| 초록 |
Li-S battery is promising energy storage devices for its lower cost and higher energy density than LIB. However, Li-S battery has intrinsic problems such as poor electrical conductivity of S and shuttle effects of lithium polysulfides. By encapsulating S in a carbon host, we could expect to alleviate those issues. In this study, we prepared hollow carbon spheres (HCS) by using polymer spheres synthesized by batch emulsifier-free emulsion copolymerization of styrene with acrylic acid. Then, we coated the polymer with carbon gel. The carbon gel-coated core-shell polymers were heated to carbonize the shell of carbon gel and to pyrolyze the core polymer to generate the HCS simultaneously. Encapsulating S in HCS was followed by two different methods; conventional physical mixing of S powder and HCS followed by melt-diffusion(S/HCS-PM) or solution S impregnation followed by melt-diffusion(S/HCS-IM). We found that the S/HCS-IM showed much higher S utilization and cycling stability than the S/HCS-PM due to the better sulfur dispersion in S/HCS-IM than that in S/HCS-PM. It was also possible to further enhance the sulfur utilization by employing a carbon coated separator.
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