Novel LixSiSy/Nafion as an artificial SEI film to enable dendrite-free Li metal anodes and high stability Li–S batteries

Abstract

Lithium–sulfur batteries are the most promising next-generation power source thanks to their extremely high theoretical capacity. However, the uncontrollable lithium dendrite growth and side reactions between the polysulfides and electrolyte for the Li metal anode result in a short lifespan, rapid capacity decay, low Coulombic efficiency, and safety concerns, impeding their practical development. In this work, a novel dual-layered artificial SEI on the Li metal anode is reported, which consists of organic lithiated Nafion on the top and inorganic Li_xSiS_y on the bottom. The flexible Nafion layer can not only maintain the structural integrity of the SEI, but also hinder the side reactions between soluble polysulfides and the lithium anode, while the rigid inorganic layer is beneficial for diffusion of Li ions within it and suppression of Li dendrite growth. Accordingly, the protected Li electrode can steadily withstand successive Li plating/stripping processes for over 1400 h at a current density of 1 mA cm⁻². Li–S batteries with a Li_xSiS_y/Nafion film coated Li anode exhibit better cycling stability (783 mA h g⁻¹ after 300 cycles at 0.5C) and higher rate performance (789 mA h g⁻¹ at 2.0C) than those with a bare Li anode. This work highlights the significance of rational manipulation of the interfacial properties of a working Li metal anode and provides fresh insights into achieving dendrite-free Li deposition behaviors and high-cyclability Li–S batteries.