Direct Epitaxial Growth of Polycrystalline MOF Membranes on Cu Foils for Uniform Li Deposition in Long-life Anode-free Li Metal Batteries

Anode-free Li-metal battery (AFLMB) is being developed as the next generation of advanced energy storage devices. However, the low plating and stripping reversibility of Li on Cu foil prevents its widespread application. A promising avenue for further improvement is to enhance the lithophilicity of Cu foils and optimise their surfaces through a metal-organic framework (MOF) functional layer. However, excessive binder usage in the current approaches obscures the active plane of the MOF, severely limiting its performance. In response to this challenge, MOF polycrystalline membrane technology has been integrated into the field of AFLMB in this work. The dense and seamless HKUST-1 polycrystalline membrane was deposited on Cu foil (HKUST-1 M@Cu) via an epitaxial growth strategy. In contrast to traditional MOF functional layers, this binder-free polycrystalline membrane fully exposes lithophilic sites, effectively reducing the nucleation overpotential and optimising the deposition quality of Li. Consequently, the Li plating layer becomes denser, eliminating the effects of dendrites. When coupled with LiFePO4 cathodes, the battery based on the HKUST-1 membrane exhibits excellent rate performance and cycling stability, achieving a high reversible capacity of approximately 160 mAh g-1 and maintaining a capacity retention of 80.9 % after 1100 cycles.