Authors: Mariya Kalapsazova, Pavel Markov, Krassimir Kostov, Ekaterina Zhecheva, Diana Nihtianova and Radostina Stoyanova
Batteries & Supercaps 10.1002/batt.202000137
Abstract: The integration of sodium ion batteries into large-scale energy storage systems will become feasible in the case when their performance becomes less sensitive towards the ambient temperature. Herein, we demonstrate firstly the elaboration of the oxide-based electrode material with optimized layered structure and composition that is designed to work at elevated temperatures.
Through selective substitution of Mg2+ ions for Ni2+ in the three layered oxide, P3-Na2/3Ni1/2Mn1/2O2, the oxidation state of Ni ions, the cationic distribution in the layers, the sodium intercalation capacity and the rate capability is manipulated. The electrochemical behavior of P3-Na2/3Ni1/3Mg1/6Mn1/2O2 is discussed on the basis of ex-situ diffraction, microscopic and spectroscopic methods in terms of redox activity of the lattice oxygen, the reversible transfer of Mg2+ and Ni2+ ions between layers during Na+ intercalation, thermal stability of cycled electrodes and surface reactivity of the layered oxide towards the ionic liquid (IL) electrolyte. At 40 oC, the rate capability of the oxide is improved upon using an IL electrolyte rather than the carbonate-based electrolyte.