Electrolyte and secondary battery

Abstract

The invention discloses an electrolyte and a secondary battery with the electrolyte, the electrolyte comprises an additive, the additive accounts for 0.1 wt%-3wt% of the electrolyte, and the additive comprises a compound as shown in a formula 1; in the formula, R1, R2, and R3 are each independently selected from a substituted or unsubstituted C6 to C20 aryl group, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C1 to C10 alkoxy group, a substituted or unsubstituted C2 to C6 alkenyl group, a substituted or unsubstituted C3 to C20 heterocyclic group, and a halogen. The electrolyte provided by the invention is beneficial to prolonging the service life of the secondary battery.

Description

[0001] This application is a divisional application. The application number of the original application is: 202410930400.6, the application date is July 11, 2024, and the name of the invention is: Electrolyte and secondary battery. Technical Field

[0002] The present application relates to the field of batteries, and in particular to an electrolyte and a secondary battery. Background Art

[0003] At present, electrochemical devices (e.g., lithium metal batteries) have been widely used in new energy electric vehicles, electronic products such as cameras, digital cameras, and 3C products due to their high energy density, high operating voltage, long life, and green environmental protection.

[0004] Lithium metal batteries generally include a positive electrode, a negative electrode, a separator and an electrolyte. In the related art, the electrolyte of lithium metal batteries has problems such as low conductivity, difficulty in ion movement, and high cost, which limits the further improvement of its performance and practical application. In addition, the electrolyte used for lithium metal batteries is generally a high-concentration or locally high-concentration electrolyte (for example, the concentration of lithium salt is above 1 mol / L), which has low conductivity and difficulty in ion movement, resulting in safety hazards such as overheating and even combustion inside the lithium metal battery with this electrolyte. Summary of the invention

[0005] In view of this, the present application provides an electrolyte and a secondary battery. The secondary battery having the electrolyte has a longer lifespan.

[0006] In a first aspect, an embodiment of the present application provides an electrolyte for a secondary battery, characterized in that the electrolyte includes an additive, the additive accounts for 0.1wt% to 3wt% of the electrolyte, and the additive includes a compound shown in Formula 1;

[0007]

[0008] wherein R1, R2 and R3 are each independently selected from substituted or unsubstituted C6 to C 20 Aryl, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C1 to C 10 alkoxy, substituted or unsubstituted C2 to C6 alkenyl, substituted or unsubstituted C3 to C 20 Heterocyclyl, halogen.

[0009] In some embodiments of the present application, R1, R2 and R3 are each independently selected from substituted or unsubstituted C6 to C 12 Aryl, substituted or unsubstituted C1 to C6 alkyl, substituted or unsubstituted C1 to C6 alkoxy, halogen.

[0010] In some embodiments of the present application, the additive is selected from at least one of triphenyl phosphine, tri-p-phenyl phosphine, diphenyl methoxy phosphine, tri(1-naphthyl) phosphine, tri-m-phenyl phosphine, dimethyl phenyl phosphine, diphenyl phosphine chloride and diethyl phenyl phosphine.

[0011] In some embodiments of the present application, the additive is selected from at least one of triphenylphosphine, tri(1-naphthyl)phosphine and diphenylphosphine chloride.

[0012] In some embodiments of the present application, the additive accounts for 0.5 wt % to 2 wt % of the electrolyte.

[0013] In some embodiments of the present application, the electrolyte further includes a lithium salt and a solvent, and the concentration of the lithium salt in the electrolyte is 0.01 mol / L to 0.3 mol / L; or

[0014] Calculated by mass percentage, the electrolyte includes: 1wt% to 6wt% of lithium salt; 93% to 98% of solvent; and 0.1wt% to 3wt% of additives.

[0015] In some embodiments of the present application, the lithium salt is selected from one or more of lithium difluorooxalatoborate, lithium difluorophosphate, lithium nitrate, lithium dioxalatoborate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorophosphate, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl imide), and lithium bis(fluorosulfonyl imide).

[0016] In some embodiments of the present application, the solvent is selected from cyclic ethers and / or esters; or,

[0017] The solvent is selected from at least one of tetrahydrofuran, 2-methyltetrahydrofuran, 4-methyl-1,3-dioxolane, dioxane, ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate and ethyl propyl carbonate.

[0018] In a second aspect of the present application, a secondary battery is provided, the secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator and the electrolyte.

[0019] In some embodiments of the present application, the negative electrode sheet includes lithium metal or lithium alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 It is a voltage curve diagram of the button cell in Comparative Example 1 of the present application;

[0022] Figure 2 It is a voltage curve diagram of the button cell in Comparative Example 2 of the present application;

[0023] Figure 3 is a voltage curve diagram of a button cell in Example 1 of the present application;

[0024] Figure 4 It is a voltage curve diagram of the fully electric button-type battery in Example 1, Comparative Example 1 and Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0027] In this application, unless otherwise stated, directional words such as "upper" and "lower" generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. In addition, in the description of this application, the term "including" means "including but not limited to". The terms first, second, third, etc. are used only as labels and do not impose numerical requirements or establish an order.

[0028] In this application, "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0029] In the present application, "at least one" means one or more, and "plurality" means two or more. "One or more", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0030] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0031] At present, electrochemical devices (e.g., lithium metal batteries) have been widely used in new energy electric vehicles, electronic products such as cameras, digital cameras, and 3C products due to their high energy density, high operating voltage, long life, and green environmental protection.

[0032] Lithium metal batteries generally include a positive electrode, a negative electrode, a separator and an electrolyte. In the related art, the electrolyte of lithium metal batteries has problems such as low conductivity, difficulty in ion movement, and high cost, which limits the further improvement of its performance and practical application. In addition, the electrolyte used for lithium metal batteries is generally a high-concentration or locally high-concentration electrolyte (for example, the concentration of lithium salt is above 1 mol / L), which has low conductivity and difficulty in ion movement, resulting in safety hazards such as overheating and even combustion inside the lithium metal battery with this electrolyte.

[0033] In view of this, the present application provides an electrolyte for a lithium metal battery. The concentration of lithium salt in the electrolyte of the present application is low, and the lithium metal battery having the electrolyte has high performance, high safety and long life. The electrolyte and lithium metal battery of the present application are further described in combination with the embodiments below.

[0034] The present application embodiment provides an electrolyte, the electrolyte comprising: a lithium salt, a solvent and an additive, wherein the additive comprises a compound shown in Formula 1;

[0035]

[0036] wherein R1, R2 and R3 are each independently selected from substituted or unsubstituted C6 to C 20 Aryl, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C1 to C 10 alkoxy, substituted or unsubstituted C2 to C6 alkenyl, substituted or unsubstituted C3 to C 20 Heterocyclyl, halogen.

[0037] It should be noted that C6 to C 20 The aryl group refers to an aryl group having 6 to 20 carbon atoms. 20 Aryl includes phenyl, tolyl, xylyl, and the like. Similarly, C1 to C 10 The alkyl group refers to an alkyl group having 1 to 10 carbon atoms. 10 Alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, etc. 10 The alkoxy group refers to an alkoxy group having 1 to 10 carbon atoms. 10 Alkoxy includes methoxy, ethoxy, propoxy, butoxy, etc. C2 to C6 alkenyl refers to an alkenyl group having 2 to 6 carbon atoms. Exemplarily, C2 to C6 alkenyl includes ethenyl, propenyl, butenyl, etc. C3 to C 20 The heterocyclic group refers to an oxirane group, a furanyl group, a thienyl group, a pyrrolyl group, etc. having 3 to 20 carbon atoms. The halogen group includes fluorine (F), chlorine (Cl), bromine (Br), and the like.

[0038] Preferably, R1, R2 and R3 are each independently selected from substituted or unsubstituted C6 to C 12 Aryl, substituted or unsubstituted C1 to C6 alkyl, substituted or unsubstituted C1 to C6 alkoxy, halogen.

[0039] Preferably, at least one of R1, R2 and R3 is a substituted or unsubstituted C6 to C 12 Aryl.

[0040] Specifically, the additive is selected from at least one of triphenyl phosphine, tri-p-phenyl phosphine, diphenyl methoxy phosphine, tri(1-naphthyl) phosphine, tri-m-phenyl phosphine, dimethyl phenyl phosphine, diphenyl phosphine chloride and diethyl phenyl phosphine.

[0041] In the embodiment of the present application, the concentration of the lithium salt is 0.01 mol / L to 0.3 mol / L. Preferably, the concentration of the lithium salt is 0.2 mol / L to 0.3 mol / L.

[0042] Compared with the existing electrolyte for lithium metal batteries, the concentration of lithium salt in the electrolyte provided by the embodiment of the present application is 0.01mol / L to 0.3mol / L, and the lithium salt in the electrolyte has an ultra-low concentration, which is conducive to reducing the production cost of the electrolyte. At the same time, by adding an additive containing the compound shown in Formula 1 to the electrolyte, the synergistic combination of the additive with a special structure and the ultra-low concentration of lithium salt is conducive to promoting the movement of lithium ions and improving the conductivity of the electrolyte; when the electrolyte is used in a lithium metal battery, it is conducive to promoting the formation of a dense and uniform SEI film, promoting the uniform deposition of lithium ions, and improving the performance, safety and life of the lithium metal battery.

[0043] In some embodiments of the present application, the electrolyte includes: 1 wt% to 6 wt% of lithium salt; 93% to 98% of solvent; and 0.1% wt% to 3 wt% of additives.

[0044] In some embodiments of the present application, the lithium salt is selected from one or more of lithium difluorooxalatoborate (LiDFOB), lithium difluorophosphate (LIDFOP), lithium nitrate (LINO3), lithium dioxalatoborate (LiBOB), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiCLO4), lithium difluorophosphate (LiCLO4), lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl imide) (LiTFSI), and lithium bis(fluorosulfonyl imide) (LiFSI).

[0045] In some embodiments of the present application, the solvent is selected from cyclic ethers and / or esters. It is understood that the selection of cyclic ethers and / or esters as solvents is beneficial to increase the voltage window. Exemplarily, the voltage window of the electrolyte is greater than 4.2V.

[0046] Exemplarily, the cyclic ether is selected from at least one of tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 4-methyl-1,3-dioxolane (4-MeDOL), and dioxane.

[0047] Illustratively, the ester is selected from at least one of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0048] The present application also provides a lithium metal secondary battery, which includes a positive electrode sheet, a negative electrode sheet, a separator and the above-mentioned electrolyte. Exemplarily, the negative electrode sheet is a lithium metal negative electrode.

[0049] The positive electrode includes a positive electrode active material. Exemplarily, the positive electrode active material is selected from at least one of iron phosphate, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, or nickel cobalt manganese oxide.

[0050] Example 1

[0051] (1) Preparation of electrolyte

[0052] Add 0.0091 g of triphenylphosphine (TPP) to 1 ml of tetrahydropyran (THP), stir well for 1 h. After complete dissolution, add 0.0003 mol of lithium difluorooxalate borate (LiDFOB, 0.051 g) and stir well to obtain the electrolyte. Among them, the mass percentage of TPP in the electrolyte is 1%, and the concentration of the lithium salt in the electrolyte is 0.28 M.

[0053] (2) Preparation of the positive electrode

[0054] Mix the ternary cathode material (LiNi 0.8 Co 0.1 Mn 0.1 O2), conductive agent Super P, and binder PVDF in a mass ratio of 8:1:1, disperse them in the organic solvent NMP (N-methylpyrrolidone), stir until stable and uniform to form the positive electrode slurry. Coat the positive electrode slurry on an aluminum foil with a thickness of 10 μm, dry it at 80 °C and then raise the temperature to 120 °C for further vacuum drying, and then roll and slice to make the positive electrode.

[0055] (3) Battery preparation

[0056] For the button cell: Under an inert atmosphere in the glove box with the moisture and oxygen content <0.1 PPM, assemble the negative electrode case丨spring washer丨spacer丨lithium sheet丨electrolyte丨separator丨lithium sheet丨positive electrode case in sequence to assemble the button cell. Among them, the thickness of the lithium sheet is 20 μm, the diameter is 14 mm, the thickness of the separator is 9 μm PE separator, the diameter is 16 mm, the electrolyte dosage for each button cell is 20 μL, and 10 μL is added to each side. Press at 800 kPa for 5 s to complete the assembly and obtain the required secondary battery.

[0057] For the full button cell: Under an inert atmosphere in the glove box with the moisture and oxygen content <0.1 PPM, assemble the negative electrode case丨spring washer丨spacer丨lithium sheet丨electrolyte丨separator丨positive electrode丨positive electrode case in sequence to assemble the full button cell.

[0058] Example 2

[0059] The difference from Example 1 is as follows:

[0060] (1) Preparation of electrolyte

[0061] Add a certain amount of triphenylphosphine (TPP) to 1 ml of tetrahydropyran (THP), stir well for 1 h. After complete dissolution, add lithium difluorooxalate borate (LiDFOB) and stir well to obtain the electrolyte. Among them, the mass percentage of TPP in the electrolyte is 2%, and the concentration of the lithium salt in the electrolyte is 0.28 M.

[0062] Example 3

[0063] The difference between it and Example 1 is that:

[0064] (1) Preparation of electrolyte

[0065] A certain amount of triphenylphosphine (TPP) is added to 1 ml of tetrahydropyran (THP), stirred for 1 hour, and then lithium difluorooxalate borate (LiDFOB) is added after being fully dissolved, and stirred to obtain an electrolyte. The mass percentage of TPP in the electrolyte is 3%, and the concentration of lithium salt in the electrolyte is 0.28M.

[0066] Example 4

[0067] The difference between it and Example 1 is that:

[0068] (1) Preparation of electrolyte

[0069] A certain amount of triphenylphosphine (TPP) is added to 1 ml of tetrahydropyran (THP), stirred for 1 hour, and then lithium difluorooxalate borate (LiDFOB) is added after being fully dissolved, and stirred to obtain an electrolyte. The mass percentage of TPP in the electrolyte is 1%, and the concentration of lithium salt in the electrolyte is 0.1M.

[0070] Example 5

[0071] The difference between it and Example 1 is that:

[0072] (1) Preparation of electrolyte

[0073] A certain amount of triphenylphosphine (TPP) is added to 1 ml of tetrahydropyran (THP), stirred for 1 hour, and then lithium difluorooxalate borate (LiDFOB) is added after being fully dissolved, and stirred to obtain an electrolyte. The mass percentage of TPP in the electrolyte is 1%, and the concentration of lithium salt in the electrolyte is 0.4M.

[0074] Example 6

[0075] The difference between it and Example 1 is that:

[0076] (1) Preparation of electrolyte

[0077] A certain amount of triphenylphosphine (TPP) is added to 1 ml of tetrahydropyran (THP), stirred for 1 hour, and then lithium difluorooxalate borate (LiDFOB) is added after being fully dissolved, and stirred to obtain an electrolyte. The mass percentage of TPP in the electrolyte is 1%, and the concentration of lithium salt in the electrolyte is 0.8M.

[0078] Example 7

[0079] The difference between it and Example 1 is that:

[0080] (1) Preparation of electrolyte

[0081] A certain amount of diphenylphosphine chloride (CDPP) is added to 1 ml of tetrahydropyran (THP), stirred for 1 hour, and then lithium difluorooxalate borate (LiDFOB) is added after being fully dissolved, and stirred to obtain an electrolyte. The mass percentage of CDPP in the electrolyte is 1%, and the concentration of lithium salt in the electrolyte is 0.28M.

[0082] Example 8

[0083] The difference between it and Example 1 is that:

[0084] (1) Preparation of electrolyte

[0085] A certain amount of tri(1-naphthyl)phosphine (TNPP) was added to 1 ml of tetrahydropyran (THP), and the mixture was stirred for 1 hour. After the mixture was fully dissolved, lithium difluorooxalate borate (LiDFOB) was added thereto, and the mixture was stirred for a long time to obtain an electrolyte. The mass percentage of CDPP in the electrolyte was 1%, and the concentration of lithium salt in the electrolyte was 0.28 M.

[0086] Example 9

[0087] The difference between it and Example 1 is that:

[0088] (1) Preparation of electrolyte

[0089] A certain amount of tri(1-naphthyl)phosphine (TPP) and diphenylphosphine chloride (CDPP) were added to 1 ml of tetrahydropyran (THP), stirred for 1 hour, and then lithium difluorooxalate borate (LiDFOB) was added after being fully dissolved, and stirred to obtain an electrolyte. The mass percentage of TPP in the electrolyte was 0.5%, the mass percentage of CDPP in the electrolyte was 0.5%, and the concentration of lithium salt in the electrolyte was 0.28M.

[0090] Example 10

[0091] The difference between it and Example 1 is that:

[0092] (1) Preparation of electrolyte

[0093] A certain amount of triphenylphosphine (TPP) is added to 1 ml of tetrahydropyran (THP), stirred for 1 hour, and then lithium difluorooxalate borate (LiDFOB) is added after being fully dissolved, and stirred to obtain an electrolyte. The mass percentage of TNPP in the electrolyte is 0.1%, and the concentration of lithium salt in the electrolyte is 0.28M.

[0094] Comparative Example 1

[0095] The difference between it and Example 1 is that:

[0096] (1) Preparation of electrolyte

[0097] A certain amount of lithium difluorooxalatoborate (LiDFOB) is added to 1 ml of tetrahydropyran (THP) and stirred thoroughly to obtain an electrolyte solution, wherein the concentration of lithium salt in the electrolyte solution is 1M.

[0098] Comparative Example 2

[0099] The difference between it and Example 1 is that:

[0100] (1) Preparation of electrolyte

[0101] A certain amount of lithium difluorooxalatoborate (LiDFOB) is added to 1 ml of tetrahydropyran (THP) and stirred thoroughly to obtain an electrolyte solution, wherein the concentration of lithium salt in the electrolyte solution is 0.6M.

[0102] Comparative Example 3

[0103] The difference between it and Example 1 is that:

[0104] (1) Preparation of electrolyte

[0105] A certain amount of lithium difluorooxalatoborate (LiDFOB) was added to 1 ml of tetrahydropyran (THP) and stirred thoroughly to obtain an electrolyte solution, wherein the concentration of lithium salt in the electrolyte solution was 0.28M.

[0106] The compositions of the electrolytes in Examples 1 to 10 and Comparative Examples 1 to 3 are shown in Table 1.

[0107] Table 1

[0108]

[0109] Note: “ / ” means not added.

[0110] Conductivity test: The electrolytes prepared in Examples 1 to 10 and Comparative Examples 1 to 3 were tested using a conductivity meter at room temperature and pressure. The test results are shown in Table 2.

[0111] Battery life test: The batteries prepared in the examples and comparative examples were charged at 25°C at 1 mA / cm 2 Current density, 1 mAh / cm 2 A symmetrical battery test is carried out with a load of , and the time when the battery undergoes a hard short circuit or the polarization potential is greater than 0.3V is the battery life.

[0112] Cycle performance test: The batteries prepared in the examples and comparative examples were charged to 4.2 V at 0.2 C constant current and constant voltage at 25° C., and then discharged to 3.0 V at 0.5 C constant current. This was considered one cycle.

[0113] The test results of battery performance are as follows: Figures 1 to 4 And as shown in Table 2. Figure 1 is a voltage curve diagram of the symmetrical battery prepared in Comparative Example 1, Figure 2 This is a voltage curve diagram of the symmetrical battery prepared in Comparative Example 2. Figure 3 is a voltage curve diagram of the symmetrical battery prepared in Example 1, Figure 4 The cycle performance curves of the fully electric button-type batteries prepared in Example 1 (also known as Example 1), Comparative Example 1 and Comparative Example 2 are shown.

[0114] Table 2

[0115]

[0116] Depend on Figures 1 to 4 As shown in Table 2, compared with Comparative Examples 1 to 3, the life of the symmetrical batteries of Examples 1 to 10 is improved, indicating that adding the additive shown in Formula 1 to the electrolyte is beneficial to improving the life of the battery. From the comparison of Examples 1 to 3, it can be seen that when the mass ratio of the additive in the electrolyte exceeds 3%, increasing the mass ratio of the additive in the electrolyte will reduce the effect of improving the battery life and cycle performance.

[0117] As can be seen from Table 2, the capacity retention rate of the full battery prepared in Examples 1 to 4 is above 90% after 80 cycles, the capacity retention rate of the full battery prepared in Examples 1 and 4 is as high as 94% after 80 cycles, and the number of cycles of Examples 5 and 6 at 80% capacity retention rate is less than 40. By comparing Examples 1, 4 to 6, it can be seen that the effect of the additives in the present application on improving the battery life and cycle performance is greatly affected by the concentration of lithium salt. In the electrolyte system with a lithium salt concentration of less than 0.3M, the additives have a significant effect on improving the battery life and cycle performance. Both additives and low-concentration lithium salts are beneficial to improving the battery life and cycle performance. When the concentration of lithium salt in the electrolyte is about 0.1M and the mass ratio of the additive in the electrolyte is about 1%, the battery life and cycle performance are improved better.

[0118] The technical solutions provided by the embodiments of the present application are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. An electrolyte for a secondary battery, characterized in that: The electrolyte includes an additive, wherein the additive accounts for 0.1wt% to 3wt% of the electrolyte; The electrolyte also includes a lithium salt and a solvent, wherein the concentration of the lithium salt in the electrolyte is 0.1 mol / L to 0.3 mol / L; and the additive is triphenylphosphine.

2. The electrolyte according to claim 1, characterized in that The additive accounts for 0.5 wt % to 2 wt % of the electrolyte.

3. The electrolyte according to claim 2, characterized in that The additive accounts for 1 wt % of the electrolyte.

4. The electrolyte according to claim 1, characterized in that The additive accounts for 2 wt % to 3 wt % of the electrolyte.

5. The electrolyte according to any one of claims 1 to 4, characterized in that The concentration of the lithium salt in the electrolyte is 0.2 mol / L to 0.3 mol / L.

6. The electrolyte according to any one of claims 1 to 4, characterized in that Calculated by mass percentage, the electrolyte includes: 93% to 98% solvent.

7. The electrolyte according to any one of claims 1 to 4, characterized in that The lithium salt is selected from one or more of lithium difluorooxalatoborate, lithium difluorophosphate, lithium nitrate, lithium dioxalatoborate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorophosphate, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl imide) and lithium bis(fluorosulfonyl imide).

8. The electrolyte according to any one of claims 1 to 4, characterized in that The solvent is selected from cyclic ethers and / or esters; or, The solvent is selected from at least one of tetrahydrofuran, 2-methyltetrahydrofuran, 4-methyl-1,3-dioxolane, dioxane, ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate and ethyl propyl carbonate.

9. A secondary battery, characterized in that: The secondary battery comprises a positive electrode sheet, a negative electrode sheet, a separator and the electrolyte according to any one of claims 1 to 8 above.

10. The secondary battery according to claim 9, characterized in that The negative electrode sheet includes lithium metal or lithium alloy.

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