Effects of different carboxylic acid substituents on the electrochemical performance of polythiophene anode materials for lithium-ion batteries

Abstract

The effect of different carboxylic acid substituents on the electrochemical performance of polythiophene anode materials was discussed. In terms of cycle and rate performance, isophthalic acid substituted polythiophene (P3-TBDCOOH) outperforms formic and parabenzoic acid substituted polythiophenes (P3-TCOOH and P3-TBCOOH). P3-TBDCOOH has a specific capacity of 681.1 mAh g−1 after 100 cycles at 50 mA g−1 and a capacity of 340.8 mAh g−1 after 1000 cycles at 1000 mA g−1. According to density functional theory calculations, P3-TBDCOOH and P3-TBCOOH with a benzene ring between the thiophene ring and the carboxyl group have higher conductivity than P3-TCOOH without a benzene ring, and P3-TBDCOOH shows stronger conductivity than P3-TBCOOH and P3-TCOOH. The results imply that the pendant isophthalic acid can enhance the electrochemical activity of polythiophene, increasing the reversible capacity.