Photo‐Assisted Li–S Batteries With 2D High‐Entropy Oxide Nanosheets: Coupling Built‐In Electric Field for Ultra‐High Photoelectric Energy Conversion

ABSTRACT The integration of solar energy into rechargeable battery systems represents a pivotal advancement in sustainable energy technology. Herein, we develop a photo‐assisted lithium–sulfur battery (PALSB) that synergistically enables light energy harvesting, conversion, and electrochemical energy storage. Its multifunctional photocathode consists of 2D polycrystalline La 0.65 Sr 0.35 Co 0.20 Ni 0.19 Fe 0.24 Cr 0.18 Cu 0.19 O 3 high‐entropy oxide (LSCO‐HEO) nanosheets with grain boundaries. Owing to the distinct surface work functions of its crystal facets, a spontaneously formed built‐in electric field at the binary facet junction effectively suppresses the recombination of photogenerated carriers, thereby substantially enhancing photo‑chemical‑electrical energy conversion efficiency. Moreover, optimal band alignment between LSCO‐HEOs and polysulfides enables direct participation of photoexcited electrons and holes in sulfur reduction and oxidation, respectively. Light‐induced electron redistribution in LSCO‐HEOs generates more dynamic and complementary highly active catalytic sites that effectively inhibit polysulfide shuttling, lower Li 2 S nucleation barriers, and enhance sulfur redox reaction kinetics. As a result, the PALSB achieves an ultra‐high photoelectric energy conversion efficiency of 12.98% and exhibits exceptional cycling stability over 1000 cycles at 8.0 C, with a minimal capacity decay of only 0.025% per cycle. This work introduces a breakthrough strategy for direct solar‐to‐chemical energy conversion within batteries, opening avenues for high‐efficiency photoelectrochemical energy storage.