We propose a novel electrolyte additive, 5-acetylthiophene-2-carbonitrile (ATCN) with three functional groups (thiophene, nitrile and carbonyl), to in situ construct a stable cathode interface film that can significantly improve the cycling stability of LiCoO₂ cathode under high-voltage. Adding 0.2% of ATCN into a base electrolyte, the capacity retention of LiCoO₂/Li cell under 4.5 V is enhanced from 53% to 91% after 200 cycles at 1 C, and the cycle number of commercial LiCoO₂/graphite pouch cell (34 Ah) with 10% capacity loss at 0.5 C under a cut-off voltage of 4.45 V is increased from 550 to 800. Experimental characterizations and theoretical calculations reveal that ATCN is preferentially oxidized on LiCoO₂ cathode and utilizes its decomposition intermediates to convert the detrimental components, the hydrogen fluoride and water present in the electrolyte, and the lithium oxide and carbonate resulting from the electrolyte decomposition, into a unique film texture comprised of underneath compacted lithium salts and outer thiophene polymers. The as-constructed film significantly improves the cathode/electrolyte interface stability and the cycling stability of the cell. Such an effective strategy to address the interface instability has never been reported before and paves a new path to improve the energy density of commercial lithium-ion batteries via enhancing cut-off charge voltage.

我们提出了一种新型电解质添加剂，具有三个官能团（噻吩、腈和羰基）的 5-乙酰噻吩-2-甲腈（ATCN），以原位构建稳定的正极界面膜，可显着提高 LiCoO ₂正极在低温下的循环稳定性。高压。在基础电解液中加入0.2%的ATCN，LiCoO ₂ /Li电池在4.5 V下的容量保持率从1 C 200次循环后的53%提高到91%，商业LiCoO ₂ /石墨软包电池的循环次数（ 34 Ah) 在 0.5 C 和 4.45 V 的截止电压下容量损失 10% 从 550 增加到 800。实验表征和理论计算表明 ATCN 优先在 LiCoO _{2 上}氧化阴极并利用其分解中间体将有害成分、电解液中存在的氟化氢和水，以及电解液分解产生的氧化锂和碳酸盐，转化为独特的薄膜结构，由下方压实的锂盐和外部噻吩聚合物组成。所构建的薄膜显着提高了电池的阴极/电解质界面稳定性和循环稳定性。这种解决界面不稳定性的有效策略以前从未有过报道，并为通过提高截止充电电压来提高商业锂离子电池的能量密度铺平了道路。