Application of Element-Doped Carbonaceous Materials in Lithium-Sulfur Batteries

The blossoming of mobile electronic devices, plug-in electric vehicles and stationary energy storage have triggered the urgent demand for the exploration of the energy storage systems with high energy density and long cycle life. Lithium-sulfur battery is regarded as one of the most promising candidates of the next-generation rechargeable batteries, since the active substance sulfur is low cost and possesses high theoretical energy density of 2600 Wh.kg(-1). However, the practical applications of lithium-sulfur battery are hindered by a series of severe problems, which are caused by the insulative nature of sulfur and its discharge products, and the dissolution and shuttling of polysulfides. Carbonaceous materials are generally used as sulfur hosts to improve the conductivity of the cathode. Regrettably, due to the weak interaction between non-polar carbonaceous materials and polar polysulfides, the carbonaceous materials can inhibit polysulfides only by limited physical adsorption and restrictions, thus the dramatic capacity decline derived from the notorious "shuttling effect" remains insufficiently resolved. Introducing polar or chemical adsorption sites to carbonaceous materials by element doping, such as N, S, Co and B doping, can greatly enhance the adsorption capacity of carbonaceous materials to polysulfides, so as to sufficiently improve the cycling stability of the cell. Moreover, element doping may improve the electronic conductivity of carbonaceous materials by changing their electronic structure, thus effectively increasing the utilization ratio of the active materials. This article reviews the elements doping commonly applied in carbonaceous materials such as porous carbon, carbon nanotubes and graphene for lithium-sulfur batteries, wherein single-element doping, dual-element doping, and multi-element doping are introduced separately. The effects of different doping elements on performance of carbonaceous materials are analyzed. And the development direction of element-doped carbonaceous materials in lithium-sulfur batteries are prospected.