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

Challenges from the insulating S and Li2S2/Li2S (Li2S1-2) discharge products are restricting the development of the high-energy-density Li-S battery system. The deposition of insulating Li2S1-2 on the surfaces of S based cathodes (e.g., S and Li2S) limits the reaction kinetics, leading to inferior electrochemical performance. In this work, the impact of binders on the deposition of Li2S1-2 on S based cathodes is revealed, along with the interaction between polyvinylidene difluoride and Li2S/polysulfides. This interaction can obstruct the electrochemical reactions near the binder, leading to dense deposition of insulating Li2S1-2 that covers the cathode surface. Without such a binder, localized and uniform Li2S1-2 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 Li2S cathode delivers a gravimetric and volumetric energy density of 331.0 Wh kg(-1) and 281.5 Wh L-1, under ultrahigh Li2S loading (16.2 mg(Li2S) cm(-2)) with lean electrolyte (2.0 mu L mg(Li2S)(-1)), providing a facile but practical approach to the design of next-generation S-based batteries.

Automated summary

This study reveals the impact of binders on the deposition of Li2S1-2 on S based cathodes and the interaction between polyvinylidene difluoride and Li2S/polysulfides. Constructing a battery without binders can significantly improve electrode utilization.