High-efficiency lithium isotope separation via electrodeposition: Mechanistic insight and material design principles

The development of green and efficient lithium isotope separation methods is of strategic importance for sustainable nuclear energy applications. Electrodeposition represents a promising approach, yet the fundamental separation mechanisms and the role of cathode materials require further clarification. This work systematically investigates the mechanism of lithium isotope separation through electrodeposition by integrating computational simulations with experimental validation. The results indicate that the lighter isotope 6 Li exhibits weaker solvation interactions and a reduced energy barrier for electron transfer, leading to its preferential deposition. The kinetic isotope effect during the charge transfer step (Li⁺ + e⁻ → Li) is identified as the dominant factor in the separation process, contributing significantly more than the limited fractionation induced by diffusion. Two categories of cathode materials—deposition-type (Ni, Cu, stainless steel) and alloy-forming (Zn, Al, Sn)—were evaluated, revealing a strong positive correlation between charge transfer resistance and separation performance, with stainless steel achieving the highest separation factor of 1.048. Furthermore, voltage-dependent studies demonstrate that separation efficiency decreases under high overpotentials due to a transition from charge transfer control to diffusion-limited kinetics. These findings provide fundamental insights into the electrodeposition-based separation mechanism and establish practical guidelines for developing efficient lithium isotope separation systems.