The increasingly widespread use of electric vehicles has necessitated the development of high-energy batteries capable of operating under harsh conditions, e.g., at elevated temperatures and high charge/discharge rates. Hence, considerable attention has been focused on enhancing the safety of lithium-ion batteries (LIBs). Herein, a thermoresponsive polymer, poly(vinylidene fluoride-co-trifluoroethylene) with 75 mol% vinylidene fluoride and 25 mol% trifluoroethylene (TrFE-25), is employed as an electrolyte additive to enhance the thermal stability of LIBs (LiCoO2/graphite full cells). Under thermal-abuse conditions, i.e., above a certain threshold temperature, the TrFE-25-containing electrolyte turns into a gel, thereby abruptly increasing of the electrolyte viscosity and interfacial resistance. The gel layers block ion transport, suppress exothermic reactions between the electrodes and electrolyte, and hinder separator shrinkage via adhesive bonding to the anode and cathode, thus preventing internal short-circuiting and enhancing battery safety. According to the results of cycling tests, the addition of TrFE-25 to the baseline electrolyte has no negative effects under normal conditions. Therefore, the proposed methodology holds promise for improving the safety of LIBs, particularly those with flammable carbonate-based electrolytes, and paves the way for the widespread use of these batteries in electric vehicles.

中文翻译：

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热响应性聚偏二氟乙烯-三氟乙烯共聚物电解质实现更安全的锂离子电池


电动汽车的日益广泛使用需要开发能够在恶劣条件下运行的高能电池，例如在高温和高充电/放电速率下。因此，提高锂离子电池（LIB）的安全性受到了极大的关注。本文采用热响应聚合物，即含有 75 mol% 偏二氟乙烯和 25 mol% 三氟乙烯的聚（偏二氟乙烯-三氟乙烯）（TrFE-25）作为电解质添加剂，以增强锂离子电池（LiCoO2/石墨全细胞）。在热滥用条件下，即高于某个阈值温度，含有TrFE-25的电解质变成凝胶，从而突然增加电解质粘度和界面电阻。凝胶层阻止离子传输，抑制电极和电解质之间的放热反应，并通过与阳极和阴极的粘合剂粘合来阻止隔膜收缩，从而防止内部短路并增强电池安全性。根据循环测试结果，在正常条件下，在基线电解液中添加TrFE-25不会产生负面影响。因此，所提出的方法有望提高锂离子电池的安全性，特别是那些使用易燃碳酸酯基电解质的锂离子电池，并为这些电池在电动汽车中的广泛使用铺平道路。