Lithium-sulfur battery

Abstract

The invention belongs to the technical field of lithium-sulfur batteries, and relates to a lithium-sulfur battery, an electrolyte of the lithium-sulfur battery comprises cyanide-containing lithium salt and chlorine-containing Lewis acid, and a positive electrode is mainly composed of a positive electrode current collector and an elemental sulfur-containing conductive coating on the surface of the positive electrode current collector, or is directly composed of an elemental sulfur-containing material. According to the lithium-sulfur battery, based on an S / SCl4 positive electrode chemical reaction, a high-valence sulfur redox process of 32 electron transfer is realized, a 16 electron transfer mechanism of a traditional lithium-sulfur battery is far superior, the average discharge voltage of the battery can reach 3.52 V, the specific discharge capacity can reach 1761 mAh g <-1 >, and the lithium-sulfur battery is remarkably superior to a traditional system. In addition, the battery can be selectively provided with a non-negative electrode structure, the negative electrode can be completely prevented from using lithium metal in the preparation process, and the preparation and use safety of the battery is greatly improved. The invention opens up a brand new path for finding and breaking through the voltage, specific energy and safety bottlenecks of the traditional lithium-sulfur battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium-sulfur batteries, and relates to a lithium-sulfur battery. 0 / S 4+ The positive electrode reaction is specifically a 32-electron conversion reaction between S8 and SCl4 , and can be applied to the field of energy storage. BACKGROUND

[0002] Due to the extremely rich sulfur resources and a theoretical specific capacity as high as 1675 mAh g -1 , lithium-sulfur batteries are widely considered as a strong candidate for the next generation of high specific energy storage technology. However, the discharge voltage of traditional lithium-sulfur batteries is generally lower than 2.4 V, and the negative electrode side excessively uses lithium metal, which greatly hinders the industrial application of lithium-sulfur batteries.

[0003] Sulfur element has rich valence states such as -2, 0, +1, +2, +4, and +6. Traditional lithium-sulfur batteries are all based on low-valence reaction paths from 0 to -2, which makes it difficult to improve the corresponding discharge potential, and the initial reduction reaction requires the use of lithium metal for the negative electrode to balance the full battery reaction, so it is inevitable to use a large amount of lithium metal. If the oxidation process of sulfur element is used to form high-valence sulfur compounds, it is expected to improve the discharge potential to 3.7 V, and the negative electrode does not use any lithium metal. In addition, the high-valence oxidation reaction of sulfur shows a theoretical capacity much higher than the reduction reaction (for example, the theoretical capacity of the oxidation reaction from 0 to +4 is 3350 mAh g -1 ), and the super-high energy density is expected to be realized by superimposing high discharge voltage. However, due to the need to overcome a very high reaction energy barrier in the oxidation process of sulfur, and the need for corresponding anion groups for coordination, and the need to reasonably match the positive electrode and negative electrode reactions, it is difficult to realize lithium-sulfur batteries based on high-valence reactions of sulfur so far. SUMMARY

[0004] In view of the deficiencies in the prior art described above, the application provides a lithium-sulfur battery based on S / SCl4 positive electrode chemical reaction, which realizes a high-valence sulfur oxidation-reduction process of 32-electron transfer, far exceeding the 16-electron transfer mechanism of traditional lithium-sulfur batteries. The battery can have an average discharge voltage as high as 3.52 V, and a discharge specific capacity of up to 1761 mAh g -1 , which is significantly better than the traditional system with a discharge voltage of only about 2.2 V and a capacity of 1400-1640 mAh g -1 . In addition, the battery can have a negative electrode-free structure, which can completely avoid the use of lithium metal in the negative electrode during preparation, greatly improving the safety of the battery during preparation and use. The application opens up a new path for breaking through the voltage, specific energy, and safety bottlenecks of traditional lithium-sulfur batteries.

[0005] To achieve the above object, the present application is implemented by the technical scheme of the following technical measures.

[0006] The present application provides a lithium-sulfur battery, whose electrolyte comprises a lithium salt containing cyanide and a Lewis acid containing chlorine, the molar concentration of the Lewis acid containing chlorine in the solvent is 2-13 mol / L, and the lithium salt containing cyanide is 80-100% of the saturated amount of dissolution in the solvent and has a molar concentration of at least 1 mol / L;

[0007] The positive electrode is mainly composed of a positive electrode current collector and a conductive coating containing elemental sulfur on the surface of the positive electrode current collector, or is directly composed of a material containing elemental sulfur.

[0008] In this context, the lithium salt containing cyanide is a lithium salt having cyanide (-C≡N); generally, the lithium salt containing cyanide is selected from known compounds that are commercially available or can be synthesized based on existing technical literature, for example, including but not limited to lithium dicyanamide, lithium butyrate, lithium 4,5-dicyano-2-(trifluoromethyl)imidazole; further based on experimental evidence, lithium dicyanamide is the most preferred;

[0009] The chemical formula of the lithium butyrate is CLiN, and the CAS is 2408-36-8;

[0010] The chemical formula of the lithium 4,5-dicyano-2-(trifluoromethyl)imidazole is C6F3LiN4, and the CAS is 761441-54-7;

[0011] The chemical formula of the lithium dicyanamide (LiDCA) is C2N3Li, which is a known compound in the art, and those skilled in the art can refer to relevant recorded documents or common knowledge to prepare and obtain it themselves. For example, lithium dicyanamide can be synthesized as recorded in patent document CN1449069A. In order to better illustrate the present application, the present application also provides a reference preparation method of lithium dicyanamide:

[0012] Dissolve 15.31 g of silver nitrate in 50 ml of water, and add it dropwise to an aqueous solution of sodium dicyanamide (0.095 mol in 50 ml of water) under continuous stirring, and the dropwise process lasts for 1 hour; the white precipitate generated in the reaction is filtered and washed with water, and the obtained solid product after washing is suspended in 60 ml of water, and then an aqueous solution of lithium bromide (0.075 mol in 25 ml of water) is added dropwise, and after stirring at 40 ℃ for 2 hours, silver bromide and excess silver dicyanamide are removed by filtration, and the filtrate is collected and concentrated by rotary evaporation to obtain white hygroscopic crystal product; the crystal product is repeatedly washed with anhydrous ether, filtered under argon atmosphere, dried at 60 ℃ for 12 hours, and finally dried at 100 ℃ for 24 hours under vacuum to obtain lithium dicyanamide.

[0013] In the present disclosure, the chlorine-containing Lewis acid is a Lewis acid containing chloride ions, which is a conventional electrolyte salt selection in the field of batteries. Those skilled in the art can select appropriate chlorine-containing Lewis acids from the Lewis acids described in the prior art.

[0014] To better illustrate the present application, and to provide a technical solution for reference, the chlorine-containing Lewis acid selection includes at least one of aluminum chloride, gallium chloride, iron chloride, and zinc chloride.

[0015] In the present disclosure, the electrolyte includes a lithium cyanide-containing salt and a chlorine-containing Lewis acid. The electrolyte can be composed of a lithium cyanide-containing salt and a chlorine-containing Lewis acid, or the electrolyte can be composed of a lithium cyanide-containing salt, a chlorine-containing Lewis acid, and other conventional electrolytes.

[0016] In one preferred technical solution, to further enhance the synergistic effect of the components of the electrolyte, Li + -DCA - To promote the positive electrode reaction and optimize the negative electrode interface to achieve reversible cycling, the electrolyte further includes ethoxy aluminum (AE, CAS: 555-75-9); the molar concentration of ethoxy aluminum in the solvent can be referred to the relevant literature of ethoxy aluminum as an electrolyte, for example, 1-6 mol / L.

[0017] In the present disclosure, the lithium-sulfur battery can be a liquid lithium-sulfur battery or a solid-state lithium-sulfur battery.

[0018] The liquid lithium-sulfur battery is a lithium-sulfur battery using a liquid electrolyte, which is mainly composed of a lithium cyanide-containing salt and a chlorine-containing Lewis acid dissolved in a solvent as an electrolyte; the solvent can be selected from conventional electrolyte solvents, preferably chloro-based electrolyte solvents.

[0019] To better illustrate the present application, and to provide a technical solution for reference, the solvent preferably includes any one of thionyl chloride (SOCl2) and sulfuryl chloride (SO2Cl2); more preferably, the solvent is thionyl chloride.

[0020] Preferably, the liquid electrolyte further includes other conventional electrolyte additives / additives or conventional electrolyte additives / additives inherent in conventional commercial chloro-based electrolyte compositions, especially functional additives, which can be selected by those skilled in the art according to the functional requirements. It should be emphasized that the liquid electrolyte in the technical solution of the present application can or can not be added with other conventional electrolyte additives / additives.

[0021] In one preferred embodiment, the liquid electrolyte further comprises pentafluorobenzene (PFB, CAS: 363-72-4) as an additive; the amount of pentafluorobenzene added in the solvent can refer to the relevant literature on the use of pentafluorobenzene as an additive, for example, no more than 1000 µL of pentafluorobenzene is added per 1 mL of solvent.

[0022] It should be noted that the solubility of the lithium salt containing cyanide (especially lithium dicyanamide) in the solvent generally changes with the molar concentration of the Lewis acid containing chlorine, and the lithium salt containing cyanide is difficult to dissolve in the solvent under normal conditions without the addition of the Lewis acid containing chlorine, so the Lewis acid containing chlorine is a necessary electrolyte.

[0023] To better illustrate the present application, and to provide a preferred technical solution for reference, when the Lewis acid containing chlorine is aluminum chloride and the lithium salt containing cyanide is lithium dicyanamide, the molar ratio of aluminum chloride to lithium dicyanamide can be selected from 2:1, 2:1.2, 4:2.3, 8:4.5, 10:5.7, or 13:7.4, etc.

[0024] The solid-state lithium-sulfur battery is a lithium-sulfur battery using a solid-state electrolyte, which is mainly composed of a lithium salt containing cyanide, a Lewis acid containing chlorine as an electrolyte dissolved in a solvent, and a solid or colloidal small molecule polymer material added for compounding; the solid or colloidal small molecule polymer material is selected according to conventional solid-state batteries.

[0025] To better illustrate the present application, and to provide a preferred technical solution for reference, the solid or colloidal small molecule polymer material is selected to include 3,3-bis(chloromethyl)oxetane. The ratio of the lithium salt containing cyanide, the Lewis acid containing chlorine, the solvent, and the solid or colloidal small molecule polymer material can refer to conventional solid-state batteries. For example, the liquid electrolyte can be prepared according to the above description, and then the solid or colloidal small molecule polymer material is added to the liquid electrolyte and mixed uniformly to obtain the solid-state electrolyte; the volume ratio of the liquid electrolyte to the solid or colloidal small molecule polymer material is (2-10):1.

[0026] In this context, based on the common knowledge of lithium metal batteries or lithium ion batteries in the prior art, the lithium-sulfur battery further includes a negative electrode and / or a negative electrode current collector, and the material selection, material ratio, and preparation process of the negative electrode and / or negative electrode current collector all follow the conventional lithium metal battery or lithium ion battery process, preferably referring to the use of a negative electrode current collector only in the negative electrode lithium metal battery; those skilled in the art can select appropriate processes based on the prior art to prepare the lithium-sulfur battery according to the conventional preparation process of the lithium metal battery or the lithium ion battery or the required battery type.

[0027] For better illustrating the present application, and exemplifying the lithium-sulfur battery provided by the present application, specifically, the lithium-sulfur battery is mainly composed of a positive electrode, the liquid electrolyte or the solid electrolyte, and a negative electrode and / or a negative electrode current collector;

[0028] The positive electrode is one of the components commonly known in the art of batteries. In the present application, the positive electrode can be directly used as the positive electrode of a conventional sulfur-based battery, or a positive electrode described in the present application. Specifically, the positive electrode is mainly composed of a positive electrode current collector and a sulfur-containing conductive coating on the surface of the positive electrode current collector, or is directly composed of a sulfur-containing material. Specifically, the positive electrode is mainly composed of a positive electrode current collector and a sulfur-containing conductive coating on the surface of the positive electrode current collector, wherein the sulfur-containing conductive coating is formed by mixing and coating the surface of the positive electrode current collector with raw components including a carbon-based material for conductive coating, sulfur powder, and a binder; or the positive electrode is directly composed of a sulfur-containing material, which is formed by mixing and curing raw components including a carbon-based material for conductive coating, sulfur powder, and a binder.

[0029] Further, the carbon-based material for conductive coating is selected from at least one of Ketjenblack, graphite, conductive carbon black, carbon nanotube, and activated carbon.

[0030] The binder is selected from any one of a water-based binder and a non-water-based binder. The water-based binder is a conventional water-based binder described in the prior art and suitable for use in the positive electrode of a battery. In use, water is used as the main solvent, for example, any one of sodium carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), sodium alginate, polyacrylic acid, polyacrylate (such as LA133), natural polymer (such as chitosan, starch, etc.), and conductive polymer (such as PEDOT:PSS). The non-water-based binder is a conventional non-water-based binder described in the prior art and suitable for use in the positive electrode of a battery. In use, a conventional organic reagent (for example, N-methyl pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), tetrahydrofuran (THF), acetone, cyclohexanone, chloroform, dichloromethane, ethyl acetate, ethanol) is used as the main solvent, for example, any one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyurethane (PU), and epoxy resin.

[0031] The positive electrode current collector is selected from any one of foamed copper, copper foil, nickel foil, foamed nickel, stainless steel foil, aluminum foil, carbon-coated aluminum foil, foamed aluminum, titanium foil, carbon-based material, and metal-organic polymer composite.

[0032] Generally, the mass percentage of elemental sulfur (sulfur powder) in the elemental sulfur-containing conductive coating and the elemental sulfur-containing material can refer to the positive electrode material ratio of a conventional sulfur-based battery. To better illustrate the present application, a preferred technical solution is provided, wherein the mass percentage of elemental sulfur in the elemental sulfur-containing conductive coating and the elemental sulfur-containing material is 30-60 wt%. The ratio of the remaining carbon-based materials for the conductive coating and the binder all follow the preparation of the positive electrode of a conventional sulfur-based battery.

[0033] The negative electrode and / or negative electrode current collector are one of the components commonly known in the art of batteries. In the negative electrode-free lithium-sulfur battery, only the negative electrode current collector is used. The negative electrode and / or negative electrode current collector can be directly obtained from the market or can be prepared according to the prior art documents and conventional processes of lithium metal batteries or lithium ion batteries in the art. For example, the negative electrode can be directly made of elemental lithium metal, or can be directly made of a conventional carbon-containing material negative electrode or an alloy negative electrode. For another example, the negative electrode is formed by loading a lithium foil on the surface of a negative electrode current collector.

[0034] Further, the negative electrode current collector can be selected from any one of a copper foil, a nickel foil, a nickel foam, a stainless steel foil, an aluminum foil, a carbon-coated aluminum foil, an aluminum foam, a titanium foil, a carbon-based material, and a metal-organic polymer composite.

[0035] The process for loading the lithium foil on the surface of the negative electrode current collector can include any one of direct calendering, electrochemical deposition, mechanical coating, and melt impregnation.

[0036] Based on the common knowledge of batteries in the prior art, the lithium-sulfur battery can further include a conventional negative electrode shell, a gasket, a spring, a separator loaded with electrolyte, a positive electrode shell, and other conventional structures / components, and a person skilled in the art can select appropriate processes to prepare the lithium-sulfur battery based on the prior art according to the conventional preparation process of lithium metal batteries or lithium ion batteries or the required battery type.

[0037] Further, based on the common knowledge of lithium metal batteries or lithium ion batteries in the prior art, in addition to the technical content described above, the specifications and assembly ratios of the positive electrode, the liquid electrolyte or the solid electrolyte, the negative electrode and / or the negative electrode current collector all follow the conventional lithium metal battery or lithium ion battery process. A person skilled in the art can select appropriate processes to prepare the lithium-sulfur battery product based on the prior art according to the conventional preparation process of lithium metal batteries or lithium ion batteries or the required battery model. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1The schematic diagram and charge-discharge curve summary diagram of the negative electrode-free lithium-sulfur battery based on S / SCl4 redox reaction of embodiment 4 of the present application and the conventional lithium-sulfur battery based on S / Li2S redox chemistry of comparative example 2 are shown in the following figure. The left figure is a schematic diagram of the structure of the battery of embodiment 4 and comparative example 2, the middle figure is a schematic diagram of the positive electrode chemical reaction of the battery of embodiment 4 and comparative example 2, and the right figure is a comparison diagram of the charge-discharge curves of the battery of embodiment 4 and comparative example 2.

[0039] Figure 2 The cycle performance comparison and constant current charge-discharge curve diagram of the batteries of comparative example 1, comparative example 3, embodiment 1 and embodiment 4 of the present application are shown in the following figure. The figure a is a cycle performance comparison diagram of the batteries of comparative example 1, embodiment 1 and embodiment 4 under the condition of using different electrolytes; the figure b is a constant current charge-discharge curve diagram of the batteries of comparative example 3 and embodiment 4 in the control experiment of containing sulfur and not containing sulfur in the positive electrode.

[0040] Figure 3 The S 2p XPS spectra of the S positive electrode in the initial preparation state, the charged state (800 mAh g -1 ) and the fully discharged state of the negative electrode-free lithium-sulfur button cell of embodiment 4 of the present application are shown in the following figure.

[0041] Figure 4 The analysis results of the liquid electrolytes used in comparative example 1, embodiment 1, embodiment 3 and embodiment 4 of the present application are shown in the following figure. The figure a is the 27 Al nuclear magnetic resonance spectrum comparison diagram of AS electrolyte, DCA-AS electrolyte and AE-DCA-AS electrolyte; the figure b is the infrared spectrum diagram of AS electrolyte, DCA-AS electrolyte, AE-DCA-AS electrolyte, pure AE and pure LiDCA; the figure c is the 7 Li nuclear magnetic resonance spectrum comparison diagram of AE-DCA-AS electrolyte and PFB-AE-DCA-AS electrolyte.

[0042] Figure 5 The electrochemical performance summary diagram of the Li||Ni half-batteries using different electrolytes in verification examples 1-3 of the present application is shown in the following figure. The figure a is a cycle performance comparison diagram of the Li||Ni half-batteries in verification examples 1-3; the figure b is a charge-discharge curve comparison diagram of the Li||Ni half-batteries in verification examples 1-3 under the condition of 1 mA cm -2 current density; the figure c is a charge-discharge curve comparison diagram of the Li||Ni half-batteries in verification examples 1-3 under the condition of 1 mAh cm -2 capacity.

[0043] Figure 6Figure 1 is a summary chart of the negative electrode interface composition analysis of the batteries of Example 1, Example 3, and Example 4 using different liquid electrolytes. Figure 1a is the F 1s XPS spectrum of the negative electrode interface of the batteries of Example 1, Example 3, and Example 4; Figure 1b is the O 1s XPS spectrum of the negative electrode interface of the batteries of Example 1, Example 3, and Example 4; and Figure 1c is the N 1s XPS spectrum of the negative electrode interface of the batteries of Example 1, Example 3, and Example 4.

[0044] Figure 7 Figure 2 is a constant current charge-discharge curve of the lithium-sulfur button cell provided in Example 5. The charge capacity is 250 mAh / g, and the current density is 0.5 A / g.

[0045] Figure 8 Figure 3 is a constant current charge-discharge curve of the lithium-sulfur button cell provided in Example 6. The charge capacity is 250 mAh / g, and the current density is 0.5 A / g.

[0046] Figure 9 Figure 4 is a constant current charge-discharge curve of the lithium-sulfur button cell provided in Example 8. The charge capacity is 200 mAh / g, and the current density is 1 A / g.

[0047] Figure 10 Figure 5 is a constant current charge-discharge curve of the lithium-sulfur button cell provided in Example 9. The charge capacity is 800 mAh / g, and the current density is 0.5 A / g. DETAILED DESCRIPTION

[0048] In order to further understand the present application, the preferred embodiments of the present application will be described in conjunction with the examples below, but it should be understood that these descriptions are only intended to further illustrate the features and advantages of the present application, and are not intended to limit the scope of the claims of the present application. Those skilled in the art can modify the process parameters according to the content herein, and implement the present application. It should be particularly pointed out that all similar replacements and modifications are obvious to those skilled in the art, and are considered to be included in the present application. The methods and applications of the present application have been described by the preferred embodiments, and those skilled in the art can obviously modify or appropriately change and combine the methods and applications described herein, to implement and apply the present application technology. Although the following terms are believed to be well understood by those skilled in the art, the following definitions are set forth to facilitate the understanding of the subject matter disclosed herein.

[0049] The application provides a lithium-sulfur battery, an electrolyte of which comprises a lithium salt containing cyanide and a Lewis acid containing chlorine, the molar concentration of the Lewis acid containing chlorine in the solvent is 2-13 mol / L, and the lithium salt containing cyanide is 80-100% of the saturated amount of dissolution in the solvent and has a molar concentration of at least 1 mol / L;

[0050] The positive electrode is mainly composed of a positive electrode current collector and a conductive coating containing elemental sulfur on the surface of the positive electrode current collector, or is directly composed of a material containing elemental sulfur.

[0051] In the present application, the lithium salt containing cyanide is a lithium salt containing cyanide (-C≡N); generally, the lithium salt containing cyanide is selected from known compounds available on the market or synthesized based on prior art documents, and in one embodiment, for example, includes but is not limited to lithium dicyanamide, lithium butyrate, lithium 4,5-dicyano-2-(trifluoromethyl)imidazole; further based on experimental evidence, lithium dicyanamide is the most preferred.

[0052] The lithium butyrate has a chemical formula of CLiN and a CAS of 2408-36-8.

[0053] The lithium 4,5-dicyano-2-(trifluoromethyl)imidazole has a chemical formula of C6F3LiN4 and a CAS of 761441-54-7.

[0054] The lithium dicyanamide (LiDCA) has a chemical formula of C2N3Li and is a known compound in the art, and a person skilled in the art can refer to relevant documents or common knowledge to prepare and obtain it by himself / herself. For example, the lithium dicyanamide can be synthesized according to the patent document CN1449069A. In order to better illustrate the present application, the present application also provides a preparation method of lithium dicyanamide for reference:

[0055] 15.31 g of silver nitrate is dissolved in 50 ml of water, and then added dropwise into an aqueous solution of sodium dicyanamide (0.095 mol dissolved in 50 ml of water) under continuous stirring, and the dropwise process lasts for 1 hour; the white precipitate generated in the reaction is filtered and washed with water, and then the obtained solid product after washing is suspended in 60 ml of water, and then an aqueous solution of lithium bromide (0.075 mol dissolved in 25 ml of water) is added dropwise, and after stirring at 40 ℃ for 2 hours, silver bromide and excess silver dicyanamide are removed by filtration, and the filtrate is collected and concentrated by rotary evaporation to obtain white hygroscopic crystal product; the crystal product is repeatedly washed with anhydrous ether, filtered under an argon atmosphere, dried at 60 ℃ for 12 hours, and finally dried at 100 ℃ for 24 hours under vacuum to obtain lithium dicyanamide.

[0056] In the present disclosure, the chlorine-containing Lewis acid is a Lewis acid containing chloride ions, which is a conventional electrolyte salt selection in the field of batteries. Those skilled in the art can select appropriate chlorine-containing Lewis acids from the Lewis acids described in the prior art.

[0057] To better illustrate the present disclosure and provide a reference for the embodiments, the chlorine-containing Lewis acid selection includes at least one of aluminum chloride, gallium chloride, iron chloride, and zinc chloride.

[0058] In one embodiment, the molar concentration of the chlorine-containing Lewis acid in the solvent is 2-13 mol / L, such as 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L, 8 mol / L, 8.5 mol / L, 9 mol / L, 9.5 mol / L, 10 mol / L, 10.5 mol / L, 11 mol / L, 11.5 mol / L, 12 mol / L, 12.5 mol / L, 13 mol / L, or any range or point value therebetween.

[0059] In the present disclosure, the electrolyte includes a lithium cyanide-containing salt and a chlorine-containing Lewis acid, which can be an electrolyte composed of a lithium cyanide-containing salt and a chlorine-containing Lewis acid. In one embodiment, the electrolyte can also be composed of a lithium cyanide-containing salt, a chlorine-containing Lewis acid, and other conventional electrolytes.

[0060] In one preferred embodiment, to further enhance the synergistic effect of the components of the electrolyte, Li + -DCA - Coordination to promote positive electrode reactions and optimize negative electrode interfaces for reversible cycling, the electrolyte further includes aluminum ethoxide (AE, CAS: 555-75-9); the molar concentration of aluminum ethoxide in the solvent can be referred to the relevant literature for its use as an electrolyte, for example, 1-6 mol / L, such as 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, or any range or point value therebetween.

[0061] In the present disclosure, the lithium-sulfur battery can be a liquid lithium-sulfur battery or a solid-state lithium-sulfur battery.

[0062] The liquid lithium-sulfur battery is a lithium-sulfur battery using a liquid electrolyte, and the liquid electrolyte is mainly composed of a lithium salt containing cyanide, a Lewis acid containing chlorine as an electrolyte dissolved in a solvent. In one embodiment, the solvent can be selected from conventional electrolyte solvents, preferably chlorine-based electrolyte solvents.

[0063] To better illustrate the present application, and to provide an embodiment for reference, the solvent preferably includes any one of thionyl chloride (SOCl2) and sulfuryl chloride (SO2Cl2); more preferably, the solvent is thionyl chloride.

[0064] Preferably, the liquid electrolyte further includes other conventional electrolyte auxiliaries / additives or conventional electrolyte auxiliaries / additives inherent in conventional commercial chlorine-based electrolyte compositions, especially functional additives, which can be selected by those skilled in the art according to the required functional requirements. It should be emphasized that the liquid electrolyte in the technical solution of the present application can or can not be added with other conventional electrolyte auxiliaries / additives.

[0065] In one preferred embodiment, the liquid electrolyte further includes pentafluorobenzene (PFB, CAS: 363-72-4) as an additive; the amount of pentafluorobenzene added in the solvent can refer to the relevant literature records of pentafluorobenzene as an additive, for example, not more than 1000 µL of pentafluorobenzene is added per 1 mL of solvent, such as 100 µL, 200 µL, 300 µL, 400 µL, 500 µL, 600 µL, 700 µL, 800 µL, 900 µL, 1000 µL or any range or point value therebetween.

[0066] It should be noted that the solubility of the lithium salt containing cyanide (especially lithium dicyanamide) in the solvent changes with the molar concentration of the Lewis acid containing chlorine. Without the addition of the Lewis acid containing chlorine, the lithium salt containing cyanide is difficult to dissolve in the solvent under normal conditions, so the Lewis acid containing chlorine is an essential electrolyte. In one embodiment, the lithium salt containing cyanide is 80-100% of the saturated amount of the solvent, for example, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100% or any range or point value therebetween.

[0067] For better illustrating the present application, and providing a preferred embodiment for reference, when the chlorine-containing Lewis acid is aluminum chloride, and the cyanide-containing lithium salt is lithium dicyanamide, the molar ratio of aluminum chloride and lithium dicyanamide can be selected from 2:1, 2:1.2, 4:2.3, 8:4.5, 10:5.7, 13:7.4, and the like.

[0068] The solid-state lithium-sulfur battery is a lithium-sulfur battery using a solid-state electrolyte, which is mainly composed of a solvent in which a cyanide-containing lithium salt and a chlorine-containing Lewis acid are dissolved as an electrolyte, and a solid or gel small molecule polymer material added for compounding; the solid or gel small molecule polymer material is selected according to a conventional solid-state battery.

[0069] For better illustrating the present application, and providing a preferred embodiment for reference, the solid or gel small molecule polymer material is selected from 3,3-bis(chloromethyl)oxetane. The ratio of the cyanide-containing lithium salt, the chlorine-containing Lewis acid, the solvent, and the solid or gel small molecule polymer material can be selected according to a conventional solid-state battery. In one embodiment, the solid or gel small molecule polymer material is added to the liquid electrolyte prepared according to the above-mentioned liquid electrolyte, and mixed uniformly to obtain a solid-state electrolyte; the volume ratio of the liquid electrolyte to the solid or gel small molecule polymer material is (2-10):1, for example, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, or any range or point value therebetween.

[0070] In this context, based on the common knowledge of lithium metal batteries or lithium ion batteries in the prior art, the lithium-sulfur battery also includes a negative electrode and / or a negative electrode current collector, and the material selection, material ratio, and preparation process of the negative electrode and / or the negative electrode current collector all follow the conventional lithium metal battery or lithium ion battery process, preferably referring to the negative electrode current collector used in the negative electrode-free lithium metal battery; those skilled in the art can select appropriate processes based on the prior art to prepare the lithium-sulfur battery according to the conventional preparation process of the lithium metal battery or the lithium ion battery or the required battery type.

[0071] For better illustrating the present application, and providing an example of the lithium-sulfur battery provided by the present application, specifically, the lithium-sulfur battery is mainly composed of a positive electrode, the above-mentioned liquid electrolyte or the above-mentioned solid-state electrolyte, and a negative electrode and / or a negative electrode current collector;

[0072] The positive electrode is one of the components known in the art of batteries. The positive electrode used in the present application can directly use the positive electrode of a conventional sulfur-based battery or use the positive electrode described in the present application. The positive electrode is mainly composed of a positive electrode current collector and a sulfur-containing conductive coating on the surface thereof or is directly composed of a sulfur-containing material. Specifically, the positive electrode is mainly composed of a positive electrode current collector and a sulfur-containing conductive coating on the surface thereof, and the sulfur-containing conductive coating is formed by mixing and coating carbon-based materials for conductive coating, sulfur powder, and a binder as raw material components on the surface of the positive electrode current collector. Alternatively, the positive electrode is directly composed of a sulfur-containing material, which is formed by mixing and curing carbon-based materials for conductive coating, sulfur powder, and a binder as raw material components.

[0073] Further, in one embodiment, the carbon-based material for conductive coating is selected from at least one of Ketjen black, graphite, conductive carbon black, carbon nanotube, and activated carbon.

[0074] In one embodiment, the binder is selected from any one of a water-based binder and a non-water-based binder. The water-based binder is a conventional water-based binder described in the art and applicable to a positive electrode of a battery. In use, water is used as a main solvent, and for example, any one of sodium carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), sodium alginate, polyacrylic acid, polyacrylate (e.g., LA133), natural polymer (e.g., chitosan, starch, etc.), and conductive polymer (e.g., PEDOT:PSS) is used. The non-water-based binder is a conventional non-water-based binder described in the art and applicable to a positive electrode of a battery. In use, a conventional organic reagent (e.g., N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), tetrahydrofuran (THF), acetone, cyclohexanone, chloroform, dichloromethane, ethyl acetate, ethanol) is used as a main solvent, and for example, any one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyurethane (PU), and epoxy resin is used.

[0075] In one embodiment, the positive electrode current collector is selected from any one of foamed copper, copper foil, nickel foil, foamed nickel, stainless steel foil, aluminum foil, carbon-coated aluminum foil, foamed aluminum, titanium foil, carbon-based material, and metal-organic polymer composite.

[0076] Generally, the elemental sulfur (sulfur powder) mass percentage in the elemental sulfur-containing conductive coating and the elemental sulfur-containing material can refer to the positive electrode material ratio of a conventional sulfur-based battery. To better illustrate the present application, and to provide a preferred embodiment for reference, the elemental sulfur mass percentage in the elemental sulfur-containing conductive coating and the elemental sulfur-containing material is 30-60 wt%, for example, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, 46 wt%, 47 wt%, 48 wt%, 49 wt%, 50 wt%, 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt%, 60 wt%, or any range or point value therebetween. The remaining ratio of the carbon-based material and the binder for the conductive coating all follow the preparation of the positive electrode of the conventional sulfur-based battery.

[0077] The negative electrode and / or the negative current collector are one of the components known in the art of batteries. In the lithium-sulfur battery without a negative electrode, only the negative current collector is used. The negative electrode and / or the negative current collector can be directly obtained from the market or can be prepared according to the prior art documents and conventional processes in the art of lithium metal batteries or lithium ion batteries. For example, the negative electrode can be directly made of elemental lithium metal, or can be directly made of a conventional carbon-containing material negative electrode or an alloy negative electrode. For another example, the negative electrode is formed by loading a lithium foil on the surface of a negative current collector.

[0078] Further, in one embodiment, the negative current collector is selected from any one of a copper foil, a nickel foil, a nickel foam, a stainless steel foil, an aluminum foil, a carbon-coated aluminum foil, an aluminum foam, a titanium foil, a carbon-based material, and a metal-organic polymer composite.

[0079] In one embodiment, the process for loading the lithium foil on the surface of the negative current collector includes any one of direct calendering, electrochemical deposition, mechanical coating, and melt impregnation.

[0080] Based on the prior art knowledge of batteries, in one embodiment, the lithium-sulfur battery can further include a conventional negative electrode shell, a gasket, a spring, a separator loaded with electrolyte, a positive electrode shell, and other conventional structures / components, which can be selected by a person skilled in the art according to the conventional preparation process of lithium metal batteries or lithium ion batteries or the required battery type, and based on the prior art to prepare the lithium-sulfur battery.

[0081] Further, based on the common knowledge in the prior art of lithium metal batteries or lithium ion batteries, in addition to the technical contents recorded in the above, the specifications of the positive electrode, the liquid electrolyte or the solid electrolyte, the negative electrode and / or the negative electrode current collector, and the assembly ratio all follow the conventional lithium metal battery or lithium ion battery process. Those skilled in the art can select appropriate processes to prepare the lithium-sulfur battery product based on the prior art according to the conventional preparation process of the lithium metal battery or the lithium ion battery or the required battery model.

[0082] The present application will be further explained in detail with reference to the following examples. However, those skilled in the art will understand that the examples are provided only for illustrative purposes, and are not intended to limit the scope of the present application.

[0083] Examples

[0084] The embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will understand that the following examples are only for the purpose of illustration, and should not be regarded as limiting the scope of the present application. If no specific conditions are specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If no manufacturer of the reagent or instrument is specified, it is a conventional product that can be obtained by purchase on the market. The present application should not be interpreted as being limited to the specific examples described.

[0085] Example 1

[0086] In this example, an anode-free lithium-sulfur button cell was assembled as a test sample.

[0087] Liquid electrolyte: The liquid electrolyte was prepared in an argon glove box with water and oxygen content less than 1 ppm; 1.067 g (8 mmol) of AlCl3 was weighed into 1 mL of SOCl2 and stirred for 0.5 hours until completely dissolved, then 0.329 g (4.5 mmol) of lithium dicyanamide (LiDCA) was added and stirred for another 0.5 hours until completely dissolved, to prepare the liquid electrolyte, which is denoted as DCA-AS electrolyte.

[0088] S positive electrode: 45 wt% sulfur powder, 45 wt% Ketjen black and 10 wt% PTFE (60 wt% aqueous dispersion) were mixed in ethanol with a solid to ethanol mass ratio of 20:1. After uniform dispersion, the obtained sulfur-containing slurry was slowly (80 μL each time) dropped onto the nickel foam suspended on a hot plate at 100 °C, with an interval of about 5 min between each drop to ensure sufficient evaporation of ethanol, and the process was repeated until the target loading was reached. Finally, vacuum drying was performed at 70 °C overnight, the sample was flattened using a rolling machine and weighed. The sulfur loading of the button cell was 1.0-1.2 mg / cm 2 .

[0089] The battery assembly was performed in an argon-filled glove box (water and oxygen content less than 1 ppm). The anode-free lithium-sulfur button cell (2032 type) was assembled using the above liquid electrolyte, S cathode and nickel foil, glass fiber separator (GF / D, 675 μm thick, Whatman). The diameters of the S cathode and nickel foil were 14 mm and 16 mm, respectively. The liquid electrolyte was 120 μL.

[0090] Verification Example 1

[0091] In this verification example, Li||Ni half-batteries were assembled as test samples.

[0092] Liquid electrolyte: The liquid electrolyte was prepared in an argon-protected glove box with water and oxygen content less than 1 ppm; 1.067 g (8 mmol) of AlCl3 was weighed into 1 mL of SOCl2 and stirred for 0.5 hours until completely dissolved, then 0.329 g (4.5 mmol) of lithium dicyanamide (LiDCA) was added and stirred for 0.5 hours until completely dissolved, to prepare the liquid electrolyte, which was denoted as DCA-AS electrolyte.

[0093] The battery assembly was performed in an argon-filled glove box (water and oxygen content less than 1 ppm). The Li||Ni half-batteries were assembled using the above liquid electrolyte, lithium foil, nickel foil and glass fiber separator (GF / D, 675 μm thick, Whatman). The nickel foil with a diameter of 14 mm was paired with a lithium foil anode with a diameter of 14 mm. The liquid electrolyte was 150 μL.

[0094] Example 2

[0095] In this example, anode-free lithium-sulfur button cells were assembled as test samples.

[0096] Liquid electrolyte: The liquid electrolyte was prepared in an argon-protected glove box with water and oxygen content less than 1 ppm; 1.067 g (8 mmol) of AlCl3 was weighed into 1 mL of SOCl2 and stirred for 0.5 hours until completely dissolved, then 0.486 g (3 mmol) of ethoxyaluminum (AE) was added and stirred for 0.5 hours until completely dissolved, then 0.329 g (4.5 mmol) of lithium dicyanamide (LiDCA) was added and stirred for 0.5 hours until completely dissolved, and finally 800 μL of pentafluorobenzene (PFB) was added and stirred for 10 minutes until completely dissolved, to prepare the liquid electrolyte, which was denoted as PFB-AE-DCA-AS electrolyte.

[0097] S positive electrode: Ketjen black, sulfur powder and PTFE powder were mixed by ball milling with a mass ratio of 47.5:47.5:5, and grinded in a mortar for 5 min to form agglomerates, then pressed into self-standing electrodes by a roller press machine (MSK-2150, MTI). The sulfur loading of the coin cell was 3.80~5.60 mg / cm 2 .

[0098] The battery assembly was carried out in an argon-filled glove box (water and oxygen content less than 1 ppm). The anode-free lithium-sulfur coin cell (2032 type) was assembled using the above liquid electrolyte, S positive electrode and nickel foil, glass fiber separator (GF / D, 675 μm thick, Whatman), the diameter of the S positive electrode and nickel foil was 14 mm and 16 mm respectively, and the liquid electrolyte was 120 μL.

[0099] Example 3

[0100] In this example, an anode-free lithium-sulfur coin cell was assembled as a test sample.

[0101] Liquid electrolyte: The liquid electrolyte was prepared in an argon-protected glove box with water and oxygen content less than 1 ppm; 1.067 g (8 mmol) of AlCl3 was weighed into 1 mL of SOCl2 and stirred for 0.5 hours until completely dissolved, then 0.486 g (3 mmol) of ethoxy aluminum (AE) was added and stirred for 0.5 hours until completely dissolved, finally 0.329 g (4.5 mmol) of lithium dicyanamide (LiDCA) was added and stirred for 0.5 hours until completely dissolved, to prepare the liquid electrolyte, which was denoted as AE-DCA-AS electrolyte.

[0102] S positive electrode: 45 wt% sulfur powder, 45 wt% Ketjen black and 10 wt% PTFE (60 wt% aqueous dispersion) were mixed in ethanol with a mass ratio of ethanol to solid of 20:1. After uniform dispersion, the obtained sulfur-containing slurry was slowly (80 μL each time) dropped onto a nickel foam suspended on a hot plate at 100 ℃, with an interval of about 5 min between each drop to ensure sufficient evaporation of ethanol, and the process was repeated until the target loading was reached. Finally, vacuum drying was carried out at 70 ℃ overnight, and the rolled flat was weighed.

[0103] The battery assembly was carried out in an argon-filled glove box (water and oxygen content less than 1 ppm). The anode-free lithium-sulfur coin cell (2032 type) was assembled using the above liquid electrolyte, S positive electrode and nickel foil, glass fiber separator (GF / D, 675 μm thick, Whatman), the diameter of the S positive electrode and nickel foil was 14 mm and 16 mm respectively, and the liquid electrolyte was 120 μL.

[0104] Verification example 2

[0105] Li||Ni half-cells were assembled as test samples.

[0106] Liquid electrolyte: Liquid electrolyte was prepared in an argon-filled glovebox (water and oxygen content <1 ppm). 1.067 g (8 mmol) of AlCl3 was weighed into 1 mL of SOCl2 and stirred for 0.5 h until complete dissolution. Then 0.486 g (3 mmol) of ethoxyaluminum (AE) was added and stirred for 0.5 h until complete dissolution. Finally, 0.329 g (4.5 mmol) of lithium dicyanamide (LiDCA) was added and stirred for 0.5 h until complete dissolution. The liquid electrolyte was prepared and noted as AE-DCA-AS electrolyte.

[0107] Cell assembly was performed in an argon-filled glovebox (water and oxygen content <1 ppm). Li||Ni half-cells were assembled using the above liquid electrolyte, lithium foil, nickel foil, and glass fiber separator (GF / D, 675 pm thick, Whatman). The 14 mm diameter nickel foil was paired with a 14 mm diameter lithium foil anode, and the liquid electrolyte was 150 pL.

[0108] Example 4

[0109] Anode-free lithium-sulfur button cells were assembled as test samples.

[0110] Liquid electrolyte: Liquid electrolyte was prepared in an argon-filled glovebox (water and oxygen content <1 ppm). 1.067 g (8 mmol) of AlCl3 was weighed into 1 mL of SOCl2 and stirred for 0.5 h until complete dissolution. Then 0.486 g (3 mmol) of ethoxyaluminum (AE) was added and stirred for 0.5 h until complete dissolution. Then 0.329 g (4.5 mmol) of lithium dicyanamide (LiDCA) was added and stirred for 0.5 h until complete dissolution. Finally, 800 pL of pentafluorobenzene (PFB) was added and stirred for 10 min until complete dissolution. The liquid electrolyte was prepared and noted as PFB-AE-DCA-AS electrolyte.

[0111] S positive electrode: 45 wt% sulfur powder, 45 wt% Ketjen black, and 10 wt% PTFE (60 wt% aqueous dispersion) were mixed in ethanol with a solvent to solid mass ratio of 20:1. After uniform dispersion, the resulting sulfur-containing slurry was slowly (80 pL each time) added to the nickel foam suspended on a hot plate at 100 °C, with an interval of about 5 min between each drop to ensure complete evaporation of ethanol. This process was repeated until the target loading was reached. Finally, vacuum drying was performed at 70 °C overnight, and the sample was flattened using a rolling press and weighed.

[0112] The battery assembly was performed in an argon-filled glovebox (water and oxygen content less than 1 ppm). The anode-free lithium-sulfur button cell (2032 type) was assembled with the above liquid electrolyte, S cathode and nickel foil, glass fiber separator (GF / D, 675 pm thick, Whatman). The diameter of S cathode and nickel foil was 14 mm and 16 mm, respectively. The liquid electrolyte was 120 pL.

[0113] Verification Example 3

[0114] In this verification example, Li||Ni half-batteries were assembled as test samples.

[0115] Liquid electrolyte: The liquid electrolyte was prepared in an argon-protected glovebox with water and oxygen content less than 1 ppm; 1.067 g (8 mmol) of AlCl3 was weighed into 1 mL of SOCl2 and stirred for 0.5 hours until completely dissolved, then 0.486 g (3 mmol) of ethoxyaluminum (AE) was added and stirred for 0.5 hours until completely dissolved, then 0.329 g (4.5 mmol) of lithium dicyanamide (LiDCA) was added and stirred for 0.5 hours until completely dissolved, and finally 800 pL of pentafluorobenzene (PFB) was added and stirred for 10 minutes until completely dissolved, to prepare the liquid electrolyte, which was denoted as PFB-AE-DCA-AS electrolyte.

[0116] The battery assembly was performed in an argon-filled glovebox (water and oxygen content less than 1 ppm). Li||Ni half-batteries were assembled with the above liquid electrolyte, lithium foil, nickel foil and glass fiber separator (GF / D, 675 pm thick, Whatman). The nickel foil with a diameter of 14 mm was paired with a lithium foil anode with a diameter of 14 mm. The liquid electrolyte was 150 pL.

[0117] Example 5

[0118] In this example, lithium-sulfur button full cells were assembled as test samples.

[0119] Liquid electrolyte: The liquid electrolyte was prepared in an argon-protected glovebox with water and oxygen content less than 1 ppm; 1.067 g (8 mmol) of AlCl3 was weighed into 1 mL of SOCl2 and stirred for 0.5 hours until completely dissolved, then 0.486 g (3 mmol) of ethoxyaluminum (AE) was added and stirred for 0.5 hours until completely dissolved, then 0.329 g (4.5 mmol) of lithium dicyanamide (LiDCA) was added and stirred for 0.5 hours until completely dissolved, and finally 800 pL of pentafluorobenzene (PFB) was added and stirred for 10 minutes until completely dissolved, to prepare the liquid electrolyte, which was denoted as PFB-AE-DCA-AS electrolyte.

[0120] S positive electrode: 45 wt% sulfur powder, 45 wt% Ketjen black, and 10 wt% PTFE (60 wt% aqueous dispersion) were mixed in ethanol with a mass ratio of ethanol to solid of 20:1. After uniform dispersion, the obtained sulfur-containing slurry was slowly (80 μL each time) dropped onto the nickel foam suspended on a hot plate at 100 °C, with an interval of about 5 min each time to ensure sufficient evaporation of ethanol. This process was repeated until the target loading was reached. Finally, vacuum drying was performed at 70 °C overnight, flattened using a rolling machine, and weighed.

[0121] Graphite negative electrode: Graphite, Super P conductive carbon black, and polyvinylidene fluoride (PVDF) binder were mixed in a mass ratio of 8:1:1 to prepare a uniform slurry using N-methyl-2-pyrrolidone (NMP) as the solvent. The slurry was coated on the surface of an aluminum foil (thickness 10 μm) using a doctor blade, and then placed in a vacuum oven at 100 °C for 12 hours. The obtained electrode was punched into a disc shape (diameter 12 mm) and pressed at a pressure of 10 MPa to increase the electrode density. The active material loading was 2.0-6.0 mg / cm 2 .

[0122] Battery assembly was performed in an argon-filled glove box (water and oxygen content less than 1 ppm). The anode-free lithium-sulfur button cell (type 2032) was assembled using the above-mentioned liquid electrolyte, S positive electrode, and graphite negative electrode, a glass fiber separator (GF / D, 675 μm thick, Whatman), the diameters of the S positive electrode and the graphite negative electrode were 14 mm and 12 mm, respectively, and the liquid electrolyte was 120 μL.

[0123] Example 6

[0124] In this example, lithium-sulfur button full cells were assembled as test samples.

[0125] Liquid electrolyte: The liquid electrolyte was prepared in an argon-protected glove box with water and oxygen content less than 1 ppm; 1.067 g (8 mmol) of AlCl3 was weighed into 1 mL of SOCl2 and stirred for 0.5 hours until completely dissolved, then 0.486 g (3 mmol) of ethoxy aluminum (AE) was added and stirred for 0.5 hours until completely dissolved, then 0.329 g (4.5 mmol) of lithium dicyanamide (LiDCA) was added and stirred for 0.5 hours until completely dissolved, finally 800 μL of pentafluorobenzene (PFB) was added and stirred for 10 minutes until completely dissolved, to prepare the liquid electrolyte, which was denoted as PFB-AE-DCA-AS electrolyte.

[0126] S positive electrode: 45 wt% sulfur powder, 45 wt% Ketjen black, and 10 wt% PTFE (60 wt% aqueous dispersion) were mixed in ethanol with a mass ratio of ethanol to solid of 20:1. After uniform dispersion, the resulting sulfur-containing slurry was slowly (80 μL each time) dropped onto nickel foam suspended on a hot plate at 100 °C, with an interval of about 5 min between each drop to ensure sufficient evaporation of ethanol, and the process was repeated until the target loading was reached. Finally, vacuum drying was performed at 70 °C overnight, flattened using a rolling machine, and weighed.

[0127] Silicon-carbon negative electrode (Kureha, Silicon-carbon 650) with an active material loading of 7.25 mg / cm 2 .

[0128] Battery assembly was performed in an argon-filled glovebox (water and oxygen content less than 1 ppm). The anode-free lithium-sulfur button cell (2032 type) was assembled using the liquid electrolyte described above, S positive electrode and silicon-carbon negative electrode, glass fiber separator (GF / D, 675 μm thick, Whatman), with the diameter of the S positive electrode and silicon-carbon negative electrode being 14 mm and 12 mm, respectively, and the liquid electrolyte being 120 μL.

[0129] Example 7

[0130] In this example, an anode-free lithium-sulfur button gel solid-state cell was assembled as a test sample.

[0131] Gel solid-state electrolyte: The liquid electrolyte was prepared in an argon-protected glovebox with water and oxygen content less than 1 ppm; 1.067 g (8 mmol) of AlCl3 was weighed into 1 mL of SOCl2 and stirred for 0.5 hours until completely dissolved, then 0.329 g (4.5 mmol) of lithium dicyanamide (LiDCA) was added and stirred for another 0.5 hours until completely dissolved, to prepare the liquid electrolyte, which was then mixed with 3,3-bis(chloromethyl)oxetane (BCMO) at a volume ratio of 5:1 to prepare the gel solid-state electrolyte.

[0132] S positive electrode: 45 wt% sulfur powder, 45 wt% Ketjen black, and 10 wt% PTFE (60 wt% aqueous dispersion) were mixed in ethanol with a mass ratio of ethanol to solid of 20:1. After uniform dispersion, the resulting sulfur-containing slurry was slowly (80 μL each time) dropped onto nickel foam suspended on a hot plate at 100 °C, with an interval of about 5 min between each drop to ensure sufficient evaporation of ethanol, and the process was repeated until the target loading was reached. Finally, vacuum drying was performed at 70 °C overnight, flattened using a rolling machine, and weighed.

[0133] The battery assembly was performed in an argon-filled glovebox (water and oxygen content less than 1 ppm). The anode-free lithium-sulfur button cell (2032 type) was assembled with the above-mentioned gel solid-state electrolyte, S cathode and nickel foil, glass fiber separator (GF / D, 675 pm thick, Whatman). The diameter of S cathode and nickel foil was 14 mm and 16 mm, respectively. The liquid electrolyte was 120 pL.

[0134] Example 8

[0135] The anode-free lithium-sulfur button cell was assembled as a test sample in this example.

[0136] Liquid electrolyte: The liquid electrolyte was prepared in an argon-protected glovebox with water and oxygen content less than 1 ppm; 2 mmol of AlCh was weighed into 1 mL of SOCh and stirred for 0.5 hours until completely dissolved, then 1 mmol of ethoxyaluminum (AE) was added and stirred for 0.5 hours until completely dissolved, finally 1 mmol of lithium dicyanamide (LiDCA) was added and stirred for 0.5 hours until completely dissolved, to prepare the liquid electrolyte.

[0137] S cathode: 45 wt% sulfur powder, 45 wt% Ketjen black and 10 wt% PTFE (60 wt% aqueous dispersion) were mixed in ethanol with a solid to ethanol mass ratio of 20: 1. After uniform dispersion, the obtained sulfur-containing slurry was slowly (80 pL each time) dropped onto the nickel foam suspended on a hot plate at 100 °C, with an interval of about 5 min each time to ensure sufficient evaporation of ethanol. This process was repeated until the target loading was reached. Finally, vacuum drying was performed at 70 °C overnight, flattened using a rolling machine and weighed.

[0138] The battery assembly was performed in an argon-filled glovebox (water and oxygen content less than 1 ppm). The anode-free lithium-sulfur button cell (2032 type) was assembled with the above-mentioned liquid electrolyte, S cathode and nickel foil, glass fiber separator (GF / D, 675 pm thick, Whatman). The diameter of S cathode and nickel foil was 14 mm and 16 mm, respectively. The liquid electrolyte was 120 pL.

[0139] Example 9

[0140] The anode-free lithium-sulfur button cell was assembled as a test sample in this example.

[0141] Liquid electrolyte: The liquid electrolyte was prepared in an argon-protected glovebox with water and oxygen content less than 1 ppm; 13 mmol of AlCh was weighed into 1 mL of SOCh and stirred for 0.5 hours until completely dissolved, then 7.4 mmol of lithium dicyanamide (LiDCA) was added and stirred for 0.5 hours until completely dissolved, to prepare the liquid electrolyte.

[0142] S positive electrode: 45 wt% sulfur powder, 45 wt% Ketjen black and 10 wt% PTFE (60 wt% aqueous dispersion) were mixed in ethanol with a mass ratio of ethanol to solid of 20:1. After homogenous dispersion, the resulting sulfur-containing slurry was slowly (80 μL each time) dropped onto a nickel foam suspended on a hot plate at 100 °C with an interval of about 5 min to ensure sufficient evaporation of ethanol. This process was repeated until the target loading was reached. Finally, vacuum drying was performed at 70 °C overnight, flattened using a rolling machine and weighed.

[0143] Battery assembly was performed in an argon-filled glovebox (water and oxygen content less than 1 ppm). The anode-free lithium-sulfur button cell (2032 type) was assembled using the above liquid electrolyte, S positive electrode and nickel foil, glass fiber separator (GF / D, 675 μm thick, Whatman), with the diameter of S positive electrode and nickel foil being 14 mm and 16 mm, respectively, and the liquid electrolyte being 120 μL.

[0144] Comparative Example 1

[0145] This comparative example is an anode-free lithium-sulfur button cell using only aluminum chloride as electrolyte as test sample.

[0146] Liquid electrolyte: The liquid electrolyte was prepared in an argon-protected glovebox with water and oxygen content less than 1 ppm; 1.067 g (8 mmol) of AICI3 was weighed into 1 mL of SOCI2 and stirred for 0.5 hours until completely dissolved to prepare the liquid electrolyte, which was denoted as AS electrolyte.

[0147] S positive electrode: 45 wt% sulfur powder, 45 wt% Ketjen black and 10 wt% PTFE (60 wt% aqueous dispersion) were mixed in ethanol with a mass ratio of ethanol to solid of 20:1. After homogenous dispersion, the resulting sulfur-containing slurry was slowly (80 μL each time) dropped onto a nickel foam suspended on a hot plate at 100 °C with an interval of about 5 min to ensure sufficient evaporation of ethanol. This process was repeated until the target loading was reached. Finally, vacuum drying was performed at 70 °C overnight, flattened using a rolling machine and weighed.

[0148] Battery assembly was performed in an argon-filled glovebox (water and oxygen content less than 1 ppm). The anode-free lithium-sulfur button cell (2032 type) was assembled using the above liquid electrolyte, S positive electrode and nickel foil, glass fiber separator (GF / D, 675 μm thick, Whatman), with the diameter of S positive electrode and nickel foil being 14 mm and 16 mm, respectively, and the liquid electrolyte being 120 μL.

[0149] Comparative Example 2

[0150] The comparative example 2 is a conventional anode-free lithium-sulfur button cell based on S / Li2S redox chemistry as test sample.

[0151] Liquid electrolyte: The liquid electrolyte was prepared in an argon-filled glovebox with water and oxygen content below 1 ppm; composed of 1 M lithium bis(trifluoromethanesulfonyl)imide in 1,3-dioxolane and ethylene glycol dimethyl ether, with 5 wt% lithium nitrate added.

[0152] S cathode: 45 wt% sulfur powder, 45 wt% Ketjen black, and 10 wt% PTFE (60 wt% aqueous dispersion) were mixed in ethanol with a mass ratio of ethanol to solid of 20:1. After uniform dispersion, the resulting sulfur-containing slurry was slowly (80 μL each time) dropped onto a nickel foam suspended on a hot plate at 100 °C, with an interval of about 5 min between each drop to ensure sufficient evaporation of ethanol, and the process was repeated until the target loading was reached. Finally, vacuum drying was performed at 70 °C overnight, flattened using a rolling machine, and weighed.

[0153] Battery assembly was performed in an argon-filled glovebox (water and oxygen content below 1 ppm). An anode-free lithium-sulfur button cell (2032 type) was assembled using the liquid electrolyte, S cathode, and nickel foil, glass fiber separator (GF / D, 675 μm thick, Whatman) described above, with the diameter of the S cathode and nickel foil being 14 mm and 16 mm, respectively, and the liquid electrolyte being 120 μL.

[0154] Comparative example 3

[0155] The comparative example 3 is an anode-free lithium-sulfur button cell based on the implementation of example 4 as test sample, but using a sulfur-free elemental sulfur cathode.

[0156] Sulfur-free elemental sulfur cathode: 90 wt% Ketjen black and 10 wt% PTFE (60 wt% aqueous dispersion) were mixed in ethanol with a mass ratio of ethanol to solid of 20:1. After uniform dispersion, the resulting sulfur-containing slurry was slowly (80 μL each time) dropped onto a nickel foam suspended on a hot plate at 100 °C, with an interval of about 5 min between each drop to ensure sufficient evaporation of ethanol, and the process was repeated until the target loading was reached. Finally, vacuum drying was performed at 70 °C overnight, flattened using a rolling machine, and weighed.

[0157] Electrochemical tests

[0158] All tests were performed in a 25 °C thermostat (Neware MHW-200). Battery performance was characterized by a Neware CT-4008 system. Cycling tests: the batteries were pre-charged and discharged for 3 cycles for activation, with charge capacity limits (e.g., 200, 400, 800, 1000, 2000 mAh / g), a discharge cutoff voltage of 2.0 V, followed by long cycling tests.

[0159] Sulfur has abundant multivalent states (-2, 0, +2, +4, +6) and can form high-valence sulfur compounds through oxidation process, showing high theoretical capacity and energy density. However, due to the chemical inertness of sulfur, its electrochemical oxidation process usually requires high voltage driving, and there is little in-depth study in the traditional lithium-sulfur battery system. To address this challenge, as shown in Figure 1 Example 3 provides a new anode-free lithium-sulfur battery based on high-valence sulfur / tetrachloride sulfur (S / SCI4) positive electrode chemistry. The battery uses an S8 positive electrode, a nickel foil negative electrode current collector, and a non-flammable chloroaluminate-based electrolyte (3 M AE + 4.5 M LiDCA + 8M AlCl3 + SOCl2 / PFB (volume ratio 5:4)). Studies have shown that the lithium-sulfur battery based on S / SCI4 positive electrode chemical reaction realizes the high-valence sulfur redox process of 32 electron transfer, far exceeding the 16 electron transfer mechanism of the traditional lithium-sulfur battery. The battery has an average discharge voltage as high as 3.52 V, and a discharge specific capacity of 1761 mAh g -1 , which is significantly better than the traditional system (Comparative Example 2) with a discharge voltage of only about 2.2 V and a capacity of 1400-1640 mAh g -1 . Mechanism studies have confirmed that the dicyanamide ion (DCA - ) can stabilize the high-valence sulfur species, while the ethoxyaluminum (AE) and pentafluorobenzene (PFB) additives synergistically control the electrolyte structure, both weakening the Li + -DCA - coordination to promote the positive electrode reaction, and optimizing the negative electrode interface to achieve reversible cycling. The present technology opens up a new path for constructing the next generation of high energy density batteries by activating high-valence sulfur chemistry.

[0160] To explore the effect of PFB additive and AE on the cycle stability of the full battery, as shown in Figure 2 a, long cycle tests were carried out at a fixed charge capacity of 800 mAh g -1 . The results show that the battery without PFB additive and AE (Example 1) has a discharge capacity of 385 mAh g -1 after the tenth cycle; while the system containing PFB additive and AE (Example 3) still maintains a discharge capacity of 719 mAh g -1 under the same conditions, showing significantly improved capacity retention and cycle reversibility, which confirms the key role of PFB and AE in stabilizing the electrode interface.

[0161] As shown in Figure 3 , X-ray photoelectron spectroscopy confirms the occurrence of reversible S0 / S 4+The conversion process, in which the S 2p spectrum confirms the reversible change of sulfur from the 0 to +4 oxidation state, confirms that the main source of capacity originates from the electrochemical reaction at the sulfur cathode, such as... Figure 2 As shown in b, a control experiment was set up in which the active material sulfur was removed from the positive electrode, leaving only the same areal loading of Ketjen Black conductive agent. Under these conditions, the battery (Comparative Example 3) could hardly perform effective charge and discharge, and the observed trace discharge capacity could be attributed to irreversible side reactions of the electrolyte itself. This result strongly rules out the possibility that the conductive agent or electrolyte dominates the capacity, further confirming the core contribution of the sulfur positive electrode in this system.

[0162] like Figure 4 As shown, the electrolyte composition was systematically analyzed using nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy. In an 8 M AlCl3 dissolved in SOCl2 electrolyte (AS electrolyte), the main component was Al2Cl7. - After introducing LiDCA (DCA-AS electrolyte), DCA - Coordination with Al promotes partial Al2Cl7 - It can be converted into AlCl4 - Upon further addition of AE (AE-DCA-AS electrolyte), AE reacts with AlCl3 to generate intermediates such as Cl2AlOEt, and weakens the interaction between AlCl3 and DCA. - The interaction between them releases more free DCA - Anions. This process occurs in... 27 In Al NMR spectra, this manifests as a weakening of the Al-DCA coordination signal, and the DCA signal is reproduced in FTIR spectra. - Characteristic absorption peaks of free DCA. - Anions have a dual function: they can stabilize high-valence sulfur species (S) on the positive electrode side. 4+ On the negative electrode side, it participates in the construction of a stable solid electrolyte interface (SEI) rich in inorganic components. Further introduction of the additive PFB (PFB-AE-DCA-AS electrolyte) 7 The chemical shift in LiNMR shifts towards lower fields indicates that Li + With DCA - The coordination between them is further weakened, thereby releasing more free DCA. - Anions optimize the electrolyte structure and interfacial reaction kinetics.

[0163] like Figure 5As shown, the functions of PFB additive and AE were further validated in Li||Ni half-cell tests. In the electrolyte system without PFB additive and AE, the lithium metal deposition / stripping process was extremely unstable, with low coulombic efficiency, indicating persistent interfacial side reactions. With the introduction of AE, as shown by the spectroscopic results, it effectively released free DCA. - Anions. These DCA - The lithium ions migrate to the negative electrode interface and participate in the construction of a stable SEI layer mainly composed of inorganic lithium salts, which improves the coulombic efficiency of the battery to 91.85% in the 18th cycle, achieving reversible cycling. Further addition of PFB additives, although slightly increasing the deposition overpotential due to hindered lithium ion migration, resulted in more free DCA. - Anions significantly enhanced the protective effect of the interfacial layer, further improving the coulombic efficiency to 95.12%. This result is highly consistent with the aforementioned electrolyte structure analysis, jointly revealing that PFB and AE release free DCA by regulating the solvation structure. - Anions are the core mechanism for optimizing the chemistry of the negative electrode interface.

[0164] like Figure 6 As shown, X-ray photoelectron spectroscopy (XPS) analysis of the negative electrode interface revealed that different electrolyte systems significantly modulate the composition of the negative electrode interface. In the DCA-AS electrolyte, a lithium nitride (Li3N)-dominated interface layer was formed. After the introduction of XPS, the signal of the lithium oxide (Li2O) component increased significantly, confirming that Li2O is a key component affecting lithium deposition / stripping behavior in this system. Further addition of PFB further optimized the interface composition: the relative content of Li2O continuously increased, and a distinct lithium fluoride (LiF) characteristic peak appeared. LiF possesses high interfacial energy and good ion transport properties, and together with Li2O, it constructs a synergistically enhanced interface layer, significantly improving the reversibility and structural stability of lithium metal deposition / stripping. This result was directly verified in the cycling performance tests of Li||Ni half-cells.

[0165] Figures 7~10 The feasibility of lithium-sulfur batteries was demonstrated by constructing full cells with different negative electrodes and under different electrolyte molar concentrations.

[0166] Furthermore, based on the above experimental evidence, it is reasonable to infer that lithium salts containing cyanide, other than lithium dicyandiamide, also have similar electrochemical properties, and lithium dicyandiamide is the optimal choice based on experimental evidence.

[0167] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A lithium-sulfur battery, characterized in that: The electrolyte includes a lithium cyanide salt and a Lewis chlorine acid, wherein the Lewis chlorine acid has a molar concentration of 2 to 13 mol / L in the solvent, and the lithium cyanide salt has a molar concentration of 80 to 100% of the solubility saturation in the solvent and a molar concentration of at least 1 mol / L. The positive electrode is mainly composed of a positive electrode current collector and a conductive coating containing elemental sulfur on its surface, or it can be directly composed of materials containing elemental sulfur.

2. The lithium-sulfur battery according to claim 1, characterized in that: The cyanide-containing lithium salt includes at least one of lithium dicyandiamide, lithium butyl ester, and lithium 4,5-dicyano-2-(trifluoromethyl)imidazolium.

3. The lithium-sulfur battery according to claim 1, characterized in that: The chlorinated Lewis acid includes at least one of aluminum trichloride, gallium trichloride, ferric chloride, and zinc chloride.

4. The lithium-sulfur battery according to claim 1, characterized in that: The electrolyte also includes aluminum ethoxylate.

5. The lithium-sulfur battery according to claim 1, characterized in that: The lithium-sulfur battery is either a liquid lithium-sulfur battery or a solid lithium-sulfur battery.

6. The lithium-sulfur battery according to claim 5, characterized in that: The liquid lithium-sulfur battery is a lithium-sulfur battery that uses a liquid electrolyte, which is mainly composed of lithium salt containing cyanide and Lewis acid containing chlorine dissolved in a solvent. The liquid electrolyte also includes pentafluorobenzene as an additive.

7. The lithium-sulfur battery according to claim 1, characterized in that: The positive electrode is mainly composed of a positive electrode current collector and a conductive coating containing elemental sulfur on its surface. The conductive coating containing elemental sulfur is formed by mixing and coating the surface of the positive electrode current collector with carbon-based materials for conductive coating, sulfur powder and binder as raw material components; or, the positive electrode is mainly composed of materials containing elemental sulfur directly, which is formed by mixing and curing carbon-based materials for conductive coating, sulfur powder and binder as raw material components as raw material components.

8. The lithium-sulfur battery according to claim 1, characterized in that: The lithium-sulfur battery also includes a negative electrode and / or a negative electrode current collector.

9. The lithium-sulfur battery according to claim 8, characterized in that: The negative electrode is made of elemental lithium metal, or a conventional carbon-containing negative electrode or an alloy negative electrode; or, the negative electrode is formed by loading lithium foil onto the surface of the negative electrode current collector.

10. The lithium-sulfur battery as described in claim 1 is applied to the field of energy storage.

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