New battery materials and designs are needed to support fast battery charging - in an automobile, for example. Composites composed of silicon and graphite are a next-generation anode material that shows promise in lithium-ion batteries and in potassium-ion batteries. However, these materials suffer from issues with both mechanical and electrochemical degradation, which is exacerbated during fast charging, leading to poor battery life and safety concerns. Electrodes with engineered architectures have shown promise in mitigating these electrochemical issues during fast charging. This project combines these material and engineering approaches to develop safer, cheaper and efficient battery technologies. Using integrated experiments and computer simulation, this work will identify fundamental mechanisms in these complex chemical and physical systems. The approaches taken in the project will ultimately be broadly applicable to other materials and future engineering efforts. This project will also provide important educational opportunities, including (1) training a PhD student; (2) adapting models to make direct contributions to classroom teaching and lectures; and (3) providing research opportunities for undergraduates at both Brown and Wellesley College. High-capacity anodes capable of fast charging are necessary for more widespread adoption of electric vehicles. Si-based composites in lithium-ion batteries offer much higher capacity than commercial graphite, and mixtures wit