Unstable and deficient supplies of lithium resources have led to the development of alternative battery systems such as sodium-ion batteries. Herein, P-type Na0.6Mn0.65Ni0.25Co0.10O2 cathode materials were synthesized by a co-precipitation and solid-state reaction method. When the calcination temperature was changed from 700 to 1000°C, Na0.6Mn0.65Ni0.25Co0.10O2 had a different morphology and crystalline structure; however, a P3-type structure was formed only at 700°C, and P2-type structured cathodes could be obtained at 800, 900, and 1000°C. Their electrochemical performances were evaluated with 2032 coin-type half cells. Among them, the P2-type cathode calcinated at 900°C, exhibited a high specific discharge capacity of 148 mAh g−1, and a stable cycling performance at a 0.2 C rate for 150 cycles.