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

Challenges from the insulating S and Li₂S₂/Li₂S (Li₂S_1–2) discharge products are restricting the development of the high-energy-density Li–S battery system. The deposition of insulating Li₂S_1–2 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 Li₂S_1–2 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 Li₂S_1–2 that covers the cathode surface. Without such a binder, localized and uniform Li₂S_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 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 µL mg_Li2S⁻¹), providing a facile but practical approach to the design of next-generation S-based batteries. © 2021 Wiley-VCH GmbH