Abstract Lithium difluorophosphate (LiPO2F2) as a multi-functional additive is added into the carbonate-based electrolyte to enhance the electrochemical performances of 4.4 V LiNi0.5Co0.2Mn0.3O2/graphite lithium ion batteries (LIBs). Compared with the baseline electrolyte, the addition of 2% LiPO2F2 can significantly improve the electrolyte stability and enlarge the electrochemical window of about 1 V. At the room temperature and cutoff voltage of 4.4 V, the capacity retention of the batteries with 2% LiPO2F2 is increased from 55% to 93% after 150 cycles. At the high temperature of 45 °C, the capacity retention of the battery with 2% LiPO2F2 additive still keeps 86% after 150 cycles, while the coulombic efficiency of the battery without additive begins to decline sharply after 30 cycles. These positive effects are also reflected in the low temperature discharging at −20 °C, cycling at −10 °C, and rate capability. The enhanced performances are attributed to the excellent interfacial film promoted by the additive, which can reduce the interfacial impedance, suppress electrolyte decomposition, and alleviate the side reactions. It is indicated that LiPO2F2 is a promising multi-functional electrolyte additive for high-voltage NCM/graphite LIBs.

中文翻译：

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二氟磷酸锂作为多功能电解质添加剂用于 4.4 V LiNi0.5Co0.2Mn0.3O2/石墨锂离子电池

摘要 将二氟磷酸锂（LiPO2F2）作为多功能添加剂加入碳酸盐基电解液中，以提高4.4 V LiNi0.5Co0.2Mn0.3O2/石墨锂离子电池（LIBs）的电化学性能。与基线电解液相比，添加 2% LiPO2F2 可显着提高电解液稳定性并扩大约 1 V 的电化学窗口。 在室温和 4.4 V 截止电压下，2% LiPO2F2 电池的容量保持率为150 个循环后从 55% 增加到 93%。在45℃高温下，添加2% LiPO2F2添加剂的电池在150次循环后容量保持率仍保持在86%，而不含添加剂的电池在30次循环后库仑效率开始急剧下降。这些积极的影响也反映在 -20 °C 的低温放电、-10 °C 的循环和倍率能力上。性能的提高归因于添加剂促进了优异的界面膜，可以降低界面阻抗，抑制电解质分解，减轻副反应。结果表明，LiPO2F2 是一种很有前途的用于高压 NCM/石墨 LIB 的多功能电解质添加剂。