Medium‐Entropy Alloy/In Situ N‐doped rGO Catalyst Composite for Ultrahigh Discharge Capacity and High‐Rate Cyclability in Li─CO _2Mars Batteries

Abstract The immense potential of Li─CO ₂ batteries in mitigating CO ₂ emissions makes them an attractive choice for developing next‐generation high‐energy‐density alternative energy storage systems. However, insufficient Li ₂ CO ₃ decomposition during recharging deactivates the catalyst, reducing the dischargeability and cycle life. Herein, a medium‐entropy quaternary alloy (QA) catalyst comprising of the metals Mn, Zn, Co, and Ni is designed with in situ N‐doped reduced graphene oxide (NrGO) using a multielement metal organic framework (MZIF) (QA@NrGO). The uniformly dispersed quaternary alloy with high disorder and the synergy between the NrGO and QA help Li─CO _2Mars batteries deliver an ultrahigh discharge capacity of 50605 mAh g ⁻¹ at the high current density of 500 mA g ⁻¹ and a maximum cycle life of 240 cycles. Ex situ post‐cycling physicochemical investigations reveal the formation of disc‐shaped Li ₂ CO ₃ discharge product on the active sites and nearly complete decomposition on charging, confirming the excellent reversibility. Further, the density functional theory (DFT) studies show that improved CO ₂ adsorption and the tendency toward relatively stable formation of the discharge products of Li ₂ CO ₃ and amorphous carbon helped achieve the excellent electrochemical performance. The designed medium entropy alloy (MEA) catalyst provides a pathway for developing low‐cost, highly active bifunctional catalysts for Li─CO _2Mars batteries.