Secondary batteries and electrical devices containing them

Abstract

This application provides a secondary battery comprising a positive electrode plate and an electrolyte, wherein the positive electrode plate comprises a current collector and a positive electrode material layer provided on at least one side of the current collector, the positive electrode material layer comprises a first lithium iron phosphate material and a second lithium iron phosphate material, the Dv50 of the second lithium iron phosphate material being greater than the Dv50 of the first lithium iron phosphate material and the Dv50 of the first lithium iron phosphate material being 0.05 μm to 6 μm, the electrolyte comprising a solvent, the solvent comprising at least one first solvent selected from compounds of formula I, and R1 and R2 being independently selected from C1-C6 alkyl and C1-C6 haloalkyl, respectively. The secondary battery of this application has well-balanced and good overall performance. [Formula 1] JPEG2026512564000038.jpg2370

Description

Technical Field

[0001] This application relates to the technical field of lithium batteries, and particularly to secondary batteries and electrical devices including such secondary batteries.

Background Art

[0002] In recent years, lithium-ion secondary batteries have been widely applied in many fields such as energy storage power systems such as hydraulic, thermal, wind, and solar power generation plants, as well as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. With the development of lithium-ion secondary batteries, especially as they are widely used in daily life, users hope to achieve faster battery charging to meet the needs of the fast-paced modern life, so there are higher requirements for the fast charging performance of lithium-ion secondary batteries.

[0003] There is a need for lithium-ion secondary batteries with good fast charging performance in the art.

Summary of the Invention

[0004] This application is made in view of the above problems, and its purpose is to provide a fast charging secondary battery and an electrical device with good performance.

[0005] To achieve the above object, this application provides a secondary battery, the secondary battery includes a positive electrode plate and an electrolytic solution, the positive electrode plate includes a current collector and a positive electrode material layer provided on at least one side of the current collector, the positive electrode material layer includes a first lithium iron phosphate material and a second lithium iron phosphate material, the Dv50 of the second lithium iron phosphate material is larger than the Dv50 of the first lithium iron phosphate material, and the Dv50 of the first lithium iron phosphate material is 0.05 μm to 6 μm. The electrolytic solution includes a solvent, and the solvent includes a first solvent selected from at least one of the compounds of Formula I.

Chemical Formula

[0006] The secondary battery of the present application has improved fast charging ability. At the same time, the secondary battery of the present application further has good cycle performance and a low gas generation amount during storage (that is, a low volume expansion rate and excellent safety performance). In view of this, the present application provides a fast charging lithium ion secondary battery with good overall performance.

[0007] In any embodiment, the Dv50 of the first lithium iron phosphate material is 0.05 μm to 4 μm, optionally 1 μm to 4 μm, and more optionally 2 μm to 4 μm. By selecting the first lithium iron phosphate material within this Dv50 range, it further contributes to improving the fast charging performance of the battery, reducing the volume expansion rate, and achieving good cycle performance. <000,0098>

[0008] In any embodiment, based on the total weight of the first and second lithium iron phosphate materials, the content W1 of the first lithium iron phosphate material is 2% to 80% by weight, optionally 20% to 60% by weight, and more optionally 20% to 40% by weight. By including the first lithium iron phosphate material within the above content range in the positive electrode material layer, it further contributes to the secondary battery having a balanced good overall performance such as improved fast charging performance and cycle performance, and a reduced volume expansion rate.

[0009] In any embodiment, R1 and R2 are each independently selected from C1-C4 alkyl and C1-C4 haloalkyl, and are optionally selected from methyl, ethyl, propyl, fluoromethyl, fluoroethyl, and fluoropropyl.

[0010] In any embodiment, the compound of formula I is

Chemical formula

Chemical formula

[0011] By selecting the first solvent described above, improvements in the viscosity and conductivity of the electrolyte are achieved, further contributing to improvements in the fast charging performance and cycle performance of the secondary battery.

[0012] In any embodiment, based on the total weight of the solvent, the content W2 of the first solvent is 20% to 80% by weight, selectively 30% to 70% by weight, and more selectively 50% to 70% by weight. By controlling the weight percentage of the first solvent within the above range, it is possible to provide secondary batteries with excellent overall performance, such as ideal fast charging performance, cycle performance, and a low volume expansion rate.

[0013] In any embodiment, the Dv50 of the first lithium iron phosphate material, its content W1, and the content W2 of the first solvent are: The relationship t = (W1 × W2) / Dv50 is satisfied, 0.0006 ≤ t ≤ 12.8, selectively 0.015 ≤ t ≤ 0.14, and more selectively 0.03 ≤ t ≤ 0.12, The unit for Dv50 is μm, and both W1 and W2 are weight percentages.

[0014] When t is within the above range, it is possible to ensure that the cell has good fast charging performance without worsening gas generation during storage.

[0015] In any embodiment, the electrolyte further comprises an additive, the additive comprising a sultone of formula II and / or a sulfate ester of formula III. [ka] p is 1, 2 or 3, and optionally 1, R 11 and R 12 are each independently selected from a hydrogen atom, a halogen atom, C1-C6 alkyl, C1-C3 haloalkyl, C1-C3 alkoxy and C1-C3 haloalkoxy, and optionally, R 11 and R 12 are each independently selected from a hydrogen atom, a halogen atom, C1-C3 alkyl, C1-C3 haloalkyl, and more optionally, R 11 is a hydrogen atom, R 12 is a hydrogen atom, C1-C3 alkyl or a halogen atom, R 13 and R 14 are each independently selected from a hydrogen atom, a halogen atom, C1-C6 alkyl, C1-C6 haloalkyl, C1-C6 alkoxy and C1-C3 haloalkoxy, and optionally, R 13 and R 14 are each independently selected from a hydrogen atom, a halogen atom, C1-C3 alkyl, C1-C3 haloalkyl, C1-C3 alkoxy and C1-C3 haloalkoxy, and more optionally, R 13 and R 14 are each independently a hydrogen atom or C1-C3 alkyl, R 15 and R 16 are each independently selected from a hydrogen atom, a halogen atom, C2-6 alkenyl, an ester group, C1-C6 alkyl, C1-C6 haloalkyl, C1-C6 alkoxy and C1-C6 haloalkoxy, and optionally selected from a hydrogen atom, C1-C3 alkyl, C1-C3 fluoroalkyl and C2-C3 alkenyl, or R 15 and R 16 together form a carbonyl, or,

Chemical formula

[0016] By introducing the above additives into the electrolyte, the cycle performance of secondary batteries can be further improved, and gas generation during storage can be reduced.

[0017] In any embodiment, the additive is [ka] It contains at least one of the following substances: Selectively, the additive is [ka] It contains at least one of the following substances.

[0018] Furthermore, by selecting the above substance as an additive, it further contributes to improving the cycle performance of the battery and reducing gas generation during storage.

[0019] In any embodiment, based on the total weight of the electrolyte, the content W3 of the additive is 0.005 wt% to 10 wt%, optionally 0.01 wt% to 5 wt%, and more optionally 0.05 wt% to 2 wt%. By including the additive in the above content, the cycle performance of the secondary battery can be further improved, and gas generation during storage can be reduced.

[0020] In any embodiment, the content W3 of the additive and the content W1 of the first lithium iron phosphate material satisfy the relationship n = W1 / W3, where 2 < n < 8000, optionally 3 ≤ n ≤ 6000, more optionally 10 < n < 800, and still more optionally 15 ≤ n ≤ 600. In this way, gas generation during storage of the secondary battery is less, and the high-rate charging performance and cycle performance are good.

[0021] In any embodiment, the Dv50 of the second lithium iron phosphate material is 6 μm to 20 μm, optionally 7 μm to 12 μm, and the overall performance of the battery can be further improved.

[0022] The second aspect of the present application provides an electrical device including the secondary battery according to the first aspect.

[0023] The present application provides a lithium ion secondary battery having good high-rate charging performance and capable of having good cycle and safety performances, with good overall performance.

Brief Description of Drawings

[0024] [Figure 1] It is a schematic diagram of a battery cell according to an embodiment of the present application. [Figure 2] It is an exploded view of a battery cell according to an embodiment of the present application shown in FIG. 1. [Figure 3] This is a schematic diagram of a battery module according to one embodiment of the present invention. [Figure 4] This is a schematic diagram of a battery pack according to one embodiment of the present invention. [Figure 5] Figure 4 is an exploded view of a battery pack according to one embodiment of the present invention. [Figure 6] This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of the present invention. [Modes for carrying out the invention]

[0025] Hereinafter, embodiments specifically disclosing the secondary battery 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.

[0026] 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, and both a and b are 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.

[0027] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined to form new technical solutions.

[0028] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0029] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably in order. For example, if 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).

[0030] Unless otherwise specified, the terms “include” and “incorporate” as used herein are open-ended or closed-ended. For example, “include” and “incorporate” may further include or incorporate other components not listed, or may include or incorporate only the listed components.

[0031] 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).

[0032] In recent years, with the development of lithium-ion secondary battery technology, lithium-ion secondary batteries have been widely applied to many fields, including energy storage and power systems such as hydroelectric, thermal, wind, and solar power plants, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. As lithium-ion secondary batteries permeate various aspects of life, people are increasingly demanding faster charging performance from lithium-ion secondary batteries, as they want batteries that can be charged more quickly to meet the fast-paced needs of modern society.

[0033] Lithium-ion rechargeable batteries, which use lithium iron phosphate as the cathode material, have advantages such as high safety, long cycle life, and environmental friendliness, making them a promising candidate for an ideal power source. However, current batteries still struggle to meet the needs in terms of fast charging, which limits their application and development in industrial and consumer fields.

[0034] Furthermore, people noted that focusing solely on improving fast charging performance could have significant negative impacts on aspects such as the cycle performance and safety performance of secondary batteries.

[0035] To solve the above problems, this invention provides a lithium-ion secondary battery with good overall performance (i.e., good fast charging performance and the ability to achieve other desirable performance characteristics).

[0036] secondary battery In one embodiment of the present application, the present application proposes a secondary battery comprising a positive electrode plate and an electrolyte, wherein the positive electrode plate comprises a current collector and a positive electrode material layer provided on at least one side of the current collector, the positive electrode material layer comprises a first lithium iron phosphate material and a second lithium iron phosphate material, the Dv50 of the second lithium iron phosphate material being greater than the Dv50 of the first lithium iron phosphate material, and the Dv50 of the first lithium iron phosphate material being 0.05 μm to 6 μm. The electrolyte comprises a solvent, the solvent comprising a first solvent selected from at least one of the compounds of formula I, [ka] R1 and R2 are independently selected from C1-C6 alkyl and C1-C6 haloalkyl groups, respectively.

[0037] Without being bound by any theory, this invention improves the fast charging capability of a secondary battery (shorter charging time) by employing a positive electrode active material layer containing a mixture of two different lithium iron phosphate materials with Dv50 and combining it with an electrolyte containing a small molecule carboxylic acid ester solvent of formula I. At the same time, the secondary battery of this invention further possesses other desirable performance characteristics, such as low gas generation during storage (i.e., low volume expansion rate, contributing to improved safety performance) and good cycle performance, especially at high temperatures (e.g., 60°C). In summary, this invention provides a lithium-ion secondary battery with good overall performance, possessing at least one of good fast charging performance, reduced gas generation, and good cycle performance.

[0038] In this specification, "Dv50" represents the particle size at which the cumulative volume from the smallest particle size reaches 50% in the particle size distribution based on the volume of the material. Typically, Dv50 can be tested using methods and instruments known in the art, for example, by employing a laser diffraction particle size distribution analyzer (e.g., MalvernMastersizer 3000).

[0039] In some embodiments, the Dv50 of the first lithium iron phosphate material is 0.05 μm to 4 μm, selectively 1 μm to 4 μm, and more selectively 2 μm to 4 μm. By selecting a first lithium iron phosphate material within this Dv50 range, it is possible to further improve the fast charging performance of the battery, reduce the volume expansion rate, and achieve good cycle performance.

[0040] In some embodiments, based on the total weight of the first and second lithium iron phosphate materials, the amount W1 of the first lithium iron phosphate material is 2% to 80% by weight, selectively 20% to 60% by weight, and more selectively 20% to 40% by weight. In some embodiments, the amount W1 of the first lithium iron phosphate material is 2% by weight, 10% by weight, 20% by weight, 30% by weight, 40% by weight, 60% by weight, or 80% by weight, or W1 may be within the range of any two of the above. Including the first lithium iron phosphate material in the above content range helps to achieve well-balanced overall performance of the secondary battery, such as improved fast charging and cycling performance and reduced volume expansion.

[0041] In this specification, "wt%" means weight percentage and represents a percentage by weight.

[0042] In some embodiments, in formula I, R1 and R2 are each independently selected from C1-C4 alkyl and C1-C4 haloalkyl, and selectively, R1 and R2 are each independently selected from methyl, ethyl, propyl, fluoromethyl, fluoroethyl, and fluoropropyl. In this specification, the number of fluorine atoms in the fluoroalkyl is not particularly limited, and in some embodiments, the fluoroalkyl may be monofluoromethyl, difluoromethyl, trifluoromethyl, monofluoroethyl, difluoroethyl, trifluoroethyl, tetrafluoroethyl, or pentafluoroethyl, more selectively difluoromethyl or difluoroethyl. In some embodiments, R1 is selectively selected from C1-C4 alkyl or C1-C4 fluoroalkyl, more selectively methyl, ethyl, fluoromethyl, or fluoroethyl.

[0043] In some embodiments, the compound of formula I is [ka] [ka] Selected from at least one of the following, Selectively, the compound of formula I is [ka] Selected from at least one of the following, More selectively, it is I-1 and / or I-2. Furthermore, by selecting the first solvent, the electrolyte can be given appropriate viscosity and high conductivity, which further contributes to improving the fast charging performance and cycle performance of secondary batteries.

[0044] In some embodiments, based on the total weight of the solvent, the content W2 of the first solvent is 20% to 80% by weight, selectively 30% to 70% by weight, and more selectively 50% to 70% by weight. In some embodiments, the content W2 of the first solvent may be 20%, 30%, 40%, 50%, 60%, 70%, or 80% by weight, or W2 may be within a range composed of any two of the above. By controlling the amount W2 of the first solvent within the above range, the secondary battery further contributes to achieving at least one good overall performance among ideal fast charging performance (short charging time), good cycle performance, and low volume expansion rate.

[0045] In some embodiments, the solvent selectively comprises another solvent, the other solvent selected from linear carbonates, cyclic carbonates, or mixtures thereof. In this application, the type of linear carbonate or cyclic carbonate as the other solvent is not particularly limited and can be selected according to the actual needs. In some embodiments, the other solvent can be selected from at least one of the following substances: dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethylene carbonate (or ethylene carbonate), propylene carbonate (or propylene carbonate), butylene carbonate (or butylene carbonate), and γ-butyrolactone.

[0046] In some embodiments, the Dv50 of the first lithium iron phosphate material, its content W1, and the content W2 of the first solvent are: The relationship t = (W1 × W2) / Dv50 is satisfied, 0.0006 ≤ t ≤ 12.8, selectively 0.015 ≤ t ≤ 0.14, and more selectively 0.03 ≤ t ≤ 0.12, The unit for Dv50 is μm, and both W1 and W2 are weight percentages.

[0047] When t is within the above range, it is possible to ensure that the cell has good fast charging performance without worsening gas generation during storage.

[0048] In some embodiments, the electrolyte further comprises an additive, the additive comprising a sultone of formula II and / or a sulfate ester of formula III. [ka] p is 1, 2, or 3, and is selectively 1. R 11 and R 12 Each of these is independently selected from a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group, and a C1-C3 haloalkoxy group. R 13 and R 14 Each of these is independently selected from a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, and a C1-C3 haloalkoxy group. R 15 and R 16 Each is independently selected from a hydrogen atom, a halogen atom, a C2-C6 alkenyl group, an ester group, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, and a C1-C6 haloalkoxy group, or R 15 and R 16 They together constitute a carbonyl group. Or, [ka]

[0049] In some embodiments, R 11 and R 12 Each is independently selected from a hydrogen atom, a halogen atom, a C1-C3 alkyl group, and a C1-C3 haloalkyl group. In some embodiments, R 11 R is a hydrogen atom, 12 These are hydrogen atoms, C1-C3 alkyl atoms, or halogen atoms.

[0050] In some embodiments, R 13 and R 14 Each is independently selected from a hydrogen atom, a halogen atom, a C1-C3 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group, and a C1-C3 haloalkoxy group. In some embodiments, R 13 and R 14 Each of these is independently either a hydrogen atom or a C1-C3 alkyl group.

[0051] In some embodiments, R 15 and R 16 Each is independently selected from a hydrogen atom, a C1-C3 alkyl group, a C1-C3 fluoroalkyl group, and a C2-C3 alkenyl group, or R 15 and R 16They together constitute a carbonyl group. In some embodiments, R 15 R is a hydrogen atom, 16 is selected from a hydrogen atom, C1-C3 alkyl, C1-C3 fluoroalkyl and C2-C3 alkenyl, or R 15 and R 16 They both constitute a carbonyl group. [ka] q is 1, 2, or 3, and is selectively 1. R 17 and R 18 Each is independently selected from a hydrogen atom, a halogen atom, a C2-C6 alkenyl, a C1-C6 alkyl, a C1-C6 haloalkyl, a C1-C6 alkoxy, a C1-C6 alkyloxyacyl, a C1-C6 haloalkoxyacyloxy, and a 4-6 membered cyclic sulfate ester group. R 19 and R 20 Each of these is independently selected from hydrogen atoms, halogen atoms, C1-C6 alkyl groups, C1-C6 haloalkyl groups, C1-C6 alkoxy groups, C1-C6 haloalkoxy groups, and aryl groups (e.g., phenyl groups). Or, [ka]

[0052] In some embodiments, R 17 and R 18 Each is independently selected from a hydrogen atom, a halogen atom, a C2-4 alkenyl, a C1-C4 alkyl, a C1-C3 haloalkyl, a C1-C3 alkoxy, a C1-C3 haloalkoxyacyloxy C1-3 alkyl, and a 4-6 membered cyclic sulfate ester group. In some embodiments, R 17 and R 18 Each is independently selected from a hydrogen atom, a C1-4 alkyl group, and a C1-C3 alkyloxyacyl group. In some embodiments, R 17 R is a hydrogen atom, 18The element is selected from a hydrogen atom, C1-C4 alkyl groups, and C1-3 alkyloxyacyl groups.

[0053] In some embodiments, R 19 and R 20 Each of these is independently selected from a hydrogen atom, a halogen atom, and a C1-C6 alkyl group. In some embodiments, R 19 R is a hydrogen atom, 20 This is selected from hydrogen atoms, halogen atoms, and C1-C6 alkyl groups.

[0054] By introducing the above additives into the electrolyte, a polymer layer with strong ion conductivity is formed on the surface of the positive electrode material during the charging process, further improving the cycle performance of the secondary battery and reducing gas generation during storage (reducing the rate of volume expansion).

[0055] In some embodiments, the additive comprises at least one of the following substances: [ka] [ka]

[0056] In some embodiments, the additive comprises at least one of the following substances: [ka]

[0057] Furthermore, selecting the above-mentioned substances as additives further contributes to improving the battery's cycle performance and reducing gas generation during storage.

[0058] In some embodiments, based on the total weight of the electrolyte, the content W3 of the additive is 0.005 wt% to 10 wt%, optionally 0.01 wt% to 5 wt%, and more optionally 0.05 wt% to 2 wt%. In some embodiments, the content W3 of the additive may be 0.005 wt%, 0.01 wt%, 0.05 wt%, 0.1 wt%, 1 wt%, 2 wt%, 5 wt% or 10 wt%, or W3 may be within the range composed of any two of the above. By adding the additive in the above content, the cycle and storage performance of the battery can be further improved.

[0059] In some embodiments, the content W3 of the additive and the content W1 of the first lithium iron phosphate material satisfy the relationship n = W1 / W3, where 2 < n < 8000, optionally 3 ≤ n ≤ 6000, more optionally 10 < n < 800, and still more optionally 15 ≤ n ≤ 600. Both W1 and W3 are weight percentages. In some embodiments, n may be 3, 6, 15, 30, 300, 600, 3000 or 6000, or n may be within the range composed of any two of the above. When the proportion of the material having a small Dv50 is constant, if n is within the above range, the film formation on the positive electrode surface is sufficient, the surface resistance of the positive electrode is low, the gas generation during storage is small, and the fast charging performance and cycle performance are improved.

[0060] In some embodiments, the Dv50 of the second lithium iron phosphate material is 6 μm to 20 μm, optionally 7 μm to 16 μm, and more optionally 7 μm to 12 μm. In some embodiments, the Dv50 of the second lithium iron phosphate material may be 6 μm, 7 μm, 10 μm, 12 μm, 16 μm or 20 μm, or the Dv50 may be within the range composed of any two of the above. When the Dv50 of the second lithium iron phosphate material is within the above range, it contributes to further improving the overall performance of the battery.

[0061] The second aspect of the present application provides an electrical device including a secondary battery according to the first aspect of the present application.

[0062] The secondary battery of this application includes the form of a battery cell, the form of a battery module, and the form of a battery pack.

[0063] The battery cell, battery module, battery pack, and electrical device of this application will be described below with reference to the drawings as appropriate.

[0064] Typically, a battery cell further includes a positive 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 between the positive and negative electrodes. The electrolyte plays a role in conducting ions between the positive and negative electrodes. The separator is placed between the positive and negative electrodes and primarily serves to prevent short circuits between the positive and negative electrodes while simultaneously allowing ions to pass through.

[0065] [Positive plate] As described above, the positive electrode plate includes a positive electrode current collector and a positive electrode material layer (which may be referred to as a positive electrode film layer) provided on at least one surface of the positive electrode current collector, the positive electrode material layer includes a positive electrode active material.

[0066] 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.

[0067] In some embodiments, the positive electrode current collector can be a metal foil or a composite 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)).

[0068] In some embodiments, the cathode material 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.

[0069] In some embodiments, the mass percentage of the binder in the positive electrode material layer is 0.1% to 4%, and selectively 0.5% to 2%.

[0070] In some embodiments, the cathode material layer further selectively 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.

[0071] In some embodiments, the mass percentage of the conductive agent in the positive electrode material layer is 0.1% to 4%, and selectively 0.5% to 2%.

[0072] 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.

[0073] [negative electrode plate] The negative electrode plate includes a negative electrode current collector and a negative electrode material layer (which may be referred to as a negative electrode film layer) provided on at least one surface of the negative electrode current collector, the negative electrode material layer including a negative electrode active material.

[0074] 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.

[0075] In some embodiments, the negative electrode current collector can be a metal foil or a composite 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)).

[0076] In some embodiments, the type of negative electrode active material can be any negative electrode active material known in the art for use in 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 in batteries may be used. These negative electrode active materials may be used individually or in combination of two or more.

[0077] In some embodiments, the mass percentage of the negative electrode active material in the negative electrode material layer is 75% to 99%, and selectively 80% to 98%.

[0078] In some embodiments, the negative electrode material layer further selectively 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).

[0079] In some embodiments, the mass percentage of the binder in the negative electrode material layer is 0.1% to 3.5%, and selectively 0.5% to 2.5%.

[0080] In some embodiments, the negative electrode material 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.

[0081] In some embodiments, the mass percentage of the conductive agent in the negative electrode material layer is 0.04% to 5%, and selectively 0.3% to 3%.

[0082] In some embodiments, the negative electrode material layer further selectively includes other additives, such as a thickener (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0083] 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.

[0084] [Electrolytes] The electrolyte plays a role in conducting ions between the positive and negative electrodes. In this application, the type of electrolyte is not specifically limited and can be selected according to the needs. For example, the electrolyte may be a liquid, a gel, or an all-solid.

[0085] In some embodiments, an electrolyte solution is used as the electrolyte. The electrolyte solution comprises an electrolyte salt and the solvent described above.

[0086] In some embodiments, the electrolyte salt can be 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.

[0087] In some embodiments, the concentration of the electrolyte salt in the non-aqueous electrolyte is, for example, 0.3 mol / L (moles / liter) or higher, selectively 0.7 mol / L or higher, selectively 1.7 mol / L or lower, and even more selectively 1.2 mol / L or lower.

[0088] In some embodiments, the electrolyte further selectively comprises additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives capable of improving certain performance of the battery, such as additives that improve the overcharge performance of the battery, or additives that improve the high-temperature or low-temperature performance of the battery.

[0089] [Separator] In some embodiments, the battery cell 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.

[0090] 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.

[0091] [Exterior] In some embodiments, the battery cell may include an outer casing for packaging a positive electrode plate, a negative electrode plate, and an electrolyte. For example, the positive electrode plate, negative electrode plate, and separator may be laminated or wound to form a laminated or wound cell, the cell may be packaged within the outer casing, and the electrolyte may be the electrolyte described in the first aspect of this application, which permeates the cell. The number of cells in the battery cell may be one or more and can be adjusted according to the needs.

[0092] In one embodiment, the present application provides an electrode assembly. In some embodiments, a positive electrode plate, a negative electrode plate, and a separator can be manufactured as an electrode assembly by a winding process or a lamination process. An outer casing can be used to package the electrode assembly and the electrolyte.

[0093] In some embodiments, the battery cell casing may be a soft pack, such as a bag-type soft pack. The material of the soft pack may be plastic, and may include one or more of the following: polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc. In some embodiments, the battery cell casing may be a rigid case, such as a rigid plastic case, an aluminum case, or a steel case. In this application, the shape of the battery cell is not particularly limited and may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows a rectangular battery cell 5 as an example.

[0094] In some embodiments, referring to Figure 2, the casing may include a case 51 and a top cover assembly 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates are enclosed to form a housing chamber. The case 51 has an opening that communicates with the housing chamber, and the top cover assembly 53 may cover the opening to seal the housing chamber. The positive electrode plate, negative electrode plate and separator may form an electrode assembly 52 by a winding or lamination process. The electrode assembly 52 is packaged within the housing chamber. The electrolyte permeates the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, and a person skilled in the art can select according to specific practical needs.

[0095] In some embodiments, battery cells can be assembled into a battery module, the number of battery cells 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.

[0096] Figure 3 shows an example of a battery module 4. Referring to Figure 3, in the battery module 4, the multiple battery cells 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 battery cells 5 may be fixed by fastening members.

[0097] Selectively, the battery module 4 may further include a housing having a housing space, and a plurality of battery cells 5 are housed in said housing space.

[0098] In some embodiments, the battery cells or battery modules may be assembled into a battery pack, and the number of battery cells or 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.

[0099] 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 manner.

[0100] The present application further provides an electrical device comprising at least one of the battery cells, battery modules, and battery packs provided herein. The battery cell, 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, laptops, etc.), electric vehicles (e.g., rechargeable 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, energy storage systems, etc.

[0101] As the aforementioned electrical device, a battery cell, battery module, or battery pack can be selected according to the needs of its use.

[0102] 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.

[0103] 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. [Examples]

[0104] 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.

[0105] Example 1 1. Manufacturing of rechargeable batteries (1) Electrolyte In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were uniformly mixed in a 3 / 7 volume ratio. 60% by weight of methyl acetate was added to this mixture based on the total weight of the solvent. Then, the lithium salt LiPF6 was added and dissolved in the organic solvent to a concentration of 12.5% ​​of LiPF6. The mixture was then uniformly stirred to obtain the electrolyte.

[0106] (2) Positive plate A mixture of a first lithium iron phosphate (LiFePO4 or LFP) material (with a Dv50 of 2 μm, representing 30% by weight based on the total weight of the first and second lithium iron phosphate materials) and a second lithium iron phosphate material (with a Dv50 of 10 μm, representing 70% by weight based on the total weight of the first and second lithium iron phosphate materials), acetylene black as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder are added to the solvent N-methylpyrrolidone (NMP) in a weight ratio of 90:5:5. After thorough stirring and homogeneous mixing, a positive electrode slurry (with a solid content of 67%) is obtained. Subsequently, the positive electrode slurry is uniformly applied to the positive electrode current collector, and the weight of the positive electrode plate film layer on one side is 350 mg / 1540.25 mm. 2 A positive electrode plate was obtained, and then further subjected to baking, cold pressing, and cutting to obtain another positive electrode plate.

[0107] (3) Separator: A standard commercially available polypropylene film was used as the separator.

[0108] (4) Negative plate The active material, artificial graphite, the conductive agent, carbon black, the binder, styrene-butadiene rubber (SBR), and the thickener, sodium carboxymethylcellulose (CMC-Na), were dissolved in deionized water as a solvent in a weight ratio of 90:4:4:2 and uniformly mixed to form a negative electrode slurry (with a solid content of 48%). This negative electrode slurry was then uniformly applied to the copper foil of the negative electrode current collector in one or multiple applications (with a load of 97.2%), followed by baking, cold pressing, and cutting to obtain a negative electrode plate.

[0109] (5) Battery assembly A positive electrode plate (87 mm wide x 605 mm long), a separator (98 mm wide x 1896 mm long), and a negative electrode plate (93 mm wide x 735 mm long) were stacked in order, with the separator interposed between the positive and negative electrode plates to act as a separator. The assembly was then wound up to obtain an electrode assembly. The electrode assembly was placed in a battery case, dried, and then 158.1 g of electrolyte (51 Ah, injection coefficient 3.0 g / Ah) was injected. A lithium-ion battery was then manufactured through further processes such as chemical conversion and settling.

[0110] 2. Testing charging time Charge and discharge tests were performed on capacity-graded batteries at 25°C, ranging from 2.5V to 3.65V. The test steps were as follows: first, the battery was charged to 30% SOC with a constant current of 3C, then to 60% SOC with a constant current of 2C, then to 80% SOC with a constant current and voltage of 1C, with a cutoff current of 0.01C, and left to stand for 5 minutes. Finally, the battery was discharged to 2.0V with a constant current of 1C and left to stand for 5 minutes. The time taken to charge the battery to 80% SOC was measured.

[0111] 3. Test of volumetric expansion coefficient A lithium-ion secondary battery was charged to 3.65V with a constant current of 0.33C, then charged to 0.05C with a constant voltage of 3.65V until the current was reduced to 0.05C, and the lithium-ion battery was fully charged. The volume of the battery was tested using the drainage method, and this volume was recorded as the volume before storage. Subsequently, the lithium-ion battery was stored at 60°C for 60 days. After storage, the lithium-ion secondary battery was placed in an environment of 25°C, and the volume of the battery was tested using the drainage method, and this volume was recorded as the volume after storage. The volume expansion rate of the battery was calculated according to the following formula.

number

[0112] 4. Cycle count test when battery capacity is reduced to 80% at 60°C. At 60°C, a lithium-ion battery was charged to 3.65V with a constant current of 0.5C, then charged again with a constant voltage of 3.65V until the current fell below 0.05C, and finally discharged to 2.5V with a constant current of 0.5C. This constitutes one charge-discharge process (i.e., one cycle). This charging and discharging process was repeated, and the number of cycles until the capacity retention rate reached 80% was recorded.

[0113] Examples 2-6 The manufacturing and testing methods for Examples 2-6 are similar to those for Example 1, except that the Dv50 of the first lithium iron phosphate material is different. Details and test results are shown in Table 1.

[0114] Examples 7-8 The manufacturing and testing methods for Examples 7 and 8 are similar to those for Example 1, but the difference is that ethyl difluoroacetate and methyl difluoroacetate were used as the first solvent, respectively. Details and test results are shown in Table 1.

[0115] Comparative Examples 1-2 The manufacturing and testing methods for Comparative Examples 1 and 2 are similar to those for Example 1, but the differences lie in the Dv50 of the first lithium iron phosphate material and the first solvent. Details and test results are shown in Table 1.

[0116] Comparative Examples 3-5 In Comparative Example 3, the first lithium iron phosphate material (with a Dv50 of 2 μm) was used as the positive electrode active material in all cases. In Comparative Example 4, the second lithium iron phosphate material (with a Dv50 of 10 μm) was used as the positive electrode active material in all cases. In Comparative Example 5, dimethyl carbonate was used as the first solvent instead of methyl acetate as in Example 1, with a ratio of 60% by weight. The rest of the materials were the same as in Example 1.

[0117] Examples 9-16 The manufacturing and testing methods for Examples 9 to 16 are similar to those for Example 1, but the difference lies in the content W1 of the first lithium iron phosphate material. Details and test results are shown in Table 1.

[0118] Examples 17-24 The manufacturing and testing methods for Examples 17-24 are similar to those for Example 1, except that the content W2 of the first solvent is different. Details and test results are shown in Table 1.

[0119] [Table 1-1] [Table 1-2] [Table 1-3] 1. Here, "the first material" refers to "the first lithium iron phosphate material," and similarly, "the second material" below refers to "the second lithium iron phosphate material." 2. In Tables 1 and 2, W1, W2, and W3 are all weight percentages. 3. Volume expansion rate after storage at 60°C for 30 days at 100% SOC. 4. The number of cycles required to achieve an 80% capacity retention rate at 60°C.

[0120] As can be seen from Examples 1-9 and Comparative Examples 1-5, the secondary battery of the present invention has good overall performance, good fast charging capability, low gas generation during storage (low volume expansion rate), and good cycle performance (especially at high temperatures). Furthermore, when the Dv50 of the first lithium iron phosphate material is 0.05 μm to 6 μm, and selectively 1 μm to 4 μm, it further contributes to improving the fast charging performance of the battery, reducing the volume expansion rate, and achieving good cycle performance. Also, when t = (W1 × W2) / Dv50 and 0.0006 ≤ t ≤ 12.8, it can be guaranteed that the cell has good fast charging performance without worsening gas generation during storage.

[0121] As can be seen from Examples 10 to 17, when the content W1 of the first lithium iron phosphate material is 2% to 80% by weight based on the total weight of the first and second lithium iron phosphate materials, the secondary battery has a better overall performance with a good balance of good fast charging performance and cycle performance, and a low storage volume expansion rate.

[0122] As can be seen from Examples 18-25, when the content W2 of the first solvent is 20% to 80% by weight based on the total weight of the solvent, the secondary battery has ideal overall performance.

[0123] Examples 26-30 The manufacturing and testing methods for Examples 26-30 are substantially the same as those for Example 1, the only difference being the Dv50 of the second lithium iron phosphate material. Details of the Dv50 and test results for each example are shown in Table 2.

[0124] [Table 2]

[0125] As can be seen from Table 2 above, when the Dv50 of the second lithium iron phosphate material is in the range of 6 μm to 20 μm, and especially when it is in the range of 7 μm to 12 μm, it contributes even more to improving the overall performance of the battery.

[0126] Examples 31-52 The manufacturing and testing methods for Examples 30-38 are similar to those for Example 1, but the difference is that 1% by weight of an additive of formula II or formula III was added based on the total weight of the electrolyte. The content of additive II-8 in Examples 39-45 differs from that in Example 33, and the content of additive II-1 in Examples 46-52 differs from that in Example 34. Details and test results are shown in Table 3 below.

[0127] [Table 3-1] [Table 3-2]

[0128] As can be seen from Table 3, by adding an additive of formula II or formula III, particularly in an amount of 0.005% to 10% by weight based on the total weight of the electrolyte, the performance of the battery was further improved, for example, by improving cycle performance and reducing gas generation.

[0129] 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]

[0130] 1 Battery pack 2. Top box 3. Lower box 4 Battery Modules 5 battery cells 51 cases 52 Electrode assembly 53 Top cover assembly

Claims

1. A secondary battery comprising a positive electrode plate and an electrolyte, wherein the positive electrode plate includes a current collector and a positive electrode material layer provided on at least one side of the current collector, the positive electrode material layer comprises a first lithium iron phosphate material and a second lithium iron phosphate material, the Dv50 of the second lithium iron phosphate material being greater than the Dv50 of the first lithium iron phosphate material, and the Dv50 of the first lithium iron phosphate material being 0.05 μm to 6 μm. The electrolyte comprises a solvent, the solvent comprising a first solvent selected from at least one of the compounds of formula I, 【Chemistry 1】 R 1 and R 2 These are secondary batteries, each independently selected from C1-C6 alkyl and C1-C6 haloalkyl.

2. The secondary battery according to claim 1, wherein the Dv50 of the first lithium iron phosphate material is 0.05 μm to 4 μm, selectively 1 μm to 4 μm, and more selectively 2 μm to 4 μm.

3. The secondary battery according to claim 1 or 2, wherein, based on the total weight of the first and second lithium iron phosphate materials, the content W1 of the first lithium iron phosphate material is 2% by weight to 80% by weight, selectively 20% by weight to 60% by weight, and more selectively 20% by weight to 40% by weight.

4. The aforementioned R 1 and R 2 Each is independently selected from C1-C4 alkyl and C1-C4 haloalkyl, and selectively R 1 and R 2 The secondary battery according to any one of claims 1 to 3, wherein each is independently selected from methyl, ethyl, propyl, fluoromethyl, fluoroethyl, and fluoropropyl.

5. The compound of formula I is 【Chemistry 2】 At least one of the following compounds is selected: Selectively, the compound of formula I is 【Transformation 3】 A secondary battery according to any one of claims 1 to 4, wherein at least one of the following compounds is selected.

6. A secondary battery according to any one of claims 1 to 5, wherein, based on the total weight of the solvent, the content W2 of the first solvent is 20% to 80% by weight, selectively 30% to 70% by weight, and more selectively 50% to 70% by weight.

7. The Dv50 of the first lithium iron phosphate material, its content W1, and the content W2 of the first solvent are: The relationship t = (W1 × W2) / Dv50 is satisfied, 0.0006 ≤ t ≤ 12.8, selectively 0.015 ≤ t ≤ 0.14, and more selectively 0.03 ≤ t ≤ 0.12, A secondary battery according to any one of claims 1 to 6, wherein the unit of Dv50 is μm, and W1 and W2 are both weight percentages.

8. The electrolyte further comprises an additive, the additive comprising a sultone of formula II and / or a sulfate ester of formula III. 【Chemistry 4】 p is 1, 2, or 3, and is selectively 1. R 11 and R 12 are each independently selected from a hydrogen atom, a halogen atom, C1-C6 alkyl, C1-C3 haloalkyl, C1-C3 alkoxy, and C1-C3 haloalkoxy, and optionally, R 11 and R 12 are each independently selected from a hydrogen atom, a halogen atom, C1-C3 alkyl, and C1-C3 haloalkyl, and more optionally, R 11 is a hydrogen atom, and R 12 is a hydrogen atom, C1-C3 alkyl, or a halogen atom, R 13 and R 14 Each is independently selected from a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, and a C1-C3 haloalkoxy group, and selectively R 13 and R 14 Each is independently selected from a hydrogen atom, a halogen atom, a C1-C3 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group, and a C1-C3 haloalkoxy group, and more selectively, R 13 and R 14 Each of these is independently a hydrogen atom or a C1-C3 alkyl group. R 15 and R 16 Each is independently selected from hydrogen atoms, halogen atoms, C2-C6 alkenyl groups, ester groups, C1-C6 alkyl groups, C1-C6 haloalkyl groups, C1-C6 alkoxy groups, and C1-C6 haloalkoxy groups, and selectively selected from hydrogen atoms, C1-C3 alkyl groups, C1-C3 fluoroalkyl groups, and C2-C3 alkenyl groups, or R 15 and R 16 They together constitute a carbonyl group. Or, 【Transformation 5】 q is 1, 2, or 3, and is selectively 1. R 17 and R 18 Each is independently selected from a hydrogen atom, a halogen atom, a C2-C6 alkenyl, a C1-C6 alkyl, a C1-C6 haloalkyl, a C1-C6 alkoxy, a C1-C6 alkyloxyacyl, a C1-C6 haloalkoxyacyloxyC1-6 alkyl, and a 4-6 membered cyclic sulfate ester group, and selectively, R 17 and R 18 Each is independently selected from a hydrogen atom, a halogen atom, a C2-C4 alkenyl, a C1-C4 alkyl, a C1-C3 haloalkyl, a C1-C3 alkoxy, a C1-C3 haloalkoxyacyloxy C1-C3 alkyl, and a 4-6 membered cyclic sulfate ester group, and more selectively, R 17 and R 18 Each of these is independently selected from a hydrogen atom, a C1-C4 alkyl group, and a C1-C3 alkyloxyacyl group. R 19 and R 20 Each is independently selected from a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, and an aryl group, and selectively, R 19 and R 20 Each of these is independently selected from a hydrogen atom, a halogen atom, and a C1-C6 alkyl group. Or, 【Transformation 6】

9. The aforementioned additive is 【Transformation 7】 【Transformation 8】 It contains at least one of the following substances: Selectively, the additive is 【Chemistry 9】 The secondary battery according to claim 8, comprising at least one of the following substances.

10. The secondary battery according to claim 8 or 9, wherein, based on the total weight of the electrolyte, the content W3 of the additive is 0.005% to 10% by weight, selectively 0.01% to 5% by weight, and more selectively 0.05% to 2% by weight.

11. The content W3 of the additive and the content W1 of the first lithium iron phosphate material are, A secondary battery according to any one of claims 8 to 10, satisfying the relationship n = W1 / W3, where 2 < n < 8000, selectively 3 ≤ n ≤ 6000, more selectively 10 < n < 800, and even more selectively 15 ≤ n ≤ 600.

12. The secondary battery according to any one of claims 1 to 11, wherein the Dv50 of the second lithium iron phosphate material is 6 μm to 20 μm, and selectively 7 μm to 12 μm.

13. An electrical device comprising a secondary battery according to any one of claims 9 to 12.

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