The chemical composition and mechanical properties change of coating materials, interfaces, and Si itself during lithiation and delithiation process imposed a grand challenge to design coating/Si nanostructure as an integrated electrode system. In our work, reactive force field (ReaxFF) parameters for Li-Si-Al-O-F were developed along with a new algorithm to simulate lithiation and delithation processes with different rates. With the reactive dynamics simulations, we were able to simultaneously track and correlate the lithiation-delithiation rate, compositional change, mechanical property evolution, stress distributions, and fracture. Interesting insights were obtained from these studies. For example, it was found that the lithiation rate during the initial mixing stage increases exponentially with vacancy concentrations in Si; and it was discovered the self-accelerating Li diffusion in Al₂O₃ coating forms a well-defined Li concentration gradient, leading to an elastic modulus gradient, which effectively avoids local stress concentration and mitigates crack propagation.  A new mechanics model based on these varying properties was developed to determine how to stabilize the coating with a critical size ratio.