Towards a Safe Lithium–Sulfur Battery with a Flame‐Inhibiting Electrolyte and a Sulfur‐Based Composite Cathode

Abstract

Of the various beyond‐lithium‐ion batteries, lithium–sulfur (Li‐S) batteries were recently reported as possibly being the closest to market. However, its theoretically high energy density makes it potentially hazardous under conditions of abuse. Therefore, addressing the safety issues of Li‐S cells is necessary before they can be used in practical applications. Here, we report a concept to build a safe and highly efficient Li‐S battery with a flame‐inhibiting electrolyte and a sulfur‐based composite cathode. The flame retardant not only makes the carbonates nonflammable but also dramatically enhances the electrochemical performance of the sulfur‐based composite cathode, without an apparent capacity decline over 750 cycles, and with a capacity greater than 800 mA h −1 g −1 (sulfur) at a rate of 10 C. Fire away : A nonflammable sulfur composite cathode has been shown to maintain extremely stable electrochemical activity over 750 cycles and exhibit a discharge capacity greater than 800 mA h −1 g −1 (sulfur) at a high rate of 10 C in a flame‐inhibiting electrolyte. The safe electrolyte was generated from a phosphite additive that participates in interfacial reactions on the cathode and accelerates Li‐ion diffusion more than tenfold.