Hollow spherical carbonized polypyrrole/sulfur composite cathode materials for lithium/sulfur cells with long cycle life

Hollow carbonized polypyrrole (PPy) spheres are synthesized using poly(methyl methacrylate-ethyl acrylate-acrylic acid) latex spheres as sacrificial templates. The hollow spherical carbonized PPy/sulfur composite cathode materials are prepared by heating the mixture of hollow carbonized PPy spheres and element sulfur at 155 C for 24 h. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations show the hollow structures of the carbonized PPy spheres and the homogeneous distribution of sulfur on the carbonized PPy shells. The hollow spherical carbonized PPy/sulfur composite with 60.9 wt.% S shows high specific capacity and excellent cycling stability when used as the cathode materials in lithium/sulfur cells, whose initial specific discharge capacity reaches as high as 1320 mA h g^-1 and the reversible discharge capacity retains 758 mA h g^-1 after 400 cycles at 0.2C. The excellent electrochemical properties benefit from the hollow structures and the flexible shells of the carbonized PPy spheres.