Molecular Design Strategy toward Multielectron-Based Polyphenylaniline Organic Cathode and Its Electrochemical Performance

Abstract

The growing demands for electronic devices and electric vehicles require the exploration of more efficient and high-power battery systems, in which the organic cathode materials are becoming a research hot issue in energy storage batteries. In the work, a polytriphenylamine derivative of polyphenylaniline (P(PhAn)) with a polyaniline-like molecular backbone structure was prepared by Buchwald-Hartwig C–N coupling reaction, and its electrochemical performances were evaluated in detail as the lithium organic cathode material. P(PhAn) as cathode displayed the multielectron redox characteristic, in which two pairs of redox characteristic peaks occurred in the measured voltage range. Density functional theory (DFT) calculation and simulations further proved that the formed push–pull electron effect and the conjugated polyaniline-like skeleton change the redox potentials and electron transfer of the cathode material. The electrode material also exhibited stable cycling performances and superior rate performances. It has a decent initial discharge specific capacity of 133 mAh·g^–1, and after the 100 cycles, it kept at 111.2 mAh·g^–1, remaining the 86% of capacity retention compared to the second cycle. Under the current densities of 20, 50, 100, 200, and 500 mA·g^–1, it displayed the discharge specific capacities of 124, 122.1, 119.5, 115.3, and 112.4 mAh·g^–1, respectively, and a 90.6% of capacity was even remained at the rate of 500 mA·g^–1. Furthermore, it was proved that the energy storage process for P(PhAn) was mainly controlled by a capacitive-diffusion hybrid kinetics process.