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

Anode-free lithium-sulfur batteries (AFLSBs) showa surprisinglyprolonged 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 underlyingmechanism for the impact of PS redox species on the electrochemicalperformance of AFLSBs is not clearly understood. Herein, we investigatethe role of PS redox species in retrieving inactive lithium for compensatinglithium inventory loss using titration gas chromatography, therebyquantifying inactive lithium accumulated after several cycles. Moreover,XPS analysis reveals reduced lithium sulfide (Li2S/Li2S2) species formed through PS redox shuttle refreshinactive solid electrolyte interface (SEI) composition and stabilizethe consecutive cycle lithium deposition. Interestingly, synchrotron-based operando transmission X-ray microscopy (TXM) reveals denseand granular electrodeposited lithium morphologies in AFLSBs. Therefore,the interplay between reviving inactive lithium for compensating lithiuminventory loss and stabilizing lithium electrodeposition endows highelectrochemical performance in AFLSBs.