Recycling of High-Purity Lithium Metal from Waste Battery by Photoelectrochemical Extraction at Ultralow Overall Potential

To ease the scarcity of lithium (Li) resource and cut down on environmental pollution, an efficient, selective, inexpensive and sustainable Li recycling process from waste batteries is needed, which is yet to be achieved. Here, we report a low-potential photoelectrochemical (PEC) system that selectively and efficiently extracts Li metals from multi-cation electrolytes under 1 sun illumination. Based on the difference of redox potential, we can get rid of the disturbance of other cations (i.e., Fe, Co and Ni ions) by a bias-free PEC device to realize the extraction of high-purity Li metals on a coplanar Si-based photocathode-TiO₂ photoanode tandem device at 2 V of applied bias (far less than the redox potentials of Li⁺/Li). In such system, the extraction rate of Li metals (purity > 99.5%) exceeds 1.35 g h^-1 m^-2 with 90% of Faradaic efficiency. Long-term experiments, different electrode/electrolyte tests, and various price assessments further demonstrate the stability, compatibility and economy of PEC extraction system, enabling a solar-driven pathway for the recycling of critical metal resources.