本文要点：
锂金属电池(LMBs)因其超高的理论比容量(3860 mAh·g-1)而被视为锂离子电池的潜在替代品。然而，由枝晶生长和不可避免的副反应引起的严重不稳定性和安全性问题阻碍了LMBs的商业化。
为了解决这些问题，本文提出了可溶性亲锂共价有机骨架的设计策略。通过引入聚乙二醇作为侧链，两种COFs(CityU-28和CityU-29)不仅变得可溶于容易的旋涂技术，而且可以促进锂离子在电池中的迁移。
此外，当涂覆在LMB的锂阳极上时，两种COFs都可以充当人造固体电解质界面，以防止枝晶生长，从而使得电池能够长期稳定。
值得注意的是，对称的CityU-29@Li电池可以在2 mA cm-2的电流密度和1 mAh cm-2的面积容量下工作超过5000小时。在CityU-29@Li||LiFePO4全电池中，1500次循环后78.9%的显著容量保持率和约99.9%的1.0 C库仑效率也可以实现。
这项工作可以为可溶性COFs提供一个通用的设计策略，并启发它们在不同场景中的应用，特别是与能源相关的领域。
Figure 1. Schematic illustration of a) PEG enabled solubilization and lithium-ion transportation, as well as b) solution preparation process of mPEG-grafted COFs. Inset: photograph of CityU-29 solution. c) Synthesis of CityU-28 and CityU-29.
Figure 2. a) FT-IR spectra of CityU-28, CityU-29, and THB-DMTP. C1s (top), N1s (middle), and O1s (bottom) XPS spectra of b) CityU-28 and c) CityU-29. PXRD patterns of experimental results, Powley refined results, and their differences, as well as simulated AA stacking patterns and Bragg positions of d) CityU-28 and e) CityU-29. Insets: HRTEM images of d) CityU-28 and e) CityU-29, and corresponding fast Fourier transfer patterns.
Figure 3. a) Electrostatic potential (ESP) distribution of CityU-28, where red and blue represent negative and positive charge, respectively. Top-view (top) and front-view (bottom) of calculated b) in-plane and c) out-of-plane lithium-ion migration paths near oxygen and d,e) their diffusion energy barriers in CityU-28. f) Tafel plots of bare Li, CityU-28@Li, and CityU-29@Li symmetric cells and the calculated exchange current density. g) Polarization curve of CityU-29@Li symmetrical cell. Inset: EIS before and after polarization. h) EIS of CityU-29@Li symmetric cells at different temperatures. i) Corresponding Arrhenius curves and comparison of activation energies of bare Li, CityU-28@Li, and CityU-29@Li symmetric cells.
Figure 4. Voltage−time profiles of Li plating/stripping processes of bare Li, CityU-28@Li, and CityU-29@Li symmetrical cells a) at 2 mA cm-2 and 1 mAh cm-2, and b) at 5 mA cm-2 and 5 mAh cm-2. Inset of a): surface and cross section SEM images of (I, II) bare Li and (III, IV) CityU-29@Li deposition morphology after 100 cycles. c) Rate performance of symmetric cells with different current densities and areal capacity from 1 to 10 mA cm-2. d) The Nyquist plots of symmetric CityU29@Li cells measured at 1 and 50 cycles at 2 mA cm-2/1 mAh cm-2. e) Long-term cycling of Li-Cu half cells under 1 mA cm-2/1 mAh cm-2. f) Average Coulombic efficiency (ACE) measurement after 50 cycles.
Figure 5. a) Cycling performance of LFP||Li, LFP||CityU-28@Li, and LFP||CityU-29@Li cells at 1C. (b) Charge–discharge curves of LFP||CityU29@Li at different cycles. (c) Rate performance of LFP||Li, LFP||CityU-28@Li, and LFP||CityU-29@Li at 1, 2, 3, 4, and 5 C.
https://doi.org/10.1002/anie.202422040
