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

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.