Towards high energy density Li-S batteries with high sulfur loading: From key issues to advanced strategies

High energy and low-cost lithium sulfur battery (LSB) has been vigorously revisited in recent years due to urgent need of electric vehicles (EV), portable devices and grid storage. For EV applications, the areal capacity of LSBs needs reach 5 mAh cm(-2) to compete with the state-of-the-art LIBs. However, the practical application of LSB has been hindered by the gap in scientific knowledge between the fundamental research and application requirement such as high sulfur loading (over 5 mg cm(-2)). Moreover, notorious "shuffle effect", sluggish redox kinetics and non-ignorable safety issues impede its rapid development, which will become more serious with high sulfur loading. Thus numerous researchers have focused on areal capacity and safety at high sulfur loading. In this review, the fundamental studies and current development strategies for high sulfur loading LSBs are reviewed mainly including LiPSs anchoring, electrocatalytic effect and overall security strategy. For LiPSs anchoring strategy, the function mechanism includes physical adsorption/barrier, chemical anchor and electrostatic interaction. For electrocatalytic strategy, 0D nanoparticles/nanospheres, 1D nanofibers/nanowires, 2D nanosheets/ nanoflakes and 3D catalytic materials are summarized. For the safety issues, liquid/solid electrolytes modification, high-performance separators/interlayers, artificial SEI layers and nanostructured Li anodes of high sulfur loading LSBs are also described. Finally, we conclude with an outlook section to provide some insights on the future prospects of high energy density (over 500 Wh kg(-1)) for LSBs. This discussion and proposed strategies will offer more avenues to the practical application LSBs with high energy density in the future.