Lithium-sulfur battery, electrolyte and electric equipment

Abstract

The invention discloses a lithium-sulfur battery, an electrolyte and electric equipment, and belongs to the field of secondary batteries, the lithium-sulfur battery comprises a positive pole piece, the electrolyte and a negative pole piece, the electrolyte comprises a first electrolyte and a second electrolyte, the first electrolyte comprises thioether, the second electrolyte comprises electrolyte salt and a solvent, and the solvent is a solvent. In the electrolyte salt and the solvent, the amount-of-substance concentration of the electrolyte salt is greater than or equal to 5 mol / L. The lithium-sulfur battery provided by the invention has excellent specific capacity and cycle performance.

Description

Technical Field

[0001] This application belongs to the field of secondary batteries, specifically relating to a lithium-sulfur battery, an electrolyte, and an electrical device. Background Technology

[0002] Secondary batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0003] Lithium-sulfur batteries are a type of lithium battery that uses sulfur as the positive electrode and metallic lithium as the negative electrode. Elemental sulfur is abundant on Earth and is characterized by its low price and environmental friendliness. Lithium-sulfur batteries using sulfur as the positive electrode material have high theoretical specific capacity and theoretical specific energy, reaching 1675 mAh / g and 2600 Wh / kg, respectively. However, lithium polysulfides, an intermediate product of lithium-sulfur batteries, are readily soluble in the electrolyte and can shuttle to the metallic lithium side of the negative electrode. They undergo side reactions with the metallic lithium, consuming it and forming non-conductive lithium sulfide that coats the surface of the metallic lithium, leading to a decrease in capacity and cycle performance. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides a lithium-sulfur battery, which aims to improve the capacity and cycle performance of lithium-sulfur batteries.

[0005] To achieve the above objectives, the first aspect of this application proposes a lithium-sulfur battery, which includes a positive electrode, an electrolyte, and a negative electrode. The electrolyte includes a first electrolyte and a second electrolyte. The first electrolyte includes a sulfide, and the second electrolyte includes an electrolyte salt and a solvent. The concentration of the electrolyte salt is greater than or equal to 5 mol / L.

[0006] This application includes at least the following beneficial effects: The lithium-sulfur battery of this application includes two electrolytes, which can suppress the shuttle of intermediate product lithium polysulfide and improve the contact of the positive electrode, thereby improving the capacity and cycle performance of the lithium-sulfur battery.

[0007] In some embodiments, the sulfide comprises R1-S n -R2, where n = 2-3, and R1 and R2 each independently include one or more of methyl, phenyl, ethyl, n-propyl, isopropyl, or propenyl groups. This can improve the capacity and cycle performance of lithium-sulfur batteries.

[0008] In some embodiments, R1 and R2 each independently comprise one or more of methyl or phenyl groups. This can improve the capacity and cycle performance of lithium-sulfur batteries.

[0009] In some embodiments, the sulfide includes one or more of the following: CH3-SS-CH3, C6H5-SSS-C6H5, C6H5-SS-C6H5, C6H5-SSS-CH3, C6H5-SS-CH3, CH3CH2-SS-CH2CH3, CH3CH2-SSS-CH2CH3, CH3CH2CH2-SS-CH2CH2CH3, CH3CH2CH2-SSS-CH2CH2CH3, CH3-SS-CH2CH3, CH3-SSS-CH2CH3, CH3-SS-CH2CH2CH3, CH3-SS-CH2CH2CH3, or CH3-SSS-CH2CH2CH3. This can improve the capacity and cycle performance of lithium-sulfur batteries.

[0010] In some embodiments, the first electrolyte further includes a first solvent, which comprises one or more of the following: 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, pentaethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, 1,3-dioxane, or dimethyl ether. This can improve the capacity and cycle performance of lithium-sulfur batteries.

[0011] In some embodiments, the molar concentration of the sulfide in the first electrolyte is 1 mol / L to 10 mol / L. This can improve the capacity and cycle performance of the lithium-sulfur battery.

[0012] In some embodiments, the molar concentration of the electrolyte salt in the second electrolyte is greater than or equal to 5 mol / L. This can improve the capacity and cycle performance of the lithium-sulfur battery.

[0013] In some embodiments, the molar concentration of the electrolyte salt in the second electrolyte is 5 mol / L to 10 mol / L. This can improve the capacity and cycle performance of the lithium-sulfur battery.

[0014] In some embodiments, the electrolyte salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, or lithium tetrafluorooxalate phosphate. This can improve the capacity and cycle performance of lithium-sulfur batteries.

[0015] In some embodiments, the solvent includes one or more of 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, pentaethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, 1,3-dioxane, or dimethyl ether. This can improve the capacity and cycle performance of lithium-sulfur batteries.

[0016] In some embodiments, the second electrolyte further includes a diluent comprising one or more of 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, or 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether. This can improve the capacity and cycle performance of the lithium-sulfur battery.

[0017] In some embodiments, the volume ratio of the first electrolyte to the second electrolyte in the electrolyte is (5:95) to (30:70). This can improve the capacity and cycle performance of the lithium-sulfur battery.

[0018] In some embodiments, the positive electrode includes a positive active material comprising conductive carbon and sulfur. This can improve the capacity and cycle performance of lithium-sulfur batteries.

[0019] In some embodiments, the mass ratio of the conductive carbon to the sulfur is (1:9) to (5:5). This can improve the capacity and cycle performance of lithium-sulfur batteries.

[0020] In some embodiments, the positive electrode includes a current collector and a positive electrode slurry disposed on at least one side of the current collector, the positive electrode slurry comprising a positive electrode active material and the electrolyte. This can improve the capacity and cycle performance of the lithium-sulfur battery.

[0021] In some embodiments, the mass ratio of the components in the positive electrode slurry is: positive electrode active material: electrolyte: conductive agent = (10-50): (50-90): (0.5-10). This can improve the capacity and cycle performance of lithium-sulfur batteries.

[0022] In a second aspect, this application provides an electrolyte comprising a first electrolyte and a second electrolyte. The first electrolyte comprises a sulfide, and the second electrolyte comprises an electrolyte salt and a solvent. The molar concentration of the electrolyte salt is greater than or equal to 5 mol / L. Using two electrolytes can suppress the shuttling of the intermediate lithium polysulfide and improve the contact of the positive electrode, thereby enhancing the capacity and cycle performance of the lithium-sulfur battery.

[0023] In some embodiments, the sulfide comprises R1-S n -R2, where n = 2-3, and R1 and R2 each independently include one or more of methyl, phenyl, ethyl, n-propyl, isopropyl, or propenyl groups. This can improve the capacity and cycle performance of lithium-sulfur batteries.

[0024] In some embodiments, R1 and R2 each independently comprise one or more of methyl or phenyl groups. This can improve the capacity and cycle performance of lithium-sulfur batteries.

[0025] In some embodiments, the sulfide includes one or more of the following: CH3-SS-CH3, C6H5-SSS-C6H5, C6H5-SS-C6H5, C6H5-SSS-CH3, C6H5-SS-CH3, CH3CH2-SS-CH2CH3, CH3CH2-SSS-CH2CH3, CH3CH2CH2-SS-CH2CH2CH3, CH3CH2CH2-SSS-CH2CH2CH3, CH3-SS-CH2CH3, CH3-SSS-CH2CH3, CH3-SS-CH2CH2CH3, CH3-SS-CH2CH2CH3, or CH3-SSS-CH2CH2CH3. This can improve the capacity and cycle performance of lithium-sulfur batteries.

[0026] In some embodiments, the first electrolyte further includes a first solvent, which comprises one or more of the following: 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, pentaethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, 1,3-dioxane, or dimethyl ether. This can improve the capacity and cycle performance of lithium-sulfur batteries.

[0027] In some embodiments, the molar concentration of the sulfide in the first electrolyte is 1 mol / L to 10 mol / L. This can improve the capacity and cycle performance of the lithium-sulfur battery.

[0028] In some embodiments, the molar concentration of the electrolyte salt in the second electrolyte is greater than or equal to 5 mol / L. This can improve the capacity and cycle performance of the lithium-sulfur battery.

[0029] In some embodiments, the molar concentration of the electrolyte salt in the second electrolyte is 5 mol / L to 10 mol / L. This can improve the capacity and cycle performance of the lithium-sulfur battery.

[0030] In some embodiments, the electrolyte salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, or lithium tetrafluorooxalate phosphate. This can improve the capacity and cycle performance of lithium-sulfur batteries.

[0031] In some embodiments, the solvent includes one or more of 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, pentaethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, 1,3-dioxane, or dimethyl ether. This can improve the capacity and cycle performance of lithium-sulfur batteries.

[0032] In some embodiments, the second electrolyte further includes a diluent comprising one or more of 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, or 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether. This can improve the capacity and cycle performance of the lithium-sulfur battery.

[0033] In some embodiments, the volume ratio of the first electrolyte to the second electrolyte in the electrolyte is (5:95) to (30:70). This can improve the capacity and cycle performance of the lithium-sulfur battery.

[0034] In a third aspect of this application, an electrical device is proposed, including the lithium-sulfur battery described in the first aspect of this application.

[0035] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0036] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0037] Figure 1 This is a schematic diagram of a battery according to one embodiment of this application.

[0038] Figure 2 yes Figure 1 An exploded view of a battery according to one embodiment of this application is shown.

[0039] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0040] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0041] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0042] Figure 6 This is a schematic diagram of an electrical device in which a battery is used as a power source according to one embodiment of this application.

[0043] Figure 7 This is a photograph of the electrolyte prepared in Example 1 of this application.

[0044] Figure 8 These are cycle performance test curves of lithium-sulfur batteries in Examples 1 and 1-3 of this application.

[0045] Figure 9 This is a specific capacity test curve of the lithium-sulfur battery of Example 1 and Comparative Examples 1-3 of this application.

[0046] Explanation of reference numerals in the attached figures:

[0047] 1. Battery cell; 11. Housing; 12. Electrode assembly; 13. Cover plate; 2. Battery module; 3. Battery pack; 31. Upper casing; 32. Lower casing. Detailed Implementation

[0048] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0049] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0050] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0051] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0052] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0053] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0054] Currently, judging from market trends, the application of rechargeable batteries is becoming increasingly widespread. Rechargeable batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace, among other fields.

[0055] Lithium-sulfur batteries are a type of lithium battery that uses sulfur as the positive electrode and metallic lithium as the negative electrode. Elemental sulfur is abundant on Earth and is inexpensive and environmentally friendly. Lithium-sulfur batteries using sulfur as the positive electrode material have high theoretical specific capacity and theoretical specific energy, reaching 1675 mAh / g and 2600 Wh / kg, respectively. However, lithium polysulfides, an intermediate product of lithium-sulfur batteries, are readily soluble in the electrolyte and can shuttle to the metallic lithium side of the negative electrode. They undergo side reactions with the metallic lithium, consuming it and forming non-conductive lithium sulfide covering the surface of the metallic lithium, leading to a decrease in capacity and cycle performance. On the other hand, the dense, non-conductive lithium sulfide generated during battery discharge reduces the contact between sulfur positive electrode particles, disrupting the conductive network and also resulting in a decrease in capacity and cycle performance.

[0056] Regarding the shuttling problem of lithium polysulfides, existing technologies use electrolytes that are difficult to dissolve lithium polysulfides, such as locally high-concentration or high-concentration electrolytes, to suppress the shuttling of lithium polysulfides. However, this causes the reaction of the sulfur cathode to change to a solid-solid reaction, which hinders the kinetics and reduces the battery's capacity and cycle performance. Regarding the problem of damage to the conductive network, existing technologies reduce the sulfur content of the cathode and increase the conductive carbon content, but this leads to a decrease in the battery's energy density.

[0057] The lithium-sulfur battery of this application embodiment includes a first electrolyte and a second electrolyte. The two electrolytes are essentially immiscible. The organic sulfide in the first electrolyte has a strong interaction with the sulfur-containing positive electrode and tends to accumulate on the surface of the sulfur-containing positive electrode. Furthermore, the sulfide can dissolve the intermediate lithium polysulfide, ensuring a rapid solid-liquid-solid reaction. This confines the lithium polysulfide and sulfide to the positive electrode side, reducing their migration to the negative electrode side and causing side reactions, thus improving the capacity and cycle performance of the lithium-sulfur battery. In addition, the sulfide molecules can react with some elemental sulfur in the positive electrode to form organic sulfide intermediates. These intermediates can then react further at the positive electrode active material. The material particles form three-dimensional, non-dense products, making it difficult for non-conductive lithium sulfide generated during discharge to re-enter the spaces between the positive electrode active material particles. This ensures that the electrical contact between the positive electrode active material particles is largely unaffected, improving the battery's cycle performance. Simultaneously, the use of a second electrolyte that is immiscible with the first electrolyte, with the electrolyte salt concentration greater than or equal to 5 mol / L in both the electrolyte salt and solvent, creates a high-concentration or locally high-concentration electrolyte. Lithium polysulfides have extremely low solubility in this electrolyte, further suppressing lithium polysulfide shuttle and improving battery capacity and cycle performance. In summary, the lithium-sulfur battery proposed in this application exhibits excellent capacity and cycle performance.

[0058] The lithium-sulfur battery disclosed in this application can be used in electrical devices that use batteries as a power source or in various energy storage systems that use batteries as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0059] The first aspect of this application discloses a lithium-sulfur battery, which includes a positive electrode, an electrolyte, and a negative electrode. The electrolyte includes a first electrolyte and a second electrolyte. The first electrolyte includes a sulfide, and the second electrolyte includes an electrolyte salt and a solvent. The molar concentration of the electrolyte salt is greater than or equal to 5 mol / L.

[0060] As an example, the molar concentration of the electrolyte salt in the electrolyte salt and solvent can be 5 mol / L-9.9 mol / L, 5.5 mol / L-9.5 mol / L, 6 mol / L-9 mol / L, 6.5 mol / L-8.5 mol / L, 7 mol / L-8 mol / L, etc.

[0061] The lithium-sulfur battery of this application embodiment includes a first electrolyte and a second electrolyte. The two electrolytes are essentially immiscible. The organic sulfide in the first electrolyte has a strong interaction with the sulfur-containing positive electrode and tends to accumulate on the surface of the sulfur-containing positive electrode. Furthermore, the sulfide can dissolve the intermediate lithium polysulfide, ensuring a rapid solid-liquid-solid reaction. This confines the lithium polysulfide and sulfide to the positive electrode side, reducing their migration to the negative electrode side and the occurrence of side reactions, thus improving the capacity and cycle performance of the lithium-sulfur battery. In addition, the sulfide molecules can react with the elemental sulfur in the positive electrode to form an organic sulfide intermediate. This intermediate can then react further at the active electrode. The formation of three-dimensional, non-dense products between material particles makes it difficult for non-conductive lithium sulfide generated during discharge to re-enter the spaces between the positive electrode active material particles. This ensures that the electrical contact between the positive electrode active material particles is largely unaffected, improving the battery's cycle performance. Simultaneously, the use of a second electrolyte that is immiscible with the first electrolyte, with the electrolyte salt concentration greater than or equal to 5 mol / L in both the electrolyte salt and solvent, creates a high-concentration or locally high-concentration electrolyte. Lithium polysulfides have extremely low solubility in this electrolyte, which inhibits lithium polysulfide shuttle, further enhancing the battery's capacity and cycle performance. In summary, the lithium-sulfur battery proposed in this application exhibits excellent capacity and cycle performance.

[0062] It is understandable that the first electrolyte and the second electrolyte can be obtained by disassembling the battery, pouring out the electrolyte, and separating them into layers.

[0063] Understandably, the concentrations of electrolyte salts and lithium salts in the solvent of the second electrolyte can be determined by ion chromatography, referring to JY / T 020-1996.

[0064] If the second electrolyte is a locally high-concentration electrolyte (containing diluent), the concentrations of lithium salts in the electrolyte salt and solvent can be determined by the following methods:

[0065] The amount of electrolyte salt in the second electrolyte is determined by ion chromatography according to JY / T 020-1996, and the amount of solvent and diluent is determined by gas chromatography according to GB / T 9722-2006, thereby determining the concentration of lithium salt in the solvent of the second electrolyte.

[0066] Understandably, the organic sulfides in the first electrolyte can be qualitatively and quantitatively analyzed by gas chromatography, referring to standard GB / T 9722-2006.

[0067] In some embodiments of this application, the sulfide comprises R1-S n-R2, where n = 2-3, R1 and R2 each independently include one or more of methyl, phenyl, ethyl, n-propyl, isopropyl, or propenyl. As an example, n can be 2, 3, etc. The aforementioned sulfide acts as a redox medium, enabling the non-conductive lithium sulfide generated during discharge to be loosely deposited on the surface of the positive electrode active material, causing less damage to the conductive network of the positive electrode active material. It also confines lithium polysulfides and sulfides to the positive electrode side, reducing their shuttle to the negative electrode side and the occurrence of side reactions, thereby improving the capacity and cycle performance of the battery containing them. In other embodiments of this application, R1 and R2 each independently include one or more of methyl or phenyl.

[0068] In some embodiments of this application, the sulfide includes one or more of CH3-SS-CH3, C6H5-SSS-C6H5, C6H5-SS-C6H5, C6H5-SSS-CH3, C6H5-SS-CH3, CH3CH2-SS-CH2CH3, CH3CH2-SSS-CH2CH3, CH3CH2CH2-SS-CH2CH2CH3, CH3CH2CH2-SSS-CH2CH2CH3, CH3-SS-CH2CH3, CH3-SSS-CH2CH3, CH3-SS-CH2CH2CH3, CH3-SSS-CH2CH2CH3, or CH3-SSS-CH3. The aforementioned sulfide acts as a redox medium, enabling the non-conductive lithium sulfide generated during discharge to be loosely deposited on the surface of the positive electrode active material. This results in less damage to the conductive network of the positive electrode active material. Furthermore, it confines lithium polysulfides and sulfides to the positive electrode side, reducing their shuttle to the negative electrode side and causing side reactions, thereby improving the capacity and cycle performance of batteries containing them.

[0069] In some embodiments of this application, the first electrolyte further includes a first solvent, which comprises one or more of the following: 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, pentaethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, 1,3-dioxane, or dimethyl ether. The above solvents are ether solvents, which can further improve the solubility of lithium polysulfide intermediates in the first electrolyte, thereby enhancing the capacity and cycle performance of batteries containing them.

[0070] In some embodiments of this application, the molar concentration of the sulfide in the first electrolyte is 1 mol / L-10 mol / L. For example, the molar concentration of the sulfide in the first electrolyte can be 1 mol / L-9.9 mol / L, 2 mol / L-9 mol / L, 3 mol / L-8 mol / L, 4 mol / L-7 mol / L, 5 mol / L-6 mol / L, etc. Controlling the molar concentration of the sulfide within the above range can reduce the localized deterioration of ionic conductivity caused by excessively high sulfide content, and can also reduce the indistinct phase separation of the first and second electrolytes caused by excessively low sulfide content, thereby improving the capacity and cycle performance of the battery containing it.

[0071] In some embodiments of this application, the molar concentration of the electrolyte salt in the second electrolyte is greater than or equal to 5 mol / L. For example, the molar concentration of the electrolyte salt in the second electrolyte is 5 mol / L-9.9 mol / L, 5.5 mol / L-9.5 mol / L, 6 mol / L-9 mol / L, 6.5 mol / L-8.5 mol / L, 7 mol / L-8 mol / L, etc. The second electrolyte is a high-concentration electrolyte, in which lithium polysulfides have extremely low solubility, which can suppress lithium polysulfide shuttle and improve battery capacity and cycle performance. In other embodiments of this application, the molar concentration of the electrolyte salt in the second electrolyte is 5 mol / L-10 mol / L.

[0072] In some embodiments of this application, the electrolyte salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, or lithium tetrafluorooxalate phosphate. The above-mentioned electrolyte salts exhibit high stability and compatibility with the first and second electrolytes, thereby improving the capacity and cycle performance of batteries containing them.

[0073] In some embodiments of this application, the solvent includes one or more of the following: 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, pentaethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, 1,3-dioxane, or dimethyl ether. These ether solvents are compatible with lithium metal anodes and sulfur-containing cathodes, exhibit strong stability, and can improve the capacity and cycle performance of batteries containing them.

[0074] In some embodiments of this application, the second electrolyte further includes a diluent, which includes one or more of 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, or 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether. The above-mentioned diluent can reduce the viscosity of the electrolyte, improve the wetting performance, maintain the electrochemical stability of the high-concentration electrolyte, inhibit the formation of lithium dendrites, improve the ionic conductivity, and improve the capacity and cycle performance of the battery containing it.

[0075] This is understandable. You can refer to standard GB / T 9722-2006 for qualitative and quantitative analysis of the diluent in the second electrolyte using gas chromatography.

[0076] In some embodiments of this application, the volume ratio of the first electrolyte to the second electrolyte in the electrolyte is (5:95)-(30:70). For example, it can be 5:95, 10:90, 15:85, 20:80, 25:75, 30:70, etc. Specifically, controlling the volume ratio of the first electrolyte to the second electrolyte within the above range further facilitates the full utilization of the first electrolyte and the second electrolyte, reduces the probability of lithium polysulfide migrating to the negative electrode, reduces the probability of the conductive network of the positive electrode active material being damaged, and improves the capacity and cycle performance of the lithium-sulfur battery.

[0077] It is understood that the "volume ratio of the first electrolyte to the second electrolyte" is a well-known definition in the art and can be determined using methods known in the art, such as the following methods:

[0078] The lithium-sulfur battery was disassembled, the electrolyte was poured out, and after standing and separating into layers, the first electrolyte and the second electrolyte were separated. The first electrolyte and the second electrolyte were identified by gas chromatography according to standard GB / T 9722-2006. The volumes of the two electrolytes were measured to obtain the volume ratio of the first electrolyte and the second electrolyte.

[0079] In some embodiments of this application, the positive electrode sheet includes a positive electrode active material, which includes conductive carbon and sulfur. The addition of conductive carbon can improve the conductivity of the positive electrode sheet, and the conductive carbon can also adsorb lithium polysulfides to a certain extent, reducing their migration to the negative electrode. It also helps to buffer volume expansion, improve sulfur utilization and sulfur loading, and promote the conversion reaction of polysulfides, thereby significantly improving the cycle performance of lithium-sulfur batteries.

[0080] In some embodiments of this application, the mass ratio of the conductive carbon to the sulfur is (1:9)-(5:5), for example, it can be 1:9, 2:8, 3:7, 4:6, 5:5, etc. Controlling the mass ratio of conductive carbon to sulfur within the above range can further improve the conductivity of the positive electrode, reduce the migration of lithium polysulfides to the negative electrode, and also help buffer volume expansion, improve sulfur utilization and sulfur loading, and promote the conversion reaction of polysulfides, thereby significantly improving the cycle performance of lithium-sulfur batteries. In addition, it can also take into account the energy density of lithium-sulfur batteries.

[0081] It is understood that the mass ratio of conductive carbon to sulfur is a well-known definition in the art and can be determined using methods known in the art, such as the following methods:

[0082] Taking advantage of the fact that sulfur sublimates between 100 and 500°C, thermogravimetric analysis was used in a nitrogen atmosphere to quantify the weight difference between 500°C and 100°C. This difference corresponds to the mass of sulfur in the carbon-sulfur complex. The mass of conductive carbon is obtained by subtracting the amount of sulfur from the initial amount, and thus the mass ratio of the two can be obtained.

[0083] In some embodiments of this application, the positive electrode includes a current collector and a positive electrode slurry disposed on at least one side of the current collector. The positive electrode slurry includes a positive electrode active material and the electrolyte. Therefore, the above-mentioned battery is a lithium-sulfur slurry battery. By directly dispersing the positive electrode active material in the electrolyte, the traditional steps of coating and drying the positive electrode can be saved, reducing the cost of lithium-sulfur batteries. Furthermore, it facilitates the recycling of the positive electrode active material and can improve the capacity and cycle performance of lithium-sulfur batteries.

[0084] In some embodiments of this application, the mass ratio of each component in the positive electrode slurry is: positive electrode active material: electrolyte: conductive agent = (10-50):(50-90):(0.5-10). For example, the mass ratio of the three can be 10:89:1, 30:60:10, 50:49.5:0.5, etc. The addition of the conductive agent can improve the conductivity of the positive electrode side. Controlling the mass ratio of each component in the positive electrode slurry within the above range can further improve the conductivity of the positive electrode sheet, reduce the migration of lithium polysulfides to the negative electrode, and also help buffer volume expansion, improve sulfur utilization and sulfur loading, and promote the conversion reaction of polysulfides, thereby significantly improving the cycle performance of lithium-sulfur batteries.

[0085] Typically, a lithium-sulfur battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. Sulfur is used as the positive electrode reactant, and lithium is used as the negative electrode. During discharge, the negative electrode reaction involves lithium losing electrons to become lithium ions, while the positive electrode reaction involves sulfur reacting with lithium ions and electrons to form sulfides. The potential difference between the positive and negative electrode reactions is the discharge voltage provided by the lithium-sulfur battery. Under the influence of an applied voltage, the positive and negative electrode reactions of the lithium-sulfur battery proceed in reverse, which is the charging process.

[0086] [Electrolytes]

[0087] In a second aspect, this application proposes an electrolyte comprising a first electrolyte and a second electrolyte. The first electrolyte comprises a sulfide, and the second electrolyte comprises an electrolyte salt and a solvent. The molar concentration of the electrolyte salt is greater than or equal to 5 mol / L. Using two electrolytes can suppress the shuttle of the intermediate lithium polysulfide and improve the contact of the positive electrode, thereby enhancing the capacity and cycle performance of the lithium-sulfur battery.

[0088] It is understood that the electrolyte proposed in this application has some additional features, which have been detailed above and will not be repeated here.

[0089] As an example, the electrolyte of this application can be prepared by separately preparing a first electrolyte and a second electrolyte, and then mixing the two electrolytes to obtain the electrolyte.

[0090] This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or completely solid.

[0091] In some embodiments of this application, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0092] In some embodiments of this application, the solvent and the first solvent may also independently include ester solvents, which may include at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, or diethyl sulfone.

[0093] In some embodiments of this application, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0094] [Negative electrode plate]

[0095] In some embodiments of this application, the negative electrode sheet comprises a lithium metal alloy with the chemical formula LiR, wherein R comprises at least one of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, platinum, boron, carbon, or silicon.

[0096] [Positive electrode plate]

[0097] In some embodiments of this application, the positive electrode includes a positive current collector, which may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0098] In some embodiments of this application, the positive electrode active material forms a positive electrode active material layer on the positive electrode current collector.

[0099] In some embodiments of this application, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0100] In some embodiments of this application, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0101] In some embodiments of this application, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0102] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0103] In some embodiments of this application, the material of the separator may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0104] The batteries of this application include battery cells, battery modules, and battery packs. The battery cells, battery modules, and battery packs of this application will be described below with appropriate reference to the accompanying drawings.

[0105] In some embodiments of this application, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly by a winding process or a stacking process.

[0106] In some embodiments of this application, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0107] In some embodiments of this application, the outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0108] It is understood that the lithium-sulfur battery mentioned above in this application is a single battery cell.

[0109] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 Here is a square-structured battery cell 1 as an example.

[0110] In some embodiments of this application, reference is made to Figure 2 The outer packaging may include a housing 11 and a cover plate 13. The housing 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator can be formed into an electrode assembly 12 by a winding process or a stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 12. The number of electrode assemblies 12 contained in a single battery cell 1 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0111] In some embodiments of this application, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0112] Figure 3 This is battery module 2 as an example. (See reference...) Figure 3 In battery module 2, multiple battery cells 1 can be arranged sequentially along the length of battery module 2. Of course, they can also be arranged in any other way. Furthermore, these multiple battery cells 1 can be fixed in place using fasteners.

[0113] Optionally, the battery module 2 may also include a housing with a receiving space in which multiple battery cells 1 are received.

[0114] In some embodiments of this application, the battery modules described above can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0115] Figure 4 and Figure 5 This is battery pack 3 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box includes an upper box 31 and a lower box 32, with the upper box 31 covering the lower box 32 to form a closed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0116] In addition, this application also provides an electrical device, which includes the lithium-sulfur battery provided in the first aspect of this application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0117] As the electrical equipment, battery cells, battery modules, or battery packs can be selected according to their usage requirements.

[0118] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density batteries, a battery pack or battery module can be used.

[0119] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0120] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0121] Example 1

[0122] 1. Electrolyte

[0123] Dissolve 0.8 mol of LiFSI (lithium bisfluorosulfonylimide) in 100 mL of DME (ethylene glycol dimethyl ether) to obtain 8 M LiFSI@DME (second electrolyte); dissolve 0.5 mol of DMTS (dimethyl trisulfide) in 100 mL of DME (ethylene glycol dimethyl ether) to obtain 5 M DMTS@DME (first electrolyte); mix 10 mL of 5 M DMTS@DME and 90 mL of 8 M LiFSI@DME to obtain the phased electrolyte, i.e., 10 vol% (5 M DMTS@DME) + 90 vol% (8 M LiFSI@DME).

[0124] 2. Positive electrode plate

[0125] Preparation of positive electrode active materials:

[0126] Elemental sulfur powder and Ketjen black conductive carbon were mixed in a mass ratio of 8:2, and then kept at 155°C for 12 hours under a nitrogen atmosphere to obtain an S / C composite positive electrode active material.

[0127] The positive electrode is a slurry-like positive electrode slurry. The method for preparing the positive electrode slurry is to mix the S / C composite positive electrode active material, the corresponding electrolyte, and Ketjen black particles (conductive agent) in a mass ratio of 20:79:1 to form a positive electrode slurry.

[0128] 3. Negative electrode plate

[0129] A lithium metal sheet with a thickness of 1000 μm was used as the negative electrode.

[0130] 4. Separating membrane

[0131] A glass fiber sheet with a thickness of 2000μm was used as the diaphragm.

[0132] 5. Preparation of lithium-sulfur batteries

[0133] The assembly form is a button cell: First, place the lithium metal sheet on the negative electrode shell, then cover it with a glass fiber separator, then cover it with a carbon felt as a current collector, then drop 400mg of the above positive electrode slurry onto the carbon felt, then cover it with the positive electrode shell, and finally use a button cell packaging machine to press and seal the battery to obtain a lithium slurry battery.

[0134] The preparation methods of lithium-sulfur batteries in Examples 2-15 and Comparative Examples 1-4 are the same as those in Example 1, except that the electrolyte preparation process is different. In Example 9, no first solvent is added, only sulfide. In Examples 10 and 11, the molar concentration of lithium salt refers to the molar concentration of lithium salt in the lithium salt and solvent. Comparative Example 1 uses an electrolyte with a lithium salt concentration of 1 mol / L (i.e., 1M LiFSI@DME). Comparative Example 2 uses only the second electrolyte (i.e., 8M LiFSI@DME). Comparative Example 3 uses only the first electrolyte and lithium salt (i.e., 5M DMTS@DME containing 1 mol / L lithium salt LiFSI). Comparative Example 4 is a combination of the first electrolyte (i.e., 5M DMTS@DME) and an electrolyte with a lithium salt concentration of 3 mol / L (i.e., 3M LiFSI@DME), as shown in Table 1.

[0135] Table 1

[0136]

[0137]

[0138] The image of the electrolyte prepared in Example 1 is shown below. Figure 7 As shown, the electrolyte consists of two phases: the upper pale yellow layer is 5M DMTS@DME (the first electrolyte), and the lower layer is 8M LiFSI@DME (the second electrolyte).

[0139] The cycle performance and discharge specific capacity of the lithium-sulfur batteries of Examples 1-15 and Comparative Examples 1-4 were characterized, and the characterization results are shown in Table 2.

[0140] 1. Cycle performance test: Each lithium-sulfur battery was charged to 3V at room temperature with a current density of 100mA / g, and then discharged to 1.5V with a current density of 100mA / g. The reversible capacity was measured as C0. After repeating the charge-discharge cycle 30 times, the reversible capacity was measured as Cn. The cycle capacity retention rate = Cn / C0 × 100%.

[0141] 2. Discharge specific capacity test: Each lithium-sulfur battery was charged to 3V at room temperature with a current density of 100mA / g, and then discharged to 1.5V with a current density of 100mA / g. The reversible capacity was measured as the discharge specific capacity. The results are shown in Table 2.

[0142] Following the above method, the cycle performance test curves and discharge specific capacity test curves of Examples 1-3 in Example 1 are as follows: Figure 8 and Figure 9 As shown, the lithium-sulfur battery of Example 1 of this application has significantly better cycle performance and discharge specific capacity than Comparative Examples 1-3.

[0143] Table 2

[0144]

[0145]

[0146] As can be seen from Table 2, in Examples 1-15 of this application, there are two electrolytes, namely a first electrolyte and a second electrolyte, and the capacity and cycle performance of the lithium-sulfur battery are excellent. Compared to Examples 1-15, Comparative Example 1 used an electrolyte with a lithium salt concentration of 1 mol / L (i.e., 1M LiFSI@DME), Comparative Example 2 only used a second electrolyte (i.e., 8M LiFSI@DME), Comparative Example 3 only used a first electrolyte and lithium salt (i.e., 5M DMTS@DME containing 1 mol / L lithium salt LiFSI), and Comparative Example 4 was a combination of a first electrolyte (i.e., 5M DMTS@DME) and an electrolyte with a lithium salt concentration of 3 mol / L (i.e., 3M LiFSI@DME). That is, Comparative Examples 1-4 did not use a first electrolyte and a second electrolyte simultaneously. Due to the presence of sulfide, Comparative Examples 3 and 4 underwent a solid-liquid-solid reaction, resulting in high specific capacity. However, the lack of a second electrolyte weakened the barrier effect on lithium polysulfides shuttling to the negative electrode, thus leading to poor battery cycle performance. It can be seen that using the lithium-sulfur battery electrolyte of the embodiments of this application can significantly improve the capacity and cycle performance of lithium-sulfur batteries.

[0147] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A lithium-sulfur battery, characterized in that, The lithium-sulfur battery includes a positive electrode, an electrolyte, and a negative electrode. The electrolyte includes a first electrolyte and a second electrolyte. The first electrolyte includes a sulfide, and the second electrolyte includes an electrolyte salt and a solvent. The concentration of the electrolyte salt is greater than or equal to 5 mol / L.

2. The lithium-sulfur battery according to claim 1, characterized in that, The sulfide includes R1-S n -R2, where n = 2-3, and R1 and R2 each independently include one or more of methyl, phenyl, ethyl, n-propyl, isopropyl, or propenyl.

3. The lithium-sulfur battery according to claim 2, characterized in that, R1 and R2 each independently include one or more of methyl or phenyl groups.

4. The lithium-sulfur battery according to any one of claims 1-3, characterized in that, The sulfide includes one or more of the following: CH3-SS-CH3, C6H5-SSS-C6H5, C6H5-SS-C6H5, C6H5-SSS-CH3, C6H5-SS-CH3, CH3CH2-SS-CH2CH3, CH3CH2-SSS-CH2CH3, CH3CH2CH2-SS-CH2CH2CH3, CH3CH2CH2-SSS-CH2CH2CH3, CH3-SS-CH2CH3, CH3-SSS-CH2CH3, CH3-SS-CH2CH2CH3, CH3-SSSS-CH2CH2CH3, or CH3-SSS-CH3.

5. The lithium-sulfur battery according to any one of claims 1-4, characterized in that, The first electrolyte further includes a first solvent, which comprises one or more of the following: 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, pentaethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, 1,3-dioxopentane, or dimethyl ether.

6. The lithium-sulfur battery according to any one of claims 1-5, characterized in that, In the first electrolyte, the molar concentration of the sulfide is 1 mol / L to 10 mol / L.

7. The lithium-sulfur battery according to any one of claims 1-6, characterized in that, In the second electrolyte, the molar concentration of the electrolyte salt is greater than or equal to 5 mol / L.

8. The lithium-sulfur battery according to any one of claims 1-7, characterized in that, In the second electrolyte, the molar concentration of the electrolyte salt is 5 mol / L-10 mol / L.

9. The lithium-sulfur battery according to any one of claims 1-8, characterized in that, The electrolyte salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, or lithium tetrafluorooxalate phosphate.

10. The lithium-sulfur battery according to any one of claims 1-9, characterized in that, The solvent includes one or more of 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, pentaethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, 1,3-dioxopentane, or dimethyl ether.

11. The lithium-sulfur battery according to any one of claims 1-10, characterized in that, The second electrolyte further includes a diluent, which includes one or more of 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, or 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether.

12. The lithium-sulfur battery according to any one of claims 1-11, characterized in that, In the electrolyte, the volume ratio of the first electrolyte to the second electrolyte is (5:95)-(30:70).

13. The lithium-sulfur battery according to any one of claims 1-12, characterized in that, The positive electrode sheet includes a positive active material, which includes conductive carbon and sulfur.

14. The lithium-sulfur battery according to claim 13, characterized in that, The mass ratio of the conductive carbon to the sulfur is (1:9)-(5:5).

15. The lithium-sulfur battery according to any one of claims 1-14, characterized in that, The positive electrode includes a current collector and a positive electrode slurry disposed on at least one side of the current collector, the positive electrode slurry including a positive electrode active material and the electrolyte.

16. The lithium-sulfur battery according to claim 15, characterized in that, In the positive electrode slurry, the mass ratio of each component is: positive electrode active material: electrolyte: conductive agent = (10-50): (50-90): (0.5-10).

17. An electrolyte, characterized in that, The electrolyte includes a first electrolyte and a second electrolyte. The first electrolyte includes a sulfide, and the second electrolyte includes an electrolyte salt and a solvent. The concentration of the electrolyte salt is greater than or equal to 5 mol / L.

18. The electrolyte according to claim 17, characterized in that, The sulfide includes R1-S n -R2, characterized in that n=2-3, R1 and R2 each independently include one or more of methyl, phenyl, ethyl, n-propyl, isopropyl or propenyl.

19. The electrolyte according to claim 18, characterized in that, R1 and R2 each independently include one or more of methyl or phenyl groups.

20. The electrolyte according to any one of claims 17-19, characterized in that, The sulfide includes one or more of the following: CH3-SS-CH3, C6H5-SSS-C6H5, C6H5-SS-C6H5, C6H5-SSS-CH3, C6H5-SS-CH3, CH3CH2-SS-CH2CH3, CH3CH2-SSS-CH2CH3, CH3CH2CH2-SS-CH2CH2CH3, CH3CH2CH2-SSS-CH2CH2CH3, CH3-SS-CH2CH3, CH3-SSS-CH2CH3, CH3-SS-CH2CH2CH3, CH3-SSSS-CH2CH2CH3, or CH3-SSS-CH3.

21. The electrolyte according to any one of claims 17-20, characterized in that, The first electrolyte further includes a first solvent, which comprises one or more of the following: 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, pentaethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, 1,3-dioxopentane, or dimethyl ether.

22. The electrolyte according to any one of claims 17-21, characterized in that, In the first electrolyte, the molar concentration of the sulfide is 1 mol / L to 10 mol / L.

23. The electrolyte according to any one of claims 17-22, characterized in that, In the second electrolyte, the molar concentration of the electrolyte salt is greater than or equal to 5 mol / L.

24. The electrolyte according to any one of claims 17-23, characterized in that, In the second electrolyte, the molar concentration of the electrolyte salt is 5 mol / L-10 mol / L.

25. The electrolyte according to any one of claims 17-24, characterized in that, The electrolyte salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, or lithium tetrafluorooxalate phosphate.

26. The electrolyte according to any one of claims 17-25, characterized in that, The solvent includes one or more of 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, pentaethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, 1,3-dioxopentane, or dimethyl ether.

27. The electrolyte according to any one of claims 17-26, characterized in that, The second electrolyte further includes a diluent, which includes one or more of 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, or 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether.

28. The electrolyte according to any one of claims 17-27, characterized in that, In the electrolyte, the volume ratio of the first electrolyte to the second electrolyte is (5:95)-(30:70).

29. An electrical appliance, characterized in that, The lithium-sulfur battery includes any one of claims 1-16.

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