New Low Cost Sulfide Electrolytes for All Solid State Batteries

Abstract

The low cost, safe and high energy storage technology is needed to ensure a continuous energy supply from renewal energy sources. However, current Li-ion batteries (LiBs) are facing challenges to fulfil the safety and high energy and power demands of fast-growing market of electric vehicles (EVs). In particular, liquid organic electrolytes used in conventional LIBs have raised the safety issues due to serious fire risk. Solid state batteries (SSBs) are considered to provide better safety as compared to LIBs because of solid electrolytes (SEs) are used in SSBs instead of flammable organic liquid based electrolytes [1-4].The various types of solid electrolytes have already been reported for SSBs which can be divided into oxides, sulfides, halides and polymers based on their properties, advantages and disadvantages [5]. Among these solid electrolytes, sulfide solid electrolytes have advantages over other due to high conductivity and ductile nature of sulfides [6]. The discovery of Li10GeP2S12 solid electrolyte called LGPS structured sulfide electrolyte have shown great potential to replace liquid electrolyte as ionic conductivity of LGPS was found 1.2×10-2 S cm-1 at room temperature comparable to the conductivity of organic liquid electrolyte [7]. However, Li10GeP2S12 electrolyte suffers with poor cyclability in solid state batteries due to reduction of Ge+4 ions to Ge0, and instable against lithium metal anode. Moreover, germanium (Ge) is a rare and expensive element, which limits the industrial application of Li10GeP2S12 [8, 9].Therefore, in the present work, we have developed LGPS structured based new Ge free solid electrolytes with high conductivity and better electrochemical stability. The phase identification of newly synthesized solid electrolytes is done by X-ray diffractometer technique along with Rietveld refinement analysis. The conductivity of prepared solid electrolytes is determined by electrochemical impedance spectroscopy. The ionic conductivity of newly synthesised electrolytes has reached upto 0.67 mS cm-1 at room temperature. The electrochemical analysis of prepared solid electrolytes is done using Li-metal in both side (in symmetric cell) as well as using standard cathode and anode materials (full cell).