Crystal Void Fraction‐Engineered Fe‐S Catalysts for Self‐Sustaining Li‐CO 2 Mars Batteries
Tianchen Wei, Leyi Su, Liang Wu, Yuchun Liu, Yuxin Xiao, Xingwu Zhai, Zhixin Sun, Jing Zhang, Xinyun Wang, Cong Han, Ziyu Li, Min ZhouABSTRACT
Efficient energy storage is vital for self‐sustaining Martian exploration. Li‐CO 2 batteries are promising by utilizing the Martian atmosphere (∼95% CO 2 ) as active materials. Fe‐S minerals, abundant on Mars, offer a viable candidate for cathode catalysts, yet their structural diversity necessitates a rational selection criterion. Here, we propose crystal void fraction as a governing descriptor correlating with affinity toward critical oxygen‐containing species, Li 2 CO 3 and singlet oxygen ( 1 O 2 ). Higher void fraction with decreased Fe‐S 6 octahedra packing density upshifts the d‐band center and brings the z‐containing orbitals closer to the Fermi level. Given the pronounced O‐2p z character of Li 2 CO 3 band‐edge states and the π* orbital of 1 O 2 frontier orbital, symmetry matching along surface orbitals with z‐directional components strengthens orbital coupling, correlating higher crystal void fractions with increased affinity for oxygen‐containing species. Crucially, this affinity exhibits a dual role. High void fraction promotes Li 2 CO 3 decomposition but 1 O 2 ‐induced catalyst degradation, while low void fraction exhibits the opposite tendency. Marcasite with moderate void fraction achieves an optimal balance, achieving 88% energy efficiency and 1000 h cycle life. This work establishes crystal void fraction as a predictive metric for screening suitable catalysts for achieving activity‐stability trade‐off, and provides a promising landscape for in‐situ resource utilization on Mars.