Nitroxide radical polymer/graphene nanocomposite as an improved cathode material for rechargeable lithium batteries

Abstract

The nitroxide radical polymer, poly (4-vinyloxy-2,2,6,6-tetramethyl-piperidine-N-oxyl) (PTVE), is a promising cathode material for greener and sustainable rechargeable Li batteries, but exhibits low Li electroactivity due to its poor electronic conductivity. Nanocomposite of PTVE and graphene was herein synthesized via a facile co-deposition method, and investigated with fourier transform infrared spectroscopy, scanning electron microscopy, electron spin resonance spectra, thermogravimetric analysis, cyclic voltammograms and galvanostatic charge–discharge techniques. The as-synthesized PTVE/graphene nanocomposite shows much improved Li electroactivities with a reversible one by one two-electron process redox reaction in the potential limits of 2.5–3.0V and 3.5–3.7V vs Li/Li+, respectively. A high specific capacity of 261mAhg−1 close to the theoretical capacity of PTVE based on the two-electron redox reaction (270mAhg−1) is obtained in the nanocomposite. The nanocomposite also exhibits excellent rate capability (up to 200C) and long cycle life (up to 20,000 cycles) compared with pristine PTVE. The superior electrochemical properties benefit from the intrinsic fast redox reaction of nitroxide radicals with the help of unlimited electron transport via the 3D networks of graphene, as well as the good chemical and structural stabilities of PTVE which are also strengthened by the elastic graphene networks.