P2-type Na2/3Ni1/3Mn2/3-xTixO2 as a new positive electrode for higher energy Na-ion batteries

New electrode materials of layered oxides, Na2/3Ni1/3Mn2/3-xTixO2 (0 <= x <= 2/3), are successfully synthesized, and their electrochemical performance is examined in aprotic Na cells. A Na//Na2/3Ni1/3Mn1/2Ti1/6O2 cell delivers 127 mA h g(-1) of reversible capacity and the average voltage reaches 3.7 V at first discharge with good capacity retention.