NASICON-Type NaTi2(PO4)3 Surface Modified O3-Type NaNi0.3Fe0.2Mn0.5O2 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_0.3Fe_0.2Mn_0.5O₂ surface modification is performed by a simple wet chemical method of coating NaTi₂(PO₄)₃ on the surface. The NASICON-type NaTi₂(PO₄)₃ coating layer has a special three-dimensional channel, which facilitates the rapid migration of Na⁺, and the NaTi₂(PO₄)₃ coating layer also prevents direct contact between the electrode and the electrolyte, ensuring the stability of the interface. In addition, the NaTi₂(PO₄)₃ coating layer induces part of the Ti⁴⁺ doping into the transition metal layer of NaNi_0.3Fe_0.2Mn_0.5O₂, which increases the stability of the transition metal layer and reduces the resistance of Na⁺ diffusion. More importantly, the NaTi₂(PO₄)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 NaTi₂(PO₄)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 1C 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 10C, 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.