Effect of Ti doping on the structural and electrochemical performance of O3-type Na(Ni0.3Fe0.2Mn0.5)1−xTixO2 cathode materials for sodium-ion batteries

Sodium-ion batteries (SIBs) have shown great potential as energy storage devices due to their low price and abundant sodium content. In terms of current research, cathode materials remain the bottleneck for improving the performance of SIBs. Ti-doped O3-type Na(Ni0.3Fe0.2Mn0.5)1−xTixO2 (x = 0, 0.05, 0.1, 0.15) are investigated as the cathode material for sodium-ion batteries, and the results show that Ti doping can widen the layer spacing and suppress the ordering of Na+/vacancy and O3-P3 phase transition. The structurally stable Na(Ni0.3Fe0.2Mn0.5)0.9Ti0.1O2 cathode material, in particular, demonstrates enhanced rate capacity (93 mAh g−1, 2.0–4.0 V vs Na+/Na, 10 C, and 115 mAh g−1, 2.0–4.2 V vs Na+/Na, 10 C) and excellent cycling stability (87.5% capacity retention, 2.0–4.0 V vs Na+/Na, after 300 cycles, 1 C, and 82.1% capacity retention, 2.0–4.2 V vs Na+/Na, after 100 cycles, 1 C). In addition, Ti doping can effectively suppress the O3-P3 phase transition of the cathode materials and reduce the formation of the P3 phase at high voltage, which effectively suppresses the capacity decay during the charge/discharge process and reduces the irreversible capacity. As a result, the Ti doping strategy provides a simple and effective method for designing and developing high-performance layered oxide cathode materials for sodium-ion batteries.