Influence of defects on enhancing lithium diffusivity in crystalline silicon anodes for fast charging lithium-ion batteries

The energy storage sector requires high capacity, long cycling life batteries. Silicon (Si) arises as a pivotal anode material for next-generation lithium-ion batteries owing to its exceptional capacity. However, challenges arise from lithium interactions, causing volumetric expansion and structural concerns like cracking. Si anodes also exhibit diverse phenomena during lithiation, influenced by crystal orientations. A thorough comprehension of the (de)lithiation process is essential to address challenges, despite existing gaps in knowledge, with strategic design and complementary materials, offering potential solutions by enhancing ion mobility and minimizing diffusion barriers. Here we have developed and applied first-principles simulations to offer fundamental insights into atomic interactions, providing a realistic atomistic representation of lithiation processes. Our simulations systematically incorporate Li+ into Si and Si- nitrogen vacancies (NV) orientations, and evaluation between Si and Si-NV (110) indicates a more favorable behavior in ionic diffusion for Si-NV(110), with a range of 2.55 × 10−3 to 1.64 × 10−2 (cm2/s) and a 15 % decrease in volume expansion. Our results explain the ternary Si–Li–N electrode materials and the identification of optimal site disorders to maximize the rate of Li+ diffusion in crystalline Si anodes.