Closed-loop recycling of spent Li6.5La3Zr1.5Ta0.5O12: from selective lithium recovery to high-efficiency sintering-aid preparation†

Abstract

Effective recycling of spent solid-state batteries (SSBs) and endowing recycled products with a “second life” show great promise for advancing the sustainable development of SSBs, which has rarely been reported in previous works. Herein, an efficient and novel strategy based on sulfur-assisted phase transformation followed by water leaching has been proposed to selectively extract Li from spent SSBs. Structural characterization indicates that the substitution of sulfur for oxygen in dodecahedral [LaO₈] can promote the collapse of the garnet structure, and the Li in the crystal lattice can be fully converted into water-soluble Li salts. Under optimized conditions, the recovery ratio of Li can be as high as 99.6% with Li leaching selectivity approaching 100%. The techno-economic analysis demonstrates that the sulfur-assisted phase transformation for the selective recycling strategy holds potential economic and environmental value in battery recycling. Additionally, the lithium extraction slag can be transformed into a highly efficient solid electrolyte sintering aid through secondary roasting, which enables the SSBs to show greatly enhanced cycling stability and rate performance via increasing the densification of the solid-state electrolyte and improving the ionic conductivity. This work offers fresh insights into recycling spent SSBs and advancing the applications of SSBs.