Sulfur-rich polymeric materials with semi-interpenetrating network structure as a novel lithium-sulfur cathode

Novel polymeric materials with a very high content of sulfur were successfully synthesized via a facile copolymerization of elemental sulfur with 1,3-diethynylbenzene (DEB). For the as-prepared sulfur-rich polymeric materials (C-S copolymer), diynes or polydiynes are chemically cross-linked with a large amount of polymeric sulfur to form a cage-like semi-interpenetrating network (semi-IPN) structure. Due to the strong chemical interaction of sulfur with the carbon framework and the unique cage-like structure in C-S copolymers, the dissolution and diffusion of polysulfides out of the cathode is effectively suppressed through chemical and physical means. As a result, the sulfur-rich C-S polymeric materials with semi-IPN structure exhibit excellent cycling stability and high coulombic efficiency. The initial discharge capacity is 1143 mA h g-1at a 0.1 C rate. The capacity still remains at 70% even after about 500 cycles at a high current density of 1 C. In addition, a high coulombic efficiency of over 99% is obtained during the entire range of cycling.