2, POSTECH, Pohang, Kyungbuk, Korea (the Republic of)
Lithium ion batteries have penetrated into our daily lives ranging from mobile phones to electric vehicles. This prompted considerable efforts toward the development of high-energy density lithium batteries, with a focus on designing new electrode active materials. In this context, elemental sulfur has been regarded as one of the promising candidates for next generation cathode materials owing to their high theoretical specific capacity (1672 mAh/g) and high energy density (2567 Wh/kg）based on 2-electron redox chemistry. In addition, low-cost, low-toxicity, and natural abundance of sulfur are another advantages. In spite of aforementioned strengths, sulfur cathodes suffer from critical limitations to be used in practical applications, such as volumetric changes during cycling, irreversible relocation of charge/discharge products, intrinsic insulating nature of sulfur, and dissolution of lithium polysulfide intermediates into the polar electrolyte. In the present study, we report the development of new sulfur cathodes based on inverse-vulcanized polymers. A new strategy is the use of functional linkers for the vulcanization process to enhance the electrochemical properties upon modulating electronic structures of the resultant polymers. Inverse-vulcanized polymers with 2,3,5,6-Tetra(allyloxy)benzoquinone linker showed amorphous morphology with improved redox activity, low band gap, and enhanced electric conductivity. By taking advantages of these benefits, the lithium-sulfur batteries can deliver high reversible discharge capacity of 1100 mAh/g with good capacity retention and decent rate capability up to 10 C.