(Co, Ni)-NC/CNT Composite as a Cathode for Li-S Batteries

So far, severe capacity decay induced by the polysulfide shuttle effect still remains a great obstacle to the commercialization of lithium-sulfur batteries (LSBs). Herein, Ni-doped ZIF67 (ZIF67/Ni) was prepared by the coprecipitation method, and then (Co, Ni)-NC/CNT composites in which in situ formed Co-Ni nanoparticles and CNTs are embedded in the 3D N-doped nanoporous carbon network structure were successfully obtained by a two-step carbonization heat treatment, without shrinkage and collapse of the skeleton. The synergistic catalysis of Co-Ni bimetal significantly promotes redox kinetics, renders strong chemisorption toward polysulfides, and reduces the CVD growth temperature of CNTs (600 °C). Furthermore, the 3D conductive network of the N-doped C skeleton embedded with CNTs and Co-Ni nanoparticles ensures fast electron/ion transportation and structural stability of the skeleton. As the cathode host of LSBs (Co, Ni)-NC/CNT composites exhibit excellent rate performance (1352-590.6 mA h g^-1 at 0.5-10 A g^-1) and superior cycling stability (reversible capacity of 744 and 544 mA h g^-1, with decay rates of 0.031% and 0.029% per cycle at 1 and 5A g^-1 for 1000 cycles, respectively). The simple and scalable construction strategy of MOF derivatives shows an important application prospect in electrochemical energy storage, catalysis, electromagnetic shielding/microwave absorption, etc.