Sulfurized poly(o-phenylenediamine) as a novel high-performance solid-phase conversion sulfur cathode

The combination of sulfurized polymer cathode and ester-type electrolyte can realize the solid-phase conversion of sulfur cathode, which is a promising solution of the dissolution issue of Li–S batteries. In this regard, sulfurized polyacrylonitrile (SPAN) is the most famous material and few attempts have been made to challenge it in the past two decades. Herein, we report sulfurized poly(o-phenylenediamine) (SPoPDA) as its supplement or alternative for rechargeable lithium batteries. Compared with SPAN, SPoPDA shows higher ability to covalently bond with sulfur (from ∼50 to ∼60 wt%), similar reversible capacity (∼600 mAh g−1), better cycling stability (with only 2% loss of charge capacity during 100 cycles), and faster reaction kinetics. The molecular structures and electrochemical reaction mechanisms of them have been quantitatively analyzed, and the electrode structure variation of SPoPDA during discharge–charge process has been thoroughly investigated. This work provides not only a novel sulfurized polymer cathode material with low cost, easy synthesis, and high electrochemical performance, but also clearer mechanism understanding of solid-phase conversion sulfur cathode, which are of significant importance for the development of Li–S batteries towards practical application.