Secondary battery, battery module, battery pack and power-consuming device thereof

Abstract

The present application provides a secondary battery, a battery module, a battery pack and an electrical device thereof. The secondary battery comprises a negative electrode plate and an electrolyte, wherein the negative electrode plate contains a negative electrode active material, wherein the negative electrode active material comprises a core and a coating layer containing an antimony element disposed on the surface of the core; the electrolyte contains a lithium salt and a fluorine-containing additive, wherein the fluorine-containing additive is a fluorine-containing ester monocyclic compound; wherein the molar ratio of the antimony element to the fluorine-containing additive is 1:20 to 10:1, and optionally 0.9:10 to 6:10. In the present application, by using the above-mentioned secondary battery, it is helpful to form a SEI film with a high LiF content on the negative electrode plate, which can effectively prevent the co-embedding of solvent molecules, avoid the damage to the negative electrode material caused by the co-embedding of solvent molecules, reduce the decomposition of the solvent in the electrolyte, and improve the cycle performance and extend the life of the secondary battery.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a secondary battery, a battery module, a battery pack and an electrical device thereof. Background Art

[0002] In recent years, with the increasing demand for clean energy, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, military equipment, aerospace and other fields. As the application areas of secondary batteries have been greatly expanded, higher requirements have been placed on their performance.

[0003] In order to further improve the battery life and service life of secondary batteries and enhance user experience, how to improve the cycle performance and service life of secondary batteries has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] Technical problem to be solved by this application

[0005] The present application is made in view of the above-mentioned problems, and its purpose is to provide a secondary battery, a battery module, a battery pack and an electrical device thereof with long battery life and service life.

[0006] Technical solutions to solve problems

[0007] In order to achieve the above objectives, the present application provides a secondary battery, a battery module, a battery pack and an electrical device thereof.

[0008] Secondary battery

[0009] The first aspect of the present application provides a secondary battery, which includes a negative electrode plate and an electrolyte; the negative electrode plate contains a negative electrode active material, and the negative electrode active material includes a core and a coating layer containing antimony element arranged on the surface of the core; the electrolyte contains a lithium salt and a fluorine-containing additive, and the fluorine-containing additive is a fluorine-containing ester monocyclic compound; wherein the molar ratio of the antimony element to the fluorine-containing additive is 1:20 to 10:1, and optionally 0.9:10 to 6:10.

[0010] In the present application, a coating layer containing antimony elements is arranged on the surface of the core, and it is used as a negative electrode active material, and a negative electrode plate containing the negative electrode active material is applied to an electrolyte containing a lithium salt and a fluorine-containing additive. During the charging process of the secondary battery, the lithium salt in the electrolyte will ionize free lithium ions, which will react with the antimony elements in the negative electrode plate to form a film layer containing Li3Sb. When the solvent molecules in the electrolyte and the fluorine-containing ester monocyclic compounds diffuse to the surface of the negative electrode plate at the same time, the fluorine-containing ester monocyclic compounds have a stronger binding energy with the Li3Sb on the surface of the negative electrode plate relative to other solvent molecules in the electrolyte, and will preferentially adsorb on the surface of the Li3Sb film layer, and promote the decomposition of the fluorine-containing additive to generate a stable solid electrolyte interface film (SEI film) whose main component is LiF. LiF is an inorganic compound, and has better stability than other organic components in the SEI film. When the content of LiF in the SEI film is high, it can improve the film strength, resist the cracking of the SEI film caused by expansion, effectively prevent the co-embedding of solvent molecules, avoid the damage to the electrode material caused by the co-embedding of solvent molecules, and at the same time, reduce the decomposition of the electrolyte solvent. Therefore, it is beneficial to improve the cycle performance of the secondary battery and extend the service life of the secondary battery.

[0011] In this application, a fluorinated ester monocyclic compound is selected as the fluorinated additive. Compared with fluorinated ester compounds with a large number of rings, fluorinated ester monocyclic compounds have lower steric hindrance and stronger binding energy with Li3Sb, which is conducive to being adsorbed on the surface of the negative electrode before solvent molecules, and decomposing to form a SEI film with higher stability.

[0012] The present application also limits the molar ratio of the antimony element to the fluorine-containing additive in the secondary battery, thereby ensuring that a good adsorption relationship between Li3Sb and the fluorine-containing additive is formed without affecting other components of the battery system, thereby preventing problems such as excessive solvent consumption, excessive loss of active ions, and uneven SEI film coating.

[0013] In any embodiment, the coating layer containing antimony element contains at least one of antimony element, antimony oxide and antimony trifluoride, and can be antimony element. In the present application, by using at least one of antimony element, antimony oxide and antimony trifluoride as the coating layer of the negative electrode active material, it can react with lithium ions in the electrolyte to generate a film layer containing Li3Sb, and further adsorb fluorine-containing additives to promote its decomposition to form a SEI film with a high LiF content. Taking Sb2O3 as an example, the reaction formula of Sb2O3 with lithium ions in the electrolyte is:

[0014] Sb2O3+6Li + →2Sb 3+ +3Li2O,

[0015] 3Li ++Sb→Li3Sb,

[0016] SbF3+3Li + →3LiF+Sb 3+ .

[0017] Thus, the co-embedding of solvent molecules can be effectively prevented, thereby avoiding damage to the electrode material caused by the co-embedding of solvent molecules, improving the cycle performance of the secondary battery and extending the service life of the secondary battery.

[0018] In any embodiment, the coating layer has a thickness of 5 nm to 1000 nm, and optionally 20 nm to 400 nm. The present application can improve the cycle performance of the secondary battery and extend the service life of the secondary battery without affecting the capacity by controlling the thickness of the coating layer within a suitable range.

[0019] In any embodiment, based on the total mass of the negative electrode active material, the mass percentage of the coating layer is 0.5% to 20%, and optionally 1% to 10%. Therefore, by controlling the mass percentage of the coating layer within a suitable range, the present application can ensure that a uniform and structurally stable SEI film is formed on the surface of the negative electrode plate, which has a good protective effect on the negative electrode material; at the same time, it can also ensure that the consumption of active lithium is low, ensure the battery capacity, thereby ensuring the improvement of the cycle performance of the secondary battery and extending the service life of the secondary battery.

[0020] In any embodiment, the fluorine-containing additive includes at least one of fluoroethylene carbonate, phenyl trifluoroacetate, and allyl tris (2,2,2-trifluoroethyl) carbonate, optionally fluoroethylene carbonate or phenyl trifluoroacetate. When the above-mentioned fluorine-containing additive is selected, the binding energy of the above-mentioned substance with Li3Sb is stronger than that of other solvent molecules, and the attraction between them is also stronger, so it can be preferentially adsorbed on the surface of the Li3Sb film layer, and decomposed to generate a SEI film with a high LiF content and stability. LiF is an inorganic compound, and has better stability than other organic components in SEI films. When the content of LiF in the SEI film is high, the film strength can be improved, the cracking of the SEI film caused by the expansion can be resisted, and the co-embedding of solvent molecules can be effectively prevented, and the damage to the electrode material caused by the co-embedding of solvent molecules can be avoided. Therefore, the present application can generate a SEI film with a high LiF content and stability by selecting the fluorine-containing additive in the above range, which can effectively prevent the co-embedding of solvent molecules and avoid the damage to the electrode material caused by the co-embedding of solvent molecules, thereby improving the cycle performance and service life of the secondary battery.

[0021] In any embodiment, based on the total mass of the electrolyte, the mass percentage of the fluorine-containing additive is 0.5% to 20%, and optionally 2% to 10%. The present application controls the mass percentage of the fluorine-containing additive within a suitable range. On the one hand, it can ensure low consumption of solvent for the formation of the SEI film, prevent the decomposition of the solvent, ensure the battery capacity, and meet the use of the whole life cycle; at the same time, it can also ensure that the solvent in the electrolyte is in a suitable proportion, and ensure that the electrolyte system, solubility, viscosity and other conditions are in a good state, thereby improving the cycle performance of the secondary battery and extending the service life of the secondary battery.

[0022] In any embodiment, the molar concentration of the lithium salt in the electrolyte is 0.7M to 1.5M.

[0023] In any embodiment, the core contains at least one of graphite, hard carbon, soft carbon, lithium titanate, tin-based materials, nickel-based materials, and alloy materials.

[0024] The second aspect of the present application provides a battery module, comprising the secondary battery of the first aspect of the present application, wherein the battery module has good cycle performance and a long service life.

[0025] The third aspect of the present application provides a battery pack, comprising the battery module of the second aspect of the present application. The battery pack has good cycle performance and a long service life.

[0026] The fourth aspect of the present application provides an electric device, comprising at least one selected from the secondary battery of the first aspect of the present application, the battery module of the second aspect of the present application, or the battery pack of the third aspect of the present application. The electric device has good cycle performance and a long service life.

[0027] Beneficial Effects

[0028] The present application provides a secondary battery, the secondary battery comprising a negative electrode plate and an electrolyte, the negative electrode plate contains a negative electrode active material, the inner core surface of the negative electrode active material is provided with a coating layer containing antimony element; the electrolyte contains a lithium salt and a fluorine-containing additive, the fluorine-containing additive is a fluorine-containing ester monocyclic compound; wherein the molar ratio of the antimony element to the fluorine-containing additive is 1:20 to 10:1, optionally 0.9:10 to 6:10. In the present application, by using the above-mentioned secondary battery, a film layer containing Li3Sb can be generated on the surface of the negative electrode plate after charging, and the fluorine-containing additive in the electrolyte is preferentially adsorbed, decomposed and formed into a SEI film with a high content of LiF, which can effectively prevent the co-embedding of solvent molecules, avoid the damage to the negative electrode material caused by the co-embedding of solvent molecules, reduce the decomposition of the solvent in the electrolyte, and improve the cycle performance and extend the life of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of a negative electrode active material according to an embodiment of the present application.

[0030] Figure 2 These are the cycle performance test results of secondary batteries made from the negative electrode active materials obtained in Example 1 and Comparative Example 1 of the present application.

[0031] Figure 3 is a schematic diagram of a secondary battery according to one embodiment of the present application.

[0032] Figure 4 yes Figure 3 An exploded view of a secondary battery according to an embodiment of the present application is shown.

[0033] Figure 5 is a schematic diagram of a battery module according to an embodiment of the present application.

[0034] Figure 6 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0035] Figure 7 yes Figure 6 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0036] Figure 8 Schematic diagram of an electrical device using a secondary battery according to an embodiment of the present application as a power source.

[0037] Description of reference numerals:

[0038] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0039] Below, the embodiments of the secondary battery, battery module, battery pack and power device of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0040] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0042] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0043] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0044] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0045] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0046] The inventors have found through research that secondary batteries, especially at the position of the negative electrode, have the problem of co-embedding of solvent molecules and excessive decomposition of solvents, which is an important factor restricting the cycle performance and service life of secondary batteries. The inventors of this application have effectively improved the cycle performance of secondary batteries and extended their service life by setting a coating layer containing antimony elements on the surface of the core of the negative electrode active material and adding special additives to the electrolyte.

[0047] Based on this, the first embodiment of the present application provides a secondary battery, which includes a negative electrode plate and an electrolyte; the negative electrode plate contains a negative electrode active material, and the negative electrode active material includes a core and a coating layer containing antimony element arranged on the surface of the core; the electrolyte contains a lithium salt and a fluorine-containing additive, and the fluorine-containing additive is a fluorine-containing ester monocyclic compound; wherein the molar ratio of the antimony element to the fluorine-containing additive is 1:20 to 10:1, and optionally 0.9:10 to 6:10.

[0048] like Figure 1 As shown, in the present application, a coating layer containing antimony elements is arranged on the surface of the core, and it is used as a negative electrode active material, and the negative electrode plate containing the negative electrode active material is applied to an electrolyte containing a lithium salt and a fluorine-containing additive. During the charging process of the secondary battery, the lithium salt in the electrolyte will ionize free lithium ions, which will react with the antimony elements in the negative electrode plate to form a film layer containing Li3Sb. When the solvent molecules in the electrolyte and the fluorine-containing ester monocyclic compounds diffuse to the surface of the negative electrode plate at the same time, the fluorine-containing ester monocyclic compounds have a stronger binding energy with the Li3Sb on the surface of the negative electrode plate relative to other solvent molecules in the electrolyte, and the attraction between them is also stronger, and they will preferentially adsorb on the surface of the Li3Sb film layer, and promote the decomposition of the fluorine-containing additive to generate a stable solid electrolyte interface film (SEI film) whose main component is LiF. In the SEI film of the present application, LiF is an inorganic compound, which has better stability than the organic components in other SEI films. When the LiF content in the SEI film is high, it can improve the film strength, resist the cracking of the SEI film caused by expansion, effectively prevent the co-embedding of solvent molecules, avoid the damage to the electrode material caused by the co-embedding of solvent molecules, and at the same time, reduce the decomposition of the electrolyte solvent, improve the cycle performance of the secondary battery, and extend the service life of the secondary battery. Figure 2 .

[0049] In the present application, a fluorinated ester monocyclic compound is selected as the fluorinated additive. Compared with a fluorinated ester compound with a larger number of rings, the fluorinated ester monocyclic compound has lower steric hindrance and stronger binding energy with Li3Sb. The binding energy refers to the free energy of the binding reaction of two substances. The smaller the binding energy value, the easier it is for the two substances to bind.

[0050] The secondary battery provided in the present application can satisfy the above-mentioned molar ratio of antimony element to the fluorine-containing additive in the initial state, especially within 10 cycles of charge and discharge. After 1000 cycles of charge and discharge, the molar ratio of the two can still be maintained in the range of 1:5 to 40:1, optionally 1:2.5 to 4:1, because the initial film formation and the cycle process will consume the fluorine-containing additive. By limiting the molar ratio of the antimony element and the fluorine-containing additive in the secondary battery, it is possible to ensure that a good adsorption relationship between Li3Sb and the fluorine-containing additive is formed without affecting other components of the battery system, thereby preventing problems such as excessive consumption of solvent, excessive loss of active ions, and uneven SEI film coating.

[0051] In addition, in the present application, the coating layer on the surface of the negative electrode active material is preferably generated in situ, and the coating layer occupies a small volume in the negative electrode active material. Therefore, the secondary battery provided in the present application is suitable for situations where space is limited and where high requirements are placed on weight and energy density, but is not limited thereto.

[0052] In the present application, the content of antimony element and the content of fluorine-containing additive can be tested by methods known in the art. As an example, the content of antimony element can be tested by inductively coupled plasma spectrometer (ICP), such as ICP-3000 of Tianrui Company; the content of fluorine-containing additive can be obtained by GC test, such as GC-2014C of Shimadzu Company. By calculation, the ratio of the two can be obtained.

[0053] In some embodiments, the coating layer containing antimony element contains at least one of antimony element, antimony oxide and antimony trifluoride, and may be antimony element.

[0054] In the present application, by using at least one of antimony, antimony oxide and antimony trifluoride as the coating layer of the negative electrode active material, it can react with lithium ions in the electrolyte to generate a film layer containing Li3Sb, and further adsorb fluorine-containing additives to promote their decomposition to form a SEI film with a high LiF content. Taking Sb2O3 as an example, the reaction formula of Sb2O3 with lithium ions in the electrolyte is:

[0055] Sb2O3+6Li + →2Sb 3++3Li2O,

[0056] 3Li + +Sb→Li3Sb,

[0057] SbF3+3Li + →3LiF+Sb 3+ .

[0058] Thus, the co-embedding of solvent molecules can be effectively prevented, thereby avoiding damage to the electrode material caused by the co-embedding of solvent molecules, improving the cycle performance of the secondary battery and extending the service life of the secondary battery.

[0059] In some embodiments, the coating layer has a thickness of 5 nm to 1000 nm, and optionally 20 nm to 400 nm. The present application can improve the cycle performance of the secondary battery and extend the service life of the secondary battery without affecting the capacity by controlling the thickness of the coating layer within a suitable range.

[0060] In the present application, the thickness of the coating layer can be tested by methods known in the art. For example, a transmission electron microscope (TEM) can be used for characterization testing, such as JEM-2100F from JEOL.

[0061] In some embodiments, based on the total mass of the negative electrode active material, the mass percentage of the coating layer is 0.5% to 20%, or alternatively 1% to 10%.

[0062] Therefore, the present application controls the mass percentage of the coating layer within an appropriate range. On the one hand, it can ensure that a uniform and structurally stable SEI film is formed on the surface of the negative electrode plate, which has a good protective effect on the negative electrode material; at the same time, it can also ensure that the consumption of active lithium is low and the battery capacity is guaranteed, thereby improving the cycle performance of the secondary battery and extending the service life of the secondary battery.

[0063] In some embodiments, the fluorine-containing additive includes at least one of fluoroethylene carbonate, phenyl trifluoroacetate, and allyl tris(2,2,2-trifluoroethyl) carbonate, and may be fluoroethylene carbonate or phenyl trifluoroacetate.

[0064] When the above-mentioned fluorine-containing additive is selected, the binding energy of the above-mentioned substance with Li3Sb is stronger than that of other solvent molecules, and the attraction between them is also stronger, so it can be preferentially adsorbed on the surface of the Li3Sb film layer, and decomposed to generate a SEI film with a high and stable LiF content. LiF is an inorganic compound, and has better stability than other organic components in SEI films. When the content of LiF in the SEI film is high, it can improve the film strength, resist expansion and cause cracking of the SEI film, effectively prevent the co-embedding of solvent molecules, and avoid damage to the electrode material caused by the co-embedding of solvent molecules. Thus, the present application can generate a SEI film with a high and stable LiF content by selecting the fluorine-containing additive in the above range, which can effectively prevent the co-embedding of solvent molecules, avoid damage to the electrode material caused by the co-embedding of solvent molecules, and thus improve the cycle performance and service life of the secondary battery.

[0065] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the fluorine-containing additive is 0.5% to 20%, optionally 2% to 10%. In the secondary battery provided in the present application, in the initial state, especially within 10 cycles of charge and discharge, the fluorine-containing additive can meet the above mass percentage range.

[0066] Therefore, the present application controls the mass percentage of fluorine-containing additives within an appropriate range. On the one hand, it can ensure low consumption of solvent for the formation of SEI film, prevent decomposition of solvent, ensure battery capacity, and meet the use of the entire life cycle; at the same time, it can also ensure that the solvent in the electrolyte is in an appropriate proportion, and ensure that the electrolyte system, solubility, viscosity and other conditions are in a good state, thereby improving the cycle performance of the secondary battery and extending the service life of the secondary battery.

[0067] In some embodiments, the molar concentration of the lithium salt in the electrolyte is 0.7M to 1.5M.

[0068] In some embodiments, the core may be a negative electrode active material for a battery known in the art. As an example, the core may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, tin-based materials, nickel-based materials, lithium titanate, and alloy materials. The alloy material may be selected from silicon-based materials, and the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used as the core. These materials may be used alone as the core, or two or more may be used in combination as the core.

[0069] In some embodiments, the negative electrode sheet further includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes the negative electrode active material. As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0070] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material 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 material substrate (such as a substrate of PP, PET, PBT, PS, PE, etc.).

[0071] In some embodiments, the negative electrode film layer may further include a binder. The binder 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).

[0072] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0073] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0074] In some embodiments, the negative electrode plate can be prepared by the following method:

[0075] A precursor containing antimony element and a core are provided, and the precursor containing antimony element and the core are mixed and calcined to obtain a negative electrode active material, wherein the negative electrode active material includes a core and a coating layer containing antimony element arranged on the surface of the core; the above components for preparing a negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on a negative electrode collector, and after drying, cold pressing and other processes, a negative electrode sheet can be obtained.

[0076] In the present application, the negative electrode sheet preparation method of the present application can be simply and easily prepared, and has the advantages of low energy consumption and low cost; in addition, through the above method, the antimony element-containing precursor can be evenly coated on the surface of the inner core, thereby obtaining a negative electrode sheet that meets the conditions of the present application.

[0077] In some embodiments, the precursor containing the antimony element includes an antimony salt, and the antimony salt includes at least one of antimony trichloride, antimony nitrate, antimony sulfate, antimony acetate, poly(antimony glycol), tri(dimethylamino)antimony, triphenylantimony, antimony butoxide, triphenylantimony dichloride, antimony (III) ethoxide, triphenylantimony dibromide, and fluoroantimonic acid hexahydrate; the coating layer containing the antimony element includes at least one of antimony element, antimony oxide and antimony trifluoride; the inner core contains at least one of graphite, hard carbon, soft carbon, lithium titanate, tin-based materials, nickel-based materials, and alloy materials.

[0078] In some embodiments, the mixing step comprises:

[0079] The antimony element-containing precursor and the core are mixed in an aqueous solution, hydrochloric acid is added to maintain the pH value of the solution at 2-4, the mixture is stirred until the mixture is uniform, and the solvent is evaporated.

[0080] In the present application, by controlling the pH range in the mixing step, the hydrolysis of the antimony-containing precursor can be effectively suppressed. When the pH value is higher than 4, the antimony-containing precursor is easily hydrolyzed, and the antimony-containing precursor cannot be uniformly coated on the surface of the core; when the pH value is lower than 2, the reaction conditions are too acidic, which will corrode the reaction container. Thus, a uniform coating layer containing antimony can be formed on the surface of the core.

[0081] In some embodiments, the calcining step comprises:

[0082] The sintering temperature is controlled to be 400°C to 800°C, the sintering time is 4h to 12h, and it is carried out in an inert gas atmosphere.

[0083] In this application, in the calcination step, when the sintering temperature is low and the sintering time is short, the reduction time will be too long and the reduction effect will be poor; when the sintering temperature is high and the sintering time is long, it will lead to aging, causing the coating layers of adjacent particles to melt together, resulting in problems such as particle agglomeration; at the same time, calcination needs to be carried out in an inert gas atmosphere to protect the core from being oxidized and consumed. Therefore, by limiting the sintering temperature, sintering time and gas atmosphere in the calcination step, a negative electrode active material that meets the conditions of this application can be obtained.

[0084] In addition, other parts of the secondary battery, the battery module, the battery pack, and the electric device of the present application are described below with reference to the drawings as appropriate.

[0085] In one embodiment of the present application, a secondary battery is provided.

[0086] Normally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charge and discharge process, active ions are embedded and removed back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through. The following is a detailed description of the various components of the secondary battery.

[0087] [Positive electrode]

[0088] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.

[0089] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0090] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. 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 material substrate (such as a substrate of polypropylene (PP), PET, PBT, polystyrene (PS), polyethylene (PE), etc.).

[0091] In some embodiments, the positive electrode active material may adopt a positive electrode active material for a battery that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds, etc. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0092] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0093] In some embodiments, the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0094] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0095] [Negative electrode]

[0096] The negative electrode plate is described above.

[0097] [Electrolytes]

[0098] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0099] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0100] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0101] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0102] In some embodiments, the electrolyte includes additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc. In the present application, the electrolyte includes a fluorine-containing additive that is a fluorine-containing ester monocyclic compound.

[0103] [Isolation film]

[0104] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0105] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0106] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0107] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0108] In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0109] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape. Figure 3 The secondary battery 5 is a square structure as an example.

[0110] In some embodiments, reference Figure 4 , the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0111] In some embodiments, secondary batteries may be assembled into a battery module. The number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0112] Figure 5 4 is an example of a battery module. Figure 5 In the battery module 4, the plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

[0113] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0114] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0115] Figure 6 and Figure 7 1 is a battery pack 1 as an example. Figure 6 and Figure 7The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0116] In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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., but are not limited thereto.

[0117] As the electrical device, a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.

[0118] Figure 8 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the power consumption device for the secondary battery, a battery pack or a battery module can be used.

[0119] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.

[0120] Example

[0121] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0122] Example 1

[0123] (1) Preparation of negative electrode active materials

[0124] After 95g of graphite and 5g of SbCl3 were uniformly mixed by a liquid phase method, the sample was placed in an Ar / H2 (5% H2) atmosphere and calcined at 500°C for 6h to obtain a negative electrode active material. The physical properties of the negative electrode active material are shown in Table 1 below.

[0125] (2) Preparation of negative electrode sheet

[0126] The above-mentioned negative electrode active material, conductive agent carbon black, binder styrene butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC) are dispersed in deionized water, and fully stirred and mixed to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector copper foil, and dried and cold pressed to obtain a negative electrode sheet.

[0127] (3) Preparation of secondary batteries

[0128] Lithium manganese phosphate as a positive electrode material, acetylene black as a conductive agent and polyvinylidene fluoride (PVDF) as a binder are fully stirred and mixed in an N-methylpyrrolidone solvent system at a weight ratio of 94:3:3, and then coated on an aluminum foil, dried, and cold pressed to obtain a positive electrode sheet.

[0129] A porous polymer film made of polyethylene (PE) is used as the isolation membrane.

[0130] The positive electrode sheet, the separator and the negative electrode sheet are overlapped in sequence, the separator is placed between the positive and negative electrodes to play an isolating role, and then wound to obtain a bare battery cell.

[0131] The electrolyte is fluoroethylene carbonate (FEC) / (ethylene carbonate (EC)+diethyl carbonate (DEC)) (mass ratio 5:95), and the volume ratio of EC to DEC is 1:1.

[0132] The bare battery cell is placed in an outer package, injected with the above electrolyte and packaged to obtain a secondary battery.

[0133] Example 2-3

[0134] The secondary battery of Example 2-3 was prepared in the same manner as Example 1, except that the thickness of the coating layer of the negative electrode active material was changed by adjusting the input amount of the precursor containing the antimony element in the raw material as shown in Table 1 below.

[0135] Example 4

[0136] The secondary battery of Example 4 was prepared in the same manner as Example 1, except that the amount of the antimony-containing precursor in the raw material was adjusted to change the coating thickness of the negative electrode active material and the amount of FEC added was adjusted as shown in Table 1 below.

[0137] Example 5

[0138] A secondary battery of Example 5 was prepared in the same manner as in Example 1, except that FEC was replaced with phenyl trifluoroacetate as shown in Table 1 below.

[0139] Embodiment 6-7

[0140] Secondary batteries of Examples 6-7 were prepared in the same manner as in Example 1, except that FEC was replaced with phenyl trifluoroacetate and the addition amount was adjusted as shown in Table 1 below.

[0141] Example 8

[0142] The secondary battery of Example 8 was prepared in the same manner as Example 1, except that the amount of the antimony-containing precursor in the raw material was adjusted to change the coating thickness of the negative electrode active material and the amount of FEC added was adjusted as shown in Table 1 below.

[0143] Example 9

[0144] (1) Preparation of negative electrode active materials

[0145] 95 g of graphite and 5 g of Sb2O3 were put into a ball mill together, and ball milled at a speed of 400 r / min for 10 h to obtain the negative electrode active material.

[0146] (2) Preparation of negative electrode sheet

[0147] The above-mentioned negative electrode active material, conductive agent carbon black, binder styrene butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC) are dispersed in deionized water, and fully stirred and mixed to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector copper foil, and dried and cold pressed to obtain a negative electrode sheet.

[0148] (3) Preparation of secondary batteries

[0149] Lithium manganese phosphate as a positive electrode material, acetylene black as a conductive agent and polyvinylidene fluoride (PVDF) as a binder are fully stirred and mixed in an N-methylpyrrolidone solvent system at a weight ratio of 94:3:3, and then coated on an aluminum foil, dried, and cold pressed to obtain a positive electrode sheet.

[0150] A porous polymer film made of polyethylene (PE) is used as the isolation membrane.

[0151] The positive electrode sheet, the separator and the negative electrode sheet are overlapped in sequence, the separator is placed between the positive and negative electrodes to play an isolating role, and then wound to obtain a bare battery cell.

[0152] The electrolyte is fluoroethylene carbonate (FEC) / (ethylene carbonate (EC)+diethyl carbonate (DEC)) (mass ratio 5:95), and the volume ratio of EC to DEC is 1:1.

[0153] The bare battery cell is placed in an outer package, injected with the above electrolyte and packaged to obtain a secondary battery.

[0154] Example 10

[0155] A secondary battery of Example 10 was prepared in the same manner as in Example 9 except that Sb 2 O 3 charged in the raw material was adjusted to SbF 3 as shown in Table 1 below.

[0156] Comparative Example 1

[0157] The secondary battery of Comparative Example 1 was prepared in the same manner as in Example 1, except that the precursor containing antimony element was not added during the preparation of the negative electrode active material as shown in Table 1 below.

[0158] Comparative Example 2

[0159] A secondary battery of Comparative Example 2 was prepared in the same manner as in Example 1, except that FEC was not added to the electrolyte as shown in Table 1 below.

[0160] Comparative Example 3

[0161] A secondary battery of Comparative Example 3 was prepared in the same manner as in Example 1, except that the addition amount of FEC was adjusted as shown in Table 1 below.

[0162] Comparative Example 4

[0163] A secondary battery of Comparative Example 4 was prepared in the same manner as in Example 1, except that FEC was replaced with 2-fluoro-1-naphthol as shown in Table 1 below.

[0164] Comparative Example 5

[0165] The secondary battery of Comparative Example 5 was prepared in the same manner as Example 1, except that the coating thickness of the negative electrode active material was changed by adjusting the input amount of the antimony-containing precursor in the raw material and adjusting the addition amount of FEC as shown in Table 1 below.

[0166] Next, a method for testing the secondary battery will be described.

[0167] (1) Initial capacity test

[0168] The secondary battery prepared above was charged to 4.2V at 0.33C in a constant temperature environment of 25°C, then charged at a constant voltage at 4.2V to a current ≤ 0.05C, allowed to stand for 5 minutes, and then discharged to 2.8V at 0.33C to obtain the initial capacity of the secondary battery.

[0169] (2) Capacity retention test

[0170] The secondary battery prepared as above was charged to 4.2V at 1C in a constant temperature environment of 60°C, then charged at a constant voltage at 4.2V to a current ≤0.05C, allowed to stand for 5 minutes, and then discharged to 2.8V at 1C. This cycle was repeated for 500 cycles. The capacity after 500 cycles obtained by the test was divided by the initial capacity to obtain the capacity retention rate.

[0171]

[0172] Table 2: Performance test results of Examples 1 to 10 and Comparative Examples 1 to 5

[0173]

[0174] It can be seen from Examples 1-10 in Table 2 above that when the type, thickness, and mass percentage of the antimony element in the negative electrode active material coating layer in the secondary battery, the type and mass percentage of the fluorine-containing additive in the electrolyte, and the molar ratio of the particles containing antimony elements to the fluorine-containing additive are all within the scope of the present application, the secondary battery of the present application has good cycle performance and service life.

[0175] From the comparison of Example 1 and Comparative Examples 1-2 in Table 2 above, it can be seen that the coating layer containing antimony elements and the fluorine-containing additives are indispensable. When conventional negative electrode active materials are directly selected without antimony coating, the SEI film formed on its surface after the secondary battery is charged will contain a large amount of organic components, resulting in insufficient stability of the SEI film. At the same time, it will be destroyed due to the expansion of the anode, and the active lithium will be continuously consumed to rebuild, resulting in poor cycle performance of the secondary battery; when no fluorine-containing additives are added to the electrolyte, after the secondary battery is charged, the SEI film generated on the surface of the negative electrode material will absorb the solvent molecules in the electrolyte, resulting in rapid capacity decay. Compared with existing secondary batteries, the secondary battery of the present application has better cycle performance.

[0176] From the comparison between Example 1 and Comparative Example 4 in Table 2 above, it can be seen that when an ester polycyclic compound is used as an additive, although it contains fluorine, the steric hindrance caused by the polycyclic rings increases, and it is difficult to adsorb and combine with the generated Li3Sb film layer. Compared with the other components in the electrolyte, it has no adsorption priority. Therefore, it will also absorb the solvent molecules in the electrolyte, resulting in rapid capacity decay and unable to improve the cycle performance of the secondary battery.

[0177] From the comparison between Example 5 and Comparative Example 3 in Table 2 above, and between Example 2 and Comparative Example 5, it can be seen that when the molar ratio of the antimony element to the fluorine-containing additive exceeds the scope of the present application, a good adsorption relationship cannot be formed between Li3Sb and the fluorine-containing additive, resulting in excessive loss of active ions, leading to loss of the initial capacity of the secondary battery, and also failing to improve the cycle performance of the secondary battery.

[0178] It can be seen from Examples 5-7 and Comparative Example 3 in Table 2 above that when the amount of fluorine-containing additives added to the secondary battery is within an appropriate range, the improvement effect on the cycle performance can be guaranteed; when the amount of fluorine-containing additives in the secondary battery is too much, the electrolyte system, solubility, viscosity and other conditions cannot be guaranteed to be in a good state. Therefore, it is necessary to control the amount of fluorine-containing additives added within an appropriate range.

[0179] It can be seen from Examples 1-3 in Table 2 above that when the antimony content in the secondary battery is within an appropriate range, a good improvement effect on the cycle performance can be ensured; when the antimony content in the secondary battery is too much or too little, it will have a certain impact on the cycle performance of the secondary battery. In order to ensure that a uniform and structurally stable SEI film can be formed on the surface of the negative electrode plate, and to ensure low consumption of active lithium, the antimony content needs to be controlled within an appropriate range to ensure a good improvement effect on the cycle performance of the secondary battery.

[0180] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A secondary battery, characterized in that: include: Negative electrode and electrolyte, The negative electrode sheet contains a negative electrode active material, and the negative electrode active material includes a core and a coating layer containing antimony element arranged on the surface of the core; The electrolyte contains lithium salt and a fluorine-containing additive, wherein the fluorine-containing additive is a fluorine-containing ester monocyclic compound; Wherein, the molar ratio of the antimony element to the fluorine-containing additive is 1:20 to 10:

1.

2. The secondary battery according to claim 1, wherein: The molar ratio of the antimony element to the fluorine-containing additive is 0.9:10 to 6:

10.

3. The secondary battery according to claim 1, wherein: The coating layer containing antimony element contains at least one of antimony element, antimony oxide and antimony trifluoride.

4. The secondary battery according to claim 1, wherein: The coating layer has a thickness of 5 nm to 1000 nm.

5. The secondary battery according to claim 4, characterized in that: The coating layer has a thickness of 20 nm to 400 nm.

6. The secondary battery according to claim 1, wherein: Based on the total mass of the negative electrode active material, the mass percentage of the coating layer is 0.5% to 20%.

7. The secondary battery according to claim 6, characterized in that: Based on the total mass of the negative electrode active material, the mass percentage of the coating layer is 1% to 10%.

8. The secondary battery according to claim 1, wherein: The fluorine-containing additive includes at least one of fluoroethylene carbonate, phenyl trifluoroacetate, and allyl tris (2,2,2-trifluoroethyl) carbonate.

9. The secondary battery according to claim 1, wherein: Based on the total mass of the electrolyte, the mass percentage of the fluorine-containing additive is 0.5% to 20%.

10. The secondary battery according to claim 9, characterized in that Based on the total mass of the electrolyte, the mass percentage of the fluorine-containing additive is 2% to 10%.

11. The secondary battery according to claim 1, wherein The molar concentration of the lithium salt in the electrolyte is 0.7M to 1.5M.

12. The secondary battery according to claim 1, wherein: The core contains at least one of graphite, hard carbon, soft carbon, lithium titanate, tin-based materials, nickel-based materials, and alloy materials.

13. A battery module, characterized in that: A secondary battery comprising any one of claims 1 to 12.

14. A battery pack, characterized in that: Comprising the battery module as claimed in claim 13.

15. An electrical device, characterized in that: The battery comprises at least one selected from the secondary battery according to any one of claims 1 to 12, the battery module according to claim 13, or the battery pack according to claim 14.

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