Voltage effects on lithium extraction/recovery via electrochemical pumping using a La0.57Li0.29TiO3 electrolyte

Abstract

The production of lithium-ion batteries consumes large quantities of lithium resources, the demand for which will significantly increase with the growing popularity of electric vehicles. However, shortages and skyrocketing prices will become of concern if lithium is only produced through conventional methods. Although electrochemical pumping is a promising method of lithium recovery, its commercialization is hindered by its low recovery rate and low energy efficiency. In this study, we elucidate the origin of these issues by clarifying the effect of applied voltage on the lithium-ion collection rate and Faraday efficiency during an electrochemical pumping process using a La0.57Li0.29TiO3 (LLTO) electrolyte. The lithium collection rate increased exponentially with increasing overpotential. The Faraday efficiency was constant at unity below a certain cathodic overpotential, while the lithium transfer per unit energy gradually decreased with increasing overpotential. At higher overpotentials, the Faraday efficiency deviated from unity owing to electron conduction in the LLTO electrolyte, which resulted in a pronounced increase in Joule heat and, consequently, greater energy loss increased owing to the pronounced Joule heat. The lithium transfer per unit energy therefore decreased significantly with increasing applied voltage. These insights will aid in the design of more efficient electrochemical pumping processes for lithium extraction/recovery.