A power type sodium ion negative electrode material for energy storage, a battery, a preparation method and an application

Abstract

This invention belongs to the field of sodium-ion battery technology, specifically relating to a power-type sodium-ion anode material for energy storage, a battery, its preparation method, and its application. The raw materials for preparing the power-type sodium-ion battery anode material for energy storage provided by this invention are organic carbon sources, black phosphorus, and titanium sources, wherein the organic carbon sources include biochemical sludge, tar residue, and acidified plant tissue. After two heat treatments, the resulting anode material exhibits high specific capacity, good rate performance, and good cycle stability, and can be used to manufacture power-type sodium-ion batteries for energy storage.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, specifically relating to a power-type sodium-ion anode material for energy storage, a battery, its preparation method, and its application. Background Technology

[0002] Large-scale energy storage is key to realizing the practical application of renewable energy. Lithium-ion batteries, as one of the most successful rechargeable batteries in the energy storage field, have been widely used in electronics, electric vehicles, and other areas. However, due to resource constraints, lithium cannot meet the huge demand for battery raw materials in energy storage.

[0003] Sodium-ion batteries (SIBs) operate on a similar principle to lithium-ion batteries, but sodium resources offer unique advantages over lithium resources: abundant reserves and easy extraction; sodium does not undergo alloying reactions with aluminum, allowing aluminum foil to be used for both positive and negative electrode materials, resulting in lower costs compared to copper foil required for lithium-ion batteries; sodium has a low charge density, diffuses rapidly in both aqueous and non-aqueous electrolytes, and exhibits good stability and high safety at high temperatures between 30°C and 80°C. These advantages make sodium-ion batteries an ideal choice for large-scale energy storage technologies, attracting widespread attention in recent years. However, the large radius of sodium ions leads to severe phase changes and slow reaction kinetics in electrode materials during charge and discharge, limiting their application as electrode materials.

[0004] Sodium-ion batteries mainly consist of components such as positive electrode materials, negative electrode materials, electrolytes, and separators. Among these, the negative electrode material plays a crucial role in loading and releasing sodium ions, significantly impacting the overall power performance of the battery. Therefore, improvements to the negative electrode material in sodium-ion batteries are of great significance for enhancing their electrical performance. Summary of the Invention

[0005] To address the above technical problems, this invention provides a power-type sodium-ion anode material for energy storage, a battery, a preparation method, and applications. The power-type sodium-ion battery anode material provided by this invention exhibits high specific capacity, good rate performance, and good cycle stability, and can be used to manufacture power-type sodium-ion batteries for energy storage.

[0006] To achieve the above-mentioned objectives, the embodiments of the present invention adopt the following technical solutions:

[0007] The first aspect of this invention provides a method for preparing a negative electrode material for a power-type sodium-ion battery used for energy storage, specifically including the following operations:

[0008] Organic carbon source, black phosphorus and titanium source were ball-milled in an inert atmosphere, and then subjected to two heat treatments in an inert atmosphere: the first heat treatment was to heat to 400-550℃ at a heating rate of 2-6℃ / min and hold for 60-80min; the second heat treatment was to heat to 700-900℃ at a heating rate of 10-18℃ / min and hold for 1.5-2h.

[0009] The organic carbon source includes biochemical sludge, tar residue, and acidified plant tissue; the acidification process includes: soaking the plant tissue in a 3% to 6% wt phosphoric acid aqueous solution for 1 to 2 hours, washing it with water until neutral, and then drying it until the moisture content is ≤2.0%.

[0010] The preparation method provided by the present invention, through a specific precursor composition and heat treatment process, produces a negative electrode material that is a hard carbon material doped with phosphorus and titanium.

[0011] In this preparation method, the acidified plant tissue contains natural pores, providing a preliminary framework for the formation of the anode material. Biochemical sludge and tar residue are carbon-containing solid wastes with high carbon content, which can compensate for the low carbon yield in the preparation of hard carbon materials from plant tissue. Black phosphorus has a stable structure and possesses high carrier mobility, high theoretical capacity, good thermal stability, and high anisotropy, which helps improve the cycle stability of the anode material, but it suffers from volume expansion after sodium storage. Titanium doping helps shorten the Na... + The migration path increases the conductivity of the negative electrode material, making it suitable for Na. + The insertion and extraction of the material provides abundant sites, but the coulombic efficiency in the first week is low; the biochemical sludge and tar residue have a certain viscosity, which not only facilitates the doping of phosphorus and titanium during the formation of this negative electrode material, increasing the conductivity of the electrode, but also helps to maintain the negative electrode material in Na… + The volume and structure during sodium insertion / extraction processes are adjusted to maintain the battery's cycle life and rate performance.

[0012] The above raw materials, combined with two heat treatments in this preparation process, result in a negative electrode material with abundant and rationally distributed nanopores, moderate carbon interlayer spacing, and a large specific surface area, forming a cross-linked three-dimensional network. The open pores on the surface are particularly beneficial for Na... + Storage / Release; Cross-linked three-dimensional networks can improve the conductivity and enhance the structural stability of this anode material. This anode material can also form a graphite-like layer with defects such as edge defects, heteroatom doping defects, and vacancy defects. These defects become sodium storage sites with fast ion diffusion rates, providing a ramp capacity in the initial discharge stage and good sodium storage effect, resulting in a hard carbon material with better rate performance and conductivity. Simultaneously, Na... +The insertion potential is much higher than the sodium deposition potential, which can slow down polarization and electrolyte degradation, thereby improving cycle stability and further improving rate performance.

[0013] The heat treatment temperature of this preparation method is divided into two parts. The first heat treatment is at a lower temperature, which can reduce production costs compared to a process with high-temperature heat treatment throughout.

[0014] The biochemical sludge and tar residue in this preparation method are both solid wastes, and the plant tissues can be derived from waste agricultural and forestry residues, such as fruit shells, straw, dead branches, and dead leaves. The material cost is low, which is of great significance for the resource utilization of solid waste and the cost reduction of sodium-ion batteries.

[0015] In conjunction with the first aspect, the mass ratio of the biochemical sludge, tar residue, and acidified plant tissue is 2-4:1-3:5-7, and the water content of the biochemical sludge is 35%-45%.

[0016] In conjunction with the first aspect, the biochemical sludge and tar residue are solid wastes from coking plants.

[0017] Preferably, the molar ratio of phosphorus in the black phosphorus to carbon in the organic carbon source is 2 to 5:10.

[0018] Preferably, the molar ratio of titanium in the titanium source to carbon in the organic carbon source is 1.5 to 3:10.

[0019] Preferably, the titanium source is selected from at least one of titanium oxide and sodium titanate.

[0020] In conjunction with the first aspect, the preparation method further includes washing the product obtained from the first heat treatment with an aqueous solution of water and ethanol and drying it before the second heat treatment to remove raw materials or intermediates that did not participate in the reaction or carbonization.

[0021] A second aspect of the present invention provides a negative electrode material for a power sodium-ion battery for energy storage, which is prepared according to the above-described preparation method.

[0022] The third aspect of this invention provides the application of the above-mentioned negative electrode material in the preparation of a power sodium-ion battery for energy storage.

[0023] A fourth aspect of the present invention provides a power-type sodium-ion battery for energy storage, comprising a positive electrode material, a negative electrode material, an electrolyte, and a separator, wherein the negative electrode material is the negative electrode material of the aforementioned power-type sodium-ion battery for energy storage.

[0024] In conjunction with the fourth aspect, the cathode material includes at least one selected from sodium vanadium fluorophosphate (Na3V2(PO4)2F3), sodium vanadium phosphate (Na3V2(PO4)3), sodium iron phosphate (NaFePO4), sodium vanadium monofluorophosphate (NaVPO4F), and sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7). The above-mentioned cathode materials exhibit good electrochemical performance and excellent fast charge / discharge performance.

[0025] In conjunction with the fourth aspect, the electrolyte raw materials include a carbonate solvent, additives, and a sodium salt. The additives include at least one selected from fluoroethylene carbonate (FEC), pentafluoro-3',5'-bis(trifluoromethyl)-1,1'-biphenyl, difluoroethylene carbonate (DFEC), and tris(2,2,2-trifluoroethyl) phosphate (TFP). These additives promote the rate performance and long-cycle stability of the sodium-ion battery.

[0026] Preferably, the additive is at least two selected from fluoroethylene carbonate, pentafluoro-3',5'-bis(trifluoromethyl)-1,1'-biphenyl, difluoroethylene carbonate, and tris(2,2,2-trifluoroethyl) phosphate. Using at least two of the above additives in combination can produce better results in improving the rate performance and long-cycle stability of the sodium-ion battery.

[0027] Preferably, the volume of the additive is 3 to 10% of the volume of the carbonate solvent.

[0028] Preferably, the carbonate solvent includes at least one of ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), and ethylene carbonate (EC).

[0029] Preferably, the sodium salt is at least one selected from sodium tetrafluoroborate (NaBF4), sodium difluorosulfonamide, sodium difluorooxalate borate, sodium hexafluorophosphate (NaPF6), and sodium perchlorate (NaClO4). Using the above-mentioned sodium salts in the electrolyte achieves good conductivity and stability.

[0030] Preferably, the sodium salt is at least one selected from sodium tetrafluoroborate, sodium difluorosulfonamide, sodium difluorooxalate borate, and sodium hexafluorophosphate.

[0031] Preferably, the concentration of the sodium salt relative to the carbonate solvent is 0.3 to 0.8 mol / L.

[0032] The fifth aspect of this invention provides a method for preparing the above-mentioned power-type sodium-ion battery for energy storage, specifically including the following operations:

[0033] The sodium salt is added to the carbonate solvent, mixed evenly, and then the additive is added and mixed evenly. Water and oxygen are removed to obtain the electrolyte.

[0034] The positive electrode material, conductive agent, and binder are mixed, and N-methylpyrrolidone is used as the mixing medium to prepare a positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried, rolled, and cut to obtain a positive electrode sheet.

[0035] The above-mentioned negative electrode material, conductive agent, thickener and binder are mixed and deionized water is used as the mixing medium to prepare a negative electrode slurry; the negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector aluminum foil, dried and then rolled and cut to obtain a negative electrode sheet;

[0036] The positive electrode, separator, and negative electrode are manufactured into a power-type sodium-ion battery for energy storage using conventional rechargeable battery processes.

[0037] The preparation method of the present invention is simple to operate and can be easily implemented under laboratory conditions or on a commercial production scale.

[0038] For example, the preparation method may employ the following operations:

[0039] The sodium salt is added to the carbonate solvent, mixed evenly, and then the additive is added and mixed evenly. Water and oxygen are removed to obtain the electrolyte.

[0040] The above-mentioned positive electrode material, conductive carbon black, conductive carbon nanotubes, and binder polyvinylidene fluoride were mixed in a mass ratio of 94:2:1:3. N-methylpyrrolidone (NMP) was used as the mixing medium, and the positive electrode slurry was prepared by stirring with a planetary mixer. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried, rolled and cut to obtain the positive electrode sheet.

[0041] The above-mentioned negative electrode material, conductive agent carbon black, thickener sodium carboxymethyl cellulose and binder styrene-butadiene rubber (SBR) are mixed in a mass ratio of 95.5:1:1.5:2, and deionized water is used as the mixing medium. The negative electrode slurry is prepared by stirring with a planetary mixer. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector aluminum foil, dried, rolled and cut to obtain the negative electrode sheet.

[0042] The positive electrode, separator, and negative electrode are stacked in sequence after vacuum drying. The stacked core pack is then placed in an aluminum-plastic packaging shell for sealing. After sealing, it is vacuum dried. The vacuum-dried core pack is injected with electrolyte and then undergoes processes such as vacuuming, secondary sealing, standing, pre-charging, degassing, formation, and aging to produce a power sodium-ion battery for energy storage. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0044] The negative electrode material is a crucial component of sodium-ion batteries, providing sodium ion insertion sites and a low-potential redox couple for operation, thus significantly impacting the overall power performance of the battery. An ideal negative electrode material should possess high specific capacity, low redox potential, good cycle life, and high first-cycle coulombic efficiency. It should also meet high operating voltage requirements and be resistant to organic reactions with the electrolyte, thereby improving the energy density of the sodium-ion battery to some extent.

[0045] The anode is mainly composed of carbon-based and non-carbon materials. Carbon-based materials mainly include ordered carbon and disordered carbon; the former includes graphite and graphene, while the latter includes soft carbon and hard carbon. The large atomic radius of sodium ions prevents efficient insertion and extraction in graphite-based anode materials; graphene has good performance but is expensive; soft carbon has a lower reversible capacity than hard carbon. Hard carbon has a wide range of carbon sources, low cost, high theoretical specific capacity, low voltage plateau, small volume expansion, and good cycle performance, but its first-cycle efficiency is often low and its rate performance is poor. Furthermore, the pore size and structure of hard carbon materials have a significant impact on battery performance. For example, excessively large pore sizes can cause excessive decomposition of the electrolyte, resulting in a loss of reversible capacity; excessively small pore sizes may prevent sodium ions from inserting and diffusing. The formation of the pore size and structure of hard carbon materials depends on the precursor composition and heat treatment parameters, and it is not easy to obtain ideal pore size and structure through simple selection.

[0046] Non-carbon materials in anode materials mainly include titanium-based materials, organic materials, alloy materials, and metal oxides / sulfides. Titanium-based materials have low capacity, organic materials easily dissolve in the electrolyte, alloy materials tend to expand in volume after sodium ion insertion and exhibit poor reaction kinetics, and metal oxides / sulfides are prone to agglomeration. These shortcomings make their application still present many unresolved problems.

[0047] Based on extensive research, this invention provides a method for preparing a negative electrode material for a power-type sodium-ion battery used in energy storage, specifically including the following steps:

[0048] Organic carbon source, black phosphorus and titanium source were ball-milled in an inert atmosphere, and then subjected to two heat treatments in an inert atmosphere: the first heat treatment was to heat to 400-550℃ at a heating rate of 2-6℃ / min and hold for 60-80min; the second heat treatment was to heat to 700-900℃ at a heating rate of 10-18℃ / min and hold for 1.5-2h.

[0049] The organic carbon source includes biochemical sludge, tar residue, and acidified plant tissue; the acidification process includes: soaking the plant tissue in a 3% to 6% wt phosphoric acid aqueous solution for 1 to 2 hours, washing it with water until neutral, and then drying it until the moisture content is ≤2.0%.

[0050] In this embodiment, the biochemical sludge and tar residue are solid wastes from a coking plant. The mass ratio of biochemical sludge, tar residue, and acidified plant tissue is 2-4:1-3:5-7, and the water content of the biochemical sludge is 35%-45%.

[0051] In a preferred embodiment, the molar ratio of phosphorus in black phosphorus to carbon in the organic carbon source is 2-5:10, the molar ratio of titanium in the titanium source to carbon in the organic carbon source is 1.5-3:10, and the titanium source is selected from at least one of titanium oxide and sodium titanate.

[0052] As a preferred embodiment, the preparation method further includes washing the product obtained from the first heat treatment with an aqueous solution of water and ethanol and drying it before the second heat treatment.

[0053] This invention also provides a power-type sodium-ion battery for energy storage, wherein the negative electrode material is the same as that of the aforementioned power-type sodium-ion battery for energy storage.

[0054] As a preferred embodiment, the positive electrode material of the power sodium-ion battery for energy storage is at least one of sodium vanadium fluorophosphate (Na3V2(PO4)2F3), sodium vanadium phosphate (Na3V2(PO4)3), sodium iron phosphate (NaFePO4), sodium vanadium monofluorophosphate (NaVPO4F), and sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7).

[0055] As a preferred embodiment, the electrolyte of the power sodium-ion battery for energy storage comprises a carbonate solvent, additives, and a sodium salt. The additives include at least one of fluoroethylene carbonate (FEC), pentafluoro-3',5'-bis(trifluoromethyl)-1,1'-biphenyl, difluoroethylene carbonate (DFEC), and tris(2,2,2-trifluoroethyl) phosphate (TFP). The volume of the additives is 3 to 10% of the volume of the carbonate solvent.

[0056] As a more preferred embodiment, the carbonate solvent includes at least one of ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), and ethylene carbonate (EC), and the additive is at least two of fluoroethylene carbonate (FEC), pentafluoro-3',5'-bis(trifluoromethyl)-1,1'-biphenyl, difluoroethylene carbonate (DFEC), and tris(2,2,2-trifluoroethyl) phosphate (TFP).

[0057] In a preferred embodiment, the sodium salt in the electrolyte of the power sodium-ion battery for energy storage is at least one selected from sodium tetrafluoroborate (NaBF4), sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium hexafluorophosphate (NaPF6), and sodium perchlorate (NaClO4). In a more preferred embodiment, the sodium salt is at least one selected from NaBF4, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, and sodium hexafluorophosphate.

[0058] The embodiments of the present invention will be further described below with reference to several examples.

[0059] The biochemical sludge and tar residue in the following examples are both solid wastes from coking plants.

[0060] Example 1

[0061] This embodiment provides a negative electrode material for a power-type sodium-ion battery used for energy storage, and its preparation method is as follows:

[0062] The coconut shells were crushed to a particle size of <0.5cm, soaked in a 4% wt phosphoric acid aqueous solution for 1.5h, washed with water until neutral, and dried until the moisture content was ≤2.0%.

[0063] Using biochemical sludge, tar residue, and coconut shells treated with the above acidification (mass ratio 3:2:6) as organic carbon sources, the organic carbon source, black phosphorus, and titanium dioxide were placed in an argon-filled ball mill jar and ball-milled for 1 hour. The biochemical sludge had a water content of 41.2%, the molar ratio of phosphorus in black phosphorus to carbon in the organic carbon source was 3:10, and the molar ratio of titanium in titanium dioxide to carbon in the organic carbon source was 2:10.

[0064] The ball-milled material is heated to 470°C in an argon-filled tube furnace at a heating rate of 4°C / min and held at 460–480°C for 75 min. After natural cooling, it is first washed with water, then washed with a 50% wt ethanol aqueous solution, dried to a moisture content of ≤2%, and then heated to 800°C in an argon-filled tube furnace at a heating rate of 14°C / min and held at 790–810°C for 110 min. After natural cooling, the final product is obtained.

[0065] Example 2

[0066] This embodiment provides a negative electrode material for a power-type sodium-ion battery used for energy storage, and its preparation method is as follows:

[0067] The corn stalks were crushed to a particle size of <0.5cm, soaked in a 3% wt phosphoric acid aqueous solution for 2 hours, washed with water until neutral, and then dried to a moisture content of ≤2.0%.

[0068] Using biochemical sludge, tar residue, and corn stalks treated with the above acidification (mass ratio of 3:2:6) as organic carbon sources, the organic carbon source, black phosphorus, and titanium dioxide were ball-milled in an argon-filled ball mill jar for 1 hour; wherein, the water content of the biochemical sludge was 43.1%; the molar ratio of phosphorus in black phosphorus to carbon in the organic carbon source was 4:10; and the molar ratio of titanium in titanium dioxide to carbon in the organic carbon source was 2:10.

[0069] The ball-milled material is heated to 500°C in an argon-filled tube furnace at a heating rate of 4°C / min and held at 490–510°C for 75 min. After natural cooling, it is first washed with water, then washed with a 50% wt ethanol aqueous solution, dried to a moisture content of ≤2%, and then heated to 850°C in an argon-filled tube furnace at a heating rate of 12°C / min and held at 840–860°C for 100 min. After natural cooling, the final product is obtained.

[0070] Example 3

[0071] This embodiment provides a negative electrode material for a power-type sodium-ion battery used for energy storage, and its preparation method is as follows:

[0072] The bagasse was crushed to a particle size of <0.5cm, soaked in a 5% wt phosphoric acid aqueous solution for 1 hour, washed with water until neutral, and then dried to a moisture content of ≤2.0%.

[0073] Using biochemical sludge, tar residue, and sugarcane bagasse treated with the above acidification (mass ratio of 4:2:7) as organic carbon sources, the organic carbon sources, black phosphorus, and sodium titanate were ball-milled in an argon-filled ball mill jar for 1 hour. The biochemical sludge had a water content of 39.2%, the molar ratio of phosphorus in black phosphorus to carbon in the organic carbon source was 2:10, and the molar ratio of titanium in sodium titanate to carbon in the organic carbon source was 1.5:10.

[0074] The ball-milled material is heated to 550°C in an argon-filled tube furnace at a heating rate of 2°C / min and held at 530–550°C for 60 min. After natural cooling, it is first washed with water, then washed with a 50% wt ethanol aqueous solution, dried to a moisture content of ≤2%, and then heated to 750°C in an argon-filled tube furnace at a heating rate of 16°C / min and held at 740–760°C for 120 min. After natural cooling, the final product is obtained.

[0075] Example 4

[0076] This embodiment provides a negative electrode material for a power-type sodium-ion battery used for energy storage, and its preparation method is as follows:

[0077] The cotton stalks were crushed to a particle size of <0.5cm, soaked in a 6% wt phosphoric acid aqueous solution for 1 hour, washed with water until neutral, and then dried to a moisture content of ≤2.0%.

[0078] Using biochemical sludge, tar residue, and cotton stalks treated with the above acidification (mass ratio of 3:3:7) as organic carbon sources, the organic carbon source, black phosphorus, and sodium titanate were placed in a ball mill jar filled with argon and ball-milled for 1 hour. The biochemical sludge had a water content of 36.2%, the molar ratio of phosphorus in black phosphorus to carbon in the organic carbon source was 3:10, and the molar ratio of titanium in sodium titanate to carbon in the organic carbon source was 1:10.

[0079] The ball-milled material is heated to 450°C in an argon-filled tube furnace at a heating rate of 5°C / min and held at 440–460°C for 75 min. After natural cooling, it is first washed with water, then washed with a 50% wt ethanol aqueous solution, dried to a moisture content of ≤2%, and then heated to 700°C in an argon-filled tube furnace at a heating rate of 18°C / min and held at 700–720°C for 120 min. After natural cooling, the final product is obtained.

[0080] Example 5

[0081] This embodiment provides a negative electrode material for a power-type sodium-ion battery used for energy storage, and its preparation method is as follows:

[0082] The dead poplar and willow leaves were crushed to a particle size of <0.5cm, soaked in a 3% wt phosphoric acid aqueous solution for 1.5h, washed with water until neutral, and dried to a moisture content of ≤2.0%.

[0083] Using biochemical sludge, tar residue, and withered poplar and willow leaves (mass ratio of 2:1:5) treated with the above acidification as organic carbon sources, the organic carbon sources and titanium dioxide were placed in a ball mill jar filled with argon and ball-milled for 1 hour. The biochemical sludge had a water content of 44.3%, the molar ratio of phosphorus in black phosphorus to carbon in the organic carbon source was 5:10, and the molar ratio of titanium in titanium dioxide to carbon in the organic carbon source was 2:10.

[0084] The ball-milled material is heated to 400°C in an argon-filled tube furnace at a heating rate of 6°C / min and held at 400–420°C for 80 min. After natural cooling, it is first washed with water, then washed with a 50% wt ethanol aqueous solution, dried to a moisture content of ≤2%, and then heated to 900°C in an argon-filled tube furnace at a heating rate of 10°C / min and held at 880–900°C for 90 min. After natural cooling, the final product is obtained.

[0085] Example 6

[0086] This embodiment provides a power-type sodium-ion battery for energy storage. The negative electrode material is the negative electrode material prepared in Example 1, and the positive electrode material is sodium vanadium fluorophosphate and sodium vanadium phosphate (molar ratio of 2:1). The electrolyte raw materials include carbonate solvent, additives, and sodium salt. The carbonate solvent is ethyl methyl carbonate and ethylene carbonate (volume ratio of 1:1). The additives are fluoroethylene carbonate and pentafluoro-3',5'-bis(trifluoromethyl)-1,1'-biphenyl (volume ratio of 1:1). The volume of the additives is 6% of the volume of the carbonate solvent. The sodium salt is sodium tetrafluoroborate (concentration relative to the carbonate solvent is 0.5 mol / L). The separator is a polyethylene separator.

[0087] The preparation method of this power-type sodium-ion battery for energy storage is as follows:

[0088] (1) The preparation container is treated to remove water and oxygen, and nitrogen is continuously introduced during the preparation process. The above-mentioned carbonate solvent is added to the preparation container, followed by the above-mentioned sodium salt. After mixing evenly, the above-mentioned additives are added and mixed evenly to remove water and oxygen, thus obtaining the electrolyte;

[0089] (2) The above positive electrode material, conductive carbon black, conductive carbon nanotube, and binder polyvinylidene fluoride are mixed in a mass ratio of 94:2:1:3. N-methylpyrrolidone (NMP) is used as the mixing medium and the positive electrode slurry is prepared by stirring with a planetary mixer. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried, rolled and cut to obtain the positive electrode sheet.

[0090] (3) The negative electrode material obtained in Example 1, conductive carbon black, thickener sodium carboxymethyl cellulose and adhesive styrene-butadiene rubber (SBR) were mixed in a mass ratio of 95.5:1:1.5:2. Deionized water was used as the mixing medium and the negative electrode slurry was prepared by stirring with a planetary mixer. The negative electrode slurry was uniformly coated on both surfaces of the negative electrode current collector aluminum foil, dried and then rolled and cut to obtain the negative electrode sheet.

[0091] (4) The positive electrode, separator and negative electrode are stacked in sequence after vacuum drying. The stacked core pack is placed in an aluminum-plastic packaging shell for sealing. After sealing, it is vacuum dried. The vacuum dried core pack is injected with electrolyte. After vacuuming, secondary sealing, standing, pre-charging, degassing, formation and aging, a power sodium-ion battery for energy storage is made.

[0092] Example 7

[0093] This embodiment provides a power-type sodium-ion battery for energy storage. The negative electrode material is the negative electrode material prepared in Example 2, and the positive electrode material is sodium vanadium fluorophosphate and sodium vanadium phosphate (molar ratio of 2:1). The electrolyte raw materials include carbonate solvent, additives, and sodium salt. The carbonate solvent is ethyl methyl carbonate and ethylene carbonate (volume ratio of 1:1). The additives are difluoroethylene carbonate and tris(2,2,2-trifluoroethyl) phosphate (volume ratio of 1.5:1). The volume of the additives is 5% of the volume of the carbonate solvent. The sodium salt is sodium difluorosulfonyl imide (concentration relative to the carbonate solvent is 0.6 mol / L). The separator is a polyethylene separator.

[0094] The preparation method of this power-type sodium-ion battery for energy storage is the same as in Example 6.

[0095] Example 8

[0096] This embodiment provides a power-type sodium-ion battery for energy storage. The negative electrode material is the negative electrode material prepared in Example 3, and the positive electrode material is sodium vanadium fluorophosphate and sodium iron phosphate (molar ratio of 3:1). The electrolyte raw materials include carbonate solvent, additives, and sodium salt. The carbonate solvent is diethyl carbonate and ethylene carbonate (volume ratio of 1:1). The additives are pentafluoro-3',5'-bis(trifluoromethyl)-1,1'-biphenyl and tris(2,2,2-trifluoroethyl) phosphate (volume ratio of 1.5:1). The volume of the additives is 3% of the volume of the carbonate solvent. The sodium salt is sodium difluorooxalate borate (concentration relative to carbonate solvent is 0.5 mol / L). The separator is a polyethylene separator.

[0097] The preparation method of this power-type sodium-ion battery for energy storage is the same as in Example 6.

[0098] Example 9

[0099] This embodiment provides a power-type sodium-ion battery for energy storage. The negative electrode material is the negative electrode material prepared in Example 4, and the positive electrode material is sodium vanadium monofluorophosphate. The electrolyte raw materials include carbonate solvent, additives, and sodium salts. The carbonate solvent is diethyl carbonate and ethylene carbonate (volume ratio of 1:1). The additives are fluoroethylene carbonate and difluoroethylene carbonate, with the volume of the additives being 7% of the volume of the carbonate solvent. The sodium salts are sodium tetrafluoroborate (concentration relative to the carbonate solvent is 0.1 mol / L) and sodium difluorooxalate borate (concentration relative to the carbonate solvent is 0.2 mol / L). The separator is a polyethylene separator.

[0100] The preparation method of this power-type sodium-ion battery for energy storage is the same as in Example 6.

[0101] Example 10

[0102] This embodiment provides a power-type sodium-ion battery for energy storage. The negative electrode material is the negative electrode material prepared in Example 5, and the positive electrode material is sodium vanadium fluorophosphate. The electrolyte raw materials include carbonate solvent, additives, and sodium salts. The carbonate solvent is ethyl methyl carbonate, diethyl carbonate, and ethylene carbonate (volume ratio of 1:1:2). The additive is fluoroethylene carbonate, and the volume of the additive is 10% of the volume of the carbonate solvent. The sodium salts are sodium difluorosulfonyl imide (concentration relative to the carbonate solvent is 0.5 mol / L) and sodium difluorooxalate borate (concentration relative to the carbonate solvent is 0.3 mol / L). The separator is a polyethylene separator.

[0103] The preparation method of this power-type sodium-ion battery for energy storage is the same as in Example 6.

[0104] Example 11

[0105] This embodiment provides a power-type sodium-ion battery for energy storage. The negative electrode material is the negative electrode material prepared in Example 1, the positive electrode material is sodium vanadium phosphate, and the electrolyte raw materials include carbonate solvent, additives, and sodium salt. The carbonate solvent is ethyl methyl carbonate and ethylene carbonate (volume ratio of 1:1), the additive is pentafluoro-3',5'-bistrifluoromethyl-1,1'-biphenyl, the volume of the additive is 10% of the volume of the carbonate solvent, the sodium salt is sodium perchlorate (concentration relative to the carbonate solvent is 0.8 mol / L), and the separator is a polyethylene separator.

[0106] The preparation method of this power-type sodium-ion battery for energy storage is the same as in Example 6.

[0107] Example 12

[0108] This embodiment provides a power-type sodium-ion battery for energy storage. The negative electrode material is the negative electrode material prepared in Example 1, the positive electrode material is sodium iron pyrophosphate, and the electrolyte raw materials include carbonate solvent, additives, and sodium salt. The carbonate solvent is ethyl methyl carbonate and ethylene carbonate (volume ratio of 1:1), the additives are difluoroethylene carbonate and tris(2,2,2-trifluoroethyl) phosphate, the volume of the additives is 7% of the volume of the carbonate solvent, the sodium salt is sodium hexafluorophosphate (concentration relative to the carbonate solvent is 0.5 mol / L), and the separator is a polyethylene separator.

[0109] The preparation method of this power-type sodium-ion battery for energy storage is the same as in Example 6.

[0110] Comparative Example 1

[0111] This comparative example provides a power-type sodium-ion battery for energy storage, and the method for preparing its negative electrode material is as follows:

[0112] Crush the coconut shells to a particle size of <0.5cm, soak them in water for 1.5 hours, wash them, and dry them until the moisture content is ≤2.0%.

[0113] Using biochemical sludge, tar residue, and coconut shells treated with the above acidification (mass ratio 3:2:6) as organic carbon sources, the organic carbon source, black phosphorus, and titanium dioxide were placed in an argon-filled ball mill jar and ball-milled for 1 hour. The biochemical sludge had a water content of 41.2%, the molar ratio of phosphorus in black phosphorus to carbon in the organic carbon source was 3:10, and the molar ratio of titanium in titanium dioxide to carbon in the organic carbon source was 2:10.

[0114] The ball-milled material is heated to 470°C in an argon-filled tube furnace at a heating rate of 4°C / min and held at 460–480°C for 75 min. After natural cooling, it is first washed with water, then washed with a 50% wt ethanol aqueous solution, dried to a moisture content of ≤2%, and then heated to 800°C in an argon-filled tube furnace at a heating rate of 14°C / min and held at 790–810°C for 110 min. After natural cooling, the final product is obtained.

[0115] The cathode material, electrolyte, and preparation method are the same as in Example 6.

[0116] Comparative Example 2

[0117] This comparative example provides a power-type sodium-ion battery for energy storage, and the method for preparing its negative electrode material is as follows:

[0118] The coconut shells were crushed to a particle size of <0.5cm, soaked in a 4% wt phosphoric acid aqueous solution for 1.5h, washed with water until neutral, and dried until the moisture content was ≤2.0%.

[0119] Using epoxy resin and the above-mentioned acidified coconut shell (mass ratio 5:6) as organic carbon sources, the organic carbon source, black phosphorus, and titanium dioxide were placed in an argon-filled ball mill jar and ball-milled for 1 hour; wherein, the water content of the biological sludge was 41.2%, the molar ratio of phosphorus in black phosphorus to carbon in organic carbon source was 3:10, and the molar ratio of titanium in titanium dioxide to carbon in organic carbon source was 2:10;

[0120] The ball-milled material is heated to 470°C in an argon-filled tube furnace at a heating rate of 4°C / min and held at 460–480°C for 75 min. After natural cooling, it is first washed with water, then washed with a 50% wt ethanol aqueous solution, dried to a moisture content of ≤2%, and then heated to 800°C in an argon-filled tube furnace at a heating rate of 14°C / min and held at 790–810°C for 110 min. After natural cooling, the final product is obtained.

[0121] The cathode material, electrolyte, and preparation method are the same as in Example 6.

[0122] Comparative Example 3

[0123] This comparative example provides a power-type sodium-ion battery for energy storage, and the method for preparing its negative electrode material is as follows:

[0124] The coconut shells were crushed to a particle size of <0.5cm, soaked in a 4% wt phosphoric acid aqueous solution for 1.5h, washed with water until neutral, and dried until the moisture content was ≤2.0%.

[0125] Using biochemical sludge, tar residue, and coconut shells treated with the above acidification (mass ratio 3:2:6) as organic carbon sources, the organic carbon source, black phosphorus, and titanium dioxide were placed in an argon-filled ball mill jar and ball-milled for 1 hour. The biochemical sludge had a water content of 41.2%, the molar ratio of phosphorus in black phosphorus to carbon in the organic carbon source was 3:10, and the molar ratio of titanium in titanium dioxide to carbon in the organic carbon source was 2:10.

[0126] The ball-milled material is heated to 470°C in an argon-filled tube furnace at a heating rate of 10°C / min and held at 460–480°C for 75 min. After natural cooling, it is first washed with water, then washed with a 50% wt ethanol aqueous solution, dried to a moisture content of ≤2%, and then heated to 800°C in an argon-filled tube furnace at a heating rate of 30°C / min and held at 790–810°C for 110 min. After natural cooling, the final product is obtained.

[0127] The cathode material, electrolyte, and preparation method are the same as in Example 6.

[0128] Comparative Example 4

[0129] This comparative example provides a power-type sodium-ion battery for energy storage, and the method for preparing its negative electrode material is as follows:

[0130] The coconut shells were crushed to a particle size of <0.5cm, soaked in a 4% wt phosphoric acid aqueous solution for 1.5h, washed with water until neutral, and dried until the moisture content was ≤2.0%.

[0131] Using biochemical sludge, tar residue, and coconut shells treated with the above acidification (mass ratio 3:2:6) as organic carbon sources, the organic carbon source, black phosphorus, and titanium dioxide were placed in an argon-filled ball mill jar and ball-milled for 1 hour. The biochemical sludge had a water content of 41.2%, the molar ratio of phosphorus in black phosphorus to carbon in the organic carbon source was 3:10, and the molar ratio of titanium in titanium dioxide to carbon in the organic carbon source was 2:10.

[0132] The ball-milled material is heated to 470°C in an argon-filled tube furnace at a heating rate of 0.5°C / min and held at 460–480°C for 75 min. After natural cooling, it is first washed with water, then washed with a 50% wt ethanol aqueous solution, dried to a moisture content of ≤2%, and then heated to 800°C in an argon-filled tube furnace at a heating rate of 5°C / min and held at 790–810°C for 110 min. After natural cooling, the final product is obtained.

[0133] The cathode material, electrolyte, and preparation method are the same as in Example 6.

[0134] Comparative Example 5

[0135] This comparative example provides a power-type sodium-ion battery for energy storage, and the method for preparing its negative electrode material is as follows:

[0136] The coconut shells were crushed to a particle size of <0.5cm, soaked in a 4% wt phosphoric acid aqueous solution for 1.5h, washed with water until neutral, and dried until the moisture content was ≤2.0%.

[0137] Using biochemical sludge, tar residue, and coconut shells treated with the above acidification (mass ratio 3:2:6) as organic carbon sources, the organic carbon source, black phosphorus, and titanium dioxide were placed in an argon-filled ball mill jar and ball-milled for 1 hour. The biochemical sludge had a water content of 41.2%, the molar ratio of phosphorus in black phosphorus to carbon in the organic carbon source was 3:10, and the molar ratio of titanium in titanium dioxide to carbon in the organic carbon source was 2:10.

[0138] The ball-milled material is heated to 800°C in an argon-filled tube furnace at a heating rate of 4°C / min and held at 790–810°C for 75 min. After natural cooling, it is first washed with water, then washed with a 50% wt ethanol aqueous solution, dried to a moisture content of ≤2%, and then heated to 1200°C in an argon-filled tube furnace at a heating rate of 14°C / min and held at 1210–1220°C for 110 min. After natural cooling, the final product is obtained.

[0139] The cathode material, electrolyte, and preparation method are the same as in Example 6.

[0140] Comparative Example 6

[0141] This comparative example provides a power-type sodium-ion battery for energy storage, and the method for preparing its negative electrode material is as follows:

[0142] The coconut shells were crushed to a particle size of <0.5cm, soaked in a 4% wt phosphoric acid aqueous solution for 1.5h, washed with water until neutral, and dried until the moisture content was ≤2.0%.

[0143] Using biochemical sludge, tar residue, and coconut shells treated with the above acidification (mass ratio 3:2:6) as organic carbon sources, the organic carbon source, black phosphorus, and titanium dioxide were placed in an argon-filled ball mill jar and ball-milled for 1 hour. The biochemical sludge had a water content of 41.2%, the molar ratio of phosphorus in black phosphorus to carbon in the organic carbon source was 3:10, and the molar ratio of titanium in titanium dioxide to carbon in the organic carbon source was 2:10.

[0144] The ball-milled material is heated to 300°C in an argon-filled tube furnace at a heating rate of 4°C / min and held at 290–310°C for 75 min. After natural cooling, it is first washed with water, then washed with a 50% wt ethanol aqueous solution, dried to a moisture content of ≤2%, and then heated to 600°C in an argon-filled tube furnace at a heating rate of 14°C / min and held at 590–610°C for 110 min. After natural cooling, the final product is obtained.

[0145] The cathode material, electrolyte, and preparation method are the same as in Example 6.

[0146] Test Example

[0147] This test example evaluated the performance of sodium-ion batteries prepared in Examples 6-11 and Comparative Examples 1-6. The results are shown in Table 1.

[0148] Table 1. Electrical Performance Test Results

[0149]

[0150] It is evident that the sodium-ion batteries provided in each embodiment have significantly better discharge capacity, rate performance, and cycle stability than the sodium-ion batteries provided in the comparative example.

[0151] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a negative electrode material for a power-type sodium-ion battery for energy storage, characterized in that, Specifically, the following operations are included: Organic carbon source, black phosphorus and titanium source were ball-milled in an inert atmosphere, and then subjected to two heat treatments in an inert atmosphere: the first heat treatment was to heat to 400-550℃ at a heating rate of 2-6℃ / min and hold for 60-80min; the second heat treatment was to heat to 700-900℃ at a heating rate of 10-18℃ / min and hold for 1.5-2h. The organic carbon source includes biochemical sludge, tar residue, and acidified plant tissue. The acidification process includes: soaking plant tissue in a 3%~6% wt phosphoric acid aqueous solution for 1~2 hours, washing with water until neutral, and drying until the moisture content is ≤2.0%.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the biochemical sludge, tar residue, and acidified plant tissue is 2~4:1~3:5~7, and the water content of the biochemical sludge is 35%~45%.

3. The preparation method according to claim 2, characterized in that, The molar ratio of phosphorus in the black phosphorus to carbon in the organic carbon source is 2~5:10; and / or The molar ratio of titanium in the titanium source to carbon in the organic carbon source is 1.5~3:10; and / or The titanium source is selected from at least one of titanium oxide and sodium titanate.

4. The preparation method according to claim 1, characterized in that, It also includes washing the product obtained from the first heat treatment with an aqueous solution of water and ethanol before the second heat treatment and then drying it.

5. A negative electrode material for a power-type sodium-ion battery for energy storage, characterized in that, Prepared according to the preparation method according to any one of claims 1 to 4.

6. The application of the negative electrode material according to claim 5 in the preparation of a power sodium-ion battery for energy storage.

7. A power-type sodium-ion battery for energy storage, characterized in that, It includes a positive electrode material, a negative electrode material, an electrolyte, and a separator, wherein the negative electrode material is the negative electrode material as described in claim 5.

8. The power-type sodium-ion battery for energy storage according to claim 7, characterized in that, The positive electrode material includes at least one of sodium vanadium fluorophosphate, sodium vanadium phosphate, sodium iron phosphate, sodium vanadium monofluorophosphate, and sodium iron pyrophosphate; and / or The electrolyte raw materials include carbonate solvent, additives, and sodium salts. The additives include at least one of fluoroethylene carbonate, pentafluoro-3',5'-bis(trifluoromethyl)-1,1'-biphenyl, difluoroethylene carbonate, and tris(2,2,2-trifluoroethyl) phosphate.

9. The power-type sodium-ion battery for energy storage according to claim 8, characterized in that, In the electrolyte, the carbonate solvent includes at least one of methyl ethyl carbonate and diethyl carbonate, and ethylene carbonate; and / or In the electrolyte, the sodium salt is at least one of sodium tetrafluoroborate, sodium difluorosulfonamide, sodium difluorooxalate borate, sodium hexafluorophosphate, and sodium perchlorate.

10. The method for preparing a power-type sodium-ion battery for energy storage according to any one of claims 8 or 9, characterized in that, Specifically, the operation includes the following steps: adding the sodium salt to the carbonate solvent, mixing evenly, then adding the additive, mixing evenly, removing water and oxygen, and thus obtaining the electrolyte; The positive electrode material, conductive agent, and binder are mixed, and N-methylpyrrolidone is used as the mixing medium to prepare a positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector aluminum foil, dried, rolled, and cut to obtain a positive electrode sheet. The negative electrode material, conductive agent, thickener and binder described in claim 5 are mixed and deionized water is used as the mixing medium to prepare a negative electrode slurry; the negative electrode slurry is uniformly coated on the two surfaces of the negative electrode current collector aluminum foil, dried and then rolled and cut to obtain a negative electrode sheet. The positive electrode, separator, and negative electrode are manufactured into a power-type sodium-ion battery for energy storage using conventional rechargeable battery processes.

Images