All-solid-state Li-ion batteries are expected to be the next generation of batteries with a high energy density and safety. However, for Li-ion batteries to endure high-voltage operations, the decomposition of solid electrolytes must be suppressed first. A high potential at the cathode tends to promote battery degradation because of the oxidation of the cathode electrolyte. This study aims to achieve the high-potential operation of all-solid-state batteries using LiAlCl₄ as a chloride electrolyte with a high oxidation resistance. However, batteries with commonly used oxide electrodes (e.g., LiFePO₄) exhibit low capacity (∼0.5 mA h g⁻¹), despite having working potentials less than the oxidation potential of LiAlCl₄. First-principles calculations and ²⁷Al MAS-NMR measurements suggest that acid–base reactions based on the hard and soft acid–base (HSAB) rule occur between the electrode and the electrolyte. In contrast, a high voltage of ∼3.65 V (vs. Li⁺/Li) and high-capacity utilisation (reversible capacity ∼100 mA h g⁻¹) are observed at room temperature by combining the same chloride electrode (Li₂FeCl₄) without side reactions between these chlorides. These results indicate that material design based on the HSAB rule is also instructive when considering electrode/electrolyte material combinations, which realizes a 3.5 V-class all-solid-state Li-ion battery.

中文翻译：

---

将 HSAB 设计原理应用于具有氯化物电解质的 3.5 V 级全固态锂离子电池

全固态锂离子电池有望成为具有高能量密度和安全性的下一代电池。然而，为了使锂离子电池能够承受高压操作，必须首先抑制固体电解质的分解。由于阴极电解质的氧化，阴极处的高电位趋于促进电池退化。_{本研究旨在使用 LiAlCl 4}作为具有高抗氧化性的氯化物电解质，实现全固态电池的高电位运行。然而，具有常用氧化物电极（例如，LiFePO ₄）的电池表现出低容量（~0.5 mA hg ^-1），尽管其工作电位低于 LiAlCl _{4的氧化电位}. 第一性原理计算和²⁷ Al MAS-NMR 测量表明，基于硬酸碱和软酸碱 (HSAB) 规则的酸碱反应发生在电极和电解质之间。相反，通过组合相同的氯化物电极（Li ₂ FeCl ₄），在室温下观察到~3.65 V（相对于Li ⁺ /Li）的高电压和高容量利用率（可逆容量~100 mA hg ^-1 ）这些氯化物之间没有副反应。这些结果表明，在考虑电极/电解质材料组合时，基于 HSAB 规则的材料设计也具有指导意义，可实现 3.5 V 级全固态锂离子电池。