Maldonado-Ochoa Santiago A, Fuentes-Quezada Eduardo, Angarita Ivette, Factorovich Matías H, Bruno Mariano M, Acosta Rodolfo H, Longinotti M Paula, Vaca Chávez Fabián, de la Llave Ezequiel, Corti Horacio R
Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, Córdoba, Argentina.
CONICET. Instituto de Física Enrique Gaviola (IFEG), Córdoba, Argentina.
Phys Chem Chem Phys. 2024 Aug 28;26(34):22696-22705. doi: 10.1039/d4cp00605d.
The Li ion mobility through the porous cathode is a critical aspect in the development of commercial Li-air batteries. The bulk transport properties of lithium salts in organic solvents are not reliable parameters for the design of this type of battery since confinement could significantly modify the transport properties, especially when pore diameters are below 10 nm. In this work, we studied the effect of the carbon mesostructure and surface charge on the diffusion of LiTf and LiTFSI salts dissolved in diglyme, typical electrolytes for lithium-air batteries. Interdiffusion coefficients of the salts were determined using a conductimetric method. NMR spectroscopy and relaxometry were used to explore the effect of the carbon structure and the surface charge density on the interaction between the electrolytes and the pore wall. We showed that carbon micro/mesoporous structure plays a critical role in the transport properties of the electrolyte, producing a decrease of up to 2-3 orders of magnitude in the salt interdiffusion coefficients when going from bulk solutions to pores below 4 nm in diameter. It was observed that for pores 25 nm in diameter, the reduction in the diffusion coefficient can be mainly ascribed to the porosity of the sample, giving tortuosity factors around 1. However, for smaller pore sizes (1-10 nm diameter) bigger tortuosity coefficients were observed and were related to strong ion-pore wall interactions. Moreover, it was noticed that the ratio between the diffusion coefficients of the two studied salts dissolved in diglyme, is different in bulk and under confinement, demonstrating that the interactions of the ions with the charged pore wall probably compete with the cation-anion interactions, affecting salt association under confinement.
锂离子在多孔阴极中的迁移率是商用锂空气电池发展的一个关键方面。锂盐在有机溶剂中的体相传输性质对于这类电池的设计而言并非可靠参数，因为受限环境会显著改变传输性质，尤其是当孔径低于10纳米时。在这项工作中，我们研究了碳介观结构和表面电荷对溶解在二甘醇二甲醚中的LiTf和LiTFSI盐扩散的影响，二甘醇二甲醚是锂空气电池的典型电解质。使用电导法测定盐的互扩散系数。利用核磁共振光谱和弛豫测量法来探究碳结构和表面电荷密度对电解质与孔壁之间相互作用的影响。我们表明，碳微/介孔结构在电解质的传输性质中起着关键作用，当从本体溶液转变到直径小于4纳米的孔时，盐互扩散系数降低多达2 - 3个数量级。据观察，对于直径为25纳米的孔，扩散系数的降低主要可归因于样品的孔隙率，曲折因子约为1。然而，对于较小的孔径（直径1 - 10纳米），观察到更大的曲折系数，这与强烈的离子 - 孔壁相互作用有关。此外，注意到溶解在二甘醇二甲醚中的两种研究盐的扩散系数之比在本体和受限条件下是不同的，这表明离子与带电孔壁的相互作用可能与阳离子 - 阴离子相互作用相互竞争，从而影响受限条件下的盐缔合。
