Iodine-containing additive engineering for rejuvenating inactive lithium and constructing highly stable lithium metal anodes.

In this work, the effectiveness of dual-additives electrolyte consisting of iodine and caffeic acid (noted as CA@I) in improving electrochemical performance has been demonstrated both experimentally and theoretically. The full cell with a high LiFePO 4 loading (17.4 mg cm−2, 3.0 mAh cm−2) has successfully demonstrated a stable lifetime of more than 370 cycles with a capacity retention of 95.0%. [Display omitted] • A novel iodine and caffeic acid dual-additive electrolyte was proposed for Li metal batteries. • I 3 −/I− redox couple can rejuvenate inactive lithium and be revived itself at the cathode side. • The anionic polymerised caffeic acid modulates composition and improve stability of SEI. • The modified Li|Li battery achieves an ultra-long cyclelife over 7000 h at 1 mA cm−2. Inactive ('dead') lithium and conventional fragile solid-electrolyte interphase (SEI) usually cause performance degradation and safety hazards in Li-metal batteries. Recovering inactive lithium and constructing stable SEI are urgently required to enhance the capacity and lifespan of lithium metal batteries. Herein, we have designed a novel dual-additives electrolyte containing an I 3 −/I− redox couple for reviving the inactive lithium, and caffeic acid (CA) that can be anion-polymerised to modulate the composition and improve stability of the SEI. It's found that the generated I 3 −/I− redox couple can turn the inactive Li 2 O into soluble Li+, and prompt the formation of SEI composed of inorganic LiI, Li 3 N and organic RCOOLi with high stability. Density functional theory (DFT) calculations indicate that the diffusion potential barrier of Li+ is significantly lower on the LiI-rich SEI interface, which can not only accelerate the transport of Li+ at the interface, but also effectively prevent I 3 − from attacking Li metal. Benefiting from this elaborate dual-additives electrolyte design, the symmetrical-cells present a superior electrochemical performance, i.e., high critical current density up to 10 mA cm−2, ultra-long lifespan over 7000 h at 1 mA cm−2, and over 2500 cycles under harsh conditions of high temperature (50 °C) and high current density (5 mA cm−2). In addition, as a proof of concept for practical applications of Li-metal batteries, Li|LiFePO 4 full cell delivers excellent cycle stability and rate performance with low hysteresis voltage at a high cathode loading of 17.4 mg cm−2. [ABSTRACT FROM AUTHOR]