Double-Shelled Hollow SiO2 @N-C Nanofiber Boosts the Lithium Storage Performance of [PMo12 O40 ]3.

Abstract

Polyoxometalates (POMs)-based materials, with high theoretical capacities and abundant reversible multi-electron redox properties, are considered as promising candidates in lithium-ion storage. However, the poor electronic conductivity, low specific surface area and high solubility in the electrolyte limited their practical applications. Herein, a double-shelled hollow PMo12 -SiO2 @N-C nanofiber (PMo12 -SiO2 @N-C, where PMo12 is [PMo12 O40 ]3- , N-C is nitrogen-doped carbon) was fabricated for the first time by combining coaxial electrospinning technique, thermal treatment and electrostatic adsorption. As an anode material for LIBs, the PMo12 -SiO2 @N-C delivered an excellent specific capacity of 1641 mA h g-1 after 1000 cycles under 2 A g-1 . The excellent electrochemical performance benefited from the unique double-shelled hollow structure of the material, in which the outermost N-C shell cannot only hinder the agglomeration of PMo12 , but also improve its electronic conductivity. The SiO2 inner shell can efficiently avoid the loss of active components. The hollow structure can buffer the volume expansion and accelerate Li+ diffusion during lithiation/delithiation process. Moreover, PMo12 can greatly reduce charge-resistance and facilitate electron transfer of the entire composites, as evidenced by the EIS kinetics study and lithium-ion diffusion analysis. This work paves the way for the fabrication of novel POM-based LIBs anode materials with excellent lithium storage performance.