Novel melamine-based porous organic polymers: synthesis, characterizations, morphology modifications, and their applications in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have been considered to be one of the most promising energy storage devices in the next generation. However, the insulating properties of sulfur and the shuttle effect of soluble lithium polysulfides (LiPSs) seriously hinder the practical application of Li-S batteries. In this paper, a novel porous organic polymer (HUT3) was prepared based on the polycondensation between melamine and 1,4-phenylene diisocyanate. The micro morphology of HUT3 was improved by in situ growth on different mass fractions of rGO (5%, 10%, 15%), and the obtained HUT3-rGO composites were employed as sulfur carriers in Li-S batteries with promoted the sulfur loading ratio and lithium-ion mobility. Attributed to the synergistic effect of the chemisorption of polar groups and the physical constraints of HUT3 structure, HUT3-rGO/S electrodes exhibits excellent capacity and cyclability performance. For instance, HUT3-10rGO/S electrode exhibits a high initial specific capacity of 950 mAh g(-1) at 0.2 C and retains a high capacity of 707 mAh g(-1) after 500 cycles at 1 C. This work emphasizes the importance of the rational design of the chemical structure and opens up a simple way for the development of cathode materials suitable for high-performance Li-S batteries.