In this study, a new class of contenders for high-voltage and high-capacity positive electrode materials with the composition NaxLi0.7-xNi1-yMnyO2 (0.03 < x <= 0.25, 0.5 <= y <= 0.8) was synthesized by thermal treatment; these positive electrode materials synthesized by Na+/Li+ exchange using P3-NaxLi0.7-xNi1-yMnyO2 (0.5 <= y <= 0.8) as the precursor exhibited a mixture of layered and spinel structures. The (dis) charge voltage-capacity curve of materials with these compositions significantly varied according to the residual Na and Mn content. Notably, HT-NaxLi0.7-xNi1-yMnyO2 (x = 0.093, y = 0.67) exhibited a maximum discharge capacity of 261 mA h g(-1) at an average voltage of 3.36 Vat 25 degrees C (between 2.0 and 4.8 V), which translates to an energy density of 943 W h kg(-1). The obtained electrochemical performance is rationalized by the phase fractions of layered and spinel structures, which is triggered by the residual Na and Mn content in NaxLi0.7-xNi1-yMnyO2. (C) 2016 Elsevier B.V. All rights reserved.