Browsing by Author "Ai, Qing"

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    Impact of fabrication methods on binder distribution and charge transport in composite cathodes of all-solid-state batteries
    (IOP Publishing Ltd, 2023) Emley, Benjamin; Wu, Chaoshan; Zhao, Lihong; Ai, Qing; Liang, Yanliang; Chen, Zhaoyang; Guo, Liqun; Terlier, Tanguy; Lou, Jun; Fan, Zheng; Yao, Yan
    The manufacturing process of all-solid-state batteries necessitates the use of polymer binders. However, these binders, being ionic insulators by nature, can adversely affect charge transport within composite cathodes, thereby impacting the rate performance of the batteries. In this work, we aim to investigate the impact of fabrication methods, specifically the solvent-free dry process versus the slurry-cast wet process, on binder distribution and charge transport in composite cathodes of solid-state batteries. In the dry process, the binder forms a fibrous network, while the wet process results in binder coverage on the surface of cathode active materials. The difference in microstructure leads to a notable 20-fold increase in ionic conductivity in the dry-processed cathode. Consequently, the cells processed via the dry method exhibit higher capacity retention of 89% and 83% at C/3 and C/2 rates, respectively, in comparison to 68% and 58% for the wet-processed cells at the same rate. These findings provide valuable insights into the influence of fabrication methods on binder distribution and charge transport, contributing to a better understanding of the binder’s role in manufacturing of all-solid-state batteries.
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    Superior mechanical properties of multilayer covalent-organic frameworks enabled by rationally tuning molecular interlayer interactions
    (PNAS, 2023) Fang, Qiyi; Pang, Zhengqian; Ai, Qing; Liu, Yifeng; Zhai, Tianshu; Steinbach, Doug; Gao, Guanhui; Zhu, Yifan; Li, Teng; Lou, Jun
    Two-dimensional (2D) covalent-organic frameworks (COFs) with a well-defined and tunable periodic porous skeleton are emerging candidates for lightweight and strong 2D polymeric materials. It remains challenging, however, to retain the superior mechanical properties of monolayer COFs in a multilayer stack. Here, we successfully demonstrated a precise layer control in synthesizing atomically thin COFs, enabling a systematic study of layer-dependent mechanical properties of 2D COFs with two different interlayer interactions. It was shown that the methoxy groups in COFTAPB-DMTP provided enhanced interlayer interactions, leading to layer-independent mechanical properties. In sharp contrast, mechanical properties of COFTAPB-PDA decreased significantly as the layer number increased. We attributed these results to higher energy barriers against interlayer sliding due to the presence of interlayer hydrogen bonds and possible mechanical interlocking in COFTAPB-DMTP, as revealed by density functional theory calculations.