Utilizing 2D layered structure Cu-g-C3N4 electrocatalyst for optimizing polysulfide conversion in wide-temperature Li-S batteries

Lithium-sulfur batteries (LSBs) as "post-lithium-ion battery" have gained a high level of visibility due to high energy density and specific capacity. Nevertheless, the commercial production of LSBs is hampered by the the most notorious trouble for shuttling effects of lithium polysulfides (LiPSs). To settle the inherent issues, copper-doped graphitic carbon nitride (Cu-g-C3N4) catalysts with two-dimensional lamellar structures are synthesized using a template method as coating materials for LSBs separators. The substrate material g-C3N4 has a high nitrogen content, which can augment the charge density and significantly enhance the affinity of the materials for LiPSs. Doping of copper atoms in the layered structure of g-C3N4 significantly increases the electrocatalytic activity by creating additional active sites and expediting the redox kinetics of LiPSs for simultaneous S reduction as well as Li2S oxidation. With in-situ UV–vis and theoretical calculations, the efficient activation of bidirectional reaction substantially enhances the rate of solid–liquid-solid reaction, especially solid–solid (Li2S2-Li2S) conversion. As a consequence, the cell with Cu-g-C3N4 shows a satisfied initial discharge capacity of 1469.36 mAh/g at 0.1C. In addition, a high areal capacity of 6.04 mAh/cm2 is achieved under a S loading of 5.10 mg/cm2. Most importantly, the cell with Cu-g-C3N4 maintains stable cycling performance over the scope of a broad temperature (0 °C and 60 °C). This work demonstrates that Cu-g-C3N4 catalysts can be realized for the design of low/high-temperature-resistant LSBs.