Tuning the number of redox groups in the cathode toward high rate and long lifespan zinc-ion batteries

We synthesized a small molecule, DBPTO, and used it as a cathode material in aqueous zinc-ion batteries. DBPTO presented a high reversible capacity of 382 mA h g at 0.05 A g and a long lifespan of over 60 000 cycles. In the same π-conjugated skeleton, DBPTO (containing four CO and two CN groups) shows a narrower energy gap than TAPQ (containing CO and four CN groups), which leads to the superior rate and cycling performance of DBPTO. The mechanism of charge storage of DBPTO also revealed that H and Zn coordinated with the CO and CN sites by structural characterization and DFT calculations. Our results provide new insights into the design of organic cathodes with a high rate capability and long lifespan. Further efforts will focus on a deeper understanding of the charge storage mechanism.