Donor–Acceptor-Based Conjugated Polymeric Active Material with Enhanced Pseudocapacitive Contribution for Ultrafast Charging of Lithium-Ion Batteries
Saibrata Punyasloka, Koichi Higashimine, Noriyoshi Matsumi
Abstract
In the current LIBs, the capacity and fast-charging applications are limited by the available active materials. In this regard, organic conjugated polymers, due to their tunability in structure and high conductivity, have gained much focus in the current research community. Further, the introduction of a donor–acceptor structure into the framework helps in achieving a very narrow band gap between the highest occupied molecular orbital and lowest unoccupied molecular orbital levels and enhances the electronic interaction, thereby increasing the power density. Hence, such organic polymers are expected to aid in fast-charging applications and help render a very high capacity, making them an attractive choice as an anode material. Therefore, in this work, a donor–acceptor-based imine-linked conjugated network-type porous polymer, POL 202, was designed via a simple polycondensation reaction of 2,2′-bithiophene-5,5′-dicarboxaldehyde and 1,2,4,5-benzene tetraamine tetrahydrochloride. The charge storage mechanism was found to be predominantly by a pseudocapacitive process, which becomes a crucial factor when we consider fast-charging applications in batteries. The polymer delivered a very high capacity of 850 mAh/g at a current density of 100 mA/g with a capacity retention of 100%. Further, a reversible capacity of 205 mAh/g at the current rate of 5000 mA/g and a capacity of 270 mAh/g at the current rate of 2000 mA/g were observed. A striking feature of this polymer was the total time for charging, which was 8 min at a current rate of 2000 mAh/g and 2.5 min at a current rate of 5000 mA/g, making it a very attractive avenue as a next-generation electrode material.