Lithium-sulfur battery

Abstract

The present application provides a lithium-sulfur battery and an electronic device including the same, the lithium-sulfur battery including a sulfur positive electrode, a lithium negative electrode, and an electrolyte, in which the electrolyte includes a first additive including at least one of (thiophenyl) trimethylsilane, (ethylthio) trimethylsilane, and bis (trimethylsilyl) sulfide.

Description

Technical Field

[0001] The present application relates to the field of batteries, and particularly to a lithium-sulfur battery. Background Art

[0002] A lithium-sulfur battery refers to a battery in which a sulfur-containing material having a sulfur-sulfur bond (S-S bond) is used as a positive electrode active material, and lithium metal is used as a negative electrode active material, and the mutual conversion between chemical energy and electrical energy is achieved through a two-electron electrochemical reaction between sulfur and lithium. The lithium-sulfur battery has a theoretical capacity of up to 1675 mAh / g for the positive electrode and up to 3860 mAh / g for the negative electrode, which makes the lithium-sulfur battery have a very high theoretical energy density (about 2600 Wh / kg) and is one of the most promising batteries currently under development.

[0003] However, a series of side reactions occur during the charge and discharge processes of the positive and negative electrodes of existing lithium-sulfur batteries, resulting in poor electrochemical performances such as capacity and rate performance.

[0004] In a lithium-sulfur battery, the active material sulfur and its discharge products (Li2S2 / Li2S) on the sulfur positive electrode side have low conductivity, and the sulfur volume changes greatly during the charge and discharge processes (the volume expansion can reach 80%), which easily leads to the destruction of the electrode structure and rapid attenuation of the battery capacity. The intermediate product long-chain polysulfide generated during the charge and discharge is easily soluble in the electrolyte and migrates between the positive and negative electrodes, causing the "shuttle effect", consuming a large amount of active materials and reducing the Coulomb efficiency of the battery.

[0005] In addition, the main problems of the lithium metal negative electrode are the side reactions between the highly active lithium metal and the electrolyte and the uncontrollable growth of lithium dendrites, which lead to battery short circuit, low cycle Coulomb efficiency, poor cycle life and unsatisfactory safety.

[0006] Therefore, there is a need in the art for a lithium-sulfur battery that can simultaneously suppress side reactions on both the positive electrode side and the negative electrode side, thereby obtaining desired electrochemical performances and safety performances. Summary of the Invention

[0007] In a first aspect of the present application, the present application provides a lithium-sulfur battery, which includes a sulfur positive electrode, a lithium negative electrode and an electrolyte. Among them, the electrolyte includes a first additive, and the first additive includes at least one of (phenylthio)trimethylsilane, (ethylthio)trimethylsilane and bis(trimethylsilyl)sulfide.

[0008] According to the lithium-sulfur battery of the present application, by providing the first additive in the electrolyte, not only can the rapid conversion of polysulfides on the positive electrode side be accelerated, the shuttle effect of intermediate products be improved, but also a stable interface layer can be formed with the lithium metal negative electrode to inhibit the growth of irregular lithium dendrites and the side reactions between lithium metal and the electrolyte. Thus, through the simultaneous improvement of both the positive and negative electrode sides, the cycle stability of the lithium-sulfur battery can be greatly improved.

[0009] According to an embodiment of the present application, the electrolyte further includes an ether solvent, and the ether solvent includes at least one of triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dioxolane, ethylene glycol dimethyl ether, dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2 - diethoxyethane, ethoxymethoxyethane, 2 - methyltetrahydrofuran, and tetrahydrofuran.

[0010] According to an embodiment of the present application, the ether solvent includes dioxolane and ethylene glycol dimethyl ether. In some embodiments, based on the total weight of the electrolyte, the content of dioxolane is 20% by weight to 80% by weight, such as 20% by weight, 30% by weight, 40% by weight, 50% by weight, 60% by weight, 70% by weight, 80% by weight, or an interval composed of them. In some embodiments, based on the total weight of the electrolyte, the content of ethylene glycol dimethyl ether is 20% by weight to 80% by weight, such as 20% by weight, 30% by weight, 40% by weight, 50% by weight, 60% by weight, 70% by weight, 80% by weight, or an interval composed of them. By using the above - mentioned contents of dioxolane and ethylene glycol dimethyl ether in the electrolyte, intermediate polysulfides generated during the redox process of the sulfur cathode can be dissolved, providing improved reaction kinetics.

[0011] According to an embodiment of the present application, the electrolyte includes dioxolane and ethylene glycol dimethyl ether, and the volume ratio of dioxolane to ethylene glycol dimethyl ether is 0.5:1 to 2:1, such as 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, or any interval composed of them. In one embodiment, the volume ratio of dioxolane to ethylene glycol dimethyl ether is 0.8:1 to 1.2:1.

[0012] According to an embodiment of the present application, in the electrolyte, the weight content of dioxolane is greater than the weight content of ethylene glycol dimethyl ether.

[0013] According to an embodiment of the present application, the electrolyte further includes at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium perchlorate (LiClO4), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2, LiTFSI), lithium tris(trifluoromethanesulfonyl)methyl (LiC(SO2CF3)3), lithium hexafluorosilicate (LiSiF6), lithium bis(oxalato)borate (LiBOB), and lithium difluoroborate (LiBF2).

[0014] When the content of the first additive is too low, it is insufficient to form a stable interface layer on the lithium negative electrode. When the content of the first additive is too high, it will affect the viscosity and lithium ion conductivity of the electrolyte and deteriorate the electrochemical performance of the battery. Therefore, according to an embodiment of the present application, based on the total weight of the electrolyte, the content of the first additive is 0.1 wt% to 2 wt%, such as 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt% or any interval composed of them.

[0015] According to an embodiment of the present application, the electrolyte includes lithium nitrate and lithium bis(trifluoromethanesulfonyl)imide. And in the electrolyte, the content of lithium nitrate is 0.1 wt% to 2 wt%, such as 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt% or any interval composed of them. According to an embodiment of the present application, the content of lithium bis(trifluoromethanesulfonyl)imide is 10 wt% to 35 wt%, such as 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt% or any interval composed of them.

[0016] According to an embodiment of the present application, in the electrolyte, the content of lithium nitrate is 0.5 wt% to 1.5 wt%, and / or the content of lithium bis(trifluoromethanesulfonyl)imide is 15 wt% to 25 wt%.

[0017] By using lithium nitrate and lithium bis(trifluoromethanesulfonyl)imide in the electrolyte, lithium nitrate can form an electrically insulating layer on the lithium metal negative electrode through a spontaneous reduction reaction and prevent the further reduction of polysulfides on the lithium negative electrode, thereby enhancing the interfacial stability of the metal lithium negative electrode. While lithium bis(trifluoromethanesulfonyl)imide can improve the chemical stability and thermal stability of the electrolyte while ensuring the solubility of the lithium salt and the ionic conductivity and maintain a relatively low cost to a certain extent.

[0018] According to an embodiment of the present application, the sulfur positive electrode includes a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer includes sulfur and a conductive material. Among them, based on the total weight of the positive electrode active material layer, the content of sulfur is 60% by weight to 95% by weight, such as 60% by weight, 65% by weight, 70% by weight, 75% by weight, 80% by weight, 85% by weight, 90% by weight, 95% by weight, or any interval formed by them; the content of the conductive material is 5% by weight to 40% by weight, such as 5% by weight, 10% by weight, 15% by weight, 20% by weight, 25% by weight, 30% by weight, 35% by weight, 40% by weight, or any interval formed by them.

[0019] According to an embodiment of the present application, the lithium negative electrode is made of lithium metal, and / or the liquid-sulfur ratio of the lithium-sulfur battery is 2 μL / mg to 10 μL / mg.

[0020] According to an embodiment of the present application, the electrolyte further includes a solvent and a lithium salt. The solvent includes 1,3-dioxolane and 1,2-dimethoxyethane, and the lithium salt includes lithium nitrate and lithium bis(trifluoromethanesulfonyl)imide. Based on the total weight of the electrolyte, the content of 1,3-dioxolane is 30% by weight to 60% by weight, the content of 1,2-dimethoxyethane is 30% by weight to 60% by weight, the content of lithium nitrate is 0.5% by weight to 1.5% by weight, and the content of lithium bis(trifluoromethanesulfonyl)imide is 15% by weight to 25% by weight.

[0021] In the second aspect of the present application, the present application provides an electronic device, which includes the lithium-sulfur battery according to the second aspect of the present application. Description of the Drawings

[0022] Figure 1 Schematically shows the charge-discharge curves of the lithium-sulfur batteries of Example 2 and Comparative Example 1 under the condition of 0.5C rate;

[0023] Figure 2 Schematically shows the cycle performance of the lithium-sulfur batteries of Example 2 and Comparative Example 1 under the condition of 1C rate;

[0024] Figure 3 Schematically shows the cycle performance of the lithium-copper batteries of Example 5 and Comparative Example 2 under the condition of 1C rate;

[0025] Figure 4 Schematically shows the 0.5C discharge specific capacity of the examples and the comparative examples. Detailed Embodiments

[0026] Embodiments of the present application will be described in detail hereinafter. Embodiments of the present application should not be construed as limiting the scope of the claims of the present application. Unless otherwise expressly specified, the following terms used herein have the meanings set forth below.

[0027] As used herein, the term "about" is used to describe and account for small variations. When used in connection with an event or circumstance, the term can refer to instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs very nearly. For example, when used in connection with a numerical value, the term can refer to a range of variation of less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. Additionally, quantities, ratios, and other numerical values are sometimes presented herein in a range format. It should be understood that such range formats are for convenience and brevity and should be interpreted flexibly to include not only the explicitly specified numerical values as range limits, but also all individual numerical values or sub-ranges subsumed within the range as if each numerical value and sub-range were explicitly specified.

[0028] In the detailed description and claims, a list of items joined by the term "one of" can mean any one of the listed items. For example, if items A and B are listed, then the phrase "one of A and B" means only A or only B. In another example, if items A, B, and C are listed, then the phrase "one of A, B, and C" means only A; only B; or only C. Item A can include a single element or multiple elements. Item B can include a single element or multiple elements. Item C can include a single element or multiple elements.

[0029] In the detailed description and claims, a list of items joined by the term "at least one of", "at least one kind of", or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" or "at least one of A or B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" or "at least one of A, B, or C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A can include a single element or multiple elements. Item B can include a single element or multiple elements. Item C can include a single element or multiple elements.

[0030] In the context of the present invention, the "liquid sulfur ratio" refers to the mass ratio of the electrolyte injected in a lithium-sulfur battery to the mass of the positive electrode active material sulfur.

[0031] I. Lithium-Sulfur Battery

[0032] The lithium-sulfur battery of the present application includes a sulfur positive electrode, a lithium negative electrode, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are inserted into and extracted from between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate to prevent short circuit between the positive and negative electrodes and allow ions to pass through.

[0033] In some embodiments, the liquid-sulfur ratio of the lithium-sulfur battery is from 2 μL / mg to 10 μL / mg, such as 2 μL / mg, 3 μL / mg, 4 μL / mg, 5 μL / mg, 6 μL / mg, 7 μL / mg, 8 μL / mg, 9 μL / mg, 10 μL / mg, or any interval composed of them.

[0034] Sulfur positive electrode

[0035] In some embodiments, the sulfur positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, and the positive electrode active material contains the positive electrode active material.

[0036] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.

[0037] In some embodiments, the positive electrode active material can be a positive electrode active material known in the art for lithium-sulfur batteries. As an example, the positive electrode active material can include at least one of the following materials: elemental sulfur, sulfur-containing compounds, or mixtures thereof. The sulfur-containing compounds can be especially Li2Sn (n≥1), organic sulfur compounds, or carbon-sulfur polymers ((C2S x ) n , where x = 2.5 to 50, and n≥2).

[0038] In some embodiments, the positive electrode active material layer can further include a conductive material. The conductive material can be a carbon-based material, such as carbon black, graphite, graphene, activated carbon, carbon fiber, carbon nanotube (CNT), etc. Additionally, metal fibers, such as metal mesh, etc.; metal powders, such as copper, silver, nickel, aluminum, etc.; or organic conductive materials, such as polyphenylene derivatives, etc. can also be used as the conductive material. The conductive materials can be used alone or in combination. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of the battery can also be used. These positive electrode active materials can be used alone or in combination of two or more.

[0039] In some embodiments, the positive electrode active material layer further includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride - tetrafluoroethylene - propylene terpolymer, vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene terpolymer, tetrafluoroethylene - hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0040] In some embodiments, the positive electrode sheet can be prepared in the following manner: dispersing the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N - methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode sheet can be obtained.

[0041] Lithium negative electrode

[0042] In some embodiments, the lithium negative electrode can be lithium metal or a lithium alloy.

[0043] Electrolyte

[0044] The electrolyte according to the present application includes a first additive, and the first additive includes at least one of (phenylthio)trimethylsilane, (ethylthio)trimethylsilane, and bis(trimethylsilyl)sulfide.

[0045] In some embodiments, the first additive is (phenylthio)trimethylsilane. In some embodiments, the first additive is bis(trimethylsilyl)sulfide. In some embodiments, the first additive is (ethylthio)trimethylsilane.

[0046] In some embodiments, based on the total weight of the electrolyte, the content of (phenylthio)trimethylsilane is 0.1 wt% to 2 wt%, for example, the content of the first additive is 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt% or any interval composed of them.

[0047] In some embodiments, based on the total weight of the electrolyte, the content of bis(trimethylsilyl)sulfide is 0.1 wt% to 2 wt%, for example, the content of the first additive is 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt% or any interval formed by them.

[0048] In some embodiments, based on the total weight of the electrolyte, the content of (ethylthio)trimethylsilane is 0.1 wt% to 2 wt%, for example, the content of the first additive is 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2.0 wt% or any interval formed by them.

[0049] In some embodiments, the electrolyte may optionally further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of improving certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0050] Separator

[0051] In some embodiments, a separator is further disposed between the positive electrode and the negative electrode in the lithium-sulfur battery to prevent short circuit. The present application has no particular limitation on the material and shape of the separator, and it can be any technology disclosed in the prior art. In some embodiments, the separator includes a polymer or an inorganic substance formed of a material stable to the electrolyte of the present application.

[0052] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly by a winding process or a stacking process.

[0053] In some embodiments, the lithium-sulfur battery may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0054] In some embodiments, the outer packaging of the lithium-sulfur battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the lithium-sulfur battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0055] This application places no particular restrictions on the shape of the lithium-sulfur battery, which can be cylindrical, square, or any other arbitrary shape.

[0056] II. Electronic Device

[0057] The electronic device of this application can be any device that uses the lithium-sulfur battery of this application.

[0058] In some embodiments, the electronic device includes, but is not limited to: laptop computers, pen-input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, liquid crystal televisions, hand-held cleaners, portable CD players, minidiscs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, motorcycles, motorized bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, or lithium-ion capacitors, etc.

[0059] To achieve the above objectives and enable those skilled in the art to understand the solution of this application, the following gives examples of the specific implementation methods adopted in this application. It should be noted that the described embodiments are only partial embodiments of this application, rather than all embodiments.

[0060] III. Test Methods

[0061] 0.5C Discharge Specific Capacity

[0062] The charge and discharge tests of the button battery are all completed on the LAND CT2001A Blue Electric Battery Test System. 1) Let the button battery stand for 4 h; 2) Discharge at 0.5C to 1.80 V; 3) After standing for 10 min, charge at 0.5C CC to 2.70 V; 4) After standing for 10 min, discharge at 0.5C to 1.8 V; 5) Repeat steps 3 - 4 three times, and take the discharge gram capacity of the third time as the 0.5C discharge specific capacity.

[0063] 1C Capacity Retention Rate Test

[0064] 1) Let the button battery stand still in an environment of 25°C for 4 h to reach temperature equilibrium; 2) Discharge at 0.2C until 1.8V; 3) After standing still for 10 min, charge at 0.2C CC until 2.70V; 4) After standing still for 10 min, discharge at 1C until 1.80V; 5) After standing still for 10 min, charge at 1C until 2.70V; 6) Repeat steps 4 - 5 for 500 times, and use the ratio of the discharge specific capacity of the 500th time to the discharge specific capacity of the first 1C discharge as the cycle capacity retention rate.

[0065] Example 1

[0066] Preparation of the electrolyte: In a mixed solution of DOL (dioxolane) and DME (ethylene glycol dimethyl ether) with a volume ratio of 1:1, lithium salts LiTFSI and LiNO3 were added. The concentration of LiTFSI was 1 mol / L, and the concentration of LiNO3 was 0.20 mol / L. An additive (phenylthio)trimethylsilane with a concentration of 5 mmol / L was added to obtain the electrolyte. Based on the total weight of the electrolyte, the content of DOL was 41.56 wt%, the content of DME was 34.45 wt%, the content of LiTFSI was 22.81 wt%, the content of LiNO3 was 1.09 wt%, and the content of (phenylthio)trimethylsilane was 0.07 wt%.

[0067] Preparation of the positive electrode: Sulfur solid powder and multi-walled carbon nanotubes were mixed in a mass ratio of 8:2, and then heated at 155°C for 12 h in an inert atmosphere. The carbon nanotubes loaded with sulfur were weighed with a binder PVDF in a mass ratio of 9:1, and N-methylpyrrolidone (NMP) was added to mix and adjust into a slurry. The slurry was evenly coated on an aluminum foil current collector with a film coater, and after drying, it was cut into a pole piece with a diameter of 14 mm and weighed. The sulfur loading was 2 mg / cm 2 。

[0068] Preparation of the negative electrode: A lithium metal sheet with a thickness of 450 μm and a diameter of 15.6 mm was used as the negative electrode;

[0069] Preparation of the separator: The separator was Celgard 2400 with a diameter of 19 mm.

[0070] The carbon nanotubes loaded with sulfur positive electrode, separator, and lithium metal negative electrode of this example were assembled and injected with the electrolyte to obtain a CR2025 button battery, where the liquid sulfur ratio (E / S) was 10 μL / mg.

[0071] Example 2

[0072] Preparation of electrolyte: Lithium salts LiTFSI and LiNO3 were added to a mixed solution of DOL (1,3-dioxolane) and DME (ethylene glycol dimethyl ether) with a volume ratio of 1:1. The concentration of LiTFSI was 1 mol / L, and the concentration of LiNO3 was 0.20 mol / L. An additive, (phenylthio)trimethylsilane, with a concentration of 10 mmol / L was added to obtain the electrolyte. Based on the total weight of the electrolyte, the content of DOL was 41.53 wt%, the content of DME was 34.42 wt%, the content of LiTFSI was 22.79 wt%, the content of LiNO3 was 1.09 wt%, and the content of (phenylthio)trimethylsilane was 0.14 wt%.

[0073] Preparation of the positive electrode: Sulfur solid powder and multi-walled carbon nanotubes were mixed at a mass ratio of 8:2, and then heated at 155 °C for 12 hours in an inert atmosphere. The carbon nanotubes loaded with sulfur were weighed with a binder PVDF at a mass ratio of 9:1, and N-methylpyrrolidone (NMP) was added to mix and adjust into a slurry. The slurry was evenly coated on an aluminum foil current collector with a film coater, and after drying, it was cut into a pole piece with a diameter of 14 mm and weighed. The sulfur loading was 2 mg / cm 2 。

[0074] Preparation of the negative electrode: A lithium metal sheet with a thickness of 450 μm and a diameter of 15.6 mm was used as the negative electrode;

[0075] Preparation of the separator: The separator was Celgard 2400 with a diameter of 19 mm.

[0076] The carbon nanotube positive electrode loaded with sulfur, the separator, and the lithium metal negative electrode of this example were assembled and injected with the electrolyte to obtain a CR2025 button battery, where the liquid-sulfur ratio (E / S) was 10 μL / mg.

[0077] Example 3

[0078] Preparation of electrolyte: Lithium salts LiTFSI and LiNO3 were added to a mixed solution of DOL (1,3-dioxolane) and DME (ethylene glycol dimethyl ether) with a volume ratio of 1:1. The concentration of LiTFSI was 1 mol / L, and the concentration of LiNO3 was 0.20 mol / L. An additive, (phenylthio)trimethylsilane, with a concentration of 50 mmol / L was added to obtain the electrolyte. Based on the total weight of the electrolyte, the content of DOL was 41.29 wt%, the content of DME was 34.23 wt%, the content of LiTFSI was 22.66 wt%, the content of LiNO3 was 1.09 wt%, and the content of (phenylthio)trimethylsilane was 0.72 wt%.

[0079] Preparation of the positive electrode: Sulfur solid powder and multi-walled carbon nanotubes are mixed in a mass ratio of 8:2, and then heated at 155 °C for 12 hours in an inert atmosphere. The carbon nanotubes loaded with sulfur are weighed with the binder PVDF in a mass ratio of 9:1, and N-methylpyrrolidone (NMP) is added and mixed to adjust into a slurry. The slurry is evenly coated on an aluminum foil current collector with a film coater, dried and cut into a pole piece with a diameter of 14 mm and weighed. The sulfur loading is 2 mg / cm 2 .

[0080] Preparation of the negative electrode: A lithium metal sheet with a thickness of 450 μm and a diameter of 15.6 mm is used as the negative electrode;

[0081] Preparation of the separator: The separator is Celgard 2400 with a diameter of 19 mm.

[0082] The carbon nanotube positive electrode loaded with sulfur, the separator, and the lithium metal negative electrode of this example are assembled and injected with electrolyte to obtain a CR2025 button battery, where the liquid-sulfur ratio (E / S) is 10 μL / mg.

[0083] Example 4

[0084] Preparation of the electrolyte: Lithium salts LiTFSI and LiNO3 are added to a mixed solution of DOL (dioxolane) and DME (ethylene glycol dimethyl ether) with a volume ratio of 1:1. The concentration of LiTFSI is 1 mol / L, the concentration of LiNO3 is 0.20 mol / L, and an additive (phenylthio)trimethylsilane with a concentration of 100 mmol / L is added to obtain the electrolyte. Based on the total weight of the electrolyte, the content of DOL is 41.00 wt%, the content of DME is 33.98 wt%, the content of LiTFSI is 22.50 wt%, the content of LiNO3 is 1.08 wt%, and the content of (phenylthio)trimethylsilane is 1.43 wt%.

[0085] Preparation of the positive electrode: Sulfur solid powder and multi-walled carbon nanotubes are mixed in a mass ratio of 8:2, and then heated at 155 °C for 12 hours in an inert atmosphere. The carbon nanotubes loaded with sulfur are weighed with the binder PVDF in a mass ratio of 9:1, and N-methylpyrrolidone (NMP) is added and mixed to adjust into a slurry. The slurry is evenly coated on an aluminum foil current collector with a film coater, dried and cut into a pole piece with a diameter of 14 mm and weighed. The sulfur loading is 2 mg / cm 2 .

[0086] Preparation of the negative electrode: A lithium metal sheet with a thickness of 450 μm and a diameter of 15.6 mm is used as the negative electrode;

[0087] Preparation of the separator: The separator is Celgard 2400 with a diameter of 19 mm.

[0088] The sulfur-loaded carbon nanotube cathode, separator, and lithium metal anode of this example were assembled and electrolyte was injected to obtain a CR2025 coin cell, where the electrolyte-to-sulfur ratio (E / S) was 10 μL / mg.

[0089] Example 5

[0090] Preparation of electrolyte: Lithium salts LiTFSI and LiNO3 were added to a mixed solution of DOL (dioxolane) and DME (ethylene glycol dimethyl ether) with a volume ratio of 1:1. The concentration of LiTFSI was 1 mol / L, the concentration of LiNO3 was 0.20 mol / L, and an additive (phenylthio)trimethylsilane with a concentration of 50 mmol / L was added to obtain the electrolyte. Based on the total weight of the electrolyte, the content of DOL was 41.29 wt%, the content of DME was 34.23 wt%, the content of LiTFSI was 22.66 wt%, the content of LiNO3 was 1.09 wt%, and the content of (phenylthio)trimethylsilane was 0.72 wt%.

[0091] Preparation of separator: The separator was Celgard 2400 with a diameter of 19 mm.

[0092] A lithium metal sheet was used as the working electrode, and a fresh copper foil was used as the counter electrode. Then, they were assembled with the electrolyte and separator into a lithium-copper CR2025 coin cell.

[0093] Example 6

[0094] Preparation of electrolyte: Lithium salts LiTFSI and LiNO3 were added to a mixed solution of DOL (dioxolane) and DME (ethylene glycol dimethyl ether) with a volume ratio of 1:1. The concentration of LiTFSI was 1 mol / L, the concentration of LiNO3 was 0.20 mol / L, and an additive ethylthiotrimethylsilane with a concentration of 50 mmol / L was added to obtain the electrolyte. Based on the total weight of the electrolyte, the content of DOL was 41.37 wt%, the content of DME was 34.29 wt%, the content of LiTFSI was 22.70 wt%, the content of LiNO3 was 1.09 wt%, and the content of ethylthiotrimethylsilane was 0.53 wt%.

[0095] Preparation of cathode: Sulfur solid powder and multi-walled carbon nanotubes were mixed in a mass ratio of 8:2, and then heated at 155 °C for 12 hours in an inert atmosphere. The sulfur-loaded carbon nanotubes and the binder PVDF were weighed in a mass ratio of 9:1, and N-methylpyrrolidone (NMP) was added and mixed to adjust into a slurry. The slurry was evenly coated on an aluminum foil current collector with a coating machine, dried, and cut into a pole piece with a diameter of 14 mm and weighed. The sulfur loading was 1.5 mg / cm 2 to 2 mg / cm 2 .

[0096] Preparation of the negative electrode: A lithium metal sheet with a thickness of 450 μm and a diameter of 15.6 mm was used as the negative electrode;

[0097] Preparation of the separator: The separator was Celgard 2400 with a diameter of 19 mm.

[0098] The sulfur-loaded carbon nanotube positive electrode, separator, and lithium metal negative electrode of this example were assembled and injected with electrolyte to obtain a CR2025 button battery, where the electrolyte-to-sulfur ratio (E / S) was 10 μL / mg.

[0099] Example 7

[0100] Preparation of the electrolyte: Lithium salts LiTFSI and LiNO3 were added to a mixed solution of DOL (dioxolane) and DME (ethylene glycol dimethyl ether) with a volume ratio of 1:1. The concentration of LiTFSI was 1 mol / L, the concentration of LiNO3 was 0.20 mol / L, and an additive bis(trimethylsilyl)sulfide with a concentration of 50 mmol / L was added to obtain the electrolyte. Based on the total weight of the electrolyte, the content of DOL was 41.25 wt%, the content of DME was 34.19 wt%, the content of LiTFSI was 22.64 wt%, the content of LiNO3 was 1.09 wt%, and the content of bis(trimethylsilyl)sulfide was 0.81 wt%.

[0101] Preparation of the positive electrode: Sulfur solid powder and multi-walled carbon nanotubes were mixed in a mass ratio of 8:2, and then heated at 155 °C for 12 hours in an inert atmosphere. The sulfur-loaded carbon nanotubes and the binder PVDF were weighed in a mass ratio of 9:1, added with N-methylpyrrolidone (NMP) and mixed to adjust into a slurry. The slurry was evenly coated on an aluminum foil current collector with a film coater, dried and cut into a pole piece with a diameter of 14 mm and weighed. The sulfur loading was 1.5 mg / cm 2 to 2 mg / cm 2 .

[0102] Preparation of the negative electrode: A lithium metal sheet with a thickness of 450 μm and a diameter of 15.6 mm was used as the negative electrode;

[0103] Preparation of the separator: The separator was Celgard 2400 with a diameter of 19 mm.

[0104] The sulfur-loaded carbon nanotube positive electrode, separator, and lithium metal negative electrode of this example were assembled and injected with electrolyte to obtain a CR2025 button battery, where the electrolyte-to-sulfur ratio (E / S) was 10 μL / mg.

[0105] Comparative Example 1

[0106] Preparation of electrolyte: Lithium salts LiTFSI and LiNO3 were added to a mixed solution of DOL (dioxolane) and DME (ethylene glycol dimethyl ether) with a volume ratio of 1:1. The concentration of LiTFSI was 1 mol / L and the concentration of LiNO3 was 0.20 mol / L to obtain the electrolyte. Based on the total weight of the electrolyte, the content of DOL was 41.60 wt%, the content of DME was 34.48 wt%, the content of LiTFSI was 22.83 wt%, and the content of LiNO3 was 1.09 wt%.

[0107] Preparation of the positive electrode: Sulfur solid powder and multi-walled carbon nanotubes were mixed at a mass ratio of 8:2, and then heated at 155 °C for 12 hours in an inert atmosphere. The carbon nanotubes loaded with sulfur and the binder PVDF were weighed at a mass ratio of 9:1, and N-methylpyrrolidone (NMP) was added and mixed to adjust into a slurry. The slurry was evenly coated on an aluminum foil current collector with a film coater, dried and cut into a pole piece with a diameter of 14 mm and weighed. The sulfur loading was 1.5 mg / cm 2 to 2 mg / cm 2 。

[0108] Preparation of the negative electrode: A lithium metal sheet with a thickness of 450 μm and a diameter of 15.6 mm was used as the negative electrode;

[0109] Preparation of the separator: The separator was Celgard 2400 with a diameter of 19 mm.

[0110] The carbon nanotube positive electrode loaded with sulfur, the separator, and the lithium metal negative electrode of this example were assembled and the electrolyte was injected to obtain a CR2025 button battery, where the liquid-to-sulfur ratio (E / S) was 10 μL / mg.

[0111] Comparative Example 2

[0112] Preparation of electrolyte: Lithium salts LiTFSI and LiNO3 were added to a mixed solution of DOL (dioxolane) and DME (ethylene glycol dimethyl ether) with a volume ratio of 1:1. The concentration of LiTFSI was 1 mol / L and the concentration of LiNO3 was 0.20 mol / L to obtain the electrolyte. Based on the total weight of the electrolyte, the content of DOL was 41.60 wt%, the content of DME was 34.48 wt%, the content of LiTFSI was 22.83 wt%, and the content of LiNO3 was 1.09 wt%.

[0113] Preparation of the separator: The separator was Celgard 2400 with a diameter of 19 mm.

[0114] A lithium metal sheet was used as the working electrode and a fresh copper foil was used as the counter electrode, and then assembled with the electrolyte and the separator into a lithium-copper CR2025 button battery.

[0115] Electrochemical tests were conducted on the button cells obtained in Examples 1-7 and Comparative Examples 1-2. The test results show that in Figures 1 to 3 .

[0116] From Figure 1 , Figure 2 and Figure 4 it can be seen that, by means of the first additive in the electrolyte of the examples, the examples obtain improved capacity and cycling performance relative to the comparative examples.

[0117] After adding the first additive to the electrolyte of the present application, the first additive can not only act on the sulfur positive electrode, but also bring a significant improvement in the electrical properties such as Coulomb efficiency of the lithium positive electrode. From Figure 3 it can be seen that for a lithium copper battery without using a sulfur positive electrode, the electrolyte of the present application containing the first additive can still improve the Coulomb efficiency by acting on the lithium electrode. This proves that the electrolyte according to the present application can rarely act on both the lithium negative electrode and the sulfur positive electrode of a lithium-sulfur battery and simultaneously suppress the undesirable side reactions on the positive electrode side and the negative electrode side, thereby greatly improving the cycling stability of the lithium-sulfur battery.

[0118] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and the embodiments can be changed, substituted, and modified without departing from the spirit, principle, and scope of the present application, and these changes, substitutions, and modifications also fall within the protection scope of the present application.

Claims

1. A lithium-sulfur battery, characterized in that, The lithium-sulfur battery includes a sulfur cathode, a lithium anode, and an electrolyte. Among them, the electrolyte includes a first additive, and the first additive includes at least one of (phenylthio)trimethylsilane, (ethylthio)trimethylsilane, and bis(trimethylsilyl)sulfide.

2. The lithium-sulfur battery according to claim 1, characterized in that, The electrolyte further includes an ether solvent, and the ether solvent includes at least one of triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dioxolane, ethylene glycol dimethyl ether, dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran.

3. The lithium-sulfur battery according to claim 2, characterized in that, The ether solvent includes dioxolane and ethylene glycol dimethyl ether. Among them, based on the total weight of the electrolyte, the content of dioxolane is 20% by weight to 80% by weight, and the content of ethylene glycol dimethyl ether is 20% by weight to 80% by weight.

4. The lithium-sulfur battery according to claim 3, characterized in that, The volume ratio of the dioxolane to the ethylene glycol dimethyl ether is 0.5:1 to 2:

1.

5. The lithium-sulfur battery according to claim 1, characterized in that, Based on the total weight of the electrolyte, the content of the first additive is 0.1% by weight to 2% by weight.

6. The lithium-sulfur battery according to claim 1, characterized in that, The electrolyte further includes lithium nitrate and lithium bis(trifluoromethanesulfonyl)imide. And in the electrolyte, the content of lithium nitrate is 0.1% by weight to 2% by weight, and the content of lithium bis(trifluoromethanesulfonyl)imide is 10% by weight to 35% by weight.

7. The lithium-sulfur battery according to claim 6, characterized in that, In the electrolyte, the content of lithium nitrate is 0.5% by weight to 1.5% by weight, and / or the content of lithium bis(trifluoromethanesulfonyl)imide is 15% by weight to 25% by weight.

8. The lithium-sulfur battery according to claim 1, characterized in that, The sulfur cathode includes a cathode current collector and a cathode active material layer. The cathode active material layer includes sulfur and a conductive material. Among them, based on the total weight of the cathode active material layer, the content of sulfur is 60% by weight to 95% by weight, and the content of the conductive material is 5% by weight to 40% by weight.

9. The lithium-sulfur battery according to claim 1, characterized in that, The lithium anode is made of lithium metal, and / or the liquid-sulfur ratio of the lithium-sulfur battery is 2 μL / mg to 10 μL / mg.

10. The lithium-sulfur battery according to claim 1, characterized in that, Based on the total weight of the electrolyte, the content of the first additive is 0.1% by weight to 2% by weight. The electrolyte further includes a solvent and a lithium salt. The solvent includes dioxolane and ethylene glycol dimethyl ether. The lithium salt includes lithium nitrate and lithium bis(trifluoromethanesulfonyl)imide. Based on the total weight of the electrolyte, the content of dioxolane is 30% by weight to 60% by weight, the content of ethylene glycol dimethyl ether is 30% by weight to 60% by weight, the content of lithium nitrate is 0.5% by weight to 1.5% by weight, and the content of lithium bis(trifluoromethanesulfonyl)imide is 15% by weight to 25% by weight.

11. An electronic device, characterized in that, The electronic device includes the lithium-sulfur battery according to any one of claims 1 to 10.

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