Light-Motivated SnO2 /TiO2 Heterojunctions Enabling the Breakthrough in Energy Density for Lithium-Ion Batteries.

Powering lithium-ion batteries (LIBs) by light-irradiation will bring a paradigm shift in energy-storage technologies. Herein, a photoaccelerated rechargeable LIB employing SnO2 /TiO2 heterojunction nanoarrays as a multifunctional anode is developed. The electron-hole pairs generated by the Lix TiO2 (x ≥ 0) under light irradiation synergistically enhance the lithiation kinetics and electrochemical reversibility of both SnO2 and TiO2 . Specifically, the electrons can quickly pour into the SnO2 and the generated Sn due to the more positive conduction band potentials (vs TiO2 ), and mean while the holes also promote the intercalation of Li+ into TiO2 by reaching charge balance. A remarkable increase in areal specific capacity is therefore achieved from 1.91 to 3.47 mAh cm-2 at 5 mA cm-2 . More impressively, there is no capacity loss even through 100 cycles, which is the best report for photorechargeable LIBs to date, owing to the strong and stable photoresponse current. This finding exhibits a feasible pathway to break the limitation in the energy density of LIBs by the efficient conversion and storage of solar energy.