Herein, the ferrocene redox indicator-based surface film characteristics of spinel lithium manganese oxide (LMO) were evaluated. The pre-cycling of spinel LMO generated a film on the LMO surface. The surface film deposited on LMO surface suppresses further electrolyte decomposition, while the penetration of approximately 0.7 nm-sized redox indicator is not prevented. The facile self-discharge of LMO and regeneration current from the ferrocenium molecule was observed from the redox indicator in a specifically designed four-electrode cell. From this electrochemical behavior, a small-sized HF molecule attack on the LMO surface through a carbonate-based electrolyte-derived film is defined; hence, the prevention of small-sized molecules into the deposited surface film is crucial for the enhancement of LiMn2O4-based lithium-ion batteries.

中文翻译：

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氧化还原活性指示剂揭示沉积在 LiMn ₂ O ₄正极表面膜的渗透特性

在此，评估了尖晶石锂锰氧化物 (LMO) 的基于二茂铁氧化还原指示剂的表面膜特性。尖晶石 LMO 的预循环在 LMO 表面生成了一层薄膜。沉积在 LMO 表面的表面膜抑制了电解质的进一步分解，同时不会阻止约 0.7 nm 大小的氧化还原指示剂的渗透。从专门设计的四电极电池中的氧化还原指示剂观察到 LMO 的轻松自放电和二茂铁分子的再生电流。根据这种电化学行为，定义了一个小尺寸的 HF 分子通过碳酸盐基电解质衍生的薄膜攻击 LMO 表面；因此，防止小分子进入沉积的表面膜对于增强 LiMn2O4 基锂离子电池至关重要。