Electrolyte solution and secondary battery, battery module, battery pack, and electric device containing the same

Abstract

The electrolyte includes a battery module (4), a battery pack (1) and an electric device. The electrolyte includes a solvent and a fluorine-containing lithium salt, and the electrochemical stability coefficient of the electrolyte is x=S F / (S F +4S H ) is 0.18-0.6, preferably 0.25-0.55, and S F and S H can be determined by the described measurement method. The secondary battery (5) using the electrolyte has good electrochemical stability, which helps to improve the storage performance and cycle performance of the secondary battery (5).

Description

[Technical field]

[0001] The present application relates to the technical field of lithium batteries, and in particular to an electrolyte and a secondary battery, battery module, battery pack, and electric device containing the electrolyte. [Background technology]

[0002] In recent years, as secondary batteries are more and more widely applied in many industries such as electric vehicles, electric motorcycles, aerospace, hydroelectric power plants, wind power plants, solar power plants, etc., people have increasingly higher requirements for the performance of secondary batteries, one of which is that secondary batteries have good storage performance and cycle performance. However, conventional industrializable electrolytes are easily oxidized and decomposed under high voltage operating conditions, which deteriorates the performance of secondary batteries. Therefore, how to provide an electrolyte with stable performance under high voltage operating conditions in order to improve the storage performance and cycle performance of secondary batteries remains a technical problem that engineers need to solve urgently. Summary of the Invention [Problem to be solved by the invention]

[0003] The present application has been made in view of the above problems, and an object of the present application is to provide an electrolyte solution that has good stability under high voltage operating conditions and is useful for improving the storage performance and cycle performance of secondary batteries. [Means for solving the problem]

[0004] In order to achieve the above object, the present application provides an electrolyte solution, and a secondary battery, a battery module, a battery pack, and an electric device each containing the electrolyte solution.

[0005] A first aspect of the present application is an electrolyte solution comprising a solvent and a fluorine-containing lithium salt, the electrolyte solution having an electrochemical stability coefficient x=SF / (SF+4SH) of 0.18 to 0.6, and optionally 0.25 to 0.55; SF is the peak area of ​​fluorine excluding the fluorine corresponding to the lithium salt and the fluorine corresponding to 4-fluoropyridine in the range of -280 ppm to 80 ppm when a fluorine-19 nuclear magnetic resonance test is performed on a mixture of an electrolyte and 4-fluoropyridine in a weight ratio of 1:1, and the peak area of ​​fluorine corresponding to 4-fluoropyridine in the range of -102 ppm to -104 ppm is normalized to 1; The SH is the peak area of ​​hydrogen excluding hydrogen corresponding to acetonitrile-d3 and 4-fluoropyridine in the range of 0.5 ppm to 10 ppm in a proton nuclear magnetic resonance test of a mixture of electrolyte and 4-fluoropyridine in a weight ratio of 1:1, and the peak areas of hydrogen corresponding to 4-fluoropyridine in the ranges of 7.0 ppm to 7.2 ppm and 8.45 ppm to 8.65 ppm are normalized to 1; The electrolyte provides an electrolyte that does not contain acetonitrile-d3, 4-fluoropyridine.

[0006] When the chemical stability coefficient of the electrolyte satisfies the above relationship, the electrolyte has good stability, and at the same time is compatible with high voltage positive and negative electrodes, and further improves the storage performance and cycle performance of the secondary battery.

[0007] In any embodiment, optionally, the electrolyte comprises a first solvent and a second solvent; the first solvent is selected from one or more of a fluoroether, a fluorocarbonate, a fluorocarboxylate, a fluorobenzene, or a fluorosulfone; Selectively, [ka] one or more of R 1 , R 3 , R 5 and R 13 are C 1 ~C 6 fluoroalkanes, R 2 , R 4 , R 6 , R 14 , R15 and R 16 are C 1 ~C 6 Alkane or C 1 ~C 6 fluoroalkanes, R 7 ~R 12 are C 1 ~C 6 R is selected from a fluoroalkane, fluorine or hydrogen; 7 ~R 12 At least one of R is selected from fluorine or a fluoroalkane; 15 and R 16 At least one of them is C 1 ~C 6 selected from fluoroalkanes, More selectively, [ka] one or more of the second solvent is selected from one or more of a non-fluorocarbonate, a non-fluorocarboxylate, a non-fluoroether, or a non-fluorosulfone; Selectively, [ka] one or more of R 1 ', R 2 ', R 3 ', R 13 ', R 14 ' and R 16 ' are C 1 ~C 6 selected from alkanes, R 4 ' and R 15 ' are C 1 ~C 6 selected from an alkane or hydrogen; More preferably, the carbonate 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, propyl propionate.

[0008] When the first solvent and the second solvent are selected from the above solvents, the solvent can form a special solvation structure with the lithium salt in the electrolyte, thereby reducing side reactions of the solvent on the surfaces of the positive and negative electrodes and contributing to extending the life of the secondary battery.

[0009] In any embodiment, optionally, based on the total weight of the first solvent and the second solvent, the content y1 of the first solvent is 10 to 100%, optionally 45 to 100%, and further optionally 80 to 100%.

[0010] In any embodiment, optionally, based on the total weight of the first solvent and the second solvent, the content y2 of the second solvent is 0 to 90%, optionally 0 to 55%, and further optionally 0 to 20%.

[0011] In any embodiment, optionally, the content y1 of the first solvent and the content y2 of the second solvent satisfy y1 / y2≧0.82, optionally y1 / y2≧2.33, further optionally y1 / y2≧4, and further optionally y1 / y2≧5.67.

[0012] When the contents of the first solvent and the second solvent are within the above ranges, this contributes to further improving the stability of the electrolyte.

[0013] In any embodiment, optionally, the electrolyte further comprises a film-forming additive, the film-forming additive being selected from one or more of a linear or cyclic sulfate ester, a linear or cyclic sulfonate ester, a linear or cyclic carbonate ester, a polycyclic sulfate ester, or a polycyclic sulfonate ester; Selectively, [ka] one or more of More selectively, [ka] One or more of the following:

[0014] The film-forming additive can preferentially form a film on the negative electrode, reduce the loss of active lithium, and further improve the performance of the battery.

[0015] In any embodiment, optionally, the content of the film-forming additive is 0.1 to 10%, optionally 0.5 to 7%, and further optionally 1 to 5%, based on the total weight of the first solvent and the second solvent.

[0016] In any embodiment, optionally, based on the total weight of the first solvent and the second solvent, the film-forming additive is [ka] Includes.

[0017] When the electrolyte contains the above-mentioned amount of the film-forming additive, it contributes to further improving the stability of the electrolyte, and further improving the storage performance and cycle performance of the corresponding secondary battery.

[0018] In any embodiment, optionally, the lithium salt comprises one or more of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

[0019] When the electrolyte contains the lithium salt, the conductivity of the electrolyte is improved, which contributes to further improving the performance of the secondary battery.

[0020] In any embodiment, optionally the concentration of the lithium salt is 0.7 to 2.5 mol / L, optionally 1 to 1.5 mol / L.

[0021] In any embodiment, optionally, the acidity of the electrolyte is ≦50 ppm and the purity of each solvent used is ≧99.8%.

[0022] When the acidity and purity of the electrolyte are within the above ranges, the electrolyte has good stability and is less likely to cause side reactions, which contributes to improving the cycle performance of the secondary battery.

[0023] A second aspect of the present application provides a secondary battery including the electrolyte according to the first aspect of the present application. The secondary battery can be manufactured by a method for manufacturing a secondary battery commonly used in the art.

[0024] In any embodiment, optionally, based on the total weight of the positive electrode active material, the positive electrode active material of the secondary battery has a Mn element content of ≧25%; Optionally, LiM p Mn 2-p O 4 , LiN q Mn 1-q PO 4 Or Li 1+t Mn 1-w L w O 2+t wherein 0≦p≦1, 0≦q≦0.5, 0≦t≦1, 0≦w≦0.5; and M, N, and L each independently represent one or more of Ni, Co, Fe, Cr, V, Ti, Zr, La, Ce, Rb, P, W, Nb, Mo, Sb, B, Al, and Si; More selectively, LiM p Mn 2-p O 4 Or Li 1+t Mn 1-w L w O 2+t one or more of More selectively, LiNi 0.5 Mn 1.5 O 4 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , Li 2 MnO 3 , LiMnPO4 One or more of the following:

[0025] When the positive electrode active material of the secondary battery is selected from the above types, it is possible to improve the energy density of the secondary battery, contribute to reducing the manufacturing cost, and cause less environmental pollution.

[0026] In any embodiment, optionally, the particles of the positive electrode active material are single crystal or pseudo-single crystal.

[0027] When the positive electrode active material is a single crystal, the active material itself is less likely to be broken, reducing the probability of exposing new surfaces, and further reducing side reactions of the electrolyte, thereby improving the stability of the electrolyte.

[0028] In any embodiment, optionally, the particle size of the positive electrode active material is 1 to 20 μm, optionally 3 to 15 μm.

[0029] In any embodiment, optionally, the specific surface area of ​​the positive electrode active material is 1.5 m 2 / g or less, and selectively 0.1m 2 / g~1m 2 / g.

[0030] When the particle size and surface area of ​​the positive electrode active material are within the above ranges, it contributes to reducing side reactions and improving the stability of the electrolyte, and also helps to avoid the increase in energy consumption in the process and the deterioration of the processing performance of the positive electrode plate caused by an excessively large particle size.

[0031] A third aspect of the present application provides a battery module including the secondary battery according to the second aspect of the present application. The battery module can be manufactured by a manufacturing method for a battery module commonly used in the art.

[0032] A fourth aspect of the present application provides a battery pack including the battery module according to the third aspect of the present application. The battery pack can be manufactured by a method for manufacturing a battery pack commonly used in the art.

[0033] A fifth aspect of the present application provides an electric device including at least one selected from the secondary battery according to the second aspect of the present application, the battery module according to the third aspect of the present application, or the battery pack according to the fourth aspect of the present application. Effect of the Invention

[0034] In the electrolyte described in this application, the electrochemical stability factor x=S F / (S F +4S H ) is 0.18-0.6, and optionally 0.25-0.55, which contributes to improving the stability of the electrolyte, makes the electrolyte and the positive and negative electrodes have good compatibility, reduces the destruction of the surface of the positive electrode active material after the electrolyte generates hydrofluoric acid, reduces the exposure of new active sites, reduces the side reaction of the electrolyte, and improves the storage performance and cycle performance of the secondary battery. In addition, when the electrochemical stability coefficient is within the above range, it reduces the destruction of the generated hydrofluoric acid on the negative electrode SEI film (solid electrolyte interface), and helps to avoid the reduction of a large amount of solvent at the negative electrode, which leads to the loss of a large amount of active lithium, and further deteriorates the storage performance and cycle performance of the secondary battery.

[0035] The battery module, battery pack and electric device of the present application include the secondary battery provided by the present application, and therefore have at least the same advantages as the secondary battery. [Brief description of the drawings]

[0036] [Figure 1] FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application. [Diagram 2] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. [Diagram 3] FIG. 1 is a schematic diagram of a battery module according to an embodiment of the present application. [Figure 4] FIG. 1 is a schematic diagram of a battery pack according to an embodiment of the present application. [Diagram 5]FIG. 5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 4. [Figure 6] 1 is a schematic diagram of an electrical device that uses a secondary battery as a power source according to an embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Hereinafter, with reference to the drawings as appropriate, embodiments specifically disclosing the electrolyte, secondary battery, battery module, battery pack, and electric device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and duplicate description of substantially the same structure may be omitted. This is to avoid the following description becoming unnecessarily redundant and to allow those skilled in the art to easily understand. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the scope of the claims.

[0038] The "ranges" disclosed herein are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the given range. Such a defined range may be inclusive or exclusive of both end values, and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a given parameter, it is understood that ranges of 60-110 and 80-120 are also anticipated. Also, if 1 and 2 are listed as the minimum range values, and 3, 4, and 5 are listed as the maximum range values, then the ranges of 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all anticipated. In this application, unless otherwise stated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are recited herein, and "0-5" is simply shorthand for combinations of these numerical values. Note that when a parameter is stated to be an integer ≧2, this is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0039] Unless otherwise stated, all the embodiments and optional embodiments in the present application can be combined with each other to form new technical solutions.

[0040] Unless otherwise stated, all technical features and optional technical features in the present application can be combined with each other to form new technical solutions.

[0041] Unless otherwise stated, all steps in the present application may be performed in sequence, randomly, and preferably in sequence. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, or may include steps (b) and (a) performed in sequence. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), or may include steps (c), (a) and (b).

[0042] Unless otherwise stated, the terms "comprise" and "comprises" referred to in this application may be open ended or closed ended. For example, the terms "comprise" and "comprises" may further include or include other components not listed, or may include or include only the listed components.

[0043] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any one of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or A and B are both true (or exist).

[0044] In practical work, the inventors found that most of the electrolytes in the prior art are not suitable for operating at high voltages, such as voltages above 4.2 V, because these electrolytes have low stability and are prone to decomposition under high voltage operating conditions, resulting in the generation of large amounts of HF, which will corrode the positive electrode active material and deteriorate the performance of the secondary battery.

[0045] After extensive experimentation, the inventors have determined the corresponding integral areas S of the electrolyte in proton nuclear magnetic resonance and fluorine-19 nuclear magnetic resonance.H and S F , x=S F / (S F +4S H ) is 0.18-0.6, and optionally 0.25-0.55, the electrolyte has good electrochemical stability even under high voltage operating conditions, is more suitable for the positive and negative electrodes, reduces the destruction of the positive and negative electrode materials after the electrolyte generates hydrofluoric acid, and further improves the storage performance and cycle performance of the secondary battery. In addition, the types and amounts of various solvents and additives in the electrolyte can be further adjusted to further improve the storage performance and cycle performance of the secondary battery.

[0046] [Electrolyte] A first aspect of the present application is an electrolyte solution containing a solvent and a fluorine-containing lithium salt, the electrolyte solution having an electrochemical stability coefficient x=S F / (S F +4S H ) is 0.18 to 0.6, and optionally 0.25 to 0.55; S F is the peak area of ​​fluorine excluding the fluorine corresponding to the lithium salt and the fluorine corresponding to 4-fluoropyridine in the range of -280 ppm to 80 ppm when a mixture of electrolyte and 4-fluoropyridine in a weight ratio of 1:1 is subjected to a fluorine-19 nuclear magnetic resonance test, and the peak area of ​​fluorine corresponding to 4-fluoropyridine in the range of -102 ppm to -104 ppm is normalized to 1, S H is the peak area of ​​hydrogen excluding hydrogen corresponding to acetonitrile-d3 and 4-fluoropyridine in the range of 0.5 ppm to 10 ppm when a mixture of electrolyte and 4-fluoropyridine with a weight ratio of 1:1 is subjected to a proton nuclear magnetic resonance test, and the peak areas of hydrogen corresponding to 4-fluoropyridine in the ranges of 7.0 ppm to 7.2 ppm and 8.45 ppm to 8.65 ppm are normalized to 1; The electrolyte provides an electrolyte that does not contain acetonitrile-d3, 4-fluoropyridine.

[0047] Although the mechanism is not yet clear, the inventors believe that in the electrolyte solution described in this application, the electrochemical stability coefficient x=S F / (S F +4S H ) is 0.18 to 0.6, it contributes to improving the stability of the electrolyte, the electrolyte and the positive and negative electrodes have good compatibility, the electrolyte generates hydrofluoric acid and then damages the surface of the positive electrode active material, the exposure of new active sites is reduced, the side reaction of the electrolyte is reduced, and the storage performance and cycle performance of the secondary battery are improved. In addition, when the electrochemical stability coefficient is within the above range, it is found that it is useful for reducing the damage of the generated hydrofluoric acid to the negative electrode SEI film, and preventing a large amount of solvent from being reduced at the negative electrode, which leads to a large amount of active lithium loss and further deteriorates the storage performance and cycle performance of the secondary battery. Alternatively, when x is 0.25 to 0.55, it further improves the compatibility of the electrolyte with the positive and negative electrodes, and further improves the storage performance and cycle performance of the secondary battery.

[0048] It should be noted that the present application specifies that the electrolyte does not contain acetonitrile-d3,4-fluoropyridine, which is determined by nuclear magnetic resonance spectroscopy to be S F and S H When measuring, acetonitrile-d3 must be used as the solvent for the nuclear magnetic resonance test, and 4-fluoropyridine must be used as the reference. If the electrolyte also contains the reference, the characteristic peaks of the same components in the reference and electrolyte cannot be distinguished, and S F and S H This is because the measurement of will be inaccurate. Those skilled in the art should understand that when performing nuclear magnetic resonance testing, different deuterated solvents and references can be selected according to the needs of the test. In addition, the mass ratio of the electrolyte to 4-fluoropyridine can be determined according to the test, for example, the mass ratio of the electrolyte to 4-fluoropyridine can be 1:1.

[0049] In some embodiments, optionally, the electrolyte comprises a first solvent and a second solvent; the first solvent is selected from one or more of a fluoroether, a fluorocarbonate, a fluorocarboxylate, a fluorobenzene, or a fluorosulfone; Selectively, [ka] one or more of R 1 , R 3 , R 5 and R 13 are C 1 ~C 6 fluoroalkanes, R 2 , R 4 , R 6 , R 14 , R 15 and R 16 are C 1 ~C 6 Alkane or C 1 ~C 6 fluoroalkanes, R 7 ~R 12 are C 1 ~C 6 R is selected from a fluoroalkane, fluorine or hydrogen; 7 ~R 12 At least one of R is selected from fluorine or a fluoroalkane; 15 and R 16 At least one of them is C 1 ~C 6 selected from fluoroalkanes, More selectively, [ka] one or more of the second solvent is selected from one or more of a non-fluorocarbonate, a non-fluorocarboxylate, a non-fluoroether, or a non-fluorosulfone; Selectively, [ka] one or more of R 1 ', R 2 ', R 3 ', R 13 ', R 14 ' and R 16 ' are C 1 ~C 6 selected from alkanes, R 4 ' and R 15 ' are C 1 ~C 6 selected from an alkane or hydrogen; More preferably, the carbonate 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, propyl propionate.

[0050] When the first solvent and the second solvent are selected from the above solvents, the solvent forms a special solvation structure with the lithium salt in the electrolyte, promotes the formation of a dense protective film in the initialization stage, promotes desolvation, and further reduces side reactions of the solvent on the positive and negative electrode surfaces, thereby improving the cycle performance of the secondary battery.

[0051] In some embodiments, optionally based on the total weight of the first solvent and the second solvent, the content y1 of the first solvent is 10 to 100%, optionally 45 to 100%, and further optionally 80 to 100%. For example, the content y1 of the first solvent may be 10%, 30%, 45%, 70%, 80%, 90%, or 100%.

[0052] In some embodiments, optionally based on the total weight of the first solvent and the second solvent, the content y2 of the second solvent is 0 to 90%, optionally 0 to 55%, and further optionally 0 to 20%. For example, the content y2 of the second solvent may be 70%, 55%, 40%, 30%, 20%, 10%, or 0%.

[0053] When the contents of the first solvent and the second solvent are within the above ranges, the stability of the electrolyte is further improved, which contributes to improving the storage performance and cycle performance of the secondary battery.

[0054] In some embodiments, optionally, the sum of the weights of the first solvent and the second solvent accounts for 60 to 90%, and optionally 60 to 87.5%, of the total weight of the electrolyte solution of the present application.

[0055] When the weight percentage of the sum of the weights of the first solvent and the second solvent relative to the electrolyte of the present application is within the above range, this contributes to further improving the stability of the electrolyte.

[0056] In some embodiments, optionally, the content y1 of the first solvent and the content y2 of the second solvent satisfy y1 / y2≧0.82, optionally y1 / y2≧2.33, further optionally y1 / y2≧4, and further optionally y1 / y2≧5.67.

[0057] When the content y1 of the first solvent and the content y2 of the second solvent satisfy the above relationship, the electrolyte has better electrochemical stability, further improves the compatibility of the electrolyte with the positive and negative electrodes, reduces side reactions, and helps to improve the storage performance and cycle performance of the secondary battery.

[0058] In some embodiments, optionally, the content y1 of the first solvent and the content y2 of the second solvent satisfy 0≦y1×y2 / (y1+y2)≦0.25, optionally 0≦y1×y2 / (y1+y2)≦0.16, and further optionally 0≦y1×y2 / (y1+y2)≦0.09.

[0059] When the content y1 of the first solvent and the content y2 of the second solvent satisfy the above relationship, the stability of the electrolyte is further improved, which helps to improve the storage performance and cycle performance of the secondary battery.

[0060] In some embodiments, optionally, the electrolyte further comprises a film-forming additive, the film-forming additive being selected from one or more of a linear or cyclic sulfate ester, a linear or cyclic sulfonate ester, a linear or cyclic carbonate ester, a polycyclic sulfate ester, or a polycyclic sulfonate ester; Selectively, [ka] one or more of More selectively, [ka] One or more of the following:

[0061] The film-forming additive can preferentially form a film on the negative electrode, reduce the loss of active lithium, and further improve the storage performance and cycle performance of the secondary battery.

[0062] In some embodiments, optionally, the content of the film-forming additive is 0.1 to 10%, optionally 0.5 to 7%, and further optionally 1 to 5%, based on the total weight of the first solvent and the second solvent.

[0063] In some embodiments, optionally based on the combined weight of the first solvent and the second solvent, the film-forming additive comprises: [ka] Includes.

[0064] When the electrolyte contains the above-mentioned amount of the film-forming additive, it contributes to further improving the stability of the electrolyte, and further improving the storage performance and cycle performance of the corresponding secondary battery.

[0065] In some embodiments, optionally, the lithium salt comprises one or more of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

[0066] In some embodiments, the concentration of the lithium salt is optionally 0.7 to 2.5 mol / L, optionally 1 to 1.5 mol / L.

[0067] When the electrolyte contains the lithium salt at the above-mentioned concentration, the viscosity of the electrolyte is appropriate, which improves the conductivity of the electrolyte and contributes to improving the performance of the secondary battery. However, if the concentration of the lithium salt in the electrolyte is too high, the concentration of the electrolyte as a whole increases, but the dissociation degree of the salt in the electrolyte decreases, and the viscosity of the electrolyte also increases, which in turn reduces the conductivity of the electrolyte.

[0068] In this specification, the concentration units "M" and "mol / L" can be used interchangeably.

[0069] In some embodiments, the electrolyte of the present application optionally further comprises other functional additives, which may be any additives known in the art that are applicable in the context of the present application. For example, the electrolyte further comprises at least one of a flame retardant additive, an overcharge prevention additive, and a conductive additive. The electrolyte further comprises the additives to further improve the performance of the electrolyte.

[0070] In some embodiments, optionally, the acidity of the electrolyte is ≦50 ppm and the purity of each solvent used is ≧99.8%.

[0071] When the acidity and purity of the electrolyte are within the above ranges, the electrolyte has good stability and is less likely to cause side reactions, which contributes to improving the cycle performance of the secondary battery.

[0072] The acidity of the electrolyte in this application can be tested by a method commonly used in the art, specifically, see HG / T4067-2015, which describes that triethylamine standard solution can be used to titrate the free acid in the electrolyte.

[0073] It is explained that the electrolyte solution described in the present application can be prepared by a method commonly used by those skilled in the art so that those skilled in the art can understand. For example, the electrolyte solution described in the present application can be prepared by uniformly mixing and stirring the first solvent, the second solvent, the lithium salt, the film-forming additive, the other additives, etc. in a certain ratio under the protection of an inert gas.

[0074] [Secondary battery] A second aspect of the present application provides a secondary battery comprising the electrolyte solution according to the first aspect of the present application.

[0075] 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 and removed between the positive and negative electrodes. The electrolyte serves to conduct ions between the positive and negative electrodes. The separator is placed between the positive and negative electrodes, and serves mainly to prevent short circuits between the positive and negative electrodes, while allowing ions to pass through.

[0076] In some embodiments, the electrolyte injection coefficient of the secondary battery described herein is optionally 1.8-4g / Ah, optionally 2.4-3.2g / Ah. As an example, if the electrolyte injection coefficient of the secondary battery is 2.8g / Ah and the cell capacity is designed to be 3Ah, the electrolyte injection amount is 2.8*3g=8.4g.

[0077] The positive electrode plate, the negative electrode plate, and the separator of the secondary battery described in the present application will be described in detail below.

[0078] [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, the positive electrode film layer including a positive electrode active material.

[0079] As an example, the positive electrode current collector has two surfaces opposing each other in the thickness direction of the positive electrode current collector, and the positive electrode film layer is provided on either one or both of the two opposing surfaces of the positive electrode current collector.

[0080] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, the metal foil may be an aluminum foil. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0081] In some embodiments, optionally, based on the total weight of the positive electrode active material, the positive electrode active material of the secondary battery has a Mn element content of ≧25%; Optionally, LiM p Mn 2-p O 4 , Lin q Mn 1-q PO 4 Or Li 1+t Mn 1-w L w O 2+t wherein 0≦p≦1, 0≦q≦0.5, 0≦t≦1, 0≦w≦0.5; M, N, and L each independently represent one or more of Ni, Co, Fe, Cr, V, Ti, Zr, La, Ce, Rb, P, W, Nb, Mo, Sb, B, Al, and Si; More selectively, LiM p Mn 2-p O 4 Or Li 1+t Mn 1-w L w O 2+t one or more of More selectively, LiNi 0.5 Mn 1.5 O 4 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , Li 2 MnO 3, LiMnPO 4 One or more of the following:

[0082] When the positive electrode active material of the secondary battery is selected from the above types, it is possible to improve the energy density of the secondary battery, contribute to reducing the manufacturing cost, and cause less environmental pollution.

[0083] Optionally, in some embodiments, the particles of the positive electrode active material are single crystal or pseudo-single crystal.

[0084] When the positive electrode active material is a single crystal, the active material itself is less likely to be broken, reducing the probability of exposing new surfaces, and further reducing side reactions of the electrolyte, thereby improving the stability of the electrolyte.

[0085] In some embodiments, the particle size of the positive electrode active material is optionally 1 to 20 μm, and optionally 3 to 15 μm. The particle size of the positive electrode active material can be measured by a method commonly used in the art, for example, by testing with reference to the standard GB / T 19077-2016 / ISO 13320:2009.

[0086] In some embodiments, the specific surface area of ​​the positive electrode active material is optionally less than 1.5 m 2 / g or less, and selectively 0.1m 2 / g~1m 2 / g. The specific surface area of ​​the positive electrode active material can be measured by a method commonly used in the art, for example, the test can be performed with reference to the standard GB / T19587-2004 "Measurement of the specific surface area of ​​solid materials by gas adsorption BET method".

[0087] When the particle size and surface area of ​​the positive electrode active material are within the above ranges, it contributes to reducing side reactions and improving the stability of the electrolyte, and also helps to avoid the increase in energy consumption in the process and the deterioration of the processing performance of the positive electrode plate caused by an excessively large particle size.

[0088] In some embodiments, the positive electrode membrane layer optionally further includes a binder, for example, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0089] In some embodiments, the binder optionally comprises 0.1 to 3.5% of the total weight of the positive electrode membrane layer, optionally 0.5 to 2.5%.

[0090] In some embodiments, the positive electrode membrane layer optionally further comprises a conductive agent. For example, the conductive agent may comprise at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0091] In some embodiments, the conductive agent optionally comprises 0.05 to 5% of the total weight of the positive electrode membrane layer, and optionally 0.5 to 3%.

[0092] In some embodiments, the positive electrode plate can be manufactured by the following method. The components for manufacturing the positive electrode plate described above, such as the positive electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. The positive electrode slurry is applied to a positive electrode current collector, and after steps such as drying and cold pressing, a positive electrode plate can be obtained.

[0093] [Negative plate] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0094] As an example, the negative electrode current collector has two surfaces opposing each other in the thickness direction of the negative electrode current collector, and the negative electrode film layer is provided on either one or both of the two opposing surfaces of the negative electrode current collector.

[0095] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, the metal foil may be a copper foil. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0096] In some embodiments, the type of negative electrode active material may be a negative electrode active material for batteries known in the art. As an example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate. The silicon-based material may be selected from at least one of silicon alone, silicon oxygen compound, silicon carbon composite, silicon nitrogen composite, and silicon alloy. The tin-based material may be selected from at least one of tin alone, tin oxide compound, and tin alloy. 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 alone or in combination of two or more.

[0097] In some embodiments, the negative electrode membrane layer optionally further comprises a binder, which can be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0098] In some embodiments, the negative electrode membrane layer optionally further comprises a conductive agent, which can be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0099] In some embodiments, the negative electrode membrane layer optionally further comprises other auxiliary agents, such as a thickening agent (eg, sodium carboxymethylcellulose (CMC-Na)).

[0100] In some embodiments, the negative electrode plate can be manufactured by the following method. The components for manufacturing the negative electrode plate described above, such as the negative electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry. The negative electrode slurry is applied to a negative electrode current collector, and after processes such as drying and cold pressing, a negative electrode plate can be obtained.

[0101] [Separator] In some embodiments, the secondary battery further includes a separator. In the present application, the type of the separator is not particularly limited, and any known separator having a porous structure with good chemical stability and mechanical stability can be selected.

[0102] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, and is not particularly limited.

[0103] A third aspect of the present application provides a battery module including the secondary battery according to the second aspect of the present application.

[0104] A fourth aspect of the present application provides a battery pack including the battery module according to the third aspect of the present application.

[0105] A fifth aspect of the present application provides an electric device including at least one selected from the secondary battery according to the second aspect of the present application, the battery module according to the third aspect, or the battery pack according to the fourth aspect. The secondary battery, the battery module, or the battery pack may be used as a power source for the electric device, or may be used as an energy storage unit for the electric device. The electric device may include, but is not limited to, a mobile device (e.g., a mobile phone, a notebook computer, etc.), an electric vehicle (e.g., a secondary battery electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric car, a ship and a satellite, an energy storage system, etc.

[0106] The electrical device can be selected as a secondary battery, a battery module or a battery pack according to the needs of its use.

[0107] The secondary battery, battery module, battery pack, and electric device of the present application will be described below with appropriate reference to the drawings.

[0108] In some embodiments, the positive and negative plates and the separator can be manufactured into an electrode assembly by a winding or lamination process.

[0109] In some embodiments, the secondary battery may include an exterior body that can be used to package the electrode assembly and the electrolyte.

[0110] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a soft pack, such as a bag-type soft pack, etc. The material of the soft pack may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0111] In the present application, the shape of the secondary battery is not particularly limited and may be cylindrical, rectangular or any other shape. For example, FIG. 1 shows a secondary battery 5 having a rectangular structure as an example.

[0112] In some embodiments, referring to FIG. 2, the exterior body may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate surround the chamber to form a chamber. The case 51 has an opening communicating with the chamber, and the cover plate 53 may cover the opening to seal the chamber. The positive electrode plate, the negative electrode plate and the separator may form an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the chamber. The electrolyte infiltrates the electrode assembly 52. ​​The number of electrode assemblies 52 included in the lithium ion battery 5 may be one or more, and may be selected by those skilled in the art according to specific practical requirements.

[0113] In some embodiments, the secondary batteries can be assembled into a battery module, and the number of secondary batteries included in the battery module can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery module.

[0114] 5 Fig. 3 shows an example of a battery module 4. Referring to Fig. 3, in the battery module 4, the multiple secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the multiple secondary batteries 5 may be fixed by a fastening member.

[0115] Optionally, the battery module 4 may further include a case having an accommodation space, and the multiple secondary batteries 5 are accommodated in the accommodation space.

[0116] In some embodiments, the above battery modules can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0117] 4 and 5 show an example of a battery pack 1. Referring to Fig. 4 and Fig. 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box may include an upper box 2 and a lower box 3, and the upper box 2 may cover the lower box 3 to form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box according to any method.

[0118] 6 shows an example of an electric device, such as a secondary battery electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack or a battery module can be adopted to meet the high power and high energy density requirements for the secondary battery of the electric device.

[0119] Another example of the device may be a mobile phone, a tablet, a laptop, etc. Such devices usually require light weight and thinness, and may employ a secondary battery as a power source.

[0120] Working Example The following examples of the present application are described. The examples described below are illustrative and are merely for the purpose of interpreting the present application, and should not be understood as limiting the present application. If no specific techniques or conditions are specified in the examples, they are carried out according to the techniques or conditions described in the literature in the field, or according to the product specifications. If no manufacturer is specified for the reagents or equipment used, they are all ordinary products that are commercially available.

[0121] The origins of the raw materials used in the examples of this application are as shown in the table below. [Table 1]

[0122] Example 1 Electrolyte production Argon atmosphere glove box (H 2 O<0.1ppm, O 2 <0.1 ppm), referring to Table 2, various organic solvents were uniformly mixed in the mass ratios shown, salts and additives shown in Table 2 were added, and the mixture was stirred uniformly to obtain the electrolyte solution of Example 1.

[0123] Positive electrode plate manufacturing The positive electrode active material LNMO (i.e., LiNi 0.5 Mn 1.5 O 4 ), carbon black (Super P) as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder were mixed in a mass ratio of 96:2.5:1.5 in an appropriate amount of NMP as a solvent by thorough stirring to form a uniform positive electrode slurry, which was then uniformly applied to the surface of the aluminum foil of the positive electrode current collector, and then applied to both sides. After drying and cold pressing, a positive electrode plate was obtained. The amount of positive electrode active material carried on one side of the positive electrode current collector was 0.02 g / cm. 2 It was.

[0124] Negative plate manufacturing The negative electrode active material artificial graphite, the conductive agent carbon black (Super P), the binder styrene butadiene rubber, and the thickener sodium carboxymethyl cellulose were mixed in a mass ratio of 96:1:1:2 with an appropriate amount of deionized water as a solvent and thoroughly stirred to form a uniform negative electrode slurry, which was then uniformly applied to one side of the copper foil surface of the negative electrode current collector. After drying and cold pressing, a negative electrode plate was obtained. The amount of negative electrode active material carried on one side of the negative electrode current collector was 0.008 g / cm. 2 It was.

[0125] Separator A polypropylene film was used as a separator.

[0126] Secondary battery manufacturing The positive electrode plate, the separator, and the negative electrode plate were stacked in this order, and the separator was placed between the positive and negative electrodes to serve as an insulator, and the electrode assembly was placed in a battery case. After drying, an electrolyte was injected, and the secondary battery of Example 1 was manufactured through processes such as chemical formation and standing. The injection coefficient of the obtained secondary battery was 2.8 g / Ah.

[0127] Examples 2 to 11 and Comparative Examples 1 to 3 Unlike the conditions shown in Table 2, the positive electrode active material used in Example 11 and Comparative Example 3 was NCM523 (i.e., LiNi 0.5 Co 0.2 Mn 0.3 O 2 ), other conditions in Examples 2 to 11 and Comparative Examples 1 to 3 were the same as in Example 1.

[0128] Test methods for relevant parameters 1. Nuclear Magnetic Resonance Test 1.1. Hydrogen spectrum test Mix 25 mg of electrolyte and 25 mg of 4-fluoropyridine, then add the mixture to 0.5 g of acetonitrile-d3 to perform proton nuclear magnetic resonance test. In the obtained spectrum, the chemical shifts of hydrogen of 4-fluoropyridine are 7.09 ppm and 8.57 ppm, and the peak areas in the ranges of 7.0 ppm to 7.2 ppm and 8.45 ppm to 8.65 ppm are integrated, and the area obtained by integration is normalized to 1. In a similar manner, the peaks in the range of 0.5 ppm to 10 ppm are integrated, and the peak areas corresponding to the above-mentioned hydrogen of 4-fluoropyridine and the peak areas corresponding to the hydrogen of acetonitrile-d3 in the range of 2.0 ppm to 1.9 ppm are subtracted, and the remaining hydrogen spectrum peak areas are normalized to S H He wrote:

[0129] 1.2. Fluorine spectrum test Mix 25 mg of electrolyte and 25 mg of 4-fluoropyridine, then add the mixture to 0.5 g of acetonitrile-d3, and perform a fluorine-19 nuclear magnetic resonance test. In the obtained spectrum, integrate the fluorine peak area corresponding to 4-fluoropyridine in the range of -102 ppm to -104 ppm, and normalize the integrated area to 1. In a similar manner, integrate the peak area in the range of -280 ppm to 80 ppm, and normalize the peak area in the range of -72 ppm to -75 ppm (LiPF 6 ) and the peak areas corresponding to the fluorines of the lithium salts in the range of 51 ppm to 60 ppm (LiFSI), and the peak areas corresponding to the fluorines of 4-fluoropyridine in the range of -102 ppm to -104 ppm were subtracted, and the peak areas of the remaining fluorine spectra were normalized to S F He wrote:

[0130] 2. Cell Capacity (C) Test At 25°C, the lithium-ion battery was constant current charged at 0.1C to an upper cut-off voltage, followed by constant voltage charging at this voltage until the current was less than 0.05C, and then discharged at 0.1C to a lower cut-off voltage to obtain the discharge capacity C (Ah).

[0131] 3. Cycle performance test of secondary batteries At 25°C, the secondary battery was charged at a constant current of 0.1C to the upper cut-off voltage, then charged at a constant voltage of 0.05C at this cut-off voltage, and allowed to stand for 5 minutes, after which the secondary battery was discharged at a constant current of 0.1C to the lower cut-off voltage, which constitutes one charge-discharge cycle, and the discharge capacity this time is the initial discharge capacity of the secondary battery. The charge-discharge cycle was repeated according to the above method for the secondary battery until the discharge capacity after the cycle was attenuated to 70% of the initial discharge capacity, the test was terminated, and the number of cycles of the secondary battery at this time was recorded. The more cycles of the secondary battery, the longer the expected cycle life of the secondary battery.

[0132] 4. Secondary battery storage performance test At 25°C, the secondary battery was charged at a constant current of 0.1C to the upper cut-off voltage, and then at this cut-off voltage, was charged at a constant voltage of 0.05C, at which point the secondary battery was in a fully charged state. The fully charged secondary battery was stored in an environment of 60°C, taken out once every 10 days, and discharged at a constant current of 0.1C to the lower cut-off voltage, to obtain the discharge capacity after a certain period of storage. After that, the secondary battery was fully charged as above and stored again in an environment of 60°C until the discharge capacity of the secondary battery after storage attenuated to 70% of the initial discharge capacity, the test was terminated, and the total storage days of the secondary battery were recorded. The longer the storage days of the secondary battery, the longer the expected high-temperature storage life of the secondary battery.

[0133] It should be noted that in the above performance tests, the upper cutoff voltage of Examples 1 to 11 and Comparative Examples 1 to 2 is 4.9 V and the lower cutoff voltage is 3.5 V, and the upper cutoff voltage of Example 11 and Comparative Example 3 is 4.5 V and the lower cutoff voltage is 2.8 V. Table 2 shows the performance test results of Examples 1 to 12 and Comparative Examples 1 to 3.

[0134] [Table 2] JPEG2025515903000016.jpg225162

[0135] As can be seen from Table 2, when the electrochemical stability coefficient x of the electrolyte is 0.18 to 0.60, the secondary battery using the electrolyte has better storage performance and cycle performance than those of Comparative Examples 1 to 3. Also, when x is 0.25 to 0.55, the storage performance and cycle performance of the corresponding secondary battery are better. Also, by adjusting the amounts of the first and second solvents used, and the type and amount of the film-forming additive, the storage performance and cycle performance of the secondary battery can be further improved.

[0136] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and all embodiments that have substantially the same configuration as the technical idea within the scope of the technical solution of the present application and exhibit the same action and effect are included within the technical scope of the present application. In addition, various modifications that a person skilled in the art can conceive of to the embodiments and other forms formed by combining some of the components in the embodiments are also included within the scope of the present application, within the scope of the present application. [Explanation of symbols]

[0137] 1 Battery pack 2 Top Box 3 Lower Box 4 Battery Module 5 Secondary battery 51 cases 52 Electrode assembly 53 Top cover

Claims

1. An electrolyte comprising a solvent and a fluorine-containing lithium salt, the electrolyte having an electrochemical stability factor x=SF / (SF+4SH) of 0.18 to 0.6, optionally 0.25 to 0.55; The SF is the peak area of ​​fluorine corresponding to the lithium salt in the range of −280 ppm to 80 ppm, excluding the fluorine corresponding to 4-fluoropyridine, when a fluorine-19 nuclear magnetic resonance test is performed on a mixture of an electrolyte and 4-fluoropyridine in a weight ratio of 1:1, and the peak area of ​​fluorine corresponding to 4-fluoropyridine in the range of −102 ppm to −104 ppm is normalized to 1; The SH is the hydrogen peak area excluding hydrogen corresponding to acetonitrile-d3 and 4-fluoropyridine in the range of 0.5 ppm to 10 ppm when a proton nuclear magnetic resonance test is performed on a mixture of an electrolyte and 4-fluoropyridine in a weight ratio of 1:1, and the hydrogen peak areas corresponding to 4-fluoropyridine in the ranges of 7.0 ppm to 7.2 ppm and 8.45 ppm to 8.65 ppm are normalized to 1; The electrolyte is an electrolyte that does not contain acetonitrile-d3,4-fluoropyridine.

2. The electrolyte solution includes a first solvent and a second solvent, the first solvent is selected from one or more of a fluoroether, a fluorocarbonate, a fluorocarboxylate, a fluorobenzene, or a fluorosulfone; Selectively, 【Chemistry 13】 one or more of R1, R3, R5 and R13 are each independently selected from C1 to C6 fluoroalkanes; R2, R4, R6, R14, R15 and R16 are each independently selected from C1 to C6 alkanes or C1 to C6 fluoroalkanes; R7 to R12 are each independently selected from C1 to C6 fluoroalkanes, fluorine or hydrogen; at least one of R7 to R12 is selected from fluorine or a fluoroalkane; and at least one of R15 and R16 is selected from a C1 to C6 fluoroalkane; More selectively, 【Chemistry 14】 one or more of the second solvent is selected from one or more of a non-fluorocarbonate, a non-fluorocarboxylate, a non-fluoroether, or a non-fluorosulfone; Selectively, 【Chemistry 15】 one or more of R1', R2', R3', R13', R14' and R16' are each independently selected from a C1-C6 alkane; R4' and R15' are each independently selected from a C1-C6 alkane or hydrogen; 2. The electrolyte of claim 1, further optionally being 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.

3. The content y1 of the first solvent is 10 to 100%, optionally 45 to 100%, and further optionally 80 to 100% based on the total weight of the first solvent and the second solvent. The electrolyte solution according to claim 2.

4. The content y2 of the second solvent is 0 to 90%, optionally 0 to 55%, and further optionally 0 to 20%, based on the total weight of the first solvent and the second solvent. The electrolyte solution according to claim 2 or 3.

5. The content y1 of the first solvent and the content y2 of the second solvent satisfy y1 / y2≧0.82, optionally y1 / y2≧2.33, further optionally y1 / y2≧4, further optionally y1 / y2≧5.

67. The electrolyte solution according to any one of claims 3 to 4.

6. The electrolytic solution further includes a film-forming additive, and the film-forming additive is selected from one or more of a chain or cyclic sulfate ester, a chain or cyclic sulfonate ester, a chain or cyclic carbonate ester, a polycyclic sulfate ester, or a polycyclic sulfonate ester; Selectively, 【Chemistry 16】 one or more of More selectively, 【Chemistry 17】 The electrolyte solution according to any one of claims 1 to 5, which is one or more of the following:

7. The content of the film-forming additive is 0.1 to 10%, optionally 0.5 to 7%, and further optionally 1 to 5%, based on the total weight of the first solvent and the second solvent. The electrolyte solution according to claim 6.

8. Based on the total weight of the first solvent and the second solvent, the film-forming additive comprises: 【Chemistry 18】 The electrolyte solution according to claim 6 or 7, comprising:

9. 9. The electrolyte solution according to claim 1, wherein the lithium salt comprises one or more of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

10. The electrolyte according to any one of claims 1 to 9, wherein the concentration of the lithium salt is 0.7 to 2.5 mol / L, and optionally 1 to 1.5 mol / L.

11. The electrolyte according to any one of claims 1 to 10, wherein the acidity of the electrolyte is ≦50 ppm and the purity of each solvent used is ≧99.8%.

12. A secondary battery comprising the electrolyte solution according to any one of claims 1 to 11.

13. Based on the total weight of the positive electrode active material, the positive electrode active material of the secondary battery has a Mn element content of ≧25%, Optionally, LiMpMn ２－ｐ O ４ , LiNqMn １－ｑ P.O. ４ Or Li １＋ｔ Mn １－ｗ L ｗ O ２＋ｔ wherein 0≦p≦1, 0≦q≦0.5, 0≦t≦1, 0≦w≦0.5; M, N, and L each independently represent one or more of Ni, Co, Fe, Cr, V, Ti, Zr, La, Ce, Rb, P, W, Nb, Mo, Sb, B, Al, and Si; More optionally, LiM ｐ Mn ２－ｐ O ４ Or Li １＋ｔ Mn １－ｗ L ｗ O ２＋ｔ one or more of More preferably, LiNi ０．５ Mn １．５ O ４ , LiNi ０．５ Co ０．２ Mn ０．３ O ２ , Li ２ MnO ３ , LiMnPO ４ The secondary battery according to claim 12, wherein the secondary battery is one or more of the following:

14. 14. The secondary battery according to claim 12, wherein the particles of the positive electrode active material are single crystal or pseudo single crystal.

15. The secondary battery according to any one of claims 12 to 14, wherein the particle size of the positive electrode active material is 1 to 20 µm, and optionally 3 to 15 µm.

16. The specific surface area of ​​the positive electrode active material is 1.5 m ２ / g or less, and optionally 0.1m ２ / g to 1m ２ The secondary battery according to any one of claims 12 to 15, wherein the molecular weight is 1 / g.

17. A battery module comprising the secondary battery according to any one of claims 12 to 16.

18. A battery pack comprising the battery module according to claim 17.

19. An electric device comprising at least one of the secondary battery according to any one of claims 12 to 16, the battery module according to claim 17, or the battery pack according to claim 18.

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