纳米电解质中离子电导率降低的物理根源

IF 16 1区 材料科学 Q1 CHEMISTRY, MULTIDISCIPLINARY
Kara D. Fong*, Clare P. Grey* and Angelos Michaelides*, 
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引用次数: 0

摘要

通过纳米级孔隙的离子传输是许多能量存储和分离技术的核心。尽管在揭示离子-离子、离子-水和离子-孔相互作用导致这些传输过程的复杂相互作用方面做出了重大努力,但人们对受限电解质中离子运动的原子机制仍然知之甚少。在这项工作中,我们使用基于机器学习的分子动力学模拟来表征石墨烯狭缝孔中NaCl水溶液中离子传输的第一性原理级精度。我们发现离子电导率随着约束程度的增加而降低,这一趋势由离子自扩散和动态离子-离子相关性的变化所控制。研究结果表明,受约束离子的自扩散系数受到电解液总密度的强烈影响,电解质总密度随孔内水分子分层的狭缝高度呈非单调变化。我们进一步观察到,随着约束程度的增加,离子的扩散机制向更多的车辆运动方向转变。尽管理想溶液(能-爱因斯坦)假设在该领域普遍存在,但我们发现,在约束条件下,对输运的非理想贡献变得更加明显。这种非理想离子相关性的增加不仅仅是由于通常假设的缔合离子比例的增加,而是由于离子对寿命的增加。通过建立对受限电解质传输的机制理解,这项工作提供了可以指导设计纳米多孔材料的见解,以优化高效和选择性离子传输。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
On the Physical Origins of Reduced Ionic Conductivity in Nanoconfined Electrolytes

Ion transport through nanoscale pores is at the heart of numerous energy storage and separation technologies. Despite significant efforts to uncover the complex interplay of ion–ion, ion–water, and ion–pore interactions that give rise to these transport processes, the atomistic mechanisms of ion motion in confined electrolytes remain poorly understood. In this work, we use machine learning-based molecular dynamics simulations to characterize ion transport with first-principles-level accuracy in aqueous NaCl confined to graphene slit pores. We find that ionic conductivity decreases as the degree of confinement increases, a trend governed by changes in both ion self-diffusion and dynamic ion–ion correlations. We show that the self-diffusion coefficients of our confined ions are strongly influenced by the overall electrolyte density, which changes nonmonotonically with slit height based on the layering of water molecules within the pore. We further observe a shift in the ions’ diffusion mechanism toward more vehicular motion as the degree of confinement increases. Despite the ubiquity of ideal solution (Nernst–Einstein) assumptions in the field, we find that nonideal contributions to transport become more pronounced under confinement. This increase in nonideal ion correlations arises not simply from an increase in the fraction of associated ions, as is commonly assumed, but from an increase in ion pair lifetimes. By building a mechanistic understanding of confined electrolyte transport, this work provides insights that could guide the design of nanoporous materials optimized for efficient and selective ion transport.

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来源期刊
ACS Nano
ACS Nano 工程技术-材料科学:综合
CiteScore
26.00
自引率
4.10%
发文量
1627
审稿时长
1.7 months
期刊介绍: ACS Nano, published monthly, serves as an international forum for comprehensive articles on nanoscience and nanotechnology research at the intersections of chemistry, biology, materials science, physics, and engineering. The journal fosters communication among scientists in these communities, facilitating collaboration, new research opportunities, and advancements through discoveries. ACS Nano covers synthesis, assembly, characterization, theory, and simulation of nanostructures, nanobiotechnology, nanofabrication, methods and tools for nanoscience and nanotechnology, and self- and directed-assembly. Alongside original research articles, it offers thorough reviews, perspectives on cutting-edge research, and discussions envisioning the future of nanoscience and nanotechnology.
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