Owing to their high-voltage stabilities, halide superionic conductors such as Li₃YCl₆ recently emerged as promising solid electrolyte (SE) materials for all-solid-state batteries (ASSBs). It has been shown that by either introducing off-stoichiometry in solid-state (SS) synthesis or using a mechanochemical (MC) synthesis method the ionic conductivities of Li_3–3xY_1+xCl₆ can increase up to an order of magnitude. The underlying mechanism, however, is unclear. In the present study, we adopt a hopping frequency analysis method of impedance spectra to reveal the correlations in stoichiometry, crystal structure, synthesis conditions, Li⁺ carrier concentrations, hopping migration barriers, and ionic conductivity. We show that unlike the conventional Li₃YCl₆ made by SS synthesis, mobile Li⁺ carriers in the defect-containing SS-Li_3–3xY_1+xCl₆ (0 < x < 0.17) and MC-Li_3–3xY_1+xCl₆ are generated with an activation energy and their concentration is dependent on temperature. Higher ionic conductivities in these samples arise from a combination of a higher Li⁺ carrier concentration and lower migration energy barriers. A new off-stoichiometric halide (Li_2.61Y_1.13Cl₆) with the highest ionic conductivity (0.47 mS cm^–1) in the series is discovered, which delivers exceptional cycling performance (∼90% capacity retention after 1000 cycles) in ASSB cells equipped with an uncoated high-energy LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) cathode. This work sheds light on the thermal activation process that releases trapped Li⁺ ions in defect-containing halides and provides guidance for the future development of superionic conductors for all-solid-state batteries.

中文翻译：

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全固态电池卤化物超离子导体：合成和组成对锂离子电导率的影响

由于其高电压稳定性，卤化物超离子导体（例如Li ₃ YCl _{6 ）}最近成为全固态电池（ASSB）有前途的固体电解质（SE）材料。研究表明，通过在固态（SS）合成中引入非化学计量或使用机械化学（MC）合成方法，Li _{3–3 x} Y _{1+ x} Cl ₆的离子电导率可以提高到一个数量级震级。然而，其根本机制尚不清楚。在本研究中，我们采用阻抗谱的跳频分析方法来揭示化学计量、晶体结构、合成条件、Li ⁺载流子浓度、跳频迁移势垒和离子电导率之间的相关性。我们发现，与通过SS合成制备的传统Li ₃ YCl ₆不同，含有缺陷的SS-Li _{3–3 x} Y _{1+ x} Cl ₆ (0 < x < 0.17) 和MC-Li _{3–中存在移动的Li} ^{+载流子。} _{3 x} Y _{1+ x} Cl ₆通过活化能产生，并且它们的浓度取决于温度。这些样品中较高的离子电导率源于较高的Li ⁺载流子浓度和较低的迁移能垒。发现了该系列中离子电导率最高 (0.47 mS cm ^–1 ) 的新型非化学计量卤化物 (Li _2.61 Y _1.13 Cl ₆ )，可在 ASSB 电池中提供卓越的循环性能（1000 次循环后容量保持率为 90%）配备无涂层高能LiNi _0.8 Mn _0.1 Co _0.1 O ₂ (NMC811)阴极。这项工作揭示了释放含缺陷卤化物中捕获的Li ⁺离子的热激活过程，并为全固态电池超离子导体的未来发展提供指导。