An Organic Cathode Material S-3Q@MWCNT with Monoelectrochemical Conversion Phase for Highly Reversible Lithium Batteries

A facile strategy to synthesize organic cathode material using triquinoxaline (3Q) and elemental sulfur (S) is reported. The 3Q material is a kind of multiredox phase-transiting composite with a theoretical specific capacity of 418 mA h g(-1) and a poor cycling performance. By adding S to 3Q@multiwalled carbon nanotubes (MWCNTs) at 165 degrees C with a mass ratio of 1:4, S and 3Q are chemically matched to form an organic composite S-3Q@MWCNT. Interestingly, it is found that the as-prepared sample exhibits a single-electrochemical phase transition with a higher specific capacity of 608 mA h g(-1) at 0.1C rate. The mass ratio of 1:4 indicates that the capacity of S is equal to the capacity of 3Q, and the monoredox conversion phase suggests that S and 3Q are electrochemically matched. These results show that the chemical matching point is consistent with the electrochemical matching point. The as-prepared S-3Q@MWCNT composite presents a good cycling performance. In the absence of any additives, especially without the assistance of coated separators, the coulombic efficiency is stable at around 100% for 400 cycles. It is believed that the monophase redox process of the as-prepared S-3Q@MWCNT improves the cycling performance.