Abstract: We report on the electrochemical properties of layered manganese oxides, with and without cobalt substituents, as cathodes in sodium ion batteries. We fabricated sub-µm sized particles of Na0.7MnO2+z and Na0.7Co0.11Mn0.89O2+z via combustion synthesis. X-ray diffraction revealed the same layered hexagonal P2-type bronze structure with high crystallinity for both materials. Potentiostatic and galvanostatic charge/discharge cycles in the range 1.5 Vâ¦3.8 V vs. Na ï¼ Na+ were performed to identify potential dependent phase transitions, capacity, and capacity retention. After charging to 3.8 V, both materials had an initial discharge capacity of 138 mA h g-1 at a rate of 0.3 C. For the 20th cycle those values reduced to 75 mA h g-1 and 92 mA h g-1 for Co-free and Co-doped samples, respectively. Our findings indicate that earlier works probably underestimated the potential of (doped) P2-type Na0.7MnO2+z as cathode material for sodium ion batteries in terms of capacity and cycle stability. Apart from doping a simple optimization parameter seems to be the particle size of the active material.
