Cathode electrolyte interphase (CEI) film is suffering from electrochemical disintegration and physical disturbance caused by particles’ volumetric variation while layered oxide cathodes are operated at high voltage. However, most CEI design strategies only focus on the electrochemical stability of the film. Herein a novel tough Janus-faced CEI film with excellent high-voltage stability and ultrahigh Young's modulus ∼ 30 Gpa is in-situ constructed by succinonitrile (SN) and cyclohexylbenzene (CHB) additives. SN is adsorbed on electrode particles due to the coordinative interaction with transition metals, then CHB is electrochemically polymerized generating an outer layer subsequently. This Janus-faced film not only prevents the decomposition of electrolyte and the irreversible phase transition on particles surface, but also suppresses the particles cracking and Co element dissolution. With the multiply protection of this film, the cyclic performances of LiCoO₂ and LiNi_0.8Co_0.1Mn_0.1O₂ cathodes are remarkably improved, over 500 & 600 cycles at the high voltages of 4.6 & 4.7 V vs. Li⁺/Li, respectively. This work not only provides a novel design of functional CEI film, but also throws light on other electrochemical protection fields such as metal corrosion.

当层状氧化物正极在高压下运行时，正极电解质界面 (CEI) 膜会遭受电化学分解和颗粒体积变化引起的物理干扰。然而，大多数 CEI 设计策略只关注薄膜的电化学稳定性。在此，由丁二腈 (SN) 和环己基苯 (CHB) 添加剂原位构建了一种新型坚韧的 Janus 面 CEI 薄膜，具有出色的高压稳定性和超高杨氏模量 ∼ 30 Gpa。由于与过渡金属的配位相互作用，SN 被吸附在电极颗粒上，然后 CHB 发生电化学聚合，随后产生外层。这种双面膜不仅可以防止电解质的分解和颗粒表面不可逆的相变，同时也抑制了颗粒的开裂和Co元素的溶解。有了这层薄膜的多重保护，LiCoO的循环性能₂和 LiNi _0.8 Co _0.1 Mn _0.1 O ₂阴极得到显着改善，分别在 4.6 和 4.7 V相对于Li ⁺ /Li 的高电压下超过 500 和 600 个循环。该工作不仅提供了一种新颖的功能性CEI膜设计，也为金属腐蚀等其他电化学保护领域提供了启示。