Preparation method of biomass hard carbon sodium-ion battery negative electrode material with good consistency

Abstract

The application discloses a biomass hard carbon sodium ion battery negative electrode material preparation method, which comprises the following steps: S1, raw material pre-breaking treatment: crushing and sieving the raw material to obtain biomass raw material of a first fineness; S2, raw material homogenization modification: mixing the biomass raw material obtained in the step S1 with acid liquor, a crosslinking agent and an organic pore-forming agent in a wet manner, centrifuging, washing and drying after temperature control reaction to obtain modified raw material uniformly distributed and rich in the organic pore-forming agent; S3, pre-carbonization treatment: pre-carbonizing the modified raw material obtained in the step S2 in a protective atmosphere to obtain pre-carbonized material; S4, crushing and refining: crushing and refining the pre-carbonized material obtained in the step S3 to obtain pre-carbonized material of a second fineness; and S5, high-temperature carbonization: high-temperature carbonizing the pre-carbonized material obtained in the step S4 in a protective atmosphere to obtain final hard carbon sodium ion battery negative electrode material. The application has the characteristics of good consistency, high first-week efficiency and effective improvement of sodium storage capacity.

Description

TECHNICAL FIELD

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

[0002] Compared with mainstream lithium ion batteries on the market, sodium ion batteries have the advantages of low production cost, good rate performance, good low-temperature performance, high safety performance and the like, and have good development prospects in the fields of energy storage, start-stop power supply, two-wheeled electric vehicles and the like. However, the energy density of the sodium ion battery is low, which limits the further development thereof.

[0003] One of the reasons why the energy density of the sodium ion battery is low is that the specific capacity of the hard carbon negative electrode material is low. The raw materials of mainstream hard carbon materials include biomass, coal, pitch and organic polymer materials, and the like, wherein the biomass raw material has the advantages of wide source, low cost, simple processing process and sufficient supply, and is the mainstream choice of current hard carbon negative electrode production plants.

[0004] Constructing a micropore structure in the hard carbon material is an effective way to improve the sodium storage capacity thereof. At present, the industry mainly adds a pore former to the raw material or intermediate product, and then plays an activation role in the subsequent carbonization process, so that the carbon material generates rich pore structures.

[0005] In the prior art, inorganic salts such as NaOH, KOH and ZnCl2 are mainly used as pore formers. However, the microcrystal size of the pore former in the raw material is large and unevenly distributed, so that the number of micropores generated is small, the consistency is poor, and mesopores and macropores are inevitably introduced, the specific surface area of the pore is too large, and the capacity improvement is extremely limited. SUMMARY

[0006] The purpose of the present application is to provide a biomass hard carbon sodium ion battery negative electrode material preparation method with good consistency, which has the characteristics of good consistency, high first-week efficiency and effective improvement of sodium storage capacity.

[0007] The present application can be realized by the following technical solutions:

[0008] The present application discloses a biomass hard carbon sodium ion battery negative electrode material preparation method with good consistency, comprising the following steps:

[0009] S1, raw material pre-breaking treatment: crushing and sieving the raw material to obtain biomass raw material with a first fineness;

[0010] S2, raw material homogenization modification: wet-mixing the biomass raw material obtained in step S1 with an acid solution, a crosslinking agent and an organic pore former, centrifuging, washing and drying after temperature control reaction to obtain modified raw material rich in uniformly distributed organic pore former;

[0011] S3, pre-carbonization treatment: the modified raw material obtained in step S2 is pre-carbonized under a protective atmosphere to obtain a pre-carbonized material;

[0012] S4, pulverization and refinement: the pre-carbonized material obtained in step S3 is pulverized and refined to obtain a pre-carbonized material with a second fineness;

[0013] S5, high-temperature carbonization: the pre-carbonized material obtained in step S4 is high-temperature carbonized under a protective atmosphere to obtain a final hard carbon sodium-ion battery negative electrode material.

[0014] In step S2 of the present application, the highly ordered and dense structure inside the biomass is opened at the beginning of the reaction. Specifically, the biomass is mainly composed of cellulose, hemicellulose and lignin, among which cellulose accounts for the highest proportion, about 40% to 50%. The chain structure regularity of cellulose and the hydroxyl groups on the molecular chain form a strong hydrogen bond network between different celluloses, resulting in a tight molecular arrangement between cellulose fibers, making it difficult for pore-forming agents to penetrate into the interior of the biomass material. Under the action of acid, the charge state of the -OH group inside the cellulose is changed, thereby breaking the hydrogen bond and weakening the binding force between cellulose molecules, and the structure is opened. The crosslinking agent undergoes crosslinking reaction between molecules under the catalysis of acid, and is converted from small molecular organic matter to polymer with larger molecular weight; at the same time, the crosslinking agent reacts with the -OH group of cellulose at the molecular level, achieving the purpose of uniform dispersion in the biomass raw material; in addition, the organic pore-forming agent has good affinity with the crosslinking agent, so that the organic pore-forming agent is also uniformly distributed in the biomass raw material.

[0015] Further, in step S2, the reaction temperature is 60-200℃, and the reaction time is 3-10h.

[0016] Further, in step S2, the acid is one or two or more of hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, formic acid, acetic acid, citric acid, oxalic acid and benzoic acid; the amount of acid used is 0.5-10 wt.% of the added amount of biomass raw material. In the present application, the amount of acid added affects the effect of the present application: specifically, if the amount of acid added is too low, the dense structure of the biomass raw material cannot be fully opened, and the purpose of the present application cannot be achieved; if the amount of acid added is too high, the cellulose will be dissolved in the acid, resulting in a decrease in product yield, which is not conducive to actual production.

[0017] Further, in step S2, the cross-linking agent is one or more of polyethylene glycol, phthalic acid glycoside, malonic acid, formaldehyde, benzaldehyde, propylene diamine, glyoxal, p-phenylenediamine, urea formaldehyde, furfural, diamino diphenyl methane, m-xylene amine, and biphenyl diammonium; the addition amount of the cross-linking agent is 1-5 wt.% of the addition amount of the biomass raw material. Specifically, in the present application, the cross-linking agent is an organic reagent containing hydroxyl, acid anhydride, aldehyde group, carboxyl, amino functional group and easily soluble in water, and the addition amount of the cross-linking agent affects the final technical effect. If the addition amount of the cross-linking agent is too low, the cross-linking functional group is insufficient, and the purpose of uniformly dispersing the pore-forming agent in the biomass raw material cannot be achieved. If the addition amount of the cross-linking agent is too high, the production cost of the material is increased, which is not conducive to actual production.

[0018] Further, in step S2, the organic pore-forming agent is one or more of sodium gluconate, potassium gluconate, magnesium gluconate, zinc gluconate, sodium acetate, potassium acetate, zinc acetate, magnesium acetate, sodium citrate, potassium citrate, zinc citrate, magnesium citrate, sodium oxalate, potassium oxalate, zinc oxalate, magnesium oxalate, sodium formate, potassium formate, zinc formate, magnesium formate, sodium benzoate, potassium benzoate, zinc benzoate, and magnesium benzoate; the addition amount of the organic pore-forming agent is 5-50 wt.% of the addition amount of the biomass raw material. If the addition amount of the organic pore-forming agent is too low, it is difficult to form a rich microporous structure inside the hard carbon material, and the capacity improvement is limited. If the addition amount of the organic pore-forming agent is too high, mesopores and macropores are easily formed in the hard carbon material, which adversely affects the electrochemical performance.

[0019] Further, in step S3, the protective atmosphere is nitrogen and / or argon, the carbonization temperature is 500-1000°C, and the carbonization time is 2-6 h. In the carbonization process, the organic pore-forming agent is pyrolyzed to form metal oxides, and then the metal oxides act as activators to activate the carbon layer to form a porous structure. In the present application, the carbonization temperature and the carbonization time affect the effect of the present application. If the carbonization temperature is too low or the time is insufficient, the activation effect is not obvious, and it is difficult to form a rich microporous structure inside the carbon material. On the contrary, the activation effect is too strong, and after the carbon material is activated to form micropores, it continues to be activated, eventually forming mesopores or macropores, resulting in insufficient micropore content and excessive specific surface area of the hard carbon material.

[0020] Further, in step S4, the protective atmosphere is nitrogen and / or argon, the carbonization temperature is 1200-1500 DEG C, the carbonization time is 2-8h, and the heating rate is 1-15 DEG C / min. Higher carbonization temperature, longer carbonization time, and slower heating rate are conducive to graphitization of the carbon material, promote the collapse of the open micropore walls to form closed internal pores, and reduce the specific surface area of the material. However, too high a carbonization temperature will cause the material to be too graphitized, the interlayer spacing will be narrowed, and the sodium ions will be difficult to deintercalate between the carbon layers, affecting the rate performance of the carbon material; too long a carbonization time and too slow a heating rate will increase the production cycle of the product and increase the production cost, which is not conducive to actual production.

[0021] Further, in step S1, the mesh size of the screen is greater than or equal to 15 mesh; if the mesh size of the screen is too small, the particle size of the obtained biomass material will be too large, which is not conducive to the occurrence of the modification reaction.

[0022] Further, in step S4, the crushing method is one or more of a pair of rollers, a mechanical mill, a Raymond mill, an E crusher, an air flow powder, a ball mill, a sand mill, and a stirring mill; the D50 of the crushed and carbonized material is 3-15um.

[0023] Further, in step S1, the raw material is one or more of coconut shell, walnut shell, nut shell, apricot shell, coffee shell, corn cob, straw, reed, bamboo, rice husk, poplar, eucalyptus, pine, sugarcane residue, starch, cassava powder, fruit wood, miscellaneous wood, Chinese fir, oak.

[0024] The biomass hard carbon sodium ion battery negative material preparation method has the following advantages:

[0025] First, the consistency is good, the crosslinking agent is uniformly distributed in the organic pore-forming agent raw material, so the product shows good consistency;

[0026] Second, the initial efficiency is high, the synergistic effect of the acid, the crosslinking agent and the organic pore-forming agent forms a rich microporous structure inside the hard carbon material, almost no mesoporous and macroporous is generated, and the microporous is closed during the subsequent high-temperature sintering process, so that the material has a low specific surface area and shows a low initial efficiency.

[0027] Third, the sodium storage capacity is effectively improved, the acid catalysis opens the dense structure of the biomass, so that the activator can fully penetrate into the inside of the biomass raw material; the organic crosslinking agent makes the pore-forming agent uniformly distributed in the inside of the biomass raw material. The synergistic effect of the acid, the crosslinking agent and the organic pore-forming agent forms a rich microporous structure inside the hard carbon material, and the microporous structure as a sodium storage active site increases the sodium storage capacity of the hard carbon material. DETAILED DESCRIPTION

[0028] In order to make the person in this field better understand the technical scheme of the present application, the product of the present application is further described in detail below in combination with embodiments.

[0029] The application discloses a preparation method of a biomass hard carbon sodium ion battery negative electrode material with good consistency.

[0030] S1, raw material pre-breaking treatment: crushing and sieving the raw material to obtain biomass raw material of a first fineness;

[0031] S2, raw material homogenization modification: mixing the biomass raw material obtained in step S1 with acid liquor, cross-linking agent and organic pore-forming agent in a wet manner, centrifuging, washing and drying after temperature control reaction to obtain modified raw material uniformly distributed and rich in organic pore-forming agent;

[0032] S3, pre-carbonization treatment: pre-carbonizing the modified raw material obtained in step S2 in a protective atmosphere to obtain pre-carbonized material;

[0033] S4, crushing and refining: crushing and refining the pre-carbonized material obtained in step S3 to obtain pre-carbonized material of a second fineness;

[0034] S5, high-temperature carbonization: high-temperature carbonizing the pre-carbonized material obtained in step S4 in a protective atmosphere to obtain the final hard carbon sodium ion battery negative electrode material.

[0035] Further, in step S2, the reaction temperature is 60-200 DEG C, and the reaction time is 3-10 h.

[0036] Further, in step S2, the acid liquor is one or two or more of hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, formic acid, acetic acid, citric acid, oxalic acid and benzoic acid; and the amount of the acid liquor added to the biomass raw material is 0.5-10 wt.%.

[0037] Further, in step S2, the cross-linking agent is one or two or more of polyethylene glycol, phthalic acid glycoside, malonic acid, formaldehyde, benzaldehyde, propylene diamine, glyoxal, p-phenylenedimethylene, urea-formaldehyde, furfural, diamino diphenyl methane, m-xylene amine and diphenyl diammonium; and the amount of the cross-linking agent added to the biomass raw material is 1-5 wt.%.

[0038] Further, in step S2, the organic pore-forming agent is one or two or more of sodium gluconate, potassium gluconate, magnesium gluconate, zinc gluconate, sodium acetate, potassium acetate, zinc acetate, magnesium acetate, sodium citrate, potassium citrate, zinc citrate, magnesium citrate, sodium oxalate, potassium oxalate, zinc oxalate, magnesium oxalate, sodium formate, potassium formate, zinc formate, magnesium formate, sodium benzoate, potassium benzoate, zinc benzoate and magnesium benzoate; and the amount of the organic pore-forming agent added to the biomass raw material is 5-50 wt.%.

[0039] Further, in step S3, the protective atmosphere is nitrogen and / or argon, the carbonization temperature is 500-1000℃, and the carbonization time is 2-6h.

[0040] Further, in step S4, the protective atmosphere is nitrogen and / or argon, the carbonization temperature is 1200-1500℃, the carbonization time is 2-8h, and the heating rate is 1-15℃ / min.

[0041] Further, in step S1, the mesh size of the screen is ≥15 mesh.

[0042] Further, in step S4, the crushing method is one or more of a pair of rollers, a mechanical mill, a Raymond mill, an E-break, an air flow powder, a ball mill, a sand mill, and a stirring mill; and the D50 of the crushed carbonization material is 3-15μm.

[0043] Further, in step S1, the raw material is one or more of coconut shell, walnut shell, nut shell, apricot shell, coffee shell, corn cob, straw, reed, bamboo, rice husk, poplar, eucalyptus, pine, sugarcane residue, starch, cassava powder, fruit wood, miscellaneous wood, Chinese fir, oak. Embodiment

[0044] The present embodiment relates to a method for preparing a biomass hard carbon sodium-ion battery negative electrode material with good consistency, comprising the following steps:

[0045] S1, raw material pre-breaking treatment: crushing and sieving the raw material to obtain a biomass raw material with a first fineness. Specifically, the mesh size of the screen is ≥15 mesh, and the raw material is coconut shell, walnut shell, nut shell.

[0046] S2, raw material homogenization modification: wet mixing the biomass raw material obtained in step S1 with acid, crosslinking agent, and organic pore-forming agent, centrifuging, washing, and drying after temperature control reaction to obtain a modified raw material with uniform distribution and rich organic pore-forming agent. Specifically, the reaction temperature is 200℃, the reaction time is 6h; the acid is hydrochloric acid, and the amount of acid added is 0.5wt.% of the biomass raw material; the crosslinking agent is polyethylene glycol and o-phthalic acid glycoside, and the amount of crosslinking agent added is 5wt.% of the biomass raw material; and the organic pore-forming agent is sodium gluconate, potassium gluconate, magnesium gluconate, and zinc gluconate, and the amount of organic pore-forming agent added is 25wt.% of the biomass raw material.

[0047] S3, pre-carbonization treatment: pre-carbonizing the modified raw material obtained in step S2 under a protective atmosphere to obtain a pre-carbonization material. Specifically, the protective atmosphere is nitrogen and argon, the carbonization temperature is 1000℃, and the carbonization time is 4h.

[0048] S4, crushing and refining: the pre-carbonized material obtained in step S3 is crushed and refined to obtain a second fineness of pre-carbonized material. Specifically, the protective atmosphere is nitrogen, the carbonization temperature is 1500℃, the carbonization time is 5h, and the heating rate is 1℃ / min; the crushing method is roller, mechanical grinding, Raymond grinding, and the D50 of the crushed carbonized material is 3-15pm.

[0049] S5, high-temperature carbonization: the pre-carbonized material obtained in step S4 is subjected to high-temperature carbonization under a protective atmosphere to obtain the final hard carbon sodium ion battery negative electrode material. Embodiment

[0050] The present embodiment relates to a biomass hard carbon sodium ion battery negative electrode material preparation method with good consistency, comprising the following steps:

[0051] S1, raw material pre-breaking treatment: crushing and sieving the raw material to obtain a first fineness of biomass raw material. Specifically, the mesh size of the sieve is ≥15 mesh, and the raw material is sugarcane residue, starch, cassava powder, fruit wood, miscellaneous wood, cedar, oak.

[0052] S2, raw material homogenization modification: wet mixing the biomass raw material obtained in step S1 with acid, crosslinking agent and organic pore-forming agent, centrifuging, washing and drying after temperature control reaction to obtain a modified raw material with uniform distribution and rich organic pore-forming agent. Specifically, the reaction temperature is 120℃, and the reaction time is 3h; the acid is acetic acid, citric acid, oxalic acid and benzoic acid, and the amount of acid added is 10 wt.% of the biomass raw material; the crosslinking agent is m-xylene amine and diphenyl diamine, and the amount of crosslinking agent added is 3 wt.% of the biomass raw material; the organic pore-forming agent is zinc formate, magnesium formate, sodium benzoate, potassium benzoate, zinc benzoate and magnesium benzoate, and the amount of organic pore-forming agent added is 5 wt.% of the biomass raw material.

[0053] S3, pre-carbonization treatment: the modified raw material obtained in step S2 is subjected to pre-carbonization under a protective atmosphere to obtain a pre-carbonized material. Specifically, the protective atmosphere is nitrogen, the carbonization temperature is 800℃, and the carbonization time is 2h.

[0054] S4, crushing and refining: the pre-carbonized material obtained in step S3 is crushed and refined to obtain a second fineness of pre-carbonized material. Specifically, the protective atmosphere is argon, the carbonization temperature is 1400℃, the carbonization time is 2h, and the heating rate is 15℃ / min; the crushing method is ball milling and sand milling, and the D50 of the crushed carbonized material is 3-15pm.

[0055] S5, high-temperature carbonization: the pre-carbonized material obtained in step S4 is subjected to high-temperature carbonization under a protective atmosphere to obtain the final hard carbon sodium ion battery negative electrode material. Embodiment

[0056] The embodiment relates to a biomass hard carbon sodium ion battery negative electrode material preparation method with good consistency, and comprises the following steps:

[0057] S1, raw material pre-breaking treatment: the raw material is crushed and sieved to obtain biomass raw material of a first fineness. Specifically, the mesh number of the sieve is greater than or equal to 15 meshes, and the raw material is coconut shell, walnut shell, starch, cassava powder, fruit wood, miscellaneous wood, Chinese fir, oak.

[0058] S2, raw material homogenization modification: the biomass raw material obtained in step S1 is mixed with acid liquor, crosslinking agent and organic pore-forming agent in a wet manner, and after temperature control reaction, centrifugation, washing and drying, modified raw material rich in organic pore-forming agent and uniformly distributed is obtained. Specifically, the reaction temperature is 60 DEG C, and the reaction time is 10 hours; the acid liquor is hydrochloric acid, nitric acid, oxalic acid and benzoic acid, and the amount of the acid liquor is 5 wt.% of the biomass raw material; the crosslinking agent is polyethylene glycol, o-phthalic acid glycoside, malonic acid and diphenyl diammonium, and the amount of the crosslinking agent is 3 wt.% of the biomass raw material; the organic pore-forming agent is sodium gluconate, potassium gluconate, magnesium gluconate, magnesium oxalate, sodium formate, potassium formate, zinc formate, magnesium formate, sodium benzoate, potassium benzoate, zinc benzoate and magnesium benzoate, and the amount of the organic pore-forming agent is 5 wt.% of the biomass raw material.

[0059] S3, pre-carbonization treatment: the modified raw material obtained in step S2 is pre-carbonized in a protective atmosphere to obtain pre-carbonized material. Specifically, the protective atmosphere is argon, the carbonization temperature is 500 DEG C, and the carbonization time is 6 hours.

[0060] S4, crushing and refining: the pre-carbonized material obtained in step S3 is crushed and refined to obtain pre-carbonized material of a second fineness. Specifically, the protective atmosphere is nitrogen and argon, the carbonization temperature is 1200 DEG C, the carbonization time is 8 hours, and the heating rate is 6 DEG C / min; the crushing mode is airflow powder, and the pre-carbonized material is crushed to D50 of 3-15 microns.

[0061] S5, high-temperature carbonization: the pre-carbonized material obtained in step S4 is high-temperature carbonized in a protective atmosphere to obtain the final hard carbon sodium ion battery negative electrode material. Embodiment

[0062] The embodiment relates to a biomass hard carbon sodium ion battery negative electrode material preparation method with good consistency, and comprises the following steps:

[0063] S1, raw material pre-breaking treatment: the raw material is crushed and sieved to obtain biomass raw material of a first fineness. Specifically, the mesh number of the sieve is greater than or equal to 15 meshes, and the raw material is coconut shell, walnut shell, starch, cassava powder, fruit wood, miscellaneous wood, Chinese fir, oak.

[0064] S2, raw material homogenization modification: the biomass raw material obtained in step S1 is mixed with acid, crosslinking agent and organic pore forming agent, and after temperature control reaction, centrifugation, washing and drying, a modified raw material with uniform distribution of organic pore forming agent is obtained. Specifically, the reaction temperature is 100°C, the reaction time is 5h; the acid is hydrochloric acid, nitric acid, phosphoric acid and sulfuric acid, and the amount of acid added is 3wt.% of the biomass raw material; the crosslinking agent is polyethylene glycol, phthalyl glycol, malonic acid and formaldehyde, and the amount of crosslinking agent added is 2wt.% of the biomass raw material; the organic pore forming agent is sodium gluconate, potassium gluconate and magnesium gluconate, and the amount of organic pore forming agent added is 10wt.% of the biomass raw material.

[0065] S3, pre-carbonization treatment: the modified raw material obtained in step S2 is pre-carbonized in a protective atmosphere to obtain a pre-carbonized material. Specifically, the protective atmosphere is nitrogen and argon, the carbonization temperature is 600°C, and the carbonization time is 5h.

[0066] S4, crushing and refining: the pre-carbonized material obtained in step S3 is crushed and refined to obtain a second fineness of pre-carbonized material. Specifically, the protective atmosphere is nitrogen and argon, the carbonization temperature is 1400°C, the carbonization time is 3h, and the heating rate is 1-15°C / min; the crushing method is roller crushing, and the D50 of the carbonized material is 3-15μm.

[0067] S5, high-temperature carbonization: the pre-carbonized material obtained in step S4 is high-temperature carbonized in a protective atmosphere to obtain the final hard carbon sodium ion battery negative electrode material. Embodiment

[0068] The present embodiment relates to a method for preparing a biomass hard carbon sodium ion battery negative electrode material with good consistency, comprising the following steps:

[0069] S1, raw material pre-breaking treatment: the raw material is crushed and sieved to obtain a first fineness of biomass raw material. Specifically, the mesh size of the sieve is ≥15 mesh, and the raw material is poplar, eucalyptus, pine, sugarcane residue, starch, cassava powder, fruit wood, miscellaneous wood, fir wood and oak wood.

[0070] S2, raw material homogenization modification: the biomass raw material obtained in step S1 is mixed with acid, crosslinking agent and organic pore forming agent, and after temperature control reaction, centrifugation, washing and drying, a modified raw material rich in organic pore forming agent and uniformly distributed is obtained. Specifically, the reaction temperature is 160℃, the reaction time is 7h; the acid is hydrochloric acid, oxalic acid and benzoic acid, and the amount of acid added is 3 wt.% of the biomass raw material; the crosslinking agent is polyethylene glycol, phthalic acid glycoside and malonic acid, and the amount of crosslinking agent added is 2 wt.% of the biomass raw material; the organic pore forming agent is sodium gluconate, potassium gluconate, magnesium gluconate, potassium benzoate, zinc benzoate and magnesium benzoate, and the amount of organic pore forming agent added is 12 wt.% of the biomass raw material.

[0071] S3, pre-carbonization treatment: the modified raw material obtained in step S2 is pre-carbonized under a protective atmosphere to obtain a pre-carbonized material. Specifically, the protective atmosphere is nitrogen and argon, the carbonization temperature is 900℃, and the carbonization time is 5h.

[0072] S4, crushing and refining: the pre-carbonized material obtained in step S3 is crushed and refined to obtain a pre-carbonized material with a second fineness. Specifically, the protective atmosphere is nitrogen and argon, the carbonization temperature is 1300℃, the carbonization time is 7h, and the heating rate is 5℃ / min; the crushing method is crushing, air flow powder and ball milling, and the D50 of the carbonized material is 3-15μm.

[0073] S5, high-temperature carbonization: the pre-carbonized material obtained in step S4 is high-temperature carbonized under a protective atmosphere to obtain a final hard carbon sodium ion battery negative electrode material.

[0074] The present embodiment relates to a method for preparing a biomass hard carbon sodium ion battery negative electrode material with good consistency, comprising the following steps:

[0075] S1, raw material pre-breaking treatment: walnut shell raw material is crushed and passed through a 20 mesh screen to obtain walnut shell raw material with a certain fineness.

[0076] S2, raw material homogenization modification: the walnut shell raw material with a certain fineness obtained in step S1 is mixed with hydrochloric acid, polyethylene glycol crosslinking agent, sodium acetate and deionized water, then reacted in a high-pressure reaction kettle at 100℃ for 5h, and then centrifuged, washed and dried to obtain a modified raw material rich in organic pore forming agent and uniformly distributed. Among them, the addition amounts of hydrochloric acid, polyethylene glycol crosslinking agent and sodium acetate are 2.5wt.%, 2.0wt.% and 20 wt.% of the walnut shell raw material, respectively.

[0077] S3, pre-carbonization treatment: the modified raw material obtained in step S2 is pre-carbonized under a nitrogen protective atmosphere, the carbonization temperature is 800℃, and the carbonization time is 3h, to obtain a pre-carbonized material.

[0078] S4, pre-carbonization treatment: crushing and refining: the pre-carbonized material obtained in step S3 is crushed and refined using an air flow crusher to obtain a pre-carbonized material with a D50 of 7 pm.

[0079] S5, high-temperature carbonization: the pre-carbonized material obtained in step S4 is subjected to high-temperature carbonization under a nitrogen gas atmosphere, the carbonization temperature is 1300°C, the carbonization time is 3 h, and the heating rate is 5°C / min, to obtain the high-capacity hard carbon negative electrode material of application example 1.

[0080] The obtained material is subjected to electrochemical performance testing according to the following method: hard carbon material, Super P, CMC, SBR are mixed into a homogenate in a mass ratio of 94:1.5:2:2.5, then the black slurry is coated on a copper foil using a 120 um four-side preparation device, and then the film is dried in a 100°C vacuum drying oven for 2 hours. The electrode film is punched into a circular sheet with a radius of 0.6 mm using a sheet punching machine, metal sodium is used as the counter electrode, 1 mol / L NaClO4 EC+DEC (1:1 vol%) is used as the electrolyte, and PP / PE / PP three-layer separators are used as the separators, and CR2016 type button cells are assembled in a glove box. The above button cells are subjected to constant current charge and discharge tests, the current density is 0.1C (1C=300 mAh / g), and the voltage range is 2-0.005 V.

[0081] This example relates to a method for preparing a biomass hard carbon sodium ion battery negative electrode material, which differs from application example 1 in that no acid solution is added for modification treatment, comprising the following steps:

[0082] S1, raw material pre-breaking treatment: the walnut shell raw material is crushed and passed through a 20 mesh screen to obtain a walnut shell raw material with a certain fineness.

[0083] S2, raw material modification: the walnut shell raw material with a certain fineness obtained in step S1 is mixed with a polyethylene glycol crosslinking agent, sodium acetate and deionized water, then reacted in a high-pressure reaction kettle at 100°C for 5h, then centrifuged, washed and dried to obtain a modified raw material rich in organic pore-forming agent and uniformly distributed. The addition amounts of the polyethylene glycol crosslinking agent and sodium acetate are 2.0 wt.% and 20 wt.% of the addition amount of the walnut shell raw material, respectively.

[0084] S3, pre-carbonization treatment: the modified raw material obtained in step S2 is subjected to pre-carbonization under a nitrogen protective atmosphere, the carbonization temperature is 800°C, and the carbonization time is 3h, to obtain a pre-carbonized material.

[0085] S4, pre-carbonization treatment: crushing and refining: the pre-carbonized material obtained in step S3 is crushed and refined using an air flow crusher to obtain a pre-carbonized material with a D50 of 7 pm.

[0086] S5, high-temperature carbonization: the pre-carbonization material obtained in step S4 is subjected to high-temperature carbonization under a nitrogen gas atmosphere, the carbonization temperature is 1300°C, the carbonization time is 3 h, and the heating rate is 5°C / min, to obtain the hard carbon negative electrode material of Comparative Example 1.

[0087] The obtained material is subjected to electrochemical performance testing according to the following method: the hard carbon material, Super P, CMC, and SBR are mixed into a homogenate at a mass ratio of 94:1.5:2:2.5, the black slurry is coated on a copper foil using a 120 um four-side coater, and then the film is dried in a 100°C vacuum drying oven for 2 hours. The electrode film is punched into a circular sheet with a radius of 0.6 mm using a sheet puncher, a metal sodium is used as the counter electrode, 1 mol / L NaClO4 EC+DEC (1:1 vol%) is used as the electrolyte, and a PP / PE / PP three-layer separator is used as the separator, to assemble a CR2016 type button cell in a glove box. The button cell is subjected to constant current charge and discharge testing, the current density is 0.1C (1C=300 mAh / g), and the voltage range is 2-0.005 V.

[0088] This embodiment relates to a preparation method of a biomass hard carbon sodium ion battery negative electrode material, which differs from Application Example 1 in that no crosslinking agent is added for modification treatment, and includes the following steps:

[0089] S1, raw material pre-breaking treatment: walnut shell raw materials are broken and passed through a 20-mesh screen to obtain walnut shell raw materials with a certain fineness.

[0090] S2, raw material modification: the walnut shell raw materials with a certain fineness obtained in step S1 are mixed with hydrochloric acid, sodium acetate, and deionized water, and then reacted in a high-pressure reaction kettle at 100°C for 5 h, followed by centrifugation, washing, and drying, to obtain modified raw materials rich in organic pore-forming agents and uniformly distributed. The addition amounts of hydrochloric acid and sodium acetate are 2.5 wt.% and 20 wt.% of the addition amount of the walnut shell raw materials, respectively.

[0091] S3, pre-carbonization treatment: the modified raw materials obtained in step S2 are subjected to pre-carbonization under a nitrogen protective atmosphere, the carbonization temperature is 800°C, and the carbonization time is 3 h, to obtain pre-carbonization materials.

[0092] S4, pre-carbonization treatment: the pre-carbonization materials obtained in step S3 are finely ground using an air jet mill to obtain pre-carbonization materials with a D50 of 7 μm.

[0093] S5, high-temperature carbonization: the pre-carbonization materials obtained in step S4 are subjected to high-temperature carbonization under a nitrogen gas atmosphere, the carbonization temperature is 1300°C, the carbonization time is 3 h, and the heating rate is 5°C / min, to obtain the hard carbon negative electrode material of Comparative Example 2.

[0094] The obtained material was subjected to electrochemical performance test according to the following method: the hard carbon material, Super P, CMC and SBR were mixed into a homogenate at a mass ratio of 94:1.5:2:2.5, then the black slurry was coated on a copper foil using a 120 um four-side preparation device, and then the film was dried in a 100°C vacuum drying oven for 2 hours. The electrode film was punched into a circular sheet with a radius of 0.6 mm using a sheet puncher, and a metal sodium was used as a counter electrode, 1 mol / L NaClO4 EC+DEC (1:1 vol%) was used as an electrolyte, and a PP / PE / PP three-layer separator was used as a separator to assemble a CR2016 type button cell in a glove box. The above button cell was subjected to constant current charge and discharge test, the current density was 0.1C (1C=300 mAh / g), and the voltage range was 2-0.005 V.

[0095] The nitrogen adsorption and desorption test results show that the specific surface areas of the hard carbon materials of application example 1, comparative example 1 and comparative example 2 are 4.8, 25.4 and 18.9 m2 / g respectively, and the synergistic effect of the acid solution, the crosslinking agent and the organic pore-forming agent makes the hard carbon material hardly generate mesopores and macropores, and the micropores are closed in the subsequent high-temperature sintering process, so that the material has a low specific surface area.

[0096] The He gas true density test results show that the true densities of the hard carbon materials of application example 1, comparative example 1 and comparative example 2 are 1.86, 1.93 and 1.97 g / cm3 respectively, indicating that the synergistic effect of the acid solution, the crosslinking agent and the organic pore-forming agent makes the hard carbon material form rich micropore structures inside, thereby reducing the true density of the hard carbon material.

[0097] The constant current charge and discharge test shows that the first cycle charge capacities of the hard carbon materials of application example 1, comparative example 1 and comparative example 2 are 342, 276 and 281 mAh / g respectively, and the first cycle coulombic efficiencies are 92.1%, 86.7% and 88.4% respectively, indicating that the formation of rich micropore structures inside the hard carbon material can effectively improve the sodium storage capacity of the hard carbon material, and the reduction of the specific surface area of the material can effectively improve the first cycle coulombic efficiency of the hard carbon material.

[0098] The above examples are only specific embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as limiting the scope of the patent of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, and these obvious alternative forms all belong to the protection scope of the present application.

Claims

1. A method for preparing a negative electrode material for a biomass hard carbon sodium-ion battery, characterized in that... Includes the following steps: S1. Raw material pre-crushing treatment: The raw material is crushed and sieved to obtain biomass raw material of the first fineness; S2. Raw Material Homogenization Modification: The biomass raw material obtained in step S1 is wet-mixed with acid, crosslinking agent, and organic pore-forming agent. After temperature-controlled reaction, it is centrifuged, washed, and dried to obtain a uniformly distributed modified raw material rich in organic pore-forming agent. The acid is one or more of hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, oxalic acid, and benzoic acid; the amount of acid is 0.5-10 wt.% of the biomass raw material; the crosslinking agent is one or more of polyethylene glycol, phthalic acid, malonic acid, formaldehyde, and biphenyl diamine; the amount of crosslinking agent is 1-5 wt.% of the biomass raw material; the amount of organic pore-forming agent is 5-50 wt.% of the biomass raw material. S3. Pre-carbonization treatment: The modified raw material obtained in step S2 is pre-carbonized under a protective atmosphere to obtain pre-carbonized material; S4. Crushing and refining: The pre-carbonized material obtained in step S3 is crushed and refined to obtain pre-carbonized material of the second fineness; S5. High-temperature carbonization: The pre-carbonized material obtained in step S4 is carbonized at high temperature under a protective atmosphere to obtain the final hard carbon sodium-ion battery anode material.

2. The method for preparing the anode material of a biomass hard carbon sodium-ion battery according to claim 1, characterized in that: In step S2, the reaction temperature is 60-200℃ and the reaction time is 3-10h.

3. The method for preparing the anode material of a biomass hard carbon sodium-ion battery according to claim 1, characterized in that: In step S2, the organic pore-forming agent is one or more of the following: sodium gluconate, potassium gluconate, magnesium gluconate, zinc gluconate, sodium acetate, potassium acetate, zinc acetate, magnesium acetate, sodium citrate, potassium citrate, zinc citrate, magnesium citrate, sodium oxalate, potassium oxalate, zinc oxalate, magnesium oxalate, sodium formate, potassium formate, zinc formate, magnesium formate, sodium benzoate, potassium benzoate, zinc benzoate, and magnesium benzoate.

4. The method for preparing the anode material of a biomass hard carbon sodium-ion battery according to claim 1, characterized in that: In step S3, the protective atmosphere is nitrogen and / or argon, the carbonization temperature is 500-1000℃, and the carbonization time is 2-6h.

5. The method for preparing the anode material of a biomass hard carbon sodium-ion battery according to claim 1, characterized in that: In step S5, the protective atmosphere is nitrogen and / or argon, the carbonization temperature is 1200-1500℃, the carbonization time is 2-8h, and the heating rate is 1-15℃ / min.

6. The method for preparing the anode material of a biomass hard carbon sodium-ion battery according to claim 1, characterized in that: In step S1, the mesh size of the sieve is ≥15 mesh.

7. The method for preparing the anode material of a biomass hard carbon sodium-ion battery according to claim 1, characterized in that: In step S4, the crushing method is one or more of the following: roller mill, Raymond mill, jaw crusher, air jet mill, ball mill, sand mill, and stirred mill.

8. The method for preparing the anode material of a biomass hard carbon sodium-ion battery according to claim 1, characterized in that: In step S1, the raw materials are one or more of the following: coconut shell, walnut shell, nut shell, apricot shell, coffee shell, corn cob, straw, reed, bamboo, rice husk, poplar, eucalyptus, pine, bagasse, starch, cassava flour, fruit wood, fir, and oak.