Oxygen Vacancy-Mediated Growth of Amorphous Discharge Products toward an Ultrawide Band Light-Assisted Li-O₂ Batteries.

Abstract

Photoassisted electrochemical reaction is regarded as an effective approach to reduce the overpotential of lithium-oxygen (Li-O₂ ) batteries. However, the achievement of both broadband absorption and long term battery cycling stability are still a formidable challenge. Herein, an oxygen vacancy-mediated fast kinetics for a photoassisted Li-O₂ system is developed with a silver/bismuth molybdate (Ag/Bi₂ MoO₆ ) hybrid cathode. The cathode can offer both double advantages for light absorption covering UV to visible region and excellent electrochemical activity for O₂ . Upon discharging, the photoexcited electrons from Ag nanoplate based on the localized surface plasmon resonance (LSPR) are injected into the oxygen vacancy in Bi₂ MoO₆ . The fast oxygen reaction kinetics generate the amorphous Li₂ O₂ , and the discharge plateau is improved to 3.05 V. Upon charging, the photoexcited holes are capable to decompose amorphous Li₂ O₂ promptly, yielding a very low charge plateau of 3.25 V. A first cycle round-trip efficiency is 93.8% and retention of 70% over 500 h, which is the longest cycle life ever reported in photoassisted Li-O₂ batteries. This work offers a general and reliable strategy for boosting the electrochemical kinetics by tailoring the crystalline of Li₂ O₂ with wide-band light.