Carbonate-based electrolytes used in Li-ion batteries encounter various challenges in extreme electrochemical environments, and hence their application requires various additives, especially when used with high voltage cathode materials. These additives are designed to form protective interphases that prevent parasitic carbonate oxidation, while in certain cases they stabilize electrolytes from reduction at anode surfaces or even serve as flame-retardants that postpone the thermal runaway during overcharge. However, most of these additives casts negative effects, lowering ionic conductivity of electrolyte or impairing the compatibility between cathode and electrolyte. An ideal solution of minimizing the presence of these inert molecules is to identify an additive that structurally integrates these multiple functions into a single compound. In this work, we report a novel additive, diethyl(thiophen-2-ylmethyl)phosphonate (DTYP). Its 0.5% presence in a base electrolyte dramatically improves the capacity retention of a high voltage Li-ion cell using LiNi_0.5Mn_1.5O₄ from 18% to 85% after 280 cycles at 1C at 60 °C, increases the endothermic reaction onset temperature from 193 °C to 223 °C, and reduces the self-extinguishing time of the electrolyte from 88 s to 77 s. Thus, such a multifunctional additive presents a cost-efficient solution to the issues often faced in high voltage lithium-ion batteries.

中文翻译：

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（噻吩-2-基甲基）膦酸二乙酯：一种用于高压电池的新型多功能电解质添加剂†

锂离子电池中使用的基于碳酸盐的电解质在极端的电化学环境中会遇到各种挑战，因此其应用需要各种添加剂，尤其是与高压阴极材料一起使用时。这些添加剂旨在形成可防止寄生碳酸根氧化的保护性相，而在某些情况下，它们可防止电解质在阳极表面被还原，甚至起到阻燃剂的作用，从而在过充电期间推迟热失控。然而，这些添加剂中的大多数会产生负面影响，降低电解质的离子电导率或损害阴极与电解质之间的相容性。最小化这些惰性分子的存在的理想解决方案是确定一种添加剂，该添加剂在结构上将这些多种功能整合到一个化合物中。在这项工作中，我们报告了一种新型的添加剂，二乙基（噻吩-2-基甲基）膦酸酯（DTYP）。它在基础电解质中的含量为0.5％，大大提高了使用LiNi的高压锂离子电池的容量保持率在60°C下于1C进行280次循环后，将_0.5 Mn _1.5 O ₄从18％降至85％，将吸热反应的起始温度从193°C升高至223°C，并将电解质的自熄时间从88 s降低至77秒 因此，这种多功能添加剂为高电压锂离子电池中经常面临的问题提供了一种经济高效的解决方案。