Selectively permeable intermediate layer

Abstract

An intermediate layer for a lithium-sulfur battery is provided. The intermediate layer is produced from an elastic polymer electrolyte liquid (EPL) and a two-dimensional conductive material such as graphene oxide. The EPL is produced from a polyphenol, a cationic polymer, and a protein that promotes ion transport. The intermediate layer is characterized by ion selective transport behavior and electrocatalytic properties, and a separator substrate coated with the intermediate layer can be usefully incorporated into a lithium-sulfur battery.

Description

Technical Field

[0001] The present disclosure relates to a selective permeability intermediate layer for a lithium-sulfur battery. The present disclosure also relates to a method of preparing the intermediate layer, a separator coated with the intermediate layer, and a lithium-sulfur battery incorporating the separator.

Background Art

[0002] Lithium-sulfur batteries have attracted attention from both the academic and industrial communities in view of their much higher theoretical specific energy density compared to lithium-ion batteries.

[0003] However, lithium-sulfur batteries face technical challenges that have so far limited their widespread adoption and commercialization. These challenges include the insulating properties of solid sulfur and the large volume changes during charging and discharging that can cause structural damage to the sulfur cathode. In addition, during the discharge process, intermediate lithium polysulfide (LiPS) is at least partially dissolved in the electrolyte, and as a result, diffuses from the cathode to the anode and is further reduced by lithium metal to form a non-conductive solid. This phenomenon is also known as the Li-S "shuttle effect".

[0004] These non-conductive solids can accumulate on the surface of the lithium metal anode and do not easily return from the solid phase to the liquid phase, which results in continuous cathode active material loss and passivation of the lithium anode, leading to irreversible capacity loss.

[0005] To date, several strategies have been utilized to address the shuttle effect. One strategy involves providing a physical barrier or intermediate layer to attempt to suppress the shuttle effect. However, in addition to providing such suppression, the intermediate layer should maintain high-speed transport of at least Li + and strongly adhere to a porous separator substrate, typically a hydrophobic polyolefin.

[0006] There remains a need for improved interlayers for lithium-sulfur batteries that address at least some of the above problems.

[0007] The reference to any prior art in this specification is not an admission or suggestion that this prior art forms part of the common general knowledge in any jurisdiction, or that this prior art could reasonably be expected to be understood, considered relevant, and / or combined with other prior art pieces by a person skilled in the art. Summary of the Invention

[0008] In one aspect, the present disclosure provides a selectively permeable interlayer for a lithium-sulfur battery, comprising: a) one or more elastomeric polyelectrolyte liquids; b) providing a selectively permeable intermediate layer comprising one or more two-dimensional conductive materials.

[0009] In an embodiment, the selectively permeable intermediate layer comprises, based on the total weight of the selectively permeable intermediate layer: a) about 15% to about 45% by weight of one or more elastomeric polyelectrolyte liquids; b) about 40% by weight to about 80% by weight of one or more two-dimensional conductive materials; Includes.

[0010] In an embodiment, the selectively permeable intermediate layer comprises, based on the total weight of the selectively permeable intermediate layer: a) about 20% to about 40% by weight of one or more elastomeric polyelectrolyte liquids; b) about 40% by weight to about 80% by weight of one or more two-dimensional conductive materials; Includes.

[0011] In embodiments, the weight ratio of the one or more elastic polyelectrolyte liquids to the one or more two-dimensional conductive materials is from about 1:1.5 to about 1:3.5.

[0012] In an embodiment, the elastic polymeric electrolyte liquid comprises, based on the total weight of the elastic polymeric electrolyte liquid: a) from about 40% to about 80% by weight of one or more polyphenols, and b) from about 5% to about 40% by weight of one or more cationic polymers, and c) from about 5% to about 35% by weight of one or more ion transport promoting proteins, and contains a mixture thereof.

[0013] In an embodiment, the elastic polymer electrolyte liquid is based on the total weight of the elastic polymer electrolyte liquid, a) from about 50% to about 80% by weight of one or more polyphenols, and b) from about 15% to about 40% by weight of one or more cationic polymers, and c) from about 5% to about 35% by weight of one or more ion transport promoting proteins, and contains a mixture thereof.

[0014] In an embodiment, the elastic polymer electrolyte liquid is based on the total weight of the elastic polymer electrolyte liquid, a) from about 50% to about 70% by weight of one or more polyphenols, and b) from about 15% to about 35% by weight of one or more cationic polymers, and c) from about 10% to about 30% by weight of one or more ion transport promoting proteins, and contains a mixture thereof.

[0015] In an embodiment, the one or more polyphenols have a molecular weight of about 100 to about 20,000 Daltons, or about 200 to about 20,000 Daltons.

[0016] In an embodiment, the one or more polyphenols include one or more of tannic acid, caffeic acid, gallic acid, ellagitannin, gallotannin, ellagic acid, proanthocyanidin, and curcumin.

[0017] In an embodiment, the one or more cationic polymers contain an amine functional group.

[0018] In embodiments, the one or more cationic polymers include one or more of polyethyleneimine, poly(allylamine) hydrochloride, poly(lysine), poly(DADMAC), and chitosan.

[0019] In embodiments, the one or more facilitative ion transport proteins include one or more of bovine serum albumin, lysosome, ovalbumin, and valinomycin.

[0020] In embodiments, the one or more two-dimensional conductive materials include one or more of reduced graphene oxide, transition metal dichalcogenide, metal-organic framework, phosphorene, and nitride.

[0021] The transition metal dichalcogenide may include one or more of MX2, where M is Mo, W, or V, and X is S, Se, or Te.

[0022] In embodiments, the selective permeable intermediate layer includes both hydrophilic and hydrophobic domains.

[0023] In embodiments, the selective permeable intermediate layer has a zero-shear viscosity of less than 500 Pa·s measured at 20 °C to 25 °C.

[0024] In another aspect, the present disclosure provides a separator for a lithium-sulfur battery comprising a porous substrate coated with a selective permeable intermediate layer according to any one of the embodiments disclosed herein.

[0025] In embodiments, the porous substrate includes one or more polyolefins.

[0026] In embodiments, the thickness of the selective permeable intermediate layer on the separator is about 100 nm to about 400 nm, or about 150 nm to about 350 nm, or about 200 nm to about 300 nm.

[0027] In embodiments, the selective permeable intermediate layer includes pores of a size large enough to enable the transport of lithium ions through the separator.

[0028] In an embodiment, the selective permeability intermediate layer coating includes pores of a size small enough to block the transport of polysulfide species through the separator. The selective permeability intermediate layer coating can block the transport of more than 90%, or more than 95%, or up to 99% or more of the polysulfide species through the separator.

[0029] In an embodiment, the selective permeability intermediate layer coating reduces the accumulation of polysulfide species on the surface of the selective permeability intermediate layer coating.

[0030] In another aspect, the present disclosure provides a lithium-sulfur battery including a lithium anode, a sulfur cathode, a separator coated with a selective permeability intermediate layer according to any one of the embodiments disclosed herein, and an electrolyte disposed between the anode and the cathode.

[0031] In an embodiment, during charging or discharging of the battery, the selective permeability intermediate layer coating reduces the accumulation of polysulfide species on the surface of the selective permeability intermediate layer coating.

[0032] In an embodiment, during charging or discharging of the battery, the selective permeability intermediate layer coating oxidizes or reduces polysulfide species.

[0033] In an embodiment, during charging or discharging of the battery, the selective permeability intermediate layer coating promotes the transport of lithium ions through the separator.

[0034] In an embodiment, during charging or discharging of the battery, the selective permeability intermediate layer coating blocks the transport of polysulfide species through the separator.

[0035] In an embodiment, the selective permeability intermediate layer coating blocks the transport of more than 90%, or more than 95%, or up to 99% or more of the polysulfide species through the separator.

[0036] In an embodiment, the electrolyte volume-to-capacity ratio of the lithium-sulfur battery is 5 μL mAh-1 or less.

[0037] In another aspect, the present disclosure provides a method for generating a selective permeable intermediate layer according to any one of the embodiments disclosed herein, including combining one or more elastic polymer electrolyte liquids with one or more two-dimensional conductive materials.

[0038] When the two-dimensional conductive material is graphene oxide, the combination of one or more elastic polymer electrolyte liquids and graphene oxide is heated to a temperature above 60 °C to reduce at least a part of the graphene oxide.

[0039] In this method, the weight ratio of one or more elastic polymer electrolyte liquids to one or more two-dimensional conductive materials is about 1:1.5 to about 1:3.5.

[0040] In another aspect, the present disclosure provides a method for generating a separator according to any one of the embodiments disclosed herein, including coating a porous substrate with a selective permeable intermediate layer according to any one of the embodiments disclosed herein.

[0041] In another aspect, the present disclosure provides an elastic polymer electrolyte liquid comprising a mixture of one or more polyphenols, one or more cationic polymers, and one or more ion transport promoting proteins.

[0042] In another aspect, the present disclosure provides a method for preparing an elastic polymer electrolyte liquid according to any one of the embodiments disclosed herein, a) combining one or more polyphenols and one or more cationic polymers; and b) adding one or more ion transport promoting proteins, wherein a) and b) are carried out under acidic conditions.

[0043] The advantages of the selective permeable intermediate layer of the present disclosure are as follows: ● Selective permeable transport of lithium ions, ● Prevent or eliminate polysulfide transport, ● Reactivation and recycling of polysulfides, ● Include one or more of strong adhesion to the separator substrate.

[0044] Any embodiment herein shall, unless otherwise specified, be modified as appropriate and applied to any other embodiment.

[0045] The present disclosure should not be limited in scope by the specific embodiments described herein for illustrative purposes only. Functionally equivalent products, compositions, and processes are clearly within the scope of the present disclosure as described herein.

[0046] Further aspects of the present disclosure and further embodiments of the aspects described in the previous paragraphs will become apparent from the following description, by way of example and with reference to the accompanying drawings.

Brief Description of the Drawings

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Best Mode for Carrying Out the Invention

[0048] The disclosure described and defined in this specification is understood to cover all combinations of two or more alternative features mentioned or apparent from the text or drawings. All of these different combinations constitute various alternative aspects of the present disclosure.

[0049] Definitions For the purposes of interpreting this specification, terms used in the singular include the plural and vice versa.

[0050] As used in this specification, unless the context requires otherwise, the term "comprise" and variations such as "comprising", "comprises" and "comprised" are not intended to exclude further additives, components, elements or steps.

[0051] When referring to measurable values such as amounts, lengths of time, etc., "about" as used in this specification means a variation of ±20% or ±10% from the specified value, in some instances ±5%, in some instances ±1%, and in some instances ±0.1%, as such variations are appropriate for carrying out the disclosed method.

[0052] As used in this specification, the term "polyphenol" refers to a compound having two or more hydroxyl groups on an aromatic ring. Thus, the term includes compounds such as phenolic acids having two or more hydroxyl groups on an aromatic ring.

[0053] Scope: Throughout this disclosure, various aspects of the invention can be presented in range format. It should be understood that the description in range format is for convenience and brevity only and should not be construed as a rigid limitation on the scope of the invention. Thus, a description of a range should be considered to specifically disclose all the possible sub-ranges within that range as well as individual numerical values. For example, a description of a range such as 1 to 6 should be considered to specifically disclose sub-ranges such as 1 to 3, 1 to 4, 1 to 5, 2 to 4, 2 to 6, 3 to 6, etc., as well as the individual numbers within that range, for example, 1, 2, 2.7, 3, 4, 5, 5.3, and 6. This applies regardless of the width of the range.

[0054] This disclosure relates to a novel selective permeable intermediate layer for a lithium-sulfur battery. The intermediate layer facilitates the transport of lithium ions but reduces the transport of polysulfide anions. Further, the intermediate layer advantageously reduces the surface accumulation of polysulfide species.

[0055] Selective permeable intermediate layer This disclosure is a selective permeable intermediate layer for a lithium-sulfur battery, a) one or more elastic polymer electrolyte liquids, and b) one or more two-dimensional conductive materials, and provides a selective permeable intermediate layer.

[0056] In an embodiment, the selective permeable intermediate layer is based on the total weight of the selective permeable intermediate layer, a) about 15 wt% to about 45 wt% of one or more elastic polymer electrolyte liquids, and b) about 40 wt% to about 80 wt% of one or more two-dimensional conductive materials, and comprises.

[0057] In an embodiment, the selective permeable intermediate layer is based on the total weight of the selective permeable intermediate layer, a) about 20 wt% to about 40 wt% of one or more elastic polymer electrolyte liquids, and b) about 40 wt% to about 80 wt% of one or more two-dimensional conductive materials, and comprises.

[0058] The amount of one or more elastic polymer electrolyte liquids in the selective permeable intermediate layer can be about 15 wt% to about 45 wt%, or about 20 wt% to about 45 wt%, or about 25 wt% to about 45 wt%, or about 30 wt% to about 45 wt%.

[0059] The amount of one or more two-dimensional conductive materials in the selective permeable intermediate layer can be about 40 wt% to about 80 wt%, or about 45 wt% to about 80 wt%, or about 50 wt% to about 80 wt%, or about 55 wt% to about 80 wt%, or about 60 wt% to about 80 wt%, or about 65 wt% to about 80 wt%, or about 70 wt% to about 80 wt%, or about 75 wt% to about 80 wt%.

[0060] In an embodiment, the weight ratio of one or more elastic polymer electrolyte liquids to one or more two-dimensional conductive materials is about 1:1.5 to about 1:3.5.

[0061] Elastic polymer electrolyte liquid One or more elastic polymer electrolyte liquids, based on the total weight of the elastic polymer electrolyte liquid, a) about 40 wt% to about 80 wt% of one or more polyphenols; and b) about 5 wt% to about 40 wt% of one or more cationic polymers; and c) about 5 wt% to about 35 wt% of one or more ion transport promoting proteins; may contain a mixture of.

[0062] One or more elastic polymer electrolyte liquids, based on the total weight of the elastic polymer electrolyte liquid, a) about 50 wt% to about 80 wt% of one or more polyphenols; and b) about 15 wt% to about 40 wt% of one or more cationic polymers; and c) about 5 wt% to about 35 wt% of one or more ion transport promoting proteins; may contain a mixture of.

[0063] One or more elastic polymer electrolyte liquids, based on the total weight of the elastic polymer electrolyte liquid, a) about 50 wt% to about 70 wt% of one or more polyphenols, and b) about 15 wt% to about 35 wt% of one or more cationic polymers, and c) about 10 wt% to about 30 wt% of one or more ion transport promoting proteins, may contain a mixture of.

[0064] Suitable polyphenols may be selected from polyphenols having a molecular weight of about 100 to about 20,000 Daltons, or about 200 to about 20,000 Daltons.

[0065] Exemplary polyphenols may include one or more of tannic acid, caffeic acid, gallic acid, ellagitannin, gallotannin, ellagic acid, proanthocyanidin, and curcumin. Other polyphenols are also contemplated.

[0066] Suitable cationic polymers may contain amine functional groups. Exemplary cationic polymers may include one or more of polyethyleneimine, poly(allylamine) hydrochloride, poly(lysine), poly(DADMAC), and chitosan. Other cationic polymers are also contemplated.

[0067] Exemplary ion transport promoting proteins include one or more of bovine serum albumin, lysosome, ovalbumin, and valinomycin. Other ion transport promoting proteins are also contemplated.

[0068] The elastic polymer electrolyte liquid can be prepared by combining one or more polyphenols, one or more conductive polymers, and one or more ion transport promoting proteins.

[0069] Preferably, the elastic polymer electrolyte liquid can be prepared by first combining one or more polyphenols and one or more cationic polymers, and then adding one or more ion transport promoting proteins.

[0070] Preferably, the elastic polymer electrolyte liquid is prepared under acidic conditions.

[0071] Properties of the elastic polymer liquid In a combination of one or more polyphenols, one or more cationic polymers, and one or more ion transport promoting proteins, a high-density phase and a clear supernatant can be formed, and such a mixture promotes self-assembly with one or more two-dimensional conductive materials.

[0072] In one embodiment, the polyphenol is tannic acid, the cationic polymer is polyethyleneimine, and the ion transport promoting protein is bovine serum albumin. In one example, a suitable elastic polymer electrolyte liquid can be prepared by combining tannic acid, polyethyleneimine, and bovine serum albumin in a weight ratio of about 60:25:15. Such a composition has a surface charge determined by a zeta potential of about +40 mV. Fourier transform infrared spectroscopy indicated the presence of phenolic, amine, carboxyl, carbonyl, and amide stretching modes.

[0073] In another embodiment, the polyphenol is caffeic acid, the cationic polymer is polyethyleneimine, and the ion transport promoting protein is bovine serum albumin. In one example, a suitable elastic polymer electrolyte liquid can be prepared by combining caffeic acid, polyethyleneimine, and bovine serum albumin in a weight ratio of about 60:15:25.

[0074] In another embodiment, the polyphenol is gallic acid, the cationic polymer is polyethyleneimine, and the ion transport promoting protein is bovine serum albumin. In one example, a suitable elastic polymer electrolyte liquid can be prepared by combining gallic acid, polyethyleneimine, and bovine serum albumin in a weight ratio of about 60:15:25.

[0075] In another embodiment, the polyphenol is tannic acid, the cationic polymer is pDADMAC, and the facilitative ion transport protein is bovine serum albumin. In one example, a suitable elastic polymeric electrolyte liquid can be prepared by combining tannic acid, pDADMAC, and bovine serum albumin in a weight ratio of about 60:15:25.

[0076] In another embodiment, the polyphenol is tannic acid, the cationic polymer is polyethyleneimine, and the facilitative ion transport protein is lysosome. In one example, a suitable elastic polymeric electrolyte liquid can be prepared by combining tannic acid, polyethyleneimine, and lysosome in a weight ratio of about 60:15:25.

[0077] Two-dimensional conductive material One or more two-dimensional conductive materials may include one or more of reduced graphene oxide, transition metal dichalcogenides, metal-organic frameworks, phosphorene, and nitrides. Other two-dimensional conductive materials are also contemplated.

[0078] Exemplary transition metal dichalcogenides may include one or more of MX2, where M is Mo, W, or V, and X is S, Se, or Te, such as MoS2, MoTe2, and VS2.

[0079] Preparation of the selective permeable intermediate layer The selective permeable intermediate layer can be prepared by combining one or more elastic polymeric electrolyte liquids and one or more two-dimensional conductive materials.

[0080] Preferably, the weight ratio of one or more elastic polymeric electrolyte liquids to one or more two-dimensional conductive materials is from about 1:1.5 to about 1:3.5.

[0081] In embodiments where the two-dimensional conductive material includes graphene oxide, a mixture of one or more elastic polymer electrolyte liquids and one or more two-dimensional conductive materials is heated to a temperature above 60°C, preferably about 80°C, to convert at least a portion of the graphene oxide to reduced graphene oxide.

[0082] The heating can be carried out for about 1 hour to about 36 hours, preferably about 8 hours to about 20 hours.

[0083] Properties of the Selective Permeability Intermediate Layer The elastic polymer electrolyte liquids of the present disclosure impart advantageous properties to the selective permeability intermediate layer when combined with two-dimensional conductive materials. The elastic polymer liquids improve ion transport and enhance coating properties and adhesion to the separator substrate. In addition, when the two-dimensional conductive material is graphene oxide, the elastic polymer electrolyte liquid reduces at least a portion of the graphene oxide to reduced graphene oxide.

[0084] In embodiments, the selective permeability intermediate layer includes both hydrophilic and hydrophobic domains.

[0085] In embodiments, the selective permeability intermediate layer has a zero-shear viscosity of less than 500 Pa·s measured at 20°C to 25°C.

[0086] In one embodiment where the elastic polymer electrolyte liquid is formed from a mixture of tannic acid, polyethyleneimine, and bovine serum albumin in a weight ratio of approximately 60:25:15, a suitable selective permeable intermediate layer can be produced by combining this mixture with graphene oxide in a weight ratio of approximately 1:2. By combining, gelation likely occurs due to various interactions between the elastic polymer electrolyte liquid and graphene oxide, such as π-π, hydrogen, and Coulombic force interactions. This is supported by the observation that the zero-shear viscosities of graphene oxide and the elastic polymer liquid, which are 45 Pa·s and 4 Pa·s respectively, increase to 980 Pa·s after gelation, and the material has a surface charge of +30 mV. Heating to 80 °C for various times to reduce graphene oxide results in a selective permeable intermediate layer with a zero-shear viscosity of 250 Pas and a surface charge of +37 mV.

[0087] Separator Porous separators such as Celgard polyolefin separators are utilized within battery systems due to their inertness and excellent stability. However, one drawback is their hydrophobic characteristics, which are not favorable for coating modification.

[0088] An advantageous feature of the selective permeable intermediate layer of the present disclosure is that casting on a hydrophobic surface such as the Celgard surface is made possible by the amphiphilic and excellent adhesion properties of the polyphenol and ion transport promoting protein components, that is, by the presence of both hydrophilic and hydrophobic domains within the intermediate layer.

[0089] Method for manufacturing separator A porous separator substrate such as Celgard can be coated with the selective permeable intermediate layer of the present disclosure on one or both surfaces of the porous substrate.

[0090] The method for preparing the separator of the present disclosure is not particularly limited, and known methods for modifying these methods or various methods can be used by those skilled in the art.

[0091] In one method, the selective permeability intermediate layer of the present disclosure is prepared and then coated on at least one surface of the porous substrate and then dried.

[0092] Useful porous separator substrates include polyarylate, polyethylene terephthalate, polybutylene terephthalate, polysilane, polysiloxane, polysilazane, polyethylene, polycarbosilane, polyacrylate, poly(meth)acrylate, polymethyl acrylate, polymethyl (meth)acrylate, polyethyl acrylate, cyclic olefin copolymer, polyethyl (meth)acrylate, cyclic olefin polymer, polypropylene, polyimide, polystyrene, polyvinyl chloride, polyacetal, polyether ether ketone, polyester sulfone, polytetrafluoroethylene, polyvinylidene fluoride, perfluoroalkyl polymer and other polymers. Preferred porous substrates include polyolefins such as polyethylene or polypropylene.

[0093] The coating process can be controlled to provide a selective permeability intermediate layer thickness of about 100 nm to about 400 nm, or about 150 nm to about 350 nm, or about 200 nm to about 300 nm on the porous substrate.

[0094] Separator performance The selective permeability intermediate layer in the lithium-sulfur battery can advantageously have a pore size smaller than that of lithium polysulfide (LiPS), but also allows Li + transport. Sub-nanometer pores necessary to block or prevent LiPS transport are a fundamental limitation of Li-S batteries due to the significant mass transport resistance that can be imposed on Li + transport. Such Li + transport promotes electrochemical reactions, and those obstacles can lead to low active material utilization, concentration polarization, low CE and high cell resistance.

[0095] Another limitation is that these blocked LiPS species can ultimately accumulate on the surface of the intermediate layer, i.e., cause intermediate layer adhesion fouling and pore clogging. This can lead to loss of active material, high microviscosity of the interlayer surface, passivation of the surface, and potentially create a feedback loop of degraded ion transport.

[0096] During cell operation, there are a number of different LiPS species present in the electrolyte. Due to the low dielectric constant of the ether solvent (ε ~ 7) and the high ion concentration of the Li + salt in the electrolyte [Li + ≥ 1 M, the dominant species are the neutral ion triplet [Li2S n and its clusters [Li2S n x while the isolated ion pairs [Li2S n - and [S n - can be ignored. Among these many species, Li2S4 is the most dominant species generated during operation because the reduction of Li2S4 to Li2S accounts for approximately 75% of the theoretical cell capacity.

[0097] The selective permeable intermediate layer desirably has redox mediator properties or an electrocatalytic surface to "reactivate" and "recycle" the accumulated LiPS species by promoting their conversion kinetics, while at the same time reducing the irreversible deposition of Li2S.

[0098] The selective permeable intermediate layer of the present disclosure addresses these issues. These demonstrate the ability to minimize surface accumulation of LiPS species by allowing Li-ion transport while retaining or blocking the transport of LiPS species and by "reactivating" the LiPS species due to the redox mediator properties of the selective permeable intermediate layer.

[0099] In an embodiment, the separator disclosed herein can prevent more than 90% LiPS transfer through the separator, or more than 95%, or up to 99% LiPS transfer rejection.

[0100] ​​​In an embodiment, the separator disclosed herein oxidizes and reduces LiPS on the surface of the selective permeability intermediate layer. Therefore, the accumulation of LiPS on the surface is reduced or eliminated.

[0101] Lithium-sulfur battery The present disclosure provides a lithium-sulfur battery including a lithium anode, a sulfur cathode, a separator according to any one of the embodiments disclosed herein, and an electrolyte disposed between the anode and the cathode.

[0102] The selection of the lithium anode is not particularly limited. It can be lithium metal or a lithium alloy. Here, the lithium alloy contains an element that can be alloyed with lithium, and the element can be Si, Sn, C, Pt, Ir, Ni, Cu, Ti, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, Co, or an alloy thereof.

[0103] The selection of the sulfur cathode is not particularly limited. It can include elemental sulfur, a sulfur compound used in the technical field of constructing sulfur cathodes, or a mixture thereof.

[0104] The sulfur cathode can include a conductor. Commonly used conductors include graphite, carbon black, carbon fiber, carbon nanotube, and the like.

[0105] The sulfur cathode can also include a binder. However, the binder is not limited, and a binder typically used in the technical field of sulfur cathode structures can be used.

[0106] The electrolyte of the lithium-sulfur battery is a lithium salt-containing electrolyte liquid, which can be an aqueous electrolyte liquid or a non-aqueous electrolyte liquid, and preferably a non-aqueous electrolyte formed by an organic solvent electrolyte liquid and a lithium salt. In addition, an organic solid electrolyte, an inorganic solid electrolyte, etc. can be used, but the electrolyte liquid is not limited thereto.

[0107] Examples of non-aqueous organic solvents may include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, 4-methyl-1,3-dioxane, diethyl ether, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate ester, trimethoxymethane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, or ethyl propionate.

[0108] The lithium salt is a material preferably dissolved in the non-aqueous electrolyte, and examples thereof include LiCl, LiBr, LiI, LiNO3, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, (CF3SO2)2NLi, (FSO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium tetraphenylborate, lithium imide, and the like.

[0109] In an embodiment, the lithium-sulfur battery of the present disclosure has a sulfur loading of more than 3 mg cm -2 super, or more than 6 mg cm -2 super.

[0110] In an embodiment, the lithium-sulfur battery of the present disclosure has an electrolyte volume-to-capacity ratio of 5 μL mAh -1 or less.

[0111] Performance of the lithium-sulfur battery The coin cell containing the separator disclosed herein has a very low electrolyte / capacity (E / C) ratio of 4.9 to 5.3 μL mAh -1 and achieves an areal capacity of 4.8 to 8.1 mAh cm with 450 stable cycles at a very low electrolyte / capacity (E / C) ratio of 4.9 to 5.3 μL mAh -2

[0112] The pouch cell prototype (3 cm × 5 cm) containing the separator disclosed herein achieves an energy density of 202 Wh kg-1 over 100 stable cycles.

Example

[0113] Materials The sulfur cathode was composed of crystalline sulfur (Sigma Aldrich), carbon (Black Pearls 2000, CABOT Co.), and carboxymethyl cellulose binder (Sigma). The elastic polymer electrolyte liquid (EPL) was composed of tannic acid (Sigma), polyethyleneimine (Mn 1000, Sigma), and bovine serum albumin (Heat Shock Fraction, Sigma). Graphene oxide paste (The Sixth Element Inc.) was purified, exfoliated, and made into a suspension by adding deionized water. Lithium bis(trifluoromethane)sulfonamide salt and lithium nitrate were purchased from Sigma-Aldrich and used directly without further purification. Dimethoxyethane (DME) and 1,3-dioxolane (DOL) solvents were purchased from Sigma. Li2S was purchased from Alfa Aesar for the synthesis of lithium polysulfide. Battery-grade etched Al foil was purchased from Japan Capacitor Industrial Co., and Celgard 2730 was purchased from Celgard Inc., USA.

[0114] Example 1: Preparation of Elastic Polymer Electrolyte Liquid (EPL) ​The elastic polymer electrolyte liquid (EPL) was synthesized by combining different ratios of components. A solution of tannic acid (TA) was vigorously stirred at 1000 rpm, and then polyethyleneimine (PEI) and then bovine serum albumin (BSA) were added at a rate of 1 mL per minute until the desired ratio was achieved. -1 All EPL samples were prepared at pH 5 to prevent or minimize any covalent bond reactions that could occur under basic conditions such as Michael addition reactions.

[0115] Variations in the TA:PEI:BSA ratio indicated the component ratios at which the preferred EPL was formed. Figure 1 illustrates this for the TA:PEI:BSA system highlighting the region of EPL preference.

[0116] The amphiphilicity of EPL was demonstrated by its ability to create a stable oil-in-water emulsion using paraffin oil and water (30 vol% oil). This suggested that the hydrophobic domain of EPL could interact with paraffin oil and the hydrophilic domain of EPL could interact with water to produce a stable solution of otherwise immiscible phases.

[0117] Example 2: Preparation of an intermediate layer containing EPL and reduced graphene oxide EPL was added to a suspension of graphene oxide (GO) at a given mass ratio and stirred vigorously. Gelation was observed after 15 minutes. All EPL-GO mixtures were stirred overnight. For reduction, the EPL-GO suspension was then heated to 80 °C for different times to produce an elastic polymer electrolyte liquid-reduced graphene oxide (EPL-rGO) for subsequent use as an intermediate layer.

[0118] Example 3: Variation in the amount of intermediate layer components Several EPL-rGO intermediate layer samples were prepared with different component amounts. Table 1 collects details and ranks the samples regarding several performance parameters. Each EPL composition was mixed with graphene oxide at a weight ratio of 1:2 (EPL:GO) and reduced at 70 °C for 12 hours. The relative sheet resistance was recorded as a proxy for the degree of GO reduction. The amphiphilicity was estimated by the coatability of the material on the exposed Celgard as a measure of the extent to which it was useful for coating the hydrophobic surface of Celgard. The selective permeability was evaluated by a diffusion cell test. The ionic conductivity was measured by electrochemical impedance spectroscopy (EIS).

Table 1

[0119] The results are that i) the reduction of GO can be mainly attributed to TA, but also to PEI; ii) all components can contribute to ion transport, especially the improvement of BSA, but the yield may decrease after exceeding a certain ratio; iii) the Li + affinity can be associated with the PEI content; iv) the favorable adhesion characteristics can be derived from BSA and TA; v) the selective permeability can be attributed to the BSA content. These results are further discussed in the following paragraphs.

[0120] Example 4: Characterization of the EPL-rGO Intermediate Layer Figure 2F is a bright-field polarized light microscopy image of the EPL-rGO (60:25:15 EPL composition) of Example 3, showing liquid crystalline domains. This suggests that a high degree of structural order remained even after reduction. Figure 2E shows the variations in the viscosities of EPL, GO, the combination of EPL and GO, and EPL-rGO. When EPL and GO are combined, a significant increase in the zero-shear viscosity consistent with the observed gelation can be seen. With reduction, the zero-shear viscosity decreases.

[0121] The reduction from EPL-GO to EPL-rGO was further evidenced by the increase in electrical conductivity with respect to the reduction time (see Figure 3). It can be seen that a long reduction time may have an adverse effect on the coating property of EPL-rGO. Over-reduction may lead to the formation of particulate materials that degrade the performance as an interlayer material. The reduction was further confirmed by Fourier transform infrared (FTIR) spectroscopy showing a decrease in the intensity of the peaks associated with C-O and C=O bonds, and X-ray photoelectron spectroscopy (XPS) showing a decrease in the relative intensity of the sp2 to sp3 domains indicating the deoxygenation of GO. Raman spectroscopic studies showed a shift of the G band in the spectrum to lower frequencies (red shift) from EPL-GO to EPL-rGO, further confirming the further reduction.

[0122] EPL-rGO also maintained long-term colloidal stability, as evidenced by its stability even after storage for 3 months at ambient temperature.

[0123] Example 5: Preparation of separator EPL-GO, EPL-rGO and rGO were coated on Celgard. However, for comparison of the selective permeable interlayer, the coating property of Celgard was improved by immersion coating in a 15 g / L solution of tannic acid for 15 minutes, thereby imparting hydrophilicity, and this hydrophilized Celgard was used for all experiments. The coating was performed by rod coating. The rGO interlayer was reduced by UVC light (254 nm). The exposure time was adjusted to about 220 minutes to achieve a similar thin film resistance as EPL-rGO. -1

[0124] Example 6: Study of EPL-rGO interlayer The molecular rejection cutoff of LiPS is approximately 9 Å. By adjusting the degree of reduction and the ratio of EPL to GO, it is possible to manipulate the interlayer spacing to meet this design criterion. X-ray diffraction (XRD) shows two peaks for EPL-rGO, indicating the presence of a double-channel spacing with a wide channel of 8.9 Å and a narrow channel of 3.7 Å (Figure 4B). It should be noted that the difference between the wet-state spectrum and the dry-state spectrum is minimal, showing negligible changes in the interlayer spacing when EPL-rGO is immersed in the solvent for 24 hours. The narrow channels arise from highly reduced and stacked lamellar domains, i.e., the sp 2 carbon stacking regions, while the wider channels are the result of the intercalation of EPL into the lamellae. This is schematically depicted in Figure 4A. Positron annihilation lifetime spectroscopy (PALS) analysis reveals an average interlayer spacing of 8.2 Å from the spectrum in Figure 4C, meaning that approximately 15% of the channels are narrow and approximately 85% of the channels are wide. Both the narrow and wide channels reject LiPS, but the wide channels allow for + an increase in Li transmittance.

[0125] Example 7: Rejection Performance of the Intermediate Layer As illustrated in Figure 5A, the rejection performance of the intermediate layer was studied in a diffusion cell with DOL / DME on one side and Li2S4 dissolved in DOL / DME on the other side. The synthesis of the Li2S6 and Li2S4 solutions followed the method reported by Liao et al., J. Mater. Chem., vol. 4, pp. 5406 - 5409, 2016. Elemental sulfur and Li2S powder were stirred and mixed in a solvent of DOL and DME (DOL / DME = 50 / 50 (v / v)) at 50 °C for 48 hours in an argon glove box with an appropriate molar ratio. The resulting solution was centrifuged at 5000 rpm for 10 minutes to remove any unreacted particles.

[0126] Quantification of Li2S4 by UV-Vis spectroscopy revealed that the EPL-rGO interlayer could reject 99% of Li2S4, while the GO and rGO interlayers achieved 32% and 91%, respectively, and EPL-GO had a rejection of 79%. A visual summary of the results is provided in Fig. 5B.

[0127] The rejection performance depends not only on the interlayer spacing of the lamellar interlayer but also on the stability in the harsh electrolyte and LiPS environment during operation, as shown in Fig. 5C. The interlayer coated on Celgard was immersed in a 2 mM solution of Li2S6 for 48 h in the presence of LiTFSI and LiNO3 to simulate the environment of a Li-S battery. Under solvated conditions, the GO coating lost its structural integrity. The rGO coating exhibited poor conformational stability, and the separator curled after 48 h. EPL-GO had a dry interlayer spacing of 11.1 Å, slightly above the threshold for LiPS rejection, while showing improvement while remaining fixed to the underlying substrate. The strong interaction between EPL and rGO, and the strong interlayer interaction between the narrow channels, i.e., the strong π-π stacking between the sp 2 domains of rGO, is likely important for maintaining structural integrity and reducing swelling in the solvent.

[0128] The thickness of the EPL-rGO interlayer coated on Celgard varied from 70 to 480 nm. Fig. 6 is a plot of the thickness of the interlayer against the ionic conductivity and the lithium polysulfide rejection reaction. A higher interlayer thickness led to higher polysulfide rejection, but the ionic conductivity was negatively affected. An interlayer thickness of approximately 250 nm provided a useful balance between the ability to reject LiPS and the ability to maximize ionic conductivity.

[0129] The diffusion cell study was conducted by placing the desired separator between the two chambers of the diffusion cell, with 0.3 M Li2S4 on one side and a blank solvent on the other side, and allowing it to permeate for 48 h. The polysulfide rejection value was

Number

Equation

[0130] Example 8: Battery Manufacturing and Evaluation of Electrochemical Characteristics The cathode was composed of 70 wt% sulfur, 20 wt% carbon black, and 10 wt% CMC binder, and was fabricated on a tape cast on an Al foil current collector using a thick aqueous slurry and a doctor blade. The cathode was air-dried for 2 hours and further dried overnight in a vacuum oven at 50 °C. Then, the cathode was cut into 1 cm 2 disks. A CR2032 coin cell was assembled in an Ar-filled glove box with O2 and moisture < 0.1 ppm using a Li metal anode, the aforementioned cathode, and a separator having different selective permeable intermediate layer coatings. For the evaluation of electrochemical characteristics, a constant current charge-discharge method (same charge / discharge current) was used with a Neware battery cycler (Neware Technology Limited) for Li / Li + ​It was applied in the voltage range of 1.8 - 2.7V. Cyclic voltammetry (CV) was performed on EC-Lab (BioLogic Science Instruments, France) at different scan rates and Li / Li + It was carried out in the voltage range of 1.8 - 2.8V with respect to + . Electrochemical impedance spectroscopy (EIS) was also performed using EC-Lab, measuring the response over the frequency range of 1 MHz - 10 mHz and recording 6 points per decade of frequency. To ensure reproducibility, the impedance was repeated 3 times. The diffusion coefficient

Number

Number

Number

[0131] Example 9: Performance of Coin Cells A standard cathode consisting of sulfur, a conductive carbon additive, and a water-soluble binder was used and consistently used throughout the study. The cycle performance of different separators with the same thickness of the intermediate layer coating and E / S ratio was compared at a sulfur loading of 3.2 mg cm -2 and a cycle rate of 0.1 C (see Figure 7A). The EPL-rGO intermediate layer showed a minimum capacity decay over 120 cycles with a maximum capacity of 1,505 mAh g -1 (90% sulfur utilization) and CE > 99%. In contrast, EPL-GO had a significantly lower capacity of 1,102 mAh g -1 and 80 stable cycles before the onset of rapid capacity decay. The cells using EPL-rGO could maintain excellent cycle stability with high sulfur utilization (>1400 mAh g -1 ) without capacity loss. The exposed GO intermediate layer resulted in a very low initial capacity and limited cycle life.

[0132] To further study the performance differences, electrochemical property evaluations were used. These include cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and analysis of galvanostatic charge-discharge curves.

[0133] CV was used to gain insights into the electrochemical processes occurring during the anode and cathode processes, enabling comparison of reaction kinetics. Figure 7B shows that the EPL-rGO interlayer had anodic peaks at 2.41 V and 2.33 V and cathodic peaks at 2.37 V and 2.06 V. Compared with other interlayers, the peaks were sharper, exhibited higher peak current density, had a significantly higher cathodic reaction potential and a lower anodic potential. The peak positions and high current density suggest that the EPL-rGO interlayer has excellent ion transport properties, accelerated redox kinetics of the lithium polysulfide (LiPS) reaction, and can effectively suppress LiPS shuttling.

[0134] The galvanostatic charge-discharge curves in Figure 7D complement the CV data. The plateau voltage ranges and their respective capacities are controlled by the access of Li + ions, the kinetics of LiPS conversion, and the ability to mitigate LiPS shuttling. For the EPL-rGO interlayer, the start of the second plateau was at 2.05 V and 380 mAh g -1 which indicates the availability of Li + and fast ion transport at the cathode, as well as the fast redox reaction of higher-order LiPS. The length of the second plateau, which mainly contributes to the capacity, exceeds 950 mAh g -1 suggesting excellent LiPS retention and the ability to catalyze the reaction of lower-order LiPS to Li2S.

[0135] The significantly large potential barriers at the initial stage of the charging process for GO, rGO, and the EPL-GO interlayer clearly indicate that a high overpotential is required to convert insulating Li2S discharge products to LiPS, and the lack of redox mediator properties results in retarded diffusion kinetics. Furthermore, the significantly lower polarization when using EPL-rGO as the interlayer further suggests a combined effect of cycle suppression, excellent ion transport, and a remarkable ability to enhance the LiPS conversion reaction. The higher polarization of the other interlayers is likely due to a combination of insufficient ion transport and concentration polarization of LiPS on their surfaces. As a result of ohmic and concentration polarization, the initial internal resistance (IR) drop of the discharge profiles of each interlayer is significantly lower for the EPL-rGO interlayer.

[0136] The dynamics of ion transport and LiPS regulation were further investigated using electrochemical impedance spectroscopy (EIS) to compare the internal cell resistances. The Nyquist plots are shown in Fig. 7C. The plots consist of a semicircle in the high-frequency region, where the diameter can be assigned as the charge transfer resistance, and a slanted line (Warburg impedance) in the low-frequency domain related to capacitive fade and electrochemical response. The EIS results complement the findings from the CV curves and charge-discharge curves. The reduced internal resistance of EPL-rGO is likely the result of its architecture favorable for ion transport, lithium affinity, and its ability to function both as an upstream current collector and a redox mediator to drive the LiPS conversion reaction due to its electronic conductivity.

[0137] At a higher cycle rate of 0.4 °C, a maximum capacity of 1,382 mAh g−1 was achieved after several activation cycles and exhibited a CE of over 98.5% over approximately 450 stable cycles, as shown in Fig. 7E. At a very high sulfur loading of 6 mg cm -2 and an area capacity > 7 mAh cm -2 was maintained over 70 cycles at a rate of 0.1C with minimal capacity loss at a very low electrolyte-to-capacity (E / C) ratio of 4.9 μL mAh−1 (reaching a maximum of 8.1 mAh cm -2 )(Fig. 7F).

[0138] The study of electrochemical impedance spectroscopy (EIS) showed that the internal cell resistance decreased with the number of cycles, indicating the high reversibility of the battery, and a slight increase was observed after 300 cycles. CV was carried out at four different scan rates, showing a strong current response and suggesting excellent reaction kinetics. The measured current followed a power-law relationship with the scan rate related to the Li+ diffusion coefficient, D_Li^+. The D_Li^+ of the complete cell was 10 -9 cm 2 s -1 orders of magnitude.

[0139] Example 10: Pouch cell Using an EPL-rGO separator, a double-sided sulfur cathode (with a single-sided sulfur loading of 3 mg cm -2 and a total of 6 mg cm -2 ), and a 100-μm-thick lithium metal anode with an E / S ratio of 5, a pouch cell prototype was fabricated. The delivered initial energy density was 202 Wh kg-1 and 925 mAh g-1 at a rate of 0.05 °C over 100 cycles. The cycle data are presented in Figure 8A.

[0140] The charge-discharge profile in Figure 8C shows that the start of the second plateau is at 2.08 V and 290 mAh g-1, indicating low polarization and low IR drop. The high voltage of the second plateau is essential for the energy density. The Nyquist plot in Figure 8D shows that the impedance spectrum exhibits non-negligible changes even after 40 cycles.

[0141] Example 11: Lithium ion transport study Figure 9A shows the cell configuration for measuring ion conductivity and Li+ transference number. Figure 9B illustrates the results of different interlayers, and also shows images of the electrolyte contact angles of different interlayers.

[0142] Rapid Li + ion transport is Li +Making ions more readily available at the cathode, enabling reaction with sulfur during discharge (and the reverse during charge), is essential for improving sulfur utilization, CE, and cycle life. In an electrochemical device, ion transport through the separator consists of ionic conductivity (σ m ) composed of diffusion and the potential driving force, as well as the ion current carried by Li + and TFSI - and NO3 - and both Li + and its co-ions, and is characterized from the perspective of the transference number of Li + (t + Li + + ) that explains the ion current carried by Li

[0143] Li + has a significantly larger solvation radius than the pore diameter required to reject LiPS, so i) the first step is that Li + must undergo desolvation and dissociation of the ion pair at the interlayer surface, and ii) then the Li + ions must "adsorb" and "stabilize" to split within the pores, and iii) diffusion through the interlayer continues and can be described as a series of formations, breakages, and reformations of bonds with the next coordinate atoms. The schematic diagram in Figure 9C outlines the proposed mechanism.

[0144] The activation energy required for Li + transport through the interlayer was calculated from the slope in Figure 9D. The activation energy with 95% confidence for Celgard is 32.1 ± 0.39 kJ mol -1 , while for GO it is 33.2 ± 0.23 kJ mol -1 . When EPL is added, it improves to similar values of 27.3 ± 0.50 kJ mol -1 for EPL-GO and 26.9 ± 0.42 kJ mol -1 for EPL-rGO.

[0145] Example 12: Separator electrocatalytic activity To confirm that EPL-rGO has redox mediator properties, coin cells were assembled with different intermediate layers facing the bottom casing current collector having 0.5 M Li2S6 and a Li anode in the electrolyte (catholyte). The arrangement is shown in Figure 10A. CV scans at three different scan rates in Figure 10B revealed two cathodic peaks consistent with the conversion of higher-order LiPS to short-chain LiPS and then to the final discharge product Li2S, while the anodic scan exhibited peaks for the reverse process. The strong, sharp peaks in the presence of only the EPL-rGO material (in the absence of sulfur or conductive carbon additives) strongly demonstrate that it has excellent catalytic activity and kinetics for LiPS conversion.

[0146] Complementary experiments to establish the electrocatalytic activity towards LiPS were carried out in a symmetric cell experiment. The symmetric cell was assembled with the same working and counter electrodes in 0.5 M catholyte. The cell was cycled at a scan rate of 10 mVs -1 shown in Figure 11 from -0.8 V to 0.8 V. The highest current response was for EPL-rGO, which was consistent with the concept of a redox mediator intermediate layer playing a major role in enhancing the redox kinetics of LiPS and in agreement with the observations from the catholyte cell. The peaks at +0.35 V and -0.42 V were consistent with the reduction and oxidation of Li2S6 on the intermediate layer surface. These results are in stark contrast to other intermediate layers. GO and EPL-GO exhibited negligible peaks due to the lack of electron conductivity, while rGO exhibited broad anodic and cathodic peaks at a current density approximately 20 times lower due to the lack of interaction and low affinity with LiPS.

[0147] In addition, a comparison was made with the redox mediator materials commonly studied in the Li-S battery of FIG. 12, and the same mass ratio of LiPS to the redox mediator material was maintained for a fair comparison. Without adding a conductive additive, the EPL-rGO interlayer exhibits better performance than well-known electrocatalytic materials that result in sharper peaks and higher current densities. The CV curves are equivalent only when conductive carbon is added. A notable exception is that these coatings, unlike EPL-rGO, are not selectively permeable, have a lower LiPS adsorption capacity compared to EPL-rGO, and require a very high electrolyte volume for complete wetting.

[0148] Example 13: Preparation and Use of Further Elastic Polymer Electrolyte Liquid (EPL) As described in Example 1, various polyphenols, cationic polymers, and ion transport promoting proteins were used to prepare a further elastic polymer electrolyte liquid (EPL) with a mass ratio of 60:15:25. These formulations are shown in Table 2.

Table 2

[0149] Interlayer materials as in Example 2 were prepared, including EPL formulations 1 - 4 of Table 2 and graphene oxide (GO) with an EPL:GO ratio of 1:2. Reduction was carried out at 70 °C for 12 hours, and each EPL-rGO formulation was coated onto a Celgard substrate as in Example 5. Good adhesion to the substrate and film quality were observed.

[0150] As in Example 9, coin cells were prepared with a sulfur loading of 3 mg cm -2 and the cycle performance of different separators at a cycle rate of 0.25 °C was compared.

[0151] Figure 13 illustrates that four formulations (1, 2, 3, and 4) showed minimal capacity decay over 150 cycles.

[0152] Electrochemical Property Evaluation The ionic conductivity of the separator was calculated from EIS and repeated three times. Each separator was saturated with electrolyte (20 μL) and sandwiched between two stainless steel electrodes in a coin cell. After a 12-hour rest, the ionic conductivity was calculated according to the following formula: [Number] where σ is the ionic conductivity, L is the thickness of the intermediate layer, A is the area of the stainless steel electrode, and R b is the bulk resistance. The Li + transference number was calculated by the Bruce-Vincent method from AC impedance measurements combined with DC polarization. An electrolyte-impregnated separator (20 μL) was placed between two Li electrodes in a coin cell. Then, the Li + transference number [Number] was calculated as follows: [Number] where ΔV is the potential difference applied by a chronoamperometric step of 10 mV, I SS and I0 are the steady-state and initial currents, and R SS and R0 are the steady-state and initial interfacial resistances determined by impedance spectroscopy. The activation energy was calculated based on the Arrhenius relationship of a symmetric cell. Keeping all other things constant, the activation energy E a enabled a comparison based on the desolvation energy of Li + and diffusion through the separator. The Arrhenius relationship is given as follows: [Number] where A is the pre-exponential factor, R ct is the impedance (ohm), T is the temperature (K), and R is the gas constant (Jmol-1 K -1 ) is.

[0153] Separator property evaluation The measurement of the static electrolyte contact angle was carried out on the separator at room temperature and 50% controlled humidity using the droplet method with a Dataphysics OCA35 contact angle meter, and the droplet volume was 6 μL. The electrolyte uptake of the separator was determined by immersing it in the electrolyte solution for 2 hours, removing excess electrolyte from the surface using filter paper, and then recording the weight of the separator. The test was performed in an inert argon atmosphere inside a glove box. The electrolyte uptake was calculated using the following formula:

Equation

[0154] To test the hydrodynamic permeability of different separators, the solvent permeability was measured in a dead-end filtration cell from Sterlitech (HP4750 Stirred Cell, Sterlitech USA) with an effective surface area of 14.6 cm 2 . The pressure was maintained at 200 mbar, and the mass and pressure records were taken every second using a Radwag precision balance (PS1000.R2, Poland) and a Fluigent pressure pump (MFCS-EX, France). The separator was stabilized for 2 hours to obtain the permeability results and repeated 3 times to ensure reproducibility. The permeability J is defined as follows:

Equation

[0155] Further property evaluation techniques The Fourier transform infrared (FTIR) spectrum was averaged over 32 scans with a resolution of 2 cm -1 from 400 to 4000 cm -1Recorded using an attenuated total reflection FTIR spectrometer (PerkinElmer, USA) within the range. X-ray photoelectron spectroscopy (XPS) was performed to investigate the reduction of EPL-rGO by comparing the sp 2 and sp 3 peaks. This was carried out using a Nexsa Surface Analysis System (ThermoFisher Scientific, USA) with a monochromatic AlKα source. Scanning electron microscopy (SEM, FEI Nova NanoSEM 450 FEG) was used to investigate the morphology of the nanoparticle images. The samples were mounted on Al stubs and coated with iridium using a Cressington 208HRD sputter coated to a thickness of approximately 2 nm. Secondary electron images were collected at an acceleration voltage of 5 kV and a working distance of 5 mm. The lithium polysulfide concentration was determined using UV-Vis by first preparing a set of standards and creating a calibration curve (Lambda 365, PerkinElmer, USA). X-ray diffraction (XRD) analysis using a Bruker D2 Phaser diffractometer with Cu Kα radiation was generated at 30 kV and 10 mA with a scan speed of 0.4° per -1 and a step size of 0.02°. Raman spectra were obtained using a Renishaw Confocal micro-Raman spectrometer equipped with a HeNe (632.8 nm) laser operating at 10% output. Extended scans (10 s) were performed at a laser spot size of 1 μm over a wavenumber range of 100 - 3200. Once the background was removed, the intensity of the spectra was normalized by dividing the data by the maximum intensity. The surface charge was evaluated using a dynamic light scattering analyzer (NanoBrook 90Plus PALS, Brookhaven, USA). Rheological tests were conducted using a strain-controlled ARG2 rheometer (TA instruments, USA) with a cone-plate geometry (cone angle 2° and cone diameter 50 mm). A constant gap of 0.045 mm was maintained during the test. The temperature was controlled at 23.00 ± 0.01 °C for the experiment. For steady-state measurements, 0.01 s -1 to 100 s-1 The shear rates in the range of were used. The polarized light microscopy was performed using an inverted Leica DM IRB microscope equipped with an Abrio polarization imaging system manufactured by CRI Inc., and the images were taken in a birefringence setting mode that included two variable electro-optic retardation plates instead of a linear polarizer, an analyzer, and a compensator. The polarized light transmitted through the specimen loaded on a clean microscope slide passed through the analyzer and was captured by a CCD camera. The captured signal was continuously processed using a digital image processing system to generate optical retardation and slow axis orientation images.

Claims

1. A selective permeable intermediate layer for a lithium-sulfur battery, comprising: a) one or more elastic polymer electrolyte liquids; and b) one or more two-dimensional conductive materials.

2. Based on the total weight of the intermediate layer, the intermediate layer comprises: a) about 15 wt% to about 45 wt% of one or more elastic polymer electrolyte liquids; and b) about 40 wt% to about 80 wt% of one or more two-dimensional conductive materials. The selective permeable intermediate layer according to Claim 1.

3. Based on the total weight of the intermediate layer, the intermediate layer comprises: a) about 20 wt% to about 40 wt% of one or more elastic polymer electrolyte liquids; and b) about 40 wt% to about 80 wt% of one or more two-dimensional conductive materials. The selective permeable intermediate layer according to Claim 2.

4. The weight ratio of the one or more elastic polymer electrolyte liquids to the one or more two-dimensional conductive materials is about 1:1.5 to about 1:3.

5. The selective permeable intermediate layer according to any one of Claims 1 to 3.

5. Based on the total weight of the elastic polymer electrolyte liquid, the elastic polymer electrolyte liquid comprises: a) about 50 wt% to about 80 wt% of one or more polyphenols; b) about 5 wt% to about 40 wt% of one or more cationic polymers; and c) about 5 wt% to about 35 wt% of one or more ion transport promoting proteins. The selective permeable intermediate layer according to any one of Claims 1 to 4.

6. Based on the total weight of the elastic polymer electrolyte liquid, the elastic polymer electrolyte liquid comprises: a) about 50 wt% to about 80 wt% of one or more polyphenols; b) about 15 wt% to about 40 wt% of one or more cationic polymers; and c) about 5 wt% to about 35 wt% of one or more ion transport promoting proteins. The selective permeable intermediate layer according to any one of Claims 1 to 5.

7. Based on the total weight of the elastic polymer electrolyte liquid, the elastic polymer electrolyte liquid comprises: a) about 50 wt% to about 70 wt% of one or more polyphenols; b) about 15 wt% to about 35 wt% of one or more cationic polymers; and c) about 10 wt% to about 30 wt% of one or more ion transport promoting proteins. The selective permeable intermediate layer according to any one of Claims 1 to 6.

8. The one or more polyphenols have a molecular weight of about 100 to about 20,000 Daltons. The selective permeable intermediate layer according to Claim 6 or 7.

9. The selective permeable intermediate layer according to any one of claims 6 to 8, wherein the one or more polyphenols include one or more of tannic acid, caffeic acid, gallic acid, ellagitannin, gallotannin, ellagic acid, proanthocyanidin, and curcumin.

10. The selective permeable intermediate layer according to any one of claims 6 to 9, wherein the one or more cationic polymers include an amine functional group.

11. The selective permeable intermediate layer according to any one of claims 6 to 9, wherein the one or more cationic polymers include one or more of polyethyleneimine, poly(allylamine) hydrochloride, poly(lysine), poly(DADMAC), and chitosan.

12. The selective permeable intermediate layer according to any one of claims 6 to 11, wherein the one or more ion transport promoting proteins include one or more of bovine serum albumin, lysosome, ovalbumin, and valinomycin.

13. The selective permeable intermediate layer according to any one of claims 1 to 12, wherein the one or more two-dimensional conductive materials include one or more of reduced graphene oxide, transition metal dichalcogenide, metal organic framework, phosphorene, and nitride.

14. wherein the transition metal dichalcogenide contains one or more of MX ２ and in the formula, M is Mo, W or V, and X is S, Se or Te. The selective permeable intermediate layer according to claim 13.

15. The selective permeable intermediate layer according to any one of claims 1 to 14, wherein the intermediate layer includes both a hydrophilic domain and a hydrophobic domain.

16. The selective permeable intermediate layer according to any one of claims 1 to 15, wherein the intermediate layer has a zero-shear viscosity of less than 500 Pa·S measured at 20°C to 25°C.

17. A separator for a lithium-sulfur battery, comprising a porous substrate coated with the selective permeable intermediate layer according to any one of claims 1 to 16.

18. The separator according to claim 17, wherein the selective permeable intermediate layer coating includes pores of a size large enough to allow the transport of lithium ions through the separator.

19. The separator according to claim 17 or 18, wherein the selective permeable intermediate layer coating includes pores of a size small enough to block the transport of polysulfide species through the separator.

20. The separator according to any one of claims 17 to 19, wherein the selective permeable intermediate layer coating reduces the accumulation of polysulfide species on the surface of the selective permeable intermediate layer coating.

21. The separator according to any one of claims 17 to 20, wherein the porous substrate contains one or more polyolefins.

22. The separator according to any one of claims 17 to 21, wherein the thickness of the selective permeable intermediate layer coating is about 100 nm to about 400 nm, or about 150 nm to about 350 nm, or about 200 nm to about 300 nm.

23. A lithium-sulfur battery comprising a lithium anode, a sulfur cathode, a separator coated with a selective permeable intermediate layer according to any one of claims 1 to 16, and an electrolyte disposed between the anode and the cathode.

24. The lithium-sulfur battery according to claim 23, wherein during charging or discharging, the selective permeable intermediate layer coating reduces the accumulation of polysulfide species on the surface of the selective permeable intermediate layer coating.

25. The lithium-sulfur battery according to claim 24, wherein during charging and discharging, the selective permeable intermediate layer coating oxidizes and reduces polysulfide species.

26. The lithium-sulfur battery according to any one of claims 23 to 25, wherein during charging or discharging, the selective permeable intermediate layer coating promotes the transport of lithium ions through the separator.

27. The lithium-sulfur battery according to any one of claims 23 to 26, wherein during charging or discharging, the selective permeable intermediate layer coating blocks the transport of polysulfide species through the separator.

28. The lithium-sulfur battery according to claim 27, wherein the selective permeable intermediate layer coating blocks the transport of more than 90%, or more than 95%, or up to 99%, or more of the polysulfide species through the separator.

29. The electrolyte volume-to-capacity ratio is 5 μL mAh －１ The lithium-sulfur battery according to any one of claims 23 to 28, wherein the ratio is 5 μL mAh or less.

30. A method for generating a selective permeable intermediate layer according to any one of claims 1 to 16, the method comprising combining one or more elastic polymer electrolyte liquids with one or more two-dimensional conductive materials.

31. The method according to claim 30, wherein the two-dimensional conductive material is graphene oxide.

32. The method according to claim 31, wherein the combination of one or more elastic polymer electrolyte liquids and graphene oxide is heated to a temperature above 60 °C to reduce at least a portion of the graphene oxide.

33. The method according to any one of claims 30 to 32, wherein the weight ratio of the one or more elastic polymer electrolyte liquids to the one or more two-dimensional conductive materials is from about 1:1.5 to about 1:3.

5.

34. A method of producing a separator according to any one of claims 17 to 22, comprising coating a porous substrate with a selective permeable intermediate layer according to any one of claims 1 to 16.

35. An elastic polymer electrolyte liquid comprising a mixture of one or more polyphenols, one or more cationic polymers, and one or more ion transport promoting proteins.

36. A method for preparing the elastic polymer electrolyte liquid according to claim 35, comprising: a) combining one or more polyphenols and one or more cationic polymers; and b) adding one or more ion transport promoting proteins, wherein a) and b) are carried out under acidic conditions.

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