Lithium sulfur (Li-S) batteries are a promising technology due to their high energy density and low cost. However, the polysulfide shuttle effect remains a significant cause of degradation in Li-S batteries and there is an urgent need for improved cathode materials that can effectively trap polysulfides to minimize this phenomenon. In this work, we propose a BaTiO₃ (BTO) cathode with controlled dipole alignment as a ferroelectric additive to improve polysulfide trapping. To evaluate the polysulfide adsorption on BTO with different degrees of dipole alignments, operando ultraviolet–visible diffuse reflectance spectroscopy (UV-vis DRS) and optical microscopy were used to track the shuttling of polysulfides in cycling Li-S batteries. The poled BTO cathodes demonstrated not only superior initial capacity, but also lower concentrations of shuttling polysulfides during cycling, resulting in a 24% improvement in capacity after 500 cycles as compared with the unpoled material. These improvements were attributed to the relatively strong electrostatic field induced by the highly aligned dipoles on the poled BTO surface, confirmed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and density functional theory (DFT) modelling. We thus demonstrate, for the first time, the beneficial role of bulk aligned dipoles in ferroelectric materials for the suppression of polysulfide shuttling, and the resulting superior long-term cycling performance.

中文翻译：

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通过铁电 BaTiO3 中的偶极排列增强锂硫电池中的多硫化物捕获


锂硫（Li-S）电池由于其高能量密度和低成本而成为一种有前途的技术。然而，多硫化物穿梭效应仍然是锂硫电池退化的一个重要原因，迫切需要改进的正极材料能够有效捕获多硫化物，以最大限度地减少这种现象。在这项工作中，我们提出了一种具有受控偶极子排列的 BaTiO ₃ (BTO) 阴极作为铁电添加剂来改善多硫化物捕获。为了评估具有不同偶极排列程度的 BTO 上的多硫化物吸附，使用操作紫外可见漫反射光谱（UV-vis DRS）和光学显微镜来跟踪循环锂硫电池中多硫化物的穿梭。极化的 BTO 阴极不仅表现出优异的初始容量，而且在循环过程中穿梭多硫化物的浓度较低，与未极化的材料相比，500 次循环后容量提高了 24%。这些改进归因于极化 BTO 表面上高度排列的偶极子引起的相对较强的静电场，X 射线光电子能谱 (XPS)、拉曼光谱和密度泛函理论 (DFT) 建模证实了这一点。因此，我们首次证明了铁电材料中块状排列偶极子对于抑制多硫化物穿梭的有益作用，以及由此产生的卓越的长期循环性能。