NASICON-Type NaTi(PO) Surface Modified O3-Type NaNiFeMnO 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-NaNiFeMnO surface modification is performed by a simple wet chemical method of coating NaTi(PO) on the surface. The NASICON-type NaTi(PO) coating layer has a special three-dimensional channel, which facilitates the rapid migration of Na, and the NaTi(PO) coating layer also prevents direct contact between the electrode and the electrolyte, ensuring the stability of the interface. In addition, the NaTi(PO) coating layer induces part of the Ti doping into the transition metal layer of NaNiFeMnO, which increases the stability of the transition metal layer and reduces the resistance of Na diffusion. More importantly, the NaTi(PO) 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(PO) 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 and a discharge capacity of 107 mAh g (2.0-4.0 V vs Na/Na) and 125 mAh g (2.0-4.2 V vs Na/Na) at 10, 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.