Topic 1 : Structure and Mechanism Analysis of Functional Materials  

  Crystal structure is one of the most important factors determining the function of inorganic materials. Atomic arrangement, ion sites, vacancy distribution, local distortion, and diffusion pathways strongly affect ion transport, redox behavior, phase stability, and reaction reversibility. 

  Our group focuses on determining new, complex, or poorly understood crystal structures of functional materials. We use crystallographic analysis to identify ion positions, framework connectivity, possible diffusion channels, and structural features that are closely related to material properties. We employ powder X-ray diffraction, Rietveld refinement, electron-density analysis, bond valence sum analysis, ion diffusion pathway calculations, and structural visualization. These approaches allow us to investigate not only the average crystal structure but also possible ion migration pathways, bottleneck sites, structural distortion, and phase evolution.

  A major part of this topic is understanding reaction mechanisms in electrochemical materials. We study how crystal structures change during ion insertion/extraction, how phase transitions occur, and how structural degradation affects electrochemical performance. This helps clarify the origin of capacity, voltage behavior, reversibility, and long-term stability. Although battery materials are our main focus, this structural analysis platform is also applied to O2- conductors for solid oxide fuel cell-related materials, ion diffusion behavior in thin films for semiconductor materials. Through this work, we aim to understand how crystal structures control ion migration and functional properties across different material systems.

Topic 2 : Electrode Materials for Emerging Battery Chemistries

  Our group develops electrode materials for emerging battery systems based on mono- and multivalent charge carriers. These include Li⁺, Na⁺, K⁺, Zn²⁺, Mg²⁺, Ca²⁺, Al³⁺, and Mn²⁺ chemistries in both aqueous and non-aqueous electrolytes.

  We are interested in battery systems beyond conventional lithium-ion technology. Our research covers aqueous batteries, non-aqueous multivalent-ion batteries, hybrid charge-storage systems, and low-cost battery chemistries for large-scale energy storage. Particular attention is given to abundant and sustainable elements such as Na, Zn, Mg, Ca, and Mn.

  A key goal of this research is to understand how different charge carriers are stored in electrode structures. We investigate ion insertion and extraction, phase transitions, conversion reactions, structural degradation, electrolyte participation, and electrode–electrolyte interfacial reactions during charge and discharge. Because multivalent ions have stronger charge density and slower diffusion than monovalent ions, their storage mechanisms are often more complex. We study how crystal structure, interlayer spacing, tunnel size, hydration, solvation structure, and electrolyte composition affect ion transport and reaction reversibility.

  Our research combines materials synthesis, electrochemical testing, structural characterization, and mechanism analysis. By linking crystal structure, charge-storage behavior, and electrochemical performance, we aim to design electrode materials with improved capacity, voltage, rate capability, cycling stability, and safety.

Topic 3 : Solid-State Ion Conductors

  Solid-state ion conductors are key materials for a wide range of electrochemical devices, including all-solid-state batteries and solid oxide fuel cells. Our group studies Li⁺, Na⁺, and O2- conductors with a focus on their crystal structures, ion migration pathways, and electrochemical properties.

  We investigate how structural frameworks affect ion transport. Factors such as diffusion channel geometry, bottleneck size, site occupancy, local disorder, defects, and chemical substitution can strongly influence ionic conductivity. Understanding these structural factors is essential for designing better solid ion conductors. Our research uses crystallographic analysis, Rietveld refinement, bond valence-based pathway analysis, impedance spectroscopy, and electrochemical measurements. These methods help us identify favorable ion diffusion pathways, structural limitations, and possible strategies to improve ionic transport. We also study structural engineering strategies for solid-state ion conductors. These include elemental substitution, defect control, phase stabilization, and microstructural optimization. Through these approaches, we aim to improve ionic conductivity, electrochemical stability, and interface compatibility.

  This topic mainly covers Li⁺ and Na⁺ conductors for solid-state batteries, as well as O2- conductors for solid oxide fuel cell related ceramic materials. The same structural analysis approach is also relevant to other ion-conducting materials.