A CO₂-Mediated Li-O₂ Battery With 3.3 V Discharge Voltage

Lithium-oxygen (Li-O₂) batteries overcome the ion-intercalation chemistry in lithium-ion batteries by employing oxygen conversion reactions beyond the solid cathode framework. However, sluggish kinetic limit practical discharge voltages below 2.85 V, establishing a "high capacity, low power output" dilemma that severely compromises achievable energy and power densities. Herein, a CO₂-mediated Li-O₂ battery (CLOB) is constructed to redefine the oxygen redox chemistry by strategically optimizing gas composition and catalytic architecture, successfully elevating the discharge voltage to 3.30 V comparable to the LiFePO₄-based lithium-ion batteries. O₂ and CO₂ are gradually reduced to form the intermediates of Li₂CO₄ and Li₂C₂O₆, and finally Li₂CO₃ as the discharge product. It leads to an equilibrium voltage of 3.30 V in a two-electrode electrochemical cell. Furthermore, iron phthalocyanine (FePc) is introduced as a soluble molecular carrier to mitigate the kinetic constraint. The demonstrated FePc-based CLOB delivers an exceptional discharge voltage of 3.30 V and the assembled pouch cell exhibits a 1.38 Ah capacity with an ultrahigh energy density of 870.1 Wh kg^-1. This voltage enhancement substantially improves energy output and offers a new paradigm for the commercialization of metal-gas batteries.