Noncontact Imaging of Ion Dynamics in Polymer Electrolytes with Time-Resolved Electrostatic Force Microscopy
Noncontact Imaging of Ion Dynamics in Polymer Electrolytes with Time-Resolved Electrostatic Force Microscopy
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DOI：
10.1021/acsnano.8b07254
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发表时间：
2019-01-01
期刊：
影响因子：
17.1
通讯作者：
Ginger, David S.
中科院分区：
文献类型：
--
作者：
Harrison, Jeffrey S.;Waldow, Dean A.;Ginger, David S.
离子传输过程控制着许多经典和新兴设备的性能，从电池存储到现代混合导电有机电化学晶体管(OECT)。在这里，我们使用时间分辨静电力显微镜(TrEFM)研究聚合物薄膜中的局域离子输运动力学。我们使用局部trEFM和宏观阻抗谱(EIS)建立了局部和宏观测量之间的对应关系。我们使用双(三氟甲烷)磺酰亚胺锂(LiTFSI)掺杂的聚合物薄膜作为模型体系，其中聚合物主链上含有氧代冰片二酰亚胺重复单元和长度为n的低聚环氧乙烷侧链。我们的结果表明，用trEFM在时间域中测量的聚合物局部响应遵循拉伸指数松弛动力学，这与我们在频域EIS数据中测量的相同聚合物的宏观样品的Havriliak-Negami松弛一致。此外，我们发现trEFM结果捕捉到了与EIS结果相同的趋势--随着温度的升高、盐浓度的增加以及聚合物基质中环氧乙烷侧链体积分数的增加，离子动力学的变化与两种测量技术的趋势相同。根据这种相关性，我们得出结论，trEFM数据在纳米尺度上反映了在器件水平上在传统EIS中探测到的相同的离子过程。最后，作为新兴材料合成的一个应用实例，我们使用trEFM和红外光感应力显微镜(PiFM)对用于下一代固态储能应用的两嵌段共聚物电解质进行了成像。
Ionic-transport processes govern performance in many classic and emerging devices, ranging from battery storage to modern mixed-conduction organic electrochemical transistors (OECT). Here, we study local ion-transport dynamics in polymer films using time-resolved electrostatic force microscopy (trEFM). We establish a correspondence between local and macroscopic measurements using local trEFM and macroscopic electrical impedance spectroscopy (EIS). We use polymer films doped with lithium bis(trifluoromethane)sulfonimide (LiTFSI) as a model system where the polymer backbone has oxanorbornenedicarboximide repeat units with an oligomeric ethylene oxide side chain of length n. Our results show that the local polymer response measured in the time domain with trEFM follows stretched-exponential relaxation kinetics, consistent with the Havriliak-Negami relaxation we measure in the frequency-domain EIS data for macroscopic samples of the same polymers. Furthermore, we show that the trEFM results capture the same trends as the EIS results-changes in ion dynamics with increasing temperature, increasing salt concentration, and increasing volume fraction of ethylene oxide side chains in the polymer matrix evolve with the same trends in both measurement techniques. We conclude from this correlation that trEFM data reflect, at the nanoscale, the same ionic processes probed in conventional EIS at the device level. Finally, as an example application for emerging materials syntheses, we use trEFM and infrared photoinduced force microscopy (PiFM) to image a diblock copolymer electrolyte for next-generation solid-state energy storage applications.