Silicon-based anodes are considered ideal candidate materials for next generation lithium-ion batteries but suffer from poor electrical conductivity, large volume expansion and unstable SEI. The above issues can be effectively alleviated by adding carbon nanotubes (CNTs). However, the electrochemical performances vary significantly depending on the type of CNTs added, and the intrinsic mechanism remains unknown. Herein, we propose a non-destructive method to monitor the microscopic contact state and strain in silicon-based anodes based on in situ Raman spectroscopy. Then, we revealed that the large volume expansion of Si-based anodes leads to the acupuncture effect of short CNTs, with the compressive stress on the CNTs and the Li-ion (Li+) diffusion energy barriers in the SEI exhibiting a linear correlation. Both the SEI and carbon-coating are penetrated by short, thick CNTs with gigapascal (GPa)-scale compressive stress, thereby accelerating electrolyte decomposition and leading to a LiF-rich SEI and an increased Li+ diffusion barrier. Thus, long, slender CNTs are ideal for Si-based anodes. This work reveals the structure-property relationships among compressive stress, SEI components and Li+ diffusion energy barriers, providing a novel perspective on the development of high-performance electrodes