Sub-Nano Confinement Engineering Toward Anion-Reinforced Solvation Structure to Achieve Highly Reversible Anode-Free Lithium Metal Batteries

The practical application of anode-free lithium metal batteries (AFLMBs) is impeded by poor cycling performance due to sluggish Li⁺ transport kinetics, unfavorable side reactions, and dendrite Li growth. To address these issues, ≈200 nm zeolitic imidazolate framework-8 (ZIF-8) interphase layer is introduced to enable highly reversible Li plating/stripping by electrosynthesis method. ZIF-8 interphase layer with sub-nano windows accelerates Li⁺ desolvation kinetics and thus suppresses unfavorable side reactions. Further, the internal cavities of ZIF-8 serve as an anion reservoir to modulate anion-reinforced solvation structure of Li⁺, facilitating the formation of LiF- and Li₃N-riched solid–electrolyte interphase. Thus, the Li/Cu@ZIF-8 asymmetric cell exhibits remarkable Aurbach coulombic efficiency of 99.84%, and Cu@ZIF-8/LiFePO₄ AFLMB delivers impressive capacity retention (57.8%) over 400 cycles. This work highlights the effectiveness of ZIF-8 to enable highly reversible AFLMBs and inspires the potential application of porous materials with sub-nano windows and interval cavities in anode-free batteries.