Improve Rate Capability of the Sulfur Cathode Using a Gelatin Binder

The influence of discharge rate on the discharge behaviour of the Li/S battery with the cathode using a gelatin binder (SGA cathode) is investigated by X-ray diffraction and scanning electron microscopy, with the system using poly(ethylene oxide) (PEO) binder (SPA cathode) as comparison. It is found that SGA cathode shows smaller plateau potential drop trend and less discharge curve shape change with the discharge rate increasing. Detailed characterization reveals that this is due to the dispersion ability and good adhesion of gelatin, which enable complete conversion of elemental sulfur to polysulfide in the upper plateau region and stable structure of the cathode during discharge. Developing pores in the SGA cathode (the PSGA cathode) can further improve the rate capability of the battery, since porous structure provides a larger contact surface with the electrolyte, and shorter Li(+) ion diffusion length. The PSGA cathode shows an initial capacity of 1230 mAhg(-1) -S at 100 mAg(-1) -S, and remains 733 mAhg(-1) -S at a high discharge rate of 1600 mAg(-1) -S. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3583375]