Accelerated Polysulfide Redox in Binder‐Free Li₂S Cathodes Promises High‐Energy‐Density Lithium–Sulfur Batteries

Abstract

Abstract Challenges from the insulating S and Li 2 S 2 /Li 2 S (Li 2 S 1–2 ) discharge products are restricting the development of the high‐energy‐density Li–S battery system. The deposition of insulating Li 2 S 1–2 on the surfaces of S based cathodes (e.g., S and Li 2 S) limits the reaction kinetics, leading to inferior electrochemical performance. In this work, the impact of binders on the deposition of Li 2 S 1–2 on S based cathodes is revealed, along with the interaction between polyvinylidene difluoride and Li 2 S/polysulfides. This interaction can obstruct the electrochemical reactions near the binder, leading to dense deposition of insulating Li 2 S 1–2 that covers the cathode surface. Without such a binder, localized and uniform Li 2 S 1–2 deposition throughout the whole cathode can be achieved, effectively avoiding surface blockage and significantly improving electrode utilization. A full battery constructed with a binder‐free Li 2 S cathode delivers a gravimetric and volumetric energy density of 331.0 Wh kg −1 and 281.5 Wh L −1 , under ultrahigh Li 2 S loading (16.2 mg Li2S cm −2 ) with lean electrolyte (2.0 µL mg Li2S −1 ), providing a facile but practical approach to the design of next‐generation S‐based batteries.