The Na0.9Ni0.45MnxTi0.55-xO2 (0 <= x <= 0.55) series of layered oxides was synthesized using a solid-state method and the materials in this series were studied as positive electrode materials in sodium cells. All compositions resided in a phase pure O3 solid solution. Compared to the Ti-free composition, Na0.9Ni0.45MnxTi0.55-xO2 has improved capacity retention without sacrificing reversible capacity and average voltage. Na(0.9)Ni(0.45)Mn(x)Ti(0.55-x)O(2)delivers similar to 197 mAh/g of reversible capacity in a voltage range of 1.5-4.5 V with an average voltage of similar to 3.27 V. Energy density available based on metallic sodium is estimated to be approximately 643 Wh/kg or 2805 Wh/L. Increasing the Ti content beyond this composition results in increased average voltage, increased polarization and a reduction in cycling performance. (C) 2017 Elsevier Ltd. All rights reserved.