Enhancing Na-storage property of Na3V2(PO4)3 via porous structure Design：From the perspective of carbon source optimization

The inborn low electronic conductivity of NASCION-type Na3V2(PO4)3 (NVP) restricts its widespread commercial applications. Traditionally carboreduction method could add a thin carbon-layer on the surface of the particles and enhance its conductivity to some extent, while the underlying mechanism about the reducing agent categories is blurred. In this paper, the mechanism of various frequently-selected carbon sources in the carbothermal process has been explored in detail, and the Na-storage property of NVP has been optimized focusing on the categories of the carbon sources. Owning to the acid etching effect of citric acid, carbon-coated NVP (NVP@C) particles synthesized via adopting citric acid as carbon source display tiny particle size as well as porous Na-storage structure. The construction of porous Na-storing structure, coupled with evenly carbon-coating, upgrades the dynamics of ion and electron transportation effectively, enhancing its Na-storing performances. The optimal experiments indicates that NVP@C prepared with citric acid with the overdose coefficient of 125 % (CR125%-NVP) exhibits the optimal electrochemical performances. In detail, CR125%-NVP showcased the initial discharging specific capacities of 116.2 and 101.3 mAh g−1 at 0.1C and 10 C, respectively. It also performed perfect cycle stability, with a capacity retention of 88.9 % after 500 cycles at 10 C rate.