A Sulfur Heterocyclic Quinone Cathode and a Multifunctional Binder for a High-Performance Rechargeable Lithium-Ion Battery

We report a rational design of a sulfur heterocyclic quinone (dibenzo[b,i] thianthrene-5,7,12,14-tetraone=DTT) used as a cathode (uptake of four lithium ions to form Li4DTT) and a conductive polymer [poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)=PEDOT:PSS) used as a binder for a high-performance rechargeable lithium-ion battery. Because of the reduced energy level of the lowest unoccupied molecular orbital (LUMO) caused by the introduced S atoms, the initial Li-ion intercalation potential of DTT is 2.89 V, which is 0.3 V higher than that of its carbon analog. Meanwhile, there is a noncovalent interaction between DTT and PEDOT:PSS, which remarkably suppressed the dissolution and enhanced the conductivity of DTT, thus leading to the great improvement of the electrochemical performance. The DTT cathode with the PEDOT:PSS binder displays a long-term cycling stability (292 mAhg(-1) for the first cycle, 266 mAhg(-1) after 200 cycles at 0.1 C) and a high rate capability (220 mAhg(-1) at 1 C). This design strategy based on a noncovalent interaction is very effective for the application of small organic molecules as the cathode of rechargeable lithium-ion batteries.