科研之友
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摘要
Rational regulation of the Li-ion (Li+) migration behaviors and charge distribution at the electrolyte-electrode interface is of great significance in pursuit of high-performance lithium metal battery (LMB) chemistry. Herein, unique locally-zwitterionic covalent organic framework nanosheets (ziCOFNs) are developed as Li+ accelerated regulators, whose functions include not only kinetics-boosted Li+ migration but also induces uniform charge distribution in LMBs. The zwitterions act as "dissociation enhancers" to trigger efficient Li+ desolvation, while the abundant COO- units within the nanopores favor rapid Li+ diffusion. In addition, the ordered ionic skeleton dynamically homogenizes the interfacial charge, thereby inhibiting Li dendrite growth and stabilizing the Li-interface chemistry. When implemented as a functional interlayer in the cell configuration, ziCOFNs display ultrahigh transfer number (0.84) and ionic conductivity beyond 4.5 mS cm-1. With such a layer, stable Li plating/stripping (over 6500 h) at 3 mA cm-2 in symmetric cells, and superior long-term cycle performance in high-loading LiFePO4 (9.4 mg cm-2) full cells are achieved. Detailed experimental characterizations combined with theoretical calculations elucidate the mechanism of the zwitterionic framework tuning Li+ migration behaviors. This work is anticipated to shed fresh light on the exploration of zwitterionic crystalline materials in next-generation LMBs. @@@ A Li+ accelerated regulator derived from zwitterionic COF nanosheets is developed for rational modulation of Li+ transport behaviors and charge distribution toward high-performance lithium metal battery chemistry. The acceleration of Li+ dissociation and migration by zwitterions, the dynamic regulation of the interfacial charge distribution, and the host-guest interactions between zwitterions and solvent clusters are demonstrated in crystalline COFs.image
