Electrolyte and preparation method thereof, and battery

Abstract

The present application discloses an electrolyte, a preparation method thereof, and a battery. The electrolyte comprises a first lithium salt, a second lithium salt, an additive, a solvent, and a solubilizing agent, wherein the solvent comprises one or more of a cyclic ether and a chain ether having 3 to 10 main chain atoms, and the solubilizing agent comprises one or more of a sulfone solvent and a chain ether having 10 to 15 main chain atoms. The concentration of the second lithium salt in the electrolyte described in the present application can be as high as 2.0 mol / L, which effectively increases the content of the second lithium salt in the electrolyte. In this way, during the operation of the battery, it is beneficial to the formation reaction of the SEI film, and the SEI film can have better performance, such as uniform distribution on the electrode surface, which can effectively inhibit the formation of lithium dendrites, thereby improving the battery's electrical properties such as cycle life and capacity retention.

Description

[0001] This application is a divisional application. The application number of the original application is: 202410626512.2, the application date is May 20, 2024, and the name of the invention is: Electrolyte, preparation method thereof, and battery. Technical Field

[0002] The present application relates to the technical field of electrolytes, and in particular to an electrolyte, a preparation method thereof, and a battery. Background Art

[0003] The electrolyte is the medium used in batteries. It can provide ions for the normal operation of the battery and ensure that the chemical reactions occurring during operation are reversible.

[0004] At present, inorganic film-forming additives such as LiNO3 are usually added to the electrolyte. The reaction of inorganic film-forming additives such as LiNO3 in the battery is used to promote the formation of SEI film, thereby improving the electrical performance of the battery.

[0005] However, the content of inorganic film-forming additives such as LiNO3 in existing electrolytes is low and cannot effectively improve the electrical performance of electrochemical devices. Summary of the Invention

[0006] In view of this, the present application provides an electrolyte, a preparation method thereof, and a battery, aiming to improve the problem of low LiNO3 content in existing electrolytes.

[0007] An embodiment of the present application provides an electrolyte, comprising a first lithium salt, a second lithium salt, an additive, a solvent, and a solubilizer, wherein:

[0008] The solvent includes one or more of a cyclic ether and a chain ether with 3 to 10 main chain atoms;

[0009] The solubilizing agent includes one or more of a sulfone solvent and a chain ether with a main chain atom number of 10 to 15.

[0010] Optionally, in some embodiments, the cyclic ether includes one or more of 1,3-dioxolane, tetrahydrofuran, furan, tetrahydropyran, and 2,2-dimethoxy-4-(trifluoromethyl)-1,3-dioxolane ether.

[0011] Optionally, in some embodiments, the chain ether having 3 to 10 main chain atoms includes one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and diethylene glycol dimethyl ether.

[0012] Optionally, in some embodiments, the sulfone solvent includes one or more of dimethyl sulfoxide, sulfolane, diethyl sulfoxide, tetramethyl sulfoxide, and 3-methylsulfolane.

[0013] Optionally, in some embodiments, the chain ether having a main chain atom number of 10 to 15 includes one or more of diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, and ethylene glycol dipropylene glycol ether.

[0014] Optionally, in some embodiments, the first lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalatoborate, lithium difluorophosphate, lithium hexafluorophosphate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and lithium perchlorate.

[0015] Optionally, in some embodiments, the second lithium salt includes LiNO 3 .

[0016] Optionally, in some embodiments, the additive includes a diluent, and the diluent includes one or more of 1,2,2-trifluoro-1,1,2-trichloroethane, 1,1,1-trifluoro-2-[(2,2,2-trifluoroethoxy)methoxy]ethane, tris(trifluoroethoxy)methane, bis(2,2,2-trifluoroethyl) ether, 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and fluorobenzene.

[0017] Optionally, in some embodiments, the ratio between the amount of the first lithium salt and the volume of the solvent is in the range of (3 mol to 8 mol):1 L.

[0018] Optionally, in some embodiments, the volume ratio of the solvent to the additive is 1:(2~8).

[0019] Optionally, in some embodiments, the ratio between the amount of the second lithium salt and the volume of the solubilizer is (1-22) mol:1L.

[0020] Optionally, in some embodiments, the molar ratio of the first lithium salt to the second lithium salt is 10:(0.2~4.4).

[0021] Optionally, in some embodiments, in the electrolyte, the concentration of the second lithium salt is greater than 0 mol / L and less than or equal to 2.0 mol / L.

[0022] Optionally, in some embodiments, the concentration of the second lithium salt in the electrolyte is 0.5-0.8 mol / L.

[0023] Accordingly, the present application also provides a method for preparing an electrolyte, comprising the following steps:

[0024] dissolving a first lithium salt in a solvent to obtain a first lithium salt solution;

[0025] dissolving the second lithium salt in a solubilizing agent to obtain a second lithium salt solution;

[0026] mixing the first lithium salt solution and the second lithium salt solution to obtain a mixed solution;

[0027] Adding additives to the mixed solution to obtain an electrolyte.

[0028] Optionally, in some embodiments, the solvent includes one or more of a cyclic ether and a chain ether with 3 to 10 main chain atoms.

[0029] Optionally, in some embodiments, the solubilizing agent includes one or more of a sulfone solvent and a chain ether having a main chain atom number of 10 to 15.

[0030] Optionally, in some embodiments, the cyclic ether includes one or more of 1,3-dioxolane, tetrahydrofuran, furan, tetrahydropyran, and 2,2-dimethoxy-4-(trifluoromethyl)-1,3-dioxolane ether.

[0031] Optionally, in some embodiments, the chain ether having 3 to 10 main chain atoms includes one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and diethylene glycol dimethyl ether.

[0032] Optionally, in some embodiments, the sulfone solvent includes one or more of dimethyl sulfoxide, sulfolane, diethyl sulfoxide, tetramethyl sulfoxide, and 3-methylsulfolane.

[0033] Optionally, in some embodiments, the chain ether having a main chain atom number of 10 to 15 includes one or more of diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, and ethylene glycol dipropylene glycol ether.

[0034] Optionally, in some embodiments, the first lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalatoborate, lithium difluorophosphate, lithium hexafluorophosphate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and lithium perchlorate.

[0035] Optionally, in some embodiments, the second lithium salt includes LiNO 3 .

[0036] Optionally, in some embodiments, the additive includes a diluent, and the diluent includes one or more of 1,2,2-trifluoro-1,1,2-trichloroethane, 1,1,1-trifluoro-2-[(2,2,2-trifluoroethoxy)methoxy]ethane, tris(trifluoroethoxy)methane, bis(2,2,2-trifluoroethyl) ether, 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and fluorobenzene.

[0037] Optionally, in some embodiments, the ratio between the amount of the first lithium salt and the volume of the solvent is in the range of (3 mol to 8 mol):1 L.

[0038] Optionally, in some embodiments, the volume ratio of the solvent to the additive is 1:(2~8).

[0039] Optionally, in some embodiments, the ratio between the amount of the second lithium salt and the volume of the solubilizer is (1-22) mol:1L.

[0040] Optionally, in some embodiments, the molar ratio of the first lithium salt to the second lithium salt is 10:(0.2~4.4).

[0041] Correspondingly, the present application also provides a battery comprising the electrolyte.

[0042] The electrolyte described in the present application includes the solubilizer. Under the action of the solubilizer, the concentration of the second lithium salt in the electrolyte can be as high as 2.0 mol / L, which effectively increases the content of the second lithium salt in the electrolyte. In this way, during the operation of the battery, it is beneficial to the formation reaction of the SEI film, and the SEI film can have better performance, such as uniform distribution on the electrode surface, which can effectively inhibit the formation of lithium dendrites, thereby improving the battery's electrical properties such as cycle life and capacity retention rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. 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 creative work.

[0044] Figure 1 This is a flow chart of a method for preparing an electrolyte provided in an embodiment of the present application;

[0045] Figures 2 to 22These are time-voltage curves of button batteries prepared from the electrolytes of Examples 1 to 21 of the present application;

[0046] Figures 23 to 36 These are time-voltage curves of button batteries prepared from the electrolytes of Comparative Examples 1 to 14 of the present application;

[0047] Figures 37 to 57 These are respectively the time-voltage curves of the soft-pack batteries prepared from the electrolytes of Examples 1 to 21 of the present application;

[0048] Figures 58 to 69 They are respectively the time-voltage curves of the soft-pack batteries prepared from the electrolytes of Comparative Examples 1 to 8, 10 to 11, and 13 to 14 of the present application. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of this application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0050] In this application, unless otherwise indicated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of a device in actual use or operation, specifically in the drawing directions of the accompanying drawings; whereas "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "including" means "including but not limited to." Terms such as first, second, and third are used merely as labels and do not impose numerical requirements or establish a sequence.

[0051] In this application, "and / or" describes the association relationship between associated objects, indicating that three relationships can exist. 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.

[0052] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single 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, and c can each be single or plural.

[0053] 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 hard 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 numbers within the range. For example, the description of a range 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 applies 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.

[0054] The solvents in the electrolytes used in existing electrochemical devices, such as lithium metal batteries, primarily include carbonate solvents. Inorganic film-forming additives in the electrolyte, such as LiNO3, decompose into substances that contribute to the formation of the SEI film, thereby improving the battery's lifespan, cycle performance, and other electrical properties. However, the solubility of inorganic film-forming additives in existing electrolytes is low and needs to be further improved.

[0055] The technical solution of this application is as follows:

[0056] In a first aspect, an embodiment of the present application provides an electrolyte comprising a first lithium salt, a second lithium salt, an additive, a solvent, and a solubilizer.

[0057] The first lithium salt includes but is not limited to one or more of LiFSI (lithium bis(fluorosulfonyl imide), LiTFSI (lithium bis(trifluoromethanesulfonyl imide), LiDFOB (lithium difluorooxalatoborate), LiOP2F2 (lithium difluorophosphate), LiPF6 (lithium hexafluorophosphate), LiBOB (lithium dioxalatoborate), LiDODFP (lithium difluorooxalatophosphate), LiBF4 (lithium tetrafluoroborate), LiTf (lithium trifluoromethanesulfonate), and LiClO4 (lithium perchlorate).

[0058] The second lithium salt includes, but is not limited to, LiNO3. The second lithium salt is an inorganic film-forming additive in the electrolyte. It can provide lithium ions, enhance the electrolyte's ionic conductivity, help reduce the internal resistance of the lithium battery, and improve the electrolyte's conductivity and the diffusion rate of lithium ions, thereby increasing the energy density of the battery containing the electrolyte. During battery operation, the second lithium salt can also participate in the formation reaction of the SEI film, inhibiting the decomposition side reaction of the electrolyte, thereby improving the electrolyte's stability and enhancing the battery's electrical properties, such as cycle life and capacity retention.

[0059] The additives include, but are not limited to, diluents, including, but not limited to, one or more of 1,2,2-trifluoro-1,1,2-trichloroethane, 1,1,1-trifluoro-2-[(2,2,2-trifluoroethoxy)methoxy]ethane, tris(trifluoroethoxy)methane, bis(2,2,2-trifluoroethyl) ether, 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether (HFE), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and fluorobenzene. The diluents can dilute the electrolyte, reduce the viscosity of the electrolyte, reduce the impedance, increase the conductivity of the electrolyte, and increase the coulombic efficiency of a battery including the electrolyte.

[0060] The solvent includes, but is not limited to, one or more of cyclic ethers and chain ethers with 3 to 10 main chain atoms.

[0061] In some embodiments, the cyclic ether includes but is not limited to one or more of 1,3-dioxolane, tetrahydrofuran, furan, tetrahydropyran, and 2,2-dimethoxy-4-(trifluoromethyl)-1,3-dioxolane.

[0062] In some embodiments, the chain ether having 3 to 10 main chain atoms includes, but is not limited to, one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and diethylene glycol dimethyl ether.

[0063] The solubilizing agent includes, but is not limited to, one or more of sulfone solvents and chain ethers with a main chain atom number of 10 to 15.

[0064] In some embodiments, the sulfone solvent includes but is not limited to one or more of dimethyl sulfoxide (DMSO), sulfolane, diethyl sulfoxide, tetramethyl sulfoxide, and 3-methylsulfolane.

[0065] In some embodiments, the chain ether having 10 to 15 main chain atoms includes, but is not limited to, one or more of diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, and ethylene glycol dipropylene glycol ether.

[0066] The solubilizer has a high dielectric constant, which can reduce the cation-anion coordination interaction of the lithium salt, effectively improve the solubility of the second lithium salt in the electrolyte, and thus effectively increase the content of the second lithium salt in the electrolyte.

[0067] In some embodiments, the ratio of the amount of the first lithium salt to the volume of the solvent is (3 mol to 8 mol):1 L, for example, 3 mol:1 L, 3.5 mol:1 L, 4 mol:1 L, 4.5 mol:1 L, 5 mol:1 L, 5.5 mol:1 L, 6 mol:1 L, 6.5 mol:1 L, 7 mol:1 L, 7.5 mol:1 L, 8 mol:1 L, etc. Within this ratio range, the first lithium salt can be fully dissolved, the electrolyte viscosity can be moderate, and the electrolyte can have good ion mobility and stability, thereby enabling a battery using the electrolyte to have good electrical properties such as cycle life and capacity retention.

[0068] In some embodiments, the volume ratio of the solvent to the additive is 1:(2-8), for example, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, etc. Within this ratio range, the electrolyte has an appropriate viscosity, high conductivity, and high stability.

[0069] In some embodiments, the ratio of the amount of the second lithium salt to the volume of the solubilizer is (1-22) mol:1L, for example, 1 mol:1L, 2 mol:1L, 3 mol:1L, 4 mol:1L, 5 mol:1L, 6 mol:1L, 7 mol:1L, 8 mol:1L, 10 mol:1L, 11 mol:1L, 12 mol:1L, 15 mol:1L, 18 mol:1L, 20 mol:1L, 22 mol:1L, etc. Within this ratio range, the second lithium salt is fully dissolved, the electrolyte has an appropriate viscosity, and has high conductivity and stability.

[0070] In some embodiments, in the electrolyte, the molar ratio of the first lithium salt to the second lithium salt is 10:(0.2-4.4), for example, 10:0.2, 10:0.5, 10:1, 10:1.2, 10:1.5, 10:2, 10:2.5, 10:3, 10:4, 10:4.4, etc. Within this range, a battery including the electrolyte can have higher coulombic efficiency, cycle life, and higher capacity retention.

[0071] In some embodiments, in the electrolyte, the concentration of the second lithium salt is greater than 0 mol / L and less than or equal to 2.0 mol / L, for example, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 1.0 mol / L, 2.0 mol / L, etc. In some preferred embodiments, the concentration of the second lithium salt ranges from 0.5 to 0.8 mol / L.

[0072] It should be noted that, in the present application, the concentration of the second lithium salt is based on the sum of the volumes of the solvent and the solubilizer, that is, the concentration of the second lithium salt = the amount of the second lithium salt / (volume of the solvent + volume of the solubilizer).

[0073] The electrolyte described in the present application includes the solubilizer. Under the action of the solubilizer, the concentration of the second lithium salt in the electrolyte can be as high as 2.0 mol / L, which effectively increases the content of the second lithium salt in the electrolyte. In this way, during the operation of the battery, it is beneficial to the formation reaction of the SEI film, and the SEI film can have better performance, such as uniform distribution on the electrode surface, which can effectively inhibit the formation of lithium dendrites, thereby improving the battery's electrical properties such as cycle life and capacity retention rate.

[0074] Furthermore, the electrolyte described in the present application has good stability and a higher content of the second lithium salt due to the synergistic effect of the types and specific ratios of its components, so that the battery containing the electrolyte has a lower overpotential, thereby giving the battery a longer life and a higher capacity retention rate.

[0075] Second, see Figure 1 The present invention also provides a method for preparing an electrolyte, comprising the following steps:

[0076] Step S11, dissolving a first lithium salt in a solvent to obtain a first lithium salt solution;

[0077] Step S12, dissolving the second lithium salt in a solubilizing agent to obtain a second lithium salt solution;

[0078] Step S13, mixing the first lithium salt solution and the second lithium salt solution to obtain a mixed solution;

[0079] Step S14: adding additives to the mixed solution to obtain an electrolyte.

[0080] The types of the first lithium salt, solvent, second lithium salt, solubilizer, and additive are as described above and will not be repeated here.

[0081] In some embodiments, the ratio of the amount of the first lithium salt to the volume of the solvent is in the range of (3 mol to 8 mol):1 L, for example, 3 mol:1 L, 3.5 mol:1 L, 4 mol:1 L, 4.5 mol:1 L, 5 mol:1 L, 5.5 mol:1 L, 6 mol:1 L, 6.5 mol:1 L, 7 mol:1 L, 7.5 mol:1 L, 8 mol:1 L, etc. Within this ratio range, the first lithium salt can be fully dissolved, the viscosity of the electrolyte can be moderate, and the electrolyte can have good ion mobility and stability, thereby enabling a battery using the electrolyte to have good electrical properties such as cycle life and capacity retention.

[0082] In some embodiments, the ratio of the amount of the second lithium salt to the volume of the solubilizer is (1-22) mol:1L, for example, 1 mol:1L, 2 mol:1L, 3 mol:1L, 4 mol:1L, 5 mol:1L, 6 mol:1L, 7 mol:1L, 8 mol:1L, 10 mol:1L, 11 mol:1L, 12 mol:1L, 15 mol:1L, 18 mol:1L, 20 mol:1L, 22 mol:1L, etc. Within this ratio range, the second lithium salt can be fully dissolved, which is beneficial to increasing the content of the second lithium salt in the electrolyte, thereby facilitating improving the electrical properties of the battery including the electrolyte, such as the lifespan and capacity retention rate.

[0083] In some embodiments, the molar ratio of the solvent to the additive is 1:(2-8), for example, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, etc. Within this ratio range, the electrolyte has an appropriate viscosity, high conductivity, and high stability.

[0084] In some embodiments, in the electrolyte, the molar ratio of the first lithium salt to the second lithium salt is 10:(0.2-4.4), for example, 10:0.2, 10:0.5, 10:1, 10:1.2, 10:1.5, 10:2, 10:2.5, 10:3, 10:4, 10:4.4, etc. Within this range, a battery including the electrolyte can have higher coulombic efficiency, cycle life, and higher capacity retention.

[0085] The preparation method of the electrolyte described in the present application first dissolves the second lithium salt in a solubilizer to obtain a second lithium salt solution, and then mixes the second lithium salt solution with the first lithium salt solution. In this way, the content of the second lithium salt (inorganic film-forming additive) in the prepared electrolyte can be effectively increased. The concentration of the second lithium salt in the electrolyte can be as high as 2.0 mol / L, thereby effectively promoting the formation of the SEI film in the battery including the electrolyte, improving the uniformity of the SEI film on the electrode surface, and effectively inhibiting the formation of lithium dendrites, thereby improving the battery's cycle life and capacity retention rate and other performance.

[0086] Furthermore, the preparation method of the electrolyte described in the present application, through the synergistic effect of the specific ratios of the components, makes the prepared electrolyte have good stability and a higher content of the second lithium salt, so that the battery containing the electrolyte has a lower overpotential, thereby making the battery have a longer life and a higher capacity retention rate.

[0087] In a third aspect, an embodiment of the present application further provides a battery, comprising a positive electrode, a negative electrode, a separator, and the electrolyte described above.

[0088] In some embodiments, the battery is a lithium-ion battery.

[0089] The battery described in the present application includes the electrolyte described above. The content of the second lithium salt in the electrolyte is relatively high. During the operation of the battery, it can effectively promote the formation of the SEI film in the battery, improve the uniformity of the SEI film on the electrode surface, and thus effectively inhibit the formation of lithium dendrites, thereby improving the battery's cycle life and capacity retention rate and other performance.

[0090] Furthermore, the preparation method of the electrolyte described in the present application, through the synergistic effect of the types and specific ratios of the components, makes the prepared electrolyte have good stability and a higher content of the second lithium salt, thereby making the battery have a lower overpotential, and thus the battery has a longer cycle life and a higher capacity retention rate.

[0091] The present invention is described in detail below by means of specific examples, which are only some examples of the present invention and are not intended to limit the present invention. The raw materials used in the following examples, unless otherwise specified, are all commercially available products.

[0092] Example 1

[0093] The electrolyte of this embodiment includes a first lithium salt LiFSI, a solvent ethylene glycol dimethyl ether, a diluent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, a second lithium salt LiNO3, and a solubilizer triethylene glycol dimethyl ether.

[0094] In this embodiment, the ratio between the amount of the first lithium salt and the volume of the solvent is 5 mol:1L, the molar ratio of the first lithium salt to the second lithium salt is 10:1.1, the ratio between the amount of the second lithium salt and the volume of the solubilizer is 5.5 mol:1L, the volume ratio of the solvent to the diluent is 1:4, and the concentration of the second lithium salt is 0.50 mol / L.

[0095] Example 2

[0096] The electrolyte of this embodiment includes a first lithium salt LiFSI, a solvent ethylene glycol dimethyl ether, a diluent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, a second lithium salt LiNO3, and a solubilizer triethylene glycol dimethyl ether.

[0097] In this embodiment, the ratio between the amount of the first lithium salt and the volume of the solvent is 5 mol:1L, the molar ratio of the first lithium salt to the second lithium salt is 10:1.1, the ratio between the amount of the second lithium salt and the volume of the solubilizer is 5.5 mol:1L, the volume ratio of the solvent to the diluent is 1:6, and the concentration of the second lithium salt is 0.50 mol / L.

[0098] This embodiment is substantially the same as embodiment 1, except that the volume ratio of the solvent to the diluent in this embodiment is 1:6.

[0099] Example 3

[0100] The electrolyte of this embodiment includes a first lithium salt LiFSI, a solvent ethylene glycol dimethyl ether, a diluent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, a second lithium salt LiNO3, and a solubilizer triethylene glycol dimethyl ether.

[0101] In this embodiment, the ratio between the amount of the first lithium salt and the volume of the solvent is 5 mol:1 L, the volume ratio of the solvent to the diluent is 1:4, and the concentration of the second lithium salt is 0.60 mol / L.

[0102] This embodiment is basically the same as Example 1, except that, in this embodiment, the concentration of the second lithium salt is 0.60 mol / L, the molar ratio of the first lithium salt to the second lithium salt is 10:1.32, and the ratio between the amount of the second lithium salt and the volume of the solubilizer is 6.6 mol:1L.

[0103] Example 4

[0104] The electrolyte of this embodiment includes a first lithium salt LiFSI, a solvent ethylene glycol dimethyl ether, a diluent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, a second lithium salt LiNO3, and a solubilizer DMSO.

[0105] In this embodiment, the ratio between the amount of the first lithium salt and the volume of the solvent is 5 mol:1L, the molar ratio of the first lithium salt to the second lithium salt is 10:1.1, the ratio between the amount of the second lithium salt and the volume of the solubilizer is 5.5 mol:1L, the volume ratio of the solvent to the diluent is 1:4, and the concentration of the second lithium salt is 0.50 mol / L.

[0106] This embodiment is basically the same as embodiment 1, except that the solubilizing agent in this embodiment is DMSO.

[0107] Example 5

[0108] The electrolyte of this embodiment includes a first lithium salt LiFSI, a solvent ethylene glycol dimethyl ether, a diluent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, a second lithium salt LiNO3, and a solubilizer DMSO.

[0109] In this embodiment, the ratio between the amount of the first lithium salt and the volume of the solvent is 5 mol:1 L, the volume ratio of the solvent to the diluent is 1:4, and the concentration of the second lithium salt is 0.60 mol / L.

[0110] This embodiment is basically the same as Example 4, except that, in this embodiment, the concentration of the second lithium salt is 0.60 mol / L, the molar ratio of the first lithium salt to the second lithium salt is 10:1.32, and the ratio between the amount of the second lithium salt and the volume of the solubilizer is 6.6 mol:1L.

[0111] Example 6

[0112] The electrolyte of this embodiment includes first lithium salts LiFSI and LiBOB, solvent ethylene glycol dimethyl ether, diluent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, second lithium salt LiNO3, and solubilizer triethylene glycol dimethyl ether.

[0113] In this embodiment, the ratio between the amount of the first lithium salt and the volume of the solvent is 5 mol:1L, the molar ratio of LiFSI and LiBOB is 3:2, the molar ratio of the first lithium salt to the second lithium salt is 10:1.1, the ratio between the amount of the second lithium salt and the volume of the solubilizer is 5.5 mol:1L, the volume ratio of the solvent to the diluent is 1:4, and the concentration of the second lithium salt is 0.50 mol / L.

[0114] This embodiment is substantially the same as embodiment 1, except that, in this embodiment, the first lithium salt includes LiFSI and LiBOB, and the molar ratio of LiFSI to LiBOB is 3:2.

[0115] Example 7

[0116] The electrolyte of this embodiment includes first lithium salts LiFSI and LiTFSI, solvent ethylene glycol dimethyl ether, diluent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, second lithium salt LiNO3, and solubilizer triethylene glycol dimethyl ether.

[0117] In this embodiment, the ratio between the amount of the first lithium salt and the volume of the solvent is 5 mol: 1L, the molar ratio of LiFSI and LiTFSI is 3: 2, the molar ratio of the first lithium salt to the second lithium salt is 10: 1.1, the ratio between the amount of the second lithium salt and the volume of the solubilizer is 5.5 mol: 1L, the volume ratio of the solvent to the diluent is 1: 4, and the concentration of the second lithium salt is 0.50 mol / L.

[0118] This embodiment is substantially the same as Example 1, except that, in this embodiment, the first lithium salt includes LiFSI and LiTFSI, and the molar ratio of LiFSI to LiTFSI is 3:2.

[0119] Example 8

[0120] This embodiment is substantially the same as embodiment 1, except that the solubilizing agent in this embodiment is 3-methylsulfolane.

[0121] Example 9

[0122] This embodiment is basically the same as Example 1, except that the solubilizing agent in this embodiment is ethylene glycol dipropionitrile ether.

[0123] Example 10

[0124] This embodiment is substantially the same as embodiment 1, except that the solvent in this embodiment is 1,3-dioxolane.

[0125] Example 11

[0126] This embodiment is substantially the same as embodiment 1, except that the diluent in this embodiment is 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether.

[0127] Example 12

[0128] This embodiment is basically the same as Example 1, except that, in this embodiment, the molar ratio of the second lithium salt to the volume ratio of the solubilizer is 3.3 mol:1 L, the molar ratio of the first lithium salt to the second lithium salt is 10:1.1, and the concentration of the second lithium salt is 0.30 mol / L.

[0129] Example 13

[0130] This embodiment is basically the same as Example 1, except that the molar ratio of the second lithium salt to the volume ratio of the solubilizer in this example is 6.6 mol:1L, the molar ratio of the first lithium salt to the second lithium salt is 10:1.1, and the concentration of the second lithium salt is 0.60 mol / L.

[0131] Example 14

[0132] This embodiment is basically the same as Example 1, except that, in this embodiment, the molar ratio of the second lithium salt to the volume ratio of the solubilizer is 8.8 mol:1 L, the molar ratio of the first lithium salt to the second lithium salt is 10:1.1, and the concentration of the second lithium salt is 0.80 mol / L.

[0133] Example 15

[0134] This embodiment is substantially the same as embodiment 1, except that the volume ratio of the solvent to the diluent in this embodiment is 1:8.

[0135] Example 16

[0136] This embodiment is basically the same as Example 1, except that, in this embodiment, the molar ratio of the first lithium salt to the second lithium salt is 10:0.2, the ratio between the amount of the second lithium salt and the volume of the solubilizer is 1 mol:1 L, and the concentration of the second lithium salt is 0.09 mol / L.

[0137] Example 17

[0138] This embodiment is basically the same as Example 1, except that, in this embodiment, the molar ratio of the first lithium salt to the second lithium salt is 10:4.4, the ratio between the amount of the second lithium salt and the volume of the solubilizer is 22 mol:1 L, and the concentration of the second lithium salt is 2.0 mol / L.

[0139] Example 18

[0140] This embodiment is basically the same as Example 1, except that, in this embodiment, the concentration of the second lithium salt is 0.8 mol / L, the molar ratio of the first lithium salt to the second lithium salt is 10:1.76, and the ratio between the amount of the second lithium salt and the volume of the solubilizer is 8.8 mol:1L.

[0141] Example 19

[0142] This embodiment is basically the same as Example 1, except that, in this embodiment, the concentration of the second lithium salt is 0.7 mol / L, the molar ratio of the first lithium salt to the second lithium salt is 10:1.54, and the ratio between the amount of the second lithium salt and the volume of the solubilizer is 7.7 mol:1L.

[0143] Example 20

[0144] This embodiment is substantially the same as embodiment 1, except that, in this embodiment, the ratio between the amount of the first lithium salt and the volume of the solvent is 6 mol:1 L, and the molar ratio of the first lithium salt to the second lithium salt is 12:1.1.

[0145] Example 21

[0146] This embodiment is substantially the same as embodiment 1, except that, in this embodiment, the ratio between the amount of the first lithium salt and the volume of the solvent is 8 mol:1 L, and the molar ratio of the first lithium salt to the second lithium salt is 16:1.1.

[0147] Comparative Example 1

[0148] This comparative example is basically the same as Example 1, except that the electrolyte in this comparative example does not include a solubilizer, the concentration of the second lithium salt in the electrolyte is 0.55 mol / L, and the molar ratio of the first lithium salt to the second lithium salt is 10:1.1.

[0149] Comparative Example 2

[0150] This comparative example is basically the same as Example 2, except that the electrolyte in this comparative example does not include a solubilizer, the concentration of the second lithium salt in the electrolyte is 0.55 mol / L, and the molar ratio of the first lithium salt to the second lithium salt is 10:1.1.

[0151] Comparative Example 3

[0152] This comparative example is substantially the same as Example 5, except that the electrolyte of this comparative example does not include a solubilizer, the concentration of the second lithium salt in the electrolyte is 0.66 mol / L, and the molar ratio of the first lithium salt to the second lithium salt is 10:1.32.

[0153] Comparative Example 4

[0154] This comparative example is substantially the same as Example 1, except that the ratio of the amount of the second lithium salt to the volume of the solubilizer in the electrolyte of this comparative example is 0.5 mol:1 L, and the concentration of the second lithium salt is 0.05 mol / L.

[0155] Comparative Example 5

[0156] This comparative example is substantially the same as Example 1, except that the ratio of the amount of the second lithium salt to the volume of the solubilizer in the electrolyte of this comparative example is 25 mol:1 L, and the concentration of the second lithium salt is 2.27 mol / L.

[0157] Comparative Example 6

[0158] This comparative example is substantially the same as Example 1, except that the volume ratio of the solvent to the diluent in the electrolyte of this comparative example is 1:1.5.

[0159] Comparative Example 7

[0160] This comparative example is substantially the same as Example 1, except that the volume ratio of the solvent to the diluent in the electrolyte of this comparative example is 1:8.5.

[0161] Comparative Example 8

[0162] This comparative example is basically the same as Example 1, except that the molar ratio of the first lithium salt to the second lithium salt in the electrolyte of this comparative example is 10:0.5, the ratio between the amount of the second lithium salt and the volume of the solubilizer is 2.5 mol:1 L, and the concentration of the second lithium salt is 0.23 mol / L.

[0163] Comparative Example 9

[0164] This comparative example is basically the same as Example 1, except that the molar ratio of the first lithium salt to the second lithium salt in the electrolyte of this comparative example is 10:8, the ratio between the amount of the second lithium salt and the volume of the solubilizer is 40 mol:1 L, and the concentration of the second lithium salt is 3.64 mol / L.

[0165] Comparative Example 10

[0166] This comparative example is basically the same as Example 1, except that the ratio between the amount of the first lithium salt and the volume of the solvent in the electrolyte of this comparative example is 2 mol:1 L, and the molar ratio of the first lithium salt to the second lithium salt is 10:2.75.

[0167] Comparative Example 11

[0168] This comparative example is basically the same as Example 1, except that the ratio between the amount of the first lithium salt and the volume of the solvent in the electrolyte of this comparative example is 11 mol:1 L, and the molar ratio of the first lithium salt to the second lithium salt is 11:0.55.

[0169] Comparative Example 12

[0170] This comparative example is substantially the same as Example 1, except that the solvent in the electrolyte of this comparative example is triethyl phosphate.

[0171] Comparative Example 13

[0172] This comparative example is substantially the same as Example 1, except that the solvent in the electrolyte of this comparative example is diethyl carbonate.

[0173] Comparative Example 14

[0174] This comparative example is basically the same as Example 1, except that the solvent in the electrolyte of this comparative example is methyl propionate.

[0175] In Examples 1-21 and Comparative Examples 1-14, the composition of the electrolyte is shown in Table 1.

[0176] Table 1:

[0177]

[0178] The electrolytes of Examples 1 to 21 and Comparative Examples 1 to 14 were observed to see whether they were completely dissolved and whether there was precipitation. The results are recorded in Table 2.

[0179] Li / Li symmetrical cells and NCM811 / Li pouch cells were assembled using the electrolytes of Examples 1-21 and Comparative Examples 1-14, respectively. The cycle life of the symmetrical cells, the initial impedance of the pouch cells, and the capacity retention of the pouch cells after 83 cycles at 0.2C / 0.5C were tested. The test results are shown in Table 2.

[0180] The electrolytes of Examples 1 to 21 and Comparative Examples 1 to 14 were respectively used to assemble button cells (positive and negative electrodes were both metal lithium sheets, current collectors were copper foil, ceramic separators, CR2032 button cells, electrolyte dosage was 20 μL, and the button cells were symmetrical cells). The performance of the button cells was tested and the results were as follows: Figures 2 to 36 The time-voltage curve of the button battery is shown.

[0181] Depend on Figures 2 to 36 It can be seen that:

[0182] The button battery prepared with the electrolyte of Example 1 can work stably for 340 hours;

[0183] The volume ratio of the solvent to the diluent in the electrolyte of Example 2 is 1:6. Compared with the button battery prepared with the electrolyte of Example 1, the cycle life of the button battery prepared with the electrolyte of Example 2 is slightly reduced.

[0184] In Example 3, the concentration of the second lithium salt was increased to 0.6 mol / L. Compared with the button battery prepared with the electrolyte of Example 1, the cycle life of the button battery prepared with the electrolyte of Example 3 was slightly reduced.

[0185] The voltage fluctuation of the button cells prepared with the electrolytes of Examples 4 and 5 was large, indicating that the compatibility of dimethyl sulfoxide with the lithium metal negative electrode was weaker than that of diethylene glycol dimethyl ether;

[0186] The first lithium salt in the electrolytes of Examples 6 and 7 is two kinds, and the cycle life of the button-type battery prepared with the electrolyte of Example 3 is increased, indicating that the lithium salt additive also plays a role in negative electrode film formation and improving the cycle life;

[0187] The solubilizing agent was replaced in the electrolytes of Examples 8 to 9. The cycle life of the batteries prepared with the electrolytes of Examples 6 to 9 was slightly shorter than that of the batteries prepared with the electrolyte of Example 1.

[0188] The solvent was replaced in the electrolytes of Examples 10-11. The cycle life of the batteries prepared from the electrolytes of Examples 10-11 was slightly shorter than that of the batteries prepared from the electrolyte of Example 1, indicating that the solvent DME has better adaptability to lithium metal.

[0189] The dissolution rates of the lithium salts in the electrolytes of Examples 12 to 14 varied. In Example 12, the molar ratio of the second lithium salt to the solubilizer was 3.3 mol:1 L, resulting in a low lithium salt concentration and rapid dissolution. However, the lithium salt's role in negative electrode film formation was also weakened, and its ability to inhibit lithium dendrites was also weakened, resulting in a reduced battery cycle life. In Example 14, the molar ratio of the second lithium salt to the solubilizer was 8.8 mol:1 L, resulting in a very slow dissolution rate, approaching saturation. This also reduced the cycle life of the button battery.

[0190] In the electrolyte of Example 15, the volume ratio of solvent to diluent is 1:8, and the electrolyte concentration is low and the viscosity is low. However, the large diluent-anion binding energy affects the stability of the lithium ion solvation structure and destroys the stability of the electrolyte at the high-voltage positive electrode, resulting in a reduced cycle life.

[0191] In the electrolytes of Examples 16 and 17, the molar ratio of the second lithium salt to the first lithium salt is at the minimum and maximum values, respectively. The corresponding button battery cycle life is significantly reduced, but remains above 250 h, indicating that the second lithium salt can effectively inhibit the formation of lithium dendrites within this concentration range.

[0192] The second lithium salt concentration in the electrolyte of Examples 18-19 is at the upper limit, and the corresponding button battery cycle life is slightly reduced;

[0193] The first lithium salt concentrations in the electrolytes of Examples 20 and 21 are median and maximum values, respectively. The button battery prepared with the electrolyte of Example 20 has a cycle life greater than that of the button battery prepared with the electrolyte of Example 21, and its solubility is also better than that of Example 21, indicating that the lithium salt can be dissolved within this range, and the cycle performance of the button battery can be maintained for more than 220 hours.

[0194] The electrolytes of Comparative Examples 1 to 3 do not contain a solubilizing agent, the solubility of the second lithium salt is reduced, the concentration of the second lithium salt in the electrolyte is reduced, and the corresponding button battery cycle life is significantly reduced;

[0195] In Comparative Example 4, the second lithium salt concentration in the electrolyte is low and the solubilizer is excessive, which affects the solvation structure and reduces the cycle performance of the corresponding button battery.

[0196] The concentration of the second lithium salt in the electrolyte of Comparative Example 5 was greater than the designed range, resulting in incomplete dissolution and a decrease in the performance of the corresponding button battery.

[0197] The electrolyte of Comparative Example 6 has too little diluent content, resulting in a high viscosity of the electrolyte and a high lithium ion transfer impedance, which reduces the cycle life of the corresponding button battery.

[0198] The electrolyte of Comparative Example 7 contains an excessive amount of diluent, which destroys the solubility structure between lithium ions and solvent molecules, reduces the stability of the electrolyte, and reduces the cycle life of the corresponding button battery;

[0199] In Comparative Example 8, the electrolyte of the second lithium salt is too little, the negative electrode protection effect is poor, the dendrites grow quickly, and the corresponding button battery cycle life is reduced;

[0200] In Comparative Example 9, the electrolyte contained too much second lithium salt, which could not be completely dissolved by the solubilizer, resulting in an unstable electrolyte and faster dendrite growth in the corresponding button cell.

[0201] The concentration of the first lithium salt in the electrolyte of Comparative Example 10 is too low and does not fall within the range of high-concentration salt. Excessive solvent has a stronger corrosive effect on lithium metal, and the corresponding button battery cycle life is shortened.

[0202] In Comparative Example 11, the amount of the first lithium salt in the electrolyte is too high, and the solvent cannot completely dissolve the first lithium salt. The precipitated crystals will accelerate the growth of lithium dendrites, pierce the diaphragm, and cause a short circuit. The corresponding button battery cycle life is reduced.

[0203] In Comparative Examples 12 to 14, the electrolyte solvents were replaced with phosphate ester, carbonate ester, and carboxylate ester. Compared with ether solvents, the cycle life of the corresponding button batteries decreased, indicating that ester solvents are less compatible with lithium metal negative electrodes than ether solvents.

[0204] The NCM811 / Li soft-pack batteries assembled with the electrolytes of Examples 1 to 21 and Comparative Examples 1 to 8, 10 to 14 were tested for electrical performance. Figures 39 to 69 The time-capacity retention curve is shown.

[0205] Depend on Figures 37 to 69 It can be seen that:

[0206] The soft-pack battery prepared with the electrolyte of Example 1 has a capacity retention rate of 95.4% after 83 weeks, and its cycle life is expected to reach 200 weeks.

[0207] The volume ratio of the solvent to the diluent in the electrolyte of Example 2 is 1:6. The cycle life of the battery cell prepared with the electrolyte of Example 2 is slightly shorter than that of the battery cell prepared with the electrolyte of Example 1.

[0208] The concentration of the second lithium salt in the electrolyte of Example 3 was increased to 0.6 mol / L. The cycle life of the battery cell prepared with the electrolyte of Example 3 was slightly reduced compared with the battery cell prepared with the electrolyte of Example 1.

[0209] The capacity decay slope of the battery cells prepared with the electrolytes of Examples 4 and 5 is relatively large, indicating that the compatibility of dimethyl sulfoxide with the lithium metal negative electrode is weaker than that of diethylene glycol dimethyl ether;

[0210] In Examples 6 and 7, the electrolytes used two types of first lithium salts, and the cell cycle curves had gentle slopes and significantly increased cycle life, indicating that the lithium salt additives also played a role in negative electrode film formation and improved cycle life.

[0211] In Examples 8 and 9, the solubilizing agent was replaced in the electrolyte, and the cycle life of the corresponding battery cells was slightly shorter than that of Example 1.

[0212] When the solvent was replaced in the electrolyte of Examples 10-11, the cycle life of the corresponding battery cells was slightly shorter than that of Example 1, indicating that the solvent DME has better adaptability to lithium metal;

[0213] The dissolution rates of the lithium salts in the electrolytes of Examples 12-14 vary. In Example 12, the molar ratio of the second lithium salt to the solubilizer is 3.3 mol:1L by volume. The lithium salt concentration is low and the dissolution is rapid, but the role of participating in the negative electrode film formation is also weakened, and the role of inhibiting lithium dendrites is weakened, showing a steeper cycle curve and a shorter cycle life. In Example 14, the molar ratio of the second lithium salt to the solubilizer is 8.8 mol:1L by volume. When the dissolution rate is very slow and almost reaches saturation, the cycle life of the battery cell is also shortened.

[0214] In the electrolyte of Example 15, the volume ratio of solvent to diluent is 1:8, the electrolyte concentration is low, and the viscosity is low. However, the large diluent-anion binding energy affects the stability of the lithium ion solvation structure and destroys the stability of the electrolyte at the high-voltage positive electrode, resulting in a reduced cycle life.

[0215] The molar ratio of the second lithium salt to the first lithium salt in the electrolytes of Examples 16 and 17 is at the minimum and maximum values, respectively, and the corresponding battery cell cycle life is significantly reduced, but remains above 80%, indicating that the second lithium salt can effectively inhibit the formation of lithium dendrites within this concentration range;

[0216] The second lithium salt concentration in the electrolyte of Examples 18-19 is at the upper limit, and the corresponding battery cell cycle life is slightly reduced;

[0217] The first lithium salt concentrations in the electrolytes of Examples 20 and 21 are the median and maximum values, respectively. The battery cell cycle life corresponding to Example 20 is greater than that of Example 21, and the solubility is also better than that of Example 21, indicating that the lithium salt can be dissolved within this range, and the battery cell cycle performance can be maintained above 80%.

[0218] The electrolytes of Comparative Examples 1 to 3 do not contain a solubilizer, the lithium salt cannot be completely dissolved, the electrolyte is unstable, and the corresponding battery cell cycle life is significantly reduced;

[0219] In the electrolyte of Comparative Example 4, the concentration of the second lithium salt is low and the solubilizer is excessive, which affects the solvation structure, causes the battery cell to drop in water, and the corresponding battery cell has poor cycle performance;

[0220] In Comparative Example 5, the concentration of the second lithium salt in the electrolyte was greater than the designed range, the solubilizer was not completely dissolved, and the corresponding battery cell cycle performance decreased;

[0221] The electrolyte of Comparative Example 6 has too little diluent content, resulting in a high viscosity of the electrolyte and a high lithium ion transfer impedance, which reduces the cycle life of the corresponding battery cell.

[0222] The electrolyte of Comparative Example 7 contains an excessive amount of diluent, which destroys the solubilization structure between lithium ions and solvent molecules, reduces the stability of the electrolyte, and reduces the cycle life of the corresponding battery cell;

[0223] In Comparative Example 8, the electrolyte solution contained too little second lithium salt, resulting in poor negative electrode protection, rapid dendrite growth, and a short circuit in the battery cell. This caused a drop in battery life, which reduced the cycle life of the corresponding battery cell.

[0224] In Comparative Example 9, the electrolyte contained too much second lithium salt, which could not be completely dissolved by the solubilizer. After mixing, the second lithium salt precipitated, and the electrolyte was unstable, so no soft-pack battery was produced.

[0225] The concentration of the first lithium salt in the electrolyte of Comparative Example 10 is too low and does not fall within the range of high-concentration salts. Excessive solvents have a stronger corrosive effect on lithium metal, and the corresponding battery cell cycle life is shortened.

[0226] In the electrolyte of Comparative Example 11, the concentration of the first lithium salt is too high, the solvent cannot completely dissolve the lithium salt, and the precipitated crystals will accelerate the growth of lithium dendrites, pierce the diaphragm, cause a short circuit, and reduce the cycle life of the corresponding battery cell;

[0227] In the comparative examples 12 to 14, the electrolyte solvents were replaced with phosphate ester, carbonate ester, and carboxylate ester. Compared with the ether solvents, the cycle life of the battery cells was reduced. In comparative example 12, the first lithium salt was not dissolved and no soft pack was made, indicating that the compatibility of ester solvents with lithium metal negative electrodes was worse than that of ether solvents.

[0228] Table 2:

[0229]

[0230] From Table 2 we can see that:

[0231] Compared with the electrolytes of Comparative Examples 1 to 14, the electrolytes of Examples 1 to 21 have better solubility;

[0232] Compared to batteries prepared using the electrolytes of Comparative Examples 1 to 14, batteries prepared using the electrolytes of Examples 1 to 21 exhibited longer cycle life, lower initial impedance, and higher solvent retention. This indicates that the electrolytes of the present application, when used in batteries, can provide batteries with longer cycle life, lower initial impedance, and higher solvent retention.

[0233] The above is a detailed introduction to the technical solutions provided in the embodiments of the present application. 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 those skilled in the art, based on the ideas of the present application, there may 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, characterized in that: The method comprises a first lithium salt, a second lithium salt, an additive, a solvent and a solubilizer, wherein: The solvent includes one or more of cyclic ethers and chain ethers with 3 to 10 main chain atoms; The solubilizing agent includes one or more of a sulfone solvent and a chain ether having a main chain atom number of 10 to 15; The additive includes a diluent, and the diluent includes one or more of 1,2,2-trifluoro-1,1,2-trichloroethane, 1,1,1-trifluoro-2-[(2,2,2-trifluoroethoxy)methoxy]ethane, tris(trifluoroethoxy)methane, bis(2,2,2-trifluoroethyl) ether, 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and fluorobenzene; The volume ratio of the solvent to the additive is 1:(2-8), and the ratio between the amount of the first lithium salt and the volume of the solvent is in the range of (3 mol-8 mol):1 L; The first lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalatoborate, lithium difluorophosphate, lithium hexafluorophosphate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and lithium perchlorate; the second lithium salt includes LiNO3; The ratio between the amount of the second lithium salt and the volume of the solubilizer is (1-22) mol:1L; The molar ratio of the first lithium salt to the second lithium salt is 10:(0.2-4.4); The concentration of the second lithium salt is 0.5 to 2.0 mol / L.

2. The electrolyte according to claim 1, wherein Includes one or more of the following features (1) to (4): (1) The cyclic ether includes one or more of 1,3-dioxolane, tetrahydrofuran, furan, tetrahydropyran, and 2,2-dimethoxy-4-(trifluoromethyl)-1,3-dioxolane ether; (2) The chain ether having 3 to 10 main chain atoms includes one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and diethylene glycol dimethyl ether; (3) The sulfone solvent includes one or more of dimethyl sulfoxide, sulfolane, diethyl sulfoxide, tetramethyl sulfoxide, and 3-methylsulfolane; (4) The chain ether having 10 to 15 main chain atoms includes one or more of diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, and ethylene glycol dipropylene glycol ether.

3. A method for preparing an electrolyte according to claim 1 or 2, characterized in that: The process includes the following steps: dissolving a first lithium salt in a solvent to obtain a first lithium salt solution; dissolving the second lithium salt in a solubilizing agent to obtain a second lithium salt solution; mixing the first lithium salt solution and the second lithium salt solution to obtain a mixed solution; as well as Adding additives to the mixed solution to obtain an electrolyte.

4. The preparation method according to claim 3, wherein Includes one or more of the following features (1) to (2): (1) The solvent comprises one or more of a cyclic ether and a chain ether having 3 to 10 main chain atoms; (2) The solubilizing agent includes one or more of a sulfone solvent and a chain ether having a main chain atomic number of 10 to 15.

5. The preparation method according to claim 4, wherein Includes one or more of the following features (1) to (4): (1) The cyclic ether includes one or more of 1,3-dioxolane, tetrahydrofuran, furan, tetrahydropyran, and 2,2-dimethoxy-4-(trifluoromethyl)-1,3-dioxolane ether; (2) The chain ether having 3 to 10 main chain atoms includes one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and diethylene glycol dimethyl ether; (3) The sulfone solvent includes one or more of dimethyl sulfoxide, sulfolane, diethyl sulfoxide, tetramethyl sulfoxide, and 3-methylsulfolane; (4) The chain ether having 10 to 15 main chain atoms includes one or more of diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, and ethylene glycol dipropylene glycol ether.

6. The preparation method according to claim 4, wherein Includes one or more of the following features (1) to (7): (1) The first lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalatoborate, lithium difluorophosphate, lithium hexafluorophosphate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and lithium perchlorate; (2) the second lithium salt includes LiNO3; (3) The additive includes a diluent, and the diluent includes one or more of 1,2,2-trifluoro-1,1,2-trichloroethane, 1,1,1-trifluoro-2-[(2,2,2-trifluoroethoxy)methoxy]ethane, tris(trifluoroethoxy)methane, bis(2,2,2-trifluoroethyl) ether, 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and fluorobenzene; (4) The ratio between the amount of the first lithium salt and the volume of the solvent is in the range of (3 mol to 8 mol):1 L; (5) The volume ratio of the solvent to the additive is 1:(2-8); (6) The ratio between the amount of the second lithium salt and the volume of the solubilizer is (1-22) mol:1L; (7) The molar ratio of the first lithium salt to the second lithium salt is 10:(0.2-4.4).

7. A battery, characterized in that: The electrolyte comprises the electrolyte described in any one of claims 1 or 2, or the electrolyte prepared by the preparation method described in any one of claims 3-6.

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