Lithium Carbide Prelithiation Agent Enhanced the Energy Density and Lifespan of Anode‐Free Battery

Abstract Anode‐free battery, featuring a fully lithiated cathode and a bare Cu foil, offers unparalleled energy density among lithium batteries. However, deactivation of lithium ions loss upon repeated Li metal plating/stripping results in reversible capacity decline. Binary lithium compounds have been explored as cathode prelithiation agents because of the high donor capacity, while the undesirable decomposition products and low delithiation dynamics present additional obstacles. Herein, Li 2 C 2 serves as a cathode prelithiation agent. Its decomposition is unharmful for the performance of the battery. First‐principles calculations demonstrate the feasibility of Li₂C₂ delithiation in lithium batteries. The synthesized Li 2 C 2 exhibits substantial capacity up to 1298.4 mAh g −1 and stability in dry air. The addition of Li 2 C 2 eliminates the capacity decay caused by lithium loss in anode‐free battery with LiNi 1.5 M 0.5 O 4 /LiCoO 2 cathode. The Operando XRD analysis confirms its ability to compensate for lithium loss. The 2.5 Ah anode‐free pouch cell balances the robust cycling endurance, gravimetric energy densities of 424.1 Wh kg −1 , as well as extreme power output up to 1270 W kg −1 . In summary, Li 2 C 2 plays the role of innovative cathode prelithiation additives, offering a promising solution for extending the lifespan of anode‐free batteries.