Sodium-Deficient O3-Na_0.9[Ni_0.4Mn _xTi_0.6−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_0.4Mn _x Ti_0.6−x]O₂ (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 g²¹ 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.