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

A Cu2 O-TiO2 photoelectrode is pr+oposed for simultaneous solar light energy harvesting and storing of electrochemical energy in an adapted lithium coin cell. The p-type Cu2 O semiconductor layer is the light harvester component of the photoelectrode and the TiO2 film performs as the capacitive layer. The rationale of the energy scheme shows that the photocharges generated in the Cu2 O semiconductor induce lithiation/delithiation processes in the TiO2 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.