Lithium metal solid-state batteries are promising as rechargeable energy storage devices due to their non-combustible nature, resistance to high temperatures, and non-corrosive properties. However, their widespread application is hindered by low lithium-ion conductivity and poor compatibility at the electrode/electrolyte interface. To address these challenges, two covalent organic frameworks (COFs), one with functional imidazolium groups (Dha-COFim) and one without (Dha-COF), were synthesized. Ionic liquids (ILs) were then incorporated into these COFs to create quasi-solid-state electrolytes (Dha-COFim-IL and Dha–COF–IL). The Dha-COFim, with its ordered porous structure, forms interconnected ion channels that enable fast lithium-ion transport and enhance lithium salt dissociation, achieving excellent thermal stability, high ionic conductivity (1.74 × 10⁻³ S cm⁻1), and a wide electrochemical window at room temperature. Density functional theory (DFT) calculations showed that the fixed imidazolium groups in Dha-COFim enhance interactions with TFSI⁻ anions, improving lithium salt dissociation. This allows free lithium ions to move quickly through the channels with minimal energy loss. Additionally, the formation of a stable SEI layer rich in LiF and Li3N at the lithium metal/electrolyte interface accelerates Li⁺transport, ensuring uniform lithium deposition and superior battery performance. When combined with a LiFePO4 cathode, the LiFePO4‖Dha-COFim-IL‖Li cell delivers high discharge capacity and excellent cycling stability, providing a new strategy for designing quasi-solid-state electrolytes for high-energy-density lithium batteries.

中文翻译：

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基于离子共价有机框架的准固态电解质在高性能锂金属电池中的应用


锂金属固态电池由于其不可燃性、耐高温性和无腐蚀性，有望成为可充电储能设备。然而，由于锂离子电导率低和电极/电解质界面兼容性差，它们的广泛应用受到了阻碍。为了应对这些挑战，合成了两种共价有机框架 （COF），一种具有功能性咪唑鎓基团 （Dha-COFim），另一种没有 （Dha-COF）。然后将离子液体 （IL） 掺入这些 COF 中，以产生准固态电解质（Dha-COFim-IL 和 Dha-COF-IL）。Dha-COFim 具有有序的多孔结构，可形成互连的离子通道，实现快速锂离子传输并增强锂盐解离，在室温下实现出色的热稳定性、高离子电导率 （1.74 × 10⁻³ S cm⁻1） 和宽电化学窗口。密度泛函理论 （DFT） 计算表明，Dha-COFim 中固定的咪唑鎓基团增强了与 TFSI⁻ 阴离子的相互作用，从而改善了锂盐解离。这使得游离锂离子能够以最小的能量损失快速通过通道。此外，在锂金属/电解质界面处形成富含 LiF 和 Li3N 的稳定 SEI 层可加速 Li⁺ 传输，确保均匀的锂沉积和卓越的电池性能。当与 LiFePO4 正极结合使用时，LiFePO4‖Dha-COFim-IL‖Li 电池具有高放电容量和出色的循环稳定性，为设计高能量密度锂电池的准固态电解质提供了一种新策略。