Preparation method of negative electrode active material, battery and preparation method thereof, and electric device

Abstract

The invention discloses a preparation method of a negative electrode active material, a battery, a preparation method of the battery and a power utilization device. The battery comprises a positive electrode plate, a negative electrode plate and an electrolyte, wherein the negative electrode plate comprises a negative electrode active material, the negative electrode active material comprises an inner core and a coating layer at least partially coating the inner core, the inner core comprises a negative electrode active material, the coating layer comprises lithium difluorophosphate, and the mass ratio of phosphorus in the coating layer is 0.3%-10%. The surface of the negative electrode active material of the battery is coated with the coating layer containing the lithium difluorophosphate, so that the stability of an SEI film can be improved, the charge transfer impedance of the battery is reduced, and for electrolyte salt containing fluorine and / or phosphate radicals, the self-decomposition reaction of the electrolyte salt can be effectively inhibited, the generation of hydrogen fluoride is reduced, and the service life of the battery is prolonged. And the cycle performance of the battery can be improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a method for preparing a negative electrode active material, a battery and its preparation method, and an electrical device. Background Technology

[0002] Lithium-ion batteries are widely used due to their advantages such as high energy density, high output power, long cycle life, and low environmental pollution. In lithium-ion batteries, the negative electrode active material is a crucial factor affecting battery performance. However, most negative electrode active materials undergo volume expansion during charge and discharge, leading to delamination, and are prone to side reactions with the electrolyte, which in turn affects the battery's cycle stability. Summary of the Invention

[0003] This application is made in view of the above-mentioned issues, and its purpose is to provide a method for preparing a negative electrode active material, a battery and the same method, and an electrical device that can improve the cycle performance of the battery.

[0004] To achieve the above objectives, embodiments of this application provide a method for preparing a negative electrode active material, a battery and the same, and an electrical device.

[0005] In a first aspect, embodiments of this application propose a battery comprising a positive electrode, a negative electrode, and an electrolyte; wherein the negative electrode comprises a negative electrode active material, the negative electrode active material comprising a core and a coating layer at least partially covering the core, the core comprising a negative electrode active substance, the coating layer comprising lithium difluorophosphate, and the mass percentage of phosphorus in the coating layer being 0.3% to 10%.

[0006] Therefore, in the technical solution of this application embodiment, the surface of the negative electrode active material of the battery is coated with a coating layer containing lithium difluorophosphate. During the charging and discharging process of the battery, the coating layer will preferentially contact the electrolyte, and the lithium difluorophosphate will undergo a decomposition reaction to generate lithium fluoride (LiF) and lithium phosphate (Li3PO4). This can improve the stability of the SEI film (solid electrolyte interface), reduce the charge transfer impedance of the battery, and improve the ion conduction capacity inside the battery. Moreover, for electrolyte salts containing fluorine and / or phosphate, the decomposition products of the coating layer contain a large number of strong electrolytes with the same ions as the electrolyte salt anions, which can effectively inhibit the self-decomposition reaction of the electrolyte salt, reduce the generation of hydrogen fluoride, reduce the corrosive effect of hydrogen fluoride on the positive and negative electrode materials, and thus improve the cycle performance of the battery. The mass ratio of phosphorus in the coating layer is 0.3% to 10%, which can effectively improve the cycle performance of the battery.

[0007] In any embodiment, the thickness of the coating layer is 2 nm to 60 nm. Within this thickness range, it is beneficial to improve the cycle performance of the battery.

[0008] In any embodiment, the negative electrode active material includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, and silicon-based materials. Using at least one of the above-mentioned negative electrode active materials results in lower cost, easier processing, and, when combined with the coating layer, improves the cycle performance of the battery.

[0009] In any embodiment, the D of the negative electrode active material v 50 is 10nm~25μm. A coating layer containing lithium difluorophosphate is formed on the surface of the negative electrode active material, resulting in the D of the negative electrode active material. v Within this range, 50 is beneficial for improving the cycle performance of the battery.

[0010] In any embodiment, the coating layer further includes carrageenan. Carrageenan can form a surface with multiple oxygen-containing functional groups with the negative electrode active material. The surface will have more -OH and COOH functional groups and an increase in surface oxygen content. Through hydrogen bonding, lithium difluorophosphate can be more uniformly attached to the surface of the negative electrode active material, which is beneficial to improving the cycle performance of the battery.

[0011] In any embodiment, the molar concentration of lithium salt in the electrolyte is 0.6 mol / L to 2 mol / L. The electrolyte comprises a solvent and an electrolyte lithium salt, and the molar concentration of lithium salt in the electrolyte within the above range is beneficial for ensuring the cycle performance of the battery.

[0012] In any embodiment, the lithium salt in the electrolyte includes at least one of lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium difluorooxalato)borate, lithium difluorosulfonylimide, and lithium bis(trifluoromethanesulfonylimide). Using at least one of the above lithium salts helps to ensure the cycle performance of the battery.

[0013] Secondly, embodiments of this application propose a method for preparing a negative electrode active material, comprising the following steps:

[0014] Lithium difluorophosphate was mixed with a solvent to obtain a precursor solution;

[0015] The negative electrode active material is added to the precursor solution, stirred and reacted, and then dried to obtain the negative electrode active material.

[0016] The negative electrode active material includes a core and a coating layer that at least partially covers the core. The core includes a negative electrode active substance, and the coating layer includes lithium difluorophosphate.

[0017] By mixing lithium difluorophosphate with a solvent to obtain a precursor solution, and then using a liquid-phase method to form a coating layer on the surface of the negative electrode active material, lithium difluorophosphate can be effectively loaded onto the surface of the negative electrode active material. The coating layer has a simple composition, which can effectively avoid the generation of by-products, thereby improving the cycle performance of the battery. Moreover, the preparation method of the negative electrode active material is simple, which can improve production efficiency and reduce production costs.

[0018] In any embodiment, in the step of mixing lithium difluorophosphate with a solvent to obtain a precursor solution:

[0019] The mass ratio of lithium difluorophosphate to the solvent is 1:(10~10) 5 The mass ratio of lithium difluorophosphate to the solvent within this range is beneficial for the dissolution and uniform dispersion of lithium difluorophosphate, resulting in a more uniform distribution of lithium difluorophosphate in the coating layer. It also facilitates the formation of a coating layer with an appropriate lithium difluorophosphate content on the surface of the negative electrode active material, thereby improving the battery's cycle performance; and / or,

[0020] The solvent includes at least one selected from water, xylene, methanol, ethanol, acetonitrile, tetrahydrofuran, ethyl acetate, cyclohexane, butanone, acetone, and petroleum ether. Using at least one of the above solvents facilitates the dissolution and uniform dispersion of lithium difluorophosphate, resulting in a more uniform distribution of lithium difluorophosphate in the coating layer, which is beneficial for improving the battery's cycle performance; and / or,

[0021] Lithium difluorophosphate is mixed with a solvent under an inert atmosphere. Mixing lithium difluorophosphate with a solvent under an inert atmosphere can effectively avoid the generation of by-products in the coating layer, which is beneficial to improving the cycle performance of the battery.

[0022] In any embodiment, the step of mixing lithium difluorophosphate with a solvent to obtain a precursor solution includes:

[0023] Carrageenan was mixed with a solvent, and then lithium difluorophosphate was added and mixed to obtain a precursor solution.

[0024] By adding carrageenan, lithium difluorophosphate in the precursor solution can be kept uniformly dispersed. At the same time, during the liquid-phase coating process, carrageenan can form a surface with multiple oxygen-containing functional groups with the negative electrode active material. The surface will have more -OH and COOH functional groups and the surface oxygen content will increase. Through hydrogen bonding, lithium difluorophosphate is uniformly attached to the surface of the negative electrode active material to form a coating layer. The resulting negative electrode active material is beneficial to further improve the cycle performance of the battery.

[0025] In any embodiment, the step of mixing carrageenan with a solvent, then adding lithium difluorophosphate and mixing to obtain a precursor solution:

[0026] The mass ratio of carrageenan to the solvent is 1:(5×10⁻⁶). 3 ~5×10 6 The mass ratio of carrageenan to the solvent is within this range, which helps to maintain a better uniform dispersion of lithium difluorophosphate in the precursor solution, and can make the distribution of lithium difluorophosphate in the coating layer more uniform, which is beneficial to improving the cycle performance of the battery.

[0027] In any embodiment, in the step of adding the negative electrode active material to the precursor solution, stirring and reacting, and drying to obtain the negative electrode active material: the mass ratio of lithium difluorophosphate in the precursor solution to the negative electrode active material is (0.01~10):100. Within this range, the mass ratio of lithium difluorophosphate in the precursor solution to the negative electrode active material allows lithium difluorophosphate to form a beneficial coating layer structure on the surface of the negative electrode active material, effectively reducing the erosion of the negative electrode active material surface by the electrolyte, inhibiting side reactions, and improving the cycle performance of the battery.

[0028] In any embodiment, the step of adding the negative electrode active material to the precursor solution, stirring the reaction, and drying to obtain the negative electrode active material:

[0029] The stirring reaction is carried out under an inert atmosphere. Conducting the stirring reaction under an inert atmosphere effectively avoids the formation of byproducts in the coating layer, which is beneficial for improving the battery's cycle performance; and / or,

[0030] The stirring speed of the reaction is 100 rpm to 2000 rpm. Stirring within this speed range is beneficial for forming a uniform coating layer on the surface of the negative electrode active material, which can improve the battery's cycle performance; and / or,

[0031] The stirring reaction is carried out at a temperature of 25°C to 80°C. Stirring within this temperature range promotes the formation of a uniform coating layer on the surface of the negative electrode active material, thereby improving the battery's cycle performance; and / or,

[0032] The stirring reaction time is from 0.1 h to 24 h. Stirring the reaction within this time range is beneficial for the formation of a coating layer on the surface of the negative electrode active material, which can improve the cycle performance of the battery.

[0033] In any embodiment, the step of adding the negative electrode active material to the precursor solution, stirring the reaction, and drying to obtain the negative electrode active material:

[0034] The process involves filtration prior to drying. After stirring and reacting, filtration followed by drying facilitates the formation of a uniform coating layer on the surface of the negative electrode active material, thereby improving the battery's cycle performance; and / or,

[0035] The drying temperature is between 25°C and 140°C. Drying within this temperature range is beneficial for forming a uniform coating layer on the surface of the negative electrode active material, which can improve the cycle performance of the battery.

[0036] Thirdly, embodiments of this application propose a method for preparing a battery, comprising the following steps:

[0037] The negative electrode active material prepared by the negative electrode active material preparation method of the second aspect of this application is formulated into a negative electrode slurry;

[0038] The negative electrode slurry is coated onto at least one side of the negative electrode current collector to obtain a negative electrode sheet;

[0039] The negative electrode, positive electrode, and electrolyte are assembled to obtain a battery.

[0040] A battery made from a negative electrode active material prepared using the method of the second aspect of this application can improve the cycle performance of the battery.

[0041] Fourthly, embodiments of this application provide an electrical device, including a battery prepared by the method of the first aspect of this application or the third aspect of this application. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0043] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0044] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0045] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0046] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0047] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0048] Explanation of reference numerals in the attached figures:

[0049] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0050] The following details the preparation method of the negative electrode active material, the battery and its preparation method, and the embodiment of the electrical device according to this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0051] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0052] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0053] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0054] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0055] Lithium-ion batteries are widely used due to their advantages such as high energy density, high output power, long cycle life, and low environmental pollution. In lithium-ion batteries, the negative electrode active material is a crucial factor affecting battery performance. However, most negative electrode active materials undergo volume expansion during charge and discharge, leading to delamination, and are prone to side reactions with the electrolyte, which in turn affects the battery's cycle stability.

[0056] Based on this, this application provides a method for preparing a negative electrode active material, a battery, the same method for preparing the battery, and an electrical device thereof.

[0057] In a first aspect, embodiments of this application propose a battery comprising a positive electrode, a negative electrode, and an electrolyte; wherein the negative electrode comprises a negative electrode active material, the negative electrode active material comprising a core and a coating layer at least partially covering the core, the core comprising a negative electrode active substance, the coating layer comprising lithium difluorophosphate, and the mass percentage of phosphorus in the coating layer being 0.3% to 10%.

[0058] Therefore, in the technical solution of this application embodiment, the negative electrode active material is coated with a coating layer containing lithium difluorophosphate. During the battery charging and discharging process, the coating layer preferentially contacts the electrolyte, and the lithium difluorophosphate undergoes a decomposition reaction to generate lithium fluoride (LiF) and lithium phosphate (Li3PO4). This can improve the stability of the SEI film, reduce the charge transfer impedance of the battery, and improve the ion conduction capacity inside the battery. Furthermore, for electrolyte salts containing fluorine and / or phosphate, the decomposition products of the coating layer contain a large number of strong electrolytes with the same ions as the electrolyte salt anions, which can effectively suppress... The self-decomposition reaction of electrolyte salts reduces the generation of hydrogen fluoride and its corrosive effect on positive and negative electrode materials, thereby improving the cycle performance of the battery. The mass ratio of phosphorus in the coating layer is 0.3% to 10%, which can effectively improve the cycle performance of the battery. If the mass ratio of phosphorus in the coating layer is less than 0.3%, the low phosphorus content cannot achieve the desired effect. If the mass ratio of phosphorus in the coating layer is higher than 10%, the excessive phosphorus will cause additional chemical reactions and hinder the electrochemical reaction, resulting in the mechanical, thermal, and electrical properties of the coating layer not meeting expectations.

[0059] It is understood that the coating layer of the negative electrode active material can be either partially or fully coated onto the core. It should be noted that the decomposition equation of lithium difluorophosphate includes: LiPO2F2 + H2O → LiF + Li3PO4.

[0060] In any embodiment, the thickness of the coating layer is 2 nm to 60 nm. Within this thickness range, it is beneficial to improve the cycle performance of the battery; if the coating layer thickness is less than 2 nm, the negative electrode active material will be exposed in large areas, resulting in a less significant gain effect; if the coating layer thickness is greater than 60 nm, the coating layer will lose stability and be prone to breakage during cycling, entering the electrolyte and affecting the gain effect. The thickness of the coating layer can be 2 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, or 60 nm.

[0061] In any embodiment, the negative electrode active material includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, and silicon-based materials. Using at least one of the above-mentioned negative electrode active materials results in lower cost, easier processing, and, when combined with the coating layer, improves the battery's cycle performance. The negative electrode active material can be any one or any combination of artificial graphite, natural graphite, soft carbon, hard carbon, and silicon-based materials. It is understood that the silicon-based material can be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys; the artificial graphite can be selected from at least one of primary particles and secondary particles; the shape of the negative electrode active material can be spherical or irregular. Furthermore, for artificial graphite, its specific surface area is 0.5 m². 2 / g~20m 2 / g, which is beneficial for the loading of lithium difluorophosphate, and the specific surface area of ​​artificial graphite can be 0.5m². 2 / g, 0.8m 2 / g, 1m 2 / g, 1.2m 2 / g, 1.5m 2 / g、2m 2 / g, 2.5m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g, 10m 2 / g, 15m 2 / g or 20m 2 / g.

[0062] In any embodiment, the D of the negative electrode active material v 50 is 10nm~25μm. A coating layer containing lithium difluorophosphate is formed on the surface of the negative electrode active material, resulting in the D of the negative electrode active material. v Within this range, 50 is beneficial for improving the cycle performance of the battery; the D of the negative electrode active material v50 can be 10nm, 100nm, 1μm, 5μm, 10μm, 15μm, 20μm or 25μm.

[0063] In any embodiment, the coating layer further includes carrageenan. Carrageenan can form a surface with multiple oxygen-containing functional groups with the negative electrode active material. The surface will have more -OH and COOH functional groups and an increase in surface oxygen content. Through hydrogen bonding, lithium difluorophosphate can be more uniformly attached to the surface of the negative electrode active material, which is beneficial to improving the cycle performance of the battery.

[0064] In any embodiment, the molar concentration of lithium salt in the electrolyte is 0.6 mol / L to 2 mol / L. The electrolyte comprises a solvent and an electrolyte lithium salt, and the molar concentration of lithium salt in the electrolyte within the above range is beneficial for ensuring the cycle performance of the battery. The molar concentration of lithium salt in the electrolyte can be 0.6 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, or 2 mol / L.

[0065] In any embodiment, the lithium salt in the electrolyte includes at least one of lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium difluorooxalatoborate, lithium difluorosulfonylimide, and lithium bis(trifluoromethanesulfonylimide). Using at least one of the above lithium salts is beneficial for ensuring the cycle performance of the battery; the lithium salt in the electrolyte can be any one or any combination of lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium difluorooxalatoborate, lithium difluorosulfonylimide, and lithium bis(trifluoromethanesulfonylimide).

[0066] In some embodiments, the solvent in the electrolyte may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0067] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0068] For a positive electrode, the positive electrode includes a positive current collector and a positive film layer disposed on at least one surface of the positive current collector.

[0069] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0070] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0071] In some embodiments, the positive electrode active material may be a known positive electrode active material for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0072] In some embodiments, the positive electrode film layer further includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0073] In some embodiments, the positive electrode film layer further includes a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0074] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode sheet structure, and obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0075] For a negative electrode sheet, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0076] As an example, the negative electrode structure includes a negative current collector having two surfaces opposite each other in its own thickness direction, and a negative electrode film layer disposed on either or both of the two opposite surfaces of the negative current collector structure.

[0077] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0078] In some embodiments, the negative electrode film layer further includes an adhesive. The adhesive may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0079] In some embodiments, the negative electrode film layer further includes a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0080] In some embodiments, the negative electrode film layer also includes other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0081] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode sheet structure, and obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0082] In some embodiments, the battery is a secondary battery, which also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0083] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0084] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0085] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0086] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0087] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0088] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0089] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0090] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0091] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0092] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0093] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0094] Secondly, embodiments of this application propose a method for preparing a negative electrode active material, comprising the following steps:

[0095] Lithium difluorophosphate was mixed with a solvent to obtain a precursor solution;

[0096] The negative electrode active material is added to the precursor solution, stirred and reacted, and then dried to obtain the negative electrode active material.

[0097] The negative electrode active material includes a core and a coating layer that at least partially covers the core. The core includes a negative electrode active substance, and the coating layer includes lithium difluorophosphate.

[0098] By mixing lithium difluorophosphate with a solvent to obtain a precursor solution, and then using a liquid-phase method to form a coating layer on the surface of the negative electrode active material, lithium difluorophosphate can be effectively loaded onto the surface of the negative electrode active material. The coating layer has a simple composition, which can effectively avoid the generation of by-products, thereby improving the cycle performance of the battery. Moreover, the preparation method of the negative electrode active material is simple, which can improve production efficiency and reduce production costs.

[0099] In any embodiment, in the step of mixing lithium difluorophosphate with a solvent to obtain a precursor solution: the mass ratio of lithium difluorophosphate to the solvent is 1:(10~10). 5 Within this mass ratio range, lithium difluorophosphate to the solvent is beneficial for the dissolution and uniform dispersion of lithium difluorophosphate, resulting in a more uniform distribution of lithium difluorophosphate in the coating layer. It also facilitates the formation of a coating layer with an appropriate lithium difluorophosphate content on the surface of the negative electrode active material, thereby improving the battery's cycle performance. The mass ratio of lithium difluorophosphate to the solvent can be 1:10, 1:50, 1:100, 1:500, or 1:10. 3 1:5×10 3 1:10 4 1:5×10 4 Or 1:10 5 .

[0100] In any embodiment, in the step of mixing lithium difluorophosphate with a solvent to obtain a precursor solution, the solvent includes at least one selected from water, xylene, methanol, ethanol, acetonitrile, tetrahydrofuran, ethyl acetate, cyclohexane, butanone, acetone, and petroleum ether. Using at least one of the above solvents facilitates the dissolution and uniform dispersion of lithium difluorophosphate, resulting in a more uniform distribution of lithium difluorophosphate in the coating layer and improving the cycle performance of the battery. The solvent can be any one or any combination of multiple selected from water, xylene, methanol, ethanol, acetonitrile, tetrahydrofuran, ethyl acetate, cyclohexane, butanone, acetone, and petroleum ether.

[0101] In any embodiment, in the step of mixing lithium difluorophosphate with a solvent to obtain a precursor solution, the lithium difluorophosphate and the solvent are mixed under an inert atmosphere. Mixing lithium difluorophosphate and the solvent under an inert atmosphere can effectively avoid the generation of byproducts in the coating layer, which is beneficial to improving the cycle performance of the battery.

[0102] In any embodiment, the step of mixing lithium difluorophosphate with a solvent to obtain a precursor solution includes: mixing carrageenan with a solvent, then adding lithium difluorophosphate and mixing to obtain a precursor solution. By adding carrageenan, lithium difluorophosphate in the precursor solution can be maintained in a uniformly dispersed state. Simultaneously, during the liquid-phase coating process, carrageenan can form a surface with multiple oxygen-containing functional groups with the negative electrode active material. This results in more -OH and COOH functional groups on the surface and an increase in surface oxygen content. Through hydrogen bonding, lithium difluorophosphate is uniformly attached to the surface of the negative electrode active material, forming a coating layer. The resulting negative electrode active material is beneficial for further improving the cycle performance of the battery.

[0103] It should be noted that the type of carrageenan can be any one or any combination of κ-type, ι-type, λ-type, γ-type, ν-type, ξ-type, and μ-type; optionally, the carrageenan is at least one of κ-type carrageenan and ι-type carrageenan, which is more soluble in solvents.

[0104] In any embodiment, in the step of mixing carrageenan with a solvent and then adding lithium difluorophosphate to obtain a precursor solution: the mass ratio of carrageenan to the solvent is 1:(5×10⁻⁶). 3 ~5×10 6 The mass ratio of carrageenan to the solvent is within this range, which is beneficial for maintaining a better uniform dispersion of lithium difluorophosphate in the precursor solution, resulting in a more uniform distribution of lithium difluorophosphate in the coating layer, and thus improving the cycle performance of the battery; the mass ratio of carrageenan to the solvent can be 1:5×10. 3 1:1×10 4 1:5×10 4 1:1×10 5 1:5×10 5 1:1×10 6 Or 1:5×10 6 .

[0105] In any embodiment, in the step of adding the negative electrode active material to the precursor solution, stirring and reacting, and drying to obtain the negative electrode active material: the mass ratio of lithium difluorophosphate in the precursor solution to the negative electrode active material is (0.01-10):100. Within this range, the mass ratio of lithium difluorophosphate to the negative electrode active material allows lithium difluorophosphate to form a beneficial coating layer structure on the surface of the negative electrode active material, effectively reducing the erosion of the negative electrode active material surface by the electrolyte, suppressing side reactions, and improving the cycle performance of the battery. The mass ratio of lithium difluorophosphate to the negative electrode active material can be 0.01:100, 0.05:100, 0.1:100, 0.5:100, 1:100, 2:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, 9:100, or 10:100.

[0106] In any embodiment, in the step of adding the negative electrode active material to the precursor solution, stirring the reaction, and drying to obtain the negative electrode active material: the stirring reaction is carried out under an inert atmosphere. Conducting the stirring reaction under an inert atmosphere can effectively avoid the generation of byproducts in the coating layer, which is beneficial to improving the cycle performance of the battery.

[0107] In any embodiment, in the step of adding the negative electrode active material to the precursor solution, stirring the reaction, and drying to obtain the negative electrode active material: the stirring speed of the stirring reaction is 100 rpm to 2000 rpm. Stirring the reaction within this speed range is beneficial for forming a uniform coating layer on the surface of the negative electrode active material, which can improve the cycle performance of the battery; the stirring speed of the stirring reaction can be 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm, or 2000 rpm.

[0108] In any embodiment, in the step of adding the negative electrode active material to the precursor solution, stirring and reacting, and drying to obtain the negative electrode active material: the stirring reaction temperature is 25℃~80℃. Stirring within this temperature range is beneficial for forming a uniform coating layer on the surface of the negative electrode active material, which can improve the cycle performance of the battery; the stirring reaction temperature can be 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, or 80℃.

[0109] In any embodiment, in the step of adding the negative electrode active material to the precursor solution, stirring and reacting, and drying to obtain the negative electrode active material: the stirring reaction time is 0.1h to 24h. Stirring the reaction within this time range is beneficial for the formation of a coating layer on the surface of the negative electrode active material, which can improve the cycle performance of the battery; the stirring reaction time can be 0.1h, 0.5h, 1h, 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, or 24h.

[0110] In any embodiment, in the step of adding the negative electrode active material to the precursor solution, stirring and reacting, and drying to obtain the negative electrode active material: filtration is performed before drying. After stirring and reacting, filtration followed by drying helps to form a uniform coating layer on the surface of the negative electrode active material, which can improve the cycle performance of the battery.

[0111] In any embodiment, in the step of adding the negative electrode active material to the precursor solution, stirring and reacting, and drying to obtain the negative electrode active material: the drying temperature is 25℃~140℃. Drying within this temperature range is beneficial for forming a uniform coating layer on the surface of the negative electrode active material, which can improve the cycle performance of the battery; the drying temperature can be 25℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, or 140℃.

[0112] Thirdly, embodiments of this application propose a method for preparing a battery, comprising the following steps:

[0113] The negative electrode active material prepared by the negative electrode active material preparation method of the second aspect of this application is formulated into a negative electrode slurry;

[0114] The negative electrode slurry is coated onto at least one side of the negative electrode current collector to obtain a negative electrode sheet;

[0115] The negative electrode, positive electrode, and electrolyte are assembled to obtain a battery.

[0116] A battery made from a negative electrode active material prepared using the method of the second aspect of this application can improve the cycle performance of the battery.

[0117] Fourthly, embodiments of this application provide an electrical device, including a battery prepared by the method of the first aspect of this application or the third aspect of this application.

[0118] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0119] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0120] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0121] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0122] Example

[0123] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0124] Example 1

[0125] A method for preparing a negative electrode active material includes the following steps:

[0126] 0.1 mg of carrageenan was added to 500 g of solvent and mixed, and then 50 g of lithium difluorophosphate with a purity of 98% was added. The mixture was stirred evenly under an inert atmosphere to obtain a precursor solution. The solvent was a 90% ethanol solution obtained by mixing ethanol and deionized water at a volume ratio of 90:10.

[0127] 500g D v 50 μm of artificial graphite was added to a precursor solution, stirred and reacted under an inert atmosphere, filtered, dried at 80°C, and pulverized to obtain the negative electrode active material; the specific surface area of ​​the artificial graphite was 1.2 m². 2 / g, the stirring reaction temperature was 80℃, the stirring speed was 1000rpm, and the time was 24h; among which, the carrageenan was κ-type carrageenan.

[0128] The preparation methods of the negative electrode active materials in Examples 2 to 16 are the same as those in Example 1. The parameters that are different from those in Example 1 are set as shown in Table 1. In Examples 12 to 16, carrageenan is not added when preparing the precursor solution.

[0129] Comparative Example 1 uses the uncoated artificial graphite from Example 1 as the negative electrode active material; wherein, the D of the artificial graphite... v 50 has a diameter of 11 μm and a specific surface area of ​​1.2 m². 2 / g.

[0130] Table 1. Preparation method parameters and test results of negative electrode active materials in Examples 1 to 16 and Comparative Example 1

[0131]

[0132] Materials Testing

[0133] (1) Volume average particle size D v 50 tests

[0134] Equipment Model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer; Reference Standard Procedure: GB / T19077-2016 / ISO 13320:2009; Specific Test Procedure: Take an appropriate amount of the sample to be tested (the sample concentration should be 8-12% opacity), add 20mL of deionized water, and simultaneously incubate for 5 minutes (53KHz / 120W) to ensure complete dispersion of the sample. Then, measure the sample according to the GB / T19077-2016 / ISO 13320:2009 standard.

[0135] (2) Coating thickness test

[0136] The electrode sheet before cold pressing was cut into 6cm*6cm samples with scissors, and then polished with an IB-19500CP ion cross-section polisher to obtain a polished sample with a cut surface. Then, the sample was tested with a ZEISS sigma 300 instrument according to standard JY / T010-1996. Ten different locations were randomly selected in the test sample for testing, and the average value was taken to obtain the thickness of the coating layer.

[0137] (3) Phosphorus content test

[0138] The sample to be tested is attached to a copper sheet with insulating adhesive, and then the copper sheet is attached to a sample holder. After being purged with an air gun, the sample is placed in the sample chamber. The sample surface is irradiated with X-rays of a specific energy using AXIS SUPRA+ X-ray photoelectron spectroscopy. The excited photoelectrons have a fixed binding energy and are collected by a detector.

[0139] The negative electrode active materials prepared by the methods described in Examples 1 to 16 were subjected to the aforementioned material tests, and the test results are shown in Table 1. The negative electrode active material used in Examples 1 to 16 is D. v 50 is 11μm artificial graphite, with a particle size in the range of 10-12μm. After obtaining a negative electrode active material with a coating layer, D is performed. v The 50 test may have sampling bias, which could lead to variations in the measured D of the negative electrode active material. v 50 is less than 11μm.

[0141] Preparation of secondary batteries

[0142] The negative electrode active materials obtained in Examples 1 to 16 and the negative electrode active material of Comparative Example 1 were respectively prepared into secondary batteries as shown below.

[0143] [Preparation of the positive electrode sheet]

[0144] Lithium manganese oxide positive electrode active material, nickel cobalt manganese (NCM) ternary material, conductive agent carbon black, binder polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) were mixed in a mass ratio of 67.34:30:28.86:2.7:1.1 and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto the positive electrode current collector aluminum foil, and after drying, cold pressing and slitting, a positive electrode sheet was obtained.

[0145] [Preparation of the negative electrode sheet]

[0146] The above-mentioned negative electrode active material, conductive carbon black, binder vinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP) are added to deionized water in a mass ratio of 96.2:7:5:1.2 and mixed evenly to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated onto the negative electrode current collector copper foil once or multiple times, and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0147] [Preparation of Electrolyte]

[0148] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed evenly at a volume ratio of 3:7. Then, 12.5% ​​lithium hexafluorophosphate (LiPF6) lithium salt is added and dissolved in the mixed solvent and stirred evenly to obtain the electrolyte.

[0149] [Isolation membrane]

[0150] Polypropylene film is used as the separator.

[0151] Performance testing

[0152] The secondary batteries prepared with the negative electrode active materials obtained in Examples 1 to 16 and the negative electrode active material of Comparative Example 1 were subjected to performance tests. The test results are shown in Table 1.

[0153] Secondary battery capacity retention test

[0154] At 25°C, the secondary battery is charged to 4.3V at a constant current of 1 / 3C, then charged to 0.05C at a constant voltage of 4.3V, left to stand for 5 minutes, and then discharged to 2.8V at 1 / 3C. The resulting capacity is recorded as the initial capacity C0. The above steps are repeated for the same battery, and the discharge capacity Cn of the battery after the nth cycle is recorded. The capacity retention rate Pn = Cn / C0 * 100%; where n is 100.

[0155] As shown in Table 1, compared with Comparative Example 1, the secondary batteries prepared using the negative electrode active materials obtained in Examples 1 to 16 have a higher capacity retention rate after 100 cycles at 25°C. This indicates that coating the surface of the negative electrode active material with a coating layer containing lithium difluorophosphate can improve the cycle performance of the battery. As can be seen from Examples 1 to 3, Examples 8 and 9, and Examples 12 to 16, adding carrageenan to form a precursor solution in the preparation method of the negative electrode active material can further improve the cycle performance of the battery.

[0156] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A battery, characterized by, The positive electrode sheet, the negative electrode sheet, and an electrolyte solution are included; the negative electrode sheet includes a negative electrode active material, the negative electrode active material includes a core and a coating layer at least partially coating the core, the core includes a negative electrode active substance, the coating layer includes lithium difluorophosphate, and the mass percentage of phosphorus in the coating layer is 0.3% to 10%.

2. The battery of claim 1, wherein, The thickness of the coating layer is 2nm to 60nm.

3. The battery of claim 1 or 2, wherein the electrolyte is a mixture of the first and second electrolytes. The negative electrode active substance includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, and silicon-based material.

4. The battery according to any one of claims 1 to 3, wherein D of the negative active material v 50 is 10 nm to 25 μm.

5. The battery according to any one of claims 1 to 4, wherein The coating layer further includes carrageenan.

6. The battery according to any one of claims 1 to 5, wherein The molar concentration of lithium salt in the electrolyte solution is 0.6mol / L to 2mol / L.

7. The battery according to any one of claims 1 to 6, wherein The lithium salt in the electrolyte solution includes at least one of lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluoro sulfonimide, and lithium bis(trifluoromethylsulfonyl)imide.

8. A method for producing a negative electrode active material, characterized by, The method includes the following steps: Lithium difluorophosphate is mixed with a solvent to obtain a precursor solution; A negative electrode active substance is added to the precursor solution, stirred and reacted, and dried to obtain a negative electrode active material; The negative electrode active material includes a core and a coating layer at least partially coating the core, the core includes a negative electrode active substance, and the coating layer includes lithium difluorophosphate.

9. The method for producing a negative electrode active material according to claim 8, wherein In the step of mixing lithium difluorophosphate with a solvent to obtain a precursor solution: The mass ratio of lithium difluorophosphate to the solvent is 1 : (10 ~ 10 5 ); and / or, The solvent includes at least one of water, dimethylbenzene, methanol, ethanol, acetonitrile, tetrahydrofuran, ethyl acetate, cyclohexane, butanone, acetone, and petroleum ether; and / or, Lithium difluorophosphate is mixed with a solvent in an inert atmosphere.

10. The method for producing a negative electrode active material according to claim 8 or 9, wherein The step of mixing lithium difluorophosphate with a solvent to obtain a precursor solution includes: Carrageenan is mixed with a solvent, and then lithium difluorophosphate is added and mixed to obtain a precursor solution.

11. The method for producing a negative electrode active material according to claim 10, wherein In the step of mixing carrageenan with a solvent, and then adding lithium difluorophosphate and mixing to obtain a precursor solution: The mass ratio of carrageenan to the solvent is 1 : (5 x 10 3 ~ 5 x 10 6 ).

12. The method for preparing the negative electrode active material according to any one of claims 8 to 11, in the step of adding a negative electrode active substance to the precursor solution, stirring and reacting, and drying to obtain a negative electrode active material: The mass ratio of lithium difluorophosphate in the precursor solution to the negative electrode active substance is (0.01 to 10):

100.

13. The method for producing a negative electrode active material according to any one of claims 8 to 12, characterized by, In the step of adding a negative electrode active substance to the precursor solution, stirring and reacting, and drying to obtain a negative electrode active material: The stirring and reacting is performed in an inert atmosphere; and / or, The stirring speed of the stirring and reacting is 100rpm to 2000rpm; and / or, The temperature of the stirring and reacting is 25°C to 80°C; and / or, The time of the stirring and reacting is 0.1h to 24h.

14. The method for producing a negative electrode active material according to any one of claims 8 to 13, characterized by, In the step of adding a negative electrode active substance to the precursor solution, stirring and reacting, and drying to obtain a negative electrode active material: The filtering is performed before the drying; and / or, The temperature of the drying is 25°C to 140°C.

15. A method for preparing a battery, characterized in that, The method includes the following steps: A negative electrode active material prepared by the method for preparing the negative electrode active material according to any one of claims 8 to 14 is formulated into a negative electrode slurry; The negative electrode slurry is coated on at least one side of a negative electrode current collector to obtain a negative electrode sheet. Assembling the negative electrode sheet, the positive electrode sheet and the electrolyte to obtain a battery.

16. An electrical device, comprising: A battery comprising the battery according to any one of claims 1 to 7 or the battery prepared according to the method of claim 15.

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