A bifunctional hierarchical heterostructured integrated cathode based on lignin-derived carbon fiber microfilms for...

Lithium-oxygen (Li-O₂) 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-O₂ 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-O₂ battery with TT@LCMF cathode exhibited an overpotential of 0.76 V and a stable cycle life of 900 h at 100 mA g^-1 current density without illumination. The semiconductor TiO₂ in the TT@LCMF cathode produced photogenerated electrons and holes, which further reduced the overpotentials of Li-O₂ batteries during the discharge and charge process (0.48 V with illumination and 0.88 V without illumination at 500 mA g^-1 currrent density). In addition, the photogenerated electrons on the cathode can regulate the proportion and growth morphology of lithium peroxide (Li₂O₂) that generates the discharge products with illumination, thus promoting the decomposition of the discharge products during the charge process, so that the Li-O₂ batteries can still maintain a small overpotential after 50 cycles. The investigation reveals the application mechanism of photogenerated carriers in Li-O₂ batteries, which provides an important strategy for the development of multifunctional and efficient Li-O₂ cathodes.