Biomass hard carbon negative electrode material, preparation method thereof and battery

Abstract

The invention belongs to the technical field of battery manufacturing, and relates to a biomass hard carbon negative electrode material, a preparation method thereof and a battery, and the preparation method comprises the following steps: sequentially carrying out sterilization treatment, silicate bacteria biological impurity removal, washing and carbonization on a biomass raw material; wherein the silicate bacterium biological impurity removal comprises the following steps: immersing a biomass raw material into a silicate bacterium stock solution for constant-temperature culture. According to the method, specific biological impurity removal is performed on the hard carbon biomass precursor by adopting silicate bacteria, so that the common problems of material structure damage, incomplete impurity removal, environmental pollution, complex process and the like existing in the existing hard carbon impurity removal process are effectively solved, and the sodium storage performance and the stability of the sodium-ion battery negative electrode material are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery manufacturing, and relates to a hard carbon negative electrode material, in particular to a biomass hard carbon negative electrode material and a preparation method thereof and a battery. BACKGROUND

[0002] Hard carbon material has important application value in the field of lithium / sodium ion battery negative electrode due to its unique disordered layered structure and excellent electrochemical performance. However, during the preparation of hard carbon, impurities such as ash (inorganic metal salt, oxide) and residual organic volatile matter are easily introduced due to the difference in the source of the precursor (such as biomass, polymer, pitch, etc.) and the pyrolysis process. These impurities can significantly reduce the conductivity, the first cycle coulombic efficiency and the cycle stability of the hard carbon, so the efficient impurity removal process has become one of the key links in the industrialization of the hard carbon material.

[0003] At present, the mainstream hard carbon impurity removal method in the industry includes acid washing and alkali washing processes, but both of these two processes have obvious defects. The acid washing method usually uses strong corrosive acid solutions such as hydrochloric acid, sulfuric acid, nitric acid or hydrofluoric acid to remove impurities by dissolving metal oxides or salts in hard carbon, but it faces three problems: first, strong acid can easily corrode equipment, increasing production cost and safety risk; second, part of the acid ions are easily adsorbed on the carbon surface, introducing new impurities; third, excessive acid washing can destroy part of the sp 2 carbon structure, reducing the conductivity of the material.

[0004] The alkali washing method (such as NaOH or KOH solution) is mainly used to remove acidic groups or silicate impurities in hard carbon, although the reaction conditions are relatively mild, but the removal capacity of most metal impurities is limited, and alkali washing can easily cause oxidation on the surface of hard carbon, forming oxygen-containing functional groups such as carboxyl and phenolic hydroxyl groups, thereby increasing the irreversible capacity of the material. More importantly, if the residual alkali is not completely removed by water washing after alkali washing, the structure of the material will collapse during subsequent high-temperature treatment.

[0005] In recent years, researchers have tried to optimize the traditional acid-alkali washing process, such as using step-by-step acid-alkali combined cleaning or introducing complexing agents (such as EDTA) to enhance the chelation capacity of metal impurities, but these optimization schemes still have not broken through the core bottleneck: high process complexity, high wastewater treatment cost, or the risk of secondary pollution. At the same time, the pore structure of hard carbon is easily changed uncontrollably during the acid-alkali cleaning process, which directly affects its lithium / sodium storage performance.

[0006] In summary, the existing hard carbon impurity removal process generally has problems such as material structure damage, incomplete impurity removal, environmental pollution and process complexity, which cannot meet the needs of hard carbon material industrialization for efficient, low-damage and environmentally friendly impurity removal technology. Therefore, how to develop such impurity removal technology has become a difficult point that needs to be broken through in the current industry. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application aims to provide a biomass hard carbon negative electrode material, a preparation method thereof and a battery, effectively solving the problems of material structure damage, incomplete impurity removal, environmental pollution and complex process commonly existing in the existing hard carbon impurity removal process, and fully meeting the needs of hard carbon material industrialization for efficient, low-damage and environmentally friendly impurity removal technology.

[0008] To achieve the object of the present application, the following technical solutions are adopted:

[0009] In a first aspect, the present application provides a preparation method of a biomass hard carbon negative electrode material, comprising sterilization treatment, silicate bacterial biological impurity removal, washing and carbonization of the biomass raw material in sequence.

[0010] The silicate bacterial biological impurity removal comprises immersing the biomass raw material in a silicate bacterial stock solution for constant temperature culture.

[0011] The preparation method provided by the present application completes the impurity removal step before carbonization, effectively avoiding the damage to the material micropore structure caused by acid washing or alkali washing after carbonization in the traditional process, retaining the porous and loose characteristics of the biomass hard carbon, and making the biomass hard carbon material exhibit excellent sodium storage capacity.

[0012] In addition, the silicate bacteria can specifically decompose insoluble impurities such as silicon and aluminum in the hard carbon without damaging the carbon skeleton structure. Compared with the traditional acid and alkali method, the mixed organic acids produced by microbial metabolism can gently dissolve metal oxides, greatly reducing the damage to the material structure, and the low-carbon organic matter produced by metabolism can convert open pores in the hard carbon into closed pore structures after melting, building a rich micropore structure inside the hard carbon material, and further improving the sodium storage active sites.

[0013] Further, the present application does not need to use strong corrosive acid and alkali in the impurity removal process, reducing the pollution to the environment. At the same time, the preparation process of the impurity removal biomass raw material is simple and economical, which can improve the economic benefit of the whole hard carbon material production chain. This green and environmentally friendly preparation process significantly reduces the production cost, fully meets the needs of hard carbon material industrialization for efficient, low-damage and environmentally friendly impurity removal technology.

[0014] Preferably, the biomass raw material comprises any one or a combination of two or more of coconut shell, bamboo, straw, wood, nut shell, starch, bagasse, corn cob, rice husk, peanut shell, starch or lignin. Typical but non-limiting combinations include combinations of coconut shell and bamboo, combinations of bamboo and straw, combinations of straw and wood, combinations of wood and nut shell, combinations of nut shell and starch, combinations of starch and bagasse, combinations of bagasse and corn cob, combinations of corn cob and rice husk, combinations of rice husk and peanut shell, combinations of peanut shell and starch, or combinations of starch and lignin.

[0015] The preparation method provided by the present application is suitable for different kinds of biomass raw materials, is not excessively limited by the kind of raw material, provides the possibility for diversified selection of biomass hard carbon raw materials, and further expands the application range of the technology.

[0016] Preferably, the sterilization treatment mode comprises high-temperature boiling, specifically comprising: after crushing the biomass raw material, distilling and / or boiling the crushed biomass raw material with deionized water, and then drying after cooling.

[0017] In the present application, the high-temperature boiling is used to sterilize the biomass raw material, and completely kill the miscellaneous bacteria in the raw material, so as to avoid the interference of the miscellaneous bacteria on the subsequent biological impurity removal process.

[0018] Preferably, the temperature of the high-temperature boiling is ≥95℃, for example, can be 95℃, 95.5℃, 96℃, 96.5℃, 97℃, 97.5℃, 98℃, 98.5℃, 99℃, 99.5℃ or 100℃, and is further preferably 100℃, and the time is 0.1-2h, for example, can be 0.1h, 0.2h, 0.4h, 0.6h, 0.8h, 1h, 1.2h, 1.4h, 1.6h, 1.8h or 2h, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0019] Preferably, the drying treatment mode comprises any one or a combination of at least two of reduced-pressure drying, air-drying, natural airing or freeze-drying, and a typical but non-limiting combination comprises a combination of reduced-pressure drying and air-drying, a combination of air-drying and natural airing, or a combination of natural airing and freeze-drying.

[0020] Preferably, the silicate bacteria in the silicate bacteria stock solution comprises any one or a combination of at least two of Bacillus mucilaginosus, Bacillus agri or Bacillus circulans, and a typical but non-limiting combination comprises a combination of Bacillus mucilaginosus and Bacillus agri, Bacillus agri and Bacillus circulans, Bacillus mucilaginosus and Bacillus circulans, or a combination of Bacillus mucilaginosus, Bacillus agri and Bacillus circulans.

[0021] In the present application, under the condition of not using strong corrosive acid and alkali (such as HF) and high-temperature reaction, the silicate bacteria metabolize to produce mixed organic acids, amino acids and polysaccharides, so that the insoluble potassium, phosphorus, magnesium, aluminum and silicon elements are fully dissolved out for the bacteria to utilize. Among them, the mixed organic acids can also react with metal ions (such as Al 3+ , Fe 3+) form stable chelates, further achieving the removal of metal elements in the biomass raw material; low-carbon organic matter such as polysaccharides will melt during the carbonization process, which can effectively fill the large-size pores in the biomass hard carbon precursor, thereby optimizing the pore distribution and enhancing the structural stability of the carbon skeleton, making it easier to form a rich closed microporous structure during the carbonization process, and thus providing more storage sites and more efficient diffusion channels for sodium ions.

[0022] Preferably, the concentration of bacteria in the silicate bacteria stock solution is (1-100) x 10 6 / mL, for example, it can be 1 x 10 6 / mL, 10 x 10 6 / mL, 20 x 10 6 / mL, 30 x 10 6 / mL, 40 x 10 6 / mL, 50 x 10 6 / mL, 60 x 10 6 / mL, 70 x 10 6 / mL, 80 x 10 6 / mL, 90 x 10 6 / mL or 100 x 10 6 / mL, but not limited to the listed values, other values not listed in this range are also applicable.

[0023] By limiting the concentration range of bacteria in the silicate bacteria stock solution, the present application well balances the metabolic activity of bacteria and production cost. When the concentration of bacteria is too low, the metabolic activity of bacteria is insufficient, resulting in low degradation efficiency, prolonged processing period, and easy breeding of harmful bacteria due to environmental interference; when the concentration of bacteria is too high, i.e. the amount of bacteria added is too much, the cost of the biomass raw material fermentation process is increased, which is not conducive to large-scale production and application.

[0024] Preferably, the mixing mass ratio of the biomass raw material and the silicate bacteria stock solution is 1:(5-100), for example, it can be 1:5, 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90 or 1:100, but not limited to the listed values, other values not listed in this range are also applicable.

[0025] Preferably, the temperature of the constant temperature culture is 10-50℃, for example, it can be 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃ or 50℃, and the time is 0.5-4 days, for example, it can be 0.5 days, 1 day, 1.5 days, 2 days, 2.5 days, 3 days, 3.5 days or 4 days, but not limited to the listed values, other values not listed in this range are also applicable.

[0026] In the present application, both the temperature and the time of the constant temperature culture are crucial. If the culture time is too short, the reaction cannot be fully carried out; if the culture time is too long, the bacterial activity is reduced, time is wasted and the cost is increased. Both too high or too low culture temperature will reduce the bacterial activity, thereby affecting the impurity removal efficiency.

[0027] Preferably, the washing liquid used in the washing comprises deionized water.

[0028] Preferably, the washing is followed by a drying process.

[0029] The present application uses deionized water to repeatedly wash the biomass raw material after biological impurity removal, completely removes the silicate bacteria liquid remaining on the surface of the raw material and the inorganic salts, ash and other impurities decomposed from the biomass raw material during the fermentation process, and then dries again to obtain pure impurity-removed biomass raw material.

[0030] Preferably, the carbonization method comprises segmented carbonization, specifically comprising low-temperature carbonization and high-temperature carbonization performed in sequence.

[0031] Preferably, the segmented carbonization is performed in an inert atmosphere, and the inert atmosphere comprises any one or a combination of at least two of nitrogen, argon or helium, and a typical but non-limiting combination comprises a combination of nitrogen and argon, a combination of argon and helium, a combination of nitrogen and helium, or a combination of nitrogen, argon and helium.

[0032] Preferably, the temperature of the low-temperature carbonization is 300-600℃, for example, it can be 300℃, 350℃, 400℃, 450℃, 500℃, 550℃ or 600℃, and the time is 3-6h, for example, it can be 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h, but it is not limited to the listed values, and other values not listed in this range are also applicable.

[0033] The present application removes volatile components and oxygen-containing groups in the raw material by low-temperature carbonization. If the temperature is too high, the volatile components will be released violently, the natural skeleton structure of the biomass will be damaged, the pore will collapse and the specific surface area will decrease, and excessive crosslinking will reduce the number of closed pores required for sodium storage. If the temperature is too low, it is difficult to effectively remove the volatile components and oxygen-containing groups, and the residual impurities will cause structural disorder in the subsequent high-temperature carbonization, thereby reducing the carbon yield and conductivity. At the same time, if the time is too long, energy will be wasted and excessive carbonization will easily occur, causing the pores to shrink or even close; if the time is too short, the reaction will not be sufficient, and the residual volatile components will cause structural damage during the subsequent high-temperature carbonization, thereby reducing the performance of the material.

[0034] Preferably, the high-temperature carbonization temperature is 1000-1600℃, for example, it can be 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, 1450℃, 1500℃, 1550℃ or 1600℃, and the time is 2-10h, for example, it can be 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h, but not limited to the listed values, other values in the range are also applicable.

[0035] The present application builds a stable carbon skeleton structure by high-temperature carbonization, forming sufficient interlayer embedded sodium storage sites. In the high-temperature carbonization process, if the temperature is too high, it will cause the interlayer spacing of the carbon layer in the hard carbon material to be too narrow, reducing the sodium storage active sites and porosity, thereby adversely affecting the electrochemical performance of the hard carbon material; if the temperature is too low, it is difficult to form a stable carbon skeleton structure, and it is not possible to form sufficient interlayer embedded sodium storage sites.

[0036] In a second aspect, the present application provides a biomass hard carbon negative electrode material, which is prepared by the preparation method of the first aspect.

[0037] In a third aspect, the present application provides a battery, which contains at least the biomass hard carbon negative electrode material of the second aspect.

[0038] Compared with the prior art, the present application has the following beneficial effects:

[0039] (1) The preparation method provided by the present application arranges the impurity removal step before carbonization, effectively avoiding the damage to the micro-porous structure of the material caused by acid washing or alkali washing after carbonization in the traditional process, retaining the porous and loose characteristics of the biomass hard carbon, and making the biomass hard carbon material exhibit excellent sodium storage capacity.

[0040] (2) Silicate bacteria can specifically decompose insoluble impurities such as silicon and aluminum in hard carbon without damaging the carbon skeleton structure. Compared with traditional acid and alkali methods, the mixed organic acids produced by microbial metabolism can gently dissolve metal oxides, greatly reducing the damage to the material structure, and the low-carbon organic matter produced by metabolism can convert open pores in hard carbon into closed pore structures after melting, thereby constructing a rich micro-porous structure inside the hard carbon material and further improving the sodium storage active sites.

[0041] (3) The present application does not need to use strong corrosive acid and alkali in the impurity removal process, reducing the pollution to the environment. At the same time, the preparation process of the impurity removal biomass raw material is simple and economical, which can improve the economic benefits of the entire hard carbon material production chain. This green and environmentally friendly preparation process significantly reduces the production cost, fully meets the needs of the hard carbon material industry for efficient, low-damage and environmentally friendly impurity removal technology. DETAILED DESCRIPTION

[0042] The technical solutions of the present application are further illustrated by specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application, and should not be regarded as specific limitations on the present application.

[0043] Embodiment 1

[0044] The present embodiment provides a biomass hard carbon negative electrode material and a preparation method thereof, which specifically comprises the following steps:

[0045] (1) After the coconut shell raw material is crushed, it is boiled in a constant temperature water bath (deionized water) at 100°C for 1h to completely kill the miscellaneous bacteria in the raw material; after sterilization is completed, the material is naturally cooled to room temperature, and then dried at 100°C;

[0046] (2) According to the mixing mass ratio of 1:50, the coconut shell raw material powder obtained in step (1) is immersed in a Bacillus Malleus stock solution with a bacterial concentration of 10×10 6 / mL, and incubated at 25°C for 2 days;

[0047] (3) The coconut shell raw material powder obtained in step (2) is repeatedly washed with deionized water, and then dried at 100°C to obtain the impurity-removed coconut shell raw material powder;

[0048] (4) The impurity-removed coconut shell raw material powder obtained in step (3) is placed in a nitrogen atmosphere, first carbonized at 500°C for 3h, and then carbonized at 1300°C for 5h, and naturally cooled to obtain a biomass hard carbon negative electrode material with low impurities.

[0049] Embodiment 2

[0050] The present embodiment provides a biomass hard carbon negative electrode material and a preparation method thereof, except that the mixing mass ratio of the coconut shell raw material powder and the Bacillus Malleus stock solution in step (2) is changed to 1:20, the remaining steps and conditions are the same as those in Embodiment 1, and are not repeated here.

[0051] Embodiment 3

[0052] The present embodiment provides a biomass hard carbon negative electrode material and a preparation method thereof, except that the bacterial concentration of the Bacillus Malleus stock solution in step (2) is changed to 5×10 6 / mL, the remaining steps and conditions are the same as those in Embodiment 1, and are not repeated here.

[0053] Embodiment 4

[0054] The present embodiment provides a biomass hard carbon negative electrode material and a preparation method thereof, except that the incubation time in step (2) is changed to 1 day, the remaining steps and conditions are the same as those in Embodiment 1, and are not repeated here.

[0055] Example 5

[0056] This example provides a biomass hard carbon negative electrode material and a preparation method thereof, wherein the temperature for constant temperature culture in step (2) is changed to 50°C, and the remaining steps and conditions are the same as those in Example 1, which are not repeated here.

[0057] Example 6

[0058] This example provides a biomass hard carbon negative electrode material and a preparation method thereof, wherein the biomass raw material is changed to bamboo, and the remaining steps and conditions are the same as those in Example 1, which are not repeated here.

[0059] Example 7

[0060] This example provides a biomass hard carbon negative electrode material and a preparation method thereof, wherein the biomass raw material is changed to straw, and the remaining steps and conditions are the same as those in Example 1, which are not repeated here.

[0061] Comparative Example 1

[0062] This comparative example provides a biomass hard carbon negative electrode material and a preparation method thereof, which specifically includes the following steps:

[0063] (1) After crushing the coconut shell raw material, it is boiled in a constant temperature water bath (deionized water) at 100°C for 1h to completely kill the miscellaneous bacteria in the raw material; after sterilization is completed, the material is naturally cooled to room temperature, and then dried at 100°C;

[0064] (2) The coconut shell raw material powder obtained in step (1) is placed in a nitrogen atmosphere, first carbonized at 500°C for 3h, then carbonized at 1300°C for 5h, and naturally cooled to obtain a biomass hard carbon negative electrode material.

[0065] Comparative Example 2

[0066] This comparative example provides a biomass hard carbon negative electrode material and a preparation method thereof, which specifically includes the following steps:

[0067] (1) After crushing the coconut shell raw material, it is boiled in a constant temperature water bath (deionized water) at 100°C for 1h to completely kill the miscellaneous bacteria in the raw material; after sterilization is completed, the material is naturally cooled to room temperature, and then dried at 100°C;

[0068] (2) The coconut shell raw material powder obtained in step (1) is placed in a nitrogen atmosphere, first carbonized at 500°C for 3h, then transferred to a 1 mol / L hydrochloric acid solution, acid washed at 50°C for 12h, centrifuged and washed to neutral, then carbonized at 1300°C for 5h, and naturally cooled to obtain a biomass hard carbon negative electrode material.

[0069] Comparative Example 3

[0070] The present comparative example provides a biomass hard carbon negative electrode material and a preparation method thereof, specifically comprising the following steps:

[0071] (1) After the coconut shell raw material is crushed, it is boiled in a constant temperature water bath (deionized water) at 100°C for 1 h to completely kill the miscellaneous bacteria in the raw material. After sterilization is completed, the material is naturally cooled to room temperature, and then dried at 100°C;

[0072] (2) The coconut shell raw material powder obtained in step (1) is placed in a nitrogen atmosphere, first carbonized at 500°C for 3 h, then transferred to a 1 mol / L sodium hydroxide solution, washed with alkali at 50°C for 12 h, centrifuged and washed to neutral, and then high-temperature carbonized at 1300°C for 5 h, and then naturally cooled to obtain a biomass hard carbon negative electrode material.

[0073] Comparative Example 4

[0074] The present comparative example provides a biomass hard carbon negative electrode material and a preparation method thereof, specifically comprising the following steps:

[0075] (1) After the coconut shell raw material is crushed, it is boiled in a constant temperature water bath (deionized water) at 100°C for 1 h to completely kill the miscellaneous bacteria in the raw material. After sterilization is completed, the material is naturally cooled to room temperature, and then dried at 100°C;

[0076] (2) The coconut shell raw material powder obtained in step (1) is placed in a nitrogen atmosphere, first carbonized at 500°C for 3 h, then transferred to a 1 mol / L sodium hydroxide solution, washed with alkali at 50°C for 12 h, centrifuged and washed to neutral, and then high-temperature carbonized at 1300°C for 5 h, and then naturally cooled to obtain a biomass hard carbon negative electrode material.

[0077] Performance test:

[0078] Sodium ion battery preparation and electrical performance test: the hard carbon material, Super P, CMC, SBR are mixed into a uniform slurry in a mass ratio of 94:1.5:2:2.5, then the black slurry is coated on a copper foil using a 120 μm four-side coater, and then the film is dried in a 100°C vacuum drying oven for 2 h. 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, 1M NaClO4 (EC:DEC=1:1 Vol%) solution is used as the electrolyte, and PP / PE / PP three-layer separator is used as the separator, and CR2016 type button cell is assembled in a glove box. The above button cell is subjected to constant current charge and discharge test, the current density is 0.1C (1C=300 mAh / g), and the voltage range is 0-2V.

[0079] The relevant test results are shown in Table 1 below.

[0080] Table 1

[0081]

[0082] According to Table 1 above, the following conclusions can be drawn:

[0083] (1) According to the test results of Examples 1-5, it can be seen that the charge specific capacity of the hard carbon material obtained in Examples 1-5 is relatively high, indicating that under the appropriate mass ratio of biomass raw material powder to silicate bacterial stock solution, temperature range, culture time and concentration of bacterial solution, the silicate bacteria can dissolve the metal element impurities and silicon element impurities in the biomass raw material powder. If the concentration of the bacterial solution is too low, or the constant temperature culture temperature is too high, or the soaking time is too short, the activity of the silicate bacteria will be affected, and then the impurity removal efficiency will be affected.

[0084] (2) According to the test results of Example 1 and Examples 6-7, it can be seen that the first cycle charge specific capacity of the sodium ion battery corresponding to the hard carbon material obtained in these three examples is 301.4-302.5 mAh / g, and the first cycle coulombic efficiency is 93.2%-94.4%, both of which have relatively high first cycle charge specific capacity and first cycle coulombic efficiency, indicating that the silicate bacteria impurity removal method is suitable for different types of biomass hard carbon raw materials.

[0085] (3) According to the test results of Example 1 and Comparative Example 1, it can be seen that compared with the biomass hard carbon which has not been treated by silicate bacteria, the first cycle charge specific capacity of the biomass hard carbon treated by silicate bacteria is significantly improved, indicating that the silicate bacteria can effectively remove the impurities in the biomass hard carbon material and improve the electrochemical reaction efficiency of the material. At the same time, the polysaccharides and other low-carbon organic matter generated by the metabolism of silicate bacteria will melt during the carbonization process, which can effectively fill the large-size pores in the biomass hard carbon precursor, thereby optimizing the pore distribution, enhancing the structural stability of the carbon skeleton, making the carbonization process more easily form rich closed micropore structure, and improving the sodium storage active site.

[0086] (4) According to the test results of Example 1 and Comparative Examples 2-3, it can be seen that compared with the biomass hard carbon treated by acid washing or alkali washing, the biomass hard carbon treated by silicate bacteria has more excellent performance, specifically higher first cycle charge specific capacity and first cycle coulombic efficiency, indicating that the silicate bacteria impurity removal can also achieve deep impurity removal. More importantly, the acid washing or alkali washing method will damage the micropore structure of the material and affect the sodium storage capacity of the material. In contrast, the biological impurity removal technology can not only effectively retain the intrinsic porous structure of the material, but also remove impurities, thereby improving the electrochemical performance of the hard carbon material.

[0087] (5)It can be seen from the test results of Example 1 and Comparative Example 4 that, compared with the acid-alkali combined cleaning method, the biomass hard carbon treated by the silicate bacteria has similar first cycle specific capacity and higher first cycle coulombic efficiency, which further shows that the silicate bacteria metabolites can convert the open pores in the hard carbon into closed pore structures, build rich micropore structures in the hard carbon material, and further improve the sodium storage active sites. At the same time, the silicate bacteria treatment step is arranged before the carbonization treatment, thereby avoiding the damage of the micropore structure of the material after the carbonization and acid washing or alkali washing process, and reducing the acid-alkali waste liquid treatment link, greatly reducing the environmental protection treatment cost, and realizing the green and environmental protection of the hard carbon.

[0088] Therefore, the silicate bacteria is used to specifically biologically remove impurities from the hard carbon biomass precursor in the present application, the mixed organic acids produced by microbial metabolism can gently dissolve metal oxides, greatly reducing the damage to the material structure, avoiding the structural damage of the carbon skeleton by the traditional acid-alkali method; the melting characteristics of the bacterial metabolites in the carbonization process are used to convert the open pores in the hard carbon into closed pore structures, build rich micropore structures in the hard carbon material, and further improve the sodium storage active sites.

[0089] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a biomass hard carbon negative electrode material, characterized in that, The preparation method comprises sterilization treatment, silicate bacterial biological impurity removal, washing and carbonization of the biomass raw material in sequence. The silicate bacterial biological impurity removal comprises immersing the biomass raw material in a silicate bacterial stock solution for constant temperature culture.

2. The method for preparing the biomass hard carbon anode material according to claim 1, characterized in that, The biomass raw material comprises any one or a combination of at least two of coconut shell, bamboo, straw, wood, nut shell, starch, bagasse, corn cob, rice husk, peanut shell, starch or lignin.

3. The method of claim 1 or 2, wherein the biomass hard carbon negative electrode material is prepared by the following steps: (1) mixing biomass and carbon source to form a mixture; (2) heating the mixture to obtain a biomass hard carbon negative electrode material. The sterilization treatment comprises high-temperature cooking, specifically, crushing the biomass raw material, distilling and / or boiling the crushed biomass raw material with deionized water, and drying after cooling.

4. The method for preparing the biomass hard carbon anode material according to claim 3, characterized in that, The high-temperature cooking is performed at a temperature of 95 DEG C or higher for 0.1-2 hours. The drying treatment comprises any one or a combination of at least two of reduced-pressure drying, air-drying, natural airing or freeze-drying.

5. The method of claim 1 or 2, wherein the biomass hard carbon negative electrode material is prepared by the following steps: (1) mixing biomass and carbon source to form a mixture; (2) heating the mixture to obtain a biomass hard carbon negative electrode material. The silicate bacteria in the silicate bacterial stock solution comprise any one or a combination of at least two of Bacillus mucilaginosus, Bacillus agri or Bacillus circulans. And / or, the concentration of bacteria in the silicate bacteria stock solution is (1-100) x 10 6 bacteria / mL. The mixing mass ratio of the biomass raw material to the silicate bacterial stock solution is 1:(5-100). The constant temperature culture is performed at a temperature of 10-50 DEG C for 0.5-4 days.

6. The method for preparing the biomass hard carbon anode material according to claim 1 or 2, characterized in that, The washing liquid used in the washing comprises deionized water. The drying treatment is performed after the washing.

7. The method for preparing the biomass hard carbon anode material according to claim 1 or 2, characterized in that, The carbonization comprises segmented carbonization, specifically, low-temperature carbonization and high-temperature carbonization in sequence. The segmented carbonization is performed in an inert atmosphere, and the inert atmosphere comprises any one or a combination of at least two of nitrogen, argon or helium.

8. The method for preparing the biomass hard carbon anode material according to claim 7, characterized in that, The low-temperature carbonization is performed at a temperature of 300-600 DEG C for 3-6 hours. The high-temperature carbonization is performed at a temperature of 1000-1600 DEG C for 2-10 hours.

9. A biomass hard carbon negative electrode material, characterized in that, The biomass hard carbon negative electrode material is prepared by the preparation method of any one of claims 1-8.

10. A battery, characterized by The battery comprises at least the biomass hard carbon negative electrode material of claim 9.

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