Charge-Discharge Properties of a Phosphoric Acid Material System for Application in Sodium Ion Batteries

Abstract

The demand for high capacity and safe rechargeable batteries has significantly increased in recent years due to sustainable development issues. In order to supply such demand, the cost related to batteries remains a critical factor. Recently, sodium has attracted much attention as charge carrier because this element is abundant and low cost. In fact, it was found that some layered materials can be used efficiently as positive electrode materials in sodium ion batteries. Sodium is inserted between layers, which are composed of metals and oxygen. Therefore, such materials consist in 2D sodium channels. Although layered materials exhibit a high capacity, their low stability remains problematic. Furthermore, the weakness of oxygen bonds raises security issues. Herein, a novel phosphoric acid material system used as positive electrode material is proposed. In these systems, the strength of the bond between oxygen and phosphorus increase significantly the safety of the batteries. The stability of the material was thermodynamically tested and safe operation was achieved at 400 ºC. The charge-discharge properties and structural analysis of the material are reported herein.