Lithium titanate/pyrenecarboxylic acid decorated carbon nanotubes hybrid - Alginate gel supercapacitor

摘要

A facile scalable strategy is reported for the synthesis of a hybrid of lithium titanate (Li4Ti O-5(12) or LTO) and 1-pyrenecarboxylic acid decorated multiwalled carbon nanotubes (PCA@CNTs). LTO platelets comprising of quasi-spherical nanoparticles afford short diffusion paths for electrolyte ions. PCA@CNTs, enhance the electrical conductivity of the nearly insulating LTO by 3 orders of magnitude, thus maximizing the ionuptake capability of the hybrid. Symmetric and asymmetric supercapacitors with the LTO/PCA@CNTs hybrid supported over Ni foam substrates are assembled with a novel Li+ conducting alginate gel, in air without any inert conditions that are typically used for all LTO based devices. The gel shows an average ionic conductivity of similar to 8.4 mS cm(-1 )at room temperature, and is found to be electrochemically stable over a wide operational voltage window of similar to 2.5 V. Benefitting from the synergy of electrical double layer (EDL) storage afforded by PCA@CNTs, ion-storage by LTO through a redox reaction and EDL, and the ease ion-movement across the cell due to the open architecture of CNTs, the asymmetric LTO/PCA@CNTs hybrid cell outperforms the symmetric cells by a large margin. The best areal specific capacitance (SC), volumetric SC and energy density are similar to 54 mF cm (2), similar to 4.3 F cm(-3) (at 0.5 mA cm(-2)) and similar to 3.7 mWh cm(-3) (at a power density of 49.6 mW cm(-3)) significantly enhanced for the asymmetric LTO/PCA@CNTs hybrid cell, compared to the symmetric- PCA@CNTs and hybrid cells. The design is simple to implement and can serve as a prototype to develop a range of yet unexplored LTO/carbon nanomaterial based supercapacitors. (C) 2019 Elsevier Ltd. All rights reserved.