Medium‐Entropy Alloy/In Situ N‐doped rGO Catalyst Composite for Ultrahigh Discharge Capacity and High‐Rate Cyclability in Li─CO2Mars Batteries

The immense potential of Li─CO2 batteries in mitigating CO2 emissions makes them an attractive choice for developing next‐generation high‐energy‐density alternative energy storage systems. However, insufficient Li2CO3 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─CO2Mars 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 Li2CO3 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 CO2 adsorption and the tendency toward relatively stable formation of the discharge products of Li2CO3 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─CO2Mars batteries.