Collaborative Research: Mechanistic understanding of chemomechanics in phase-changing electroceramics for sodium-ion batteries

NON-TECHNICAL SUMMARY Sodium-ion chemistry provides a significant alternative to the current lithium-ion technology for rechargeable batteries with its foremost advantage of natural abundance, low cost, and much wider choices of material selection, therefore providing a critical strategy to reduce the risk of the low reserve of scarce elements in the US. However, compared to lithium reactions, sodium chemistry poses a considerable mechanical deformation to the electrodes and creates more stress and degradation that compromise battery performance. This project, supported by the Ceramics Program within the Division of Materials Research, seeks to create a fundamental understanding of battery degradation via a close integration of novel experiments, data analysis, and modeling approaches. Such knowledge is crucial to elucidating the aging mechanisms of sodium-based batteries, which synergistically contribute to the development of materials of enhanced reliability for the same applications. The multifaceted collaboration between Purdue and Virginia Tech provides unique training opportunities for developing workforce for STEM related careers, with particular relevance to meeting the demand of the energy industries, which is expected to grow significantly in the coming decades. The research also provides a platform to continue the recruitment and engagement of future scientists on convergent research skills and entrepreneurial training. TECHNICAL SUMMARY The project aims to achieve a holistic understanding of chemomechanics in phase-changing electroceramic electrodes through mechanistic studies of defects-charge coupling at the lattice scale, phase-stress coupling in single particles, and statistics of the particle network in the composite electrodes of sodium-ion batteries. The research is based on the hypothesis that: (i) the breakdown of the local structural symmetry not only induces lattice distortion and stress gradient at the nanoscale but also impacts the charge distribution in the lattice, (ii) the stochastic nature of material defects is coupled with the phase inhomogeneity in the single particles that gives rise to a stress/strain profile largely deviated from the conventional core-shell pattern; and (iii) in composite electrodes, the charge heterogeneity, mechanical damage, and electrochemical activities co-evolve, resulting in a dynamic ionic/electronic network in the cell. Following the hypothesis, the project includes the following research tasks. (i) Quantify the defect characteristics and map the defects-charging-composition at the nanoscale using controlled synthesis, synchrotron analytical techniques, and computational modeling. (ii) Understand the phase-stress coupling in the single electroceramic particles using the designs of grain engineering and surface coating. (iii) Identify the characteristic metrics of particle network in composite electrodes using machine learning, understand the dynamic evolution of particle network under operating conditions, and interpret the impact of mechanical degradation on battery performance. Overall, the research spans the basic understanding from the lattice scale up to the composite electrode and lays a foundation of mechanistic understanding of chemomechanical degradation in energy storage materia 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.