Co–Ni bimetallic selenides embedded in honeycomb carbon framework as multifunctional separator interlayer to enhance the electrochemical performance of Li–S batteries

The commercialization of Li–S batteries is severely hampered by the electrically insulated nature of S and the discharge product Li2S, the shuttle effect of lithium polysulfides (LiPSs), and the slow redox kinetics between Li2S2/Li2S. Herein, a composite of Co–Ni bimetallic selenide nanoparticles embedded in honeycomb porous carbon (Co–Ni–Se@C) is prepared and used as a multifunctional interlayer on the separator to solve the above-mentioned challenges in Li–S batteries. The Co–Ni–Se@C composite with high electrical conductivity can not only accelerate Li+ and electronic transfer but also have good chemisorption and catalytic activity for LiPSs, which can maximize the utilization of sulfur active material. As expected, Li–S batteries assembled with Co–Ni–Se@C-PP separator exhibit excellent electrochemical performance, including high initial discharge capacity of 1245 mAh g−1 at 0.2 C, superior long cycling stability with a 0.066 % decay per cycle at 1.0 C, and an excellent rate capacity of 674 mAh g−1 at 5.0 C. In addition, a satisfactory capacity of 1174 mAh g−1 is achieved with a high sulfur loading of 3.7 mAh g−1 and a low E/S ratio of 10 μL mg−1. This work provides a new insight into the application of bimetallic selenides in high-performance Li–S batteries.