Rational structure design of metal-based cathode for high-rate and long-cycling sodium nickel chloride batteries

High-temperature sodium-nickel chloride (Na-NiCl2) batteries represented as an advanced energy storage technology show impressive advantages including abundant raw materials, high safety and long-cycling life. Nevertheless, their large-scale application is still hindered by the poor stability and rate capability of the cathode. In this work, we designed a three-dimensional cross-linked network composed of NiFe alloy nanowires via a magnetic-field assisted method. The as-prepared NiFe nanowires (NiFe NWs) are mixed with NaCl as the composite cathode of sodium-metal chloride batteries, delivering exceptionally enhanced rate performance (150.3 mAh/g@0.88 C) and superior cycling stability (84.3% capacity retention after 500 cycles). The properties are superior to those of the cathode based on the pristine Ni nanowires or the NiFe nanoparticles, which is ascribe to the existence of active Fe metal and the continuous conductive network, as confirmed by kinetics analysis. After experiencing a long-term cycling at large current density (∼0.88 C), no obvious coarsening of NiFe NWs and NaCl particles occurs. Moreover, the large-size Na-NiCl2 battery with capacity of 229 mAh reaches a practical energy density of 265.65 Wh kg−1 (∼0.3 C) with energy efficiency of 88.6%. Therefore, our work provides a guide for rational design of cathode structure, thereby improving rate and cycling performance of Na-NiCl2 batteries.