TiO2 nanorods confined in porous V2O5 nanobelts and interconnected carbon channels for sodium ion batteries

Abstract

The limited ionic diffusion and electron transport pathway confine the rate performance and stability of TiO2 based anode material for sodium ion batteries. As regards, a typical TiO2 nanorods with a heterojunction with V2O5 nanobelts encapsulated into continuous carbon frame work were designed to promote the transport of electrons and Na+ ions as well as mitigating the volume expansion during the sodiation/desodiation process. One-dimensional (1D) TiO2 hierarchical coupling with ultrathin V2O5 nanobelts confined in continuous carbon framework is designed by combining with hydro-thermal method and aqueous solution growth mechanism at room-temperature. Such structure advantages including three-dimensional (3D) building blocks, large surface area, and the optimum porous hybrid architecture afford rich accessible sites and multiple pathways for the transfer of charge carriers, which shorten the ion transport kinetics and facilitate the mass transfer as current expands to 200 times (from 0.1 Ag1 to 20 Ag−1) as well as the buffering volume expansion advantages during repeated cycles. Simultaneously, the composition synergistic effects including the oxygen vacancies due to the substitution of Ti by V introduce the enhancements in both electron conductivity and the preferred lower Na ion insertion/extraction energy barrier. In addition, these composite is benefited from superior capacity contribution from V2O5, the abundant active reaction sites because of the exposure of the large surfaces which are beneficial from the rich pores. Such three-dimensional TiO2-V2O5 composite can accelerate the electron transportation via the highly orientated interconnected structure as well as facilitating the ion diffusion because of the larger expanded interlayer. The approach supplies a promising material model for preferred orientation active planes and higher Na+ transport kinetics. Such composite with unique structural features presented remarkable high-rate performance when tested as a anode material for sodium-ion batteries (366 mA h g−1 at ∼20 A g−1), and showed very stable sodium-storage performance (a capacity retention nearly to 100% at 5 A g−1). When employed as anode for sodium-ion hybrid capacitors (SIHCs), it delivered a maximum power density of 6.84 kW kg−1 (with 114.07 Wh kg−1 energy density) and a maximum energy density of 244.15 Wh kg−1 (with 152.59 W kg−1 power density). This work with highlights in composition synergistic effects and typical structure design supplies a promising approach to enhance the electrochemical property of sodium ion batteries, which also can be applied to different metal oxides for energy storage devices.