Addressing electrode passivation in lithium-sulfur batteries by site-selective morphology-controlled Li2S formation

The sulfur utilization efficiency of lithium-sulfur batteries is often limited by the uncontrolled electrodeposition of the insulating Li2S and the resulting electrode passivation. Herein, purposeful electrode and electrolyte design is used to realize site-selective three-dimensional (3D) Li2S electrodeposition and thus mitigate the above problem. Site-selective Li2S nucleation is induced at the tips of CoP nanoneedles grown on a carbon cloth electrode, and the 3D growth of Li2S at these tips without the passivation of the inner part is achieved using a LiBr-containing high-donor-number electrolyte. The controlled Li2S morphology is rationalized by considering the tip effect, the energy of Li2S binding on the electrode surface, and the solubility of Li2S in the electrolyte. Owing to the suppressed electrode passivation, CoP nanoneedle-decorated carbon cloth electrode and LiBr-containing electrolyte deliver a capacity of >1400 mAh g(s)(-1) at a current density of 0.33 A g(s)(-1). Thus, this work paves the way for the active control of Li2S morphology for high-performance lithium-sulfur batteries.