Rational Electrochemical Recycling of Spent LiFePO₄ and LiCoO₂ Batteries to Fe₂O₃/CoPi Photoanodes for Water Oxidation

Immense utilization of lithium-ion batteries displays great advantages in sustainable energy conversion and storage in recent decades, resulting in a large amount of disposal of spent batteries to the environment. The recycling of these spent batteries into refurbished ones or to other functional materials will not only reduce the environmental burdens but also provide new energy storage/conversion devices. One of the great challenges is that their applications usually suffer from impurities from the waste. Here, we developed an electrochemical recycling method to deposit Fe films on F-doped tin oxide substrates at −1.2 to −0.7 V versus the reversible hydrogen electrode directly using the oxalic leaching solution from the spent LiFePO₄ cathode, which quickly converted to hematite films in air at 770 °C. Further, the cobalt phosphate (CoPi)-based catalyst was photoelectrochemically deposited on these hematite films by using the citric leaching solution from the spent LiCoO₂. Both the bare hematite and hematite/CoPi photoanodes demonstrated high power conversion efficiencies for water oxidation at 0.053 and 0.13% in 1 M NaOH, respectively, suggesting a promising and robust method for solid waste recycling.