Regulation of the pore structure of carbon nanosheets based electrocatalyst for efficient polysulfides phase conversions

Abstract

The practical applications of lithium-sulfur (Li-S) batteries are hampered by the sluggish redox kinetics and polysulfides shuttle in the cyclic process, which leads to a series of problems including the loss of active materials and poor cycling efficiency. In this paper, the pore structures of carbon nanosheets based electrocatalysts were precisely controlled by regulating the content of water-soluble KCl template. The relationship between pore structures and Li-S electrochemical behavior was studied, which demonstrates a key influence of pore structure in polysulfides phase conversions. In the liquid-sloid redox reaction of polysulfides, the micropores and small mesopores (d < 20 nm) exhibited little impact, while the mesopores (d > 20 nm) and macropores played a decisive role. As a typical exhibition, the nickel-embedded carbon nanosheets (Ni-CNS) with a high content of large mesopores and macropores can aid Li-S batteries in exhibiting stable cycling performance (760.1 mAh g−1 at 1 C after 300 cycles) and superior rate capacity (847.8 mAh g−1 at 2 C). Furthermore, even with high sulfur loading (8 mg cm−2) and low electrolyte (E/S is around 6 µL mg−1), the high area capacity of 7.7 mAh cm−2 at 0.05 C could be achieved. This work can provide a guideline for the design of the pore structure of carbon-based electrocatalysts toward high-efficiency sulfur species redox reactions, and afford a general, controllable, and simple approach to constructing high performance Li-S batteries.