Host-Guest Synergy of COF and CoO Enables In Situ Oxygen Vacancies and Regulated Li⁺ Behavior for High-Performance Anode‑Free/Less Li Metal Batteries.

Abstract

Anode-free Li metal batteries (AFLMBs) are excellent candidates for electric vehicles and low-altitude aircrafts because of their high energy density. However, the industrialization of AFLMBs remains limited by the poor reversibility of Li⁺ deposition and stripping on Cu current collectors (CCs). In this study, a composite CC (TCMS@Cu) integrating a covalent organic framework (COF) membrane and CoO nanoparticles is constructed to address these challenges. The TCMS@Cu forms a dense COF crystalline membrane on Cu foil via epitaxial growth and incorporates lithiophilic CoO nanoparticles. The host-guest synergistic effect between the COF and CoO effectively guides Li⁺ migration into COF cavities, effectively suppressing dendrite formation and the accumulation of inactive Li. During the initial deposition process, CoO reacts with Li⁺ to generate oxygen vacancies, further enhancing the performance of the TCMS membrane. The anode-less Li metal batteries (ALLMBs) assembled with LiFePO₄ cathode achieve an exceptional cycle life of 850 cycles and a high-rate capacity retention of 94.4% at 5C. The assembled AFLMB pouch cells deliver energy densities of 288 Wh kg^-1 (LFP|CC) and 452 Wh kg^-1 (NCM811|CC) (calculated without cell can and tabs). This work provides an effective strategy for designing high performance AFLMBs and promotes the development of next-generation energy storage devices.