room temperature, ground and crushed to obtain bamboo powder pyrolytic hard carbon electrode material;

[0103] Step 4, the carbon material prepared above is used as an active substance of a battery negative electrode material for the preparation of a sodium ion battery, and the specific method is the same as that of Comparative Example 1. The assembled half battery has a first coulombic efficiency of 88.59% and a first cycle charge specific capacity of 306.37 mAh / g at a current density of 20 mA / g.

[0104] Table 1 below is a table of relevant parameters for the half-cells assembled for Comparative Examples 1-2 and Examples 1-7, in order

[0105]

Claims

1. A method for preparing a mechanically surface-modified biomass hard carbon material, characterized by: The biomass raw material is dried and then put into a ball mill tank for high-pressure ball milling to obtain a precursor; the precursor is subjected to multi-stage continuous carbonization and crushing to obtain the product; the atmosphere of the high-pressure ball milling is single or mixed; The high-pressure ball milling is dry base ball milling, and the conditions are as follows: the rotation speed is 100-1000 rpm, the time is 12-48 h, the ball-to-material ratio is 1:0.05-20, and the pressure is 0.1-0.7 MPa; The multi-stage continuous carbonization comprises a pre-carbonization stage and a high-temperature carbonization stage, and the carbonization is completed by cooling in the furnace to room temperature; the pre-carbonization conditions are as follows: the temperature is 200-600 DEG C, and the treatment time is 2-3 h; the high-temperature carbonization conditions are as follows: the temperature is 1000-1700 DEG C, and the carbonization time is 2-5 h.

2. The method of claim 1, wherein the mechanical surface modification of the biomass-derived hard carbon material is performed by a mechanical milling process. The biomass raw material is various plant organisms synthesized by air, water and soil; and the atmosphere of the high-pressure ball milling is at least one of CO2, NH3 and O2.

3. The method of claim 1, wherein the mechanical surface modification of the biomass-derived hard carbon material is performed by a mechanical milling process. The biomass raw material is one of starch, bamboo, wood, peanut shell and wheat shell; and the drying conditions are as follows: the temperature is 70-80 DEG C, and the time is 2-3 h.

4. The method of claim 1, wherein the mechanical surface modification of the biomass-derived hard carbon material is performed by a mechanical milling process. The ball milling medium and the tank body of the high-pressure ball milling are one of agate, zirconia and stainless steel.

5. A mechanically surface-modified biomass hard carbon material, characterized by: The biomass hard carbon material is prepared by the preparation method according to any one of claims 1-4; the specific surface area of the biomass hard carbon material is 200-250 m 2 / g.

6. The use of a mechanically surface-modified biomass hard carbon material according to claim 5, characterized in that: The hard carbon is used as a battery negative material to prepare a sodium ion battery.

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