All-solid-state Li-ion batteries that utilize nonflammable solid electrolytes are considered potential candidates for sustainable energy storage systems. Although sulfide solid electrolytes have been widely explored, their lack of electrochemical stability above 2.7 V requires the application of protective coating layer on 4 V-class cathode materials, whereas the superior oxidative stability of chloride solid electrolytes enables their direct use with such high voltage cathodes. Here, we report a metastable trigonal phase of Li₃YbCl₆ with an ionic conductivity of 1.0 × 10^–4 S·cm^–1 and mixed-metal halide solid electrolytes, Li_3–xYb_1–xZr_xCl₆, with conductivities up to 1.1 mS·cm^–1 at room temperature. Combined neutron, single-crystal, and powder X-ray diffraction methods reveal that Zr-substitution for Yb in Li₃YbCl₆ triggers a trigonal-to-orthorhombic phase transition and forms new, lower energy pathways for Li-ion migration. All-solid-state cell cycling with uncoated >4 V-class cathodes is enabled by the high electrochemical oxidation stability of the mixed-metal halide solid electrolyte.

中文翻译：

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用于高压全固态电池的锂镱基卤化物固体电解质

利用不可燃固体电解质的全固态锂离子电池被认为是可持续储能系统的潜在候选者。尽管硫化物固体电解质已被广泛探索，但它们在 2.7 V 以上缺乏电化学稳定性，需要在 4 V 级正极材料上施加保护涂层，而氯化物固体电解质优异的氧化稳定性使其能够直接用于此类高压正极. 在这里，我们报告了离子电导率为 1.0 × 10 ^–4 S·cm ^–1的 Li ₃ YbCl ₆亚稳态三角相和混合金属卤化物固体电解质 Li _{3– x} Yb _{1– x} Zr _xCl ₆，室温下电导率高达1.1 mS·cm ^–1。结合中子、单晶和粉末 X 射线衍射方法表明，Li ₃ YbCl _{6 中}Yb 的 Zr 取代触发了三角相到正交相变，并为锂离子迁移形成了新的、较低能量的途径。混合金属卤化物固体电解质的高电化学氧化稳定性使具有未涂层 > 4 V 级阴极的全固态电池循环成为可能。