Ti-Substituted O3-NaNiMnTiO Material with a Disordered Transition Metal Layer and a Stable Structure.

O3-type NaNiMnO (NNM) is very competitive for sodium-ion batteries (SIBs) due to its high capacity and easy production. Nevertheless, the intricate phase transitions during the charging-discharging significantly impede its practical application. This paper proposes a strategy for successfully synthesizing NaNiMnTiO (NNMT) by combining coprecipitation and a high-temperature solid-state method. This method introduces Ti elements while retaining the electrochemically active Ni content, thus, the NNMT has a high initial specific capacity of 151.4 mAh g at 1 C. It is demonstrated that introducing Ti leads to the transition metal layers becoming disordered by ex situ XRD, thus mitigating the irreversible phase transition of the material. In addition, Ti does not have an outer electron, which can reduce electron delocalization in the transition metal layer and improve the material's cyclic stability. The NNMT possesses a capacity retention rate of 60.66% after 150 cycles, much higher than the initial NNM's 18.96%. It also exhibits an excellent discharge capacity of 86.8 mAh g at 5 C. In conclusion, the cycling and rate performance of the Ti-substituted NNMT are greatly improved without capacity loss, which offers innovative concepts for the modification means of the SIBs layered oxide cathode materials.