Electrolytes For Lithium-sulfur Batteries Research Articles

Metal Organic Frameworks as Polysulfide Reaction Modulators for Lithium Sulfur Batteries: Advances and Perspectives.

Currently, lithium sulfur (Li-S) battery with high theoretical energy density has attracted great research interest. However, the diffusion and loss process of intermediate lithium polysulfide during charge-discharge hindered the application of the Li-S battery in modern life. To overcome this issue, metal organic frameworks (MOFs) and their composites have been regarded as effective additions to restrain the LiPS diffusion process for Li-S battery. Benefiting from the unique structure with rich active sites to adsorb LiPS and accelerate the LiPS redox, the Li-S batteries with MOFs modified exhibit superior electrochemical performance. Considering the rapid development of MOFs in Li-S battery, this review summarizes the recent studies of MOFs and their composites as the sulfur host materials, functional interlayer, separator coating layer, and separator/solid electrolyte for Li-S batteries in detail. In addition, the promising design strategies of functional MOF materials are proposed to improve the electrochemical performance of Li-S battery.

Illuminating Polysulfide Distribution in Lithium Sulfur Batteries; Tracking Polysulfide Shuttle Using Operando Optical Fluorescence Microscopy.

High-energy-density lithium sulfur (Li-S) batteries suffer heavily from the polysulfide shuttle effect, a result of the dissolution and transport of intermediate polysulfides from the cathode, into the electrolyte, and onto the anode, leading to rapid cell degradation. If this primary mechanism of cell failure is to be overcome, the distribution, dynamics, and degree of polysulfide transport must first be understood in depth. In this work, operando optical fluorescence microscope imaging of optically accessible Li-S cells is shown to enable real-time qualitative visualization of the spatial distribution of lithium polysulfides, both within the electrolyte and porous cathode. Quantitative determinations of spatial concentration are also possible at a low enough concentration. The distribution throughout cycling is monitored, including direct observation of polysulfide shuttling to the anode and consequent dendrite formation. This was enabled through the optimization of a selective fluorescent dye, verified to fluoresce proportionally with concentration of polysulfides within Li-S cells. This ability to directly and conveniently track the spatial distribution of soluble polysulfide intermediates in Li-S battery electrolytes, while the cell operates, has the potential to have a widespread impact across the field, for example, by enabling the influence of a variety of polysulfide mitigation strategies to be assessed and optimized, including in this work the LiNO3 additive.

Advanced Polymers in Cathodes and Electrolytes for Lithium-Sulfur Batteries: Progress and Prospects.

Lithium-sulfur (Li-S) batteries, which store energy through reversible redox reactions with multiple electron transfers, are seen as one of the promising energy storage systems of the future due to their outstanding advantages. However, the shuttle effect, volume expansion, low conductivity of sulfur cathodes, and uncontrollable dendrite phenomenon of the lithium anodes have hindered the further application of Li-S batteries. In order to solve the problems and clarify the electrochemical reaction mechanism, various types of materials, such as metal compounds and carbon materials, are used in Li-S batteries. Polymers, as a class of inexpensive, lightweight, and electrochemically stable materials, enable the construction of low-cost, high-specific capacity Li-S batteries. Moreover, polymers can be multifunctionalized by obtaining rich structures through molecular design, allowing them to be applied not only in cathodes, but also in binders and solid-state electrolytes to optimize electrochemical performance from multiple perspectives. The most widely used areas related to polymer applications in Li-S batteries, including cathodes and electrolytes, are selected for a comprehensive overview, and the relevant mechanisms of polymer action in different components are discussed. Finally, the prospects for the practical application of polymers in Li-S batteries are presented in terms of advanced characterization and mechanistic analysis.

Accelerated Single Li-Ion Transport in Solid Electrolytes for Lithium-Sulfur Batteries: Poly(Arylene Ether Sulfone) Grafted with Pyrrolidinium-Terminated Poly(Ethylene Glycol).

Polymeric solid electrolytes have attracted tremendous interest in high-safety and high-energy capacity lithium-sulfur (Li─S) batteries. There is, however, still a dilemma to concurrently attain high Li-ion conductivity and high mechanical strength that effectively suppress the Li-dendrite growth. Accordingly, a rapidly Li-ion conducting solid electrolyte is prepared by grafting pyrrolidinium cation (PYR+ )-functionalized poly(ethylene glycol) onto the poly(arylene ether sulfone) backbone (PAES-g-2PEGPYR). The PYR+ groups effectively immobilize anions of Li-salts in Li-conductive PEGPYR domains phase-separated from PAES matrix to enhance the single-ion conduction. The tailored PAES-g-2PEGPYR membrane shows a high Li-ion transference number of 0.601 and superior ionic conductivity of 1.38mScm-1 in the flexible solid state with the tensile strength of 1.0MPa and Young's modulus of 1.5MPa. Moreover, this PAES-g-2PEGPYR membrane exhibits a high oxidation potential (5.5V) and high thermal stability up to 200(C. The Li/PAES-g-2PEGPYR/Li cell stably operates for 1000h without any short circuit, and the rechargeable Li/PAES-g-2PEGPYR/S cell discharges a capacity of 1004.7mAhg-1 at C/5 with the excellent rate capability and the prominent cycling performance of 95.3% retention after 200 cycles.

Highly Concentrated Electrolytes for Lithium Sulfur Batteries – the Role of the Anion(s)

Lithium-sulfur batteries (Li-S) have attracted a lot of attention as a alternative/complement to lithium-ion batteries (LIBs) – due to both high energy density, availability, and inexpensive materials used.[1]Yet, dissolution of sulfur from the C/S cathode and subsequent shuttling of lithium polysulfides (LiPS) to the anode as well as the instability of the Li metal anode itself are true scientific and technological challenges. Advancing in the field of electrolytes is one promising way to overcome both issues.Switching from the standard 1 M electrolyte design of LIBs to highly concentrated electrolytes (HCEs) may both prevent the dissolution of LiPSs and hinder dendrite formation at the lithium metal anode.[2]Here we combine experimental methods and computational approaches to investigate several HCEs based on various Li-salts in several standard organic solvents. Experimentally we targeted electrochemical properties, local electrolyte structure, and physico-chemical properties, with focus on the role(s) of the Li-salt anions. Furthermore, to predict the solubility of sulfur the conductor like screening model for real solvents (COSMO-RS), a computational fluid phase thermodynamic approach, was used.[3] Overall, the challenges and opportunities associated with the use of HCEs in Li-S batteries will be addressed, also highlighting potential areas for future research and development.References Peng et al., "Drastic effect of salt concentration in ionic liquid on performance of lithium sulfur battery." Journal of the Electrochemical Society 169.5 (2022): 050515.Suo et al., "A new class of solvent-in-salt electrolyte for high-energy rechargeable metallic lithium batteries." Nature communications 4.1 (2013): 1481.Jeschke and P. Johansson, "Predicting the Solubility of Sulfur: A COSMO‐RS‐Based Approach to Investigate Electrolytes for Li–S Batteries." Chemistry–A European Journal 23.38 (2017): 9130-9136.

Phosphorous-Based Heterostructure for the Effective Catalysis of Polysulfide Reactions with Phase Changes in High-Sulfur-Loading Lithium-Sulfur Batteries.

High sulfur loading and long cycle life are the design targets of commercializable lithium-sulfur (Li-S) batteries. The sulfur electrochemical reactions from Li2 S4 to Li2 S, which account for 75% of the battery's theoretical capacity, involve liquid-to-solid and solid-to-solid phase changes in all Li-S battery electrolytes in use today. These are kinetically hindered processes that are exacerbated by a high sulfur loading. In this study, it is observed that an in situ grown bimetallic phosphide/black phosphorus (NiCoP/BP) heterostructure can effectively catalyze the Li2 S4 to Li2 S reactions to increase the sulfur utilization at high sulfur loadings. The NiCoP/BP heterostructure is a good polysulfide adsorber, and the electric field prevailing at the Mott-Schottky junction of the heterostructure can facilitate charge transfer in the Li2 S4 to Li2 S2 liquid-to-solid reaction and Li+ diffusion in the Li2 S2 to Li2 S solid-state reaction. Consequently, a sulfur cathode with the NiCoP/BP catalyst can deliver a specific capacity of 830 mAh g-1 at the sulfur loading of 6mg cm-2 for 500 cycles at the 0.5 C rate. High sulfur utilization is also possible at a higher sulfur loading of 8mg cm-2 for 440 cycles at the 1 C rate.

An intrinsic safe siloxane ether-based electrolyte for lithium-sulfur batteries at high temperatures

As the next candidate of secondary batteries, lithium-sulfur (Li-S) batteries are hampered by short cycle life and safety issues caused by combustion of electrolytes and unstable cycling performance generated by Li dendrites growth, which become more serious when Li-S batteries are operated at high temperatures. To solve these problems, an intrinsic flame-retardant siloxane ether-based electrolyte, 2.5 M LiFSI/tetrapropoxysilane (TPOS), is innovatively investigated in Li-S batteries with sulfurized pyrolyzed poly(acrylonitrile) (SPAN) cathode at 80 ℃. This electrolyte exhibits desirable flame retardancy, unique solvation structure and excellent interfacial stability. Particularly, this electrolyte performs outstandingly in cathode protection derived from the robust and flexible electrolyte/electrode interphases simultaneously for Li metal anode and SPAN cathode. Li-S batteries delivered a reversible capacity of 760 mAh gSPAN−1 (1535 mAh gsulfur−1) and a capacity retention of 98.4 % after 85 cycles at 1C and 80 ℃. This work provides the concept and paves the way to develop high temperature Li-S batteries.

Homogenous conduction: Stable multifunctional gel polymer electrolyte for lithium-sulfur batteries

The low sulfur utilization rate and polysulfide shuttle are the main reasons that hinder the practical process of lithium-sulfur batteries. Here, an effective structural engineering strategy of multifunctional gel polymer electrolyte (GPE) by electrospinning was proposed. The HCNF@HPAN-GPE for lithium-sulfur batteries contained halloysite-base carbon nanofibers (HCNF) offered abundant active sites as sulfur fixation layer and halloysite-base polyacrylonitrile (HPAN) provided ion transport channel as ion transport layer. Both layers were abundant in the halloysite nanotubes as “transduction segment” and established the synergistic interface conduction. The HCNF@HPAN-GPE exhibited an ionic conductivity of 8.01 × 10−3 S cm−1. Therefore, the HCNF@HPAN-GPE displayed excellent interface compatibility and stabilized lithium deposition/ stripping over 800 h. Meanwhile, it demonstrated an initial discharge specific capacity of 1461.2 mA h g−1 at 0.1 C and an ultra-low-capacity attenuation of 0.056 % per cycle of 800 cycles at 1 C. In sum, this study may provide a novel strategy for the effective design of GPE toward the high performance lithium-sulfur batteries.

Polymer Electrolytes for Lithium-Sulfur Batteries: Progress and Challenges

The lithium-sulfur battery has garnered significant attention from both researchers and industry due to its exceptional energy density and capacity. However, the conventional liquid electrolyte poses safety concerns due to its low boiling point, hence, research on liquid electrolytes has gradually shifted towards solid electrolytes. The polymer electrolyte exhibits significant potential for packaging flexible batteries with high energy density owing to its exceptional flexibility and processability, but it also has inherent disadvantages such as poor ionic conductivity, high crystallinity, and lack of active groups. This article critically examines recent literature to explore two types of polymer electrolytes, namely gel polymer electrolyte and solid polymer electrolyte. It analyzes the impact of polymers on the formation of lithium dendrites, addresses the challenges posed by multiple interfaces, and investigates the underlying causes of capacity decay in polymer solid-state batteries. Clarifying the current progress and summarizing the specific challenges encountered by polymer-based electrolytes will significantly contribute to the development of polymer-based lithium-sulfur battery. Finally, the challenges and prospects of certain polymer solid electrolytes in lithium-sulfur battery are examined, thereby facilitating the commercialization of solid polymer electrolytes.

Suppression of Polysulfide Dissolution and Shuttling with Diphenyl Disulfide Electrolyte for Lithium Sulfur Batteries

Lithium-sulfur (Li-S) systems have been rising stars in new battery technologies beyond lithium-ion battery rea, but the dissolution and shuttle of lithium polysulfide seriously deteriorate the cycling performance. Herein, we proposed diphenyl disulfide (DPDS) as the electrolyte additive for Li-S batteries. DPDS can interact with the discharge intermediate S2- 4/S2- 6 ions, changing the stable form of lithium polysulfide in the electrolyte, inhibiting the shuttle of lithium polysulfide, and protecting the lithium anode. The initial discharge specific capacity of a Li-S battery with conventional electrolyte at 0.5 C is 1352.6 mAh/g, and the specific capacity of a Li-S battery with 200 cycles is 790.5 mAh/g. The initial discharge specific capacity of the battery containing 5.0 wt.% DPDS electrolyte at 0.5 C was 1296.3 mAh/g, and the capacity after 200 cycles was 899.9 mAh/g.

Electrochemical Characteristics of Novel Fluorinated Ether Solvent for Lithium-Sulfur Batteries

Introduction In recent years, the development of electric airplanes, large drones, and other equipment has created a need for batteries with high energy density and high power density. Lithium-sulfur batteries have been investigated as such batteries. Electrolyte solutions applying carbonate solvents and ether solvents have been developed as electrolyte for lithium-sulfur batteries1. An electrolyte with ether-based solvents is lighter than that with carbonate-based solvents, so the former is expected to be an electrolyte for lithium sulfur batteries with high energy density. However, lithium-sulfur batteries based on ether solvents have difficulty in reversible charge-discharge reactions due to the dissolution of lithium polysulfide (Li2S x ) that occurs during the charge-discharge process2. In this study, we investigate the electrochemical characteristics of electrolytes to apply a new fluorinated ether (C14) which is resistant to elution of Li2S x . Experimental Sulfur-carbon composite (S-C) was prepared by compositing activated carbon (C-novel, Toyo Tanso) and sulfur in a ratio of 35:65 by weight using a thermal impregnation method. S-C was used as the active material and mixed with acetylene black (AB, DENKA), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) to prepare a slurry. The cathode was obtained by coating the obtained slurry on an aluminum foil by a doctor blade method. An electrochemical cell was assembled with the obtained cathode as the working electrode, Li foil as the counter electrode, and LiTFSI dissolved in a mixture of dioxolane (DOL), dimethoxyethane (DME), and C14 at a concentration of 1 mol L-1 as the electrolyte. In order to clarify the electrochemical characteristics of the lithium sulfur battery with these electrolytes, constant current charge-discharge tests were conducted using the electrochemical cell described above. To clarify the coordination state of the solvent to lithium ions and lithium polysulfide in the electrolyte, IR spectra were measured for these electrolytes. Results and Discussion In the IR spectra for the solutions of Li2S x dissolved in DME, the intensity of the peak attributed to the asymmetric stretching of the C-O-C bond, which can be seen at around 1090 cm-1, increases with increasing concentration of Li2S x . The change in peak intensity appears to be due to the coordination of the structure of the diether in DME to the Li+ of Li2S x . On the other hand, in the IR spectra of Li2S x immersed in C14, the intensity of the corresponding peak was found to be similar to that of C14 only, regardless of the concentration of Li2S x . The results indicate that C14 is hard to coordinate to Li2Sx. This may be due to the fact that the functional group with fluorine in the structure of C14 is an electron-withdrawing group, which delocalizes the electrons located around O in the diether and weakens the coordinative force to Li2Sx. As a result of the constant-current charge-discharge test, it was confirmed that the voltage stagnated at about 2.3 V in the charge curves of the cell to which 1M LiTFSI / DOL : DME = 1 : 1 by vol.% was applied. The stagnation of the voltage is considered to be due to the shuttle reaction caused by the coordination of DME to lithium polysulfide and its dissolution into the electrolyte during the charge-discharge process. On the other hand, in the charge-discharge curves of the cell with 1M LiTFSI / C14, the stagnation of voltage that was observed in the cell with 1M LiTFSI / DME could not be confirmed, and it was turned out that the irreversible capacity was small. This should be due to the inability of C14 to coordinate with Li2S x . Acknowledgement A part of this research was conducted under a subcontract (JPNP15005) from the New Energy and Industrial Technology Development Organization (NEDO), a national research and development corporation. Reference 1) L. Gordin et al, ACS Appl. Mater. Interfaces, 6 (2014) 8006−80102) B. Zhang et al, ACS Energy Lett., 6 (2021) 537−546

Sulfur solubility in sulfolane electrolytes for lithium-sulfur batteries

The solubility of sulfur in sulfolane and sulfolane solutions of lithium salts [LiBF4, LiClO4, LiPF6, LiSO3CF3 and LiN(SO2CF3)2], promising electrolytes for lithium-sulfur batteries, was determined by UV-vis spectroscopy. It was found that the solubility of sulfur in sulfolane at 30°C is 82.0 mM, and in sulfolane solutions of lithium salts (1 M) is 4-9 times lower than in pure sulfolane. The dependence of sulfur solubility on the concentration of lithium salts is not linear, it is 32.9 and 5.8 mM for sulfolane solutions of 0.5 М LiClO4 and 2.35 M LiClO4, respectively.

Unraveling the lithium iodide-mediated interfacial process in lithium-sulfur batteries: An in situ AFM study

Among various energy storage devices, lithium-sulfur batteries have attracted widespread attention due to their high theoretical energy density and specific capacity. To improve the performance and realize practical applications of lithium-sulfur batteries, it is crucial to unravel the dynamic evolution and reaction mechanism at the electrode/electrolyte interfaces during cycling. Nevertheless, the details are still not well known despite generous efforts, which need more in situ and non-destructive imaging characterizations. Herein, we have combined AFM with an electrochemical workstation to dynamically visualize the morphological evolution and structural changes of the interfacial process, which reveals the lithium iodide-mediated interfacial reactions in lithium-sulfur batteries. In situ measurements showed that the electrode surface was coated by a reticular layer consists of elemental iodine and polyether with lithium iodide additive during charging, which could effectively prevent insolube sulfides from gathering on the surface and improve the cycling performances of lithium-sulfur batteries. These findings shed new light on the interfacial mechanism and establish design ideas for the future development of better electrolytes for lithium-sulfur batteries.

3D Asymmetric Bilayer Garnet Hybridized High-Energy-Density Lithium-Sulfur Batteries

Li7La3Zr2O12 (LLZO) has high ionic conductivity and stability against a Li metal anode making it a promising solid electrolyte for Lithium-Sulfur batteries. However, typically reported discharge capacity does not achieve theoretical. Therefore, we addressed this by forming a stable sulfur cathode/LLZO interface through a poly(ethylene oxide) (PEO)-based interlayer, with a small amount of catholyte used to maintain physical contact and ionic conduction between sulfur cathode and the PEO-based interlayer. With a thin bilayer LLZO and the stabilized sulfur cathode/LLZO interface, the hybridized Li-S batteries achieved an initial discharge capacity of 1307 mAh/g at a current density of 0.2 mA/cm2 (0.03C) at room temperature (22°C) without any indication of a polysulfide shuttle. With specific optimization, an energy density of 1308 Wh/L and 485 Wh/kg is achievable.The mechanisms regarding the cell stabilization are presented: 1). X-ray Diffraction and X-ray Photoelectron Spectroscopy indicate that the PEO-based interlayer which physically separates the sulfur cathode and LLZO, is both chemically and electrochemically stable with LLZO. 2). Due the physical separation between liquid electrolyte and LLZO through the PEO-based film, the proton/Li+ exchange with the moisture in liquid electrolytes was avoided. 3). PEO-based interlayer can adapt to the stress/strain associated with sulfur volume expansion during lithiation to protect LLZO from failure.

Nanoscale Ionic Materials for Nafion Based Nanocomposites Membranes As Single Lithium-Ion Conducting Polymer Electrolytes for Lithium Sulfur Batteries

Currently, rechargeable batteries with the lithium–sulfur (Li–S) chemistry has attracted great interest as one of the most promising candidates for next generation electrochemical energy storage systems. Research into these high energy density devices is critical to the development of thinner, lighter, and lower cost battery systems. One of the biggest obstacles for practical applications of Li-S batteries is caused by the soluble nature of the highly ordered lithium polysulfides (Li2Sn) in the organic electrolytes and induce a so-called “shuttle effect”. A solid-state electrolyte (SPEs) could be a valid alternative in terms of reducing the polysulfides dissolution and shuttle, as well as to protect the lithium metal anode and to minimize dendrite formation, which is beneficial for improving the safety and cycle life of Li−S batteries. SPEs are typically dual-ion conductor systems both cations and anions are mobile and cause a concentration polarization leading to poor performances of batteries. Recently, single lithium-ion conducting solid polymer electrolytes (SLIC-SPEs) have been proposed for polymer electrolytes, where anions are covalently bonded to the polymer, inorganic backbone, or immobilized by anion acceptors and only the Li+ cation will contribute to a permanent flow of charge. They have advantages over conventional dual-ion conducting SPEs such as unity transference number, absence of harmful effect of anion polarization, extremely low rate of Li dendrite growth and immobilization of the lithium polysulfides in the lithium-sulfur (Li-S) batteries. Polymer electrolytes based on ionomers (e.g., Nafion) with easily ionizable groups (e.g., sulfonic groups covalently bonded to the polymer side-chains, −CF2SO3 −) are promising thanks to the high concentration of weakly coordinating anions (counterions). In this work, lithiated Nafion and Nafion-nanocomposites membranes based on Nanoscale Ionic Materials (NIMs) were synthesized, and their ionic conductivity and lithium transference number were investigated in common nonaqueous organic solvents (EC/PC and Glymes).A thorough and systematic study of the lithium-ion transport was conducted by p 1H and 7Li pulsed field gradient (PFG) NMR spectroscopy and electrochemical impedance spectroscopy (EIS), while the mechanical properties of the film electrolytes have been tested by dynamic mechanical analysis (DMA) in a wide temperature range. The electrochemical studies have been conducted both in Li/Li symmetric cell and in secondary Li-S cells. The preliminary results are very interesting, showing ionic conductivities of the order of 5 × 10-4 S/ cm at 25°C satisfactory properties in terms of stability window and stability of the lithium stripping. The lithium transport number is very close to unity thus confirming the complete immobilization of the negative charge carriers.

Recent advances in the cathode materials and solid-state electrolytes for lithium sulfur batteries

Lithium-sulfur batteries (LSBs) have sparked a lot of attention due to their high theoretical energy density and cost-effectiveness. However, several challenges, notably unstable cycle life and low sulfur consumption, have hampered the development of workable LSBs for commercial use. Most of these challenges arise from the cathode materials and liquid electrolytes. This mini-review attempts to highlight the current advancements in cathode materials and solid-state electrolytes for the development of next-generation LSBs.

High Efficiency, Low Polysulfides Solubility Electrolytes for Lithium Sulfur Batteries

Lithium-sulfur (Li-S) battery is one of the most promising next generation energy storage systems because of its high energy density, low cost and environmental benignity. 1 However, their practical application is still hindered by the severe shuttle effect of polysulfides and poor stability of lithium metal anode (LMA). 2 The electrolyte is critical to enable full potential of Li-S batteries because its formulation and structure determine the solubility of the polysulfides. It also determines properties of the solid electrolyte interphase (SEI) formed on LMA surface which acts as a kinetic barrier for the continuous reactions between the electrolyte and the LMA. 2,3 This work reports low-polysulfides-solubility electrolytes (LPSEs) for Li-S batteries, in which new solvents with low-polysulfide-solubility and good Li metal stability are used to improve the overall performance of Li-S cells. By using the optimized LPSE, the capacity retention and the Coulombic efficiency of the Li-S batteries are greatly improved compared to the cells using the conventional electrolyte adopted in Li-S batteries. In addition, the LPSE can also significantly reduce the cell self-discharge compared to the baseline electrolyte. The systematic investigations and fundamental insights into LPSEs can guide further design of advanced electrolytes for Li-S batteries. The details will be discussed during the presentation.

Diphenyl guanidine vulcanization accelerators enable sulfurized polyacrylonitrile cathode for high capacity and ether-compatible by fast kinetic

Sulfurized polyacrylonitrile (SPAN) cathode shows excellent electrochemical performance in carbonate electrolyte for lithium-sulfur batteries. However, the limited redox conversion rate of SPAN cathode in ether electrolyte would lead to high solubility of the intermediate polysulfide Li2Sn(n ≤ 4) and shuttling, resulting in a low performance of corresponding lithium-sulfur battery, even though ether-based electrolytes are more suitable in terms of Li metal anode. In addition, SPAN is comparatively lower sulfur loading (<50 wt%) reduced its value. Improving the sulfur loading and accelerate the redox conversion of SPAN to be compatible with ether electrolyte will be one of the most promising cathode of lithium-sulfur batteries. Here, we introduced a sulfurized polyacrylonitrile cathode (SPAN-DG) with high sulfur loading (52 wt%) and high conductivity prepared by diphenylguanidine as vulcanization accelerator into lithium-sulfur battery based on ether electrolyte. This study found that SPAN-DG cathode with high conductivity can fast reaction kinetics and successfully inhibit the dissolution of lithium polysulfide and shuttle in ether electrolytes, shows good electrochemical performance. SPAN-DG cathode deliver a specific capacity of 879 mAh g−1 and 661 mAh g−1 (based on the mass of cathode) at rates of 0.1C and 1C (1C = 700 mA g−1), respectively.

Understanding Structural and Transport Properties of Dissolved Li2 S8 in Ionic Liquid Electrolytes through Molecular Dynamics Simulations.

Lithium-sulfur batteries with high energy density are considered as one of the most promising future energy storage devices. However, the parasitic lithium polysulfides shuttle phenomenon severely hinders the commercialization of such batteries. Ionic liquids have been found to suppress the lithium polysulfides solubility, diminishing the shuttle effect effectively. Herein, we performed classical molecular dynamics simulations to explore the microscopic mechanism and transport behaviors of typical Li2 S8 species in ionic liquids and ionic liquid-based electrolyte systems. We found that the trifluoromethanesulfonate anions ([OTf]- ) exhibit higher coordination strength with lithium ions compared with bis(trifluoromethanesulfonyl)imide anions ([TFSI]- ) in static microstructures. However, the dynamical characteristics indicate that the presence of the [OTf]- anions in ionic liquid electrolytes bring faster Li+ exchange rate and easier dissociation of Li+ solvation structures. Our simulation models offer a significant guidance to future studies on designing ionic liquid electrolytes for lithium-sulfur batteries.

New High Donor Electrolyte for Lithium-Sulfur Batteries.

The unparalleled theoretical specific energy of lithium-sulfur (Li-S) batteries has attracted considerable research interest from within the battery community. However, most of the long cycling results attained thus far relies on using a large amount of electrolyte in the cell, which adversely affects the specific energy of Li-S batteries. This shortcoming originates from the low solubility of polysulfides in the electrolyte. Here, 1,3-dimethyl-2-imidazolidinone (DMI) is reported as a new high donor electrolyte for Li-S batteries. The high solubility of polysulfides in DMI and its activation of a new reaction route, which engages the sulfur radical (S3 •- ), enables the efficient utilization of sulfur as reflected in the specific capacity of 1595mAhg-1 under lean electrolyte conditions of 5 μLelectrolyte mgsulfur -1 . Moreover, the addition of LiNO3 stabilizes the lithium metal interface, thereby elevating the cycling performance to one of the highest known for high donor electrolytes in Li-S cells. These engineered high donor electrolytes are expected to advance Li-S batteries to cover a wide range of practical applications, particularly by incorporating established strategies to realize the reversibility of lithium metal electrodes.