Na3V2(PO4)3 Nanofibers As a High Performance Cathode Material for Sodium Ion Battery

Sodium ion batteries have emerged as attractive and potential energy storage systems to substitute lithium ion battery especially in large-scale energy storage systems (ESSs) based on abundance and low cost of sodium source.

However, ionic radius of Na⁺ is larger than Li⁺, the structure of materials becomes more important when Na⁺ is inserted into or extracted from the material. Thus, it seems very necessary to introduce adequate material that has structural stability to express good electrochemical performance.

Recently, sodium super ion conductor (NASICON) - Na₃V₂(PO₄)₃ have attained much interest because it possesses large interstitial spaces through which sodium ion can diffuse. Na₃V₂(PO₄)₃ shows 118mAh/g theoretical discharge capacity at 3.4 V vs Na/Na⁺ in V⁴⁺/V³⁺ redox couple. However, its low electrical conductivity due to phosphate, significantly limits its electrochemical performance. So, the realization of theoretical capacities is difficult. In addition, Na₃V₂(PO₄)₃ shows severe capacity fading at high rate because of its low sodium ion diffusivity. These structural properties limit its electrochemical performance and practical applications, especially when rate performance is a prerequisite.

We noticed that a 1D morphology and structure on an electrode material can effectively enhance its electrochemical performance by enhancing electronic/ionic conductivity, the benefits of 1D have well demonstrated in lithium ion batteries electrode materials.

In this point of view, we prepare the electrospun nanofibers of NASICON-Na₃V₂(PO₄)₃ through a typical electrospinning technique and report on the correlation between its improved electrochemical properties and the morphological feature of nanofibers.