One-dimensional polythiophene/multi-walled carbon nanotube composite cathodes for rechargeable magnesium battery: Evidence of improved stability and electrochemically induced rearrangement in electrode morphology

Abstract

This paper showcases polythiophene/multi-walled carbon nanotube (PTh/MWCNT), synthesized via chemical in-situ oxidative method as an active cathode material for rechargeable magnesium (Mg) battery. Successful formation of the composite material is confirmed by Fourier transform-Infra Red and X-ray diffraction analysis. Morphological evaluations of the cathode materials employing field emission scanning- and transmission- electron microscopy (FESEM and TEM) reveal the composites’ one-dimensional, homogeneous phase formation. The feasibility of PTh/MWCNT composite as a prospective positive electrode for rechargeable magnesium battery is assessed using cyclic voltammetry and galvanostatic charge-discharge. Comprehensive electrochemical studies demonstrate a significantly enhanced performance of the optimized PTh/MWCNT cathode composition. A considerably high specific capacity of ∼157 mAh.g−1 coupled with appreciable coulombic efficiency (∼70%) and excellent reversibility (>100 cycles), at high current density, indicates great promise. Analysis by X-ray photoelectron spectroscopy confirms the existence of multi-polaron state of the polymer/composites providing crucial clues towards proposing a plausible mechanism of charge transport and storage. Affirmation of improved stability and electrochemically induced rearrangement in electrode morphology is clearly evidenced from the FESEM studies post charge-discharge cycles. These encouraging findings suggest PTh/MWCNT composite electrodes possess the desirable physical and electrochemical properties, to be considered as a potential polymer electrode for rechargeable Mg-battery.