Bi/Bi2O3/TiO2 heterojunction photocathode for high-efficiency visible-light-driven lithium-sulfur batteries: Advancing light harvesting and polysulfide conversion

Integrating solar-electrical energy conversion and electrical-chemical energy storage functions within a single device offers a promising strategy for efficient light harvesting, conversion, and storage of renewable solar energy. Herein, we develop visible-light-driven photoelectrochemical Li2S6-based lithium-sulfur batteries (VPLSBs) for simultaneous energy conversion and storage, employing a versatile Bi/Bi2O3/TiO2 photocathode as both a light harvester and redox catalyst. The narrowed band gap of photocathode minimizes photoelectron-hole recombination, enabling efficient light-to-electrical energy conversion. Its energy level alignment with Li-S electrochemical potentials facilitates the photocarriers' participation in polysulfide conversions, supporting electrical-to-chemical energy storage. Under visible light, the Bi/Bi2O3/TiO2 photocathode exhibits a photoelectrocatalysis effect, enhancing interfacial charge transfer, reducing Li2S deposition resistance, and ensuring stable Li2S plating/stripping. Additionally, the bare photo-charging process achieves an overall energy conversion-storage efficiency of 2.58 %. The VPLSB demonstrates an exceptional specific capacity of 1484 mA h g−1 over 900 cycles, maintaining an apparent energy efficiency of 100.2 % at 0.2 mA cm−2.