Collaborative Research: Material Simulation-driven Electrolyte Designs in Intermediate-temperature Na-K / S Batteries for Long-duration Energy Storage

长时间储能技术（10小时，LDES）对于间歇性可再生能源（如太阳能/风能）的扩展至关重要。传统的Na-S和K-S电池由于其低成本和使用地球丰富的元素而对LDES具有吸引力。然而，由于其工作温度高达300-350℃，以及相关的降解和安全问题，它们的部署受到严重阻碍。该项目将采用材料设计和模拟驱动的方法开发创新电解质，以溶解Na-S和K-S电池中的不溶性反应产物，并推进对潜在溶解机制的了解。这种新型电解质将提高反应动力学，因此操作温度可以降低到60-120℃，这不仅提高了热稳定性，还降低了操作成本。项目活动将整合研究和教育，针对从K-12到研究生院的学生，通过实践经验、建议和研究整合，在各个层面促进代表性不足的社区的教育。传统的碱性金属硫（AMS）电池面临的主要挑战是在放电过程中形成固体M2S2和M2S化合物（M = Na， K），其电化学动力学较差。这限制了可逆氧化还原范围主要限于S/M2S3反应，降低了比容量和能量密度。该项目的目标是确定和开发能够溶解M2S2/M2S的新溶剂，以取代传统的醚电解质，从而使M2S2/M2S具有电化学活性。这将使硫的比容量从500 mAh/g增加到1000-1500 mAh/g，并具有较长的循环寿命。该项目将利用模拟驱动的方法来设计电解质，例如结合分子动力学（MD）模拟和机器学习（ML）。MD模拟计算溶剂化自由能，ML能够高通量筛选具有优越M2S2和M2S溶解度的溶剂。有希望的候选者将通过实验验证。在实验确定了高效溶剂后，多尺度/多模态表征将用于全面了解该体系的基本溶解机制、电化学和输运。将构建和测试一个ah级原型，并对开发的材料和设备的成本进行大规模部署分析。知识和研究工具的进步将有助于开发下一代长时间储能电池。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知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Long-duration energy storage technology (10 hours, LDES) is critical to the expansion of intermittent renewable energy (e.g., solar/wind). Conventional Na-S and K-S batteries are attractive for LDES due to their low cost and the use of earth-abundant elements. However, their deployment is severely hindered by their high operational temperature of 300-350oC and associated degradation and safety issues. This project will use materials design and simulation-driven approaches to develop innovative electrolytes to dissolve insoluble reaction products in Na-S and K-S batteries and advance knowledge on underlying dissolution mechanisms. Such novel electrolytes will enhance reaction kinetics so the operation temperature can be reduced to 60-120oC, which not only enhances thermal stability but also decreases operational costs. The new material systems from this project have the potential to be deployed for LDES, which enhances the economic competitiveness and sustainability of U.S. The project activities will integrate research and education, targeting students from K-12 to graduate school and promoting underrepresented communities' education through hands-on experiences, advising, and research integration across all levels. The primary challenge in traditional alkaline metal sulfur (AMS) batteries arises from the formation of solid M2S2 and M2S compounds during discharge (M = Na, K), which exhibit poor electrochemical kinetics. This limits the reversible redox range mainly to S/M2S3 reactions, reducing specific capacity and energy density. The goal of this project is to identify and develop new solvents that can dissolve M2S2/M2S readily to replace conventional ether electrolytes, which will in turn make M2S2/M2S electrochemically active. This will double the specific capacity of sulfur from 500 mAh/g in ether electrolytes to 1000-1500 mAh/g, along with a long cycle life. The project will utilize a simulation-driven approach to design electrolytes, such as combining molecular dynamics (MD) simulations and machine learning (ML). MD simulations calculate solvation free energy, and ML enables high-throughput screening for solvents with superior M2S2 and M2S solubilities. Promising candidates will be experimentally validated. After experimentally confirming the high-performance solvents, multi-scale/multi-modal characterizations will be used to understand the fundamental dissolution mechanisms, electrochemistry and transport in the proposed system comprehensively. An Ah-level prototype will be constructed and tested, and the cost of developed materials and devices will be analyzed for large-scale deployment. The advances in knowledge and research tools together will help develop next-generation batteries for long-duration energy storage.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.