Secondary battery, battery module including the same, battery pack, and electric device

Abstract

The present invention provides a secondary battery (5) including a positive plate, a negative plate, a separator, and an electrolyte, the positive plate including a positive active material including a core and a coating, the manganese content of the core being ≧25% based on the weight of the core, the coating coating the surface of the core and including one or more of oxides, hydroxides, or oxysalts of element X, the element X being selected from one or more of A1, B, or P, the weight ratio of the coating to the core being 1:5-100, optionally 1:16-100, the electrolyte including a first solvent, the first solvent being selected from one or more of fluorocarbonates, fluorocarboxylates, fluorosulfones, fluoroethers, or fluorobenzenes. The secondary battery has good electrical storage performance and cycle performance. Related battery modules, battery packs, and electric devices are also provided.

Description

[Technical field]

[0001] The present application relates to the technical field of lithium batteries, and in particular to secondary batteries and battery modules, battery packs, and electric devices including the same. [Background technology]

[0002] In recent years, as the application scope of lithium ion batteries becomes wider and wider, people have higher and higher requirements for the performance of secondary batteries, one of which is that they want the secondary batteries to have good storage performance and cycle performance, especially under high voltage operating conditions. Therefore, how to provide a secondary battery with good storage performance and cycle performance under high voltage operating conditions remains a technical problem that engineers need to solve. Summary of the Invention [Problem to be solved by the invention]

[0003] The present application has been made in view of the above problems, and an object of the application is to provide a secondary battery having significantly improved storage performance and cycle performance under high voltage operating conditions. [Means for solving the problem]

[0004] A first aspect of the present application is a secondary battery including a positive electrode plate, a negative electrode plate, a separator, and an electrolyte, The positive plate includes a positive active material including a core and a coating, the manganese content of the core being ≧25% based on the weight of the core, the coating coating a surface of the core and including one or more of an oxide, hydroxide or oxysalt of an element X, the element X being selected from one or more of Al, B or P, the weight ratio of the coating to the core being 1:5-100, optionally 1:16-100; The electrolyte provides a secondary battery comprising a first solvent, the first solvent being selected from one or more of a fluorocarbonate, a fluorocarboxylate, a fluorosulfone, a fluoroether, or a fluorobenzene.

[0005] When the positive electrode active material and the electrolyte of the secondary battery described in the present application satisfy the above conditions, the secondary battery has good stability, which contributes to improving the storage performance and cycle performance of the secondary battery.

[0006] In any embodiment, optionally, the manganese ion elution coefficient k of the positive electrode plate is ≦0.035%, optionally, k≦0.017%, and further optionally, k≦0.01%, and the manganese ion elution coefficient refers to the weight content of manganese ions in the electrolyte after storing the positive electrode plate in a fully charged state and the electrolyte (the electrolyte injection coefficient is 5 g / Ah) together at 60° C. for 48 hours.

[0007] When the manganese ion elution coefficient of the positive electrode plate satisfies the above conditions, the interface stability of the positive electrode can be significantly improved, the side reactions at the interface can be reduced, the stability of the secondary battery can be enhanced, and the storage performance and cycle performance of the secondary battery can be improved.

[0008] In any embodiment, optionally, the stability coefficient of the static protective layer of the positive plate is 54%≦e1≦100%, optionally 70%≦e1≦100%, and further optionally 85%≦e1≦100%, and the stability coefficient of the static protective layer refers to the ratio of the content of the remaining element X in the positive electrode film layer after storing the positive electrode plate in a fully charged state and the electrolyte together at 60° C. for 48 hours to the content of the element X contained in the positive electrode film layer in an initial fully charged state of the positive electrode plate.

[0009] When the stability coefficient of the protective layer of the positive electrode plate satisfies the above condition, the stability of the secondary battery can be further increased, and the storage performance and cycle performance of the secondary battery can be improved.

[0010] In any embodiment, optionally, the stability coefficient e2 of the dynamic protection layer of the positive electrode plate satisfies 20%≦e2≦100%, optionally 50%≦e2≦100%, and further optionally 70%≦e2≦100%, and the stability coefficient of the dynamic protection layer refers to the ratio of the content of the remaining element X in the positive electrode film layer after storing the positive electrode plate in a fully charged state and the electrolyte at 60° C. for 48 hours to the content of the element X contained in the positive electrode film layer before the storage.

[0011] When the stability coefficient e2 of the dynamic protective layer is within the above range, the secondary battery has good stability, which contributes to improving the storage performance and cycle performance of the secondary battery.

[0012] In any embodiment, optionally, the content of element X in the positive electrode membrane layer is 0.05% to 5.35%, optionally 0.1% to 1.61%, and further optionally 0.24% to 1.61%, based on the total weight of the positive electrode active material.

[0013] When the content of element X in the positive electrode membrane layer is within the above range, it can effectively reduce the direct contact between the core material and the electrolyte, reduce the side reaction, reduce the elution of manganese ions, and improve the storage performance and cycle performance of the secondary battery.

[0014] In any embodiment, optionally, the core is LiM p Mn 2-p O 4 , LiN q Mn 1-q PO 4 Or Li 1+t Mn 1-w L w O 2+t wherein 0≦p≦1, 0≦q≦0.5, 0≦t≦1, 0≦w≦0.5; and M, N, and L each independently represent one or more of Ni, Co, Fe, Cr, V, Ti, Zr, La, Ce, Rb, P, W, Nb, Mo, Sb, B, Al, and Si; More selectively, LiM p Mn 2-p O 4 Or Li1+t Mn 1-w L w O 2+t one or more of More selectively, LiNi 0.5 Mn 1.5 O 4 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , Li 2 MnO 3 , LiMnPO 4 One or more of the following:

[0015] When the core material of the secondary battery is selected from the above types, it can improve the energy density of the secondary battery, contribute to reducing the manufacturing cost, and reduce environmental pollution.

[0016] In any embodiment, the coating is optionally selected from alumina, boron oxide, and borate. a+ x [BO 3 ] 3- y , phosphate A a+ x [PO 4 ] 3- y or aluminate A a+ x [AlO 2 ] 1- z A represents one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Ni, Fe, Co, Ti, Al, Cr, V, Nb, W, each compound being electrically neutral; and a, x, y and z are selected from 1, 2 or 3; Optionally, Al 2 O 3 , B 2 O 3 , Li 3 BO 3 , Li 3 PO 4 , Na 3 PO 4 or LiAlO 2One or more of the following:

[0017] When the coating is selected from the above materials, it reduces the elution of transition metals and reduces side reactions at the interface, contributing to improving the performance of the battery.

[0018] JPEG2025516027000002.jpg148152

[0019] JPEG2025516027000003.jpg79152

[0020] When the first solvent and the second solvent are selected from the above solvents, the solvent can form a special solvation structure with the lithium salt in the electrolyte, thereby reducing side reactions of the solvent on the surfaces of the positive and negative electrodes and contributing to extending the life of the secondary battery.

[0021] In any embodiment, optionally, based on the total weight of the first solvent and the second solvent, the content y1 of the first solvent is 10 to 100%, optionally 40 to 100%, and further optionally 80 to 100%.

[0022] In any embodiment, based on the total weight of the first solvent and the second solvent, the content y2 of the second solvent is 0 to 90%, optionally 0 to 60%, and further optionally 0 to 20%.

[0023] In any embodiment, optionally, the content y1 of the first solvent and the content y2 of the second solvent satisfy y1 / y2≧0.66, and optionally y1 / y2≧2.33, and more preferably y1 / y2≧4.

[0024] When the contents of the first solvent and the second solvent are within the above ranges, this contributes to further improving the storage performance and cycle performance of the secondary battery.

[0025] JPEG2025516027000004.jpg86152

[0026] The film-forming additive can preferentially form a film on the negative electrode, reduce the loss of active lithium, and further improve the performance of the battery.

[0027] In any embodiment, optionally, based on the total weight of the first solvent and the second solvent, the content of the film-forming additive is 0.5% to 20%, optionally 1% to 10%, and further optionally 1% to 5%.

[0028] JPEG2025516027000005.jpg51152

[0029] When the electrolyte contains the above-mentioned amount of the film-forming additive, it contributes to further improving the storage performance and cycle performance of the secondary battery.

[0030] In any embodiment, optionally, the core further contains a doping element, and the doping element is selected from one or more of W, Nb, Sb, Ti, Zr, La, Ce, and S, and optionally one or more of W and Nb.

[0031] Doping with elements improves the electrochemical properties of the positive electrode active material and contributes to improving the electrochemical performance of the corresponding secondary battery.

[0032] In any embodiment, optionally, based on the total weight of the core, the content of the doping element is 0.05% to 5%, and optionally 0.1% to 2%.

[0033] In any embodiment, optionally, the particles of the positive electrode active material are single crystals or pseudo single crystals.

[0034] When the positive electrode active material is a single crystal, the active material itself is difficult to crush, the probability of exposing a new surface is reduced, the side reaction of the electrolyte is further reduced, and the stability of the electrolyte can be improved.

[0035] In any embodiment, optionally, the particle size of the positive electrode active material is 1 to 20 μm, optionally 3 to 15 μm.

[0036] When the particle size of the positive electrode active material is within the above range, it contributes to avoiding an increase in energy consumption in the process and deterioration of the processing performance of the positive electrode plate caused by an excessively large particle size.

[0037] In any embodiment, optionally, the acidity of the electrolyte is ≦50 ppm and the purity of each solvent used is ≧99.9%.

[0038] When the acidity and purity of the electrolyte are within the above ranges, the electrolyte has good stability and is less likely to cause side reactions, which contributes to improving the cycle performance of the secondary battery.

[0039] A second aspect of the present application provides a battery module including the secondary battery according to the first aspect of the present application. The battery module can be manufactured by a method for manufacturing a battery module commonly used in the art.

[0040] A third aspect of the present application provides a battery pack including the battery module according to the second aspect of the present application. The battery pack can be manufactured by a battery pack manufacturing method commonly used in the art.

[0041] A fourth aspect of the present application provides an electric device including at least one selected from the secondary battery according to the first aspect of the present application, the battery module according to the second aspect of the present application, or the battery pack according to the third aspect of the present application. Effect of the Invention

[0042] In the secondary battery described in the present application, the positive electrode active material includes a core and a coating covering the surface of the core, and the weight ratio of the coating to the core is 1:5 to 100. The appropriate weight ratio of the coating to the core contributes to ensuring that the coating effectively reduces the direct contact between the core material and the electrolyte, reduces side reactions at the interface, and improves the storage performance and cycle performance of the secondary battery, while avoiding the deterioration of the dynamic performance of the secondary battery due to excessive coating. In addition, the coating itself is a fast ion conductor, and does not obviously reduce the capacity of the entire positive electrode active material, contributing to the secondary battery having a high energy density. In addition, the electrolyte in the secondary battery of the present application includes a first solvent selected from fluorinated solvents, thereby improving the fluorination degree of the electrolyte, increasing the compatibility of the electrolyte with the positive and negative electrodes, reducing the destruction of the electrolyte against the positive and negative electrode materials, and further contributing to improving the storage performance and cycle performance of the secondary battery.

[0043] The battery module, battery pack, and electric device of the present application include the secondary battery provided by the present application, and therefore have at least the same advantages as the secondary battery. [Brief description of the drawings]

[0044] [Figure 1] FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application. [Diagram 2] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. [Diagram 3] FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application. [Figure 4] FIG. 4 is a schematic diagram of a battery pack according to one embodiment of the present application. [Diagram 5] FIG. 5 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG. [Figure 6] FIG. 6 is a schematic diagram of an electrical device that uses a secondary battery according to one embodiment of the present application as a power source. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Hereinafter, with reference to the drawings as appropriate, embodiments specifically disclosing the secondary battery, battery module, battery pack, and electric device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and duplicated description of substantially the same structure may be omitted. This is to avoid the following description becoming unnecessarily redundant and to allow those skilled in the art to easily understand. Furthermore, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the scope of the claims.

[0046] The "ranges" disclosed herein are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the given range. Such a defined range may be inclusive or exclusive of both end values, and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a given parameter, it is understood that ranges of 60-110 and 80-120 are also anticipated. Also, if 1 and 2 are listed as the minimum range values, and 3, 4, and 5 are listed as the maximum range values, then the ranges of 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all anticipated. In this application, unless otherwise stated, the numerical range "a-b" represents an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are recited herein, and "0-5" is simply shorthand for combinations of these numerical values. Note that when a parameter is stated to be an integer ≧2, this is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0047] Unless otherwise stated, all the embodiments and optional embodiments in the present application can be combined with each other to form new technical solutions.

[0048] Unless otherwise stated, all technical features and optional technical features in the present application can be combined with each other to form new technical solutions.

[0049] Unless otherwise stated, all steps in this application may be performed in sequence, randomly, and preferably in sequence. For example, a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, or may include steps (b) and (a) performed in sequence. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), or may include steps (c), (a) and (b).

[0050] Unless otherwise stated, the terms "comprise" and "comprising" referred to in this application may be open ended or closed ended. For example, "comprise" and "comprising" may indicate that the composition may further include or include other components not listed, or may include or include only the listed components.

[0051] Unless otherwise 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 one 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 A and B are both true (or exist).

[0052] It should be noted that in this application, the term "fully charged state" refers to the state when the secondary battery is charged to the upper cut-off voltage. Similarly, the term "initial fully charged state" refers to the state when the secondary battery is charged to the upper cut-off voltage after the secondary battery is manufactured and the electrolyte does not contain elemental manganese.

[0053] In this application, the term "stability coefficient of protective layer" can be further subdivided into "stability coefficient of static protective layer" and "stability coefficient of dynamic protective layer". The distinction between the two is that the secondary battery used when measuring the stability coefficient e1 of the static protective layer is a newly manufactured secondary battery, but the secondary battery used when measuring the stability coefficient e2 of the dynamic protective layer is not limited and may be a newly manufactured secondary battery or a secondary battery that has been used for a certain period of time.

[0054] The inventors have found that in practical work, when a secondary battery operates at a high voltage such as 4.2V or more, the elution of transition metals in the positive electrode active material becomes serious, which deteriorates the storage performance and cycle performance of the secondary battery. After extensive experiments, the inventors have found that when the positive electrode active material includes a core and a coating covering the core surface, and the weight ratio of the coating to the core is 1:5 to 100, the stability of the secondary battery under high voltage operating conditions can be effectively improved, and the storage performance and cycle performance of the secondary battery can be improved. Furthermore, when the electrolyte contains a first solvent selected from fluorinated solvents, the compatibility of the electrolyte with the positive and negative electrodes can be improved, and the stability of the secondary battery under high voltage operating conditions can be further improved, thereby improving the performance of the secondary battery.

[0055] After further intensive research, the inventors discovered that when the manganese ion elution coefficient of the positive electrode plate or the stability coefficient of the protective layer meets certain conditions, the stability of the secondary battery can be further significantly improved, and the storage performance and cycle performance of the secondary battery can be improved.

[0056] [Secondary battery] A first aspect of the present application is a secondary battery including a positive electrode plate, a negative electrode plate, a separator, and an electrolyte, The positive plate includes a positive active material including a core and a coating, the manganese content of the core being ≧25% based on the weight of the core, the coating coating the surface of the core and including one or more of an oxide, hydroxide or oxysalt of element X, the element X being selected from one or more of Al, B or P, the weight ratio of the coating to the core being 1:5-100, optionally 1:16-100; The electrolyte provides a secondary battery comprising a first solvent, the first solvent being selected from one or more of a fluorocarbonate, a fluorocarboxylate, a fluorosulfone, a fluoroether, or a fluorobenzene.

[0057] In the secondary battery described in the present application, the positive electrode active material includes a core and a coating covering the surface of the core, and the weight ratio of the coating to the core is 1:5 to 100. The appropriate weight ratio of the coating to the core contributes to ensuring that the coating effectively reduces the direct contact between the core material and the electrolyte, reduces side reactions at the interface, and improves the storage performance and cycle performance of the secondary battery, while avoiding the deterioration of the dynamic performance of the secondary battery due to excessive coating. In addition, the coating itself is a fast ion conductor, and does not obviously reduce the capacity of the entire positive electrode active material, contributing to the secondary battery having a high energy density. In addition, the electrolyte in the secondary battery of the present application includes a first solvent selected from fluorinated solvents, thereby improving the fluorination degree of the electrolyte, increasing the compatibility of the electrolyte with the positive and negative electrodes, reducing the damage of the electrolyte to the positive and negative electrode materials, and further contributing to improving the storage performance and cycle performance of the secondary battery.

[0058] In some embodiments, the manganese ion elution coefficient k of the positive plate is optionally ≦0.035%, optionally ≦0.017%, and further optionally ≦k ≦0.01%, and the manganese ion elution coefficient refers to the weight content of manganese ions in the electrolyte after storing a fully charged positive plate and an electrolyte (the electrolyte injection coefficient is 5 g / Ah) together at 60° C. for 48 hours.

[0059] When the manganese ion elution coefficient of the positive electrode plate satisfies the above conditions, the interface stability of the positive electrode can be significantly improved, the side reactions at the interface can be reduced, the stability of the secondary battery can be enhanced, and the storage performance and cycle performance of the secondary battery can be improved.

[0060] In some embodiments, optionally, the stability coefficient of the static protective layer of the positive plate is 54%≦e1≦100%, optionally 70%≦e1≦100%, and further optionally 85%≦e1≦100%, and the stability coefficient of the static protective layer refers to the ratio of the content of the remaining element X in the positive electrode film layer to the content of the element X contained in the positive electrode film layer in the initial fully charged state of the positive electrode plate after storing the fully charged positive electrode plate and the electrolyte at 60° C. for 48 hours.

[0061] The stability coefficient e1 of the static protective layer can suitably reflect the degree of dissolution of the element X in the positive electrode film layer in the electrolyte. When the stability coefficient of the static protective layer satisfies the above condition, the secondary battery has good stability, which contributes to improving the storage performance and cycle performance of the secondary battery.

[0062] If the content of element X in the positive electrode film layer in the initial fully charged state of the secondary battery after a certain period of use is not known in advance, the stability coefficient of the static protective layer It will be explained that it becomes difficult to obtain e1. Instead, the stability coefficient e2 of the dynamic protective layer can be used to evaluate the dissolution rate of element X in the positive electrode film layer into the electrolyte. The larger the stability coefficient e2 of the dynamic protective layer, the smaller the dissolution rate of element X in the positive electrode film layer into the electrolyte, indicating a high stability of the secondary battery, and conversely, the higher the dissolution rate, the lower the stability of the secondary battery.

[0063] In some embodiments, optionally, the stability coefficient of the dynamic protective layer of the positive plate satisfies 20%≦e2≦100%, optionally 50%≦e2≦100%, and further optionally 70%≦e2≦100%, and the stability coefficient of the dynamic protective layer refers to the ratio of the content of the remaining element X in the positive electrode film layer after storing the fully charged positive electrode plate and the electrolyte at 60° C. for 48 hours to the content of the element X contained in the positive electrode film layer before the storage.

[0064] When the stability coefficient e2 of the dynamic protective layer is within the above range, the secondary battery has good stability, which contributes to improving the storage performance and cycle performance of the secondary battery.

[0065] In general, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are repeatedly inserted and removed between the positive electrode plate and the negative electrode plate. The electrolyte serves to conduct ions between the positive electrode plate and the negative electrode plate. The separator is provided between the positive electrode plate and the negative electrode plate, and serves mainly to prevent short-circuiting between the positive and negative electrodes, while allowing ions to pass through. The positive electrode plate, the negative electrode plate, the electrolyte, and the separator described in the present application will be described below.

[0066] [Positive plate] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0067] As an example, the positive electrode current collector has two surfaces opposing each other in the thickness direction of the positive electrode current collector, and the positive electrode film layer is provided on either one or both of the two opposing surfaces of the positive electrode current collector.

[0068] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, the metal foil may be an aluminum foil. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0069] In some embodiments, the core of the cathode active material described herein may optionally be LiMp Mn 2-p O 4 , Lin q Mn 1-q PO 4 Or Li 1+t Mn 1-w L w O 2+t wherein 0≦p≦1, 0≦q≦0.5, 0≦t≦1, 0≦w≦0.5; and M, N, and L each independently represent one or more of Ni, Co, Fe, Cr, V, Ti, Zr, La, Ce, Rb, P, W, Nb, Mo, Sb, B, Al, and Si; More selectively, LiM p Mn 2-p O 4 Or Li 1+t Mn 1-w L w O 2+t one or more of More selectively, LiNi 0.5 Mn 1.5 O 4 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , Li 2 MnO 3 , LiMnPO 4 One or more of the following:

[0070] When the core material of the secondary battery is selected from the above types, it can improve the energy density of the secondary battery, contribute to reducing the manufacturing cost, and reduce environmental pollution.

[0071] In some embodiments, the coating of the positive electrode active material described herein is optionally selected from the group consisting of alumina, boron oxide, and borate. a+ x [BO 3 ] 3- y , phosphate A a+ x [PO 4 ] 3- y or aluminate A a+x [AlO 2 ] 1- z A is selected from one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Ni, Fe, Co, Ti, Al, Cr, V, Nb, W, each compound being electrically neutral; a, x, y, and z are selected from 1, 2, or 3; Optionally, Al 2 O 3 , B 2 O 3 , Li 3 BO 3 , Li 3 PO 4 , Na 3 PO 4 or LiAlO 2 One or more of the following:

[0072] When the coating is selected from the above materials, it reduces the elution of transition metals and reduces side reactions at the interface, thereby improving the performance of the battery. Furthermore, the coating itself is a fast ion conductor, and does not obviously reduce the capacity of the entire positive electrode active material, thereby contributing to the secondary battery having a high energy density.

[0073] In some embodiments, the content of element X in the positive electrode membrane layer is preferably 0.05% to 5.35%, more preferably 0.1% to 1.61%, and even more preferably 0.24% to 1.61%, based on the total weight of the positive electrode active material.

[0074] When the content of element X in the positive electrode membrane layer is within the above range, it can effectively reduce the direct contact between the core material and the electrolyte, reduce the side reaction, reduce the elution of manganese ions, and improve the storage performance and cycle performance of the secondary battery.

[0075] In some embodiments, optionally, the core further comprises a doping element selected from one or more of W, Nb, Sb, Ti, Zr, La, Ce, S, and optionally one or more of W, Nb.

[0076] The doping of elements improves the electrochemical properties of the positive electrode active material, which contributes to improving the electrochemical performance of the corresponding secondary battery.

[0077] In some embodiments, optionally, the content of the doping element is 0.05% to 5%, optionally 0.1 to 2%, based on the total weight of the core.

[0078] Optionally, in some embodiments, the particles of the positive electrode active material are single crystal or pseudo-single crystal.

[0079] When the positive electrode active material is a single crystal, the active material itself is less likely to be broken, reducing the probability of exposing new surfaces, and further reducing side reactions of the electrolyte, thereby improving the stability of the electrolyte.

[0080] In some embodiments, the particle size of the positive electrode active material is optionally 1 to 20 μm, and optionally 3 to 15 μm. The particle size of the positive electrode active material can be measured by a method commonly used in the art, for example, by testing with reference to the standard GB / T 19077-2016 / ISO 13320:2009.

[0081] When the particle size of the positive electrode active material is within the above range, it contributes to avoiding an increase in energy consumption in the process and deterioration of the processing performance of the positive electrode plate caused by an excessively large particle size.

[0082] In some embodiments, the positive electrode active material optionally comprises 85-99% of the total weight of the positive electrode membrane layer, and optionally comprises 93-97% of the total weight of the positive electrode membrane layer. For example, the positive electrode active material may comprise 85%, 90%, 95.5%, or 97% of the total weight of the positive electrode membrane layer.

[0083] In some embodiments, the positive electrode membrane layer may further include a binder. For 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.

[0084] In some embodiments, the binder optionally comprises 0.1 to 3.5% of the total weight of the positive electrode membrane layer, optionally 0.5 to 2.5%.

[0085] In some embodiments, the positive electrode film layer optionally further comprises a conductive agent. For example, the conductive agent may comprise at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0086] In some embodiments, the conductive agent optionally comprises 0.05 to 5% of the total weight of the positive electrode membrane layer, optionally 0.5 to 3%.

[0087] In some embodiments, the positive electrode plate can be manufactured by the following method. The components for manufacturing the positive electrode plate described above, such as the positive electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. The positive electrode slurry is applied to a positive electrode current collector, and after processes such as drying and cold pressing, a positive electrode plate can be obtained.

[0088] [Negative plate] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0089] As an example, the negative electrode current collector has two surfaces opposing each other in the thickness direction of the negative electrode current collector, and the negative electrode film layer is provided on either one or both of the two opposing surfaces of the negative electrode current collector.

[0090] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, the metal foil may be a copper foil. The composite current collector may include a polymeric base layer and a metal layer formed on at least one surface of the polymeric substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymeric substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0091] In some embodiments, the negative electrode active material may be any negative electrode active material known in the art for batteries. As an example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of silicon alone, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of tin alone, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials used as negative electrode active materials in batteries may be used. These negative electrode active materials may be used alone or in combination of two or more.

[0092] In some embodiments, the negative electrode membrane layer optionally further comprises a binder, which can 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).

[0093] In some embodiments, the negative electrode film layer optionally further comprises 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.

[0094] In some embodiments, the negative electrode membrane layer optionally further comprises other auxiliary agents, such as a thickening agent (eg, sodium carboxymethylcellulose (CMC-Na)).

[0095] In some embodiments, the negative electrode plate can be manufactured by the following method. The components for manufacturing the negative electrode plate described above, such as the negative electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry. The negative electrode slurry is applied to a negative electrode current collector, and after processes such as drying and cold pressing, a negative electrode plate can be obtained.

[0096] [Electrolyte] The electrolyte serves to conduct ions between the positive and negative plates and typically includes an electrolyte salt and a solvent.

[0097] JPEG2025516027000006.jpg164152

[0098] When the electrolytic solution contains the first solvent, it contributes to improving the stability of the electrolytic solution, improving the compatibility of the electrolytic solution with the positive and negative electrodes, and improving the storage performance and cycle performance of the secondary battery.

[0099] JPEG2025516027000007.jpg76152

[0100] When both the first solvent and the second solvent are selected from the above solvents, the solvent can form a special solvation structure with the lithium salt in the electrolyte, thereby reducing side reactions of the solvent on the surfaces of the positive and negative electrodes and contributing to extending the life of the secondary battery.

[0101] In some embodiments, the content y1 of the first solvent is 10-100%, optionally 40-100%, and further optionally 80-100% based on the total weight of the first solvent and the second solvent. For example, the content y1 of the first solvent is 40%, 70%, 80%, 95%, or It could be 100%.

[0102] In some embodiments, the content y2 of the second solvent is optionally 0 to 90%, optionally 0 to 60%, and further optionally 0 to 20% based on the total weight of the first solvent and the second solvent. For example, the content y2 of the second solvent may be 0%, 5%, 20%, 30%, or 60%.

[0103] When the contents of the first solvent and the second solvent are within the above ranges, the stability of the electrolyte is further improved, which contributes to improving the storage performance and cycle performance of the secondary battery.

[0104] In some embodiments, optionally, the sum of the weights of the first solvent and the second solvent accounts for 60 to 90%, optionally 60 to 87.5%, of the total weight of the electrolyte solution of the present application.

[0105] When the weight percentage of the sum of the weights of the first solvent and the second solvent relative to the electrolyte of the present application is within the above range, this contributes to further improving the stability of the electrolyte.

[0106] In some embodiments, optionally, the first solvent content y1 and the second solvent content y2 satisfy y1 / y2≧0.66, optionally y1 / y2≧2.33, and further optionally y1 / y2≧4.

[0107] When the content y1 of the first solvent and the content y2 of the second solvent satisfy the above relationship, the electrolyte has better electrochemical stability, further improves the compatibility of the electrolyte with the positive and negative electrodes, reduces side reactions, and helps to improve the storage performance and cycle performance of the secondary battery.

[0108] JPEG2025516027000008.jpg19152

[0109] When the content y1 of the first solvent and the content y2 of the second solvent satisfy the above relationship, the stability of the electrolyte is further improved, which helps to improve the storage performance and cycle performance of the secondary battery.

[0110] In some embodiments, optionally, the electrolyte salt in the electrolyte solution 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 bisoxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0111] In some embodiments, the concentration of the lithium salt is optionally 5 to 50% by weight, optionally 8 to 40% by weight, based on the total weight of the electrolyte.

[0112] When the electrolyte contains the above-mentioned lithium salt at a certain concentration, the viscosity of the electrolyte is appropriate, which improves the conductivity of the electrolyte and contributes to further improving the performance of the secondary battery. However, if the concentration of the lithium salt in the electrolyte is too high, the concentration of the electrolyte as a whole increases, but the dissociation degree of the salt in the electrolyte decreases, and the viscosity of the electrolyte also increases, which in turn reduces the conductivity of the electrolyte.

[0113] JPEG2025516027000009.jpg81152

[0114] The film-forming additive can preferentially form a film on the negative electrode, reduce the loss of active lithium, and further improve the storage and cycle performance of the secondary battery.

[0115] In some embodiments, optionally, the content of the film-forming additive is 0.5-20%, optionally 1-10%, and further optionally 1-5%, based on the total weight of the first solvent and the second solvent.

[0116] JPEG2025516027000010.jpg50152

[0117] When the electrolyte contains the above-mentioned film-forming additive in an amount, it contributes to further improving the stability of the electrolyte, and further improving the storage performance and cycle performance of the corresponding secondary battery.

[0118] In some embodiments, the electrolyte of the present application optionally further comprises other functional additives, which may be any additives known in the art that are applicable in the context of the present application. For example, the electrolyte further comprises at least one of a flame retardant additive, an overcharge prevention additive, and a conductive additive. The electrolyte further comprises the additives, which can further improve the performance of the electrolyte.

[0119] In some embodiments, optionally, the acidity of the electrolyte is ≦50 ppm and the purity of each solvent used is ≧99.8%.

[0120] When the acidity and purity of the electrolyte are within the above ranges, the electrolyte has good stability and is less likely to cause side reactions, which contributes to improving the cycle performance of the secondary battery.

[0121] The acidity of the electrolyte in this application can be tested by a method commonly used in the art, specifically, see HG / T4067-2015, which describes that triethylamine standard solution can be used to titrate the free acid in the electrolyte.

[0122] In some embodiments, the electrolyte injection coefficient of the secondary battery described herein is optionally 1.8-4g / Ah, optionally 2.4-3.2g / Ah. As an example, if the electrolyte injection coefficient of the secondary battery is 2.8g / Ah and the cell capacity is designed to be 3Ah, the injection amount is 2.8*3g=8.4g.

[0123] It is explained that the electrolyte solution described in the present application can be prepared by a method commonly used by those skilled in the art so that those skilled in the art can understand. For example, the electrolyte solution described in the present application can be prepared by mixing a first solvent, a second solvent, a lithium salt, a film-forming additive, other additives, etc. in a certain ratio under the protection of an inert gas and stirring the mixture uniformly.

[0124] [Separator] In some embodiments, the secondary battery further includes a separator. In the present application, the type of the separator is not particularly limited, and any known separator having a porous structure with good chemical stability and mechanical stability can be selected.

[0125] 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, and is not particularly limited. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, and is not particularly limited.

[0126] A second aspect of the present application provides a battery module including the secondary battery according to the first aspect of the present application.

[0127] A third aspect of the present application provides a battery pack including the battery module according to the second aspect of the present application.

[0128] A fourth aspect of the present application provides an electric device including at least one of the secondary battery according to the first aspect of the present application, the battery module according to the second aspect, or the battery pack according to the third aspect. The secondary battery, the battery module, or the battery pack may be used as a power source for the electric device, or may be used as an energy storage unit for the electric device. The electric device may include, but is not limited to, mobile devices (e.g., mobile phones, notebook computers, etc.), electric vehicles (e.g., secondary battery electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric cars, ships and satellites, energy storage systems, etc.

[0129] For an electrical device, a secondary battery, a battery module, or a battery pack can be selected according to the needs of its use.

[0130] The secondary battery, battery module, battery pack, and electric device of the present application will be described below with appropriate reference to the drawings.

[0131] In some embodiments, the positive and negative plates and the separator can be manufactured into an electrode assembly by a winding or lamination process.

[0132] In some embodiments, the secondary battery may include an exterior body that can be used to package the electrode assembly and the electrolyte.

[0133] In some embodiments, the exterior body of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior body of the secondary battery may be a soft pack, such as a bag-type soft pack, etc. The material of the soft pack may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0134] In the present application, the shape of the secondary battery is not particularly limited and may be cylindrical, rectangular or any other shape. For example, FIG. 1 shows a secondary battery 5 having a rectangular structure as an example.

[0135] In some embodiments, referring to FIG. 2, the exterior body may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate surround the chamber to form a chamber. The case 51 has an opening communicating with the chamber, and the cover plate 53 may cover the opening to seal the chamber. The positive electrode plate, the negative electrode plate and the separator may form an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the chamber. The electrolyte infiltrates the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and may be selected by those skilled in the art according to specific practical requirements.

[0136] In some embodiments, the secondary batteries can be assembled into a battery module, and the number of secondary batteries included in the battery module can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery module.

[0137] Fig. 3 shows an example of a battery module 4. Referring to Fig. 3, in the battery module 4, the multiple secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the multiple secondary batteries 5 may be fixed by a fastening member.

[0138] Optionally, the battery module 4 may further include a housing having an accommodating space, and the multiple secondary batteries 5 are accommodated in the accommodating space.

[0139] In some embodiments, the above battery modules can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0140] 4 and 5 show an example of a battery pack 1. Referring to Fig. 4 and Fig. 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box may include an upper box 2 and a lower box 3, and the upper box 2 may cover the lower box 3 to form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box according to any form.

[0141] 6 shows an example of an electric device, such as a secondary battery electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack or a battery module can be adopted to meet the high power and high energy density requirements for the secondary battery of the electric device.

[0142] Another example of the device may be a mobile phone, a tablet, a laptop, etc. Such devices usually require light weight and thinness, and may employ a secondary battery as a power source.

[0143] Working Example The following examples of the present application are described. The examples described below are illustrative and are merely for the purpose of interpreting the present application, and should not be understood as limiting the present application. If no specific techniques or conditions are specified in the examples, they are performed according to the techniques or conditions described in the literature in the field or according to the product specifications. If no manufacturer is specified for the reagents or equipment used, they are all ordinary products that are commercially available.

[0144] The weight average molecular weight of polyvinylidene fluoride (PVDF) used in the examples of this application is about 900,000, and the purity of various solvents used in the examples of this application is greater than 99.9%. Unless otherwise specified, all materials used in the examples of this application are based on weight without water of crystallization.

[0145] Example 1 (Production of positive electrode active material) LiNi 0.5 Mn 1.5 O 4 was added to a suitable amount of deionized water and stirred to mix evenly to form a suspension. 3 PO 4 The mixture was then thoroughly stirred until homogenized. The mixture was then filtered and dried to obtain a solid powder. The solid powder was then heated at 650°C for 8 hours to obtain a Li-ion powder. 3 PO 4 LiNi coated with 0.5 Mn 1.5 O 4 Based on the total weight of the obtained positive electrode active material, the content of P element in the coating was 0.50%.

[0146] Except for the different types of added substances and the contents of the corresponding elements, the manufacturing methods of the positive electrode active materials in the comparative example and other examples were the same as the above-mentioned methods.

[0147] (Manufacturing positive electrodes) The positive electrode active material obtained in the above step, the conductive carbon black (Super P), and the binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 95.5:2.5:2 in an appropriate amount of NMP solvent by thorough stirring to form a uniform positive electrode slurry, which was then uniformly applied to the surface of the aluminum foil of the positive electrode current collector, and then coated on both sides. After drying and cold pressing, a positive electrode plate was obtained. The amount of positive electrode active material carried on one side of the positive electrode current collector was 0.020 g / cm. 2 It was.

[0148] (Manufacturing of negative plates) The negative electrode active material artificial graphite, the conductive agent carbon black (Super P), the binder styrene butadiene rubber, and the thickener sodium carboxymethyl cellulose were mixed in a mass ratio of 96:1:1:2 with an appropriate amount of deionized water as a solvent and thoroughly stirred to form a uniform negative electrode slurry, which was then uniformly applied to one side of the copper foil surface of the negative electrode current collector. After drying and cold pressing, a negative electrode plate was obtained. The amount of negative electrode active material carried on one side of the negative electrode current collector was 0.008 g / cm. 2 It was.

[0149] (Electrolyte production) Argon atmosphere glove box (H 2 O<0.1ppm, O 2 <0.1 ppm), referring to Table 1, various organic solvents were uniformly mixed in the mass ratios shown, salts and additives shown in Table 1 were added, and the mixture was stirred uniformly to obtain the electrolyte solution of Example 1.

[0150] (Separator) A polypropylene film was used as a separator.

[0151] (Secondary battery manufacturing) The positive electrode plate, separator, and negative electrode plate were stacked in this order, and a separator was placed between the positive and negative electrodes to serve as an insulator. The electrode assembly was placed in a battery case, dried, and then an electrolyte was injected. The secondary battery of Example 1 was manufactured through processes such as chemical formation and standing. The size of the secondary battery was 60×130×4 mm, and the corresponding sizes of the positive and negative electrodes were both 87×700 mm. The electrolyte injection coefficient was It was 2.8g / Ah.

[0152] Examples 2 to 20 and Comparative Examples 1 to 3 Except for the different conditions shown in Table 1, the other conditions of Examples 2 to 20 and Comparative Examples 1 to 3 were the same as those of Example 1.

[0153] (Test methods for related parameters) 1. Cell Capacity (C) Test At 25°C, the lithium-ion battery was constant current charged at 0.1C to an upper cut-off voltage, followed by constant voltage charging at this voltage until the current was less than 0.05C, and then discharged at 0.1C to a lower cut-off voltage to obtain the discharge capacity C (Ah).

[0154] 2. Testing manganese ion elution coefficient and protective layer stability coefficient At 25℃, the lithium-ion batteries (two parallel samples) were charged with constant current at 0.1C to the upper cut-off voltage, then with constant voltage at this voltage until the current was less than 0.05C, and then disassembled in a glove box. The positive plate of one of the lithium batteries was immersed in dimethyl carbonate for 1h*3 times (after completing a single immersion, the dimethyl carbonate was immediately replaced for the next immersion), and then dried and subjected to element content test to obtain the weight-based content of element X in the positive electrode film layer as x1.

[0155] For the other parallel sample, the positive plate was taken out in a similar manner, then added to the corresponding 5g / Ah electrolyte (composition shown in Table 1), sealed, and placed in a 60°C oven for 48h. The corresponding electrolyte was then taken out in a glove box, and the elemental content test was then performed to measure the weight-based content of manganese ions (manganese element) in the electrolyte, and then divided by the weight of the electrolyte to obtain the weight content of manganese ions (manganese element) in the electrolyte, which was designated as y1. Accordingly, the positive plate after storage was immersed in dimethyl carbonate for 1h*3 times (after the completion of a single immersion, the dimethyl carbonate was immediately replaced for the next immersion), and then dried, after which the elemental content test was performed to obtain the weight-based content of element X in the positive electrode film layer, which was designated as x2. In this case, the manganese ion elution coefficient k=y1 of the secondary battery, and the stability coefficient e=x2 / x1 of the protective layer.

[0156] The stability coefficient e1 of the static protective layer and the stability coefficient e2 of the dynamic protective layer can both be measured by the above-mentioned method for measuring the stability coefficient of the protective layer, and the difference between them is that the secondary battery used when measuring the stability coefficient e1 of the static protective layer is a newly manufactured secondary battery, but the secondary battery used when measuring the stability coefficient e2 of the dynamic protective layer is not limited and may be a newly manufactured secondary battery or a secondary battery that has been used for a certain period of time. In the examples and comparative examples of the present application, a newly manufactured secondary battery was tested, so the stability coefficient of the protective layer in Table 1 is the stability coefficient e1 of the static protective layer.

[0157] The manganese ion content in the electrolyte and the manganese element and element X content in the positive electrode film layer are tested by inductively coupled plasma atomic emission spectrometry. The instrument specifications refer to EPA6010D-2014 "Inductively Coupled Plasma Atomic Emission Spectroscopy" and JY / T015-1996 "General Rules for Inductively Coupled Plasma Atomic Emission Spectroscopy".

[0158] The content of manganese element and the content of element X (B or P) in the positive electrode film layer can be measured by punching the positive electrode plate into small disks with a radius of 7 mm, weighing six positive small disks, and taking the corresponding weight as m1, adding 10 ml of aqua regia, heating to thoroughly digest, and then diluting with deionized water to a constant volume of 100 ml. The solution is tested by inductively coupled plasma optical emission spectroscopy to obtain the content of element X contained in the corresponding six positive small disks, which is taken as m2. In addition, the corresponding six small disks with a radius of 7 mm, the positive electrode plate substrate (aluminum substrate), are taken, and the mass is measured and taken as m3. In this case, the corresponding content of element X is x1=m2 / (m1-m3).

[0159] When the element X is aluminum, the method for testing the content of X in the positive electrode active material is slightly different: scrape off the active material on the plate surface (be careful not to scrape off the aluminum substrate), measure the mass of the scraped mixture as m4, and then measure the mass of X in the mixture as above as m2. In this case, the corresponding content of X element (Al) is m2 / m4.

[0160] The test method for the manganese ion content in the electrolyte is as follows: take about 1 g of electrolyte, add 10 ml of concentrated HNO 3 Acid (mass fraction 68%) was added, followed by Heat at 180°C for 30 minutes, then dilute to 50ml with deionized water. Test the solution by inductively coupled plasma atomic emission spectroscopy to finally determine the weight content of manganese ion (elemental manganese) in the corresponding electrolyte, and divide by the mass of the electrolyte to obtain the weight content of manganese ion (elemental manganese) in the electrolyte, which is designated as y1.

[0161] 3. Testing the gram capacity of the positive electrode active material At 25°C, the secondary battery is charged at a constant current of 0.33C up to the upper cut-off voltage, then charged at a constant voltage at this cut-off voltage until the current reaches 0.05C. After standing for 5 minutes, the secondary battery is discharged at a constant current of 0.33C down to the lower cut-off voltage. The discharge capacity obtained at this time is the initial discharge capacity of the secondary battery.

[0162] Initial discharge gram capacity (mAh / g) of the positive electrode active material = initial discharge capacity of the secondary battery / total mass of the positive electrode active material.

[0163] 4. Cycle performance test of secondary batteries At 45°C, the secondary battery is charged at a constant current of 0.1C to the upper cut-off voltage, then charged at a constant voltage of 0.05C at this cut-off voltage, and after 5 minutes of standing, the secondary battery is discharged at a constant current of 0.1C to the lower cut-off voltage, which is one charge-discharge cycle process, and the discharge capacity this time is the initial discharge capacity of the secondary battery. The charge-discharge cycle is repeated according to the above method for the secondary battery until the discharge capacity after the cycle is attenuated to 80% of the initial discharge capacity, the test is terminated, and the number of cycles of the secondary battery at this time is recorded. The more cycles the secondary battery has, the longer the expected cycle life of the secondary battery is.

[0164] 5. Secondary battery storage performance test At 25°C, the secondary battery was charged at a constant current of 0.1C to the upper cut-off voltage, and then at this cut-off voltage, was charged at a constant voltage of 0.05C, at which point the secondary battery was in a fully charged state. The fully charged secondary battery was stored in an environment of 25°C, taken out once every 5 days, and discharged at a constant current of 0.1C to the lower cut-off voltage to obtain the discharge amount after a certain period of storage. After that, the secondary battery was fully charged as described above and stored again in an environment of 25°C until the discharge capacity of the secondary battery after storage attenuated to 80% of the initial discharge capacity, the test was completed, and the total storage days of the secondary battery were recorded. The longer the storage days of the secondary battery, the longer the expected room temperature storage life of the secondary battery.

[0165] It should be noted that in the above performance tests, the upper cutoff voltage in the examples and comparative examples is 4.95 V and the lower cutoff voltage is 3.0 V. Table 1 shows the performance test results of Examples 1 to 20 and Comparative Examples 1 to 3.

[0166] [Table 1] JPEG2025516027000012.jpg251156Table 1 (continued) JPEG2025516027000013.jpg251160JPEG2025516027000014.jpg251148

[0167] As can be seen from Table 1, when the positive electrode active material contains a coating and the electrolyte contains a first solvent, the storage performance and cycle performance of the corresponding secondary battery are better than those of the corresponding secondary battery that does not contain any coating or does not contain the first solvent. Furthermore, when the manganese ion elution coefficient k of the positive electrode plate is ≦ 0.035% or the stability coefficient e1 of the static protective layer is ≧ 54%, the storage performance and cycle performance of the corresponding secondary battery are better. In addition, the storage performance and cycle performance of the secondary battery can be further improved by adjusting the amount of the first solvent and the second solvent used, and the type and amount of the film-forming additive used.

[0168] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and all embodiments that have substantially the same configuration as the technical idea within the scope of the technical solution of the present application and exhibit the same action and effect are included within the technical scope of the present application. In addition, various modifications that a person skilled in the art can conceive of to the embodiments and other forms formed by combining some of the components in the embodiments are also included within the scope of the present application, within the scope of the present application. [Explanation of symbols]

[0169] 1 Battery pack 2 Upper Box 3 Lower Box 4 Battery Module 5 Secondary battery 51 Housing 52 Electrode assembly 53 Top cover

Claims

1. A secondary battery including a positive electrode plate, a negative electrode plate, a separator, and an electrolyte, The positive plate comprises a positive active material including a core and a coating, the manganese content of the core being ≧25% based on the weight of the core, the coating coating a surface of the core and comprising one or more of an oxide, hydroxide or oxysalt of an element X, the element X being selected from one or more of Al, B or P, the weight ratio of the coating to the core being 1:5-100, optionally 1:16-100; A secondary battery, wherein the electrolyte comprises a first solvent, the first solvent being selected from one or more of a fluorocarbonate, a fluorocarboxylate, a fluorosulfone, a fluoroether, or a fluorobenzene.

2. 2. The secondary battery according to claim 1, wherein the manganese ion elution coefficient k of the positive electrode plate is ≦0.035%, optionally k≦0.017%, and further optionally k≦0.01%, and the manganese ion elution coefficient refers to a weight content of manganese ions in the electrolyte after storing the positive electrode plate in a fully charged state and the electrolyte (an injection coefficient of the electrolyte is 5 g / Ah) together at 60° C. for 48 hours.

3. 3. The secondary battery according to claim 1, wherein a stability coefficient of the static protective layer of the positive plate is 54%≦e1≦100%, optionally 70%≦e1≦100%, and further optionally 85%≦e1≦100%, and the stability coefficient of the static protective layer indicates a ratio between a content of the remaining element X in the positive electrode film layer after storing the positive electrode plate in a fully charged state and the electrolyte at 60° C. for 48 hours, and a content of the element X contained in the positive electrode film layer in an initial fully charged state of the positive electrode plate.

4. The stability coefficient e2 of the dynamic protective layer of the positive electrode plate satisfies 20%≦e2≦100%, alternatively 50%≦e2≦100%, and further alternatively 70%≦e2≦100%. The stability coefficient of the dynamic protective layer is such that, when the positive electrode plate and the electrolyte are both fully charged, The secondary battery according to any one of claims 1 to 3, wherein the content of the element X remaining in the positive electrode film layer after storage at 60°C for 48 hours is a ratio of the content of the element X contained in the positive electrode film layer before the storage.

5. The secondary battery according to any one of claims 1 to 4, wherein the content of element X in the positive electrode film layer is 0.05% to 5.35%, optionally 0.1% to 1.61%, and further optionally 0.24% to 1.61%, based on the total weight of the positive electrode active material.

6. The core is LiM ｐ Mn ２－ｐ O ４ , LiN ｑ Mn １－ｑ P.O. ４ Or Li １＋ｔ Mn １－ｗ L ｗ O ２＋ｔ and 0≦p≦1, 0≦q≦ 0.5, 0≦t≦1, 0≦w≦0.5, and M, N, and L each independently represent one or more of Ni, Co, Fe, Cr, V, Ti, Zr, La, Ce, Rb, P, W, Nb, Mo, Sb, B, Al, and Si; More optionally, LiM ｐ Mn ２－ｐ O ４ Or Li １＋ｔ Mn １－ｗ L ｗ O ２＋ｔ one or more of More preferably, LiNi ０．５ Mn １．５ O ４ , LiNi ０．５ Co ０．２ Mn ０．３ O ２ , Li ２ MnO ３ , LiMnPO ４ The secondary battery according to any one of claims 1 to 5, wherein the secondary battery is one or more of the following:

7. The coating is made of alumina, boron oxide, and borate. ａ＋ ｘ [BO ３ ] ３－ ｙ , A being phosphate ａ＋ ｘ [P.O. ４ ] ３－ ｙ or A which is an aluminate ａ＋ ｘ [AlO ２ ] １－ ｚ A represents one or more of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Ni, Fe, Co, Ti, Al, Cr, V, Nb, W, each compound being electrically neutral; and a, x, y and z are selected from 1, 2 or 3; Optionally, Al ２ O ３ , B ２ O ３ , Li ３ B.O. ３ , Li ３ P.O. ４ , Na ３ P.O. ４ Or LiAlO ２ The secondary battery according to any one of claims 1 to 6, wherein the secondary battery is one or more of the following:

8.

9.

10. The content y1 of the first solvent is 10 to 100%, optionally 40 to 100%, and further optionally 80 to 100% based on the total weight of the first solvent and the second solvent. The secondary battery according to claim 9.

11. The content y2 of the second solvent is 0 to 90%, optionally 0 to 60%, and further optionally 0 to 20%, based on the total weight of the first solvent and the second solvent. The secondary battery according to any one of claims 9 to 10.

12. The secondary battery according to claim 11, wherein the content y1 of the first solvent and the content y2 of the second solvent satisfy y1 / y2≧0.66, optionally y1 / y2≧2.33, and further optionally y1 / y2≧4.

13.

14. The content of the film-forming additive is 0.5 to 20%, optionally 1 to 10%, and further optionally 1 to 5%, based on the total weight of the first solvent and the second solvent. The secondary battery according to claim 13.

15.

16. The secondary battery according to any one of claims 1 to 15, wherein the core further comprises a doping element, the doping element being selected from one or more of W, Nb, Sb, Ti, Zr, La, Ce, S, and optionally one or more of W and Nb.

17. The secondary battery as claimed in claim 16, wherein the content of the doping element is 0.05%-5%, optionally 0.1-2%, based on the total weight of the core.

18. The secondary battery according to any one of claims 1 to 17, wherein the particles of the positive electrode active material are single crystal or pseudo single crystal.

19. The secondary battery according to any one of claims 1 to 18, wherein the particle size of the positive electrode active material is 1 to 20 µm, and optionally 3 to 15 µm.

20. 20. The secondary battery according to claim 1, wherein the acidity of the electrolyte is ≦50 ppm, and the purity of each solvent used is ≧99.9%.

21. A battery module comprising the secondary battery according to any one of claims 1 to 20.

22. A battery pack comprising the battery module according to claim 21.

23. An electric device comprising at least one of the secondary battery according to any one of claims 1 to 20, the battery module according to claim 21, or the battery pack according to claim 22.

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