Metal compound soft and hard carbon composite material as well as preparation method and application thereof

Abstract

The invention relates to the field of ion batteries, in particular to a metal compound soft and hard carbon composite material and a preparation method and application thereof. A polyphenol hydroxyl structure in a polyphenol substance generates a strong chelation effect and a multivalent effect, a complex formed by the polyphenol substance and metal ions shows excellent stability, after high-temperature calcination, the surface layer is coated with soft carbon and a hard carbon template to complete heteroatom doping, and an intermediate complex is fired into a target compound. A hard carbon-metal compound-soft carbon three-layer coating structure relieves volume expansion and provides good electrochemical performance, and soft carbon coating reduces contact between hard carbon and electrolyte and improves the first efficiency of the battery. Biomass waste is adopted to be suitable for acid treatment and purification, the consistency of hard carbon is greatly improved, a uniform cellulose hard carbon template is prepared, meanwhile, polyphenol substances and cellulose have strong non-power-supply interaction, combination of the polyphenol substances and the cellulose is firmer through a cross-linking agent, formation of a complex on the cellulose template is facilitated, and the structural stability is enhanced.

Description

Technical Field

[0001] This invention relates to the field of ion batteries, and more particularly to a metal compound soft and hard carbon composite material, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy vehicles and the large-scale energy storage market, the development of low-cost, high-performance, and highly safe lithium-ion (LIB) and sodium-ion (SIB) batteries has become a research hotspot. As a core component of the battery, the performance of the anode material is crucial.

[0003] Hard carbon materials are considered to be highly promising SIB anode materials due to their abundant defects, widened interlayer spacing, and excellent rate performance, and can also be used as fast-charging anodes for LIBs. However, hard carbon materials face three major technical challenges: (1) the large specific surface area and abundant defects in the SEI film consume a large amount of active lithium / sodium, resulting in low initial coulombic efficiency; (2) poor batch consistency, leading to large performance fluctuations; and (3) volume expansion, affecting cycle stability. Currently, strategies to improve the performance of hard carbon include element doping, structural design, and surface coating. For example, using phenolic resin and other synthetic precursors can improve consistency, but the cost is high; using soft carbon coating such as pitch can improve ICE, but it cannot solve the consistency problem of biomass raw materials themselves. In addition, the acid treatment waste liquid in the existing preparation methods also lacks a simple and effective recycling and treatment scheme, posing environmental hazards.

[0004] Therefore, developing a method for preparing anode materials that has low raw material costs, environmentally friendly processes, excellent product performance, and high batch stability has significant practical and commercial value. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of poor batch consistency of biomass waste, severe compound volume expansion, and low initial efficiency of hard carbon in existing technologies. A homogeneous cellulose template is prepared through low-cost purification, and then a primary coating is achieved through non-electrical interactions of polyphenols and enhanced binding with a cross-linking agent. Subsequently, a three-layer structure of hard carbon-metal compound-soft carbon coating is prepared by high-temperature calcination with soft carbon materials and heteroatoms. This structure achieves excellent electrochemical performance when applied to sodium or lithium batteries.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of this invention is to provide a method for preparing a metal compound soft-hard carbon composite material, comprising the steps of:

[0008] S1. After crushing and acid soaking the biomass waste, the cellulose material is obtained by filtration and purification.

[0009] S2. Disperse the cellulose material in a solution, add the crosslinking agent, polyphenolic substance and metal salt in sequence, stir and then perform hydrothermal treatment. After the reaction is completed, collect and wash the intermediate.

[0010] S3. The intermediate is mixed with asphalt and then subjected to ball milling, drying, high-temperature pyrolysis and cooling treatments, followed by grinding and sieving to obtain the metal compound soft and hard carbon composite anode material.

[0011] Preferably, in step S1, the biomass waste includes at least one of the following: wood waste, straw, wheat straw, rice husk, reed, and hardwood.

[0012] Preferably, in step S1, the reagent used for the acid soaking treatment is a mixed soaking solution of organic acid, hydrogen peroxide and solvent; wherein the solvent includes at least one of water and alcohol.

[0013] Preferably, in step S2, the polyphenolic substance includes at least one of tannic acid, gallic acid, proanthocyanidins, caffeic acid, epigallocatechin gallate, and quercetin; the crosslinking agent includes at least one of citric acid, epichlorohydrin, and biological enzymes; and the metal ion in the metal salt includes at least one of iron ions, copper ions, and aluminum ions.

[0014] Preferably, in step S2, the hydrothermal treatment temperature is 90-150℃ and the time is 10-30h.

[0015] Preferably, in step S3, the mass ratio of the intermediate to the asphalt is 1:(0.1-0.5).

[0016] Preferably, in step S3, the high-temperature pyrolysis treatment includes: heating to 800-1400℃ at a heating rate of 1-5℃ / min and holding at that temperature for 1-3 hours.

[0017] Preferably, the high-temperature pyrolysis treatment includes: heating the intermediate with selenium powder, sulfur powder or melamine.

[0018] A second aspect of the present invention is to provide a metal compound soft and hard carbon composite material, which is prepared by the above-described preparation method.

[0019] The third aspect of the present invention is to provide an application of the metal compound soft and hard carbon composite material prepared by the above preparation method in an alkali metal ion battery. The preparation steps include: mixing the metal compound soft and hard carbon composite material with acetylene black and polyvinylidene fluoride and dissolving it in N-methylpyrrolidone, grinding it evenly and coating it on a copper foil current collector, drying and cooling to obtain a negative electrode sheet; assembling the negative electrode sheet with a positive electrode sheet, a separator, an electrolyte and a battery case to obtain an alkali metal ion battery.

[0020] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0021] (1) The polyphenol hydroxyl structure in the polyphenolic substances in this invention produces a strong chelation effect and a multivalent effect. The complex formed with metal ions exhibits excellent stability. After high-temperature calcination, the surface is coated with soft carbon and hard carbon template to complete heteroatom doping. The intermediate complex is calcined to form the target compound. The three-layer coating structure of hard carbon-metal compound-soft carbon alleviates volume expansion and provides good electrochemical performance. The coating of soft carbon reduces the contact between hard carbon and electrolyte and improves the first efficiency of the battery.

[0022] (2) This invention utilizes suitable acid treatment to purify biomass waste, significantly improving the uniformity of hard carbon and preparing a uniform cellulose hard carbon template. Simultaneously, polyphenols exhibit strong non-electrical interactions with cellulose, which are further strengthened by a cross-linking agent, facilitating the formation of complexes on the cellulose template and enhancing structural stability. The soaked liquid can be collected and recycled through simple distillation or cooling crystallization. The dissolved lignin and hemicellulose can be recycled for downstream products. The treatment method is simple, safe, and environmentally friendly. Attached Figure Description

[0023] Figure 1 This is an electron microscope image of the metal compound soft and hard carbon composite material in Example 3.

[0024] Figure 2 This is a cycle performance diagram of the battery in Example 3. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0028] Example 1

[0029] This embodiment provides a method for preparing a metal compound soft and hard carbon composite material and its application.

[0030] 100g of dried straw was crushed and placed in a 2:1 mixture of acetic acid and hydrogen peroxide. After stirring evenly, the mixture was left to stand at room temperature for 24 hours. Then, it was washed with deionized water until neutral, dried, and the purified cellulose material was collected. 10g of the dried cellulose material was dispersed in a 1:6 mixture of alcohol and water and ultrasonically stirred evenly. 2g of tannic acid (a polyphenol), 0.05g of citric acid (a crosslinking agent), and 20mL of 0.1mol / L ferric acetate solution (a metal salt) were added sequentially, and the mixture was stirred for 6 hours. The mixture was transferred to a 200mL hydrothermal reactor lined with polytetrafluoroethylene and reacted at 120℃ for 10 hours. After cooling, the mixture was filtered and washed with ethanol and water, then vacuum dried at 80℃ to obtain an intermediate. The intermediate was placed in a ball mill with 0.5g of pitch (a soft carbon source) and ball-milled at 300r / min for 2 hours to ensure uniform mixing. The mixture was placed in a tube furnace and heated to 900°C at a rate of 5°C / min under an argon atmosphere and held for 2 hours. After natural cooling to room temperature, the carbonized product was ground into a fine powder to obtain the final three-layer metal compound soft-hard carbon composite material. The above material was mixed with acetylene black and PVDF in an NMP solution at a mass ratio of 7:2:1, ground evenly, and then coated onto a copper foil current collector. After drying and cooling, a negative electrode sheet was prepared. This negative electrode sheet was then assembled with a positive electrode sheet, separator, electrolyte, and battery casing made from commercial positive electrode materials to form a button cell, and its electrical performance was tested.

[0031] Example 2

[0032] This embodiment provides another method for preparing soft and hard carbon composite materials made of metal compounds and their applications.

[0033] 100g of dried straw was crushed and placed in a 2:1 mixture of acetic acid and hydrogen peroxide. After stirring evenly, it was left to stand at room temperature for 24 hours. Then, it was washed with deionized water until neutral, dried, and the purified cellulose material was collected. 10g of the dried cellulose material was dispersed in a 1:6 mixture of alcohol and water and ultrasonically stirred evenly. 2g of tannic acid (a polyphenol), 0.05g of citric acid (a crosslinking agent), and 20mL of 0.1mol / L copper acetate solution (a metal salt) were added sequentially, and the mixture was stirred for 6 hours. The mixture was transferred to a 200mL hydrothermal reactor lined with polytetrafluoroethylene and reacted at 120℃ for 10 hours. After cooling, it was filtered and washed with ethanol and water, then vacuum dried at 80℃ to obtain an intermediate. The intermediate was placed in a ball mill with 0.5g of pitch (a soft carbon source) and ball-milled at 300r / min for 2 hours to ensure uniform mixing. The mixture was placed in a tube furnace and heated to 900°C at a rate of 5°C / min under an argon atmosphere and held for 2 hours. After natural cooling to room temperature, the carbonized product was ground into a fine powder to obtain the final three-layer metal compound soft-hard carbon composite material. The above material was mixed with acetylene black and PVDF in an NMP solution at a mass ratio of 7:2:1, ground evenly, and then coated onto a copper foil current collector. After drying and cooling, a negative electrode sheet was prepared. This negative electrode sheet was then assembled with a positive electrode sheet, separator, electrolyte, and battery casing made from commercial positive electrode materials to form a button cell, and its electrical performance was tested.

[0034] Example 3

[0035] This embodiment provides another method for preparing soft and hard carbon composite materials made of metal compounds and their applications.

[0036] 100g of dried straw was crushed and placed in a 2:1 mixture of acetic acid and hydrogen peroxide. After stirring evenly, it was left to stand at room temperature for 24 hours. Then, it was washed with deionized water until neutral, dried, and the purified cellulose material was collected. 10g of the dried cellulose material was dispersed in a 1:6 mixture of alcohol and water and ultrasonically stirred evenly. 2g of tannic acid (a polyphenol), 0.05g of citric acid (a crosslinking agent), and 20mL of 0.1mol / L ferric acetate (a metal salt) were added sequentially, and the mixture was stirred for 6 hours. The mixture was transferred to a 200mL hydrothermal reactor lined with polytetrafluoroethylene and reacted at 120℃ for 10 hours. After cooling, it was filtered and washed with ethanol and water, then vacuum dried at 80℃ to obtain the precursor intermediate. The intermediate was placed in a ball mill with 0.5g of pitch (a soft carbon source) and ball-milled at 300r / min for 2 hours to ensure uniform mixing. The mixture was combined with selenium powder and placed in a tube furnace. Under an argon atmosphere, the temperature was increased to 900°C at a rate of 5°C / min and held for 2 hours. After natural cooling to room temperature, the carbonized product was ground into a fine powder to obtain the final three-layer metal compound soft-hard carbon composite material. The above material was mixed with acetylene black and PVDF in an NMP solution at a mass ratio of 7:2:1, ground evenly, and then coated onto a copper foil current collector. After drying and cooling, a negative electrode sheet was prepared. This negative electrode sheet was then assembled with a positive electrode sheet, separator, electrolyte, and battery casing made from commercial positive electrode materials to form a button cell, and its electrical performance was tested.

[0037] Example 4

[0038] This embodiment provides another method for preparing soft and hard carbon composite materials made of metal compounds and their applications.

[0039] 100g of dried straw was crushed and placed in a 2:1 mixture of acetic acid and hydrogen peroxide. After stirring evenly, it was left to stand at room temperature for 24 hours. Then, it was washed with deionized water until neutral, dried, and the purified cellulose material was collected. 10g of the dried cellulose material was dispersed in a 1:6 mixture of alcohol and water and ultrasonically stirred evenly. 2g of tannic acid (a polyphenol), 0.05g of citric acid (a crosslinking agent), and 20mL of 0.1mol / L ferric acetate solution (a metal salt) were added sequentially, and the mixture was stirred for 6 hours. The mixture was transferred to a 200mL hydrothermal reactor lined with polytetrafluoroethylene and reacted at 120℃ for 10 hours. After cooling, it was filtered and washed with ethanol and water, then vacuum dried at 80℃ to obtain the precursor intermediate. The intermediate was placed in a ball mill with 0.5g of pitch (a soft carbon source) and ball-milled at 300r / min for 2 hours to ensure uniform mixing. The mixture was combined with sulfur powder and placed in a tube furnace. Under an argon atmosphere, the temperature was increased to 900°C at a rate of 5°C / min and held for 2 hours. After natural cooling to room temperature, the carbonized product was ground into a fine powder to obtain the final three-layer metal compound soft-hard carbon composite material. The above material was mixed with acetylene black and PVDF in an NMP solution at a mass ratio of 7:2:1, ground evenly, and then coated onto a copper foil current collector. After drying and cooling, a negative electrode sheet was prepared. This negative electrode sheet was then assembled with a positive electrode sheet, separator, electrolyte, and battery casing made from commercial positive electrode materials to form a button cell, and its electrical performance was tested.

[0040] Example 5

[0041] This embodiment provides another method for preparing soft and hard carbon composite materials made of metal compounds and their applications.

[0042] 100g of dried straw was crushed and placed in a 2:1 mixture of acetic acid and hydrogen peroxide. After stirring evenly, it was left to stand at room temperature for 24 hours. Then, it was washed with deionized water until neutral, dried, and the purified cellulose material was collected. 10g of the dried cellulose material was dispersed in a 1:6 mixture of alcohol and water and ultrasonically stirred evenly. 2g of tannic acid (a polyphenol), 0.05g of citric acid (a crosslinking agent), and 20mL of 0.1mol / L copper acetate solution (a metal salt) were added sequentially, and the mixture was stirred for 6 hours. The mixture was transferred to a 200mL hydrothermal reactor lined with polytetrafluoroethylene and reacted at 120℃ for 10 hours. After cooling, it was filtered and washed with ethanol and water, then vacuum dried at 80℃ to obtain the precursor intermediate. The intermediate was placed in a ball mill with 0.5g of pitch (a soft carbon source) and ball-milled at 300r / min for 2 hours to ensure uniform mixing. The mixture was combined with sulfur powder and placed in a tube furnace. Under an argon atmosphere, the temperature was increased to 900°C at a rate of 5°C / min and held for 2 hours. After natural cooling to room temperature, the carbonized product was ground into a fine powder to obtain the final three-layer metal compound soft-hard carbon composite material. The above material was mixed with acetylene black and PVDF in an NMP solution at a mass ratio of 7:2:1, ground evenly, and then coated onto a copper foil current collector. After drying and cooling, a negative electrode sheet was prepared. This negative electrode sheet was then assembled with a positive electrode sheet, separator, electrolyte, and battery casing made from commercial positive electrode materials to form a button cell, and its electrical performance was tested.

[0043] Comparative Example 1

[0044] This comparative example provides a negative electrode material.

[0045] In a prepared alcohol-water mixture, 2g of tannic acid (a polyphenol), 0.05g of citric acid (a crosslinking agent), and 20mL of 0.1mol / L ferric acetate solution (a metal salt) were added sequentially, and the mixture was stirred for 6 hours. The mixture was then transferred to a 200mL hydrothermal reactor lined with polytetrafluoroethylene and reacted at 120℃ for 10 hours. After cooling, the mixture was filtered and washed with ethanol and water, then vacuum dried at 80℃ to obtain a precursor intermediate. This intermediate was then placed in a ball mill with 0.5g of pitch (a soft carbon source) and ball-milled at 300r / min for 2 hours to ensure uniform mixing. The mixture was then mixed with selenium powder and placed in a tube furnace. Under an argon atmosphere, the temperature was increased to 900℃ at a rate of 5℃ / min and held for 2 hours. After naturally cooling to room temperature, the carbonized product was ground into a fine powder to obtain the final core-shell structured metal compound carbon composite material. The above materials were mixed with acetylene black and PVDF in an NMP solution at a mass ratio of 7:2:1, ground evenly, coated onto a copper foil current collector, and dried and cooled to form a negative electrode sheet. Then, it was assembled with a positive electrode sheet made of commercial positive electrode materials, a separator, an electrolyte, a battery casing, etc. to form a button battery, and the electrical performance was tested.

[0046] Comparative Example 2

[0047] This comparative example provides another negative electrode material.

[0048] 100g of dried straw was crushed and placed in a 2:1 mixture of acetic acid and hydrogen peroxide. After stirring evenly, the mixture was left to stand at room temperature for 24 hours. The material was then washed with deionized water until neutral, dried, and the purified cellulose material was collected. 10g of the dried material was dispersed in a 1:6 mixture of alcohol and water and ultrasonically stirred evenly. 2g of tannic acid (a polyphenol), 0.05g of citric acid (a crosslinking agent), and 20mL of 0.1mol / L ferric acetate solution (a metal salt) were added sequentially, and the mixture was stirred for 6 hours. The mixture was transferred to a 200mL hydrothermal reactor lined with polytetrafluoroethylene and reacted at 120℃ for 10 hours. After cooling, the mixture was filtered and washed with ethanol and water, then vacuum dried at 80℃ to obtain the precursor intermediate. The mixture was then mixed with selenium powder and placed in a tube furnace. Under an argon atmosphere, the temperature was increased to 900℃ at a rate of 5℃ / min and held for 2 hours. After naturally cooling to room temperature, the carbonized product was ground into a fine powder to obtain the final metal compound carbon composite material. The above materials were mixed with acetylene black and PVDF in an NMP solution at a mass ratio of 7:2:1, ground evenly, coated onto a copper foil current collector, and dried and cooled to form a negative electrode sheet. Then, it was assembled with a positive electrode sheet made of commercial positive electrode materials, a separator, an electrolyte, a battery casing, etc. to form a button battery, and the electrical performance was tested.

[0049] Comparative Example 3

[0050] This comparative example provides another negative electrode material.

[0051] 100g of dried straw was crushed and placed in a 2:1 mixture of acetic acid and hydrogen peroxide. After stirring evenly, the mixture was left to stand at room temperature for 24 hours. The straw was then washed with deionized water until neutral, and the purified cellulose material was collected after drying. The cellulose material was placed in a tube furnace and heated to 900℃ at a rate of 5℃ / min under an argon atmosphere and held for 2 hours. After naturally cooling to room temperature, the carbonized product was ground into a fine powder to obtain hard carbon material. This material was mixed with acetylene black and PVDF in a 7:2:1 mass ratio in an NMP solution, ground evenly, and coated onto a copper foil current collector. After drying and cooling, a negative electrode sheet was prepared. This negative electrode sheet was then assembled with a positive electrode sheet, separator, electrolyte, and battery casing made from commercial positive electrode materials to form a button cell, and its electrical performance was tested.

[0052] Detection Examples

[0053] The performance of the batteries in Examples 1-5 and Comparative Examples 1-3 was tested respectively, and the results are shown in Table 1.

[0054] Table 1

[0055]

[0056] As shown in Table 1, the HC@FeSe2@C prepared in Example 3 exhibits the best overall electrochemical performance as a sodium-ion battery anode material, with an initial efficiency of 91.3%, a reversible capacity of 452.7 mAh / g, and excellent cycle performance. Figure 2 As shown, the capacity remained at 411.8 mAh / g after 200 cycles. The electron micrograph of the material in Example 3 is shown below. Figure 1 As shown, selenides grow uniformly on the surface of a linear cellulose template, while the oxide surface is coated with a layer of soft carbon, forming a three-layer structure of hard carbon-metal compound-soft carbon from the inside out. The addition of metal compounds to this three-layer metal compound carbon composite material significantly improves the capacity. The presence of the hard carbon template and the outer soft carbon coating enhances the stability of the metal oxide and mitigates volume expansion, resulting in good cycling performance. Simultaneously, the small specific surface area of ​​the outer soft carbon coating reduces the consumption of metal ions during SEI film formation, improving the first coulombic efficiency.

[0057] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a metal compound soft-hard carbon composite material, characterized in that the steps include... include: S1. After crushing and acid soaking the biomass waste, the cellulose material is obtained by filtration and purification. S2. Disperse the cellulose material in a solution, add the crosslinking agent, polyphenolic substance and metal salt in sequence, stir and then perform hydrothermal treatment. After the reaction is completed, collect and wash the intermediate. S3. The intermediate is mixed with asphalt and then subjected to ball milling, drying, high-temperature pyrolysis and cooling treatments, followed by grinding and sieving to obtain the metal compound soft and hard carbon composite anode material.

2. The preparation method according to claim 1, characterized in that, In step S1, the biomass waste includes at least one of the following: wood waste, straw, wheat straw, rice husks, reeds, and hardwood.

3. The preparation method according to claim 1, characterized in that, In step S1, the reagent used for the acid soaking treatment is a mixed soaking solution of organic acid, hydrogen peroxide and solvent; wherein the solvent includes at least one of water and alcohol.

4. The preparation method according to claim 1, characterized in that, In step S2, the polyphenolic substances include at least one of tannic acid, gallic acid, proanthocyanidins, caffeic acid, epigallocatechin gallate, and quercetin; the crosslinking agent includes at least one of citric acid, epichlorohydrin, and biological enzymes; and the metal ions in the metal salt include at least one of iron ions, copper ions, and aluminum ions.

5. The preparation method according to claim 1, characterized in that, In step S2, the hydrothermal treatment temperature is 90-150℃ and the time is 10-30h.

6. The preparation method according to claim 1, characterized in that, In step S3, the mass ratio of the intermediate to the asphalt is 1:(0.1-0.5).

7. The preparation method according to claim 1, characterized in that, In step S3, the high-temperature pyrolysis treatment includes: heating to 800-1400℃ at a heating rate of 1-5℃ / min and holding at that temperature for 1-3 hours.

8. The preparation method according to claim 1, characterized in that, The high-temperature pyrolysis treatment includes heating the intermediate with selenium powder, sulfur powder, or melamine.

9. A metal compound soft-hard carbon composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of a metal compound soft-hard carbon composite material prepared by the preparation method according to any one of claims 1-8 in an alkali metal ion battery, characterized in that, The preparation steps include: mixing the metal compound soft and hard carbon composite material with acetylene black and polyvinylidene fluoride and dissolving it in N-methylpyrrolidone, grinding it evenly and coating it on a copper foil current collector, drying and cooling to obtain a negative electrode sheet; assembling the negative electrode sheet with a positive electrode sheet, a separator, an electrolyte and a battery case to obtain an alkali metal ion battery.

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