The high nickel layered oxide cathode LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) is widely used in new energy power and equipment due to its high density and low cost. However, the NCM811 cathode is prone to structural rupture, dissolution of transition metal ions, and damage to the electrode/electrolyte interface under high voltage, causing degradation of battery performance and safety issues. In this paper, 3-(Trifluoromethyl)benzoylacetonitrile (3-TBL) was selected as a film-forming flame-retardant additive for the NCM811 cathode of the high-voltage lithium-ion battery, and the synergistic effect with lithium difluoro(oxalato)borate enhanced the battery cycle and safety performance. The results show that: 3-TBL is oxidized preferentially more than carbonate solvent to form a stable and dense cathode-electrolyte interface film, which effectively prevents the continuous oxidative decomposition of the electrolyte and enhances the rate of cycling and overcharge resistance of the Li/NCM811 cells under high pressure. Furthermore, the 3-TBL modified electrolyte can also delay the thermal decomposition temperature of the commercial electrolyte and improve its flame retardant properties. Kinetic analysis showed that the additive increased the activation energy required for the thermal decomposition reaction of electrolyte and NCM811 cathode mixture. Therefore, the additives 3-TBL improve the intrinsic safety of the electrolyte and electrolyte interface, providing a feasible idea for the development of high energy density and high safety electrolytes.

高镍层状氧化物正极LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811)由于密度高、成本低等特点，被广泛应用于新能源动力和装备。然而，NCM811正极在高压下容易发生结构破裂、过渡金属离子溶解、电极/电解质界面损坏等问题。，导致电池性能下降和安全问题。本文选用3-(三氟甲基)苯甲酰乙腈(3-TBL)作为高压锂离子电池NCM811正极的成膜阻燃添加剂，与二氟(草酸根)锂的协同作用硼酸盐增强了电池循环和安全性能。结果表明：3-TBL比碳酸盐溶剂优先被氧化，形成稳定致密的正极-电解质界面膜，有效阻止了电解质的持续氧化分解，提高了Li/ NCM811 电池在高压下。此外，3-TBL 改性电解质还可以延缓热分解提高商业电解质的温度并提高其阻燃性能。动力学分析表明，添加剂增加了电解质和NCM811正极混合物热分解反应所需的活化能。因此，添加剂3-TBL提高了电解液与电解液界面，为开发高能量密度、高安全性的电解液提供了可行的思路。