A bifunctional hierarchical heterostructured integrated cathode based on lignin-derived carbon fiber microfilms for high performance photo-assisted Li-O battery.

Lithium-oxygen (Li-O) batteries are expected to be the next generation of energy storage batteries, but due to high overpotential, short cycle life and low rate-performance, its further application and development are limited. The introduction of illumination into Li-O batteries will effectively improve the charge/discharge reaction rate. Here, we designed a heterostructured integrated electrode based on lignin-derived carbon fiber microfilms (TT@LCMF), which possess excellent bifunctions of electrocatalysis and photocatalysis. The Li-O battery with TT@LCMF cathode exhibited an overpotential of 0.76 V and a stable cycle life of 900 h at 100 mA g current density without illumination. The semiconductor TiO in the TT@LCMF cathode produced photogenerated electrons and holes, which further reduced the overpotentials of Li-O batteries during the discharge and charge process (0.48 V with illumination and 0.88 V without illumination at 500 mA g currrent density). In addition, the photogenerated electrons on the cathode can regulate the proportion and growth morphology of lithium peroxide (LiO) that generates the discharge products with illumination, thus promoting the decomposition of the discharge products during the charge process, so that the Li-O batteries can still maintain a small overpotential after 50 cycles. The investigation reveals the application mechanism of photogenerated carriers in Li-O batteries, which provides an important strategy for the development of multifunctional and efficient Li-O cathodes.