Improving a Mg/S Battery with YCl(3) Additive and Magnesium Polysulfide

Rechargeable magnesium/sulfur (Mg/S) batteries are widely regarded as one of the alternatives to lithium‐ion batteries. However, a key factor restricting their application is the lack of suitable electrolyte. Herein, an electrolyte additive that can reduce the polarization voltage is developed and 98.7% coulombic efficiency is realized. The as‐prepared Mg‐ion electrolyte exhibits excellent Mg plating/stripping performance with a low overpotential of 0.11 V for plating process, and high anodic stability up to 3.0 V (vs Mg/Mg(2+)). When it is coupled with magnesium polysulfide, which has high reactivity and is homogeneously distributed on carbon matrix, the Mg/S cells deliver a good cycling stability with a high discharge capacity over 1000 mAh g(−1) for more than 50 cycles.