Performance of Na0.44Mn1−xMxO2 (M = Ni, Mg; 0 ≤ x ≤ 0.44) as a cathode for rechargeable sodium ion batteries.

The influence of partial substitution of manganese by nickel or magnesium in Na_0.44MnO₂on cathode performance in sodium ion batteries has been investigated. Partial substitution changes the structure of parent Na_0.44MnO₂ from tunnel into layered P2-type, or a mixture of P2- and P3-type materials. Substitution smoothes the charge/discharge curves and may significantly improve capacity, albeit with a lower capacity retention relative to pristine Na_0.44MnO₂. In particular, high discharge capacities are found in the voltage range 2.0–4.2 V at 0.1 C rate for Na_0.44Mn_0.89Ni_0.11O₂ (193 mAh g⁻¹) and Na_0.44Mn_0.89Mg_0.11O₂ (188 mAh g⁻¹), with a capacity retention of 74% and 81%, respectively, after 70 cycles. [ABSTRACT FROM AUTHOR]