A two-step method to prepare P2-type layered oxide materials for stable sodium-ion batteries via a precursor and sintering temperature control

Abstract

With the surging demand for green energy and renewable energy, as well as the shortage and uneven distribution of global lithium resources, sodium-ion batteries are gaining increasing attention as competitive alternatives. Due to their advantages of high energy density, high safety performance and environmental friendliness, P2 layered oxides have wide application prospects as the positive electrode of sodium ion batteries. However, their practical applications face numerous obstacles due to their complex phase transitions at high voltages, leading to poor cycling stability and rate capability. In this study, a P2-type Na_0.67Ni_0.2Mn_0.8O₂ layered oxide cathode material was successfully prepared via a two-step method using ultra-nano-sized precursors. Meanwhile, the sintering temperature was optimized for its influence on phase as well as the electrochemical properties of cathode material for sodium-ion batteries. The materials were characterized in terms of their morphology, structure, and electrochemical properties using SEM, XRD, EDX, and galvanostatic charge–discharge tests. Compared to the traditional one-step solid-state method, the PS-900 material obtained by a two-step approach exhibited a reversible capacity of over 150 mA h g⁻¹ at 0.1 C and the capacity retention reached nearly 70% after 200 cycles at 1 C. These results indicate the widespread potential application of the novel P2-type layered oxide cathode material in sodium-ion batteries.