Solar Energy Storage Using a Cu 2 O-TiO 2 Photocathode in a Lithium Battery.

A Cu 2 O-TiO 2 photoelectrode is pr+oposed for simultaneous solar light energy harvesting and storing of electrochemical energy in an adapted lithium coin cell. The p-type Cu 2 O semiconductor layer is the light harvester component of the photoelectrode and the TiO 2 film performs as the capacitive layer. The rationale of the energy scheme shows that the photocharges generated in the Cu 2 O semiconductor induce lithiation/delithiation processes in the TiO 2 film as a function of the applied bias voltage and light power. A photorechargeable lithium button cell drilled on one side recharges with visible white light in ≈9 h in open circuit. It provides an energy density of ≈150 mAh g -1 at 0.1 C discharge current in dark, and the overall efficiency is 0.29%. This work draws a new approach for the photoelectrode role to advance in monolithic rechargeable batteries.