Ultrahigh intercalation pseudocapacitance of mesoporous orthorhombic niobium pentoxide from a novel cellulose nanocrystal template

Abstract

A facile biotemplating method has been developed to prepare mesoporous orthorhombic nobium pentoxide (T-Nb2O5) films with ultrahigh lithium ion (Li+) intercalation pseudocapacitance. Nanorod-like cellulose nanocrystals (CNs) with 5–10 nm in width and 100–300 nm in length are produced by the hydrolysis of cotton, which can serve as a novel soft templating agent enabling the straightforward synthesis of mesoporous T-Nb2O5 films. By varying the niobic-to-template ratio, it is possible to tune the surface area and crystallite dimension of the Nb2O5 films. The obtained T-Nb2O5 films show typical capacitive-dominated behaviour in the sweep rate range of 1–20 mV s−1. It delivers an initial intercalation capacity of 644 C g−1 at a current density of 0.625 A g−1, corresponding to x = 1.83 for LixNb2O5, and can still keep relatively stable capacity of 560 C g−1 after 300 cycles. Moreover, its excellent high-rate capability (450 C g−1 at 12.5 A g−1) and wider temperature adaptability present here suggests the promising of T-Nb2O5 as high-energy pseudocapacitor electrode with superior intercalation capacitive behaviour.