ORGANIC SULFUR CATHODS AND LITHIUM SULFUR ACCUMULATORS CONTAINING THESE,

Abstract

Low-porosity, reduced-surface-area organosulfur cathodes for lithium-sulfur batteries generally comprise sulfurized poly(1,2-butadiene), wherein the sulfurized poly(1,2-butadiene) is a reaction product of a poly(1,2-butadiene) monomer and cyclic octahedral sulfur, conductive carbon, and a binder. Optionally, the reaction product may further comprise comonomers incorporating alkene functionality. The comonomers may include one or more sulfide groups selected from the group consisting of sulfide, disulfide, and polysulfide.

Description

INTRODUCTION

[0001] The present disclosure relates generally to lithium-sulfur accumulators and in particular to organosulfur cathodes, lithium-sulfur accumulators containing them, and processes for their manufacture, wherein the organosulfur cathodes, which have low porosity and a reduced surface area, are formed by reaction of poly(1,2-butadiene) with sulfur.

[0002] Lithium-sulfur batteries are known to have a high theoretical specific energy of approximately 2600 Wh / kg. Specific energy is generally defined as the ratio between the energy output of a cell or battery and its weight. The term specific energy is synonymous with gravimetric energy density. Such batteries can be used in commercial applications such as portable notebooks and computers, digital and mobile phones, personal digital assistants, and the like, as well as in higher energy-demand applications such as hybrid and electric vehicles, and in military or defense applications.

[0003] Lithium-sulfur batteries generally comprise a lithium anode, an electrolyte, a porous separator, and a sulfur cathode. The discharge of a lithium-sulfur battery generally involves the conversion of sulfur to lithium polysulfide (Li₂Sn), with the number of n varying from 8 to 2, followed by the reduction of the polysulfides to solid lithium disulfide (Li₂S₂) and finally to lithium sulfide (Li₂S). The soluble polysulfide (Li₂Sn, 3 <n<8) im Elektrolyten kann entweder auf der Anode oder auf der Kathode als Li2S abgeschieden werden. Wenn Li2S auf der Kathode abgeschieden wird, verstopft es die Strukturporen während mehrerer Lade- / Entladezyklen. Darüber hinaus kommt es aufgrund der unterschiedlichen Molvolumina von S und Li2S zu Volumenänderungen, die sich auf die Morphologie der Kathode auswirken. Dies führt zu einer Abnahme der Kapazität bei zunehmender Lebensdauer.During the charging process, the Li₂S is oxidized from the cathode side to higher polysulfides (e.g., S₈), which can migrate and are reduced to lower polysulfides by reaction at the anode. Thus, the soluble polysulfides can oscillate back and forth between the cathode and anode, which in lithium-sulfur chemistry leads to overcharging and a low coulombic efficiency.

[0004] Conventional sulfur cathodes are typically fabricated using substantial amounts of a conductive carbon host material (up to 50 wt%) to compensate for sulfur's low electronic conductivity. However, the addition of large amounts of conductive filler reduces the specific energy at the cell level. The conductive carbon host material can be infused using methods such as melt diffusion or by casting an aqueous solution of the carbon host material, a binder, and sulfur, followed by drying with sulfur. However, the porosity is often very high, which, due to the large surface area of ​​the active material (100–1500 m² / g), affects the energy density, potentially requiring higher amounts of binder and thus reducing the cathode's efficiency.Due to their large surface area, these sulfur cathodes require large quantities of electrolyte to adequately wet all cathode surfaces, increasing the cell's weight and reducing its specific energy. Furthermore, these types of sulfur cathodes naturally produce large amounts of polysulfides during cycling.

[0005] Therefore, it is desirable to reduce the problems arising from the use of sulfur cathodes in lithium-sulfur batteries manufactured with conductive carbon host materials. SUMMARY

[0006] In an exemplary embodiment, an organosulfur cathode for a lithium-sulfur battery or lithium-sulfur cell comprises sulfurized poly(1,2-butadiene) in an amount of approximately 70 wt.% to approximately 98 wt.%. The sulfurized poly(1,2-butadiene) is a reaction product of sulfur and a poly(1,2-butadiene) monomer. The rubber monomer of poly(1,2-butadiene) is present in an amount ranging from approximately 5 wt.% to approximately 60 wt.%, and the sulfur is present in an amount ranging from approximately 40 wt.% to approximately 60 wt.% of the reaction product. The sulfur may be cyclic octoculfur. The organosulfur cathode further comprises conductive carbon in an amount ranging from approximately 1 wt.% to approximately 20 wt.% and binder in an amount ranging from approximately 0.5 wt.% to approximately 20 wt.%, the wt.% referring to the total weight of the organosulfur cathode.The binder is present in amounts greater than 0.5 wt% to less than 2 wt%. The conductive carbon comprises carbon nanotubes.

[0007] In one aspect, the organosulfur cathode exhibits a porosity of approximately 20% to 60%. In other aspects, the organosulfur cathode exhibits a porosity of less than 40%.

[0008] The reaction product may also comprise a comonomer with an alkene functionality. The alkene functionality may be vinyl or allyl. The comonomer further comprises sulfur groups selected from the group consisting of sulfides, disulfides, and polysulfides. In these embodiments, the rubber monomer of poly(1,2-butadiene) is present in an amount ranging from approximately 5 wt% to approximately 60 wt%, the comonomer comprising the alkene functionality is present in an amount ranging from approximately 5 wt% to approximately 60 wt%, and the sulfur is present in an amount ranging from approximately 40 wt% to approximately 60 wt% of the reaction product.

[0009] In one or more embodiments, a lithium-sulfur accumulator or a lithium-sulfur cell comprises a cathode current collector, an organosulfur cathode on the cathode current collector with a porosity in an amount in the range of approximately 20% to approximately 60%, wherein the organosulfur cathode comprises sulfurized poly(1,2-butadiene) in an amount in the range of approximately 70 wt% to approximately 98 wt%, wherein the sulfurized poly(1,2-butadiene) is a reaction product of sulfur and a poly(1,2-butadiene) monomer, an anode current collector, a lithium or silicon anode on the anode current collector, a microporous polymeric separator between the organosulfur cathode and the anode, and an electrolyte material between the anode and the organosulfur cathode.

[0010] In one or more aspects, the organosulfur cathode exhibits a porosity of less than 40%.

[0011] The binder can be present in amounts greater than 0.5 wt.% to less than 2 wt.%.

[0012] The reaction product further comprises a comonomer with an alkene functionality. The alkene functionality comprises a vinyl or an allyl functionality. The comonomer may also comprise sulfur groups selected from the group consisting of sulfides, disulfides, and polysulfides.

[0013] In other embodiments, a lithium-sulfur battery or lithium-sulfur cell comprises a cathode current collector that is externally connected to a load. The cathode current collector may include aluminum. An organosulfur cathode is located on the cathode current collector and has a porosity in the range of approximately 20% to approximately 60%. The organosulfur cathode comprises sulfurized poly(1,2-butadiene) in an amount in the range of approximately 70 wt% to approximately 98 wt%, wherein the sulfurized poly(1,2-butadiene) is a reaction product of a poly(1,2-butadiene) monomer in an amount in the range of approximately 5 wt% to approximately 60 wt% and of cyclic octatomic sulfur in an amount in the range of approximately 40 wt% to approximately 60 wt% of the reaction product. The organosulfur cathode also includes conductive carbon in an amount ranging from approximately 1 wt% to approximately 20 wt%.-% and binder in an amount ranging from approximately 0.5 wt% to approximately 20 wt%, the wt% referring to the total amount of the organosulfur cathode. An anode current collector externally connected to the load, the anode current collector being made of one or more materials selected from the group consisting of copper, stainless steel, nickel, iron, titanium, tin (Sn), and alloys thereof. A lithium or silicon anode is located on the anode current collector, and a porous polymer separator is placed between the cathode and the anode.

[0014] The reaction product may further comprise a comonomer with an alkene functionality and one or more sulfide groups selected from the group consisting of sulfide, disulfide and polysulfide.

[0015] The aforementioned features and advantages, as well as other features and advantages of the disclosure, are readily apparent from the following detailed description in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Further features, advantages and details are listed only as examples in the following detailed description, which refers to the drawings in which: Fig. 1 schematically illustrates a lithium-sulfur cell according to one or more embodiments of the present disclosure, Fig. 2. A microscopic structure of the ground rubber made from sulfurized poly(1,2-butadiene) according to one or more embodiments of the present disclosure is illustrated. Fig. 3. A microscopic structure of an exemplary organosulfur cathode according to one or more embodiments of the present disclosure is illustrated. Fig. 4 graphically illustrates the charge-discharge cycle curves for a lithium-sulfur cell according to one or more embodiments of the present disclosure, Fig. 5 graphically illustrates the charge-discharge profiles after 1 cycle and 10 cycles for a lithium-sulfur cell with a cathode made of sulfurized poly(1,2-butadiene) according to one or more embodiments of the present disclosure, Fig. 6 graphically illustrates the charge-discharge profiles after 1 cycle and 10 cycles for a lithium-sulfur cell with a cathode made of sulfurized poly(1,2-butadiene) according to one or more embodiments of the present disclosure and Fig. Figure 7 graphically illustrates the charge-discharge profiles after 1 cycle and 10 cycles for a lithium-sulfur cell with a cathode made of sulfurized poly(1,2-butadiene) / squalene according to one or more embodiments of the present disclosure. DETAILED DESCRIPTION

[0017] The following description is merely exemplary and is not intended to limit the present disclosure, its application or use.

[0018] According to exemplary embodiments, lithium-sulfur battery or cell designs include an organosulfur cathode formed by the reaction of poly(1,2-butadiene) with sulfur at an elevated temperature to form the organosulfur cathode, which comprises an active material of sulfurized 1,2-butadiene. Optionally, the reaction may further include comonomers comprising alkenes such as allyl, vinyl, and / or similar functionalities, the comonomers further comprising sulfide, disulfide, and / or polysulfide groups to further increase the sulfur loading. In relation to previous lithium-sulfur battery or cell designs,Cell designs incorporating sulfur cathodes formed by infusing sulfur with relatively high amounts of a conductive carbon host material and a binder result in increased cycling stability and efficiency for lithium-sulfur cells with the organosulfur cathode, which includes the active material of sulfurized 1,2-butadiene as disclosed herein. The organosulfur cathodes with the active material of sulfurized 1,2-butadiene exhibit a high sulfur loading, a relatively small surface area, and low porosity, and can be manufactured with minimal binder. The higher sulfur loading reduces the electrolyte-to-sulfur ratio (E / S), which significantly improves the specific energy obtained from the lithium-sulfur battery or cell designs with the organosulfur cathode.

[0019] Conventional techniques for manufacturing lithium-sulfur batteries or lithium-sulfur cells may be described in detail herein, but this is not required. Furthermore, the various tasks and process steps described herein may be integrated into a more comprehensive procedure or process with additional steps or functions not described in detail here. In particular, several steps in the manufacture of lithium-sulfur batteries or lithium-sulfur cells are known, so for the sake of brevity, many conventional steps are only briefly mentioned here or omitted entirely, without providing the known process details.

[0020] Spatially relative terms, such as "below," "under," "lower," "above," "upper," and the like, may be used here for the sake of simplicity to describe the relationship of an element or feature to one or more other elements or features, as illustrated in the figures. It is understood that these spatially relative terms are intended to include different orientations of the device or system in use or operation, in addition to the orientation shown in the figures. For example, if the accumulator in the figures is turned upside down, elements described as "below" or "underneath" other elements or features would then be oriented "above" the other elements or features. Thus, the term "below" can encompass both the orientation above and the orientation below.The device may be oriented differently (rotated by 90 degrees or in other orientations) and the spatially relative descriptors used here may be interpreted accordingly.

[0021] The following definitions and abbreviations are to be used for the interpretation of the claims and the description. As used herein, the terms "comprises," "comprising," "includes," "including," "has," "exhibiting," "contains," or "containing," or any other variation thereof, are to be understood as non-exclusive inclusions. For example, a composition, mixture, process, method, article, or apparatus comprising a list of elements is not necessarily limited to those elements but may also include other elements not expressly listed or belonging to such composition, mixture, process, method, article, or apparatus.

[0022] The terms "a," "an," and "one" do not imply a limitation of quantity, but rather denote the presence of at least one of the elements mentioned. The term "or" means "and / or," unless the context clearly indicates otherwise. When the entire description refers to "an aspect," this means that a specific element (e.g., a feature, a structure, a step, or a property) described in connection with that aspect is contained in at least one of the aspects described herein and may or may not be present in other aspects. It is understood that the described elements can be combined in any suitable way across the various aspects. Additionally, the terms "upper," "lower," "above," "below," "left," and "right," as well as their derivatives, refer to the described structures as they are oriented in the figures of the drawings.The same reference symbols in the different figures can refer to the same component or a part thereof.

[0023] When an element such as a layer, film, area, or substrate is described as lying "on" another element, it can lie directly on top of the other element, or there can be intermediate elements. Conversely, when an element is described as lying "directly on" another element, there are no intermediate elements.

[0024] Unless otherwise stated herein, all testing standards are the latest standard in force on the filing date of this application or, if priority is claimed, on the filing date of the earliest priority application in which the testing standard appears.

[0025] Unless otherwise defined, the technical and scientific terms used herein have the same meanings as generally understood by a person skilled in the field to which this disclosure relates.

[0026] With the following reference to Fig. Figure 1 schematically shows an exemplary lithium-sulfur battery or lithium-sulfur cell in a cross-sectional view, generally designated by reference numeral 10. The lithium-sulfur battery or lithium-sulfur cell 10 generally comprises an organosulfur cathode 12, which includes an active material of sulfurized 1,2-butadiene, a lithium-containing or silicon-containing anode 14, a polymeric separator 16 between the organosulfur cathode 12 and the anode 14, and an electrolyte material 18 between them. The polymeric separator 16 is electrically non-conductive and permeable to ions via the electrolyte material 18, which fills its open pores. The separator 16 can, for example, consist of a microporous polypropylene or polyethylene film. The anode 14 is connected to an anode current collector 20, and the organosulfur cathode 12 is connected to a cathode current collector 22.

[0027] The poles extending from the respective current collectors 20, 22 (not shown) can be connected in a circuit to either discharge the lithium-sulfur battery or lithium-sulfur cell 10 by connecting a load (not shown) in the circuit, or to charge the lithium-sulfur battery or lithium-sulfur cell 10 by connecting an external power source (not shown). The electrolyte material 18 is a lithium salt and is passed between the organosulfur cathode 12 and the lithium- or silicon-containing anode 14 during cycling.

[0028] Lithium-sulfur accumulators or lithium-sulfur cells 10, comprising the organosulfur cathodes 12 described herein, can be designed in four general ways: (1) as small solid cylinders, such as batteries for laptops, (2) as large solid cylinders with threaded terminals, (3) as soft, flat pouches, such as batteries for mobile phones with flat terminals that are flush with the body of the accumulator, and (4) in plastic housings with large terminals in the form of aluminum and copper sheets, such as battery packs for motor vehicles.

[0029] The lithium-sulfur batteries, or lithium-sulfur cells 10, can optionally include a wide range of other components known in engineering, such as sealing rings, gaskets, terminal caps, and so on, for performance-related or other practical purposes. The lithium-sulfur batteries, or lithium-sulfur cells 10, can also be connected in a suitably designed combination of series and parallel electrical circuits with other similar batteries to generate a higher output voltage and current when the load requires it.

[0030] In one or more embodiments, the organosulfur cathode 12 is formed by reacting sulfur, such as cyclic octatomic sulfur (S8), with poly(1,2-butadiene), which is relatively inexpensive and readily available, at an elevated temperature of approximately 180 °C to 200 °C, for example to form a rubber compound of sulfurized poly(1,2-butadiene), as generally shown below in Scheme I.

[0031] In one or more embodiments, the reaction further includes one or more comonomers comprising alkenes such as allyl, vinyl, and / or similar functional groups, wherein the comonomers may further include sulfide, disulfide, and / or polysulfide groups. For example, squalene, divinylbenzene, diallyl disulfide, or the like may be added to the reaction mixture with the poly(1,2-butadiene) and sulfur to produce the sulfurized poly(1,2-butadiene) rubber compound. The specific sulfurized poly(1,2-butadiene) rubber compound obtained is not limited to the one shown above and generally depends on the specific comonomers added to the reaction mixture.

[0032] The formulation of the rubber compound from sulfurized poly(1,2-butadiene) can include the reaction of the poly(1,2-butadiene) in an amount in the range of approximately 5 wt% to approximately 60 wt% of the reactants, sulfur in an amount in the range of approximately 40 wt% to 95 wt% of the reactants, and optionally the comonomers in an amount in the range of approximately 5 wt% to approximately 60 wt% of the reactants.

[0033] The organosulfur cathode 12 can be formed by mixing a rubber compound consisting of sulfurized poly(1,2-butadiene) in an amount ranging from approximately 70 wt.% to approximately 98 wt.%, conductive carbon in an amount ranging from approximately 1 wt.% to approximately 20 wt.%, and a binder in an amount ranging from approximately 0.5 wt.% to approximately 20 wt.%, where the wt. percent refer to the total weight of the composition. In other embodiments, the rubber compound consists of sulfurized poly(1,2-butadiene) in an amount ranging from approximately 75 wt.% to approximately 90 wt.%, the conductive carbon in an amount ranging from approximately 1 wt.% to approximately 15 wt.%, and the binder in an amount ranging from approximately 0.5 wt.% to approximately 10 wt.%. In other formulations, the rubber compound consists of sulfurized poly(1,2-butadiene) in an amount of approximately 80 wt.In some formulations, the conductive carbon is present in an amount ranging from approximately 1% to approximately 10% by weight, and the binder in an amount ranging from approximately 0.5% to approximately 5% by weight. In other formulations, the binder is present in an amount ranging from approximately 0.5% to 2% by weight.

[0034] In one or more embodiments, the rubber compound made of sulfurized poly(1,2-butadiene) is milled before the formulation of the cathode composition, whereby the average particle size can be approximately 5 micrometers (µm) to approximately 10 µm.

[0035] In one or more embodiments, the conductive carbon is formed from carbon nanotubes (CNTs), which can include single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), multi-walled carbon nanotubes (MWCNTs), or combinations thereof. Carbon nanotubes are generally cylindrical carbon structures with diameters in the nanometer or nm range (typically a few nanometers) and lengths in the micrometer to millimeter range. SWCNTs specifically refer to nanotubes consisting of a single graphene layer rolled into a seamless cylinder, while DWCNTs comprise two concentric cylindrical layers, and multi-walled CNTs refer to more than two concentric cylindrical layers.Suitable SWCNTs, DWCNTs, and multi-walled carbon nanotubes generally have a length greater than approximately 1 micrometer (µm), a diameter of approximately 1 nm to approximately 6 nm, and a thickness of less than 0.1 nanometers (nm), although larger or smaller diameters and thicknesses can also be used. Alternatively, vapor-phase grown carbon with the above dimensions can be used. In one or more embodiments, mixtures of the carbon nanotubes can be blended with other types of carbon additive materials in the precursor solution (e.g., Super P™, commercially available from TIMCAL; Ketjenblack, a type of acetylene black commercially available from Cabot Corporation; acetylene black; graphite conductors such as KS-6, KS-15, SO, SEG-6, and the like; and graphene).

[0036] In practice, an aqueous slurry of the aforementioned components can be mixed, cast, and dried at elevated temperature on a suitable cathode current (e.g., aluminum foil). The resulting porosity of the cast organosulfur cathode is relatively low compared to prior art sulfur cathodes, allowing for a higher volumetric energy density and a smaller surface area for increased sulfur loading and improved processability. Consequently, less electrolyte is required, resulting in a lower weight of the cells or accumulators. In one or more embodiments, the organosulfur cathodes of this disclosure exhibit a porosity of approximately 20% to approximately 60%. In other embodiments, the porosity ranges from approximately 30% to approximately 55%, and in still other embodiments, the porosity ranges from approximately 40% to approximately 50%.

[0037] The cathode current collector 22 can be made of aluminium or another suitable electrically conductive material.

[0038] The anode current collector 20 consists of one or more materials selected from a group consisting of copper, stainless steel, nickel, iron, titanium, tin (Sn) and alloys thereof.

[0039] In one or more embodiments, the anode 14 has a base electrode material such as lithium metal, which can serve as an active anode material.

[0040] The lithium metal can be present, for example, in the form of a lithium metal foil or a thin lithium film that has been deposited onto the anode current collector.

[0041] Lithium metal can also be in the form of a lithium alloy, such as a lithium-tin alloy, a lithium-aluminium alloy, a lithium-magnesium alloy, a lithium-zinc alloy, a lithium-silicon alloy (which is used as the anode in a sulfur-silicon battery), or a combination of these alloys.

[0042] The anode 14 can alternatively comprise any lithium host material capable of undergoing sufficient lithium insertion and removal while functioning as anode 14 of the lithium-sulfur accumulator 10.

[0043] Examples of host materials include electrically conductive carbon-containing materials such as carbon, graphite, carbon nanotubes, graphene, and petroleum coke. Mixtures of such host materials can also be used.

[0044] Graphite is frequently used as an anode because it is inexpensive, has favorable lithium insertion and removal properties, is relatively unreactive, and can store lithium in quantities that result in a relatively high energy density.

[0045] Commercial forms of graphite that can be used to manufacture the anode 14 are available, for example, from Timcal Graphite & Carbon, based in Bodio, Switzerland; Lonza Group, based in Basel, Switzerland; Superior Graphite, based in Chicago, Illinois, USA; or Hitachi Chemical Company, based in Japan.

[0046] In other embodiments, the anode 14 can be a porous silicon anode containing a lithium-silicon alloy, e.g. made with silicon nanoparticles from high-purity silicon or with silicon nanowires.

[0047] The anode 14 may further comprise a polymeric binder in sufficient quantity to structurally hold the lithium or silicon host material together. Non-restrictive examples of suitable binder polymers include polyvinylidene fluoride, polyacrylonitrile, polyethylene oxide, polyethylene, polypropylene, polytetrafluoroethylene, polybutadiene, polystyrene, polyalkyl acrylates and methacrylates, ethylene propylene diene monomer copolymer rubber (EPDM), styrene-butadiene copolymers, and mixtures of such polymers. Carboxymethylcellulose is a preferred binder for silicon-containing anodes.

[0048] The anode current collector 20 can be made of copper or another suitable electrically conductive material known to those skilled in the art.

[0049] The polymeric separator 16 is microporous and enables the ion transport of lithium ions between the organosulfur cathode 12 and the anode 14. Non-restrictive examples of suitable separator materials include polyolefins, which may be linear or branched homopolymers, random or block copolymers, comprising polyethylene, polypropylene, and mixtures and copolymers thereof, polyethylene terephthalate, polyvinylidene fluoride, polyamides (nylons), polyurethanes, polycarbonates, polyesters, polyetheretherketones (PEEK), polyethersulfones (PES), polyimides (PI), polyamideimides, polyethers, polyoxymethylene (acetal), polybutylene terephthalate, polyethylene naphthenate, polybutene, acrylonitrile butadiene styrene copolymers (ABS), styrene copolymers, polymethyl methacrylate, polyvinyl chloride, polysiloxane polymers (such as polydimethylsiloxane (PDMS)), and polybenzimidazole. Polybenzoxazole, polyphenylene, polyarylene ether ketones, polyperfluorocyclobutane, polytetrafluoroethylene (PTFE),Polyvinylidene fluoride copolymers and terpolymers, polyvinylidene chloride, polyvinyl fluoride, liquid crystalline polymers, polyaramides, polyphenylene oxide and combinations thereof.

[0050] The microporous polymeric separator 16 can be a single layer of woven or nonwoven fabric or a multi-layer laminate, produced either by a dry or wet process.

[0051] In a dry process, a polymer film is stretched to create holes permeable to lithium ions between crystalline regions.

[0052] In a wet process, a material is dissolved or otherwise removed from the polymer film, leaving holes permeable to lithium ions.

[0053] In one example, the polymeric separator can consist of a single layer of polyolefin.

[0054] In another example, a single layer made of one or a combination of any of the polymers from which the microporous polymeric separator 16 can be formed (e.g., the polyolefin or one or more of the other polymers listed above for separator 16) can be used. In certain embodiments, a nonwoven fabric is preferred due to its random fiber orientation.

[0055] As a further example, several discrete layers of similar or different polyolefins or other polymers can be assembled for the separator 16 during the fabrication of the microporous polymeric separator 16. In one example, a discrete layer of one or more of the polymers can be deposited onto a discrete layer of polyolefin for the separator 16.

[0056] Furthermore, the polyolefin layer (and / or another polymer) and any other optional polymer layers can be incorporated as a fiber layer into the microporous polymeric separator 16 to help impart suitable structural and porosity properties to the microporous polymeric separator 16.

[0057] Typically, the polymer separators 16 are approximately 25 micrometers thick.

[0058] The electrolyte material 18 can be a liquid or a solid. Liquid electrolytes generally comprise one or more lithium compounds, usually in the form of a lithium salt in an organic solvent.

[0059] The concentration of the lithium salt in the electrolyte material 18 can be in a range between 0 and 4 M, and preferably in a range between 0.05 and 1.5 M. Non-limiting examples include LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiSbF6, LiAsF6 (lithium hexafluoroarsenate), LiClO4 (lithium perchlorate), LiCF3SO3 (lithium trifluorosulfonate), LiN(C2F5SO2)2 (lithium bis(perfluoroethylsulfonyl)imide), and Li(CF3SO2)2N (lithium bis(trifluoromethylsulfonyl)imide or LiTFSI).

[0060] The organic solvent can be selected from acetals, ketals, sulfones, acyclic ethers, cyclic ethers, glymenes, polyethers and dioxolanes, as well as mixtures thereof.

[0061] Examples of acyclic ethers include dibutyl ether, dimethoxymethane, trimethoxymethane, dimethoxyethane (DME), diethoxyethane, 1,2-dimethoxypropane and 1,3-dimethoxypropane.

[0062] Examples of cyclic ethers that can be used include tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,3-dioxolane and trioxane.

[0063] Examples of polyethers that can be used include diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme, TEGDME), tetraethylene glycol dimethyl ether (tetraglyme), higher glyme, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, dipropylene glycol dimethyl ether, and butylene glycol ether.

[0064] Examples of sulfones include sulfolane, 3-methylsulfolane and 3-sulfolene.

[0065] Solid-state electrolytes generally include a pseudobinary sulfide, a pseudoternal sulfide, a pseudoquaternary sulfide, a halide-based solid-state electrolyte and / or a hydride-based solid-state electrolyte.

[0066] Examples of pseudobinary sulfides include the Li2S-P2S5 system (Li3PS4, Li7P3S11 and Li9.6P3S12), the Li2S-SnS2 system (Li4SnS4), the Li2S-SiS2 system, the Li2S-GeS2 system, the Li2S-B2S3 system, the Li2S-Ga2S3 system, the Li2S-P2S3 system, and the Li2S-Al2S3 system. Examples of pseudoternary sulfides include the Li2O-Li2S-P2S5 system, the Li2S-P2S5-P2O5 system, the Li2S-P2S5-GeS2 system (Li3,25Ge0,25P0,75S4 and Li10GeP2S12), the Li2S-P2S5-LiX (X = F, Cl, Br, I) system (and Li4PS4I), the Li2S-As2S5-SnS2 system (Li3,833Sn0,833As0,166S4), the Li2S-P2S5-Al2S3 system, the Li2S-LiX-SiS2 (X = F, Cl, Br, I) system and 0,4LiI·0,6Li4SnS4 and Li11Si2PS12. Examples of pseudoquaternary sulfides include the Li2O-Li2S-P2S5-P2O5 system, Li9,54Si1,74P1,44S11,7Cl0,3, Li7P2,9Mn0,1S10,710,3 and Li 10,35[Sn0,27Si 1,08] P1,65S12.

[0067] Examples of halide-based solid electrolytes include Li3YCl6, Li3InCl6, Li3YBr6, Lil, Li2CdCl4, Li2MgCl4, Li2CdI4, Li2ZnI4, and Li3OCl. Examples of hydride-based solid electrolytes include LiBH4, LiBH4-LiX (X = Cl, Br, or I), LiNH2, Li2NH, LiBH4-LiNH2, and Li3AlH6.

[0068] In other examples, other types of solid electrolytes with low grain boundary resistance can also be used.

[0069] The lithium-sulfur battery, or lithium-sulfur cell 10, with the organosulfur cathode 12, can generate a useful electric current during battery discharge through reversible electrochemical reactions that occur when an external circuit is closed to connect the organosulfur cathode 12 and the anode 14. The average chemical potential difference between the organosulfur cathode 12 and the anode 14 drives the electrons generated by the oxidation of lithium at the anode 14 through an external circuit to the organosulfur cathode 12. Simultaneously, the lithium ions generated at the anode 14 are transported by the electrolyte material 18 through the microporous polymeric separator 16 to the organosulfur cathode 12.Simultaneously with the entry of Li+ ions into the electrolyte material 18 at the anode 14, Li+ ions from the electrolyte material 18 recombine with electrons at an interface between the electrolyte material 18 and the organosulfur cathode 12, and the lithium concentration in the organosulfur cathode 12 increases.

[0070] The lithium-sulfur battery or lithium-sulfur cell 10 can be recharged at any time by connecting an external power source to the lithium-sulfur battery or lithium-sulfur cell 10 to reverse the electrochemical reactions that occur during the discharge of the battery and restore the electrical energy.

[0071] The connection of the external power source to the lithium-sulfur battery or the lithium-sulfur cell 10 forces the otherwise non-spontaneous oxidation of the lithium polysulfides at the organosulfur cathode 12 to generate electrons and lithium ions.

[0072] The electrons, which flow back to the anode 14 via an external circuit, and the lithium ions, which are transported back to the anode 14 from the electrolyte material 18 via the polymeric separator 16, recombine at the anode 14 and replenish it with lithium, which is consumed in the next discharge cycle of the battery.

[0073] The cyclization of the organosulfur cathode, which comprises the sulfurized poly(1,2-butadiene), generally proceeds as follows:

[0074] Fig. Figure 2 illustrates a microscopic microstructure of the ground rubber made from sulfurized poly(1,2-butadiene) produced according to the reaction scheme shown in Formula I, comprising 73 wt% sulfur and 27 wt% polymer. The higher sulfur loading compared to prior art sulfur-infused cathodes (which typically include significant amounts of conductive carbon and binder) increases the cathode's areal capacity (mAh / cm²), thus advantageously maximizing the cell's specific energy and representing a significant improvement over prior art sulfur-infused cathodes.

[0075] Fig. Figure 3 illustrates a microscopic structure of an exemplary organosulfur cathode with a total weight of 6.38 milligrams (mg) cast onto an aluminum foil substrate 15 µm thick (i.e., cathode current collector). The organosulfur cathode was cast from an aqueous slurry of 5.74 mg sulfurized poly(1,2-butadiene) rubber, 0.561 mg MWCNTs, and 0.077 mg CMC binder. The cathode loading of 90:8.8:1.2 provided a stored energy potential of approximately 4.19 mAh.

[0076] Using the aforementioned organosulfur cathode and cathode current collector, a button cell was fabricated with a 1.5 mm thick space spring, a microporous Celgard® polypropylene separator, and a 100 µm thick lithium foil as the anode. The electrolyte material was a mixture of 1,3-dioxolane (DOL) and dimethoxyethane (DME) with 1 molar (M) LiTFSi and 3% LiNO3. The rate capacity of the fabricated cell was 3.05 mAh / cm².

[0077] Fig. Figure 4 shows the charge / discharge curves 401 and 402, respectively, which were generated for the lithium-sulfur cell with the organosulfur cathode comprising sulfurized poly(1,2-butadiene), conductive carbon in the form of MWCNT, and CMC binder in a weight ratio of 90:8.8:1.2, and which exhibited excellent rate capacity. As shown, the cell has a high rate capacity and was able to generate a considerable amount of power; that is, it suffers from low polarization (voltage drop) even at high current loads.

[0078] The charging capacity is determined by the C-rate, which generally defines the time required for charging or discharging. The charging or discharging time of the C-rate varies relative to the rated power, with 1C corresponding to 60 minutes. Higher C-rates, such as 5C, 10C, or 20C, represent much faster charging / discharging rates.

[0079] In Fig. 5 is a charge / discharge profile for the lithium-sulfur cell, which is in Fig. As described in Figure 4, the results after cycles 1 and 10 are shown, with the organosulfur cathode comprising sulfurized poly(1,2-butadiene) rubber, MWCNTs, and CMC binder in a loading ratio of 80:18.8:1.2. As shown, the charge and discharge curves were relatively flat, indicating that the accumulator voltage remained relatively constant at the different C rates. Specific capacities of approximately 1100 mAh / mgS were observed after cycle 1 and approximately 800 mAh / mgS after cycle 10.

[0080] In Fig. 6 is a charge / discharge profile for the lithium-sulfur cell, which is in Fig. As described in Figure 4, the organosulfur cathode comprised sulfurized poly(1,2-butadiene) rubber, MWCNTs, and CMC binder in a loading ratio of 87:8:5. Specific capacities of approximately 900 mA / mgS were observed after cycle 1 and approximately 750 mA / mgS after cycle 10.

[0081] In Fig. 7 is a charge / discharge profile for the lithium-sulfur cell, which is in Fig. As described in Figure 4, the organosulfur cathode comprised sulfurized poly(1,2-butadiene) rubber with 5 wt% squalene as a copolymer, MWCNTs, and CMC binders in a loading ratio of 90 : 8.8 : 1.2. Specific capacities of approximately 1100 mAh / mgS were observed after cycle 1 and approximately 800 mAh / mgS after cycle 10.

[0082] While the above revelation was described with reference to exemplary manifestations, it is known among those skilled in the art that various modifications can be made and equivalent elements substituted without altering its scope. Furthermore, many changes can be made to adapt a particular situation or material to the teachings of the revelation without deviating from its essential scope. Therefore, the present revelation is not intended to be limited to the specific manifestations disclosed, but rather to encompass all manifestations that fall within its scope.

Claims

[1] Organosulfur cathode for a lithium-sulfur accumulator or a lithium-sulfur cell, wherein the organosulfur cathode comprises: sulfurized poly(1,2-butadiene) in an amount ranging from about 70 wt% to about 98 wt%, wherein the sulfurized poly(1,2-butadiene) is a reaction product of sulfur and a poly(1,2-butadiene) monomer, conductive carbon in an amount ranging from about 1 wt% to about 20 wt%, wherein the conductive carbon comprises carbon nanotubes and Binder in an amount ranging from about 0.5 wt% to about 20 wt%, wherein the weight percentages are based on the total weight of the organosulfur cathode. [2] The organosulfur cathode of claim 1, wherein the organosulfur cathode has a porosity of greater than about 20% to less than about 60%. [3] The organosulfur cathode of claim 1, wherein the binder is present at greater than about 0.5 wt% to less than 2 wt%. [4] The organosulfur cathode of claim 1, wherein the reaction product further comprises a comonomer having an alkene functionality. [5] The organosulfur cathode of claim 4, wherein the comonomer further comprises sulfur groups selected from the group consisting of sulfides, disulfides, and polysulfides. [6] The organosulfur cathode of claim 1, wherein the poly(1,2-butadiene) rubber monomer is present in an amount ranging from about 5% to about 60% by weight and the sulfur is present in an amount ranging from about 40% to about 60% by weight of the reaction product. [7] Lithium-sulfur accumulator or lithium-sulfur cell construction, comprising: a cathode current collector, an organosulfur cathode on the cathode current collector having a porosity in the range of about 20% to about 60%, wherein the organosulfur cathode comprises a sulfurized poly(1,2-butadiene) in an amount in the range of about 70 wt% to about 98 wt%, wherein the sulfurized poly(1,2-butadiene) is a reaction product of sulfur and a poly(1,2-butadiene) monomer and comprises conductive carbon in an amount in the range of about 1 wt% to about 20 wt%, wherein the conductive carbon comprises carbon nanotubes, an anode current collector, a lithium or silicon anode on the anode current collector, a microporous polymer separator between the organosulfur cathode and the anode and an electrolyte material between the anode and the organosulfur cathode. [8] Lithium-sulfur accumulator or lithium-sulfur cell according to claim 7, wherein the organosulfur cathode has a porosity of less than 40%. [9] Lithium-sulfur accumulator or lithium-sulfur cell according to claim 7, wherein the binder is present in an amount of greater than approximately 0.5 wt.% to less than 2 wt.%. [10] The lithium-sulfur accumulator or lithium-sulfur cell of claim 7, wherein the reaction product further comprises a comonomer comprising an alkene functionality, the comonomer optionally further comprising sulfur groups selected from the group consisting of sulfides, disulfides, and polysulfide.

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