It is apparently important to know the chemical states of lithium in lithium-ion secondary batteries (LIB). We have developed a useful method to visualize the spatial distributions of different chemical states there without using any reference spectra, by applying a multivariate curve resolution technique to the STEM-EELS spectrum image datasets. In this article we introduce examples where this method applied to the chemical state analysis of lithium in LIB.
Industrial and academic demands of electron microscopy analyses of materials for lithium (Li) ion batteries have increased rapidly. Most important roles of electron microscopy in research and development of the battery are to clarify phase changes in electrode materials from micrometer to nanometer and atomic scales in real space. In this paper, we review an application of Li mapping by EELS into a positive electrode material and remark several points to be considered for quantification of Li content. We also refer to electron irradiation effects on electrode materials for Li ion batteries.
Redox reactions at tri-phase interfaces of Yttria Stabilized Zirconia (YSZ), which is a typical electrolyte for a Solid Oxide Fuel Cell (SOFC), and platinum electrode in a vacuum or gas atmosphere are investigated by in situ electron holography and Electron Energy Loss Spectroscopy (EELS). Electron holography shows that heating specimen makes the inner potential shallow at the interface. The inner potential recovers by flowing oxygen gas even at the same high temperature. EELS spectra show the change of valence state of zirconium ions at the interfaces from +4 to +3.
All-solid-state lithium batteries with nonflammable solid electrolytes offer the possibility of avoiding some of the safety issues associated with conventional batteries that contain combustible liquid electrolytes. However, they have a lower power density, and this is mostly attributed to the large resistance to Li-ion transfer across the electrode/solid-electrolyte interface. To date, knowledge of how the local electric potential in the batteries varies during Li-ion transfer has been unattainable. Here we have succeeded in directly observing the electric potential distribution during charge-discharge cycle by in-situ electron holography. Li-ion distribution in the battery and electric double layer formed near the interfaces were directly observed in real space.
For developement of lithium ion battery, diffusion mechanism of lithium ions in the cathode electrode and at the boudary between the cathode and electolyte has been one of the important issues. Using a 50 pm resolved electron microscope (R005), lithium atomic columns in the materials of spinel structure have been observed in annular bright field (ABF) imaging. In this paper, we will show that the column intensity is proportional to the number of lithium ions in the column and also that the spinel structure is transformed into a defective NaCl-type structure by removing litium ions. In addition, we will describe feature of ABF images.
Cerebral cortex in mammals is composed of excitatory projection neurons and inhibitory interneurons. Due to their remarkable diversity, interneurons are thought to play important roles in emergence of higher brain functions. Thus, it is important to know how each interneuron subtypes is sorted into correct positions within the cerebral cortex. We addressed this issue by live imaging of interneurons utilizing glutamate decarboxylase (GAD) 67-GFP (green fluorescent protein) mice, in which GFP is specifically expressed by inhibitory interneurons, and in utero electroporation of appropriate constructs to the site of interneuron generation. We found that interneurons generated in the medial ganglionic eminence of the basal forebrain tangentially migrate to the cortex by way of the intermediate zone and the subventricular zones. These neurons then translocate to the marginal zone near the cortical surface, where they execute multidirectional tangential migration lasting for a few days. Disruption of tangential migration of interneurons in the MZ altered the final distribution of interneurons subtypes, suggesting that this mode of migration play important roles for correct sorting of interneurons subtypes into appropriate regions within the cortex.
In scanning transmission electron microscopy (STEM), a finely focused electron probe is scanned across the specimen and the transmitted and/or scattered electrons from a localized material volume are detected by the post specimen detector(s) as a function of raster position. By controlling the detector geometry, STEM image formation mechanisms and contrast characteristics can be, in principle, controlled. Recently, we have developed a new area detector which we refer to as the “Segmented Annular All Field (SAAF)” detector and which is capable of atomic-resolution STEM imaging. Here we will show the capability of this detector and discuss the possibility of new atomic-resolution STEM imaging mode using this SAAF detector.
Light-sheet microscopy obtains optical sections by illuminating the specimen with sheet-shaped excitation light(s) from the side. This method has great advantages for live imaging of tissues or whole organisms, including low bleaching, low phototoxicity, high-speed, and deep imaging. On the other hand, illuminating from the side causes disadvantages including uneven illumination: several solutions have been proposed to improve the problems.
We have studied the atomic ordering and structures of hard magnetic L10–type FePd and CoPt alloy nanoparticles using aberration-corrected high-resolution transmission electron microscopy (HRTEM). The key issue throughout this study is the atomic ordering in the alloy nanoparticles; in view of excellent hard magnetic properties due to the high magnetocrystalline anisotropy energy, which is dependent on the long-range order parameter. The kinetics of atomic ordering plays a crucial role here, i.e., annealing below a reduced order-disorder transformation temperature is essential in obtaining the L10 ordered phase in small nanoparticles. Imaging using aberration-corrected HRTEM unambiguously revealed the atomic structures of the alloy nanoparticles 2−10 nm in diameter. The technique developed rapidly in the past ten years and is now practically available for the structural analysis in materials science.
Study of Atomic-column EELS mapping by using Cs-corrected STEM was reported by many groups. Atomic resolution EELS maps have been used to determine positions and species of atoms or atomic columns. On the other hand, atomic-column EDS mapping has not been attempted, because x-ray signal collection efficiency become 100 times worse than EELS. Recently, newly large sensor (100mm2) Silicon-Drift type X-ray detector (SDD) was developed for the improvement of signal collection efficiency. This paper reported result of atomic-column EDS mapping from several Oxide specimen by using large solid angle SD-detector with Cs-corrected STEM.
Recent development of scanning electron microscopy (SEM) technique, by which images are taken from back-scattered electron (BSE) from flat block surface of resin-embedded biological specimens, enabled us to obtain high contrast images similar to the ones obtained by TEM. This imaging method facilitates not only a wide area of observation but also a 3D volume analysis such as a FIB/SEM tomography method. However, the BSE image obtained by a conventional SEM under general conditions does not have sufficient contrast and resolution to observe detailed structures of the cell. Here we present a “retarding” method that drastically enhances the quality of the BSE image even when obtained by the conventional SEM. The “retarding” method reduces the primary electron energy by the negative bias voltage between the specimen and the beam column, and it provides high resolution (4 nm) and high contrast images from the resin block surface when combined with optimal SEM settings. Furthermore, when the retarding method is applied to a FIB/SEM 3D reconstruction method, it can reconstruct a larger volume than is achievable by conventional electron tomography, and its high spatial resolution permits the visualization of 3D structures of the cell such as the membrane organization of organelles.