Convergent approach to transition metal ion mitigation via surface-engineered boehmite separator and cathode reinforcement for high-voltage lithium metal batteries

Abstract

Enhancing high-energy density lithium metal batteries (LMBs) for energy storage can be achieved using high-voltage cathodes like LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523). However, stabilizing Li metal anodes faces challenges due to harmful side reactions caused by the migration of transition metal (TM) ions from the cathode to the electrolyte and Li metal anode. In this study, a surface-engineered particle coating on the functional separator with superior wettability and flame retardancy is developed, addressing safety risks in high-voltage operations and providing effective shielding against TM ion leakage. Additionally, a single-crystal LiNbO₃ (LNO) coating is applied to the NCM523 cathode to enhance its structural integrity under severe operating conditions. The combined modifications result in superior cycling performance, improved capacity retention, > 90 % reduction in TM ion crossover, and increased stability in high-voltage operations. This study offers valuable insights into advancing high-energy density LMBs, showing that surface-engineered separators and single-crystal LNO cathode coatings can significantly enhance performance. The proposed approach provides a promising solution for enabling high-voltage operations in mid‑nickel cathode systems for practical LMB applications.