Polymer electrolytes have been gaining much attention in battery research and development due to their non-volatility, possibility to reduce decomposition at the electrodes, flexibility, and improved safety. Polyelectrolytes are polymer systems in which one of the conducting species (anion or cation) is chemically bonded to the polymer backbone. Here, we report a Nafion-based polyelectrolyte system (Nafion-Li) derived by ion-exchange of the proton in the sulfonic acid group (–SOH) with Li to enable Li-ion conduction. To further enhance the electrochemical properties, a pyrrolidinium-based ionic liquid (IL) of high ionic conductivity and wide electrochemical stability window was incorporated in the polyelectrolyte as an active plasticizer. The ionic conductivity of the Nafion-Li polymer electrolyte increased from 10 S cm to 10 S cm with the addition of the IL electrolyte solution. Cyclic voltammetry measured in the voltage range of −0.4 V to 2 V shows a lithium deposition peak and a lithium stripping peak, confirming a reversible redox reaction in the prepared polymer electrolytes. Galvanostatic charge-discharge studies of the optimized polymer electrolytes were performed by assembling coin type half cells with LiFePO as the cathode and lithium as the anode in the voltage range 2.5 to 4.2 V. The first charge and discharge capacity of the IL-added “Nafion-Li” polymer electrolyte were 160 and 152 mAh/g, respectively. In-situ impedance spectroscopy and cyclability of the assembled cells are also discussed.

中文翻译：

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用于锂充电电池的基于 Nafion 的聚电解质

聚合物电解质由于其不挥发性、减少电极分解的可能性、灵活性和更高的安全性而在电池研究和开发中受到广泛关注。聚电解质是其中一种导电物质（阴离子或阳离子）通过化学键合到聚合物主链上的聚合物系统。在这里，我们报道了一种基于 Nafion 的聚电解质系统（Nafion-Li），该系统是通过磺酸基（-SOH）中的质子与 Li 进行离子交换来实现锂离子传导的。为了进一步增强电化学性能，在聚电解质中加入了具有高离子电导率和宽电化学稳定性窗口的吡咯烷鎓离子液体（IL）作为活性增塑剂。随着IL电解质溶液的添加，Nafion-Li聚合物电解质的离子电导率从10 S cm增加到10 S cm。在-0.4 V至2 V电压范围内测量的循环伏安法显示出锂沉积峰和锂剥离峰，证实了所制备的聚合物电解质中的可逆氧化还原反应。通过组装以 LiFePO 为正极、锂为负极的硬币型半电池，在 2.5 至 4.2 V 的电压范围内对优化后的聚合物电解质进行恒流充放电研究。添加 IL 的“Nafion”的首次充放电容量-Li”聚合物电解质分别为160和152mAh/g。还讨论了组装电池的原位阻抗谱和可循环性。