钠基液态金属电池自放电行为研究与调控

The newly developing liquid metal batteries (LMBs), composed of metal electrodes and molten salt electrolytes, have potential merits of lower-cost and long-life for grid-scale energy storage. The replacing of the existing Li negative electrode with low melting point and low cost Na-based electrodes is an important development direction for practical applications of LMBs. However, when Na is directly used as electrode, the high solubility of Na in molten salt electrolytes results in severe self-discharge and then lowering the coulombic efficiency. In order to address this problem, this proposal is planned to study the self-discharge behaviors of Na based LMBs, and develop the strategies for enhancing the battery performances. The microscopic interaction of Na atoms with molten salt phases and the self-discharge mechanisms will be investigated via in-situ Raman characteristic, ex-situ phase analysis and molecular dynamics simulation. The correlation of Na dissolution behaviors and the strategies for suppressing self-discharge of LMBs will be developed, which provides theoretical guidance and technical support for the designing of low-cost and high-performance Na-based LMBs for large-scale energy storage applications.

基于金属电极和熔盐电解质的液态金属电池成本低、寿命长，是近年发展起来的新型电化学储能技术。以熔点较低、资源丰富的金属Na取代现有的Li负极，是实现液态金属电池实际储能应用的重要发展方向。但液态金属Na在卤化物熔盐中的高溶解度导致钠基液态金属电池自放电严重，使得电池充放电效率较低，难以实际应用。针对这一挑战，本项目拟从钠基液态金属电池自放电行为、调控策略和性能优化三个方面展开研究，结合高温原位拉曼在线检测、离线物相分析和分子动力学模拟，分析金属原子Na与熔盐的微观相互作用，揭示电池自放电机制；基于热力学分析，通过电极活度调控和熔盐成分优化，调控金属Na的溶解行为，发展抑制电池自放电的策略与方法，为构建低成本、高性能Na基液态金属电池储能新体系提供理论参考和技术支撑。

本项目针对钠基液态金属电池中金属钠溶解导致的自放电问题展开研究，结合理论分析与实验表征，分析了金属钠在其卤化物熔体结构中形成“色心”的溶解机制，明晰了金属钠溶解行为的影响因素；采用ICP-AES等实验手段量化分析了金属钠在不同熔盐体系中的溶解行为，验证了金属Na的溶解机制，设计了三元混合阳离子熔盐电解质，有效抑制了金属钠的溶解行为。进一步分析了金属钠与其他阳离子卤化物的相互作用，揭示了金属钠与含锂卤化物熔盐的置换反应机制。发展了系列Bi，Sb，Te基正极合金电极体系，通过分析不同合金电极的放电机制，构建了高效稳定的Na||Bi-Sb液态金属电池新体系，为低成本、高效率、长寿命钠基液态金属电池的设计提供了理论基础与技术支撑。