Sodium‐Deficient O3‐Na0.9[Ni0.4MnxTi0.6−x]O2 Layered‐Oxide Cathode Materials for Sodium‐Ion Batteries

Recently, increasing attention has been paid to the newly emerging area of sodium‐ion batteries, as a promising supplement for lithium‐ion batteries. Although many cathode materials have been proposed, most of these have limitations for practical applications, such as a low capacity or a poor cycling performance. Here, sodium‐deficient O3‐Na 0.9 [Ni 0.4 Mn x Ti 0.6− x ]O 2 (where x 5 0.1–0.6, abbreviated as NNMT‐9415, 9424, 9433, 9442, 9451, and 9460, respectively) materials are introduced, which can be used as the cathode in sodium‐ion batteries. Among these materials, the electrochemical behavior of materials with x 5 0.4 and 0.3 is the highest with a higher capacity and better cycling property than the other materials. These can deliver an initial capacity of about 120 mA h g 21 in a voltage range of 2.5–4.2 V with a negligible capacity loss even after 100 cycles. The rate capabilities of 82% and 64% at 1 C and 2 C current rates, respectively, are also satisfactory. The good cycling performance and high capacity make these two materials potential candidates as the cathode material for sodium‐ion batteries.