Data of research paper: Trade-off in Lithium Diffusivity and Transference in High Lithium Concentration Ternary Polymer Ionic Liquids

Data supporting findings of paper https://doi.org/10.1016/j.ssi.2025.116854<br>HighlightsA local optimum for lithium mobility in ternary IL/PIL/lithium salt is observed.Lithium diffusion in ternary electrolyte system is analogous to ILE at low to moderate lithium salt concentrations.A change from neutral pair to free lithium ion conductivity is observed at high lithium salt concentrations.<br>AbstractFor battery architectures that need a solid ion conductor with good contacting performance and high stability against electrochemical oxidation, polymerized ionic liquids (PIL) pose a valuable class of materials. The low conductivity of the binary PIL/ lithium salt system can be increased using a ternary ionic liquid acting as plasticiser. The conductive mechanism of the ternary system is however not fully understood. This work shows the shift in conduction mechanism for the ternary Li−/[1,3]PYR-/PDADMA-FSI system by increasing the lithium salt concentration and comparing the transfer mechanism to binary ionic liquid (IL) electrolyte analogues using pulsed field gradient (PFG) nuclear magnetic resonance (NMR), NMR relaxometry, Raman spectroscopy and electrochemical techniques. Two conducting regimes were found which show a strong trade-off between conductivity and transference number. In the low lithium salt regime (≤35 wt% LiFSI), cluster diffusion of aggregated lithium is the dominating mechanism leading to low transference numbers (0.04–0.15 at room temperature (RT)). The high salt regime (≥50 wt% LiFSI) shows diffusion through free lithium ion hopping transfer, which has a stronger dependence on temperature and yields higher transference numbers (0.31 at RT). Increasing lithium salt concentration shows an inverse linear correlation with conductivity. The electrochemical characteristics of ternary IL/PIL/lithium salt are shown to be highly tuneable by varying the lithium salt fraction, while it maintains excellent characteristics like processability, stability and mechanical function.

本数据集支撑论文https://doi.org/10.1016/j.ssi.2025.116854的研究发现。

研究亮点：
1. 观测到三元离子液体（ionic liquid, IL）/聚合离子液体（polymerized ionic liquids, PIL）/锂盐体系中锂离子迁移率存在局部最优值；
2. 在低至中等锂盐浓度下，三元电解质体系的锂离子扩散行为与离子液体电解质（ionic liquid electrolyte, ILE）相似；
3. 当锂盐浓度较高时，体系的导电机制由中性离子对传导转变为自由锂离子传导。

摘要：
对于需要兼具良好接触性能与优异抗电化学氧化稳定性的固体离子导体的电池体系而言，聚合离子液体（PIL）是一类极具应用价值的材料。二元PIL/锂盐体系的电导率较低，可通过引入三元离子液体作为增塑剂来提升其电导率，但目前学界对该三元体系的导电机制尚未完全明晰。
本研究通过提升锂盐浓度，并将三元Li−/[1,3]PYR-/PDADMA-FSI体系的离子传输机制与二元离子液体（IL）电解质类似体系进行对比，结合脉冲场梯度（pulsed field gradient, PFG）核磁共振（nuclear magnetic resonance, NMR）、NMR弛豫谱、拉曼光谱与电化学表征技术，揭示了该体系导电机制的转变过程。研究发现该体系存在两类导电区域，且两类区域的电导率与离子迁移数之间存在显著的权衡关系。在低锂盐浓度区域（LiFSI占比≤35 wt%），聚集态锂离子的团簇扩散为主要导电机制，对应较低的离子迁移数（室温（room temperature, RT）下为0.04~0.15）；在高锂盐浓度区域（LiFSI占比≥50 wt%），导电机制为自由锂离子的跳跃传输，该机制对温度的依赖性更强，且可获得更高的离子迁移数（室温下为0.31）。锂盐浓度的提升与体系电导率呈负线性相关关系。研究表明，通过调节锂盐占比可对三元IL/PIL/锂盐体系的电化学性能进行精准调控，同时该体系仍可保持优异的可加工性、稳定性与机械性能。