Electrolyte, secondary battery thereof and electric device

Abstract

The invention relates to the technical field of batteries, and discloses an electrolyte which comprises a solvent and a lithium salt, the polarity parameter MPI of the solvent is 8.5 gt; mPI is greater than or equal to 4.5, and the relative molecular mass N of the lithium salt meets 0 lt; n < = 120; the lithium ion concentration M in the electrolyte is more than or equal to 4 mol / L and less than or equal to 7 mol / L. The battery using the electrolyte formed by matching the polar solvent and the lithium salt has good cycle performance.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to an electrolyte and a secondary battery and an electrical device using the electrolyte. Background Art

[0002] Secondary batteries have the advantages of high energy density, long service life, and wide operating voltage range, and have been widely used in various fields. With the popularization of secondary batteries, users have put forward higher requirements for the performance of secondary batteries. The core components of batteries generally include positive electrodes, negative electrodes, separators, and electrolytes. The electrolyte plays the role of conducting ions between the positive and negative electrodes and has an important influence on the performance of the battery. Therefore, it is necessary to continuously research and develop new electrolyte materials. Summary of the invention

[0003] The electrolyte of the present invention cooperates with the polar solvent and the lithium salt so that the battery using the electrolyte can have good cycle performance. Under the testing method of the present invention, the battery using the electrolyte provided by the present invention has a cycle number between 1000 and 1350.

[0004] In a first aspect of the present invention, an electrolyte is provided. The electrolyte comprises: a solvent and a lithium salt; the polarity parameter of the solvent is 8.5>MPI≥4.5, the relative molecular mass of the lithium salt is ≤120; and the lithium ion concentration M in the electrolyte is in the range of 4mol / L≤M≤7mol / L.

[0005] Solvents with high polarity (polarity parameter ≥ 4.5) can improve the solubility of lithium salts with low relative molecular mass (relative molecular mass ≤ 120), so that lithium salts with low relative molecular mass are no longer limited by the solubility of carbonate solvents. High concentration (4mol / L≤M) of lithium salts can change the solvation structure of the electrolyte, so that there are no free solvent molecules on the surface of the negative electrode, and even if the polarity of the solvent molecules is high, it will not damage the negative electrode interface. Batteries using this electrolyte can have good cycle performance.

[0006] In some embodiments, the lithium ion concentration M in the electrolyte is in the range of 4.5 mol / L≤M≤6.5 mol / L. By controlling the appropriate lithium salt concentration, the battery can have better cycle performance.

[0007] In some embodiments, further, the relative molecular mass of the lithium salt in the electrolyte is: 25 <N≤75。

[0008] In some embodiments, the lithium salt comprises an inorganic lithium salt.

[0009] In some embodiments, the lithium salt includes: one or more of lithium nitrate, lithium nitrite, lithium fluoride, lithium nitride, lithium sulfide, lithium sulfate, lithium sulfite, lithium phosphate, and lithium phosphite.

[0010] In some embodiments, the polarity parameter MPI of the solvent satisfies: 7.5>MPI≥6.

[0011] In some embodiments, the solvent includes one or more of amides, esters, ethers, and sulfones.

[0012] In some embodiments, the solvent includes: N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, isopropyl acetate, methyl ethyl ketone, pyridine, dioxane, acetone, nitromethane, acetic acid, acetonitrile, aniline, dimethylformamide or one or more of the homologues of the above substances.

[0013] A second aspect of the present invention provides a battery comprising the electrolyte.

[0014] A third aspect of the present invention provides an electrical device comprising the battery.

[0015] The invention can make the lithium ion battery have good cycle performance by matching a solvent with a strong polarity with a lithium salt with a small relative molecular mass and a high concentration. DETAILED DESCRIPTION

[0016] In order to make the technical solution of the present application clearer and easier to understand, the specific implementation methods of the present application are described in detail below, but unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of actually the same structure may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and facilitate the understanding of those skilled in the art.

[0017] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. If not otherwise specified, the "includes", "comprising", "having" and any variations thereof mentioned in the present application are intended to cover non-exclusive inclusions. For example, the "includes" and "comprising" may mean that other components not listed may also be included or contained, or only the listed components may be included or contained.

[0018] If not specifically 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 of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0019] If not otherwise specified, in this application, the terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. If not otherwise specified, in this application, the term "multiple" refers to more than two (including two), similarly, "multiple groups" refers to more than two (including two), and "multiple pieces" refers to more than two (including two).

[0020] Unless otherwise specified, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0021] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers.

[0022] For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0023] Some embodiments of the present application provide a secondary battery. A secondary battery generally includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the battery charge and discharge process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0024] The present application also provides an electrical device, which includes a secondary battery provided by the present application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto. Among them, the mobile device may be, for example, a mobile phone, a laptop computer, etc.; the electric vehicle may be, for example, a pure 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., but are not limited thereto.

[0025] Positive electrode

[0026] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0027] As a non-limiting example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0028] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0029] In some embodiments, the positive electrode active material may adopt a positive electrode active material for a battery known in the art. As a non-limiting example, the positive electrode active material may include one or more of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide (such as LiCoO2), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi1 / 3Co1 / 3Mn1 / 3O2 (also referred to as NCM333), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523), LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211), LiNi0.6Co0.2Mn0.2O2 (also referred to as NCM622), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811), etc. Non-limiting examples of lithium nickel cobalt aluminum oxides may include LiNi0.85Co0.15Al0.05O2. New materials obtained by appropriate modification of the listed positive electrode active materials also fall within the scope of positive electrode active materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode active materials, and a non-limiting example is coating modification.

[0030] In some embodiments, the positive electrode active material layer may also optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0031] In some embodiments, the positive electrode active material layer may further optionally include a conductive agent. As non-limiting examples, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0032] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on at least one side of the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained. The type of solvent can be selected from but not limited to any one of the aforementioned embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode collector coated with the positive electrode slurry can be on a single surface of the positive electrode collector or on both surfaces of the positive electrode collector. The surface of the positive electrode collector coated with the positive electrode slurry can be on a single surface of the positive electrode collector or on both surfaces of the positive electrode collector.

[0033] Negative electrode

[0034] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0035] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0036] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0037] In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0038] In some embodiments, the negative electrode film layer may further include a binder. The binder may 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).

[0039] In some embodiments, the negative electrode film layer may further include 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.

[0040] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0041] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0042] Isolation film

[0043] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0044] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0045] Electrolyte

[0046] The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The electrolyte of the present application includes: a solvent and a lithium salt.

[0047] The polarity parameter MPI of the solvent satisfies: 8.5 > MPI ≥ 4.5, and further, 7.5 > MPI ≥ 6;

[0048] The polarity parameter MPI can be obtained through the molecular wave function property database iMolS.

[0049] Polarity parameters of some common compounds: Methyl ethyl ketone, 4.5; Pyridine, 5.3; Dioxane, 4.8; Acetone, 5.4; Nitromethane, 6; Acetonitrile (AN), 6.2; Aniline, 6.3; Dimethylformamide (DMF), 6.4; Dimethyl sulfoxide (DMSO), 7.2; Tetrahydrofuran (THF), 6.3; Isopropyl acetate (EP), 6.5.

[0050] The relative molecular mass N of the lithium salt satisfies: 0 < N ≤ 120, and further, 25 < N ≤ 75.

[0051] The range of the lithium ion concentration M in the electrolyte is: 4 mol / L ≤ M ≤ 7 mol / L, and further, 4.5 mol / L ≤ M ≤ 6.5 mol / L.

[0052] In some embodiments, the lithium salt includes an inorganic lithium salt. In some embodiments, the lithium salt includes: one or more of lithium nitrate, lithium nitrite, lithium fluoride, lithium nitride, lithium sulfide, lithium sulfate, lithium sulfite, lithium phosphate, and lithium phosphite.

[0053] In some embodiments, the solvent includes: one or more of amides, esters, ethers, and sulfones. In some embodiments, the solvent includes: one or more of N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, isopropyl acetate, methyl ethyl ketone, pyridine, dioxane, acetone, nitromethane, acetic acid, acetonitrile, aniline, dimethylformamide, and homologues of the above substances.

[0054] Cycling performance test

[0055] The cycle performance of the battery can be characterized by the number of cycles when its capacity is reduced to 80% of the initial capacity. At 25°C, the battery is left to stand for 2 hours, charged to 4.0V at 0.33C, and then charged at a constant voltage at 4.0V until the current is less than 0.05C; after standing for 5 minutes, it is discharged to 2.0V at 0.33C, and the capacity is recorded as D0. One charge and one discharge is one cycle. Repeat the above process until the discharge capacity of the nth cycle is Dn, and the capacity retention rate Dn / D0 = 80%, and the value of n is the number of cycles.

[0056] Material detection

[0057] The electrolyte in the battery is analyzed by inductively coupled plasma mass spectrometry (ICP) and gas chromatography-mass spectrometry (GCMS) to analyze the composition of the electrolyte, analyze whether lithium salts such as lithium nitrate are used in the electrolyte, and calculate their concentrations. Among them, ICP is used to analyze the absolute content of lithium ions in the electrolyte, and GCMS is used to analyze the main structure and composition of organic solvents in the electrolyte.

[0058] The embodiments described below are exemplary and are only used to explain the present application, and cannot be construed as limiting the present application. If the technology or conditions are not specifically noted in the embodiment, the technology or conditions described in the literature in this area or the product specification are carried out. The reagents or instruments used are not particularly noted, and are all conventional products that can be obtained commercially, and corresponding cost data can be obtained. When comparing cost data, normalization is performed based on comparative example 3. In industrial production, the cost of raw materials has an important influence on whether large-scale mass production can be achieved. This explanation defines that the cost is 1, and it is defined as having medium difficulty in achieving large-scale mass production; the cost is greater than 1, and it is defined as high difficulty; the cost is less than 1, and it is defined as low difficulty.

[0059] Example 1

[0060] Electrolyte: Prepare a lithium salt solution with a lithium ion concentration of 4 mol / L in an environment with a dew point temperature of less than -30°C. For example, the solvent used is dimethyl sulfoxide (DMSO), whose polarity parameter MPI is 7.2. The lithium salt used is lithium nitrate, whose relative molecular mass N is 69. When preparing, the mass of lithium salt required to prepare the electrolyte of the required concentration can be calculated based on the molar mass of the corresponding lithium salt.

[0061] Positive electrode sheet: lithium iron phosphate positive electrode, conductive agent is conductive carbon black, binder is polyvinylidene fluoride (PVDF), add N-methylpyrrolidone (NMP), stir, coat and dry. The mass ratio of positive electrode active material lithium iron phosphate, conductive carbon black and binder is 96:2:2.

[0062] Negative electrode: Graphite negative electrode is used, the conductive agent is conductive carbon black, and the binder is a mixture of styrene-butadiene rubber and sodium carboxymethyl cellulose (mass ratio 1:1). The mass ratio of graphite, conductive carbon black: binder is 96:2:2.

[0063] Separator: Polyethylene diaphragm.

[0064] Battery assembly: stack the above-mentioned positive electrode sheet, isolation film, and negative electrode sheet so that the isolation film is between the positive and negative electrode sheets to play an isolating role, and then wind them to obtain a bare battery cell; place the bare battery cell in an outer packaging aluminum shell, dry it at 85°C for 6 hours, and then inject electrolyte at an injection coefficient of 3.5g / Ah. After vacuum packaging, standing, formation, shaping and other processes, a secondary battery is obtained.

[0065] Examples 2 to 5

[0066] The difference between Examples 2 to 5 and Example 1 is the lithium ion concentration in the electrolyte, see the table below for details. The rest is the same as Example 1.

[0067] Comparative Examples 1 to 2

[0068] The difference between Comparative Examples 1 and 2 and Example 1 is the lithium ion concentration in the electrolyte, as shown in the table below. The rest is the same as Example 1.

[0069] Comparative Example 3

[0070] Electrolyte: The lithium salt is LiPF6, and a solution with a lithium ion concentration of 1 mol / L is prepared; the solvent is a mixture of ethylene carbonate and diethyl carbonate (EC / DEC volume ratio 3:7). Others are the same as in Example 1.

[0071] Comparative Example 4

[0072] Electrolyte: The lithium salt is lithium bis(fluorosulfonyl)imide, and a solution with a lithium ion concentration of 1 mol / L is prepared; the solvent is a mixture of ethylene carbonate and diethyl carbonate (EC / DEC volume ratio 3:7). Others are the same as in Example 1.

[0073] Table 1 Battery cycle performance and cost corresponding to different lithium ion concentrations in the electrolyte

[0074]

[0075]

[0076] Examples 1 to 5 and Comparative Examples 1 to 2 illustrate that when the lithium ion concentration in the electrolyte is controlled within a suitable range, the battery can have better cycle performance. Comparative Examples 3 and 4 are common electrolyte systems in the prior art, and Examples 1 to 5 of the present invention achieve substantially the same cycle performance (cycle number between 1050-1350) and significantly reduce the cost. Accordingly, the mass production difficulty of Examples 1-5 is low, while Comparative Examples 3-4 are medium and high.

[0077] Example 6

[0078] Electrolyte: A lithium salt solution with a lithium ion concentration of 5 mol / L was prepared under an environment with a dew point temperature of less than -30°C. The solvent used was DMSO, whose polarity parameter MPI was 7.2. The lithium salt used was lithium nitrate, whose relative molecular mass N was 69. Others were the same as in Example 1.

[0079] Embodiment 7-9

[0080] The difference between Examples 7-9 and Example 6 is that the types of lithium salts are different, the relative molecular mass of lithium sulfate is 110; the relative molecular mass of lithium sulfide is 46; the relative molecular mass of lithium fluoride is 26, the relative molecular mass of lithium hexafluorophosphate is 152, and the relative molecular mass of lithium bis(fluorosulfonyl)imide is 202. See the table below for details. Others are the same as Example 6.

[0081] Table 2 Cyclic performance and cost of batteries corresponding to lithium salts with different relative molecular weights in the electrolyte

[0082]

[0083] Examples 6 to 9, Comparative Examples 3 and 4 illustrate that when the relative molecular mass of the lithium salt in the electrolyte is within a suitable range, the battery can have good cycle performance and low cost. Comparative Examples 3 and 4 are common electrolyte systems in the prior art, and Examples 6 to 9 of the present invention achieve substantially the same cycle performance (cycle number between 1050-1350) and significantly reduce the cost. Accordingly, the mass production difficulty of Examples 6-9 is low, while Comparative Examples 3-4 are medium and high.

[0084] Example 10

[0085] Electrolyte: A lithium salt solution with a lithium ion concentration of 5 mol / L was prepared under an environment with a dew point temperature of less than -30°C. The solvent used was acetonitrile (AN), and its polarity parameter MPI was 6.3. The lithium salt used was lithium nitrate, and its relative molecular mass N was 69. Others were the same as in Example 1.

[0086] Examples 11 to 13

[0087] The difference between Examples 11 to 13 and Comparative Example 5 and Example 10 is that the polarity parameters of the solvents used are different. Among them, the polarity parameter of acetonitrile (AN) is 6.3; the polarity parameter of dimethylformamide (DMF) is 6.4; the polarity parameter of dimethyl sulfoxide (DMSO) is 7.2. The polarity parameter of benzene (BP) is 2.7. Others are the same as Example 10.

[0088] Table 3 Cyclic performance and cost of batteries corresponding to solvents with different polarity parameters in the electrolyte

[0089]

[0090] Examples 10 to 12 and Comparative Example 5 illustrate that when the polarity parameters of the solvent in the battery electrolyte are controlled within a suitable range, the battery can have better cycle performance. Comparative Examples 3 and 4 are common electrolyte systems in the prior art, and Examples 10 to 13 of the present invention achieve substantially the same cycle performance (cycle number between 1050-1350) and significantly reduce the cost. Accordingly, the mass production difficulty of Examples 10-12 is low, while Comparative Examples 3-4 are medium and high.

[0091] The present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and the same effect as the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. An electrolyte, characterized in that: Comprising: A solvent and a lithium salt; the polarity parameter MPI of the solvent satisfies: 8.5 > MPI ≥ 4.5, and the relative molecular mass N of the lithium salt satisfies: 0 < N ≤ 120; the range of the lithium ion concentration M in the electrolyte is: 4 mol / L ≤ M ≤ 7 mol / L.

2. The electrolyte according to claim 1, characterized in that The range of the lithium ion concentration M in the electrolyte is: 4.5 mol / L ≤ M ≤ 6.5 mol / L.

3. The electrolyte according to any one of claims 1 to 2, characterized in that The relative molecular mass N of the lithium salt satisfies: 25 < N ≤ 75.

4. The electrolyte according to any one of claims 1 to 3, characterized in that The lithium salt includes an inorganic lithium salt.

5. The electrolyte according to any one of claims 1 to 4, characterized in that The lithium salt includes one or more of lithium nitrate, lithium nitrite, lithium fluoride, lithium nitride, lithium sulfide, lithium sulfite, lithium sulfate, and lithium phosphate.

6. The electrolyte according to any one of claims 1 to 5, characterized in that: The polarity parameter MPI of the solvent satisfies: 7.5 > MPI ≥ 6.

7. The electrolyte according to any one of claims 1 to 6, characterized in that The solvent includes one or two of amides, esters, ethers, and sulfones.

8. The electrolyte according to any one of claims 1 to 7, characterized in that: The solvent includes one or more of N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, isopropyl acetate, methyl ethyl ketone, pyridine, dioxane, acetone, nitromethane, acetic acid, acetonitrile, aniline, N,N-dimethylformamide, methanol, ethylene glycol, and homologues of the above substances.

9. A battery, characterized in that: Comprising the electrolyte according to any one of claims 1-8.

10. An electrical device, characterized in that: Comprising the battery according to claim 9.

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