Solid polymer electrolytes (SPEs) are considered one promising candidate for lithium metal batteries due to their high flexibility, low cost, and roll-to-roll scalability. However, conventional SPEs prepared via ex situ methods are confronted with challenges such as poor contact and high resistance at the electrode|SPE interface, as well as low ionic conductivity at room temperature. In this study, we developed a quasi-solid electrolyte (QSE) using an in situ polymerization approach, employing butyl acrylate as the monomer and incorporating NMP as an additive. Spectroscopic investigations and DFT calculations revealed that NMP tends to form an overleaf-structured [Li(NMP)][TFSI] complex with LiTFSI, promoting lithium salt dissociation. Owing to this advantage, the QSE exhibits high room-temperature ionic conductivity (6.94 × 10 S cm) and an extensive electrochemical stability window (5.01 V vs. Li/Li). Furthermore, the in situ polymerization method facilitates full contact at the interface, enhancing the interfacial stability and reducing the interface resistance, thus resulting in stable cycling of Li|Built-in QSE|Li symmetric cell for 1100 h at 0.1 mA cm. The assembled LiFePO|Built-in QSE|Li cell also demonstrates excellent rate and long-term cycling performance. Our findings offer valuable insights into the interaction between organic additives and lithium salts and present a novel strategy for the development of polymer electrolytes.

中文翻译：

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NMP添加剂增强锂金属电池准固态电解质的原位聚合设计

固体聚合物电解质（SPE）因其高灵活性、低成本和卷对卷可扩展性而被认为是锂金属电池的一种有前途的候选者。然而，通过非原位方法制备的传统SPE面临着电极|SPE界面接触不良、电阻高以及室温下离子电导率低等挑战。在这项研究中，我们采用原位聚合方法开发了一种准固体电解质（QSE），采用丙烯酸丁酯作为单体并加入NMP作为添加剂。光谱研究和DFT计算表明，NMP倾向于与LiTFSI形成背叶结构的[Li(NMP)][TFSI]络合物，促进锂盐解离。由于这一优势，QSE 表现出高室温离子电导率（6.94 × 10 S cm）和广泛的电化学稳定性窗口（5.01 V vs. Li/Li）。此外，原位聚合方法有利于界面充分接触，增强界面稳定性，降低界面电阻，从而使Li|内置QSE|Li对称电池在0.1 mA cm下稳定循环1100 h。组装好的 LiFePO|内置 QSE|Li 电池还表现出优异的倍率和长期循环性能。我们的研究结果为有机添加剂和锂盐之间的相互作用提供了有价值的见解，并为聚合物电解质的开发提出了一种新策略。