Sulfur Immobilized in Hierarchically Porous Structured Carbon as Cathodes for Lithium-Sulfur Battery with Improved Electrochemical Performance

In order to overcome the main obstacles for lithium–sulfur batteries, such as poor conductivity of sulfur, polysulfide intermediate dissolution, and large volume change generated during the cycle process, a hard-template route is developed to synthesize large-surface area carbon with abundant micropores and mesopores to immobilize sulfur species. The microstructures of the C/S hybrids are investigated using field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, nitrogen adsorption–desorption isotherms, and electrochemical impedance spectroscopy techniques. The large surface and porous structure can effectively alleviate large strain due to the lithiation/delithiation process. More importantly, the micropores can effectively confine small molecules of sulfur in the form of S2–4, avoiding loss of active S species and dissolution of high-order lithium polysulfides. The porous C/S hybrids show significantly enhanced electrochemical performance with good cycling stability, high specific capacity, and rate capability. The C/S-39 hybrid with an optimal content of 39 wt% S shows a reversible capacity of 780 mA h g−1 after 100 cycles at the current density of 100 mA g−1. Even at a current density of 5 A g−1, the reversible capacity of C/S-39 can still maintain at 420 mA h g−1 after 60 cycles. This strategy offers a new way for solving long-term reversibility obstacle and designing new cathode electrode architectures.