A novel and simple aluminium/sol–gel-derived amorphous aluminium oxide multilayer film with high energy density†
Herein, a novel aluminium/amorphous aluminium oxide (Al/AmAO) multilayer film was fabricated, which exhibited enormous potential application in the energy storage field due to its low leakage current, high operating voltage and high energy density. Specifically, (a) its leakage current density was remarkably suppressed (stabilized at ∼5.4 × 10−5 A cm−2); (b) its operating voltage was drastically enhanced to 591 MV m−1; and (c) its energy density was as high as 13.9 J cm−3. The amorphous aluminium oxide thin film was prepared via a facile sol–gel and spin-coating method. Its outstanding electric properties were attributed to the interfacial evolution of the newly-formed dense aluminium oxide (NAO) freshly developed at the Al/AmAO interface during the application of a positive voltage. Furthermore, the electric characteristics and growth mechanism of NAO were investigated. The results revealed that NAO, possessing an ultrahigh resistivity of ∼9.4 × 1012 Ω cm, endowed Al/AmAO with excellent energy storage density and limited leakage current. The NAO growth model, which originates from the transformation of the amorphous aluminium oxide and chemical reaction of the aluminium electrode, was proposed to deeply understand interfacial evolution behaviour. The novel and simple multilayer film, which achieved excellent properties via interfacial evolution rather than the traditional methods for improving the dielectric properties of dielectric materials, offers a convenient and effective approach for the design of high-performance dielectric capacitors.