A method for preparing bio-based spherical porous carbon, a method for preparing bio-based spherical silicon-carbon anode material, and a battery.

Abstract

This application provides a method for preparing bio-based spherical porous carbon, a method for preparing bio-based spherical silicon-carbon anode material, and a battery. The method for preparing the bio-based spherical porous carbon includes: a precursor synthesis step; a drying and dehydration step; an alkaline activation pore-forming step; and a vapor-phase deashing step. The method for preparing the bio-based spherical silicon-carbon anode material further includes steps of silicon vapor-phase deposition and carbon vapor-phase coating of the bio-based spherical porous carbon. Through the above-mentioned method for preparing bio-based spherical porous carbon, bio-based spherical porous carbon with suitable and uniform pore size, regular spherical shape (good flowability), and high single-particle strength can be obtained. The bio-based spherical silicon-carbon anode material obtained by this method exhibits excellent effects such as lower resistivity and stronger confinement of internal silicon lithium intercalation expansion, enabling it to be used in batteries with better performance.

Description

Technical Field

[0001] This application belongs to the field of biomass refining and comprehensive utilization, specifically involving a method for preparing bio-based spherical porous carbon, a method for preparing bio-based spherical silicon-carbon anode material, and a battery. Background Technology

[0002] Most of the existing novel silicon-carbon anode materials use porous carbon as a substrate and perform vapor deposition in an atmosphere containing a silicon source to deposit nano-silicon into the porous carbon channels. Then, vapor coating is performed in an atmosphere containing a carbon source to coat the material surface with a carbon layer. The resulting silicon-carbon composite material, as a battery anode material, achieves high capacity and long cycle life while effectively improving the high expansion and low rate capability shortcomings of silicon-based anode materials.

[0003] This novel silicon-carbon material requires the deposition of nano-silicon into the pores of porous carbon. On the one hand, the pore structure of the porous carbon needs to have a good adsorption capacity for silicon source gas to ensure that the reaction process of silicon source gas decomposing into nano-silicon occurs inside the porous carbon pores. This places high demands on the structural parameters of the porous carbon. If the structure of the porous carbon is not ideal, silicon will be deposited on the material surface, resulting in floating silicon and a decrease in material processing performance and cycle life. On the other hand, the silicon source gas needs to have sufficient gas-solid contact with the porous carbon. This places high demands on the fluidity of the porous carbon material. If the material has poor fluidity, it is easy to agglomerate and clump in the equipment, resulting in uneven reaction during silicon vapor deposition and carbon vapor coating, and poor product performance.

[0004] Currently, porous carbon preparation often uses coconut shell carbon, resin, etc. as precursors. Activation methods include steam activation, CO2 activation, and alkali activation. The equipment used for activation includes kilns such as roller kilns and rotary kilns. Porous carbon prepared by different processes has different disadvantages. For example, porous carbon prepared by coconut shell carbon has low structural strength and poor pore structure consistency. The new silicon-carbon anode prepared has a high expansion rate and poor electrochemical performance. Resin-based activated carbon has high raw material costs. The pore structure of steam and CO2 activation is uncontrollable, which leads to poor cycle performance of the new silicon-carbon anode. Alkali activation has a complex pore-forming process, high product ash content, and difficult wastewater treatment.

[0005] Since silicon vapor deposition and carbon vapor coating need to be carried out at a certain gas flow rate, there are strict requirements on the particle size distribution of porous carbon. If the Dv10 of porous carbon is too low and there are too many small-sized fine powders, it will significantly affect the effect of silicon deposition and carbon coating, resulting in poor product performance. Therefore, after the porous carbon is prepared and before silicon vapor deposition, it is necessary to crush and classify the porous carbon. Summary of the Invention

[0006] To address the problems in the prior art, this application provides a method for preparing bio-based spherical porous carbon, a method for preparing bio-based spherical silicon-carbon anode materials from the aforementioned bio-based spherical porous carbon, and a method for preparing batteries from the aforementioned bio-based spherical silicon-carbon anode materials. The technical solution of this application is as follows:

[0007] 1. A method for preparing bio-based spherical porous carbon, comprising:

[0008] Precursor synthesis steps: Add crosslinking agent and dispersant to papermaking black liquor, and prepare slurry containing bio-based microspheres by sol-gel method. The papermaking black liquor is papermaking black liquor produced by alkaline papermaking.

[0009] Drying and dehydration step: The slurry is dried and dehydrated under a protective atmosphere to obtain dried and dehydrated bio-based microspheres;

[0010] Alkali activation pore-forming step: Under a protective atmosphere and activation temperature, the dried and dehydrated bio-based microspheres are activated by alkali using the alkaline pore-forming agent they contain.

[0011] Gas-phase deashing step: An acidic gas is added under a protective atmosphere to cause the acidic gas and impurities to form salt and be vaporized and removed, thereby obtaining the bio-based spherical porous carbon.

[0012] 2. The preparation method as described in item 1, wherein,

[0013] The solid content of the papermaking black liquor is 30% to 60%;

[0014] The papermaking black liquor has a pH ≥ 11.0, preferably a pH ≥ 12.0; and / or,

[0015] The Na content of the papermaking black liquor is between 200,000 and 400,000 ppm, preferably between 230,000 and 250,000 ppm.

[0016] 3. The preparation method as described in item 1, wherein,

[0017] The crosslinking agent is selected from any one or a combination of two or more of toluene, phenol, resorcinol, formaldehyde, paraformaldehyde, hexamethylenetetramine, and azobisisobutyronitrile; preferably, the crosslinking agent is added at a mass of 1-20% of the black liquor mass; and / or,

[0018] The dispersant is selected from one or more of gelatin, polyvinyl alcohol, polyethylene glycol, white oil, polyvinylpyrrolidone, sodium polyacrylate, and sorbitan oleate; preferably, the dispersant is added at a mass of 0.1-20% of the black liquor mass.

[0019] 4. The preparation method as described in item 1, wherein,

[0020] The precursor synthesis step is carried out in a closed reactor; the heating temperature is 170-190℃, preferably 175-185℃; the heating time is ≥18h, preferably 22-24h.

[0021] 5. The preparation method as described in item 1, wherein,

[0022] The drying and dehydration step is carried out in an activated fluidized bed; the drying and dehydration step includes a drying sub-step and a dehydration sub-step performed after the drying sub-step; wherein...

[0023] In the drying sub-step, the slurry is sprayed into the activated fluidized bed through a two-fluid atomizing nozzle under a protective atmosphere; the drying temperature is 100-150℃, preferably 110-120℃; the drying time after all the slurry has entered the activated fluidized bed is 0.5-6 hours.

[0024] The dehydration temperature of the dehydration sub-step is 200–800℃, preferably 300–600℃; the dehydration time is 0.5–6h.

[0025] 6. The preparation method as described in item 1, wherein,

[0026] The alkaline activation pore-forming step is carried out in an activated fluidized bed.

[0027] The activation temperature is 600–1100℃, preferably 750–950℃;

[0028] The activation time is 0.5 to 24 hours.

[0029] 7. The preparation method as described in item 6, wherein,

[0030] In the alkaline activation pore-forming step, an inert gas, the protective atmosphere, is continuously introduced from the bottom of the gas-activated fluidized bed.

[0031] 8. The preparation method as described in item 1, wherein,

[0032] The gas-phase deashing step is carried out in an activated fluidized bed;

[0033] The gas-phase deashing temperature is 400–1100℃, preferably 650–950℃;

[0034] The deashing time is 0.5 to 6 hours.

[0035] 9. The preparation method as described in item 1, wherein,

[0036] The acidic gas originates from halogen elements and / or halogen compounds; wherein,

[0037] The halogen is selected from any one or a combination of two or more of fluorine, chlorine, bromine and iodine, preferably chlorine gas;

[0038] The halogen compound is selected from any one or a combination of two or more of hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, chlorine fluoride, iodine chloride, iodine bromide, bromine chloride, and acidic precursor compounds, preferably hydrogen chloride; wherein the acidic precursor compound can decompose upon heating during the alkaline activation pore-forming step to produce at least one of hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, chlorine fluoride, iodine chloride, iodine bromide, and bromine chloride.

[0039] 10. A method for preparing a bio-based spherical silicon-carbon anode material, comprising using the bio-based spherical porous carbon prepared by any one of the methods for preparing bio-based spherical porous carbon according to claims 1 to 9, including:

[0040] Silicon vapor deposition step: Silicon source gas is introduced under a protective atmosphere to deposit silicon on the bio-based spherical porous carbon to obtain bio-based spherical porous carbon with nano-silicon deposition;

[0041] Carbon vapor phase coating step: Carbon source gas is introduced under a protective atmosphere to carbon coat the bio-based spherical porous carbon deposited on the nano-silicon, thereby obtaining the bio-based spherical silicon-carbon anode material.

[0042] 11. The preparation method as described in item 10, wherein,

[0043] In the silicon vapor deposition step, the silicon vapor deposition temperature is 450–650°C, preferably 500–550°C; and / or,

[0044] In the carbon gas phase coating step, the carbon coating temperature is 450–700℃, preferably 500–650℃.

[0045] 12. The preparation method as described in item 11, wherein,

[0046] The silicon vapor deposition step is carried out in a deposition fluidized bed;

[0047] The silicon source gas introduced under a protective atmosphere is:

[0048] A mixture of the protective atmosphere gas and the silicon source gas is introduced from the bottom of the deposition fluidized bed; the volume ratio of the protective atmosphere gas to the silicon source gas in the mixture is 10:(0.1~10).

[0049] 13. The preparation method as described in item 11, wherein,

[0050] The carbon vapor phase coating step is carried out in a deposition fluidized bed;

[0051] The carbon source gas introduced under a protective atmosphere is:

[0052] A mixture of the protective atmosphere gas and the carbon source gas is introduced from the bottom of the deposition fluidized bed; the volume ratio of the protective atmosphere gas to the carbon source gas in the mixture is 10:(0.1~10).

[0053] 14. The preparation method as described in item 10, wherein,

[0054] The silicon source gas is selected from silanes and / or chlorosilanes; and / or,

[0055] The carbon source gas is selected from one or more of alkanes, alkenes, alkynes, and carbon oxides.

[0056] 15. A battery comprising:

[0057] The bio-based spherical silicon-carbon anode material prepared by any of the preparation methods of bio-based spherical silicon-carbon anode materials in items 10 to 14.

[0058] The method for preparing bio-based spherical porous carbon provided in this application yields bio-based spherical porous carbon with suitable and uniform pore size, regular spherical shape (good flowability), and high single-particle strength. This expands the application range of papermaking black liquor, turning waste into treasure and increasing the added value of papermaking black liquor. Furthermore, the method for preparing bio-based spherical silicon-carbon anode material in this application further involves silicon vapor deposition and carbon vapor coating on the basis of the aforementioned bio-based spherical porous carbon, thereby obtaining a bio-based spherical silicon-carbon anode material. This bio-based spherical silicon-carbon anode material exhibits excellent effects such as lower resistivity and stronger confinement of internal silicon lithium intercalation expansion, enabling it to be used in batteries with better performance.

[0059] The above description is merely an overview of the technical solution of this application. In order to make the technical means of this application clearer and more understandable, so that those skilled in the art can implement it according to the contents of the specification, and in order to make the above and other objects, features and advantages of this application more obvious and understandable, the following is an example of a specific implementation of this application. Attached Figure Description

[0060] Figure 1 Electron micrograph of porous carbon, the intermediate product of Example 1;

[0061] Figure 2 Electron micrograph of the intermediate porous carbon from Example 2;

[0062] Figure 3 Electron micrograph of the intermediate porous carbon of Example 3;

[0063] Figure 4 Electron micrograph of the intermediate porous carbon of Example 4;

[0064] Figure 5 Electron micrograph of the intermediate porous carbon of Example 5;

[0065] Figure 6 Electron micrograph of the intermediate porous carbon of Example 6;

[0066] Figure 7 Electron micrograph of the product obtained from the precursor synthesis step of Comparative Example 1;

[0067] Figure 8 Electron micrograph of the product obtained from the precursor synthesis step in Comparative Example 2;

[0068] Figure 9 Electron micrograph of the product obtained from the precursor synthesis step in Comparative Example 3;

[0069] Figure 10 Electron micrograph of the product obtained from the precursor synthesis step in Comparative Example 4;

[0070] Figure 11 Electron micrograph of the product obtained from the precursor synthesis step in Comparative Example 5;

[0071] Figure 12 Electron micrograph of the product obtained from the precursor synthesis step in Comparative Example 6;

[0072] Figure 13 Electron micrograph of commercially available coconut shell-based porous carbon (Comparative Example 7);

[0073] Figure 14 Electron micrograph of commercially available pitch-based porous carbon, Comparative Example 8. Detailed Implementation

[0074] The best mode of the invention will be shown and described below. Unless otherwise defined, all terms and scientific and technical terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any inconsistency, this application (including the definitions) takes precedence.

[0075] The following appropriately explains the definitions of terms and / or basic technical content used in particular in this specification.

[0076] In this application, "papermaking black liquor" refers to the wastewater generated by the alkaline (caustic soda) pulping process in the papermaking industry. It contains large amounts of lignin, hemicellulose, pigments, pentoses, nitrogen, phosphorus, potassium, and other dissolved substances. Because the wastewater is dark brown, it is called papermaking black liquor. Raw materials used in papermaking, such as straw, contain substances such as cellulose, lignin, and hemicellulose. Papermaking only utilizes the cellulose (approximately 40%), while approximately 25% lignin, 28% hemicellulose, pigments, pentoses, nitrogen, phosphorus, and potassium are discarded along with the papermaking black liquor. Because papermaking black liquor contains large amounts of suspended solids, organic pollutants, and toxic substances, direct discharge into water bodies would cause serious pollution. Its main hazards include: papermaking wastewater containing large amounts of fiber, pigments and inorganic salts will turn water bodies black and have a special foul odor; the biochemical oxygen demand (BOD) of papermaking black liquor containing high concentrations of organic pollutants can be as high as 5,000 to 40,000 g / L, which will consume a large amount of dissolved oxygen in the water and affect water quality; the large amount of alkaline substances present in papermaking black liquor will cause the pH value of the water body to rise sharply, disrupting the balance of the aquatic environment.

[0077] In this application, "drying" refers to evaporating water, and "dehydration" refers to removing the water of crystallization from structures such as alkali salts at high temperatures.

[0078] In this application, "alkaline pore-forming agent" refers to an additive that forms a porous structure by adding an alkaline substance that can decompose or burn off at high temperatures or under specific conditions during the material preparation process. Examples of such additives include sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate. For this application, the "alkaline pore-forming agent" contained in the "papermaking black liquor" generally includes sodium hydroxide; that is, the "alkaline pore-forming agent" abundant in the "bio-based microspheres" themselves generally includes sodium hydroxide.

[0079] In this application, "protective atmosphere" refers to protection using nitrogen and / or rare gases. Those skilled in the art will know that rare gases include, for example, helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe). From an economic perspective, this application preferably uses nitrogen as the protective atmosphere gas.

[0080] In this application, the "sol-gel method" refers to using a compound containing highly chemically active components as a precursor, uniformly mixing these raw materials in the liquid phase, and carrying out hydrolysis and condensation chemical reactions. Under a specific solvent system, the precursor forms a gel with a three-dimensional network structure, and aggregates into spherical shapes under the action of reverse phase to form gel microspheres.

[0081] In this application, "activated fluidized bed" refers to a low-speed fluidized bed in which a high-speed gas flow is introduced through a gas distributor at the bottom of the fluidized bed, causing solid particles to enter a fluidized state and make full contact with the gas.

[0082] In this application, "depositional fluidized bed" refers to a low-speed stirred fluidized bed in which a high-speed gas flow is introduced through a gas distributor at the bottom of the fluidized bed, and the dispersion effect of the stirring paddle at the bottom causes solid particles to enter a fluidized state and make full contact with the gas.

[0083] The embodiments provided below are provided to better understand the present invention, and the scope of this application should not be limited to the following description. Therefore, it is apparent to those skilled in the art that appropriate modifications can be made within the scope of the present invention with reference to the description herein. Furthermore, the following embodiments of the present invention can be used alone or in combination.

[0084] In one aspect of this application, a method for preparing bio-based spherical porous carbon is provided, comprising: a precursor synthesis step: adding a crosslinking agent and a dispersant to papermaking black liquor, and preparing a slurry containing bio-based microspheres by a sol-gel method, wherein the papermaking black liquor is papermaking black liquor produced by alkaline papermaking; a drying and dehydration step: drying and dehydrating the slurry under a protective atmosphere to obtain dried and dehydrated bio-based microspheres; an alkaline activation and pore-forming step: alkali activation of the dried and dehydrated bio-based microspheres using an alkaline pore-forming agent rich in them under a protective atmosphere and activation temperature; and a gas-phase deashing step: adding an acidic gas under a protective atmosphere to generate salt from the acidic gas and impurities, which is then vaporized and removed to obtain the bio-based spherical porous carbon.

[0085] Direct discharge of papermaking black liquor without effective treatment not only severely pollutes the environment but also wastes a large amount of resources. The inventors of this application creatively utilize the characteristic of industrial alkaline papermaking black liquor being rich in both biomass and alkaline substances. By employing a sol-gel method and adding crosslinking agents and dispersants, biomass is polymerized into gel microspheres in an alkaline environment. Further post-processing yields bio-based spherical porous carbon with suitable and uniform pore size, regular spherical shape (good flowability), and high single-particle strength. This bio-based spherical porous carbon can be used as an intermediate product in battery anode materials, as described below, to obtain battery anode materials with lower resistivity and stronger constraint on the internal silicon lithium intercalation expansion of silicon-carbon anodes, thereby improving battery performance. Alternatively, those skilled in the art can utilize its characteristics in other fields. Simultaneously, the technical solution of this embodiment expands the application range of papermaking black liquor, turning waste into treasure and increasing its added value.

[0086] In one embodiment, the solid content of the papermaking black liquor is 30% to 60% (e.g., it can be 30%, 35%, 40%, 45%, 55%, or 60%).

[0087] In one embodiment, the papermaking black liquor has a pH ≥ 11.0, preferably a pH ≥ 12.0.

[0088] In one embodiment, the Na content of the papermaking black liquor is between 200,000 and 400,000 ppm (e.g., it can be 200,000 ppm, 250,000 ppm, 300,000 ppm, 350,000 ppm, or 400,000 ppm), preferably between 230,000 and 250,000 ppm.

[0089] In one embodiment, the crosslinking agent is selected from any one or a combination of two or more of toluene, phenol, resorcinol, formaldehyde, paraformaldehyde, hexamethylenetetramine, and azobisisobutyronitrile; preferably, the crosslinking agent is added at a mass of 1 to 20% of the mass of the papermaking black liquor (e.g., it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%).

[0090] In one embodiment, the dispersant is selected from one or more combinations of gelatin, polyvinyl alcohol, polyethylene glycol, white oil, polyvinylpyrrolidone, sodium polyacrylate, and sorbitan oleate; preferably, the dispersant is added at a mass of 0.1% to 20% of the mass of the papermaking black liquor (e.g., it can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%).

[0091] In one embodiment, the precursor synthesis step is carried out in a closed reactor; the heating temperature is 170–190°C (e.g., 170°C, 172°C, 174°C, 176°C, 178°C, 180°C, 182°C, 184°C, 186°C, 188°C, 190°C), preferably 175–185°C; the heating time is ≥18 h, preferably 22–24 h; and the particle size distribution Dv50 of the obtained spherical particles is between 3 and 15 μm (e.g., 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm), preferably 5–9 μm. Currently, the particle size distribution of graphite in the negative electrode of various battery cells is between 5 and 9 μm. Therefore, when spherical particles with a particle size distribution of 5 to 9 μm are used as silicon-carbon particles for compound graphite, they are similar in size to graphite particles and are easier to directly introduce into the existing production system. If the particles are too large, scratches are likely to occur after electrode coating, which is not conducive to the yield. If the particles are too small, fine powder agglomeration will occur, which is not conducive to homogenization.

[0092] In one embodiment, the drying and dehydration step is carried out in an activated fluidized bed; the drying and dehydration step includes a drying sub-step and a dehydration sub-step performed after the drying sub-step; wherein, in the drying sub-step, the slurry is sprayed into the activated fluidized bed through a two-fluid atomizing nozzle under a protective atmosphere; the drying temperature is 100-150°C (e.g., 100°C, 110°C, 120°C, 130°C, 140°C, 150°C), preferably 110-120°C; the slurry is fully dried. The drying time after the part enters the activated fluidized bed is 0.5 to 6 hours (e.g., 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours); the dehydration temperature of the dehydration sub-step is 200 to 800°C (e.g., 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C), preferably 300 to 600°C; the dehydration time is 0.5 to 6 hours (e.g., 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours). Regarding the flow rate of the protective atmosphere gas in this step, those skilled in the art can set it specifically according to the circumstances. In this embodiment, the linear velocity of the protective atmosphere gas is 0.03 to 0.1 m / s, preferably 0.04 to 0.07 m / s.

[0093] In one embodiment, the alkali activation pore-forming step is carried out in an activated fluidized bed; the activation temperature is set to 600-1100℃ (e.g., 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃), preferably 750-950℃; the activation time is 0.5-24h (e.g., 0.5h, 1h, 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h).

[0094] In one embodiment, during the alkali activation pore-forming step, an inert gas, forming the protective atmosphere, is continuously introduced from the bottom of the gas-activated fluidized bed. The flow rate of the protective atmosphere gas in this step can be specifically set by those skilled in the art according to the circumstances. In this embodiment, the linear velocity of the protective atmosphere gas is 0.03–0.1 m / s, preferably 0.04–0.07 m / s.

[0095] In one embodiment, the gas-phase deashing step is carried out in an activated fluidized bed; the gas-phase deashing temperature is 400-1100℃ (e.g., 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃), preferably 650-950℃; the deashing time is 0.5-6h (e.g., 0.5h, 1h, 2h, 3h, 4h, 5h, 6h).

[0096] In one embodiment, the acidic gas originates from a halogen element and / or a halogen compound; wherein the halogen element is selected from any one or a combination of two or more of fluorine, chlorine, bromine, and iodine, preferably chlorine; the halogen compound is selected from any one or a combination of two or more of hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, chlorine fluoride, iodine chloride, iodine bromide, bromine chloride, and acidic precursor compounds, preferably hydrogen chloride; wherein the acidic precursor compound can decompose upon heating during the alkaline activation pore-forming step to produce at least one of hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, chlorine fluoride, iodine chloride, iodine bromide, and bromine chloride.

[0097] In one aspect of this application, a method for preparing a bio-based spherical silicon-carbon anode material is provided, which uses the bio-based spherical porous carbon prepared by any of the above embodiments, comprising: a silicon vapor deposition step: introducing a silicon source gas under a protective atmosphere to deposit silicon on the bio-based spherical porous carbon to obtain nano-silicon deposited bio-based spherical porous carbon; and a carbon vapor coating step: introducing a carbon source gas under a protective atmosphere to coat the nano-silicon deposited bio-based spherical porous carbon with carbon to obtain the bio-based spherical silicon-carbon anode material.

[0098] This embodiment, based on the bio-based spherical porous carbon provided in the above embodiments, further performs silicon vapor deposition and carbon vapor coating to obtain a bio-based spherical silicon-carbon anode material. Because the bio-based spherical porous carbon obtained in the above embodiments has characteristics such as suitable pore size, uniform pore size, regular spherical shape (good flowability), and high single-particle strength, the bio-based spherical silicon-carbon anode material obtained in this embodiment exhibits excellent effects such as lower resistivity and stronger confinement of internal silicon lithium intercalation expansion, enabling it to be used to obtain batteries with better performance.

[0099] In one embodiment, the silicon vapor deposition temperature in the silicon vapor deposition step is 450–650°C (e.g., 450°C, 500°C, 550°C, 600°C, 650°C), preferably 500–550°C.

[0100] In one embodiment, the carbon vapor phase coating step is performed at a carbon coating temperature of 450–700°C (e.g., 450°C, 500°C, 550°C, 600°C, 650°C, or 700°C), preferably 500–650°C.

[0101] In one embodiment, the silicon vapor deposition step is performed in a fluidized bed; the silicon source gas introduced under a protective atmosphere is a mixture of the protective atmosphere gas and the silicon source gas introduced from the bottom of the fluidized bed; the volume ratio of the protective atmosphere gas to the silicon source gas in the mixture is 10:(0.1 to 10) (for example, it can be 10:01, 10:0.5, 10:1, 10:2, 10:3, 10:4, 10:5, 10:6, 10:7, 10:8, 10:9, or 10:10). The flow rate of the mixture can be specifically set by those skilled in the art according to the circumstances; in this embodiment, the linear velocity of the mixture is 0.03 to 0.1 m / s, preferably 0.04 to 0.07 m / s.

[0102] In one embodiment, the carbon gas phase coating step is carried out in a fluidized bed; the carbon source gas introduced under a protective atmosphere is a mixture of the protective atmosphere gas and the carbon source gas introduced from the bottom of the fluidized bed; the volume ratio of the protective atmosphere gas to the carbon source gas in the mixture is 10:(0.1 to 10) (for example, it can be 10:01, 10:0.5, 10:1, 10:2, 10:3, 10:4, 10:5, 10:6, 10:7, 10:8, 10:9, or 10:10). The flow rate of the mixture can be specifically set by those skilled in the art according to the circumstances; in this embodiment, the linear velocity of the mixture is 0.03 to 0.1 m / s, preferably 0.04 to 0.07 m / s.

[0103] In one embodiment, the silicon source gas is selected from silanes and / or chlorosilanes.

[0104] In one embodiment, the carbon source gas is selected from one or more combinations of alkanes, alkenes, alkynes, and carbon oxides.

[0105] In one aspect of this application, a battery is provided, comprising: a bio-based spherical silicon-carbon anode material prepared by any of the above-described methods for preparing bio-based spherical silicon-carbon anode materials.

[0106] Example

[0107] Unless otherwise specified, the experimental methods used below are all conventional methods.

[0108] Unless otherwise specified, all materials and reagents used below are commercially available.

[0109] Unless otherwise specified, the black liquor used in the following examples and comparative examples is all from the black liquor produced by the alkaline papermaking process of Daqing Shengquan Group.

[0110] In the following examples and comparative examples, pH was measured using a Mettler FE28 benchtop pH meter, and Na content was measured using a Thermo Fisher iCAPPRO XP Duo inductively coupled plasma atomic emission spectrometer (ICP).

[0111] Bio-based spherical porous carbons of Examples 1 to 6 and Comparative Examples 1 to 6, as shown in Table 1, were prepared using the following methods.

[0112] Crosslinking agent A

[0113] A-1: Phenol

[0114] A-2: Formaldehyde

[0115] A-3: Hexamethylenetetramine

[0116] A-4: Paraformaldehyde

[0117] A-5: Resorcinol

[0118] Dispersant B

[0119] B-1: Sorbitan Oleate

[0120] B-2: White Oil

[0121] B-3: Polyvinyl alcohol

[0122] B-4: Polyvinylpyrrolidone

[0123] B-5: Gelatin

[0124] Example 1

[0125] In a high-pressure jacketed reactor, add 230 kg of papermaking black liquor (30% solids content, pH = 12, Na content 240,000 ppm), crosslinking agent (8 kg phenol, 2 kg formaldehyde, 10 kg hexamethylenetetramine), and dispersant (1 kg sorbitan oleate, 2 kg white oil). After stirring at room temperature for 2 hours, raise the reactor temperature to 180°C and stir slowly at this temperature for 24 hours. (Precursor synthesis steps)

[0126] The slurry is cooled to 120°C, then pressurized and conveyed to an activated fluidized bed heated to 110°C. It is then sprayed into the fluidized bed cavity through a two-fluid atomizing nozzle under nitrogen protection. After all the slurry is injected into the fluidized bed, it is kept at 110°C for 6 hours to dry the powder. The activated fluidized bed is then heated to 500°C at a rate of 8°C / min and kept at that temperature for 4 hours to dehydrate the powder. During both drying and dehydration, nitrogen is continuously purged through the bottom of the activated fluidized bed to clean the powder. (Drying and Dehydration Steps)

[0127] After dehydration, the activated fluidized bed is heated to 750°C at a rate of 2°C / min and maintained for 12 hours. Simultaneously, nitrogen gas is introduced into the bottom of the activated fluidized bed to perform alkali activation of the powder. (Alkali activation pore-forming step)

[0128] After alkali activation, the temperature was increased to 900℃ at a rate of 2℃ / min. A mixture of HCl and nitrogen gas (volume ratio of HCl to nitrogen 1.5:8.5) was introduced into the bottom of the activated fluidized bed and maintained for 4 hours to complete gas-phase deashing. After gas-phase deashing, the heating of the activated fluidized bed was turned off, allowing the temperature inside the activated fluidized bed to drop below 100℃, yielding the intermediate product, bio-based spherical porous carbon. (Gas-phase deashing step)

[0129] Bio-based spherical porous carbon is transported from an activated fluidized bed to a deposition fluidized bed via gas transport. The fluidized bed is heated under a nitrogen atmosphere. When the fluidized bed reaches 520°C, the temperature is maintained constant. A mixture of silane and nitrogen gas (3:13 volume ratio) is introduced from the bottom of the fluidized bed for silicon vapor deposition. After maintaining this temperature for 400 minutes, the silane introduction is stopped. (Silicon vapor deposition procedure)

[0130] The fluidized bed was heated to 600℃ under a nitrogen atmosphere and maintained at a constant temperature. A mixture of acetylene and nitrogen gas (volume ratio 3:13) was then introduced to perform carbon gas-phase coating. After maintaining this temperature for 360 minutes, the acetylene supply was stopped, and the fluidized bed heating was shut off. The fluidized bed was then cooled under a nitrogen atmosphere. When the fluidized bed temperature dropped below 100℃, the reactor was discharged, yielding spherical silicon-carbon anode material prepared from bio-based spherical porous carbon. (Carbon gas-phase coating step)

[0131] Compared to Example 1, the differences between the other examples and comparative examples for preparing bio-based spherical silicon-carbon anode materials lie only in the types, mass fractions, and reaction conditions of reagents used in the precursor synthesis steps shown in Table 1. Furthermore, since Comparative Examples 1-6 obtained bulk polymers rather than bio-based microspheres in the precursor synthesis step, they only performed the precursor synthesis step and did not proceed with subsequent steps. The preparation conditions for Examples 1-6 and Comparative Examples 1-6 are shown in Table 1.

[0132] Table 1. Process parameters for precursor synthesis steps

[0133]

[0134] Comparative Example 7 (Preparation of silicon-carbon anode material using coconut shell-based porous carbon as raw material)

[0135] Commercially available coconut shell-based porous carbon (parameters detailed in Tables 2 and 3) was fed into a fluidized bed for deposition. The fluidized bed was heated under a nitrogen atmosphere. When the temperature reached 520°C, it was maintained constant. A mixture of silane and nitrogen gas (volume ratio 3:13) was introduced from the bottom of the fluidized bed for silicon vapor deposition. After maintaining this temperature for 400 minutes, the introduction of silane was stopped. (Silicon vapor deposition procedure)

[0136] The fluidized bed was heated to 600℃ under a nitrogen atmosphere and maintained at a constant temperature. A mixture of acetylene and nitrogen gas (volume ratio 3:13) was then introduced to perform carbon gas-phase coating. After maintaining this temperature for 360 minutes, the acetylene supply was stopped, and the fluidized bed heating was shut off. The fluidized bed was then cooled under a nitrogen atmosphere. When the fluidized bed temperature dropped below 100℃, the reactor was discharged, yielding spherical silicon-carbon anode material prepared from coconut shell-based porous carbon. (Carbon gas-phase coating step)

[0137] Comparative Example 8 (Preparation of silicon-carbon anode material using pitch-based porous carbon as raw material)

[0138] Commercially available pitch-based porous carbon (parameters detailed in Tables 2 and 3) was fed into a deposition fluidized bed. The fluidized bed was heated under a nitrogen atmosphere. When the temperature reached 520°C, it was maintained constant. A mixture of silane and nitrogen gas (volume ratio 3:13) was introduced from the bottom of the fluidized bed to perform silicon vapor deposition. After maintaining this temperature for 400 minutes, the introduction of silane was stopped. (Silicon vapor deposition procedure)

[0139] The fluidized bed was heated to 600℃ under a nitrogen atmosphere and maintained at a constant temperature. A mixture of acetylene and nitrogen gas (volume ratio 3:13) was then introduced to perform carbon gas-phase coating. After maintaining this temperature for 360 minutes, the acetylene supply was stopped, and the fluidized bed heating was shut off. The fluidized bed was then cooled under a nitrogen atmosphere. When the fluidized bed temperature dropped below 100℃, the reactor was discharged, yielding spherical silicon-carbon anode material prepared from pitch-based porous carbon. (Carbon gas-phase coating step)

[0140] Test case

[0141] Porous carbon particle size detection and electron micrograph

[0142] In the preparation processes of Examples 1-6 above, the particle size of the intermediate bio-based spherical porous carbon was measured, and the particle size of the commercially available coconut shell-based porous carbon of Comparative Example 7 and the commercially available pitch-based porous carbon of Comparative Example 8 was also measured. The particle size was determined using a Malvern Mastersizer 3000E laser particle size analyzer, and the results are detailed in Table 2. Furthermore, the morphology of the intermediate products obtained in Examples 1-6 and Comparative Examples 1-6, as well as the commercially available coconut shell-based porous carbon of Example 7 and the commercially available pitch-based porous carbon of Comparative Example 8, was analyzed using field emission scanning electron microscopy. The results are detailed in Table 2. Figures 1 to 14 Examples 1-6 are electron micrographs of the intermediate porous carbon, and Comparative Examples 1-6 are electron micrographs of the product (bulk polymer) obtained from the precursor synthesis step.

[0143] Table 2 Porous carbon particle size

[0144]

[0145] Through Table 1, Table 2 and Figures 1-12 It can be seen that in the precursor synthesis steps, crosslinking agents, dispersants, reaction temperature, and time play important roles in the reaction results.

[0146] For Examples 1-6, please refer to Table 1. Figures 1-6 It can be seen that it can synthesize bio-based microspheres with suitable particle size (without the need for further crushing and grading) and a relatively perfect spherical shape.

[0147] For Comparative Examples 1 to 6, please refer to Table 1. Figures 7-12 Comparative Example 1 did not use any crosslinking agent or dispersant and polymerization was carried out directly. Comparative Examples 2 and 3 used only one of the crosslinking agent or dispersant. The lack of either crosslinking agent or dispersant caused the formed spherical precursors to stick together and could not be dispersed as single particles. Without additional pulverization, they could not be used normally. Comparative Examples 4 and 5 changed the polymerization temperature conditions. Too low a reaction temperature would prevent polymerization from taking place, while too high a reaction temperature would cause the polymerization rate to be too fast, resulting in blocky resin. Comparative Example 6 used black liquor with a higher solids concentration. Since the liquid part of papermaking black liquor acts as a partial solvent, the high solids content of the papermaking black liquor in Comparative Example 6 resulted in too little actual solvent, which prevented the synthesized material from being uniformly dispersed in the solvent and polymerized into spherical shapes. The polymer was a blocky polymer.

[0148] Porous carbon, anode materials, and performance testing of the batteries prepared from them

[0149] The applicant tested the porous carbon and battery anode materials of Example 4, Comparative Example 7, and Comparative Example 8. The test results are detailed in Table 3 below.

[0150] To test the performance of the negative electrode material, button cells were fabricated and their performance was tested. The button cell fabrication method was as follows: a slurry was prepared by mixing silicon-carbon negative electrode material (SP, CMC, LA136D) in a ratio of 75:10:2.5:12.5 (SP (Supercarbon) is a conductive agent, CMC is carboxymethyl cellulose (CMC 2200), and LA136D is an aqueous silicon-carbon negative electrode binder; all materials are commonly used in button cell manufacturing). The material was homogenized in an ITI-300SS vacuum mixer and degassing machine, and then coated onto 9μm copper foil with a coating thickness of 120μm. After drying the coated foil, it was cut into [size not specified]. The CR2032 battery uses circular electrodes, lithium plates, a ceramic PVDF separator, and LB-137 to assemble the cells. Lithium plate specifications: Membrane specifications: base membrane 9μm, PVDF coating 3μm, ceramic layer 1μm; electrolyte specifications: 1M LiPF6 in DMC:EC:EMC=1:1:1 Vol% with 5% FEC, 1% VC; dosage: 60μL.

[0151] Among them, the pore volume, specific surface area, and average pore diameter of porous carbon were detected by the ASAP2460 multi-station extended fully automatic specific surface area and porosity analyzer of Micromeritics; the collapse angle, difference angle, dispersity, and flowability index of porous carbon were tested by the Tanggula Comprehensive Testing Powder Analyzer (PT-Pro); the single particle strength of silicon-carbon anode material was determined by the Shimadzu MCT-210 micro compression tester of Japan; and the carbon content of anode material was determined by the carbon-sulfur analyzer (3500) of Steel Research Institute.

[0152] Table 3: Test Results of Porous Carbon and Battery Anode Materials

[0153]

[0154] Comparative Examples 7 and 8 both used blocky porous carbon, whose pore volume and particle size distribution were similar to the spherical porous carbon in Example 4. The difference between the two lies in the particle shape. Therefore, the influence of particle flowability on silicon deposition effect can be verified. Compared with the porous carbon of Comparative Examples 7 and 8 in the prior art, the porous carbon prepared in Example 4 of this application has significantly higher flowability than the porous carbon of Comparative Examples 7 and 8, mainly reflected in a larger collapse angle, a larger difference angle, and a higher statistical flowability index. Therefore, during silicon vapor deposition in a fluidized bed, the fluidization state of the porous carbon is... The porous carbon in Example 4 of this application is significantly stronger than that in Comparative Examples 7 and 8, exhibiting better gas-solid contact and better silicon deposition under the same conditions. While the porous carbon in Example 4 has a similar pore volume to that in Comparative Examples 7 and 8, it has a smaller average pore size. Under the same conditions, after silicon deposition and carbon coating, the resulting sample powder has a lower resistivity, indicating less silicon deposition on the outer surface of the porous carbon compared to Comparative Examples 7 and 8, resulting in lower powder resistance. Furthermore, the higher 1.5V reversible capacity indicates that the porous carbon has a higher adsorption efficiency for silane during the silicon deposition stage. In the single-particle strength test, the silicon-carbon anode prepared in Example 4 has an average deformation pressure Cs of 922.43 MPa, significantly higher than the average Cs of Comparative Examples 7 and 8. The silicon-carbon anode material prepared from the bio-based spherical porous carbon of this application has higher single-particle strength and higher binding force in terms of silicon expansion after lithium intercalation, effectively mitigating the decrease in battery cycle life caused by silicon expansion. In addition, the silicon-carbon anode materials prepared in Comparative Examples 7 and 8 have excessively high powder resistivity, making it difficult to obtain qualified battery cell products. The silicon-carbon anode material prepared by the technical solution of this application (such as Example 4) can significantly reduce the powder resistivity.

Claims

1. A method for preparing a bio-based spherical porous carbon, comprising: a precursor synthesis step of adding a cross-linking agent and a dispersing agent to a papermaking black liquor to prepare a slurry containing bio-based microspheres by a sol-gel method, the papermaking black liquor being a papermaking black liquor produced by alkaline papermaking; a drying and dewatering step of drying and dewatering the slurry under a protective atmosphere to obtain dried and dewatered bio-based microspheres; an alkali activation pore-forming step of alkali activating the dried and dewatered bio-based microspheres using an alkali pore-forming agent rich in the bio-based microspheres under a protective atmosphere and an activation temperature; a gas-phase deashing step of adding an acidic gas to the bio-based microspheres under a protective atmosphere to generate a salt and vaporize and remove the salt and impurities to obtain the bio-based spherical porous carbon; wherein the cross-linking agent comprises any one or two or more of phenol, resorcinol, formaldehyde, and paraformaldehyde, and hexamethylenetetramine; the solid content of the papermaking black liquor is 30% to 60%; the cross-linking agent is added in an amount of 1% to 20% of the mass of the papermaking black liquor; the dispersing agent is selected from one or a combination of two or more of gelatin, polyvinyl alcohol, polyethylene glycol, white oil, polyvinylpyrrolidone, sodium polyacrylate, and sorbitan oleate; the precursor synthesis step is performed in a closed reactor; the heating temperature is 170℃ to 190℃; and the heating time is ≥ 18 h. 2.The method according to claim 1, wherein the pH of the papermaking black liquor is ≥ 11.0; and / or the Na content of the papermaking black liquor is 200000 ppm to 400000 ppm. 3.The method according to claim 2, wherein the pH of the papermaking black liquor is ≥ 12.0; and / or the Na content of the papermaking black liquor is 230000 ppm to 250000 ppm. 4.The method according to claim 1, wherein the dispersing agent is added in an amount of 0.1% to 20% of the mass of the papermaking black liquor. 5.The method according to claim 1, wherein the heating temperature is 175℃ to 185℃; and / or the heating time is 22 h to 24 h. 6.The method according to claim 1, wherein the drying and dewatering step is performed in an activated fluidized bed; the drying and dewatering step comprises a drying sub-step and a dewatering sub-step performed after the drying sub-step; wherein in the drying sub-step, the slurry is sprayed into the activated fluidized bed through a two-fluid atomizing nozzle under a protective atmosphere; the drying temperature is 100℃ to 150℃; and the drying time after the slurry enters the activated fluidized bed is 0.5 h to 6 h; the dewatering temperature of the dewatering sub-step is 200℃ to 800℃; and the dewatering time is 0.5 h to 6 h. 7.The method according to claim 6, wherein the drying temperature is 110℃ to 120℃; and / or the dewatering temperature is 300℃ to 600℃. 8.The method according to claim 1, wherein the alkali activation pore-forming step is performed in an activated fluidized bed; the activation temperature is 600℃ to 1100℃; the activation time is 0.5 h to 24 h. 9.The method according to claim 8, wherein the activation temperature is 750℃ to 950℃.

10. The preparation method of claim 8, wherein, in the alkali activation pore-forming step, the inert gas is continuously fed from the bottom of the gas-activated fluidized bed to form the protective atmosphere.

11. The preparation method of claim 1, wherein, the gas-phase deliming step is performed in an activated fluidized bed; the gas-phase deliming temperature is 400-1100°C; the deliming time is 0.5-6h.

12. The preparation method of claim 11, wherein, the gas-phase deliming temperature is 650-950°C.

13. The preparation method of claim 1, wherein, the acidic gas is derived from a halogen element and / or a halogen compound; wherein, the halogen element is selected from any one or a combination of two or more of fluorine, chlorine, bromine, and iodine; the halogen compound is selected from any one or a combination of two or more of hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, chlorofluoride, chloroiodide, bromoiodide, chlorobromide, and an acidic precursor compound; wherein the acidic precursor compound can be decomposed to generate at least one of hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, chlorofluoride, chloroiodide, bromoiodide, and chlorobromide upon heating in the alkali activation pore-forming step.

14. The preparation method of claim 13, wherein, the halogen element is chlorine; the halogen compound is hydrogen chloride.

15. A preparation method of a bio-based spherical silicon-carbon negative electrode material, which uses the bio-based spherical porous carbon prepared by any one of the preparation methods of the bio-based spherical porous carbon of claims 1-14, comprising: a silicon vapor deposition step: feeding a silicon source gas under a protective atmosphere to deposit silicon on the bio-based spherical porous carbon to obtain nano-silicon-deposited bio-based spherical porous carbon; a carbon vapor coating step: feeding a carbon source gas under a protective atmosphere to coat the nano-silicon-deposited bio-based spherical porous carbon with carbon to obtain the bio-based spherical silicon-carbon negative electrode material.

16. The preparation method of claim 15, wherein, in the silicon vapor deposition step, the silicon vapor deposition temperature is 450-650°C; and / or, in the carbon vapor coating step, the carbon coating temperature is 450-700°C.

17. The preparation method of claim 16, wherein, the silicon vapor deposition temperature is 500-550°C; and / or, the carbon coating temperature is 500-650°C.

18. The preparation method of claim 16, wherein, the silicon vapor deposition step is performed in a deposition fluidized bed; feeding the silicon source gas under a protective atmosphere is: feeding a mixed gas of the protective atmosphere gas and the silicon source gas from the bottom of the deposition fluidized bed; the volume ratio of the protective atmosphere gas to the silicon source gas in the mixed gas is 10: (0.1-10).

19. The preparation method of claim 16, wherein, the carbon vapor coating step is performed in a deposition fluidized bed; feeding the carbon source gas under a protective atmosphere is: feeding a mixed gas of the protective atmosphere gas and the carbon source gas from the bottom of the deposition fluidized bed; the volume ratio of the protective atmosphere gas to the carbon source gas in the mixed gas is 10: (0.1-10).

20. The production method according to claim 15, wherein the silicon source gas is selected from the group consisting of silane and / or chlorosilane; and / or, the carbon source gas is selected from the group consisting of one or a combination of two or more of alkane, alkene, alkyne, carbon oxide.

21. A battery comprising: the bio-based spherical silicon-carbon anode material produced by the production method according to any one of claims 15 to 20.

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