Lithium‐sulfur batteries have been identified as an ultimate successor to lithium‐ion batteries due to their unique properties such as extremely high theoretical specific capacity (1672 mAh g−1), low cost, abundance of elemental sulfur on earth's crust and environmental friendliness. However, the insulating nature and volume expansion (approximately 76 %) of elemental sulfur, shuttling of polysulfides between the two electrodes and poor interfacial properties of lithium metal anode with non‐aqueous liquid electrolytes still hinder the commercialization of this system. In order to mitigate the shuttling of polysulfides between two electrodes, several strategies have been adopted, including optimizing the compositions, lithium salt and additives of non‐aqueous liquid electrolytes, and replacing the non‐aqueous liquid electrolyte with ionic liquids (ILs), solid polymers, superionic conductors, and quasi‐solid‐state electrolytes. This review article comprehensively covers the architecture, working principles of lithium‐sulfur batteries, the state‐of‐the‐art electrolytes, their types, properties, advantages, and limitations. The importance of electrolyte additives in enhancing the safety issues of lithium‐sulfur batteries is also emphasized. Here, we provide an overview of recent developments in different types of electrolytes for lithium‐sulfur batteries, focusing on electrochemical properties, and more specifically discussing issues related to polysulfide shuttles.

The influence of electrolyte additives on the electrochemical and interfacial properties of SiO x -based anodes for lithium–sulfur batteries (Li–S) was systematically investigated. Four different electrolyte additives, namely, lithium nitrate, vinylene carbonate (VC), vinyl ethylene carbonate, and fluoroethylene carbonate (FEC), were added to the bare electrolyte comprising 1 M LiTFSI in tetraethylene glycol dimethyl ether/1,3 dioxolane in a ratio of 1:1 (v/v). The self-extinguishing time (SET) of the liquid electrolytes was measured. The 2032-type half-cells composed of Li/SiO x /Si/C were assembled, and their charge −discharge studies were analyzed at the 0.1 C-rate. Upon cycling, the electrode materials were subjected to surface morphology and differential scanning calorimetry analyses. The interfacial properties of SiO x -based electrodes were investigated by electrochemical impedance spectroscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy studies. Among the electrolytes examined, FEC-added electrolytes offered the lowest SET and interfacial resistance values. The superior charge–discharge properties of FEC-added electrolytes were attributed to the formation of a stable solid electrolyte interface layer on the electrode surface. The surface chemistry studies revealed the formation of Li2CO3 and ROCO2Li peaks on the electrode surface.

The poly(ethylene oxide)-based hybrid solid polymer electrolytes (HSPE) of different compositions comprising Li 0.5 La 0.5 TiO 3 (LLTO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) have been prepared by hot-press method. The prepared membranes were characterized by differential scanning calorimetry (DSC), thermogravimetric (TG), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR), and tensile analyses. By assembling Li/HSPE/Li symmetric cells, the electrochemical and interfacial properties such as Li + transference number, lithium dendrite, and compatibility of HSPE with lithium metal were studied at 60 °C. The ionic conductivity measurements revealed that HSPE membrane containing 20% Li 0.5 La 0.5 TiO 3 exhibited a maximum value of 8.7 × 10 −4 S cm −1 at 60 °C. The addition of LLTO as a filler not only enhanced the ionic conductivity and thermal and mechanical stabilities but also improved the electrochemical and interfacial properties appreciably. The enhanced performance of HSPE was attributed to the interaction between the polymeric host and the added filler, which was further confirmed by NMR and FTIR studies.