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 electrolytes and secondary batteries, battery modules, battery packs, and electrical devices containing the same. [Background technology]

[0002] In recent years, as secondary batteries have become increasingly widely used in many industries, such as electric vehicles, electric motorcycles, aerospace, hydroelectric power plants, wind power plants, and solar power plants, 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 industrially available 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 urgently need to solve. Summary of the Invention [Problem to be solved by the invention]

[0003] The present application has been made in view of the above-mentioned 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] 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, wherein the electrolyte solution has 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 1:1 weight ratio mixture of electrolyte and 4-fluoropyridine 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; 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 when a proton nuclear magnetic resonance test is performed on 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 solution 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, 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 solution 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 R1, R3, R5 and R 13 are independently selected from C1 to C6 fluoroalkanes, and R2, R4, R6, R 14 , R 15 and R 16 are each independently selected from a C1-C6 alkane or a C1-C6 fluoroalkane, and R7 to R 12are each independently selected from C1 to C6 fluoroalkanes, fluorine or hydrogen, and R7 to R 12 at least one of R is selected from fluorine or a fluoroalkane; 15 and R 16 At least one of the groups is selected from C1 to C6 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 R1', R2', R3', R 13 ', R 14 ' and R 16 R' are independently selected from C1 to C6 alkanes, and R4' and R 15 ' are each independently selected from a C1-C6 alkane or hydrogen; More preferably, it 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 solution.

[0013] In any embodiment, optionally, the electrolyte solution further comprises a film-forming additive, wherein the film-forming additive is 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, reducing the loss of active lithium and further improving 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 comprises: [ka] Includes.

[0017] When the electrolyte solution contains the above-mentioned film-forming additive in the above-mentioned amount, it further improves the stability of the electrolyte solution, and contributes to 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 solution contains the lithium salt, the conductivity of the electrolyte solution 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 containing the electrolyte solution 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 O4, LiN q Mn 1-q PO4 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 O4 or Li 1+t Mn 1-w L w O 2+t one or more of More selectively, LiNi 0.5 Mn 1.5 O4, LiNi 0.5 Co 0.2 Mn 0.3 O2, Li2MnO3, LiMnPO4.

[0025] When the positive electrode active material of the secondary battery is selected from the above types, it contributes to improving the energy density of the secondary battery, reducing the manufacturing cost, and minimizing environmental pollution.

[0026] In any embodiment, optionally, the particles of the positive electrode active material are single crystal or quasi-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, and 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, side reactions are reduced, the stability of the electrolyte is improved, and it is also useful for avoiding 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 battery module manufacturing method 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 battery pack manufacturing method 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. [Effects of the Invention]

[0034] In the electrolyte solution described herein, the electrochemical stability coefficient x=S F / (S F +4S H) is 0.18 to 0.6, and preferably 0.25 to 0.55, which contributes to improving the stability of the electrolyte, resulting in good compatibility between the electrolyte and the positive and negative electrodes, reducing destruction of the surface of the positive electrode active material after the electrolyte generates hydrofluoric acid, reducing the exposure of new active sites, reducing side reactions of the electrolyte, and improving the storage performance and cycle performance of the secondary battery. Furthermore, when the electrochemical stability coefficient is within the above range, it reduces destruction of the negative electrode SEI film (Solid Electrolyte Interface) by the generated hydrofluoric acid, and helps to avoid a large amount of solvent being reduced at the negative electrode, which results in a large loss of active lithium and further deteriorates the storage performance and cycle performance of the secondary battery.

[0035] The battery module, battery pack, and electrical 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 explanation of the drawings]

[0036] [Figure 1] 1 is a schematic diagram of a secondary battery according to an embodiment of the present application; [Figure 2] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. [Figure 3] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 4] 1 is a schematic diagram of a battery pack according to an embodiment of the present application. [Figure 5] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application. [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 INVENTION

[0037] Hereinafter, with appropriate reference to the drawings, 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 details may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially the same structures may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate easy understanding by those skilled in the art. Furthermore, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the scope of the claims.

[0038] The "ranges" disclosed herein are defined in the form of lower and upper limits. 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 defined ranges may be inclusive or exclusive of the endpoints and may be arbitrarily combined; i.e., any lower limit may be combined with any upper limit to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are recited for a given parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if 1 and 2 are recited as minimum range values ​​and 3, 4, and 5 are recited as maximum range values, then the ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. Unless otherwise specified herein, a numerical range "a to b" represents a shorthand notation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 and 5" are listed herein, and "0 to 5" is simply shorthand for combinations of these numbers. Note that describing a parameter as an integer ≧2 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 embodiments and alternative 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 of the present application can be combined with each other to form new technical solutions.

[0041] Unless otherwise specified, all steps herein may be performed in sequence or randomly, preferably in sequence. For example, when the method includes steps (a) and (b), it 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 stated 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 may include steps (a), (c), and (b), or may include steps (c), (a), and (b).

[0042] Unless otherwise specified, the terms "comprise" and "comprises" used herein may be open-ended or closed-ended. For example, the terms "comprise" and "comprises" may indicate that the compound may further include or include other components not listed, or may include or include only the listed components.

[0043] Unless otherwise stated, the term "or" in this application 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 have found that most of the electrolytes in the prior art are not suitable for operation 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, generating large amounts of HF, which corrodes the positive electrode active material and deteriorates the performance of the secondary battery.

[0045] After extensive experiments, 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 is x=S F / (S F +4S H It has been unexpectedly discovered that when the ratio (R) of the electrolyte is 0.18 to 0.6, and preferably 0.25 to 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. Furthermore, by further adjusting the types and amounts of various solvents and additives in the electrolyte, the storage performance and cycle performance of the secondary battery can be further improved.

[0046] [Electrolyte] A first aspect of the present application is an electrolyte solution containing a solvent and a fluorine-containing lithium salt, wherein the electrolyte solution has an electrochemical stability coefficient x=S F / (S F +4S H ) is 0.18 to 0.6, and optionally 0.25 to 0.55; The above S F is the peak area of ​​fluorine excluding that of the lithium salt and that of 4-fluoropyridine in the range of -280 ppm to 80 ppm when a 1:1 weight ratio mixture of electrolyte and 4-fluoropyridine 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. The above S His 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 proton nuclear magnetic resonance test is performed on 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 solution 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 It has been found that when x is 0.18 to 0.6, it contributes to improving the stability of the electrolyte, resulting in good compatibility between the electrolyte and the positive and negative electrodes, reducing damage to the surface of the positive electrode active material after the electrolyte generates hydrofluoric acid, reducing the exposure of new active sites, reducing side reactions in the electrolyte, and improving the storage and cycling performance of the secondary battery. Furthermore, when the electrochemical stability coefficient is within the above range, it also helps reduce damage to the negative electrode SEI film by the generated hydrofluoric acid, preventing the reduction of a large amount of solvent at the negative electrode, resulting in a large loss of active lithium and further deteriorating the storage and cycling performance of the secondary battery. Optionally, when x is 0.25 to 0.55, it further enhances the compatibility between the electrolyte and the positive and negative electrodes, contributing to further improving the storage and cycling 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, but this is because the 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 reference is also contained in the electrolyte, the characteristic peaks of the same components in the reference and electrolyte cannot be distinguished, and S F and SH This is because the measurement of NMR becomes inaccurate. Those skilled in the art should understand that when performing nuclear magnetic resonance testing, different deuterated solvents and reference materials 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 solution 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 R1, R3, R5 and R 13 are independently selected from C1 to C6 fluoroalkanes, and R2, R4, R6, R 14 , R 15 and R 16 are each independently selected from a C1-C6 alkane or a C1-C6 fluoroalkane, and R7 to R 12 are each independently selected from C1 to C6 fluoroalkanes, fluorine or hydrogen, and R7 to R 12 at least one of R is selected from fluorine or a fluoroalkane; 15 and R 16 At least one of the groups is selected from C1 to C6 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 R1', R2', R3', R 13 ', R 14 ' and R 16 R' are independently selected from C1 to C6 alkanes, and R4' and R 15 ' are each independently selected from a C1-C6 alkane or hydrogen; More preferably, it 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, promoting the formation of a dense protective film during the initialization stage, promoting desolvation, and further reducing side reactions of the solvent on the surfaces of the positive and negative electrodes, thereby improving the cycle performance of the secondary battery.

[0051] In some embodiments, the content y1 of the first solvent is optionally 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. For example, the content y1 of the first solvent may be 10%, 30%, 45%, 70%, 80%, 90%, or 100%.

[0052] In some embodiments, the content y2 of the second solvent is optionally 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. 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 solution 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 solution of the present invention is within the above range, this contributes to further improving the stability of the electrolyte solution.

[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 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 solution is further improved, which helps to improve the storage performance and cycle performance of the secondary battery.

[0060] In some embodiments, optionally, the electrolyte solution further comprises a film-forming additive, wherein the film-forming additive is 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 total weight of the first solvent and the second solvent, the film-forming additive comprises: [ka] Includes.

[0064] When the electrolyte solution contains the above-mentioned film-forming additive in the above-mentioned amount, it further improves the stability of the electrolyte solution, and contributes to 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 concentration, the viscosity of the electrolyte is appropriate, improving the conductivity of the electrolyte and further contributing to improving the performance of the secondary battery. However, if the concentration of the lithium salt in the electrolyte is too high, the overall concentration of the electrolyte increases, but the degree of dissociation of the salt in the electrolyte decreases, and the viscosity of the electrolyte also increases, which conversely 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 solution of the present application optionally further includes other functional additives, which may be any additives known in the art and applicable to the context of the present application. For example, the electrolyte solution further includes at least one of a flame retardant additive, an overcharge prevention additive, and a conductive additive. The inclusion of such additives in the electrolyte solution can further improve the performance of the electrolyte solution.

[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] As will be understood by those skilled in the art, the electrolyte solution described herein can be prepared by a method commonly used by those skilled in the art. For example, the electrolyte solution described herein can be prepared by uniformly mixing and stirring a first solvent, a second solvent, a lithium salt, a film-forming additive, other additives, etc. in a certain ratio under the protection of an inert gas.

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

[0075] Typically, a secondary battery comprises a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charge and discharge 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, located between the positive and negative electrodes, primarily serves 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 to 4 g / Ah, and optionally 2.4 to 3.2 g / Ah. For example, if the electrolyte injection coefficient of the secondary battery is 2.8 g / Ah and the cell capacity is designed to be 3 Ah, the injection amount is 2.8 * 3 g = 8.4 g.

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

[0078] [Positive electrode] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0079] As an example, the positive electrode current collector has two surfaces facing each other in the thickness direction thereof, and the positive electrode film layer is provided on either one or both of the two facing 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, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, or a silver alloy) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[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 O4, LiN q Mn 1-q PO4 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 O4 or Li 1+t Mn 1-w L w O 2+t one or more of More selectively, LiNi 0.5 Mn 1.5 O4, LiNi 0.5 Co 0.2 Mn 0.3 O2, Li2MnO3, LiMnPO4.

[0082] When the positive electrode active material of the secondary battery is selected from the above types, it contributes to improving the energy density of the secondary battery, reducing the manufacturing cost, and minimizing environmental pollution.

[0083] In some embodiments, the particles of the positive electrode active material are optionally single crystalline or quasi-single crystalline.

[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 in accordance with GB / T 19077-2016 / ISO 13320:2009.

[0086] In some embodiments, the specific surface area of ​​the positive electrode active material is optionally 1.5 m 2 / g or less, and selectively 0.1m 2 / g~1m 2 The specific surface area of ​​the positive electrode active material can be measured by a method commonly used in the art, for example, by referring 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, side reactions are reduced, the stability of the electrolyte is improved, and it is also useful for avoiding 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, such as at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and a 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, and optionally 0.5 to 2.5%.

[0090] In some embodiments, the positive electrode film layer optionally further includes a conductive agent, for example, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

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

[0092] In some embodiments, a 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, conductive agent, 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.

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

[0094] As an example, the negative electrode current collector has two surfaces facing each other in the thickness direction thereof, and the negative electrode film layer is provided on either one or both of the two facing 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, or silver alloy) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0096] In some embodiments, the negative electrode active material may be any negative electrode active material known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of tin, 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 also be used. These negative electrode active materials may be used alone or in combination.

[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 film layer optionally further comprises a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

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

[0100] In some embodiments, a 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, conductive agent, 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. The type of separator is not particularly limited in this application, and any separator with a known porous structure having good chemical stability and mechanical stability can be selected.

[0102] In some embodiments, the separator may be made of at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may 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 may be the same or different, and are 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, battery module, or battery pack may be used as a power source for the electric device or as an energy storage unit for the electric device. The electric device may include, but is not limited to, mobile devices (e.g., mobile phones, notebook computers, etc.), electric vehicles (e.g., secondary battery electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric cars, ships and satellites, energy storage systems, etc.

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

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

[0108] In some embodiments, the positive electrode plates, negative electrode plates, and separators can be manufactured into an electrode assembly by a winding process or a stacking 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, or a steel case. The exterior of the secondary battery may be a soft pack, such as a bag-type soft pack. The soft pack may be made of plastic, such as polypropylene, polybutylene terephthalate, or 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 side plates connected to the bottom plate, with the bottom plate and side plates surrounding the chamber to form a storage chamber. The case 51 may have an opening communicating with the storage chamber, and the cover plate 53 may cover the opening to seal the storage chamber. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the storage chamber. An electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the lithium-ion battery 5 may be one or more, and can be selected by those skilled in the art according to specific actual needs.

[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 those skilled in the art depending on 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 plurality of 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 plurality of secondary batteries 5 may be fixed by fastening members.

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

[0116] In some embodiments, the 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 FIGS. 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 may include an upper box 2 and a lower box 3, and the upper box 2 may cover the lower box 3 to form an enclosed 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. A battery pack or a battery module can be adopted to meet the high power and high energy density requirements of the secondary battery of the electric device.

[0119] Other example devices may be mobile phones, tablets, laptops, etc. Such devices typically require light weight and thinness, and can employ secondary batteries as their power source.

[0120] Example Examples of the present application are described below. The examples described below are illustrative and are intended merely to interpret the present application and should not be understood as limiting the present application. If specific techniques or conditions are not 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 the manufacturers of the reagents or equipment used are not specified, they are all commercially available ordinary products.

[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 In a glove box (H2O<0.1 ppm, O2<0.1 ppm) under an argon atmosphere, various organic solvents were uniformly mixed in the mass ratios shown in Table 2, and the salts and additives shown in Table 2 were added and 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 O4), conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 96:2.5:1.5 with an appropriate amount of NMP solvent and thoroughly stirred to form a uniform positive electrode slurry. The positive electrode slurry was then uniformly applied to the surface of the aluminum foil positive electrode current collector, and then coated on both sides. After drying and cold pressing, a positive electrode plate was obtained. The amount of positive electrode active material carried on one side of the positive electrode current collector was 0.02 g / cm. 2 It was.

[0124] Negative electrode 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 the solvent, and thoroughly stirred to form a uniform negative electrode slurry. The negative electrode slurry was then uniformly coated on 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 negative electrode active material loading 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, separator, and negative electrode plate were stacked in this order, with a separator interposed between the positive and negative electrode plates to serve as an insulator, the electrode assembly was placed in a battery case, and after drying, an electrolyte solution was injected, followed by further processes such as chemical formation and standing to produce the secondary battery of Example 1. The injection coefficient of the obtained secondary battery was 2.8 g / Ah.

[0127] Examples 2 to 11 and Comparative Examples 1 to 3 The conditions are different from those shown in Table 2, and the positive electrode active material used in Example 11 and Comparative Example 3 is NCM523 (i.e., LiNi 0.5 Co 0.2 Mn 0.3 Other than the above, the other conditions of Examples 2 to 11 and Comparative Examples 1 to 3 were the same as those of Example 1.

[0128] Test methods for relevant parameters 1. Nuclear Magnetic Resonance Test 1.1. Hydrogen Spectrum Test A proton nuclear magnetic resonance test was performed by mixing 25 mg of electrolyte and 25 mg of 4-fluoropyridine, then adding the mixture to 0.5 g of acetonitrile-d3. In the resulting spectrum, the chemical shifts of the 4-fluoropyridine hydrogens were 7.09 ppm and 8.57 ppm. The peak areas in the ranges of 7.0 ppm to 7.2 ppm and 8.45 ppm to 8.65 ppm were integrated and normalized to 1. Using a similar method, the peaks in the range of 0.5 ppm to 10 ppm were integrated, and the peak areas corresponding to the 4-fluoropyridine hydrogens and the peak areas corresponding to the acetonitrile-d3 hydrogens in the range of 2.0 ppm to 1.9 ppm were subtracted. After normalizing the remaining hydrogen peak areas, the S H He wrote:

[0129] 1.2. Fluorine Spectrum Test 25 mg of electrolyte and 25 mg of 4-fluoropyridine were mixed, and then the mixture was added to 0.5 g of acetonitrile-d3 for a fluorine-19 nuclear magnetic resonance test. In the resulting spectrum, the fluorine peak area corresponding to 4-fluoropyridine within the range of -102 ppm to -104 ppm was integrated and normalized to 1. Similarly, the peak area within the range of -280 ppm to 80 ppm was integrated, and the peak areas corresponding to the fluorine of lithium salts within the ranges of -72 ppm to -75 ppm (LiPF6) and 51 ppm to 60 ppm (LiFSI) and the peak area corresponding to 4-fluoropyridine within the range of -102 ppm to -104 ppm were subtracted. After normalizing the peak areas of the remaining fluorine spectrum, the S was obtained. F He wrote:

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

[0131] 3. Secondary battery cycle performance test At 25°C, the secondary battery was charged at a constant current of 0.1C to the upper cutoff voltage, followed by a constant voltage charge at this cutoff voltage until the current reached 0.05C. After allowing to stand for 5 minutes, the secondary battery was discharged at a constant current of 0.1C to the lower cutoff voltage. This constitutes one charge-discharge cycle, and the discharge capacity this time is the initial discharge capacity of the secondary battery. The secondary battery was repeatedly charged and discharged according to the above method until the discharge capacity after the cycle had decayed to 70% of the initial discharge capacity. The test was terminated, and the number of cycles of the secondary battery at this point was recorded. The higher the number of 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 cutoff voltage, followed by a constant voltage charge at this cutoff voltage until the current reached 0.05C, at which point the secondary battery was fully charged. The fully charged secondary battery was stored at 60°C and removed every 10 days and discharged at a constant current of 0.1C to the lower cutoff voltage to obtain the discharge capacity after a certain period of storage. The secondary battery was then fully charged as described above and stored again at 60°C until the discharge capacity after storage had decayed to 70% of the initial discharge capacity. The test was terminated and the total number of days the secondary battery was stored was recorded. The longer the storage period, 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 and 2 was 4.9 V and the lower cutoff voltage was 3.5 V, and the upper cutoff voltage of Example 11 and Comparative Example 3 was 4.5 V and the lower cutoff voltage was 2.8 V. Table 2 shows the performance test results of Examples 1 to 12 and Comparative Examples 1 to 3.

[0134] [Table 2] JPEG0007771433000015.jpg225162

[0135] As can be seen from Table 2, when the electrochemical stability coefficient x of the electrolyte solution is 0.18 to 0.60, the secondary battery using the electrolyte solution has better storage performance and cycle performance than 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. Furthermore, 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-described embodiments. The above-described embodiments are merely examples, and all embodiments that have substantially the same configuration as the technical idea and exhibit the same functions and effects within the scope of the technical solution of the present application are encompassed within the technical scope of the present application. Furthermore, various modifications that can be conceived by a person skilled in the art to the embodiments and other forms constructed by combining some of the components of the embodiments are also encompassed within the scope of the present application, as long as they do not deviate from the gist of the present application. [Explanation of symbols]

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

Claims

1. An electrolyte solution comprising a solvent and a fluorine-containing lithium salt, wherein the electrolyte solution has an electrochemical stability factor x=SF / (SF+4SH) of 0.18 to 0.6; The 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 hydrogen peak area excluding the hydrogen corresponding to acetonitrile-d3, 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 does not contain acetonitrile-d3,4-fluoropyridine.

2. The electrolyte according to claim 1, wherein the electrochemical stability coefficient x = SF / (SF + 4SH) of the electrolyte is 0.25 to 0.

55.

3. 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; 3. The electrolyte solution of claim 1, wherein the second solvent is selected from one or more of a non-fluorocarbonate, a non-fluorocarboxylate, a non-fluoroether, or a non-fluorosulfone.

4. The first solvent is 【Chemistry 14】 4. The electrolyte solution according to claim 3, wherein the electrolyte solution is one or more of:

5. The electrolyte solution described in claim 3, wherein the second solvent is one or more of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate.

6. 4. The electrolyte solution according to claim 3, wherein the content y1 of the first solvent is 10 to 100% based on the total weight of the first solvent and the second solvent.

7. 4. The electrolyte solution according to claim 3, wherein the content y2 of the second solvent is 0 to 90% based on the total weight of the first solvent and the second solvent.

8. The electrolyte solution according to claim 6 , wherein the content y1 of the first solvent and the content y2 of the second solvent satisfy y1 / y2≧0.

82.

9. 4. The electrolytic solution according to claim 3, further comprising a film-forming additive 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.

10. The film-forming additive is 【Chemistry 16】 10. The electrolyte solution of claim 9, wherein the electrolyte solution is one or more of:

11. The electrolyte solution according to claim 9, wherein the content of the film-forming additive is 0.1 to 10% based on the total weight of the first solvent and the second solvent.

12. Based on the total weight of the first solvent and the second solvent, the film-forming additive comprises: [Chemistry 18] The electrolyte solution of claim 9 comprising:

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

14. 3. The electrolyte solution according to claim 1, wherein the concentration of the lithium salt is 0.7 to 2.5 mol / L.

15. 3. The electrolyte according to claim 1, wherein the acidity of the electrolyte is ≦50 ppm, and the purity of each solvent used is ≧99.8%.

16. A secondary battery comprising the electrolytic solution according to claim 1 or 2.

17. The positive electrode active material of the secondary battery has a manganese element content of ≧25% based on the total weight of the positive electrode active material, 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; 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.

18. 18. The secondary battery according to claim 17, wherein the particles of the positive electrode active material are single crystal or pseudo-single crystal.

19. 18. The secondary battery according to claim 17, wherein the particle size of the positive electrode active material is 1 to 20 μm.

20. The specific surface area of ​​the positive electrode active material is 1.5 m ２ 18. The secondary battery according to claim 17, wherein the SiO2 content is 0.1 / g or less.

21. A battery module comprising the secondary battery according to claim 16.

22. A battery pack comprising the battery module of claim 21.

23. 23. An electrical device comprising the battery pack of claim 22.

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