Preparation method of hard carbon negative electrode material, hard carbon negative electrode material and application of hard carbon negative electrode material

Abstract

The invention provides a preparation method of a hard carbon negative electrode material, the hard carbon negative electrode material and application of the hard carbon negative electrode material. The preparation method of the hard carbon negative electrode material comprises the following steps: mixing bagasse and epoxypropane waste residue, and adding water to prepare precursor slurry; introducing saccharomyces cerevisiae into the precursor slurry, adding trisodium citrate, ammonium dihydrogen phosphate, soluble calcium salt and urea, and performing shake culture under certain culture conditions to obtain composite slurry containing a biomineralization template; dropwise adding a hydrogen peroxide solution into the composite slurry, performing an oxidation reaction at a certain temperature, performing freeze drying, and performing pre-carbonization at a first temperature to obtain a pre-carbonized product; and crushing the pre-carbonized product, soaking the crushed pre-carbonized product in diluted hydrochloric acid to remove the biomineralization template, and carbonizing the pre-carbonized product at a second temperature which is higher than the first temperature after the pre-carbonized product is treated to be neutral. According to the preparation method, the synergistic advantage of agricultural / industrial double solid wastes is combined, and the doping of phosphorus and nitrogen can be regulated and controlled in a biomineralization-in-situ oxidation synergistic mode, so that the defects of high template removal energy consumption, poor doping uniformity and insufficient raw material economy in the traditional hard carbon material preparation are overcome; therefore, the hard carbon negative electrode material with high capacity, high first efficiency and high rate performance is prepared.

Description

[0001] Preparation methods of hard carbon anode materials, hard carbon anode materials and their applications Technical Field This invention relates to the field of new energy material preparation technology, and in particular to the preparation method of hard carbon anode material, hard carbon anode material and its application. Background Technology

[0002] In order to break through the industrialization bottleneck of sodium-ion batteries, it is necessary to achieve breakthroughs in "high capacity, high first-time efficiency, and high rate" with hard carbon anode materials. The industry usually adopts the template method to prepare hard carbon anode materials. It uses templates with specific structures (such as hard templates and soft templates) to control the morphology and pore structure of carbon materials. Through the three steps of "template construction - carbon source filling / coating - template removal", hard carbon materials are prepared. Hard carbon materials prepared by the template method have at least the following advantages: (1) Strong structural controllability: The pore size, pore order, and morphology of hard carbon materials can be precisely controlled to adapt to different application scenarios. (2) High specific surface area: The prepared hard carbon materials usually have rich porous structures, and the specific surface area can reach 500~2000m². 2 / g, can provide more ion adsorption / desorption sites and improve lithium / sodium storage capacity. (3) Stable performance: The formation of an ordered pore structure can suppress the volume expansion of hard carbon materials during charging and discharging, and improve cycle stability (especially when used as a battery anode material, the cycle life is better than that of traditional carbonized hard carbon).

[0003] However, existing technologies for preparing hard carbon anode materials still face three major challenges: First, template methods rely on high-temperature calcination (e.g., salt templates require treatment above 800℃) or strong acid / base removal, which are energy-intensive and easily damage the pore structure. Second, elemental doping modification often employs high-temperature gas-phase doping (e.g., NH3, PH3), which is a dangerous process with poor doping uniformity. Third, precursors are mostly single biomass or resins, resulting in insufficient raw material economics. Therefore, developing a new technology for preparing doped hard carbon materials with low energy consumption, high safety, and widely available raw materials has become a critical need. Summary of the Invention

[0004] In view of the above problems, the purpose of this invention is to provide a method for preparing hard carbon anode materials, hard carbon anode materials, and their applications. This preparation method combines the synergistic advantages of agricultural / industrial solid waste, and utilizes the synergistic mechanism of biomineralization-in-situ oxidation to regulate phosphorus and nitrogen doping, thereby overcoming the defects of high energy consumption for template removal, poor doping uniformity, and insufficient raw material economy in the preparation of traditional hard carbon materials, thus preparing hard carbon anode materials with high capacity, high initial efficiency, and high rate performance.

[0005] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a hard carbon anode material, comprising the steps of: (I) Preparation of precursor slurry Sugarcane bagasse and propylene oxide waste were mixed with water to prepare a precursor slurry. (II) Construction of biomineralization templates Saccharomyces cerevisiae was introduced into the precursor slurry, and trisodium citrate, ammonium dihydrogen phosphate, soluble calcium salt and urea were added. The mixture was then shaken and cultured under certain culture conditions to obtain a composite slurry containing a biomineralization template. (III) Oxidation and Precarbonization Hydrogen peroxide solution is added dropwise to the composite slurry, and after oxidation reaction at a certain temperature, it is freeze-dried and then pre-carbonized at a first temperature to obtain a pre-carbonized product. (IV) De-dusting and carbonization The pre-carbonized product was pulverized and then soaked in dilute hydrochloric acid to remove the biomineralization template. After reaching neutrality, carbonization is carried out at a second temperature, which is higher than the first temperature.

[0006] This invention combines the synergistic advantages of agricultural and industrial solid waste, utilizing a synergistic approach of biomineralization and in-situ oxidation to regulate phosphorus and nitrogen doping, overcoming the shortcomings of traditional hard carbon material preparation, such as high energy consumption for template removal, poor doping uniformity, and insufficient raw material economy. Through three process designs—"mild and removable templates through biomineralization," "precise regulation of defects through in-situ oxidation," and "atomic-level dispersion of phosphorus and nitrogen dual doping"—a hard carbon anode material with high capacity, high initial efficiency, and high rate performance is prepared. Its specific performance is as follows.

[0007] (1) Through the metabolic action of Saccharomyces cerevisiae, ammonium dihydrogen phosphate and soluble calcium salts are converted into nano-hydroxycalcium phosphate templates. Urea not only provides a nitrogen source for the growth of Saccharomyces cerevisiae but also adjusts the metabolic pH, maintaining a stable metabolic environment. After shaking culture, the hydroxyl and amino groups on the cell wall surface hydrolyze with the soluble calcium salts to generate Ca2+. 2+ PO4 generated by the dissociation of ammonium dihydrogen phosphate 3- The hydroxyapatite nanoparticles are then combined and adsorbed onto the crystal surface via chelation with trisodium citrate to create steric hindrance, preventing further particle growth and thus inhibiting agglomeration. This results in in-situ grown hydroxyapatite nanoparticles. The hydroxyapatite nanoparticle template is constructed through biomineralization, requiring no high-temperature pretreatment and can be gently removed subsequently with dilute hydrochloric acid.

[0008] (2) Hydrogen peroxide solution is added dropwise to the composite slurry. The •OH free radicals generated by the decomposition of hydrogen peroxide can selectively oxidize the hydroxyl groups of sugarcane bagasse cellulose and the polyether segments of propylene oxide waste to form appropriate carbon skeleton defects, thereby achieving in-situ oxidation and precise control of defects. The formed carbon skeleton defects can provide active adsorption sites for sodium ions on the one hand, and promote the doping and binding of phosphorus and nitrogen elements on the other hand, so as to improve the phosphorus and nitrogen doping rate.

[0009] (3) In the process of constructing biomineralization templates, ammonium dihydrogen phosphate and urea can not only be used as mineralization raw materials, but the P and N elements contained therein can also form CP and CN bonds with carbon skeleton precursors through yeast metabolism. Subsequently, P and N elements can be further fixed by freeze drying and low temperature pre-carbonization, which can avoid the unevenness caused by high temperature gas phase doping and finally achieve atomic-level dispersion of phosphorus and nitrogen.

[0010] (4) Freeze-drying and low-temperature pre-carbonization can fix the carbon skeleton structure. After crushing, the template of hydroxyapatite nanoparticles is removed by dilute hydrochloric acid. Finally, high-temperature carbonization is carried out to form a stable hard carbon material. This processing sequence can avoid the collapse of the pore structure caused by "removing the template first and then carbonizing". At the same time, it can maintain a suitable interlayer spacing and adapt to the insertion / extraction of sodium ions.

[0011] (5) Sugarcane bagasse, which is an agricultural waste, and propylene oxide waste, which is an industrial by-product, are selected as hard carbon raw materials. Propylene oxide waste is rich in polyether segments. After the two are mixed, the cellulose skeleton of sugarcane bagasse provides attachment sites for biomineralization. The polyether segments of propylene oxide waste can improve the flexibility of carbon materials and avoid brittleness after carbonization. The two can work together to solve the structural or performance defects of a single raw material.

[0012] In some embodiments, the bagasse is crushed to 0.5-2.0 mm before mixing.

[0013] In some embodiments, the carbon content of the propylene oxide waste residue is ≥65 wt.%.

[0014] In some embodiments, the propylene oxide waste residue is dried at 100-120°C for 8-12 hours before mixing.

[0015] In some embodiments, the mass ratio of the bagasse to the propylene oxide waste is 2 to 4:1.

[0016] In some embodiments, the solid content of the precursor slurry is 15-25%.

[0017] In some implementations, the specific culture conditions are a temperature of 30-35°C, a pH of 6.0-7.0, a shaking culture time of 24-48 hours, and a shaking speed of 200-250 rpm.

[0018] In some embodiments, the amount of brewer's yeast inoculated is 5 to 10 wt. of the precursor slurry.

[0019] In some embodiments, the ammonium dihydrogen phosphate accounts for 5 to 8 wt.% of the precursor slurry.

[0020] In some embodiments, the soluble calcium salt is at least one of calcium chloride and calcium sulfate.

[0021] In some embodiments, the soluble calcium salt accounts for 5 to 8 wt.% of the precursor slurry.

[0022] In some embodiments, the urea accounts for 3 to 5 wt.% of the precursor slurry.

[0023] In some embodiments, the trisodium citrate accounts for 0.1 to 0.3 wt.% of the precursor slurry.

[0024] In some implementations, the particle size of the biomineralization template is 20-50 nm.

[0025] In some embodiments, the concentration of the hydrogen peroxide solution is 20-45 wt.%.

[0026] In some embodiments, the hydrogen peroxide solution accounts for 8 to 12 wt.% of the precursor slurry.

[0027] In some embodiments, the oxidation reaction takes 1 to 2 hours and the specific temperature is 40 to 50°C.

[0028] In some embodiments, the freeze-drying temperature is -40 to -30°C, the vacuum degree is ≤10 Pa, and the time is... It lasts for 12 to 24 hours.

[0029] In some implementations, the first temperature is 450~650°C, and the second temperature is 1100~1500°C.

[0030] In some embodiments, the pulverization is performed by air jet milling to a particle size Dv50 of 4~6μm.

[0031] In some embodiments, the concentration of the dilute hydrochloric acid is 0.5~1.0 mol / L.

[0032] In some embodiments, the soaking temperature is 50~60°C and the soaking time is 4~6 hours. In some embodiments, the liquid-to-solid ratio of the dilute hydrochloric acid to the pre-carbonized product is 10-15:1.

[0033] In some implementations, the removal rate of the biomineralized template is ≥98%.

[0034] In some embodiments, the pre-carbonized product is soaked in dilute hydrochloric acid, washed, and filtered until neutral.

[0035] In some embodiments, the pre-carbonization is carried out under an inert atmosphere for a time of 0.5 to 3.0 hours.

[0036] In some embodiments, the inert atmosphere is selected from at least one of nitrogen, argon, helium and neon, and the flow rate is 200~450 mL / min.

[0037] In some embodiments, the heating rate of the pre-carbonization is 2~10℃ / min.

[0038] In some embodiments, the carbonization is carried out under an inert atmosphere for 2 to 10 hours.

[0039] In some embodiments, the inert atmosphere is selected from at least one of nitrogen, argon, helium and neon, and the flow rate is 200~450 mL / min.

[0040] In some embodiments, the heating rate of the carbonization is 2~4°C / min.

[0041] A second aspect of this invention provides a hard carbon anode material with a particle size of 4-6 μm and a specific surface area of ​​3-7 m². 2 / g, phosphorus doping concentration of 1.2~2.0 wt.%, nitrogen doping concentration of 0.8~1.5 wt.%, interlayer spacing d 002 The wavelength range is 0.37~0.40 nm, the average pore size is 5.0~20.0 nm, and the pore volume is 0.005~0.014 cm³. 3 / g.

[0042] The third aspect of this invention provides an application of a hard carbon anode material as an anode material, which has a first reversible capacity of 350~380mAh / g at 0.2C, a first coulombic efficiency of 85~88%, a capacity retention rate of ≥72% at 3C / 0.2C, and a capacity decay rate of ≤7% after 1000 cycles at 0.2C. Detailed Implementation

[0043] The hard carbon anode material of this invention can be used alone or in combination with other anode active materials (such as natural graphite, silicon oxide materials, silicon carbon materials, soft carbon, and / or hard carbon). The hard carbon anode material can be applied in secondary batteries, which include positive and negative electrode active materials. The positive electrode active material includes at least one of lithium cobalt oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0044] The hard carbon anode material of this invention, when used as an anode material in sodium-ion batteries, exhibits an initial reversible capacity of 350-380 mAh / g at 0.2C. Examples, but not limited to, 350 mAh / g, 355 mAh / g, 360 mAh / g, 365 mAh / g, 370 mAh / g, 375 mAh / g, and 380 mAh / g. The initial coulombic efficiency is 85-88%, examples, but not limited to, 85%, 86%, 87%, and 88%. The 3C / 0.2C capacity retention rate is ≥72%, examples, but not limited to, ≥72%, ≥74%, ≥76%, ≥78%, and ≥80%. The capacity decay rate after 1000 cycles at 0.2C is ≤7%, examples, but not limited to, ≤7%, ≤6%, ≤5%, ≤4%, ≤3%, ≤2%, and ≤1%.

[0045] The particle size of the hard carbon anode material is 4~6μm; for example, it can be, but is not limited to, 4μm, 5μm, or 6μm. The specific surface area is 3~7m². 2 / g, as an example, can be, but is not limited to, 3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g. Doping concentration is 1.2~2.0 wt.%, and for example, it can be, but is not limited to, 1.2 wt.%, 1.3 wt.%, 1.4 wt.%, 1.5 wt.%, 1.6 wt.%, 1.7 wt.%, 1.8 wt.%, 1.9 wt.%, 2.0 wt.%. Nitrogen doping concentration is 0.8~1.5 wt.%, and for example, it can be, but is not limited to, 0.8 wt.%, 0.9 wt.%, 1.0 wt.%, 1.1 wt.%, 1.2 wt.%, 1.3 wt.%, 1.4 wt.%, 1.5 wt.%. Interlayer spacing d 002 The pore size is 0.37~0.40 nm, and for example, it can be, but is not limited to, 0.37 nm, 0.38 nm, 0.39 nm, and 0.40 nm. The average pore size is 5.0~20.0 nm, and for example, it can be, but is not limited to, 5.0 nm, 6.0 nm, 6.5 nm, 7.0 nm, 7.5 nm, 8.0 nm, 8.5 nm, 9.0 nm, 10.0 nm, 11.0 nm, 12.0 nm, 13.0 nm, 14.0 nm, 15.0 nm, 16.0 nm, 17.0 nm, 18.0 nm, 19.0 nm, and 20.0 nm, with a pore volume of 0.005~0.014 cm³. 3 / g, as an example, can be, but is not limited to, 0.005cm 3 / g, 0.006cm 3 / g, 0.007cm3 / g, 0.008cm 3 / g, 0.009cm 3 / g, 0.010cm 3 / g, 0.011cm 3 / g, 0.012cm 3 / g, 0.013cm 3 / g, 0.014cm 3 / g.

[0046] The preparation method of the hard carbon anode material of the present invention may include the following steps.

[0047] (I) Preparation of precursor slurry Sugarcane bagasse and propylene oxide waste were mixed with water to make a precursor slurry.

[0048] (II) Construction of biomineralization templates Saccharomyces cerevisiae was introduced into the precursor slurry, and trisodium citrate, ammonium dihydrogen phosphate, soluble calcium salt and urea were added. The mixture was then shaken and cultured under certain conditions to obtain a composite slurry containing a biomineralization template.

[0049] (III) Oxidation and Precarbonization Hydrogen peroxide solution is added dropwise to the composite slurry, and after oxidation reaction at a certain temperature, it is freeze-dried and then pre-carbonized at a first temperature to obtain a pre-carbonized product.

[0050] (IV) De-dusting and carbonization The pre-carbonized product was pulverized and then soaked in dilute hydrochloric acid to remove the biomineralization template. After treatment until neutral, it was then... Carbonization is carried out at a second temperature, which is higher than the first temperature.

[0051] In step (I), the bagasse is crushed to a particle size of 0.5-2.0 mm before mixing. For example, the particle size can be, but is not limited to, 0.5 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm, or 2.0 mm. The propylene oxide waste residue is dried at 100-120°C for 8-12 hours before mixing. The carbon content of the propylene oxide waste residue is ≥65 wt.%. For example, the carbon content can be, but is not limited to, 65 wt.%, 66 wt.%, 67 wt.%, 68 wt.%, 69 wt.%, 70 wt.%, 71 wt.%, 72 wt.%, 73 wt.%, 74 wt.%, 75 wt.%, 76 wt.%, 77 wt.%, 78 wt.%, 79 wt.%, or 80 wt.%. The mass ratio of bagasse to propylene oxide waste is 2-4:1, and for example, it can be, but is not limited to, 2:1, 3:1, or 4:1. The solid content of the precursor slurry is 15-25%, and for example, it can be, but is not limited to, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, or 25%.

[0052] In step (II), the specific culture conditions for the brewing yeast are a temperature of 30-35℃ and a pH of 6.0-7.0. For example, the temperature can be, but is not limited to, 30℃, 31℃, 32℃, 33℃, 34℃, or 35℃, and the pH can be 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, or 7.0. The shaking culture time is 24-48 hours. For example, the time can be, but is not limited to, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, 36 hours, 38 hours, 40 hours, 42 hours, 44 hours, 46 hours, or 48 hours. The shaking speed is 200-250 rpm. For example, the shaking speed can be, but is not limited to, 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, or 250 rpm. The inoculation amount of brewer's yeast is 5 to 10 wt.% of the precursor slurry. For example, the inoculation amount can be, but is not limited to, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, or 10 wt.%.

[0053] Ammonium dihydrogen phosphate comprises 5-8 wt.% of the precursor slurry. For example, the amount of ammonium dihydrogen phosphate may be, but is not limited to, 5 wt.%, 6 wt.%, 7 wt.%, or 8 wt.%. The soluble calcium salt is at least one of calcium chloride and calcium sulfate, comprising 5-8 wt.% of the precursor slurry. For example, the amount of soluble calcium salt may be, but is not limited to, 5 wt.%, 6 wt.%, 7 wt.%, or 8 wt.%. Urea comprises 3-5 wt.% of the precursor slurry. For example, the amount of urea may be, but is not limited to, 3 wt.%, 4 wt.%, or 5 wt.%. Trisodium citrate comprises 0.1-0.3 wt.% of the precursor slurry. For example, the amount of trisodium citrate may be, but is not limited to, 0.1 wt.%, 0.2 wt.%, or 0.3 wt.%. The obtained biomineralized template has a particle size of 20~50nm. For example, the particle size can be, but is not limited to, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, and 50nm.

[0054] In step (III), the concentration of the hydrogen peroxide solution is 20-45 wt.%, and for example, the concentration may be, but is not limited to, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, or 45 wt.%. The hydrogen peroxide solution accounts for 8-12 wt.% of the precursor slurry, and for example, the amount of hydrogen peroxide solution may be, but is not limited to, 8 wt.%, 9 wt.%, 10 wt.%, 11 wt.%, or 12 wt.%.

[0055] The oxidation reaction takes 1-2 hours; for example, the time may be, but is not limited to, 1 hour or 2 hours. The oxidation reaction temperature is 40-50°C; for example, the temperature may be, but is not limited to, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, or 50°C. The freeze-drying temperature is -40 to -30°C, the vacuum degree is ≤10 Pa, and the time is 12-24 hours.

[0056] Furthermore, pre-carbonization is carried out under an inert atmosphere, selected from at least one of nitrogen, argon, helium, and neon, with a flow rate of 200–450 mL / min. Examples, but not limited to, flow rates of 200 mL / min, 220 mL / min, 240 mL / min, 260 mL / min, 280 mL / min, 300 mL / min, 320 mL / min, 340 mL / min, 360 mL / min, 380 mL / min, 400 mL / min, 420 mL / min, and 450 mL / min are possible. The pre-carbonization time is 0.5–3.0 h. Examples, but not limited to, 0.5 h, 1.0 h, 1.5 h, 2.0 h, 2.5 h, and 3.0 h are possible. The pre-carbonization temperature is 450~650℃. For example, the temperature may be, but is not limited to, 450℃, 470℃, 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, 620℃, 640℃, and 650℃. The pre-carbonization heating rate is 2~10℃ / min. For example, the heating rate may be, but is not limited to, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 90℃ / min, and 10℃ / min.

[0057] In step (IV), the pulverization is performed using air jet milling to a particle size Dv50 of 4–6 μm. The concentration of dilute hydrochloric acid used for descaling is 0.5–1.0 mol / L; for example, the concentration may be, but is not limited to, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, or 1.0 mol / L. The soaking temperature is 50–60°C; for example, the temperature may be, but is not limited to, 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, or 60°C. The soaking time is 4–6 hours; for example, the time may be, but is not limited to, 4 hours, 5 hours, or 6 hours. The liquid-to-solid ratio of dilute hydrochloric acid to the pre-carbonized product is 10-15:1. For example, the liquid-to-solid ratio can be, but is not limited to, 10:1, 11:1, 12:1, 13:1, 14:1, or 15:1. The removal rate of the biomineralized template after acid washing is ≥98%. The pre-carbonized product is soaked in dilute hydrochloric acid, washed, and then filtered until neutral.

[0058] Carbonization is carried out under an inert atmosphere, selected from at least one of nitrogen, argon, helium, and neon, with a flow rate of 200–450 mL / min. Examples, but not limited to, flow rates of 200 mL / min, 220 mL / min, 240 mL / min, 260 mL / min, 280 mL / min, 300 mL / min, 320 mL / min, 340 mL / min, 360 mL / min, 380 mL / min, 400 mL / min, 420 mL / min, and 450 mL / min are possible. The carbonization time is 2–10 h. Examples, but not limited to, are 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, and 10 h. The carbonization temperature is 1100~1500℃. For example, the temperature may be, but is not limited to, 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, 1450℃, and 1500℃. The carbonization heating rate is 2~4℃ / min. For example, the heating rate may be, but is not limited to, 2℃ / min, 3℃ / min, and 4℃ / min.

[0059] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below in conjunction with specific embodiments. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting it. The embodiments of this invention include descriptions of the technical solution for hard carbon anode materials and descriptions of the technical solution for preparing hard carbon anode materials.

[0060] Example 1 This embodiment describes a method for preparing a hard carbon anode material, which includes the following steps.

[0061] (I) Preparation of precursor slurry Sugarcane bagasse pulverized to 1.0~1.5mm and propylene oxide waste residue dried at 110℃ for 10h (the carbon content of the propylene oxide waste residue is 70wt.%) were mixed at a mass ratio of 1:1 and then water was added to prepare a precursor slurry with a solid content of 20%.

[0062] (II) Construction of biomineralization templates A composite slurry containing a biomineralized template was obtained by introducing 4 wt.% of Saccharomyces cerevisiae into the precursor slurry and adding 0.3 wt.% trisodium citrate, 4 wt.% ammonium dihydrogen phosphate, 6 wt.% calcium chloride and 2 wt.% urea. The slurry was cultured at 32℃ and pH 6.5 with vibration at 250 rpm for 36 h.

[0063] (III) Oxidation and Precarbonization A 30 wt.% hydrogen peroxide solution was added dropwise to the composite slurry at a ratio of 8 wt.%, and the mixture was oxidized at 45 °C for 1.5 h. Then, it was freeze-dried at -35 °C and 5 Pa for 18 h. Under nitrogen protection (flow rate of 300 mL / min), the temperature was increased to 500 °C at 5 °C / min and held for 2.0 h to obtain the pre-carbonized product.

[0064] (IV) De-dusting and carbonization The pre-carbonized product was air-jet milled to a particle size Dv50 of 5 μm and then treated with 1.0 mol / L dilute hydrochloric acid (liquid). The sample (solid-to-solid ratio 12:1) was soaked at 55℃ for 5 hours to remove the biomineralized template (removal rate 99%). After washing and filtration to neutrality, it was placed in a forced-air drying oven and dried at 100℃ for 12 hours. Then, it was heated to 1200℃ at 3℃ / min and held in a tube furnace under a nitrogen atmosphere (flow rate 300mL / min) for 4 hours. The only difference between Examples 2-5 and Example 1 is that the mass ratio of bagasse and propylene oxide waste is 2:1, 3:1, 4:1, and 5:1, respectively.

[0065] The only difference between Examples 6-9 and Example 1 is that the inoculation amount of Saccharomyces cerevisiae is 5 wt.%, 8 wt.%, 10 wt.%, and 11 wt.%, respectively.

[0066] The only difference between Examples 10-13 and Example 1 is that the proportions of ammonium dihydrogen phosphate are 5 wt.%, 7 wt.%, 8 wt.%, and 9 wt.%, respectively.

[0067] The difference between Examples 14-17 and Example 1 is that the proportion of ammonium dihydrogen phosphate is 7 wt.% and the proportion of urea is 3 wt.%, 4 wt.%, 5 wt.%, and 6 wt.%, respectively.

[0068] The difference between Examples 18-20 and Example 1 is that the proportion of ammonium dihydrogen phosphate is 7 wt.% in all examples, the proportion of urea is 4 wt.% in all examples, and the proportions of hydrogen peroxide solution with a concentration of 30 wt.% are 10 wt.%, 12 wt.%, and 13 wt.%, respectively.

[0069] The difference between Examples 21-24 and Example 1 is that the proportion of ammonium dihydrogen phosphate is 7 wt.% and the proportion of urea is... The proportions of hydrogen peroxide solution with a concentration of 4 wt.% and 30 wt.% were all 10 wt.%, and the liquid-solid ratios of dilute hydrochloric acid and pre-carbonized products were 10:1, 13:1, 15:1, and 16:1.

[0070] The difference between Example 25 and Example 1 is that the mass ratio of bagasse to propylene oxide waste is 3:1, the inoculation amount of brewer's yeast is 7.5 wt.%, the proportion of ammonium dihydrogen phosphate is 6.5 wt.%, the proportion of urea is 4 wt.%, the proportion of 30 wt.% hydrogen peroxide solution is 10 wt.%, and the liquid-solid ratio of dilute hydrochloric acid to pre-carbonized products is 12.5:1.

[0071] Example 26 This embodiment describes a method for preparing a hard carbon anode material, which includes the following steps.

[0072] (I) Preparation of precursor slurry Sugarcane bagasse pulverized to 0.5~1.0 mm and propylene oxide waste residue dried at 120℃ for 8 hours (the carbon content of the propylene oxide waste residue is 75wt.%) were mixed at a mass ratio of 3:1 and then water was added to prepare a precursor slurry with a solid content of 23%.

[0073] (II) Construction of biomineralization templates A composite slurry containing a biomineralized template was obtained by introducing 4 wt.% of Saccharomyces cerevisiae into the precursor slurry and adding 0.2 wt.% trisodium citrate, 4 wt.% ammonium dihydrogen phosphate, 8 wt.% calcium sulfate and 2 wt.% urea. The slurry was cultured at 32℃ and pH 6.5 with vibration at 250 rpm for 36 h.

[0074] (III) Oxidation and Precarbonization A 40 wt.% hydrogen peroxide solution was added dropwise to the composite slurry at a ratio of 8 wt.%, and the mixture was oxidized at 50 °C for 2.0 h. Then, it was freeze-dried at -40 °C and 8 Pa for 24 h. Under nitrogen protection (flow rate of 250 mL / min), the temperature was increased to 500 °C at 5 °C / min and held for 2.0 h to obtain the pre-carbonized product.

[0075] (IV) De-dusting and carbonization The pre-carbonized product was air-jet milled to a particle size Dv50 of 5 μm and then treated with 0.8 mol / L dilute hydrochloric acid (liquid). The sample (solid-to-solid ratio 10:1) was soaked at 55℃ for 5 hours to remove the biomineralized template (removal rate 98%). After washing and filtration to neutrality, it was placed in a forced-air drying oven and dried at 100℃ for 12 hours. Then, it was heated to 1200℃ at 3℃ / min and held in a tube furnace under a nitrogen atmosphere (flow rate 350mL / min) for 4 hours. Example 27 This embodiment describes a method for preparing a hard carbon anode material, which includes the following steps.

[0076] (I) Preparation of precursor slurry Sugarcane bagasse pulverized to 1.0~1.5mm and propylene oxide waste residue dried at 120℃ for 8h (the carbon content of the propylene oxide waste residue is 68wt.%) were mixed at a mass ratio of 1:1 and then water was added to prepare a precursor slurry with a solid content of 25%.

[0077] (II) Construction of biomineralization templates A composite slurry containing a biomineralized template was obtained by introducing 4 wt.% of Saccharomyces cerevisiae into the precursor slurry and adding 0.3 wt.% trisodium citrate, 4 wt.% ammonium dihydrogen phosphate, 7 wt.% calcium chloride and 2 wt.% urea. The slurry was cultured at 35°C and pH 7.0 with vibration at 200 rpm for 30 h.

[0078] (III) Oxidation and Precarbonization A 30 wt.% hydrogen peroxide solution with an 8 wt.% concentration was added dropwise to the composite slurry. After oxidation at 60℃ for 2.0 h, the mixture was freeze-dried at -35℃ and 5 Pa for 18 h. Under nitrogen protection (flow rate of 300 mL / min), the temperature was increased to 600℃ at 8℃ / min and held for 3.0 h to obtain the pre-carbonized product.

[0079] (IV) De-dusting and carbonization The pre-carbonized product was pulverized by air jet milling to a particle size Dv50 of 4 μm and then treated with 1.0 mol / L dilute hydrochloric acid (liquid). The sample (solid-to-solid ratio 12:1) was soaked at 55℃ for 5 hours to remove the biomineralized template (removal rate 99%). After washing and filtration to neutrality, it was placed in a forced-air drying oven and dried at 100℃ for 12 hours. Then, it was heated to 1400℃ at 4℃ / min and held in a tube furnace under a helium atmosphere (flow rate 320mL / min) for 8 hours. Comparative Example 1 This comparative example illustrates a method for preparing a hard carbon anode material, comprising the following steps.

[0080] (I) Preparation of precursors Use a universal crusher to crush pure sugarcane bagasse into 1.5mm particles to obtain crushed material.

[0081] (II) Pre-carbonization The crushed material was placed in a tubular furnace and heated to 500℃ at a rate of 5℃ / min under nitrogen protection (flow rate of 300 mL / min) and held for 2.0 h. Pre-carbonized products are obtained.

[0082] (III) De-dusting and carbonization The pre-carbonized product was pulverized by air jet milling to a particle size Dv50 of 5 μm and soaked in 1.0 mol / L dilute hydrochloric acid (liquid-solid ratio of 12:1) at 55 °C for 5 h. After washing and filtration to neutrality, it was placed in a forced-air drying oven and dried at 100 °C for 12 h. Then, it was heated to 1200 °C at 3 °C / min and held in a tube furnace under a nitrogen atmosphere (flow rate of 300 mL / min) for 4 h. Comparative Example 2 This comparative example illustrates a method for preparing a hard carbon anode material, comprising the following steps.

[0083] (I) Preparation of precursors Use a universal crusher to crush pure sugarcane bagasse into 1.5mm particles to obtain crushed material.

[0084] (II) Pre-carbonization The crushed material was placed in a tube furnace and heated to 500℃ at 5℃ / min under nitrogen protection (flow rate of 300mL / min) and held for 2.0h to obtain a pre-carbonized product. The pre-carbonized product was then pulverized by air jet milling to a particle size Dv50 of 5μm to obtain a fine powder.

[0085] (III) Vapor phase doping The ground powder was placed in a tube furnace, nitrogen gas was introduced, and the temperature was raised to 800°C at a rate of 5°C / min. Then NH3 gas was introduced, with a total flow rate of 300 mL / min (the volume ratio of NH3 to nitrogen was 1:2). The temperature was maintained at 800°C for 3 hours. After doping was completed, the introduction of NH3 was stopped, and nitrogen gas was introduced again until the tube furnace cooled to room temperature to obtain nitrogen-doped material.

[0086] (IV) De-dusting and carbonization Soak in 1.0 mol / L dilute hydrochloric acid (liquid-solid ratio of 12:1) at 55℃ for 5 h, wash and filter until neutral, place in a forced-air drying oven and dry at 100℃ for 12 h, then heat to 1200℃ in a tube furnace under nitrogen atmosphere at 3℃ / min and hold for 4 h. Comparative Example 3 This comparative example illustrates a method for preparing a hard carbon anode material, comprising the following steps.

[0087] (I) Preparation of precursor slurry Sugarcane bagasse pulverized to 1.0~1.5mm and propylene oxide waste residue dried at 110℃ for 10h (the carbon content of the propylene oxide waste residue is 70wt.%) were mixed at a mass ratio of 1:1 and then water was added to prepare a precursor slurry with a solid content of 20%.

[0088] (II) Construction of biomineralization templates A composite slurry containing a biomineralized template was obtained by introducing 4 wt.% of Saccharomyces cerevisiae into the precursor slurry and adding 0.3 wt.% trisodium citrate, 4 wt.% ammonium dihydrogen phosphate, 6 wt.% calcium chloride and 2 wt.% urea. The slurry was cultured at 32℃ and pH 6.5 with vibration at 250 rpm for 36 h.

[0089] (III) Pre-carbonization The composite slurry was freeze-dried at -35℃ and 5Pa for 18 hours, and then heated to 500℃ at 5℃ / min and held for 2.0 hours under nitrogen protection to obtain the pre-carbonized product.

[0090] (IV) De-dusting and carbonization The pre-carbonized product was air-jet milled to a particle size Dv50 of 5 μm and then treated with 1.0 mol / L dilute hydrochloric acid (liquid). The sample (solid-to-solid ratio 12:1) was soaked at 55℃ for 5 hours to remove the biomineralized template (removal rate 99%). After washing and filtration to neutrality, it was placed in a forced-air drying oven and dried at 100℃ for 12 hours. Then, it was heated to 1200℃ in a tube furnace under nitrogen atmosphere at 3℃ / min and held for 4 hours. Comparative Example 4 This comparative example illustrates a method for preparing a hard carbon anode material, comprising the following steps.

[0091] (I) Preparation of precursor slurry Sugarcane bagasse pulverized to 1.0~1.5mm and propylene oxide waste residue dried at 110℃ for 10h (the carbon content of the propylene oxide waste residue is 70wt.%) were mixed at a mass ratio of 1:1 and then water was added to prepare a precursor slurry with a solid content of 20%.

[0092] (II) Construction of biomineralization templates A composite slurry containing a biomineralized template was obtained by introducing 4 wt.% of Saccharomyces cerevisiae into the precursor slurry and adding 0.3 wt.% trisodium citrate, 4 wt.% ammonium dihydrogen phosphate, 6 wt.% calcium chloride and 2 wt.% urea. The slurry was cultured at 32℃ and pH 6.5 with vibration at 250 rpm for 36 h.

[0093] (III) Oxidation A 30 wt.% hydrogen peroxide solution was added dropwise to the composite slurry at a concentration of 8 wt.%, and the mixture was oxidized at 45°C for 1.5 h, followed by freeze-drying at -35°C and 5 Pa for 18 h.

[0094] (IV) De-dusting and carbonization The freeze-dried product was then air-jet milled to a particle size Dv50 of 5 μm and treated with 1.0 mol / L dilute salt. The biomineralized template was removed by soaking in acid (liquid-solid ratio of 12:1) at 55℃ for 5h (removal rate of 99%). After washing and filtration to neutrality, the sample was placed in a forced-air drying oven and dried at 100℃ for 12h. Then, it was heated to 1200℃ at 3℃ / min and held in a tube furnace under a nitrogen atmosphere (flow rate of 300mL / min) for 4h. The hard carbon anode materials prepared in Examples 1-27 and Comparative Examples 1-4 were tested for physical properties and chemical composition, and the results are shown in Table 1. The hard carbon anode materials prepared in Examples 1-27 and Comparative Examples 1-4 were tested for electrochemical performance, and the results are shown in Table 2.

[0095] (1) Physical properties and chemical composition testing Specific surface area, pore volume, and pore size distribution curves were obtained using nitrogen isothermal adsorption-desorption curves. The phosphorus and nitrogen atom percentages were obtained by EDS scanning of single and multi-particle elemental distributions, and the phosphorus and nitrogen doping amounts were calculated. The interlayer spacing d was measured using XRD. 002。 The particle size of the biomineralized templates prepared in Examples 1-27 and Comparative Examples 3-4 was determined by TEM.

[0096] (2) Electrochemical performance testing 0.2C Initial Discharge Capacity / Initial Coulombic Efficiency Test A polyvinylidene fluoride solution with a mass fraction of 6-7% was prepared using N-methylpyrrolidone as a solvent. The hard carbon anode materials prepared in Examples 1-27 and Comparative Examples 1-4, polyvinylidene fluoride, and conductive carbon black were mixed evenly at a mass ratio of 90:5:5. The mixture was coated onto copper foil and placed in a vacuum drying oven at 110°C for vacuum drying for 4 hours. The mixture was then punched into small round discs with a diameter of 14 mm. The cells were then transferred to an argon-filled glove box and assembled into 2430 coin cells. A 1 mol / L NaPF6 three-component mixed solvent (EC:DMC:EMC = 1:1:1, volume ratio) was used as the electrolyte. A sodium metal sheet was used as the counter electrode, and a 16 μm thick Ube membrane was used as the separator. The electrochemical performance of the assembled half-cells was tested using an electrochemical detection system. The charge / discharge voltage range was 0.001~2.8V. The test procedure was as follows: (1) rest for 6 hours; (2) 0.2C DC to 0V; (3) 0.15C DC to 0V; (4) 0.10C DC to 0V; (5) 0.08C DC to 0V; (6) 0.06C DC to 0V; (7) 0.05C DC to 0V; (8) 0.04C DC to 0V; (9) 0.03C DC to 0V; (10) 0.02C DC to 0V. 0V; (11) 0.015C DC to 0V; (12) 0.012C DC to 0V; (13) 0.01C DC to 0V; (14) 20µA DC to 0V; (15) 10µA DC to 0V; (16) Let stand for 5min; (17) 0.2C DC to 2V; (18) Let stand for 5min to end the test.

[0097] 3C / 0.2C Rate Capacity Retention Test The battery was assembled according to the half-charge test method in the 0.2C first discharge capacity performance test. First, 3 cycles of 0.2C formation were performed, and then tests were conducted at different rates of 0.5C, 1.0C and 3.0C. Finally, the percentage of sodium intercalation capacity at 3.0C rate to sodium intercalation capacity at the first cycle of 0.2C was taken as the 3C rate capacity retention rate.

[0098] 1000-cycle capacity decay rate test The battery was assembled according to the half-charge test method in the 0.2C first discharge capacity performance test, and 1000 cycles of 0.2C rate test were performed. The ratio of (capacity after 1000 cycles - capacity after the first cycle) / capacity after the first cycle was calculated as the capacity decay rate after 1000 cycles.

[0099] Table 1. Test results of physical properties and chemical composition of the hard carbon anode materials prepared in Examples 1-27 and Comparative Examples 1-4.

[0100] Table 2. Electrochemical performance test results of the hard carbon anode materials prepared in Examples 1-27 and Comparative Examples 1-4.

[0101] As shown in Table 1, the preparation method of the hard carbon anode material of the present invention combines the synergistic advantages of agricultural / industrial solid waste and utilizes the synergistic mode of biomineralization-in-situ oxidation to regulate the doping of phosphorus and nitrogen, and can prepare hard carbon anode materials with high capacity, high first efficiency and high rate performance.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a hard carbon anode material, characterized in that, Including the following steps: (I) Preparation of precursor slurry Sugarcane bagasse and propylene oxide waste were mixed with water to prepare a precursor slurry. (II) Construction of biomineralization templates Saccharomyces cerevisiae was introduced into the precursor slurry, and trisodium citrate, ammonium dihydrogen phosphate, soluble calcium salt and urea were added. The mixture was then shaken and cultured under certain culture conditions to obtain a composite slurry containing a biomineralization template. (III) Oxidation and Precarbonization Hydrogen peroxide solution is added dropwise to the composite slurry, and after oxidation reaction at a certain temperature, it is freeze-dried and then pre-carbonized at a first temperature to obtain a pre-carbonized product. (IV) De-dusting and carbonization The pre-carbonized product was pulverized and then soaked in dilute hydrochloric acid to remove the biomineralization template, and the process was continued until... After neutralization, carbonization is carried out at a second temperature, which is higher than the first temperature.

2. The method for preparing the hard carbon anode material according to claim 1, characterized in that, Includes at least one of the following features (1) to (24): (1) The sugarcane bagasse is crushed to 0.5~2.0mm before mixing; (2) The carbon content of the propylene oxide waste residue is ≥65wt.%; (3) The propylene oxide waste residue is dried at 100~120℃ for 8~12h before mixing; (4) The mass ratio of the sugarcane bagasse to the propylene oxide waste residue is 2~4:1; (5) The solid content of the precursor slurry is 15-25%; (6) The specific culture conditions are: temperature 30~35℃, pH 6.0~7.0, shaking culture time 24~48h, and shaking culture speed 200~250rpm; (7) The inoculation amount of the brewing yeast is 5-10 wt.% of the precursor slurry; (8) The ammonium dihydrogen phosphate accounts for 5-8 wt.% of the precursor slurry; (9) The soluble calcium salt is at least one of calcium chloride and calcium sulfate; (10) The soluble calcium salt accounts for 5-8 wt.% of the precursor slurry; (11) The urea accounts for 3-5 wt.% of the precursor slurry; (12) The trisodium citrate accounts for 0.1~0.3 wt.% of the precursor slurry; (13) The particle size of the biomineralization template is 20~50nm; (14) The concentration of the hydrogen peroxide solution is 20~45 wt.%; (15) The hydrogen peroxide solution accounts for 8-12 wt.% of the precursor slurry; (16) The oxidation reaction takes 1 to 2 hours and the temperature is 40 to 50°C; (17) The freeze-drying temperature is -40~-30℃, the vacuum degree is ≤10Pa, and the time is 12~24h; (18) The first temperature is 450~650℃, and the second temperature is 1100~1500℃; (19) The pulverization is carried out by air jet pulverization to a particle size Dv50 of 4~6μm; (20) The concentration of the dilute hydrochloric acid is 0.5~1.0 mol / L; (21) The soaking temperature is 50~60℃ and the soaking time is 4~6h; (22) The liquid-to-solid ratio of the dilute hydrochloric acid and the pre-carbonized product is 10-15:1; (23) The removal rate of the biomineralization template is ≥98%; (24) The pre-carbonized product is soaked in dilute hydrochloric acid, washed, and filtered until neutral.

3. The method for preparing the hard carbon anode material according to claim 1, characterized in that, The pre-carbonization is carried out under an inert atmosphere for a time of 0.5 to 3.0 hours.

4. The method for preparing the hard carbon anode material according to claim 3, characterized in that, The inert atmosphere is selected from at least one of nitrogen, argon, helium and neon, and the flow rate is 200~450 mL / min.

5. The method for preparing the hard carbon anode material according to claim 3, characterized in that, The heating rate for pre-carbonization is 2~10℃ / min.

6. The method for preparing the hard carbon anode material according to claim 1, characterized in that, The carbonization is carried out under an inert atmosphere for 2 to 10 hours.

7. The method for preparing the hard carbon anode material according to claim 6, characterized in that, The inert atmosphere is selected from at least one of nitrogen, argon, helium and neon, and the flow rate is 200~450 mL / min.

8. The method for preparing the hard carbon anode material according to claim 6, characterized in that, The carbonization heating rate is 2~4℃ / min.

9. The hard carbon anode material prepared by the method for preparing hard carbon anode material according to any one of claims 1 to 8, characterized in that, Includes at least one of the following features (1) to (7): (1) Particle size is 4~6μm; (2) Specific surface area is 3~7m² 2 / g; (3) The phosphorus doping content is 1.2~2.0 wt.%; (4) Nitrogen doping concentration is 0.8~1.5 wt.%; (5) Interlayer spacing d 002 The wavelength is 0.37~0.40 nm. (6) The average pore size is 5.0~20.0 nm; (7) The pore volume is 0.005~0.014cm. 3 / g.

10. The application of the hard carbon material according to claim 9 as a negative electrode material in a sodium-ion battery, characterized in that, Includes at least one of the following features (1) to (4): (1) The first reversible capacity at 0.2C is 350~380mAh / g; (2) The initial coulomb efficiency is 85-88%; (3) Capacity retention rate at 3C / 0.2C ≥72%; (4) Capacity decay rate ≤ 7% after 1000 cycles at 0.2C.

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