Versatile Spinel Ferrites MFe 2 O 4 (M = Co, Zn, Ni, Cu) Enhance Dischargeability and Efficiency in Li‐CO 2 Mars Batteries with Mixed Solvent Electrolytes

Abstract Li‐CO 2 batteries as next‐generation electrochemical energy storage devices not only  potentially help reducing the greenhouse effect using CO 2 for energy storage, but also offer high‐energy‐density (1876 Wh kg −1 ) secondary batteries. However, the primary challenges for this technology are the low applied current density and limited rechargeability. In this work, a rechargeable Li‐CO 2 Mars battery is operated in a simulated Martian atmosphere using [EMIm] + [BF4] ‐ ionic liquid (IL) as an additive in the dimethyl sulfoxide (DMSO)‐based electrolyte and a spinel MFe 2 O 4 (M = Co, Ni, Cu, Zn) nanocomposite catalysts with conductive multiwalled carbon nanotubes  support prepared by a single‐step chemical co‐precipitation method. The combination of the catalysts and ionic liquids enables the battery to exhibit an ultra‐high discharge capacity exceeding 31346.3 mAh g −1 , sustaining over 100 cycles with a cutoff capacity of 1000 mAh g −1 at a current density of 500 mA g −1 . Furthermore, post‐cycling studies and first‐principles calculations reveal enhanced CO 2 adsorption, favorable reaction toward Li 2 C 2 O 4 formation, and high reversibility of the catalysts aiding toward significantly high dischargeability and long cycle life. Overall, this work contributes to the design of suitable, inexpensive, durable catalysts and novel electrolytes for Li‐CO 2 Mars batteries for its practicalization on Earth and beyond for Mars exploration.