Partially Manganese-Substituted Li-Rich Antiperovskite (Li₂Fe)SeO Cathode for Li-Ion Batteries

Lithium-rich antiperovskites are promising high-capacity cathode materials for next-generation Li-ion batteries. In this study, partially Mn-substituted (Li₂Fe_1-<i>y</i> Mn _<i>y</i> )-SeO (<i>y</i> = 0.1-0.4) cathode materials were synthesized via solid-state reaction. Structural analysis confirmed the cubic antiperovskite phase with lattice expansion proportional to the Mn content, while thermal analysis revealed congruent melting behavior with improved thermal stability. Electrochemical characterization demonstrated good cycling stability across all Mn-substituted compositions. The (Li₂Fe_0.9Mn_0.1)-SeO cathode exhibited an initial discharge capacity of 123 mAh/g and excellent cycling stability, but higher Mn content led to a performance decline. Battery optimization for (Li₂Fe_0.9Mn_0.1)-SeO, including electrolyte selection and electrode formulation, had a pronounced impact on performance. Notably, increasing the active material ratio from 70 to 85 wt % in the electrode mixture resulted in a significantly enhanced discharge capacity, achieving 203 mAh/g in the second cycle and maintaining 85% of this value (173 mAh/g) after 100 cycles. These results underscore the importance of composition and electrode design in maximizing the electrochemical performance of Li-rich antiperovskites.