Reviving Inactive Lithium and Stabilizing Lithium Deposition for Improving the Performance of Anode-Free Lithium–Sulfur Batteries

Abstract

Anode-free lithium–sulfur batteries (AFLSBs) show a surprisingly prolonged cycle life 2-fold higher than anode-free lithium metal batteries. The principal difference is the presence of an intrinsic polysulfide (PS) shuttle between electrodes in AFLSBs. However, the underlying mechanism for the impact of PS redox species on the electrochemical performance of AFLSBs is not clearly understood. Herein, we investigate the role of PS redox species in retrieving inactive lithium for compensating lithium inventory loss using titration gas chromatography, thereby quantifying inactive lithium accumulated after several cycles. Moreover, XPS analysis reveals reduced lithium sulfide (Li2S/Li2S2) species formed through PS redox shuttle refresh inactive solid electrolyte interface (SEI) composition and stabilize the consecutive cycle lithium deposition. Interestingly, synchrotron-based operando transmission X-ray microscopy (TXM) reveals dense and granular electrodeposited lithium morphologies in AFLSBs. Therefore, the interplay between reviving inactive lithium for compensating lithium inventory loss and stabilizing lithium electrodeposition endows high electrochemical performance in AFLSBs.