Modeling and Experimental Study on the Stress Mitigation Mechanism of Nanocrystalline Silicon Anodes under Geometric Anisotropy

To address structural instabilities arising from the massive volume fluctuations in silicon anodes during charge-discharge processes, this paper established a three-dimensional electrochemical-mechanical coupled model for an idealized ellipsoidal array without a spherical assumption. Simulation results show that although the geometric anisotropy of ellipsoidal particles leads to stress concentration at high-curvature regions, the strong plasticity and superior deformability of the nanoparticles effectively control this problem. Electrochemical data show consistency with the simulated curves; the nanocrystalline silicon electrode exhibits a nominal discharge capacity of 2555 mAh·g⁻¹ and a Coulombic efficiency of 61.7% at a current density of 0.1 A·g⁻¹. After 200 cycles at a current density of 1 A·g⁻¹, the remaining capacity is 771.7 mAh·g⁻¹, with the Coulombic efficiency exceeding 99.6%. Based on these findings, a link is established between the stress mitigation mechanism—relying on low yield stress—and the improvement of battery capacity, offering theoretical insights into the optimization of transport kinetics and stability of silicon anodes through structural reorganization.