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-1 at 0.05 A g-1 and a long lifespan of over 60 000 cycles. In the same pi-conjugated skeleton, DBPTO (containing four C00000000000000000000000000000000111111110000000011111111000000000000000000000000O and two CN groups) shows a narrower energy gap than TAPQ (containing CO and four CN groups), which leads to the superior rate and cycling performance of DBPTO. The mechanism of charge storage of DBPTO also revealed that H+ and Zn2+ coordinated with the CO and CN sites by ex situ 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. Tuning the number of CO and CN groups in the same pi-conjugated skeleton toward high rate and long lifespan cathodes in aqueous zinc-ion batteries.