Revealing the Hazard of Mild Electrical Abuse on the Safety Characteristics of NaNi _1/3 Fe _1/3 Mn _1/3 O ₂ Cathode Sodium‐Ion Battery

Abstract This study investigates the degradation of safety characteristics in commercial NaNi _1/3 Fe _1/3 Mn _1/3 O ₂ (NFM) sodium‐ion batteries (SIBs) under mild electrical abuse, focusing on the impact of a single electrical abuse event on capacity, impedance characteristics, and thermal stability, and reveals the degradation pattern of safety characteristics under long‐term electrical abuse cycles. The research finds that while a single mild electrical abuse event has a limited effect on battery capacity, the internal electrochemical properties of the battery still change. Mild overcharge reduces the thermal stability of the anode material, and the increased sodium plating on the anode surface also significantly affects the overall safety characteristics of the battery. In contrast, the harm caused by over‐discharge is less severe. After long‐term electrical abuse cycles, the battery experiences significant capacity degradation, and prolonged overcharge cycles cause further sodium plating, severely affecting battery safety. Overall, the impact of long‐term mild overcharge on safety characteristics is more pronounced. This study not only clarifies the degradation mechanism of sodium‐ion battery safety characteristics under electrical abuse but also provides theoretical support for the optimization design and safety evaluation of sodium‐ion batteries.