Unraveling the Role of Earth-Abundant Fe in the Suppression of Jahn-Teller Distortion of P'2-Type NaMnO: Experimental and Theoretical Studies.

Layered NaMnO suffers from capacity loss due to Jahn-Teller (J-T) distortion by Mn ions. Herein, density functional theory calculations suggest Na[Fe Mn]O suppresses the J-T effect. The Fe substitution results in a decreased oxygen-metal-oxygen length, leading to decreases in the b and c lattice parameters but an increase in the a lattice constant. As a result, the capacity retention and rate capability are enhanced with an additional redox pair associated with Fe. Finally, the thermal properties are improved, with the Fe substitution delaying the exothermic reaction and reducing exothermic heat.