Reclaiming Inactive Lithium with a 2-Iodooctane Electrolyte Additive for Ultrastable Lithium Metal Batteries over a Two-Year Lifespan

Abstract A primary cause of the energy fading in high-energy-density lithium (Li) metal batteries is the accumulation of inactive Li, including inactive metallic Li caused by Li dendrite growth and Li compounds resulted from side reactions, which reduce anode utilization efficiency and hinder Li-ion transport. Therefore, it is crucial to develop electrolyte additives that can suppress Li dendrite growth and stabilize the interfacial structure. Here, we introduce 2-iodooctane into the electrolyte, which reacts at the anode and is oxidized at the cathode to generate the I3−/I− redox mediator that converts inactive Li to Li2O and recovers Li ions. Owing to the recovered inactive Li, the half-cells exhibit a high Coulombic efficiency of 99.03% with restrained Li dendrite growth. Accordingly, the symmetric cells perform tripled stability with an ultralong lifespan of 730 days at 2 mA cm−2, while the pouch cells retain an over 88% capacity after 100 cycles, demonstrating substantial commercial application potential.