Constructing high energy density non-aqueous Li-ion capacitors using monoclinic TiO2-B nanorods as insertion host

Abstract

We report the construction and electrochemical performance of a high power Li-ion hybrid electrochemical capacitor (Li-HEC) using monoclinic TiO₂-B nanorods as anodes with activated carbon cathodes. First, TiO₂-B nanorods are synthesized by a conventional hydrothermal approach and a subsequent ion-exchange reaction with protons. Phase formation and morphological features are investigated through X-ray diffraction and scanning and transmission electron microscopy, respectively. Li-insertion properties are evaluated in half-cell configurations and reversible insertion of 0.52 moles of Li at a current density of 100 mA g⁻¹ were found. The Li-HEC is constructed with optimized mass loading of the electrodes along with Whatman and electrospun PVdF–HFP membranes. Among them, electrospun PVdF–HFP comprising Li-HEC is found to be superior in terms of cyclability, higher energy and power densities. The electrospun PVdF–HFP comprising Li-HEC delivered the maximum energy and power densities of 23 W h kg⁻¹ and 2.8 kW kg⁻¹, respectively, with a capacitance retention of ∼73% after 1200 cycles at a current density of 1.5 A g⁻¹.