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.