A Novel Aqueous Sodium‐Ion Supercabattery by Intercalation‐Dominated Bi ₂ TiO ₄ F ₂ Perovskite Electrode

This study systematically investigates the electrochemical behavior of Aurivillius‐type perovskite Bi 2 TiO 4 F 2 (BTOF) in different electrolyte systems, with a particular focus on elucidating its energy storage mechanism in a 1 m Na 2 SO 4 aqueous electrolyte, and further constructs a novel aqueous sodium‐ion supercabattery (ASSCB). The results reveal that BTOF exhibits superior electrochemical performance in 1 m Na 2 SO 4 compared to 1 m (NH 4 ) 2 SO 4 , primarily owing to the superior solvation structure of Na⁺, its lower desolvation energy barrier, and more efficient interfacial charge transfer, as determined through theoretical simulations and calculations. Through ex situ/in situ physicochemical and electrochemical techniques, it is found that the charge storage behavior in 1 m Na 2 SO 4 involves a hybrid mechanism dominated by reversible Na⁺ intercalation/deintercalation, accompanied by secondary processes including SO 4 2− interfacial adsorption/desorption and material conversion reactions. By leveraging the synergistic pseudocapacitive‐capacitive‐battery charge storage characteristics of the BTOF electrode (as anode or cathode) with activated carbon‐Na 3 V 2 (PO 4 ) 2 F 3 @C (NVPF@C‐AC) cathode or activated carbon‐NaTi 2 (PO 4 ) 3 @C (NTP@C‐AC) anode, novel ASSCB devices (BTOF//NVPF@C‐AC and NTP@C‐AC//BTOF) are constructed with comprehensive performance advantages. This work explores a new Aurivillius‐type perovskite electrode material for aqueous Na‐ion storage with deep insight into the complex charge storage mechanism and provides a novel concept for advanced aqueous energy storage systems.