Easily accessible and tunable porous organic polymer anode from azo coupling for sustainable lithium-organic batteries

Abstract

Porous organic polymers (POPs) are promising sustainable electrodes for energy storage applications. Although a handful of POPs with facile synthesis and structural tunability have been developed, they are limited to specific classes of precursors and transition metal-based catalysts. In this work, three tunable porous organic polymers were successfully synthesized and characterized using the simple azo coupling reaction of readily available precursors, phloroglucinol, and diarylamines. The α-hydrazoketone was unambiguously assigned based on X-ray photoelectron spectroscopy (XPS). The POPs with a redox-active functional group deliver impressive reversible capacity. The effects of POP precursors, surface area, and pore size on the electrochemical properties and battery performances were systematically investigated. According to the results, a high content of α-hydrazoketone and a large surface area are critical factors in designing efficient organic electrodes for high-performance energy storage. Interestingly, POP-1 derived from o-tolidine precursor exhibited a high specific capacity with greater rate capability as well as superior cycling stability over 1,000 cycles due to the importance of the magic methyl effect, optimal surface area (294 m2 g−1), and porosity. Furthermore, ex-situ FT-IR, Raman, and XPS studies also implicate the reversible redox reaction of α-hydrazoketone. Cyclic voltammetry and electrochemical impedance spectroscopy revealed kinetic behavior influencing the lithium-ion storage mechanism. This research provides empirical evidence that this tunable family of porous organic polymers is the first to exhibit promising organic electrode characteristics for the next generation of sustainable lithium-organic batteries.