3D N-doped hybrid architectures assembled from 0D T-Nb2O5 embedded in carbon microtubes toward high-rate Li-ion capacitors

Herein, a unique nitrogen-doped T-Nb2O5/tubular carbon hybrid structure in which T-Nb2O5 nanoparticles are homogeneously embedded in an in-situ formed nitrogen-doped microtubular carbon is synthesized, utilizing a facile and innovative synthesis strategy. This structure addresses the poor electron conductivity and rate capability that hinder T-Nb2O5's promise as an anode for Li-ion devices. Such a distinctive structure possesses a robust framework that has ultrasmall active nanocomponents encapsulated in highly conductive carbon scaffold with hollow interior and abundant voids, enabling fast electron/ion transport and electrolyte penetration. Moreover, nitrogen-doping not only ameliorates the electronic conductivity of the heterostructure, but also induces pseudocapacitance mechanism. When evaluated in a half-cell, the as-prepared material delivers a specific capacitance of 370 F g−1 at 0.1 A g−1 within 1–3 V vs. Li/Li+ and excellent cyclability over 1100 cycles. A high energy density of 86.6 W h kg−1 and high power density of 6.09 kW kg−1 are realized. Additionally, a capacitance retention as high as 81% after 3500 cycles is achieved in an Li-ion Capacitor (LIC) with activated carbon as the cathode and nitrogen-doped T-Nb2O5/tubular carbon as the anode.