热电池电解质与隔膜材料研究进展

Research progress of molten salt electrolyte and separator materials for thermal batteries

作为一种在使用时使电解质熔融而激活工作的储备电池,热电池的熔融盐电解质是决定其性能的关键要素之一。近年来,通过组分调控电解质新体系来降低熔点和提高离子电导率成为研究热点,利用基于热力学理论和热力学数据库的相图计算(CALPHAD)进行三元甚至四元熔融盐体系的筛选,为得到性能优异的熔融盐电解质提供便利,从而达到提升热电池性能特别是延长电池寿命的目的。熔融盐功能组分如黏结剂MgO等的加入可以减少电解质熔融盐泄漏,其用量和结构的优化可以提高熔融盐与电解液的亲和性以及减小电池内阻,进而提高热电池电化学性能;无机纤维隔膜的引入可以更大程度地减小或者消除无离子传导MgO的使用,同时无机纤维隔膜的使用提高了电池的安全可靠性,也为热电池的小型化提供了指导方向。

As a reserve battery that heats the electrolyte to melt when applied to use,thermal batteries are mostly used in military and aerospace fields.At room temperature,its electrolyte is in a solid state without ionic conduction,so that the battery does not self-discharge,which is a necessary condition for its long-term storage.The molten salt electrolyte of the thermal battery is one of the key elements that determine its performance.In recent years,the application of a new system of component-controlled molten salt electrolyte to reduce the melting point and increase the ionic conductivity has become one of the research hotspots such as adding low-melting component salts to lower the melting point of the molten salt system,or using the entropy increase principle to optimize the performance of molten salt by adding new components.Combining with theoretical calculations and simulations,the ternary or even quaternary molten salt is developed to improve thermal battery performance,especially to extend battery life.In order to make the use of thermal batteries more common,the molten salt of the low melting point system is utilized.The introduction of some precious metal cations and the use of nitrates can reduce the melting temperature of the molten salt system to below 300℃,which is the standard for its common use.The addition of functional components such as MgO binder can reduce the probability of electrolyte molten salt leakage,but its dosage and structure need to be optimized to reduce the internal resistance of the battery and improve the retention of molten salt,which can improve the electrochemical performance of thermal batteries.Further,the introduction of inorganic fiber separators can reduce or eliminate the use of MgO binder to a greater extent and improve the safety and reliability of the battery,which also provides guidance for miniaturization of thermal battery.