Abstract: In the context of the energy transition, the development of strategic emerging industries has led to a surge in demand for critical metals, exacerbating the supply-demand imbalance. Technological innovation is a key factor influencing the sustainability of critical metal supply. However, previous studies have largely overlooked the temporal diffusion effects, differences, and interconnections of various types of technological innovations. Therefore, clarifying the technological drivers and diffusion effects of critical metals is of great significance for ensuring China’s critical metal resource security. This paper focuses on lithium, a critical metal, and employs methods such as ARIMAX to explore the impact of technological innovation and other factors on critical metal supply. The findings indicate that the scale of the technological innovation network continues to expand, and its cohesion and stability are strengthening. Technological innovation exhibits a significant positive diffusion effect on mineral supply with a one-year lag, while price and reserves also influence supply with a one-year diffusion effect. However, economic factors do not exhibit a diffusion effect on mineral supply. Further analysis reveals that among functional technological innovations, efficiency-enhancing innovations have the greatest impact, while safety-enhancing innovations have the least. Among process-oriented technological innovations, extraction-related innovations exert the greatest influence, while smelting-related innovations have the least impact. In terms of the diffusion effect of technological innovation, different functional and process-stage innovations demonstrate a diffusion effect ranging from one to three years. Based on these findings, this study proposes three strategies to enhance the security and technological innovation capacity of critical metal supply: encouraging continuous collaboration and innovation along the industrial chain, leveraging core technologies as pivotal links, and ensuring economic stability to inject fresh momentum into the mineral resource industry. These recommendations aim to provide scientific evidence and policy support for ensuring the security of national critical metal supply.