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5. Direct in situ measurements of electrical properties of solid–electrolyte interphase on lithium metal anodes

Author

Xu, Yaobin, Jia, Hao, Gao, Peiyuan, Galvez-Aranda, Diego E, Beltran, Saul Perez, Cao, Xia, Le, Phung ML, Liu, Jianfang, Engelhard, Mark H, Li, Shuang, Ren, Gang, Seminario, Jorge M, Balbuena, Perla B, Zhang, Ji-Guang, Xu, Wu, and Wang, Chongmin

Subjects
Engineering, Materials Engineering, Electrical and Electronic Engineering, Environmental Engineering, Electrical engineering, Mechanical engineering
Abstract

The solid-electrolyte interphase (SEI) critically governs the performance of rechargeable batteries. An ideal SEI is expected to be electrically insulative to prevent persistently parasitic reactions between the electrode and the electrolyte and ionically conductive to facilitate Faradaic reactions of the electrode. However, the true nature of the electrical properties of the SEI remains hitherto unclear due to the lack of a direct characterization method. Here we use in situ bias transmission electron microscopy to directly measure the electrical properties of SEIs formed on copper and lithium substrates. We reveal that SEIs show a voltage-dependent differential conductance. A higher rate of differential conductance induces a thicker SEI with an intricate topographic feature, leading to an inferior Coulombic efficiency and cycling stability in Li∣∣Cu and Li∣∣LiNi0.8Mn0.1Co0.1O2 cells. Our work provides insight into the targeted design of the SEI with desired characteristics towards better battery performance.

Published
2023

6. Localized High-Concentration Electrolytes Get More Localized Through Micelle-Like Structures

Author

Efaw, Corey M., Wu, Qisheng, Gao, Ningshengjie, Zhang, Yugang, Zhou, Haoyu, Gering, Kevin, Hurley, Michael F., Xiong, Hui, Hu, Enyuan, Cao, Xia, Xu, Wu, Zhang, Ji-Guang, Dufek, Eric J., Xiao, Jie, Yang, Xiao-Qing, Liu, Jun, Qi, Yue, and Li, Bin

Subjects
Condensed Matter - Materials Science
Abstract

Liquid electrolytes in batteries are typically treated as macroscopically homogeneous ionic transport media despite having complex chemical composition and atomistic solvation structures, leaving a knowledge gap of microstructural characteristics. Here, we reveal a unique micelle-like structure in a localized high-concentration electrolyte (LHCE), in which the solvent acts as a surfactant between an insoluble salt in diluent. The miscibility of the solvent with the diluent and simultaneous solubility of the salt results in a micelle-like structure with a smeared interface and an increased salt concentration at the centre of the salt-solvent clusters that extends the salt solubility. These intermingling miscibility effects have temperature dependencies, wherein an exemplified LHCE peaks in localized cluster salt concentration near room temperature and is utilized to form a stable solid-electrolyte interphase (SEI) on Li-metal anode. These findings serve as a guide to predicting a stable ternary phase diagram and connecting the electrolyte microstructure with electrolyte formulation and formation protocols to form stable SEI for enhanced battery cyclability.

Published
2023

12. Monolayer heterojunction interactive hydrogels for high-freedom 4D shape reconfiguration by two-photon polymerization

Author

Tao, Yufeng, Lu, Chengchangfeng, Wang, Xuejiao, Xin, Zhiduo, Cao, Xia, and Ren, Yunpeng

Subjects
Interactive hydrogel, Heterojunction nanostructures, Spatiotemporal programming, Chiral torsion, High freedom
Abstract

Mimicking natural botanical/zoological systems has revolutionarily inspired four-dimensional (4D) hydrogel robotics, interactive actuators/machines, automatic biomedical devices, and self-adaptive photonics. The controllable high-freedom shape reconfiguration holds the key to satisfying the ever-increasing demands. However, miniaturized biocompatible 4D hydrogels remain rigorously stifled due to current approach/material limits. In this research, we spatiotemporally program micro/nano (μ/n) hydrogels through a heterojunction geometric strategy in femtosecond laser direct writing (fsLDW). Polyethylene incorporated N-isopropylacrylamide as programmable interactive materials here. Dynamic chiral torsion, site-specific mutation, anisotropic deformation, selective structural coloration of hydrogel nanowire, and spontaneous self-repairing as reusable μ/n robotics were identified. Hydrogel-materialized monolayer nanowires operate as the most fundamental block at nanometric accuracy to promise high freedom reconfiguration and high force-to-weight ratio/bending curvature under tight topological control. Taking use of this biomimetic fsLDW, we spatiotemporally constructed several in/out-plane self-driven hydrogel grippers, diverse 2D-to-3D transforming from the same monolayer shape, responsive photonic crystal, and self-clenched fists at μ/n scale. Predictably, the geometry-modulable hydrogels would open new access to massively-reproducible robotics, actuators/sensors for microenvironments, or lab-on-chip devices.

Published
2023

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