Secondary batteries and battery modules, battery packs, and electrical devices containing them.

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] This application relates to the technical field of lithium batteries, and particularly to secondary batteries, battery modules, battery packs containing the same, and electrical devices.

Background Art

[0002] In recent years, as the application range of lithium-ion batteries has become increasingly wide, people's requirements for the performance of secondary batteries have become increasingly high. One of them is that, especially under high-voltage operating conditions, it is desired that secondary batteries have good storage performance and cycle performance. Therefore, how to provide a secondary battery with good storage performance and cycle performance under high-voltage operating conditions is still a technical problem that needs to be solved by engineers.

Summary of the Invention

Problems to be Solved by the Invention

[0003] This application is made in view of the above problems, and its purpose is to provide a secondary battery having significantly improved storage performance and cycle performance under high-voltage operating conditions.

Means for Solving the Problems

[0004] The first aspect of this application is a secondary battery including a positive electrode plate, a negative electrode plate, a separator, and an electrolyte, the positive electrode plate includes a positive electrode active material including a core and a coating, based on the weight of the core, the manganese content of the core ≧ 25%, the coating covers the surface of the core, and includes one or more of oxides, hydroxides, or oxy-salts of element X, the element X is selected from one or more of Al, B, or P, and the weight ratio of the coating to the core is 1:5 to 100, optionally 1:16 to 100, the electrolyte includes a first solvent, and the first solvent is selected from one or more of fluorocarbonate, fluorocarboxylate, fluorosulfone, fluoroether, or fluorobenzene to provide a secondary battery.

[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 and contributes to the improvement of 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 k ≤ 0.035%, optionally k ≤ 0.017%, and further optionally k ≤ 0.01%. 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 injection coefficient of the electrolyte 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 interfacial stability of the positive electrode can be significantly improved, side reactions at the interface can be reduced, the stability of the secondary battery can be enhanced, and further the storage performance and cycle performance of the secondary battery can be improved.

[0008] In any embodiment, optionally, the stability coefficient e1 of the static protective layer of the positive electrode plate is 54% ≤ e1 ≤ 100%, optionally 70% ≤ e1 ≤ 100%, and further optionally 85% ≤ e1 ≤ 100%. 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 the 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 conditions, the stability of the secondary battery can be further enhanced, 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 more optionally 70% ≤ e2 ≤ 100%. 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 the 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 before the storage.

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

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

[0013] When the content of the element X in the positive electrode film layer is within the above range, the direct contact between the core material and the electrolyte can be effectively reduced, side reactions can be reduced, the elution of manganese ions can be reduced, and the storage performance and cycle performance of the secondary battery can be improved.

[0014] In any embodiment, optionally, the core is selected from one or more of LiM p Mn 2-p O4, LiN q Mn 1-q PO4 or Li 1+t Mn 1-w L w O 2+t where 0 ≤ p ≤ 1, 0 ≤ q ≤ 0.5, 0 ≤ t ≤ 1, 0 ≤ w ≤ 0.5, and M, N, 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, Si. More optionally, LiM p Mn 2-p O4 or Li 1+t Mn 1-w L w O2+t It is one or more of the following: Furthermore, LiNi 0.5 Mn 1.5 O4, LiSa 0.5 Co 0.2 Mn 0.3 It is one or more of O2, Li2MnO3, or LiMnPO4.

[0015] When the core material of a secondary battery is selected from the above types, it can improve the energy density of the secondary battery, reduce manufacturing costs, and minimize environmental pollution.

[0016] In any embodiment, the coating is selectively alumina, boron oxide, or a borate. a+ x [BO3] 3- y A, which is a phosphate a+ x [PO4] 3- y A is an aluminate. a+ x [AlO2] 1- z One or more of the following are selected, where 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 is electrically neutral, and a, x, y, and z are selected from 1, 2, or 3. Selectively, it is one or more of Al2O3, B2O3, Li3BO3, Li3PO4, Na3PO4, or LiAlO2.

[0017] When the coating material is selected from the above-mentioned substances, it contributes to reducing the elution of transition metals, reducing interfacial side reactions, and improving battery performance.

[0018] JPEG0007850286000001.jpg148152

[0019] JPEG0007850286000002.jpg79152

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

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

[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 0-90%, selectively 0-60%, and more selectively 0-20%.

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

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

[0025] JPEG0007850286000003.jpg86152

[0026] The aforementioned film-forming additive preferentially forms a film on the negative electrode, reducing the loss of active lithium and further improving the performance of the battery.

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

[0028] JPEG0007850286000004.jpg51152

[0029] When the electrolyte contains the aforementioned 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, the core optionally further comprises a doping element, the doping element being 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] Elemental doping improves the electrochemical properties of the positive electrode active material, thereby contributing to the improvement of the electrochemical performance of the corresponding secondary battery.

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

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

[0034] When the positive electrode active material is a single crystal, the active material itself is less likely to break down, reducing the probability of exposing new surfaces, further reducing side reactions in the electrolyte, and improving the stability of the electrolyte.

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

[0036] When the particle size of the positive electrode active material falls within the above range, it helps to avoid increased energy consumption in the process and deterioration of the processing performance of the positive electrode plate due to excessively large particle size.

[0037] In any embodiment, the acidity of the electrolyte is selectively ≤ 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 range, the electrolyte has good stability, is less prone to side reactions, and contributes to improving the cycle performance of the secondary battery.

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

[0040] A third aspect of the present application provides a battery pack including a 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 electrical device comprising at least one selected from a secondary battery according to the first aspect of the present application, a battery module according to the second aspect of the present application, or a battery pack according to the third aspect of the present application. [Effects of the Invention]

[0042] In the secondary battery described in this application, the positive electrode active material includes a core and a coating that covers the surface of the core, with a weight ratio of 1:5 to 100 for the coating to the core. An appropriate weight ratio of coating to core helps to effectively reduce direct contact between the core material and the electrolyte, reduce interfacial side reactions, and improve the storage and cycle performance of the secondary battery, while also avoiding the deterioration of the dynamic performance of the secondary battery due to excessive coating. Furthermore, the coating itself is also a high-speed ion conductor, and does not significantly reduce the overall capacity of the positive electrode active material, contributing to the secondary battery having a high energy density. In addition, the electrolyte in the secondary battery of this application contains a first solvent selected from fluorinated solvents, thereby improving the degree of fluorination of the electrolyte, enhancing the compatibility between the electrolyte and the positive and negative electrodes, reducing the breakdown of the electrolyte on the positive and negative electrode materials, and further contributing to the improvement of the storage and cycle performance of the secondary battery.

[0043] The battery module, battery pack, and electrical device of this application include a secondary battery provided by this application and therefore have at least the same advantages as a secondary battery. [Brief explanation of the drawing]

[0044] [Figure 1] Figure 1 is a schematic diagram of a secondary battery according to one embodiment of the present invention. [Figure 2] Figure 2 is an exploded view of a secondary battery according to one embodiment of the present invention shown in Figure 1. [Figure 3] Figure 3 is a schematic diagram of a battery module according to one embodiment of the present invention. [Figure 4] Figure 4 is a schematic diagram of a battery pack according to one embodiment of the present invention. [Figure 5] Figure 5 is an exploded view of a battery pack according to one embodiment of the present invention shown in Figure 4. [Figure 6] Figure 6 is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of the present invention. [Modes for carrying out the invention]

[0045] Hereinafter, embodiments specifically disclosing the secondary battery, battery module, battery pack, and electrical device of the present application will be described in detail with appropriate reference to the drawings. However, unnecessary details may be omitted. For example, detailed explanations of well-known matters and redundant explanations of substantially the same structures may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to ensure that it is easily understood by those skilled in the art. Furthermore, the drawings and the following explanation are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the essence of the claims.

[0046] The “range” disclosed herein is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundary of the given range. The range thus limited may include the values ​​at both ends, or it may not include the values ​​at both ends, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60~120 and 80~110 are listed for a given parameter, it is understood that the ranges 60~110 and 80~120 are also expected. 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 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 are all expected. In this application, unless otherwise stated, the numerical range “a~b” represents an abbreviated expression for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are listed in this specification, and "0 to 5" is simply an abbreviated representation of combinations of these numbers. Furthermore, when it is stated that a parameter is an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0047] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0048] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0049] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably in order. For example, if it is mentioned that the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, if 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), or steps (a), (c) and (b), or steps (c), (a) and (b).

[0050] Unless otherwise specified, the terms “include” and “incorporate” as used herein may be in open-ended form or closed-ended form. For example, “include” and “incorporate” may further include or incorporate other components not listed, or may include or incorporate only the listed components.

[0051] Unless otherwise specified, the term “or” is inclusive in this application. 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 both A and B are true (or exist).

[0052] In this application, the term "fully charged state" refers to the state in which a secondary battery has been charged to its upper cutoff voltage. Similarly, the term "initial fully charged state" refers to the state in which a secondary battery has been charged to its upper cutoff voltage after manufacturing is complete and the electrolyte does not contain manganese.

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

[0054] The inventors discovered in actual operation that when a secondary battery operates at high voltages such as 4.2V or higher, the leaching of transition metals from the positive electrode active material becomes severe, degrading the storage and cycle performance of the secondary battery. After numerous experiments, the inventors discovered that if the positive electrode active material includes a core and a coating that covers 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 and cycle performance of the secondary battery can be enhanced. Furthermore, if the electrolyte contains a first solvent selected from fluorinated solvents, the compatibility between the electrolyte and the positive and negative electrodes can be improved, further enhancing the stability of the secondary battery under high-voltage operating conditions and improving the performance of the secondary battery.

[0055] After further intensive research, the inventors discovered that if 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 significantly improved, and the storage performance and cycle performance of the secondary battery can be enhanced.

[0056] [Secondary battery] A first aspect of the present application is a secondary battery comprising a positive electrode plate, a negative electrode plate, a separator, and an electrolyte, The positive electrode plate comprises a positive electrode active material including a core and a coating, with a manganese content of the core ≥ 25% based on the weight of the core, the coating covering the surface of the core and containing one or more of the oxides, hydroxides, or oxysalts of element X, where element X is selected from one or more of Al, B, or P, and the weight ratio of the coating to the core is 1:5 to 100, selectively 1:16 to 100. The electrolyte comprises a first solvent, the first solvent being selected from one or more of fluorocarbonates, fluorocarboxylates, fluorosulfones, fluoroethers, or fluorobenzenes to provide a secondary battery.

[0057] In the secondary battery described in this application, the positive electrode active material includes a core and a coating that covers the surface of the core, with a weight ratio of 1:5 to 100 for the coating to the core. An appropriate weight ratio of coating to core helps to effectively reduce direct contact between the core material and the electrolyte, reduce interfacial side reactions, and improve the storage and cycle performance of the secondary battery, while also avoiding the deterioration of the dynamic performance of the secondary battery due to excessive coating. Furthermore, the coating itself is also a high-speed ion conductor, and does not significantly reduce the overall capacity of the positive electrode active material, contributing to the secondary battery having a high energy density. In addition, the electrolyte in the secondary battery of this application includes a first solvent selected from fluorinated solvents, thereby improving the degree of fluorination of the electrolyte, enhancing the compatibility between the electrolyte and the positive and negative electrodes, reducing the breakdown of the electrolyte on the positive and negative electrode materials, and further contributing to the improvement of the storage and cycle performance of the secondary battery.

[0058] In some embodiments, the manganese ion elution coefficient of the positive electrode plate is selectively k ≤ 0.035%, selectively k ≤ 0.017%, and even more selectively k ≤ 0.01%, where the manganese ion elution coefficient refers to the weight content of manganese ions in the electrolyte after storing the fully charged positive electrode plate and the electrolyte (with an electrolyte injection coefficient of 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 interfacial stability of the positive electrode is significantly improved, interfacial side reactions are reduced, the stability of the secondary battery is enhanced, and the storage performance and cycle performance of the secondary battery can be further improved.

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

[0061] The stability coefficient e1 of the static protective layer can suitably reflect the degree of dissolution of element X in the electrolyte in the positive electrode film layer. When the stability coefficient of the static protective layer satisfies the above conditions, the secondary battery has good stability, contributing to improved 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 is unknown beforehand, after using the secondary battery for a certain period of time, the stability coefficient of the static protective layer Let me explain why it becomes more 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 electrolyte in the positive electrode film layer. A larger stability coefficient e2 of the dynamic protective layer indicates a smaller dissolution rate of element X in the electrolyte in the positive electrode film layer, indicating higher stability of the secondary battery. Conversely, a larger dissolution rate indicates lower stability of the secondary battery.

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

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

[0065] Typically, 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 into and removed from the positive and negative electrode plates. The electrolyte plays a role in conducting ions between the positive and negative electrode plates. The separator is provided between the positive and negative electrode plates and primarily serves to prevent short circuits between the positive and negative electrodes while simultaneously allowing ions to pass through. The positive electrode plate, negative electrode plate, electrolyte, and separator described in this application will be explained 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] For example, a positive electrode current collector has two opposing surfaces in the thickness direction of itself, and the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

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

[0069] In some embodiments, the core in the positive electrode active material described herein is selectively LiM p Mn 2-p O4, LiN q Mn 1-q PO4 or Li 1+t Mn 1-w L w O 2+tOne or more of the following are selected, 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, Si, Furthermore, LiM p Mn 2-p O4 or Li 1+t Mn 1-w L w O 2+t It is one or more of the following: Furthermore, LiNi 0.5 Mn 1.5 O4, LiSa 0.5 Co 0.2 Mn 0.3 It is one or more of O2, Li2MnO3, or LiMnPO4.

[0070] When the core material of a secondary battery is selected from the above types, it can improve the energy density of the secondary battery, reduce manufacturing costs, and minimize environmental pollution.

[0071] In some embodiments, the coating in the positive electrode active material described in this application is selectively alumina, boron oxide, or a borate. a+ x [BO3] 3- y A, which is a phosphate a+ x [PO4] 3- y A is an aluminate. a+ x [AlO2] 1- z One or more of the following are selected, and A is Li, Na, K, Rb, Cs, The compounds represent one or more of Mg, Ca, Ba, Ni, Fe, Co, Ti, Al, Cr, V, Nb, and W, and each compound is electrically neutral, with a, x, y, and z selected from 1, 2, or 3. Selectively, it is one or more of Al2O3, B2O3, Li3BO3, Li3PO4, Na3PO4, or LiAlO2.

[0072] When the coating material is selected from the above-mentioned substances, it reduces the elution of transition metals, minimizes interfacial side reactions, and contributes to improving the performance of the battery. Furthermore, the coating material itself is a high-speed ion conductor, and does not significantly reduce the overall capacity of the positive electrode active material, thus contributing to the secondary battery having a high energy density.

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

[0074] When the content of element X in the positive electrode film layer is within the above range, direct contact between the core material and the electrolyte can be effectively reduced, side reactions can be reduced, manganese ion elution can be reduced, and the storage performance and cycle performance of the secondary battery can be improved.

[0075] In some embodiments, the core is selectively further comprising doping elements, the doping elements being selected from one or more of W, Nb, Sb, Ti, Zr, La, Ce, and S, and selectively one or more of W and Nb.

[0076] Elemental doping improves the electrochemical properties of the positive electrode active material, thereby contributing to the improvement of the electrochemical performance of the corresponding secondary battery.

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

[0078] In some embodiments, the particles of the positive electrode active material are selectively single crystals or pseudo-single crystals.

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

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

[0081] When the particle size of the positive electrode active material falls within the above range, it helps to avoid increased energy consumption in the process and deterioration of the processing performance of the positive electrode plate due to excessively large particle size.

[0082] In some embodiments, the positive electrode active material selectively accounts for 85–99% and selectively 93–97% of the total weight of the positive electrode film layer. For example, the positive electrode active material may account for 85%, 90%, 95.5%, or 97% of the total weight of the positive electrode film layer.

[0083] In some embodiments, the cathode film layer selectively further comprises 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 resins.

[0084] In some embodiments, the binder selectively accounts for 0.1–3.5% and selectively for 0.5–2.5% of the total weight of the cathode film layer.

[0085] In some embodiments, the cathode film layer selectively further comprises a conductive agent. As an example, the conductive agent may include 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 selectively accounts for 0.05 to 5% of the total weight of the positive electrode film layer, and selectively accounts for 0.5 to 3%.

[0087] In some embodiments, a positive electrode plate can be manufactured by the following method: Components for manufacturing the positive electrode plate described above, such as a positive electrode active material, a conductive agent, a 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 electrode 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] For example, the negative electrode current collector has two opposing surfaces in the thickness direction of itself, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

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

[0091] In some embodiments, the negative electrode active material can be a negative electrode active material known in the art for batteries. For example, the negative electrode active material may include at least one of the following materials: 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 elemental silicon, silicon oxygen 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 conventional materials used as negative electrode active materials for batteries may be used. These negative electrode active materials may be used individually or in combination of two or more.

[0092] In some embodiments, the negative electrode film layer selectively further comprises a binder. The binder 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 further selectively comprises a conductive agent. The conductive agent can 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 film layer selectively further comprises other additives, such as a thickener (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0095] In some embodiments, a negative electrode plate can be manufactured by the following method: Components for manufacturing the negative electrode plate, such as a negative electrode active material, a conductive agent, a 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 plays a role in conducting ions between the positive and negative electrodes. Typically, the electrolyte contains an electrolyte salt and a solvent.

[0097] JPEG0007850286000005.jpg164152

[0098] When the electrolyte contains the first solvent described above, it improves the stability of the electrolyte, improves the compatibility between the electrolyte and the positive and negative electrodes, and contributes to improving the storage performance and cycle performance of the secondary battery.

[0099] JPEG0007850286000006.jpg76152

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

[0101] In some embodiments, the content y1 of the first solvent is selectively 10-100%, selectively 40-100%, and more selectively 80-100%, based on the total weight of the first and second solvents. For example, the content y1 of the first solvent is 40%, 70%, 80%, 95%, or 100% is also acceptable.

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

[0103] When the contents of the first and second solvents are within the above range, the stability of the electrolyte is further improved, contributing to improved storage performance and cycle performance of the secondary battery.

[0104] In some embodiments, the sum of the weights of the first solvent and the second solvent selectively accounts for 60-90% and selectively 60-87.5% of the total weight of the electrolyte of the present invention.

[0105] When the weight percentage of the sum of the weights of the first solvent and the second solvent in relation to the electrolyte of this application falls within the above range, it contributes to further improving the stability of the electrolyte.

[0106] In some embodiments, the content y1 of the first solvent and the content y2 of the second solvent are selectively such that y1 / y2 ≥ 0.66, selectively y1 / y2 ≥ 2.33, and even more selectively 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 more favorable electrochemical stability, further improves the compatibility between the electrolyte and the positive and negative electrodes, reduces side reactions, and helps to improve the storage performance and cycle performance of the secondary battery.

[0108] JPEG0007850286000007.jpg19152

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

[0110] In some embodiments, the electrolyte salt in the electrolyte can be selectively selected from at least one of lithium hexafluoride phosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoride arsenate, 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 selectively 5-50% by weight, and selectively 8-40% by weight, based on the total weight of the electrolyte.

[0112] When the electrolyte contains the above-mentioned lithium salt at a suitable concentration, the viscosity of the electrolyte is appropriate, improving its conductivity and contributing to further enhancing the performance of the secondary battery. However, if the concentration of lithium salt in the electrolyte is too high, the overall concentration of the electrolyte increases, but the degree of dissociation of the salt in the electrolyte decreases, the viscosity of the electrolyte also increases, and conversely, the conductivity of the electrolyte decreases.

[0113] JPEG0007850286000008.jpg81152

[0114] The film-forming additive preferentially forms a film on the negative electrode, reducing the loss of active lithium and further improving the storage and cycle performance of the secondary battery.

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

[0116] JPEG0007850286000009.jpg50152

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

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

[0119] In some embodiments, the acidity of the electrolyte is selectively ≤ 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 range, the electrolyte has good stability, is less prone to side reactions, and contributes to improving the cycle performance of the secondary battery.

[0121] The acidity of the electrolyte in this application can be tested by methods commonly used in the art. Specifically, referring to HG / T4067-2015, it should be explained that the free acid in the electrolyte can be titrated using a triethylamine standard solution.

[0122] In some embodiments, the electrolyte injection coefficient in the secondary battery described in this application is selectively 1.8 to 4 g / Ah, and selectively 2.4 to 3.2 g / Ah. For example, if the electrolyte injection coefficient of the secondary battery is 2.8 g / Ah and the cell capacity is designed to be 3 Ah, the amount of electrolyte injected is 2.8 * 3 g = 8.4 g.

[0123] It should be explained that the electrolyte described in this application can be manufactured by methods commonly used by those skilled in the art, so that it can be understood by those skilled in the art. For example, the electrolyte described in this application can be manufactured by mixing a first solvent, a second solvent, a lithium salt, a film-forming additive, and other additives in a fixed proportion under the protection of an inert gas and stirring them uniformly.

[0124] [Separator] In some embodiments, the secondary battery further includes a separator. The present application does not particularly limit the type of separator, and any known porous separator having good chemical 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 may be a single-layer film or a multilayer composite film, and is not particularly limited. If the separator is a multilayer composite film, the materials of each layer may be the same or different, and are not particularly limited.

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

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

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

[0129] As an electrical device, a secondary battery, battery module, or battery pack can be selected according to the user's needs.

[0130] Furthermore, the secondary battery, battery module, battery pack, and electrical device of this application will be described below with appropriate reference to the drawings.

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

[0132] In some embodiments, the secondary battery may include an outer casing. This casing can be used to package the electrode assembly and the electrolyte.

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

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

[0135] In some embodiments, referring to Figure 2, the casing may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates enclose each other to form a housing chamber. The case 51 has an opening that communicates with the housing chamber, and the cover plate 53 may cover the opening to seal the housing chamber. The positive electrode plate, negative electrode plate, and separator can be formed into an electrode assembly 52 by a winding or lamination process. The electrode assembly 52 is packaged inside the housing chamber. The electrolyte permeates the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 may be one or more, and a person skilled in the art can select them 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 may be one or more, and the specific number can be selected by those skilled in the art depending on the application and capacity of the battery module.

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

[0138] Selectively, the battery module 4 may further include a housing having a housing space, and a plurality of secondary batteries 5 are housed in said housing space.

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

[0140] Figures 4 and 5 show an example of a battery pack 1. Referring to Figures 4 and 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 includes an upper box 2 and a lower box 3, the upper box 2 covering the lower box 3 and forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any configuration.

[0141] Figure 6 shows an example of an electrical device. This electrical device is a secondary battery electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power output and high energy density requirements for the secondary battery of this electrical device, a battery pack or battery module can be used.

[0142] Other examples of devices may include mobile phones, tablets, and laptop computers. These devices typically require lightweight and thin designs, and can utilize rechargeable batteries as their power source.

[0143] Examples Examples of the present application are described below. The examples described below are illustrative and are for interpretation purposes only, and should not be understood as limiting the present application. Unless otherwise specified in the examples, specific techniques or conditions are described in the art literature or in accordance with product specifications. Unless otherwise specified, the reagents or equipment used are all commercially available, common products.

[0144] The weight-average molecular weight of polyvinylidene fluoride (PVDF) used in the embodiments of this application is approximately 900,000, and the purity of all solvents used in the embodiments of this application is greater than 99.9%. Unless otherwise specified, the weights of the substances used in the embodiments of this application are based on weights excluding crystal water.

[0145] Example 1 (Manufacturing of positive electrode active material) LiRing 0.5 Mn 1.5 O4 was added to an appropriate amount of deionized water and mixed thoroughly with a stirring to form a suspension. Next, Li3PO4 was added to the suspension and stirred thoroughly until homogeneous. Subsequently, filtration and drying were performed to obtain a solid powder. The obtained solid powder was treated at 650°C for 8 hours to obtain LiNi with a surface coated with Li3PO4. 0.5 Mn 1.5 O4 was obtained. Based on the total weight of the obtained positive electrode active material, the P element content in the coating was 0.50%.

[0146] Aside from differences in the types of substances added and the content of the corresponding elements, the methods for producing the positive electrode active material in the comparative examples and other examples were the same as those described above.

[0147] (Manufacturing of positive electrode plates) The positive electrode active material obtained in the previously described steps, the conductive agent carbon black (Super P), and the binder polyvinylidene fluoride (PVDF) were thoroughly mixed in an appropriate amount of NMP solvent in a mass ratio of 95.5:2.5:2 to form a uniform positive electrode slurry. This slurry was then uniformly applied to the surface of the aluminum foil of the positive electrode current collector, coating both sides. After drying and cold pressing, a positive electrode plate was obtained. The amount of positive electrode active material supported on one side of the positive electrode current collector was 0.020 g / cm³. 2 That was the case.

[0148] (Manufacturing of negative electrode plates) Artificial graphite as the negative electrode active material, carbon black (Super P) as the conductive agent, styrene-butadiene rubber as the binder, and sodium carboxymethylcellulose as the thickener were thoroughly mixed in an appropriate amount of deionized water as the solvent in a mass ratio of 96:1:1:2 to form a uniform negative electrode slurry. This slurry was then uniformly applied to the surface of the copper foil of the negative electrode current collector, covering one side. After drying and cold pressing, a negative electrode plate was obtained. The amount of negative electrode active material supported on one side of the negative electrode current collector was 0.008 g / cm³. 2 That was the case.

[0149] (Manufacturing of electrolyte) In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), various organic solvents were uniformly mixed in the mass ratios shown in Table 1, the salts and additives shown in Table 1 were added, and the mixture was uniformly stirred to obtain the electrolyte of Example 1.

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

[0151] (Manufacturing of secondary batteries) The positive electrode plate, separator, and negative electrode plate were stacked in order, with the separator interposed between the positive and negative electrode plates to act as a separator. The electrode assembly was placed in a battery case, dried, and then the electrolyte was injected. Further processes such as chemical conversion and settling were followed to manufacture the secondary battery of Example 1. The size of the secondary battery was 60 × 130 × 4 mm, and the size of the corresponding positive and negative electrode plates was both 87 × 700 mm. The electrolyte injection coefficient was The reading was 2.8 g / Ah.

[0152] Examples 2-20 and Comparative Examples 1-3 Aside from the conditions shown in Table 1, the other conditions for Examples 2-20 and Comparative Examples 1-3 were the same as in Example 1.

[0153] (Testing methods for related parameters) 1. Testing cell capacity (C) At 25°C, the lithium-ion battery was charged with a constant current of 0.1C up to the upper cutoff voltage, then charged with a constant voltage at this voltage until the current fell below 0.05C, and then discharged at 0.1C up to the lower cutoff voltage to obtain the discharge capacity C (Ah).

[0154] 2. Testing of manganese ion elution coefficient and protective layer stability coefficient At 25°C, lithium-ion batteries (two parallel samples) were charged with a constant current of 0.1C up to the upper cutoff voltage, then charged with a constant voltage at this voltage until the current fell below 0.05C, and subsequently disassembled in a glove box. The positive electrode plate of one of the lithium batteries was immersed in dimethyl carbonate for 1 hour three times (the dimethyl carbonate was replaced immediately after each immersion for the next immersion), and after drying, an elemental content test was performed to obtain the weight-based content of element X in the positive electrode film layer, which was defined as x1.

[0155] For the other parallel sample, the positive electrode plate was removed using a similar method, then added to the corresponding 5 g / Ah electrolyte (components shown in Table 1), sealed, and left to stand in a 60°C oven for 48 hours. The corresponding electrolyte was then removed in a glove box, followed by an elemental content test 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 defined as y1. Accordingly, the stored positive electrode plate was immersed in dimethyl carbonate for 1 hour three times (the dimethyl carbonate was replaced immediately after each immersion was completed before the next immersion), and then dried before performing an elemental content test to obtain the weight-based content of element X in the positive electrode film layer, which was defined as x2. In this case, the manganese ion elution coefficient of the secondary battery is k=y1, and the stability coefficient of the protective layer is e=x2 / x1.

[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 method for measuring the stability coefficient of the protective layer described above. The distinction is that when measuring the stability coefficient e1 of the static protective layer, the secondary battery used is a newly manufactured secondary battery, but when measuring the stability coefficient e2 of the dynamic protective layer, the secondary battery used 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 this application, newly manufactured secondary batteries were 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 and element X content in the cathode film layer were tested by inductively coupled plasma atomic emission spectroscopy, with instrument specifications referring to EPA6010D-2014 "Inductively Coupled Plasma Atomic Emission Spectroscopy" and JY / T015-1996 "General Rules for Inductively Coupled Plasma Atomic Emission Spectroscopy."

[0158] The manganese and element X (B or P) content in the positive electrode film layer can be measured by punching out small circular discs with a radius of 7 mm from the positive electrode plate, weighing six of these discs, defining the corresponding weight as m1, adding 10 ml of aqua regia, heating to completely dissolve the mixture, and then adding deionized water to a final volume of 100 ml. This solution is then tested by inductively coupled plasma atomic emission spectroscopy to obtain the element X content in the corresponding six circular discs, which is defined as m2. Additionally, the positive electrode plate substrate (aluminum substrate), which consists of the corresponding six 7 mm radius circular discs, is taken and its mass is measured, which is defined as m3. In this case, the corresponding element X content is x1 = m2 / (m1 - m3).

[0159] When element X is aluminum, the test method for determining the X content in the positive electrode active material is slightly different. The active material is scraped off the electrode plate surface (care should be taken not to scrape off the aluminum substrate), the mass of the scraped mixture is measured and designated as m4, and then the mass of X in the mixture is measured using the same method as above and designated as m2. In this case, the content of the corresponding element X (Al) is m2 / m4.

[0160] The test method for manganese ion content in the electrolyte is as follows: Take approximately 1 g of electrolyte, add 10 ml of concentrated HNO3 acid (mass fraction 68%), and then... The solution was heated at 180°C for 30 minutes, followed by dilution with deionized water until it reached a final volume of 50 ml. This solution was tested by inductively coupled plasma atomic emission spectroscopy, and the weight-based content of manganese ions (manganese element) in the corresponding electrolyte was finally measured. This was then divided by the mass of the electrolyte to obtain the weight content of manganese ions (manganese element) in the electrolyte, which was defined as y1.

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

[0162] The initial discharge gram capacity (mAh / g) of the positive electrode active material is calculated as: Initial discharge capacity of the secondary battery / Total mass of the positive electrode active material.

[0163] 4. Cycle performance testing of secondary batteries At 45°C, the secondary battery is charged with a constant current of 0.1C up to the upper cutoff voltage, then charged with a constant voltage until the current reaches 0.05C at this cutoff voltage, left to stand for 5 minutes, and then discharged with a constant current of 0.1C up to the lower cutoff voltage. This constitutes one charge-discharge cycle, and the discharge capacity at this point is the initial discharge capacity of the secondary battery. The charge-discharge cycle is repeated for the secondary battery according to the above method until the discharge capacity after the cycle has decayed to 80% of the initial discharge capacity, and the test is completed. The number of cycles of the secondary battery at this point is recorded. A higher number of cycles indicates a longer expected cycle life of the secondary battery.

[0164] 5. Storage performance test of secondary batteries At 25°C, the secondary battery was charged with a constant current of 0.1C up to the upper cutoff voltage, and then charged with a constant voltage of 0.05C at this cutoff voltage until the current was 0.05C, at which point the secondary battery was fully charged. The fully charged secondary battery was stored in a 25°C environment, and every 5 days it was removed and discharged with a constant current of 0.1C up to the lower cutoff voltage. The discharge amount after a certain period of storage was obtained, and then the secondary battery was fully charged as described above and stored again in a 25°C environment until the discharge capacity after storage had decreased to 80% of the initial discharge capacity. The test was then completed, and the total number of days the secondary battery was stored was recorded. A longer number of days the secondary battery is stored indicates a longer expected storage life at room temperature.

[0165] In each of the performance tests described above, it should be noted that the upper cutoff voltage in the examples and comparative examples was 4.95V and the lower cutoff voltage was 3.0V. Table 1 shows the performance test results for Examples 1-20 and Comparative Examples 1-3.

[0166] [Table 1] JPEG0007850286000011.jpg251156 Table 1 (continued) JPEG0007850286000012.jpg251160JPEG0007850286000013.jpg251148

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

[0168] It should be noted that this application is not limited to the embodiments described above. The embodiments described above are merely examples, and all embodiments that have substantially the same configuration as the technical idea and exhibit the same function and effect within the scope of the technical solution of this application are included within the technical scope of this application. Furthermore, other forms that are constructed by adding various modifications to the embodiments that a person skilled in the art could conceive of, and by combining some of the components of the embodiments, are also included within the scope of this application, as long as they do not deviate from the spirit of this application. [Explanation of Symbols]

[0169] 1 Battery pack 2. Top box 3. Lower box 4 Battery Modules 5 Secondary battery 51 Housing 52 Electrode assembly 53 Top Cover

Claims

1. A secondary battery comprising a positive electrode plate, a negative electrode plate, a separator, and an electrolyte, The positive electrode plate comprises a positive electrode active material including a core and a coating, wherein the manganese content of the core is ≥ 25% based on the weight of the core, the coating covers the surface of the core and includes one or more of oxides, hydroxides, or oxysalts of element X, where element X is selected from one or more of Al, B, or P, and the weight ratio of the coating to the core is 1:5 to 100. The electrolyte comprises a first solvent, the first solvent being selected from one or more of fluorocarbonates, fluorocarboxylates, fluorosulfones, fluoroethers, or fluorobenzenes. The positive electrode active material particles are single crystals or pseudo-single crystals in a secondary battery.

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

3. The secondary battery according to claim 1, wherein the stability coefficient of the static protective layer of the positive electrode plate is 54% ≤ e1 ≤ 100%, and the stability coefficient of the static protective layer refers to the ratio of the content of element X remaining in the positive electrode film layer after the positive electrode plate and the electrolyte are stored together at 60°C for 48 hours in a fully charged state to the content of element X contained in the positive electrode film layer in the initial fully charged state of the positive electrode plate.

4. The secondary battery according to any one of claims 1 to 3, wherein the stability coefficient e2 of the dynamic protective layer of the positive electrode plate satisfies 20% ≤ e2 ≤ 100%, and the stability coefficient of the dynamic protective layer refers to the ratio of the content of element X remaining in the positive electrode film layer after storing the positive electrode plate and the electrolyte together at 60°C for 48 hours in a fully charged state to the content of element X contained in the positive electrode film layer before storage.

5. The secondary battery according to claim 3, wherein the content of element X in the positive electrode film layer is 0.05% to 5.35% 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 PO ４ or Li １＋ｔ Mn １－ｗ LwO ２＋ｔ selected from one or more of them, where 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, Si. The secondary battery according to any one of claims 1 to 3.

7. The secondary battery according to claim 6, wherein the core is one or more of LiNi 0.5 Mn 1.5 O 4, Li 2 MnO 3, and LiMnPO 4.

8. The aforementioned coating is alumina, boron oxide, and borate A. ａ＋ ｘ [BO ３ ] ３－ ｙ A, which is a phosphate ａ＋ ｘ [PO ４ ] ３－ ｙ A is an aluminate. ａ＋ ｘ [AlO ２ ] １－ ｚ A secondary battery according to any one of claims 1 to 3, wherein one or more of the following are selected, 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 is electrically neutral, and a, x, y, and z are selected from 1, 2, or 3.

9. The secondary battery according to claim 8, wherein the coating is one or more of Al₂O₃, B₂O₃, Li₃BO₃, Li₃PO₄, Na₃PO₄, or LiAlO₂.

10.

11.

12. The secondary battery according to any one of claims 1 to 3, wherein the electrolyte further comprises a second solvent, the second solvent being selected from one or more nonfluorocarbonates, nonfluorocarboxylates, nonfluoroethers, or nonfluorosulfones.

13.

14. The secondary battery according to claim 12, wherein the second solvent is one or more of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate.

15. The secondary battery according to claim 12, wherein the content y1 of the first solvent is 10 to 100% based on the total weight of the first solvent and the second solvent.

16. The secondary battery according to claim 12, wherein the content y2 of the second solvent is 0 to 90% based on the total weight of the first solvent and the second solvent.

17. The secondary battery according to claim 16, wherein the content y1 of the first solvent and the content y2 of the second solvent satisfy y1 / y2 ≥ 0.

66.

18. The secondary battery according to claim 12, wherein the electrolyte further comprises a film-forming additive, the film-forming additive being selected from one or more of linear or cyclic sulfate esters, linear or cyclic sulfonic acid esters, linear or cyclic carbonate esters, polycyclic sulfate esters, or polycyclic sulfonic acid esters.

19.

20. The secondary battery according to claim 18, wherein the content of the film-forming additive is 0.5 to 20% based on the total weight of the first solvent and the second solvent.

21.

22. The secondary battery according to any one of claims 1 to 3, 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, and S.

23. The secondary battery according to claim 22, wherein the content of the doping element is 0.05% to 5% based on the total weight of the core.

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

25. A secondary battery according to any one of claims 1 to 3, wherein the acidity of the electrolyte is ≤ 50 ppm and the purity of each solvent used is ≥ 99.9%.

26. A battery module comprising a secondary battery according to any one of claims 1 to 3.

27. A battery pack comprising the battery module described in claim 26.

28. An electrical device including the battery pack described in claim 27.

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