Triple effects of Sn-substitution on Na0.67Ni0.33Mn0.67O2

Layered oxides are one of the most promising cathode materials for sodium ion batteries (NIBs), however, the relatively low working voltage hinders the increase of energy density thus limiting the application scenarios of NIBs. Here we prepared and investigated a series of Sn4+ substituted Na0.67Ni0.33Mn0.67-xSnxO2 (x = 0.10, 0.20, 0.30, 0.33) and found that Sn-substitution can induce three effects: promoting O3-stack formation, smoothing the voltage profile and increasing the working voltage to ∼3.6 V. This study would enrich the knowledge of Sn-substitution and give guide to the better design of high-voltage cathode materials for NIBs.