Inhibiting and rejuvenating dead lithium in battery materials

Lithium and other alkali-metal-based batteries are promising candidates for next-generation energy-storage technologies. However, such batteries suffer from limited lifespans caused by the continuous inactivation of their electrodes during operation and even storage, creating inactivated or 'dead' Li, which is a combination of electrically insulated metallic Li and solid-electrolyte interphases (SEIs). Numerous efforts have been devoted to uncovering the origins of this inactivation and how it could be mitigated. Given that dead Li cannot be entirely prevented, rejuvenating it has emerged as a solution for prolonging the lifetimes of batteries and energy-storage systems. Here, we discuss the origins of dead Li and its effects on battery operations. We summarize the emerging challenges related to dead Li, such as SEI dissolution, dead Li migration and Li corrosion. We evaluate the limitations of the present strategies devoted to reducing the formation of dead Li, and how to recover and rejuvenate dead Li through redox chemistry and electrochemical protocols. We conclude with development opportunities in operando diagnoses and the rejuvenation of other inactivated electrode materials beyond Li chemistry in cells and large-scale systems already on the market.