m‑Phenylenediamine as a Building Block for Polyimide Battery Cathode Materials

Organic compounds have recently gained significant attention as materials for the next generation of sustainable energy storage devices. Polyimides are one of the most attractive types of organic battery cathode materials, especially if they are produced from easily accessible, inexpensive reagents. However, these polymers are still at the early stage of development for rechargeable metal-ion batteries. Particularly, the scope of amine building blocks that were used for the polyimide synthesis remains scarce. In this study, we propose m-phenylenediamine as a building block for polyimide-based cathode materials. We report the electrochemical properties of polyimides obtained from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) and m- or p-phenylenediamines for lithium-, sodium-, and potassium-ion batteries; and show that the m-polyimide has several advantages over the p-isomer. It has larger capacities and superior high-rate capabilities, owing to a higher specific surface area and smaller particle size. In sodium- and potassium-based batteries, the redox potentials of the m-isomer are higher because of the spatial arrangement of adjacent imide units, which makes chelation of metal cations more energetically favorable. These results provide an impetus for designing new polyimide-based battery materials with higher energy density and fast charge–discharge kinetics.