Introducing symmetry breaking to regulate the band structure for achieving superior rate performance in iron-based phosphate cathode for sodium-ion batteries

Due to the abundant availability and stable cost of sodium, sodium ion batteries are considered a crucial component in energy storage systems, with increasing demands placed on their rate performance and long cycle stability. In sodium ion battery polyanion cathode materials, addressing the issue of poor electron conductivity to improve rate performance has become a focal point of research. This study investigates the mechanisms by which alkaline earth metals regulate the band structure to achieve excellent rate performance. Advanced characterization methods and theoretical calculations provide a thorough explanation of the effects of Ca²⁺ substitution, which introduces symmetry breaking into the crystal field and consequently affects the band structure and electrochemical performance. Our results confirm the effectiveness of the trace alkaline earth metal substitution strategy in improving the electron conductivity, leading to improved electrochemical performance.