NASICON-Type NaTi₂(PO₄)₃ Surface Modified O3-Type NaNi_0.3Fe_0.2Mn_0.5O₂ for High-Performance Cathode Material 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. Among them, O3-type layered oxides are a promising cathode material for sodium-ion batteries; however, most of them suffer from slow kinetics and unfavorable structural stability, which seriously hinder their practical application. O3-NaNi 0.3 Fe 0.2 Mn 0.5 O 2 surface modification is performed by a simple wet chemical method of coating NaTi 2 (PO 4 ) 3 on the surface. The NASICON-type NaTi 2 (PO 4 ) 3 coating layer has a special three-dimensional channel, which facilitates the rapid migration of Na +, and the NaTi 2 (PO 4 ) 3 coating layer also prevents direct contact between the electrode and the electrolyte, ensuring the stability of the interface. In addition, the NaTi 2 (PO 4 ) 3 coating layer induces part of the Ti 4+ doping into the transition metal layer of NaNi 0.3 Fe 0.2 Mn 0.5 O 2, which increases the stability of the transition metal layer and reduces the resistance of Na + diffusion. More importantly, the NaTi 2 (PO 4 ) 3 coating layer can suppress the O3–P3 phase transition and reduce the volume change of the materials throughout the charge/discharge process. Thus, the NaTi 2 (PO 4 ) 3 coating layer can effectively improve the electrochemical performance of the cathode materials. The NFM@NTP3 has a capacity retention of 86% (2.0–4.0 V vs Na + /Na, 300 cycles) and 85% (2.0–4.2 V vs Na + /Na, 100 cycles) at 1 C and a discharge capacity of 107 mAh g –1 (2.0–4.0 V vs Na + /Na) and 125 mAh g –1 (2.0–4.2 V vs Na + /Na) at 10 C, respectively. Therefore, this surface modification strategy provides a simple and effective way to design and develop high-performance layered oxide cathode materials for sodium-ion batteries.