Rate‐Dependent Failure Behavior Regulation of LiFePO₄ Cathode via Functional Interface Engineering

Abstract LiFePO₄ is extensively used as a cathode material in lithium‐ion batteries because of its high safety profile, affordability, and extended cycle life. Nevertheless, its inherently low lithium‐ion transport kinetics and restricted electronic conductivity considerably limit its rate performance. Furthermore, the failure mechanisms specific to various cycling rates are not well examined. This study presents a functional interface layer designed to regulate the rate‐dependent failure behavior of LiFePO₄. At elevated charge/discharge rates, this layer facilitates lithium‐ion mobility, decreases internal polarization, alleviates mechanical stress, and reduces structural degradation. At lower cycling rates, it contributes to the formation of a stable cathode‐electrolyte interphase (CEI), effectively suppressing side reactions and minimizing active lithium loss. Consequently, the modified LiFePO₄ demonstrates enhanced cycling stability and capacity retention, with capacity retention after 400 cycles at 2C rate increasing from 76.5% to 98.6% and at 5C increasing from 40.2% to 90.0%. Through combinations of experimental data and theoretical analysis, this study elucidates key mechanisms underlying rate‐specific failure regulation, providing valuable insights into the relationship between ion transport dynamics and structural stability. This approach represents an effective strategy for supporting its potential use in advanced energy storage systems that require both rapid charging and prolonged cycling stability.