Rational design of fast-charging, composite electrodes with next-generation materials and complex architecture

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 with graphite and/or oxidized Si (SiOx) can help mitigate mechanical challenges from silicon’s enormous volume expansion during lithiation (>300%). More novel potassium ion batteries with graphite anodes show promise in competing with lithium chemistries but share electrochemical and mechanical concerns (~60% volume expansion). Additionally, architectured electrodes with channels and graded compositions can increase rate capability through improved charge/mass transport. The combination of silicon-based compositions and graphite with complex electrode architectures vastly expands the design space for new electrodes that can enable fast charging. This project is designed to enable the efficient creation of new electrodes with fast-charging capabilities in this space, by employing both experiments (including simultaneous operando visualization/electrochemical deformation measurements) and advanced modeling approaches. Specifically, in-situ (real-time) and ex-situ (postmortem) experiments will be used to track time-dependent and localized intercalation, plating, voltage, and mechanical deformation. Results will then inform theoretical and computational modeling that captures electrochemical/mechanical mechanisms of reaction inhomogeneity, plating onset, and mechanical failure with true predictive power. The combined research efforts will enable transformative impact through large improvements in battery fast-charging capability and energy density. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.