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

Ojha, Manoranjan, Le Houx, James, Mukkabla, Radha, Kramer, Denis, Wills, Richard George Andrew and Deepa, Melepurath (2019) Lithium titanate/pyrenecarboxylic acid decorated carbon nanotubes hybrid - Alginate gel supercapacitor. Electrochimica Acta, 309, 253-263. (doi:10.1016/j.electacta.2019.03.211).

Abstract

A facile scalable strategy is reported for the synthesis of a hybrid of lithium titanate (Li ₄ Ti ₅ O 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 ion-uptake 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 ∼8.4 mS cm ⁻¹ at room temperature, and is found to be electrochemically stable over a wide operational voltage window of ∼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 ∼54 mF cm ⁻² , ∼4.3 F cm ⁻³ (at 0.5 mA cm ⁻² )and ∼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.

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Contributors

Author: Richard George Andrew Wills

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