(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.