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

钠离子化学技术以其天然丰度、低成本和更广泛的材料选择等优势，为当前可充电电池的锂离子技术提供了一个重要的替代方案，因此为降低美国稀缺元素储量低的风险提供了关键策略。然而，与锂反应相比，钠化学反应会对电极造成相当大的机械变形，并产生更多的应力和退化，从而影响电池的性能。该项目由材料研究部陶瓷项目支持，旨在通过新颖实验、数据分析和建模方法的紧密结合，建立对电池退化的基本理解。这些知识对于阐明钠基电池的老化机制至关重要，这有助于为相同的应用开发提高可靠性的材料。普渡大学和弗吉尼亚理工大学之间的多方面合作为发展STEM相关职业的劳动力提供了独特的培训机会，特别是与满足清洁能源行业的需求有关，预计未来几十年清洁能源行业将大幅增长。这项研究还提供了一个平台，继续招募和参与代表性不足的群体，并对未来的科学家进行融合研究技能和创业培训的教育。本项目旨在通过晶格尺度的缺陷-电荷耦合、单粒子的相-应力耦合以及钠离子电池复合电极中粒子网络的统计等机制研究，全面了解相变电陶瓷电极的化学力学。该研究基于以下假设：(1)局部结构对称性的破坏不仅会导致晶格畸变和纳米尺度的应力梯度，而且会影响晶格中的电荷分布；(2)材料缺陷的随机性与单颗粒中的相不均匀性相结合，导致应力/应变分布很大程度上偏离传统的核-壳模式；（iii）在复合电极中，电荷的非均质性、机械损伤和电化学活动共同演化，导致电池内形成动态的离子/电子网络。根据假设，该项目包括以下研究任务。(i)利用受控合成、同步加速器分析技术和计算建模，量化缺陷特征并绘制纳米级缺陷-充电-组成图。（ii）利用颗粒工程和表面涂层的设计来理解单个电陶瓷颗粒的相应力耦合。（iii）利用机器学习识别复合电极中粒子网络的特征指标，了解粒子网络在运行条件下的动态演化，解释机械退化对电池性能的影响。总的来说，这项研究跨越了从晶格尺度到复合电极的基本理解，为理解储能材料的化学力学退化奠定了基础。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARYSodium-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 clean 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 the underrepresented groups and to educate future scientists on convergent research skills and entrepreneurial training.TECHNICAL SUMMARYThe 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 materiaThis 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.