Communication - O3-type layered oxide with a quaternary transition metal composition for na-ion battery cathodes: NaTi_0.25Fe_0.25Co_0.25Ni_0.25O₂

NaTi_0.25Fe_0.25Co_0.25Ni_0.25O₂ is explored as a cathode material for Na-ion batteries. Synthesized by a solid-state reaction, the compound is phase-pure with the O3-type layered structure and consists of Ti⁴⁺, Fe³⁺, Co³⁺, and Ni²⁺ according to X-ray absorption spectroscopy. The cathode delivers 163 mAh/g and 504 Wh/kg at C/20 in the first discharge with 89% capacity retention after 20 cycles and demonstrates superior rate capability with micron sized particles, in which discharge capacity at 30 C is 80mAh/g. Our results indicate that the Ti-containing quaternary material can be a potential cathode composition for Na-ion batteries.