Enhancing Rate Capability in High‐Areal‐Capacity Na‐NiCl 2 Batteries Using Graphene‐Anchoring NiFe Nanoparticles as Cathode

Abstract Planar high‐temperature sodium‐nickel chloride (Na‐NiCl 2 ) batteries represent a promising energy storage technology. However, achieving high areal capacity at large current density remains challenging for Na‐NiCl 2 batteries. In this study, nickel‐iron nanoparticles anchored on reduced graphene oxide (NiFe@RGO) is synthesized and serves as active metal electrode of Na‐NiCl 2 batteries. The superior conductivity of RGO reduces charge transfer resistance, while the incorporation of active Fe minimizes polarization, thereby enhancing rate performance. As a result, the NiFe@RGO electrode (≈10 wt.% Fe) presents an areal capacity of ≈6.7 mAh cm −2 at 14.67 mA cm −2 and can run stably over 200 cycles at 11 mA cm −2 with capacity retention of 98.4%. High‐areal‐loading (150 mg cm −2 ) cathode demonstrates a capacity of 18.7 mAh cm −2 at 19.25 mA cm −2 , while maintaining extra run of 450 and 500 cycles at 11 and 16.5 mA cm −2 , respectively. In situ electrochemical impedance spectroscopy (EIS) coupled with direct current internal resistance (DCIR) analysis reveals that NiFe@RGO electrode maintains low interfacial impedance and interior resistance during the charge–discharge, correlating with its outstanding rate capability. This work provides guidance for the design of Na‐NiCl 2 batteries with high areal capacity and high‐rate performance.