In composite solid-state electrolytes, functional fillers with ferroelectric properties have demonstrated their ability to prompt the dissociation of lithium salt (LiFSI), thereby significantly enhancing ionic conductivity. However, the underlying mechanism has been challenging to fully comprehend, which hinders further improvement in electrolyte performance. Herein, we elucidate the dissociation mechanism of LiFSI induced by the ferroelectric fillers of BaTiO₃. We find that the dipole's direction of tetragonal-BaTiO₃ (T-BTO) can slightly deflect under an external electric field of a battery to enhance the polarization. The {001} planes of T-BTO, aligned along the polarization direction, exhibit a more pronounced ability to dissociate lithium salt and accumulate anions owing to the formation of surface-absorbed FSI⁻ by binding between the O of FSI⁻ and the Ti of T-BTO. Moreover, T-BTO_3−x fillers with enhanced spontaneous polarization by oxygen vacancy defects can further amplify these effects, leading to an increased proportion of free Li⁺ from 19% to 72%. The ionic conductivity of T-BTO_3−x–poly(vinylidene fluoride) composite electrolyte can reach a value as high as 8.4 × 10⁻⁴ S cm⁻¹ at 25 °C. This work reveals the dissociation mechanism of lithium salt due to the introduction of ferroelectric fillers and highlights its great promise for developing practical solid-state composite electrolytes.

中文翻译：

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BaTiO3 自发极化解离锂盐机理

在复合固态电解质中，具有铁电特性的功能填料已证明其能够促进锂盐（LiFSI）的解离，从而显着增强离子电导率。然而，其根本机制一直难以完全理解，这阻碍了电解质性能的进一步提高。在此，我们阐明了BaTiO ₃铁电填料诱导LiFSI的解离机制。我们发现四方BaTiO ₃ (T-BTO)的偶极子方向在电池的外部电场作用下可以轻微偏转以增强极化。 T-BTO 的 {001} 面沿极化方向排列，由于FSI ^-的 O与 FSI - 的 Ti之间结合形成表面吸收的 FSI ^-，因此表现出更明显的离解锂盐和积累阴离子的能力。 T-BTO。此外，通过氧空位缺陷增强自发极化的T-BTO _{3− x}填料可以进一步放大这些效应，导致游离Li ⁺的比例从19%增加到72%。 T-BTO _{3− x} –聚偏二氟乙烯复合电解质的离子电导率在25 ℃时可达8.4 × 10 ^-4 S cm ^-1 。这项工作揭示了由于引入铁电填料而引起的锂盐的解离机制，并凸显了其在开发实用固态复合电解质方面的巨大前景。