Extending the charging cutoff voltage of lithium cobalt oxide (LCO) cathodes is an effective strategy to enhance the energy density of lithium-ion batteries (LIBs), while the formation of a poor cathode–electrolyte interphase (CEI) has limited their widespread application. Various electrolyte additives, particularly nitrile compounds, have shown promise in addressing these interfacial issues, though the fundamental design principles remain unclear. Herein, we introduce an interfacial leverage mechanism utilizing nitriles adsorbed on the LCO surface to fine-tune the CEI composition. The suitability of a nitrile additive for high-voltage LCO is determined by the repulsive interaction with the solvent (E_sol) and the attractive interaction with the anion (E_anion). The former inhibits solvent decomposition, while the latter facilitates the anion decomposition during CEI construction. These interactions can be tailored through the functional design of nitrile compounds, as demonstrated using 3,5-bis(trifluoromethyl)benzonitrile (BFBN) in a commercial carbonate electrolyte. The BFBN molecules adsorb onto the LCO surface through coordination between cyano groups (–CN) and cobalt (Co) atoms. Exhibiting repulsive interactions with the solvent and attractive interactions with the anion through anion–π interactions, BFBN suppresses carbonate solvent dehydrogenation while promoting the decomposition of PF₆⁻ anions to form an inorganic-rich CEI. A 1 wt% addition of BFBN enables 4.55 V-graphite‖LCO pouch cells to achieve a lifespan over 550 cycles at 25 °C and more than 145 cycles at 45 °C, significantly surpassing the lifespan of around 110 and 50 cycles observed in the baseline electrolyte. This work provides new insights into the design of high-voltage electrolyte additives for high-energy-density LIBs.

中文翻译：

---

阴离子-π 相互作用和溶剂脱氢控制可实现高压锂离子电池


延长钴酸锂 （LCO） 阴极的充电截止电压是提高锂离子电池 （LIB） 能量密度的有效策略，而不良阴极电解质界面 （CEI） 的形成限制了其广泛应用。各种电解质添加剂，尤其是丁腈化合物，已经显示出解决这些界面问题的前景，尽管基本设计原则仍不清楚。在此，我们介绍了一种界面杠杆机制，利用吸附在 LCO 表面的腈来微调 CEI 组成。丁腈添加剂对高压 LCO 的适用性取决于与溶剂 （E_sol） 的排斥相互作用以及与阴离子 （E_阴离子） 的吸引力相互作用。前者抑制溶剂分解，而后者促进 CEI 构建过程中的阴离子分解。这些相互作用可以通过丁腈化合物的功能设计进行定制，如在商业碳酸盐电解质中使用 3,5-双（三氟甲基）苯甲腈 （BFBN） 所证明的那样。BFBN 分子通过氰基 （–CN） 和钴 （Co） 原子之间的配位吸附到 LCO 表面。BFBN 表现出与溶剂的排斥性相互作用，并通过阴离子-π 相互作用与阴离子产生有吸引力的相互作用，抑制碳酸盐溶剂脱氢，同时促进 PF₆⁻ 阴离子分解，形成富含无机物的 CEI。添加 1 wt% 的 BFBN 使 4.55 V 石墨‖LCO 软包电池在 25 °C 下的使用寿命超过 550 次，在 45 °C 下的使用寿命超过 145 次，显著超过了基线电解液中观察到的约 110 次和 50 次循环的使用寿命。 这项工作为高能量密度 LIB 的高压电解质添加剂的设计提供了新的见解。