Method for preparing hard carbon material from biomass material and high molecular polymer, product and application thereof

Abstract

The application belongs to the field of sodium ion battery negative electrode materials, and particularly relates to a method for preparing hard carbon material from biomass material and high molecular polymer and application thereof. Powder obtained after pre-carbonization of the biomass material is mixed and solidified with the high molecular polymer, high-temperature carbonization treatment is performed on the solidified material, and the hard carbon material is obtained. The hard carbon material obtained by the method has high initial coulomb efficiency and high reversible specific capacity, and the material used as a negative electrode and applied in a sodium ion battery can significantly improve the performance of the sodium ion battery.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion batteries, and specifically relates to a method for preparing hard carbon materials from biomass materials and polymers, and its application. Background Technology

[0002] The extensive use of fossil fuels generates substantial carbon emissions, becoming a significant contributor to global climate change and environmental pollution. To promote energy upgrading, increase the proportion of green energy, and foster the rapid development of renewable energy, large-scale energy storage technology is a crucial element. Electrochemical energy storage technology is not limited by geographical terrain and can directly store and release electrical energy. In the future energy landscape, it can address the discontinuous and uncontrollable nature of renewable energy generation such as wind and solar power, ensuring controllable grid connection and on-demand transmission and distribution. It can also solve grid peak-shaving and frequency regulation, peak shaving and valley filling, intelligent power supply, and distributed energy supply issues, improving multi-energy coupling efficiency and achieving energy conservation and emission reduction. Applied to the electricity consumption side, it can support the electrification of energy-consuming terminals such as automobiles, promoting their decarbonization and intelligentization. Sodium-ion batteries possess advantages such as abundant raw material resources, low cost, high cost-effectiveness, excellent performance, and high safety, showing broad application prospects in electric bicycles, low-speed electric vehicles, distributed energy storage, and large-scale energy storage.

[0003] Sodium-ion batteries convert chemical energy into electrical energy by allowing sodium ions to shuttle back and forth between the positive and negative electrode materials. The basic principle is similar to that of lithium-ion batteries. The positive electrode, negative electrode, separator, and electrolyte are the key components of a sodium-ion battery. The positive and negative electrode materials play a decisive role in the battery's operating voltage, energy density, cycle performance, and rate performance. Currently, various sodium-ion battery positive electrode materials have entered pilot-scale production exploration. Compared to the positive electrode, the exploration and development of large-scale, industrialized preparation of sodium-ion battery negative electrode materials has progressed slowly.

[0004] Carbon-based materials are preferred for sodium-ion battery anode materials due to their abundant resources, low cost, low sodium storage potential, and small volume change during charge and discharge. Extensive research has demonstrated that hard carbon materials, with their high reversible capacity and relatively low sodium storage potential, are the most practically valuable and one of the best choices for commercial sodium-ion battery anode materials. Hard carbon refers to carbon that is difficult to graphitize at temperatures above 2500℃, and is a type of amorphous carbon material. Microstructural analysis shows that hard carbon materials have fewer carbon layers stacked along the c-axis and exhibit a random orientation, exhibiting long-range disorder and short-range order in their microstructure, with numerous nanopores within.

[0005] In calculating the material costs during the manufacturing process of sodium-ion batteries, the cost of the anode material has become the largest component. Biomass materials are abundant in nature, with diverse varieties and plentiful resources. This invention uses biomass materials as raw materials, pre-carbonizing them before compounding them with organic polymers, and then carbonizing them at high temperatures to prepare high-performance hard carbon materials. Hard carbon generated from biomass-based materials naturally possesses abundant nanopores and defects, providing high sodium storage capacity. The carbon material formed by the polymer exhibits good consistency and short-range ordering superior to biomass-based carbon, demonstrating a higher initial coulombic efficiency. This invention pre-carbonizes biomass materials and then compoundes them with polymers in powder form. The pre-carbonized powder has strong surface activity, allowing it to uniformly integrate with the three-dimensional network structure formed during the polymer curing process. Finally, the composite material is carbonized at high temperatures to obtain hard carbon with both high initial efficiency and high specific capacity. Introducing a carbon-containing gas source during carbonization reduces heteroatoms and oxygen-containing functionalities on the material surface, improving material performance. Summary of the Invention

[0006] This invention aims to improve the performance of sodium-ion batteries, achieve the large-scale preparation of biomass and polymer composite hard carbon materials, and reduce the cost of sodium-ion batteries. A method for preparing hard carbon materials from biomass materials and polymers has been designed and developed. The hard carbon materials prepared by this method have characteristics such as high initial coulombic efficiency and high reversible specific capacity. Using this material as a negative electrode active material in sodium-ion batteries can reduce the cost of sodium-ion batteries, increase the energy density of sodium-ion batteries, and make the whole battery exhibit excellent performance.

[0007] The technical solution of this invention is:

[0008] 1) Soak biomass material blocks with a particle size or length of 10-60 mm in a water-soluble organic solution at 70-100℃ for 1-6 hours;

[0009] 2) Place the biomass material treated in step 1) into a heating furnace for pre-calcination. The pre-calcination atmosphere is an oxygen-containing atmosphere, which is a mixture of oxygen and inert gas, namely nitrogen or argon, or one or more of these inert gases. The oxygen volume percentage in the atmosphere is 2-11%. The pre-calcination temperature is increased from room temperature at a rate of 1-15℃ / min, the heating is terminated at 500-800℃, and the holding time is 1-5h, to obtain pre-carbonized biomass material. The gas hourly space velocity (GHSV) of the oxygen-containing atmosphere is 30-220 mL / min / g. The carbon yield of the treated biomass material is controlled to be 20-50%. Carbon yield = dry weight of pre-carbonized biomass material after pre-calcination / dry weight of biomass material before pre-calcination.

[0010] 3) Crush the pre-carbonized biomass material from step 2) into powder with a particle size of 5–75 μm;

[0011] 4) Add polymer and curing agent to the pre-carbonized biomass material powder obtained in step 3), mix evenly, cut into 20-60mm blocks, and let stand in a vacuum oven to cure, to obtain pre-carbonized biomass material powder and polymer composite.

[0012] 5) The blocky composite from step 4) is subjected to high-temperature carbonization calcination to obtain hard carbon material. The calcination process is as follows: first, the temperature is increased from room temperature to 700-950℃ at a rate of 2-20℃ / min and held for 1-5 hours; then, the temperature is increased to 1000-1500℃ at a rate of 1-10℃ / min and held for 1-5 hours; then, the temperature is naturally cooled to room temperature to obtain blocky hard carbon material.

[0013] The entire high-temperature carbonization and roasting process is carried out in a mixed atmosphere of inert gas and carbon source gas;

[0014] The inert gas is one or a mixture of nitrogen and argon, and the carbon source gas is one or more of blast furnace gas, coking gas, carbon monoxide, methane, ethane, propane, n-butane, isobutane, ethylene, propylene, n-butene, isobutene, butadiene, cis-dibutene, trans-dibutene, cyclopropane, acetylene, and propyne, preferably one or more of blast furnace gas, coking gas, carbon monoxide, methane, ethane, propane, and ethylene, wherein the volume percentage of the carbon source gas is 5-70%; the gas space velocity of the mixture is 5-100 mL / min / g.

[0015] Furthermore, the blocky hard carbon material obtained in step 5) is crushed, ball-milled, air-jet pulverized, and sieved to obtain a hard carbon material product with a particle size of 0.5–8 μm.

[0016] Furthermore, the biomass materials mentioned in step 1) include one or more of the following biomass materials: wood, bamboo, walnut shells, pine nut shells, peanut shells, coconut shells, straw, lignin, cellulose, hemicellulose, starch, etc., preferably one or more of the following biomass materials with high yield: wood, bamboo, coconut shells, straw, lignin, cellulose.

[0017] Furthermore, the water-soluble organic matter mentioned in step 1) includes one or more of the following: polysaccharides, disaccharides, monosaccharides, carboxymethyl starch, acetic acid starch, hydroxymethyl cellulose, polyacrylamide, and polyvinylpyrrolidone, and the mass concentration of the organic matter in the aqueous solution is 5-50%.

[0018] Further, in step 4), the polymer is one or more of liquid epoxy resin, acrylic resin, polyurethane, and phenolic resin, and the curing agent is an amine curing agent or an anhydride curing agent, preferably one or more of polyamide, ethylenediamine, diethylenetriamine, fatty amine, and phthalic anhydride. The mass ratio of the polymer to the pre-carbonized biomass material is 1:4 to 7:3, the amount of curing agent added is 5 to 60% of the polymer mass, the curing temperature is 25 to 160°C, and the curing time is 2 to 24 hours.

[0019] Further, in step 5), the main components of the blast furnace gas are 20-40% carbon monoxide, 50-70% nitrogen, and 1-10% carbon dioxide (volume composition); the coking gas consists of 45-60% hydrogen, 30-45% methane, 5-10% carbon monoxide, and 1-10% carbon dioxide (volume composition).

[0020] Furthermore, the hard carbon material is prepared using any one of the above technical solutions.

[0021] Furthermore, the hard carbon materials exhibit a pore size distribution range of 0.1–20 nm, an average pore size range of 0.3–8 nm, and a specific surface area of ​​1–30 m². 2 / g.

[0022] Furthermore, using any of the aforementioned hard carbon materials as the negative electrode active material in sodium-ion batteries can yield low-cost, high-energy-density, and high-performance sodium-ion batteries.

[0023] The hard carbon material obtained by this method has high initial coulombic efficiency and high reversible specific capacity. Using this material as a negative electrode in sodium-ion batteries can significantly improve the performance of sodium-ion batteries.

[0024] The method for preparing low-cost hard carbon materials using coal proposed in this invention has the following significant advantages:

[0025] 1) Biomass materials are renewable resources in nature, with large reserves and abundant resources. Using biomass materials to produce hard carbon has the advantages of low cost and abundant raw material resources. In the preparation process, blast furnace gas or coking gas is selected as the carbon-containing gas source, which improves the material performance while reducing the manufacturing cost.

[0026] 2) Carbon materials formed by polymers have better short-range order than biomass-based carbon, fewer micropores, higher initial coulombic efficiency, and better cycle stability. In this invention, biomass materials are pre-carbonized and then compounded with polymers in powder form. The pre-carbonized biomass powder and the three-dimensional network structure of the polymer during the curing process are uniformly integrated. Finally, the composite material is carbonized at high temperature, and the resulting hard carbon material has high initial efficiency, high specific capacity, and high cycle stability. Attached Figure Description

[0027] Figure 1 This is a SEM image of the hard carbon material prepared in Example 1.

[0028] Figure 2 The image shows the XRD pattern of the hard carbon material prepared in Example 1.

[0029] Figure 3 The image shows the charge-discharge curves of the hard carbon material coin cell prepared in Example 1.

[0030] Figure 4 The image shows the charge-discharge curves of a 5.5Ah soft-pack full cell prepared with the hard carbon material obtained in Example 1 and using sodium vanadium phosphate cathode. Detailed Implementation

[0031] The advantages of the present invention will be further explained below with reference to specific embodiments.

[0032] Example 1

[0033] 1) Weigh 500g of bamboo, cut it into bamboo pieces with a length of about 30-40mm, and soak them in a 35% sucrose solution at 90℃ for 4 hours;

[0034] 2) Place the bamboo blocks treated in step 1) into a heating furnace for pre-carbonization by roasting. The roasting atmosphere is a mixture of oxygen and nitrogen, with oxygen accounting for 6% by volume. The gas hourly space velocity (GHSV) of the mixed atmosphere is 60 mL / min / g, and the heating rate is 5°C.

[0035] The heating rate was 100°C / min, the heating termination temperature was 600°C, and the holding time was 2 hours, resulting in pre-carbonized bamboo blocks with a carbon yield of 25%.

[0036] 3) Crush the bamboo pre-carbonization product from step 2) to obtain bamboo pre-carbonization product powder with a particle size of 5-75 μm;

[0037] 4) Weigh an epoxy resin solution with a mass ratio of 1:1 to the bamboo pre-carbonized product powder from step 3), and add it to the powder from step 3); the epoxy value of the epoxy resin solution is 0.49-0.52, and the molecular weight is 350-500; then add the curing agent diethylenetriamine and mix evenly, the amount of curing agent added is 20% of the mass of epoxy resin; after mixing evenly, divide the mixture into 40mm blocks, and let them stand and cure in an oven at 85℃ to obtain a solid composite material in which bamboo pre-carbonized powder and epoxy resin are evenly mixed.

[0038] 5) The blocky solid composite obtained in step 4) was subjected to high-temperature carbonization calcination. The calcination process was as follows: first, the temperature was increased to 800℃ at 10℃ / min and held for 1 hour; then, the temperature was increased to 1350℃ at 5℃ / min and held for 3 hours; finally, it was naturally cooled to room temperature to obtain blocky hard carbon material. The entire high-temperature carbonization calcination process was carried out in a mixed atmosphere of nitrogen and coking gas, with coking gas accounting for 20%. The composition of the coking gas was 52% hydrogen, 38% methane, 7% carbon monoxide, and 3% carbon dioxide; the gas space velocity was 40 mL / min / g.

[0039] 6) The blocky hard carbon material obtained in step 5) is ball-milled, air-jet pulverized and sieved to obtain a hard carbon material product with a particle size of 0.5 to 5 μm.

[0040] The specific surface area, average pore size, and micropore size range of the hard carbon material obtained in Example 1 are shown in Table 1.

[0041] The prepared hard carbon material was used to fabricate a negative electrode, which was then matched with a sodium vanadium phosphate positive electrode to fabricate a pouch cell. Specific conditions for fabricating the negative electrode using the hard carbon material were as follows: slurry ratio: hard carbon:Sp:CMC (carboxymethyl cellulose):SBR (styrene-butadiene rubber) = 92:4:2:2; electrode surface loading was 4.5 mg / cm². 2 The compacted density is 0.93 g / m³. 3 Based on a negative electrode capacity to positive electrode capacity ratio of 1.1, sodium vanadium phosphate positive electrode sheets were matched, and a 5.5Ah rated capacity soft-pack battery was fabricated using a Z-shaped stacking process for performance testing. The test conditions were: first coulombic efficiency test conditions for the full cell, voltage range:

[0042] Test conditions for full battery energy density: voltage range: 2.0–4.3V, ambient temperature: 45℃, charge / discharge test current rate: 0.1C.

[0043] The conditions for preparing coin half-cells using the prepared hard carbon material on sodium metal are as follows: slurry ratio, hard carbon:

[0044] Sp:CMC:SBR = 92:4:2:2; electrode surface loading is 3 mg / cm2; compaction density is 0.90 g / m3; voltage range: 0~2.5V; test ambient temperature: 25℃; first test of coulombic efficiency and specific capacity; charge / discharge rate is 0.1C.

[0045] Example 2

[0046] The process and conditions are the same as in Example 1, except that in step 1 of this example, a glucose solution with a mass concentration of 35% is used to soak the sample at 90°C for 4 hours.

[0047] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 2 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0048] Example 3

[0049] The process and conditions are the same as in Example 1, except that in step 1 of this example, a sucrose solution with a mass concentration of 15% is used.

[0050] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 3 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0051] Example 4

[0052] The process and conditions are the same as in Example 1, except that in step 1 of this example, the biomass material used is poplar.

[0053] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 4 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0054] Example 5

[0055] The process and conditions are the same as in Example 1, except that in step 1 of this example, the biomass material used is straw.

[0056] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 5 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0057] Example 6

[0058] The process and conditions are the same as in Example 1, except that in step 1 of this example, the biomass material used is coconut shell.

[0059] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 6 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0060] Example 7

[0061] The process and conditions are the same as in Example 1. The difference is that in step 1 of this example, the biomass material used is lignin, which is pressed into blocks.

[0062] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 7 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0063] Example 8

[0064] The process and conditions are the same as in Example 1. The difference is in step 2 of this example, where the roasting atmosphere is a mixture of oxygen and nitrogen, with oxygen accounting for 2% of the volume.

[0065] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 8 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0066] Example 9

[0067] The process and conditions are the same as in Example 1. The difference is in step 2 of this example, where the roasting atmosphere is a mixture of oxygen and nitrogen, with oxygen accounting for 9% of the volume.

[0068] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 9 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0069] Example 10

[0070] The process and conditions are the same as in Example 1, except that in step 2 of this example, the temperature at which the heating is terminated is 700°C.

[0071] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 10 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0072] Example 11

[0073] The process and conditions are the same as in Example 1, except that in step 2 of this example, the temperature at which the heating is terminated is 800°C.

[0074] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 11 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0075] Example 12

[0076] The process and conditions are the same as in Example 1, except that in step 2 of this example, the heat preservation time is 4 hours.

[0077] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 12 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0078] Example 13

[0079] The process and conditions are the same as in Example 1, except that in step 2 of this example, the gas hourly space velocity (GHSV) of the oxygen-containing atmosphere is 35 mL / min / g.

[0080] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 13 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0081] Example 14

[0082] The process and conditions are the same as in Example 1, except that in step 2 of this example, the gas hourly space velocity of the oxygen-containing atmosphere is 120 mL / min / g.

[0083] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 14 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0084] Example 15

[0085] The process and conditions are the same as in Example 1, except that in step 2 of this example, the gas hourly space velocity of the oxygen-containing atmosphere is 200 mL / min / g.

[0086] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 15 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0087] Example 16

[0088] The process and conditions are the same as in Example 1, except that in step 4 of this example, the mass ratio of epoxy resin liquid to bamboo pre-carbonized product powder is 1:2.

[0089] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 16 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0090] Example 17

[0091] The process and conditions are the same as in Example 1, except that in step 4 of this example, the mass ratio of epoxy resin liquid to bamboo pre-carbonized product powder is 3:2.

[0092] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 17 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0093] Example 18

[0094] The process and conditions are the same as in Example 1, except that in step 4 of this example, a phenolic resin adhesive is used, and the molecular weight of the phenolic resin adhesive is 500-800.

[0095] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 18 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0096] Example 19

[0097] The process and conditions are the same as in Example 1, except that in this example, step 5 is the second stage of high-temperature roasting, with the temperature raised to 1400°C.

[0098] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 19 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0099] Example 20

[0100] The process and conditions are the same as in Example 1, except that in step 5 of this example, the second stage of high-temperature heat preservation time is 3 hours.

[0101] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 20 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0102] Example 21

[0103] The process and conditions are the same as in Example 1. The difference is in step 5 of this example. The entire high-temperature carbonization roasting process is carried out in a mixed atmosphere of nitrogen and blast furnace gas, with blast furnace gas accounting for 50%. The main components of blast furnace gas are carbon monoxide 35%, nitrogen 60%, and carbon dioxide 5%.

[0104] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 21 is tested, and the test methods, conditions and contents are the same as in Example 1.

[0105] Example 22

[0106] The process and conditions are the same as in Example 1. The difference is in step 5 of this example, where the entire high-temperature carbonization and roasting process is carried out in a mixed atmosphere of nitrogen and methane, with methane accounting for 20%.

[0107] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 22 is tested, and the test methods, conditions, and contents are the same as in Example 1.

[0108] Example 23

[0109] The process and conditions are the same as in Example 1. The difference is in step 5 of this example, where the entire high-temperature carbonization and roasting process is carried out in a mixed atmosphere of nitrogen and ethylene, with ethylene accounting for 20%.

[0110] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 23 is tested, and the test methods, conditions, and contents are the same as in Example 1.

[0111] Example 24

[0112] The process and conditions are the same as in Example 1, except that in step 5 of this example, the space velocity of the mixture during the entire high-temperature carbonization and roasting process is 15 mL / min / g.

[0113] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 24 is tested, and the test methods, conditions, and contents are the same as in Example 1.

[0114] Example 25

[0115] The process and conditions are the same as in Example 1, except that in step 5 of this example, the space velocity of the mixture during the entire high-temperature carbonization and roasting process is 80 mL / min / g.

[0116] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 25 is tested, and the test methods, conditions, and contents are the same as in Example 1.

[0117] Example 26

[0118] The process and conditions are the same as in Example 1. The difference is in step 5 of this example. During the roasting process, after the first stage temperature is raised to 700°C, the holding time is 4 hours.

[0119] The remaining steps are the same as in Example 1. The hard carbon material prepared in Example 26 is tested, and the test methods, conditions, and contents are the same as in Example 1.

[0120] Comparative Example 1

[0121] The process and conditions were the same as in Example 1, except that step 1 in Comparative Example 1 was different, and the biomass material was soaked in deionized water at 90°C for 4 hours.

[0122] The remaining steps are the same as in Example 1. The hard carbon material prepared in Comparative Example 1 is tested, and the test methods, test conditions, and test contents are the same as in Example 1.

[0123] Comparative Example 2

[0124] The process and conditions were the same as in Example 1, except that step 2 in Comparative Example 2 was different, and a nitrogen atmosphere was used during the roasting process.

[0125] The remaining steps are the same as in Example 1. The hard carbon material prepared in Comparative Example 2 is tested, and the test methods, test conditions, and test contents are the same as in Example 1.

[0126] Comparative Example 3

[0127] The process and conditions were the same as in Example 1, except that step 4 in Comparative Example 4 was different; a polymer was not used for compounding. The specific differences between Comparative Example 1 and Example 1 are as follows:

[0128] 4) The bamboo pre-carbonized product powder obtained in step 3) is placed in a vacuum oven at 85°C for static baking.

[0129] The remaining steps are the same as in Example 1. The hard carbon material prepared in Comparative Example 3 is tested, and the test methods, test conditions, and test contents are the same as in Example 1.

[0130] Comparative Example 4

[0131] The process and conditions were the same as in Example 1, except that step 4 in Comparative Example 4 was different, and the mass ratio of epoxy resin liquid to bamboo pre-carbonized product powder was 9:1.

[0132] The remaining steps are the same as in Example 1. The hard carbon material prepared in Comparative Example 4 is tested, and the test methods, test conditions, and test contents are the same as in Example 1.

[0133] Comparative Example 5

[0134] The process and conditions were the same as in Example 1, except that step 5 in Comparative Example 5 was different, and the highest temperature of the second stage of roasting was 800°C.

[0135] The remaining steps are the same as in Example 1. The hard carbon material prepared in Comparative Example 5 is tested, and the test methods, test conditions, and test contents are the same as in Example 1.

[0136] Comparative Example 6

[0137] The process and conditions were the same as in Example 1, except that step 5 in Comparative Example 6 was different, and the entire roasting process was carried out in a nitrogen atmosphere.

[0138] The remaining steps are the same as in Example 1. The hard carbon material prepared in Comparative Example 6 is tested, and the test methods, test conditions, and test contents are the same as in Example 1.

[0139] Comparative Example 7

[0140] The process and conditions are the same as in Example 1, except that step 5 in Comparative Example 6 is different, and the proportion of coking gas is 1%.

[0141] The remaining steps are the same as in Example 1. The hard carbon material prepared in Comparative Example 7 was tested, and the test methods, test conditions, and test contents were the same as in Example 1.

[0142] Table 1 compares the performance test results of hard carbon materials obtained in Examples 1 to 23 and Comparative Examples 1 to 8.

[0143]

[0144]

[0145]

[0146] The implementation data from Examples 1-26 above show that the present invention uses biomass materials as raw materials, pre-carbonizes them by calcination in an atmosphere containing 2-11% oxygen, and then composites them with organic polymers before high-temperature carbonization to prepare hard carbon materials. The obtained hard carbon materials have a low specific surface area, a small average micropore size, and a small micropore diameter distribution range. When applied to sodium-ion batteries, they exhibit significantly higher initial coulombic efficiency; the initial coulombic efficiency of the hard carbon materials in Examples 1-26 is higher than 80%. The materials also have a high specific capacity. When the hard carbon materials prepared by the method of the present invention are used as negative electrodes in sodium-ion pouch cells, 5Ah pouch cells are produced with high initial coulombic efficiency; the energy density of the pouch cells in Examples 1-26 is higher than 120Wh / kg, demonstrating significant advantages.

[0147] Comparative Example 1 illustrates that treating biomass materials with a water-soluble organic solution has a significant impact on the specific surface area and battery performance of the final hard carbon material, and that the water-soluble organic solution is very important for the final product.

[0148] Comparative Example 2 illustrates that during the pre-carbonization roasting process of biomass materials, a certain amount of oxygen is present, and the controlled oxidation of the materials plays an important role in the sodium storage capacity and initial efficiency of the final hard carbon materials.

[0149] Comparative Examples 3 and 4 demonstrate that polymer materials can significantly affect the pore size distribution range and specific surface area of ​​the final product, ultimately having a significant impact on the performance of the final product. The performance of the final product prepared by adding too much polymer material or not adding polymer composite material differs greatly from that of the examples.

[0150] Comparative Example 5 shows that if the high-temperature carbonization roasting temperature is too low, the material cannot form an effective sodium storage structure at the microscopic level, and impurities cannot be effectively removed, resulting in poor material performance.

[0151] Comparative Examples 6 and 7 demonstrate that adding a certain amount of carbon-containing source gas during the calcination process can significantly improve the microporous structure of the material, affect its specific surface area and micropore size range, and play an important role in improving the sodium storage performance of the final product.

[0152] The raw materials and manufacturing process of this invention are low-cost, significantly reducing the cost of hard carbon materials. Multiple innovative processes, including water-soluble organic solution pretreatment, oxygen-containing atmosphere pre-carbonization, and high-temperature carbonization using a mixed atmosphere of carbon source gas and inert gas, improve the initial coulombic efficiency of hard carbon materials. The resulting material, when used as a negative electrode in sodium-ion pouch batteries, exhibits high energy density. This invention demonstrates significant beneficial effects.

Claims

1. A method for preparing hard carbon materials from biomass materials and polymers, comprising the following steps: 1) Soak biomass material blocks with a particle size or length of 10-60 mm in a water-soluble organic solution at 70-100℃ for 1-6 hours; 2) Place the biomass material blocks treated in step 1) into a heating furnace for pre-firing. The pre-firing atmosphere is an oxygen-containing atmosphere, which is a mixture of oxygen and an inert gas, namely nitrogen or argon, or a mixture of two of them. The oxygen volume percentage in the atmosphere is 2-11%. The temperature is raised from room temperature to the pre-firing temperature at a rate of 1-15℃ / min, the temperature is stopped at 500-800℃, and the holding time is 1-5h to obtain pre-carbonized biomass material. The gas space velocity of the oxygen-containing atmosphere is 30-220mL / min / g. The carbon yield of the treated biomass material is controlled to be 15-50%. Carbon yield = dry weight of pre-carbonized biomass material after pre-firing / dry weight of biomass material before pre-firing. 3) Crush the pre-carbonized biomass material blocks from step 2) into powder with a particle size of 5~75μm; 4) Add polymer and curing agent to the pre-carbonized biomass material powder obtained in step 3), mix evenly, and after solidification, cut into blocks with a particle size of 20~60mm. Let it stand in a vacuum oven to solidify and obtain pre-carbonized biomass material powder and polymer composite. 5) The blocky composite from step 4) is subjected to high-temperature carbonization calcination to obtain hard carbon material. The calcination process is as follows: first, the temperature is increased from room temperature to 700-950℃ at a rate of 2-20℃ / min and held for 1-5 hours; then, the temperature is increased to 1000-1500℃ at a rate of 1-10℃ / min and held for 1-5 hours; then, the temperature is naturally cooled to room temperature to obtain blocky hard carbon material. The entire high-temperature carbonization and roasting process is carried out in a mixed atmosphere of inert gas and carbon source gas; The inert gas is one or a mixture of nitrogen and argon, and the carbon source gas is one or more of blast furnace gas, coke gas, carbon monoxide, methane, ethane, propane, n-butane, isobutane, ethylene, propylene, n-butene, isobutene, butadiene, cis-dibutene, trans-dibutene, cyclopropane, acetylene, and propyne, wherein the volume percentage of the carbon source gas is 5-70%; the gas space velocity of the mixture is 5-100 mL / min / g. The mass ratio of the polymer to the pre-carbonized biomass material is 1:4 to 7:3; Step 1) The water-soluble organic matter includes one or more of the following: polysaccharides, disaccharides, monosaccharides, carboxymethyl starch, acetic acid starch, hydroxymethyl cellulose, polyacrylamide, and polyvinylpyrrolidone. The mass concentration of the organic matter in the aqueous solution is 5-50%.

2. The method according to claim 1, characterized in that: The blocky hard carbon material obtained in step 5) is crushed, ball-milled, air-jet pulverized and sieved to obtain a hard carbon material product; the particle size of the hard carbon material product is 0.5~8μm.

3. The method according to claim 1, characterized in that: Step 1) The biomass materials include one or a mixture of several of the following: wood, bamboo, walnut shells, pine nut shells, peanut shells, coconut shells, straw, lignin, cellulose, hemicellulose, and starch.

4. The method according to claim 1, characterized in that: Step 4) The polymer is one or more of liquid epoxy resin, acrylic resin, polyurethane, and phenolic resin. The curing agent is an amine curing agent or an anhydride curing agent. The amount of curing agent added is 5-60% of the polymer mass. The curing temperature is 25-160℃ and the time is 2-24h.

5. The method according to claim 4, characterized in that: The curing agent is one or more of polyamide, ethylenediamine, diethylenetriamine, fatty amine, and phthalic anhydride.

6. The method according to claim 1, characterized in that: Step 5) The volume composition of the blast furnace gas is 20-40% carbon monoxide, 50-70% nitrogen, and 1-10% carbon dioxide; the volume composition of the coking gas is 45-60% hydrogen, 30-45% methane, 5-10% carbon monoxide, and 1-10% carbon dioxide.

7. A hard carbon material product prepared by any one of claims 1-6.

8. The hard carbon material product according to claim 7, characterized in that: The pore size distribution of hard carbon materials ranges from 0.1 to 20 nm, with an average pore size ranging from 0.3 to 8 nm; the specific surface area ranges from 1 to 30 m². 2 / g.

9. The application of the hard carbon material according to any one of claims 7-8 as a negative electrode active material in a sodium-ion battery.

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