Fig. 5: First-principles calculations.
From: A fluoroxalate cathode material for potassium-ion batteries with ultra-long cyclability
a Calculated atomic structures of K1–xFeC2O4F in the pristine, half-charging and full-charging states (x = 0, 0.5, 1), and b their corresponding partial density of states (DOS) projected onto the Fe 3d orbitals. c The reaction energy of a C2O42− decomposing into 2CO2 in the bulk of K1–xFeC2O4F as a function of the charge state x. d The partial charge density for electrons in the energy range between −2.5 eV and the Fermi level (0 eV) of the pristine (x = 0) and full-charging (x = 1) states. e The reaction scheme and kinetics of a C2O42− decomposing into 2CO2 in the bulk of K0.125FeC2O4F. Based on the Brønsted-Evans-Polanyi relation, the reaction barrier is linearly related to the reaction energy. Therefore, the reaction barrier in K0.125FeC2O4F with the lowest decomposition energy represents the minimum barrier in K1–xFeC2O4F.
