Freestanding Flexible Li2S Paper Electrode with High Mass and Capacity Loading for High‐Energy Li–S Batteries

Lithium–sulfur (Li–S) batteries are a very appealing power source with extremely high energy density. But the use of a metallic‐Li anode causes serious safety hazards, such as short‐circuiting and explosion of the cells. Replacing a sulfur cathode with a fully‐lithiated lithium sulfide (Li₂S) to pair with metallic‐Li‐free high‐capacity anodes paves a feasible way to address this issue. However, the practical utility of Li₂S cathodes faces the challenges of poor conductivity, sluggish activation process, and high sensitivity to moisture and oxygen that make electrode production more difficult than dealing with sulfur cathodes. Here, an efficient but low‐cost strategy for easy production of freestanding flexible Li₂S‐based paper electrodes with very high mass and capacity loading in terms of in situ carbonthermal reduction of Li₂SO₄ by electrospinning carbon is reported. This chemistry enables high loading but strong affinity of ultrafine Li₂S nanoparticles in a freestanding conductive carbon‐nanofiber network, meanwhile greatly reducing the manufacturing complexity and cost of Li₂S cathodes. Benefiting from enhanced structural stability and reaction kinetics, the areal specific capacities of such cathodes can be significantly boosted with less sacrificing of high‐rate and cycling capability. This unique Li₂S‐cathode design can be directly applied for constructing metallic‐Li‐free or flexible Li–S batteries with high‐energy density.