Crystal Void Fraction-Engineered Fe-S Catalysts for Self-Sustaining Li-CO₂ Mars Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Planetary Science

Background:

• Efficient energy storage is crucial for long-term Martian exploration.
• Lithium-carbon dioxide (Li-CO2) batteries offer a promising solution by utilizing Martian atmospheric CO2.
• Iron-sulfide (Fe-S) minerals, abundant on Mars, are potential cathode catalysts for these batteries.

Purpose of the Study:

• To identify a rational selection criterion for Fe-S mineral catalysts based on their structural properties.
• To establish crystal void fraction as a predictive descriptor for catalyst performance and stability.
• To optimize Li-CO2 battery performance for in-situ resource utilization on Mars.

Main Methods:

• Computational analysis correlating crystal void fraction with affinity for oxygen-containing species (Li2CO3 and singlet oxygen).
• Investigation of d-band center shifts and orbital interactions based on void fraction.
• Experimental evaluation of marcasite (a moderate void fraction Fe-S mineral) in Li-CO2 batteries.

Main Results:

• Crystal void fraction governs the affinity of Fe-S catalysts towards Li2CO3 and singlet oxygen.
• Higher void fractions enhance Li2CO3 decomposition but increase catalyst degradation from singlet oxygen.
• Marcasite, with a moderate void fraction, demonstrated an optimal balance, achieving 88% energy efficiency and 1000 hours of cycle life.

Conclusions:

• Crystal void fraction is a predictive metric for selecting Fe-S catalysts for Li-CO2 batteries, balancing activity and stability.
• This research supports the in-situ resource utilization of Martian CO2 for sustainable energy storage.
• The findings pave the way for developing robust energy storage solutions for future Mars missions.