Interlayer Expanded MXene Film Cathodes with Rich Defects for Flexible 2‐Electron Oxalate‐Based Li–CO2 Batteries: A New Path to Enhanced Energy Efficiency and Durability

Abstract Aprotic Li–CO 2 batteries have garnered significant attention owing to their high theoretical energy density and potential in zero‐carbon technology. However, their practical application remains hindered by sluggish CO 2 reduction/evolution reaction (CRR/CER) kinetics and limited flexibility. While 2D graphene‐like materials are commonly employed to settle these issues, their four‐electron pathway limits efficiency and reversibility. Herein, a defect‐rich, interlayer‐expanded Ti 3 C 2 T x (Ex‐Ti 3 C 2 T x ) film cathode is presented for flexible Li–CO 2 batteries. The extended interlayer space, reduced ─OH groups, and additional uncoordinated titanium atoms of Ex‐Ti 3 C 2 T x enable abundant catalytic active sites, enhance ion and CO 2 transport, and these surface functionalizations suppress interfacial oxidation. Notably, Ex‐Ti 3 C 2 T x stabilizes the bi‐electron product Li 2 C 2 O 4 via Ti 3+ /Ti 2+ coupling bridges, effectively preventing disproportionation into Li 2 CO 3 , thereby significantly improving CRR/CER reversibility and lowering overpotential. Benefiting from these properties, Li–CO 2 batteries with Ex‐Ti 3 C 2 T x deliver a remarkable discharge capacity of 3452.33 µAh cm −2 , a low polarization potential of 0.39 V, an energy efficiency exceeding 88.9%, and an ultra‐long cycling life (>1600 h). Furthermore, the belt‐shaped flexible battery exhibits excellent flexibility and stable electrochemical performance under deformation highlighting its potential in wearable electronics. This work underscores the critical role of MXene‐based materials in bi‐electron electrocatalytic mechanisms, providing insights for advancing reversible Li–CO 2 batteries and flexible energy storage technologies.