Sustainable Recovery, Surface Chemical Engineering, and Upcycling of Spent Graphite into Dual-Ion Battery

Abstract

Recycling has become an absolute necessity. Spent Lithium-ion batteries (LIBs) are hazardous waste but a potential source of purified minerals. The industrial focus on LIB recycling is mostly centered on costly and scarce cathode materials recovery. Graphite is often overlooked as it fails to generate useful revenue. Herein, the waste LIBs are recycled following an all-components-recovery route that minimizes cross-contamination. However, the surface of the recovered graphite is covered with solid electrolyte interphase (SEI) formed during its first life application. Solvent wash followed by thermal treatment revives graphite for second-life applications. Three important things to consider here are the interaction of solvent media with the preformed SEI, the role of leftover SEI in forming the second-life SEI, and the effect of regenerated SEI on second-life electrochemistry. Therefore, the nature of the solvent plays a vital role in the overall process. Utilizing water is the go-to alternative but the obtained electrochemistry from water-washed graphite is below the mark. Organic solvent dimethyl carbonate (DMC) modifies the chemical composition of the interphase in such a way that it improves second-life electrochemistry. Strong inorganic acid HCl results in the highest carbon purity and makes recovered graphite suitable for non-electrochemical applications too. Electrochemically superior DMC-washed graphite is repurposed into a dual-ion full cell that delivers an average voltage of 4.5 V and an energy density of 110 Wh kg-1. Figure 1