Uniform zeolitic imidazolate framework coating via in situ recoordination for efficient polysulfide trapping

The “shuttle effect” in lithium sulfur battery system is the most prominent challenge hampering its further development and application in the energy storage industry. Metal-organic framework (MOF) derived carbon materials are considered to be efficient sulfur hosts to confine the polysulfides because of the unique porous structure and the heteroatom doping. However, a strong acid wash step is usually needed to remove the metal or metal oxide residual after pyrolysis, which will produce a large amount of acidic waste solution and increase the complexity of the synthetic process. Herein, instead of being removed, the uniformly dispersed ZnO nanoparticles in the pyrolytic polyhedra from zeolitic imidazolate framework-8 (ZIF-8) is directly used as the metal source to prepare a new ZIF-8 coating layer. This novel structure possesses not only the unique inner porous structure and high conductivity of pyrolytic carbon, but also the extra protection from ZIF-8 layer with both physical confinement and chemisorption to polysulfides. The resulting cathode displays an initial capacity of 1410 mAh g−1 at 0.2 C, and desirable cycling stability and rate capability are also obtained.