Solar Energy Storage Using a Cu₂ O-TiO₂ 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.