Size-Dependent Electrochemical Performance Mediated by Stress-Induced Cracking in Zn₂SnO₄ Electrodes

Correlating the microscopic structural characteristics with the macroscopic electrochemical performance in electrode materials is critical for developing excellent-performance lithium-ion batteries, which however remains largely unexplored. Here, we show that the Zn₂SnO₄ (ZTO) nanowires (NWs) with smaller diameters (d < 5 nm) exhibit slower capacity fade rate and better cycling stability, as compared with the NWs with larger diameters ranging from tens to hundreds of nanometers. By applying in situ transmission electron microscopy (TEM), we discover a strong correlation of cracking behavior with the NW diameter. Upon the first lithiation, there exists a critical diameter of ∼80 nm, below which the NWs neither crack nor fracture, and above which the cracks could easily nucleate and propagate along the specific planes, resulting in the deteriorated cycling stability in larger sized electrodes. Further theoretical calculations based on the finite element model and the climbing image nudged elastic band method faithfully predict the size-dependent cracking behaviors, which may result from the synergistic effect of axial stress evolution as well as preferential Li-ion migration directions during the first lithiation. This work provides a real-time tracking of the tempo-spatial structural evolution of a single ZTO NW, which facilitates a fundamental understanding of how the sample size affects the electrochemical behavior and thus offers a reference for future battery design and application strategy.