Unveiling the Chemomechanical Origin of Ultralong Cycling in Sb/C Composite Anodes

ABSTRACT Mechanical fatigue is a non‐negligible failure reason for most electrodes. Consequently, the development of robust electrodes that deliver both high capacity and long cycle life requires a systematic and in‐depth understanding of their mechanical behavior during operation. In this study, we design an antimony‐carbon composite featuring sub‐50 nm antimony nanoparticles uniformly embedded within a carbon matrix, which exhibits superb longevity with a capacity of 415.7 mAh g −1 after 15 000 cycles at 5 A g −1 . Its practical applicability is demonstrated in a full‐cell configuration with a LiFePO 4 cathode, delivering 79.4 mAh g −1 at 5 C with 91% capacity retention over 200 cycles. In‐situ mechanical characterizations from micro to macro levels and related chemo‐mechanical modeling jointly reveal that the carbon matrix and ultrafine Sb nanoparticles facilitate homogeneous and complete lithiation, inhibit crack formation and active material loss, and enhance the modulus of the electrode. These effects collectively improve stress reversibility and reduce residual stress accumulation across the cell. This work exhibits the role of integrated multi‐scale mechanical analysis in revealing electrode failure, and paves the way for high‐energy‐density, long‐lasting material design.