Air‐Stable Li2S Cathode for Quasi‐Solid‐State Anode‐Free Batteries with High Volumetric Energy

Abstract Anode‐free batteries can maximize the energy density but their development is hindered by a lack of Li‐rich cathodes for compensating the irreversible Li loss. Li 2 S cathode is particularly appealing to this desire due to 2.6–4.7 folds more Li content and 4.2–6.8 times higher capacity than conventional intercalation cathodes. But its practical application is hindered by poor stability against moisture attacking in the air. Herein, a facile expendable polymer sheathing strategy toward air‐stable Li 2 S cathodes with high capacities for developing high‐performance quasi‐solid‐state anode‐free batteries without risk of cell leakage is reported. Tight protection by dense polymer barrier dramatically prolongs the lifetime of Li 2 S cathode by 2,000 times at least in the air. Such air‐stable Li 2 S cathode allows for high compatibility of anode‐free battery production with commercial schemes. More attractively, the polymer protective layer can in situ transform to multifunctional gel polymer electrolyte for releasing ionic pathways and enhancing cell performance by inhibiting LiPS loss and smoothing Li plating. With air‐stable Li 2 S cathode, the quasi‐solid‐state anode‐free cells are assembled in ambient environment to deliver superb volumetric energy density of 1093 Wh L −1 . This study may shed new light to push the commercialization of high‐energy and reliable anode‐free batteries forward.