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• Polypyrrole coating is utilized for polysulfides immobilization. • Lithium sulfide is wrapped inside cathode from exposure. • Activation barrier and polysulfides shuttle are greatly suppressed. • Electrochemical performances of as-prepared cells are promoted. The significantly-high theoretical energy density and eco-sustainability of lithium sulfur batteries (LSBs) arouses a rapid surge of interest in recent years. However, some key issues of cathode, for instance, the polysulfides confinement, low ion/electrons transfer and etc., hinder the practical utilization of LSBs. Herein, such issues could be carefully handled by using the conductive polypyrrole as polysulfides wrapper. The polypyrrole with pyrrole rings can efficiently confine polysulfides inside cathode for redox. Meanwhile, the conductive polypyrrole with delocalized π-electron cloud can facilitate electrons transfer. Besides, the addition of carbon nanotube (CNT) and oxidized graphene (GO) can enhance the conductivity of cathode material. As a result, the Li 2 S/CNT/GO/PPy cathode delivers a cycling capacity of 525 mAh g−1 with a low-capacity decay rate of 0.065 % cycle−1 after 400 cycles. Therefore, the lithium-sulfur battery with Li 2 S-based and PPy-wrapped cathode could reasonably be counted as a potential alternative of long-cycling Li-ion cells. [Display omitted] [ABSTRACT FROM AUTHOR]

The high theoretical energy density, high environmental adaptability and safety of lithium sulfide (Li 2 S)-oriented cathodes attract enough attention among lithium-sulfur batteries (LSBs). In this work, the lithium sulfide (Li 2 S)-oriented composite is fabricated via an in-situ carbothermic reduction method, in which lithium sulfate is reduced by CMK3 at an optimized temperature and subsequently the as-prepared Li 2 S is protected via the conformal carbon layer by carbonization of phenol-formaldehyde resin (PF). With the aid of the porous carbon structure of CMK3 and protection of PF-derived conformal carbon layer, the dispersity of Li 2 S and conductivity of cathode are availably enhanced. It has been found that the Li 2 S@CMK3-C prepared at optimum carbothermic reduction temperature of 835 °C has excellent electrochemical performance. The lithium-sulfur battery using Li 2 S@CMK3-C as cathode and metal Li as anode can deliver a high initial discharge capacity of 979 mAh g−1 at 0.1 C, the capacity retention after running at various current density is 94%, and the discharge specific capacity is still 530 mAh g−1 at 2 C after 450 cycles. Therefore, the preparation of CMK3-supported Li 2 S-based cathode material provides a new approach for the development and industrialization of new high-performance Li–S battery. Image 1 • An in-situ carbothermic reduction method is employed. • Lithium sulfide is in-situ formed inside cathode matrix as sulfur source. • The shuttle of polysulfides and activation energy barrier is suppressed. • The as-fabricated batteries deliver elevated electrochemical performance. [ABSTRACT FROM AUTHOR]