Poly[tris(thienylphenyl)amine] Derivatives as a Performance-Improved Cathode Material for Lithium Ion Batteries

Abstract

In this work, two poly[tris(thienylphenyl)amine] derivatives, poly[tris(4-(2-thienyl)phenyl)amine] (PPT1N) and poly[4,4',4''-tris(bithienylphenyl)amine] (PPT2N) are successfully synthesized. And the chemical structure and electrochemical performance of the prepared materials are characterized by 1H NMR, UV-vis, FT-IR spectra and galvanostatic charge-discharge testing by simulated lithium ion half-cell method. The results show that the introduction of thiophene units as both electrochemically redox active moieties and "bridge" linkage into polytriphenylamine benefits the charge carrier transportation along molecular chain and optimizes the particle morphology of the resulting polymers. As a result, the obtained polymers, as cathode materials for lithium ion batteries exhibit improved specific capacity, cycling stability and rate capability, compared to that of polytriphenylamine-based cathode. Especially, the PPT1N-based electrode demonstrates a higher specific capacity of 129.3 mAh·g−1 and retains over 83% of the initial capacity with a 10 times increase in the current from 50 to 500 mA·g−1. These enhanced electrochemical performances are partly attributed to the introduction of electrochemically redox active thiophene units, the improved charge carrier transportation and the improved spherical micro-morphology.