Lithium-Ion Transport at Electrolyte/Electrode Interface Visualized By Nanoscale Meniscus Cell Microscope

Abstract

Towards the establishment of low-carbon emission society, one urgent issue is to standardize an efficient method to store unused energy. A promised candidate is an electrochemical storage such as lithium-ion batteries. However, it is still hindered as a major problem that the lithium-ion batteries do not conduct with sufficiently high energies capabilities and stable operational cycles. In particular, it is remained as an inefficient barrier of the lithium-ion (de)intercalation at the interface between electrode and electrolyte. It is therefore necessary to determine a crucial factor which influence to the homogeneity in ion transport across the interface by in-situ measurement with nanometer resolution.In this study, the homogeneity in local ion transport of LiFePO4 thin electrodes is investigated by a nanoscale meniscus cell microscope (NMCM). It is a newly established scanning probe microscopy with a nano-size pipet with electrolyte and a reference-electrode.1 As the pipet is in proximity of the LiFePO4 electrode, a meniscus is created. Then, ionic current is only measured through the meniscus when the voltage is applied between reference and LiFePO4electrodes, as shown in Figure 1(a). When the pipet is scanned through the interface in nanometer step, a mapping of the ion current distribution in lithium (de)intercalation is obtained with topographical information in Figure 1 (b). Further, as the pipet was pinned at specific area, it allows us to study the localized ion transport by cyclic voltammetry or charge /discharge process. This new analytic technique will reveal a bottleneck of the ion transport in the materials. leading to the creation of electrode with homogeneous ion transport. Reference: (1) Y. Takahashi, et al., under review.