Co4N embedded nitrogen doped carbon with 2D/3D hybrid structure as sulfur host for room-temperature sodium-sulfur batteries

Abstract

Room temperature sodium-sulfur (RT Na-S) batteries demonstrate a high theoretical energy density, but their practical application is limited by the sodium polysulfides (NaPSs) shuttling and slow redox kinetics. Herein, we report the design of the dimensional hybrid structure of 2D ZIF-67 nanosheets and 3D ZIF-67 polyhedron on the surface of carbon fiber by a pseudomorphic replication approach. After pyrolysis in ammonia, a hybrid structure composed of 2D N-doped carbon nanosheets and 3D N-doped carbon nano-polyhedrons embedded with Co4N nanoparticles (denoted as 2D/3D Co4N-NC@CC) is designed as a sulfur host for RT Na-S battery. The complex structure of 2D/3D composite guarantees abundant adsorption and catalytic sites, accelerating electrons/mass transport abilities compared with single 2D or 3D structure, in which Co4N can effectively catalyze the conversion of NaPSs and inhibit “shuttling effect”. Consequently, the RT Na-S cell with 2D/3D Co4N-NC@CC cathode exhibits extra-high discharge capacity of 466 mAh g−1 at 3.0 C and an outstanding long-term cycling stability (592 mAh g−1 at 1.0 C after 1000 cycles). The hybrid 2D/3D Co4N-NC@CC with excellent electrochemical performance represents a potential candidate for developing advanced RT Na-S batteries and other energy storage systems.