Lithiating cathodes for Li-S batteries: Regulating Li2S electrodeposition to enhance sulfur utilization

초록

The passivation of the cathode substrate by Li2S 2 S during discharge is particularly pronounced in conditions such as high S content, crucial for practical Li-S batteries. Yet, actively regulating this phenomenon through cathode substrate exploration remains a challenging task. This study unveils that Li-intercalating oxides like Nb2O5, 2 O 5 , which undergo lithiation at discharge potentials, can induce passivation-free 3D Li2S 2 S growth, while oxides such as WO3 3 and MoO2, 2 , which do not undergo lithiation at discharge potentials, exhibit 2D growth. Specifically, during discharge, the electrodeposition of Li2S 2 S kinetically inhibits lithiation, prompting lithiation from Li2S 2 S instead of from the electrolyte Li salt; this process leads to the bulk diffusion of dissociated S 2- and its 3D deposition. Utilizing a CNT cathode substrate incorporating lithiating oxides, we achieve high S utilization and high cell performance under conditions of high S loading with a lean electrolyte. This includes a discharge capacity of 1620 mAh g- 1 at 0.03 C, equivalent to 97% S utilization, and substantial capacities of 11.0 mAh cm-- 2 and 6.40 mAh cm-- 2 under high sulfur loadings of 14 mg cm-- 2 and a lean electrolyte of E/S S = 5, respectively.

키워드