Highly dispersed CuO nanoparticles embedded within porous nitrogen doped carbon as effective electrocatalyst for lithium sulfur batteries

Abstract

Lithium sulfur batteries face several challenges, including significant volumetric expansion during cycling, slow kinetics of sulfur redox reactions, and the shuttle effect of solubility lithium polysulfides. Polar metal oxides, due to their hydrophilic surface, can effectively adsorb polysulfides, facilitating their confinement and reducing their mobility, which helps to mitigate the shuttle effect. In this study, CuO nanoparticles embedded within porous nitrogen-doped porous carbon (CuO@NC) composite with a high specific surface area of 865.68 m² g^-1 are successfully synthesized without use of additional template. The CuO@NC composite enables the synergy between the physical adsorption provided by the porous carbon framework and the chemical adsorption-catalysis of CuO, thereby enhancing polysulfide immobilization and improving electrochemical performance. Cells fabricated with CuO@NC modified separator show a high specific capacity of 969.8 mAh g^-1 at 0.5 C, excellent rate capability (937.9 mAh g^-1 at 1 C), and a stable capacity of 793.2 mAh g^-1 after 200 cycles with a low decay rate of 0.09 % per cycle. Furthermore, the CuO@NC modified separator maintains a discharge capacity of 725.6 mAh g^-1 at -10 °C. Even with sulfur loading up to 5.6 mg cm^-2, it can still exhibit remarkable cycling stability. This study demonstrates the design of metal oxides-decorated porous heteroatoms doped carbon materials as an effective strategy for fabricating highly functional separator that inhibit the polysulfides shuttle effect.