A polytriphenylamine derivative exhibiting a four-electron redox center as a high free radical density organic cathode†
Abstract
A high free radical density polytriphenylamine derivative, poly(1-N,1-N,4-N-triphenyl-4-N-[4-(N-[4-(N-phenylanilino)phenyl]anilino)phenyl]benzene-1,4-diamine) (PFTP) has been synthesized and investigated as the cathode material of organic free radical batteries for the first time. The molecular structure, thermal-stability, morphology, spectral characteristics and electrochemical properties of the prepared polymer were characterized by Raman spectroscopy (RS), electron spin resonance (ESR), pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), MALDI-TOF mass spectrometry, thermogravimetric analysis (TGA), ultraviolet visible spectroscopy (UV-vis), scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Also, the charge–discharge properties of the prepared polymers were studied by galvanostatic charge–discharge testing. Compared to PTPA, it was found that PFTP not only had improved thermal stability and morphology, but also exhibited obvious four-electron redox characteristics. At a discharge current of 20 mA g−1, the PFTP electrode presented a multi-stage discharge platform and an improved discharge capacity of 74.2 mA h g−1 compared to PTPA, which could be attributed to the high free radical density and the improved morphology of the obtained novel polymer. The above exploratory work made it promising to design the multi-electron redox centers of the polytriphenylamine-based polymer to obtain improved electrochemical performance.