High-voltage lithium-metal batteries enabled by ethylene glycol bis(propionitrile) ether-LiNO₃ synergetic additives

The employment of Li metal anodes is a key to realizing ultra-high energy batteries. However, the commercialization of lithium metal batteries (LMBs) remains challenging partially due to the thermodynamic instability and competitive oxidative decomposition of the solvent. Herein, a bi-functional electrolyte for stabilizing the interfaces of both the Li metal anode and LiCoO₂ (LCO) cathode is designed by introducing lithium nitrate (LiNO₃) through Ethylene Glycol Bis(Propionitrile) Ether (DENE). For the anode, the C₈H₁₂N₂O₂-LiNO₃ coordination-solvation contributes to forming a stable Li₃N-enhanced solid electrolyte interphase (SEI), which increases the average Li coulombic efficiency (CE) up to 98.5%. More importantly, in situ electrochemical dilatometry further reveals that the highly reversible behavior and a low volume expansion of lithium deposition are related to the stable Li₃N-enhanced SEI. The designed electrolyte enables the Li‖LCO cell to achieve an average CE of 99.2% and a high capacity retention of 88.2% up to 4.6 V after 100 cycles. This work provides a strategic guidance in developing high-voltage Li‖LCO batteries with dual electrolyte additives.