Highly Reversible Anode-Free Lithium Metal Batteries Enabled by Porous Organic Cages with Subnano Lithiophilic Triangular Windows

The widespread application of anode-free lithium metal batteries (AFLMBs) is hindered by the severe dendrite growth and side reactions due to the poor reversibility of Li plating/stripping. Herein, our study introduces an ultrathin interphase layer of covalent cage 3 (CC3) for highly reversible AFLMBs. The subnano triangular windows in CC3 serve as a Li⁺ sieve to accelerate Li⁺ desolvation and transport kinetics, inhibit electrolyte decomposition, and form LiF- and Li₃N-rich solid-electrolyte interphases. Moreover, the lithiophilic backbone of CC3 homogenizes Li⁺ distribution and deposition with mitigated dendrite growth. Thus, CC3 promotes Li plating/stripping kinetics and reversibility, achieving an ultralong stability over 8000 h of the Cu@CC3 electrode. Furthermore, practical Cu@CC3/LiFePO₄ AFLMBs deliver a capacity retention (66%) over 600 cycles. This work emphasizes the effectiveness of CC3 to regulate the Li plating/stripping behavior, demonstrating the application potential of porous organic cages for enhancing the cycle life of AFLMBs.