Hiroaki Kobayashi

A hybrid deep learning framework integrating Kolmogorov–Arnold networks and a self-attention mechanism for high-precision prediction of battery cathode material properties from crystallographic perspectives.

Sodium‐ion batteries require high‐mass‐loading electrodes to achieve competitive cell‐level energy density for large‐scale energy storage. However, conventional wet processing often induces structural heterogeneity and mechanical instability in thick electrodes. In this work, we demonstrate a versatile and accessible laboratory‐scale dry‐processing strategy requiring conventional ball‐milling and thermal pressing. The degree of PTFE fibrillation can be regulated through controlled ball‐milling to construct a stable and continuous electrode architecture. The optimized dry‐processed sodium vanadium manganese phosphate (NVMP) cathode, with active material loading exceeding 40 mg cm ⁻² , exhibits reduced polarization, stable interface evolution, and boosted ion diffusion, which meets the requirements of lab‐scale testing and research for thick electrodes with high capacity. Hard‐carbon||NVMP full cells further demonstrate reliable rate capability and prolonged cycling stability. This work demonstrates a versatile and accessible laboratory‐scale strategy to construct stable thick‐electrode architectures by regulating PTFE fibrillation. The methodology provides a convenient route for laboratory research on dry‐processed electrodes and high‐capacity sodium‐ion batteries.

Layered lithium cobalt oxide (LiCoO2) is a benchmark cathode material for Li-ion batteries; however, conventional solid-state synthesis requires high temperatures (∼800 °C) and prolonged processing. Here, we demonstrate a low-temperature hydroflux method for LiCoO2 and elucidate its formation mechanism using in situ X-ray absorption spectroscopy (XAS), complemented by molecular dynamics (MD) simulations. Under alkali hydroflux conditions, moisture (H2O) induces a partial local structural transformation of Co(OH)2 toward an α-Co(OH)2-like coordination environment, locally expanding the interlayer region. The structural evolution creates pathways for lithium incorporation into the Co(OH)2 interlayers at temperatures as low as ∼150 °C, enabling the low-temperature nucleation and growth of layered LiCoO2. In contrast, syntheses under dry conditions proceed through CoO and Co3O4 intermediates and do not yield phase-pure LiCoO2 at these temperatures. Time-resolved in situ XAS reveals distinct reaction pathways in the presence and absence of moisture, identifying intermediate cobalt valence states and local structural changes consistent with the proposed mechanism. Supplementary MD simulations are consistent with this interpretation, suggesting that interlayer H2O/OH– species may assist Li+ incorporation into Co(OH)2. Collectively, these findings provide mechanistic insights into moisture-enabled low-temperature formation of LiCoO2 and suggest a viable strategy for energy-efficient production of layered oxide cathode materials.

All-solid-state calcium-metal batteries have gained significant interest due to their advantages of low reduction potential, high energy capacity, and promising resource availability by using the Ca-metal anode. To date, hydrides have attracted attention as solid electrolytes due to their high Ca-ion conductivity, and research is being conducted to further improve their conductivity. However, most of them show low thermal stability because of complexing with volatile ligands such as NH3 and THF (tetrahydrofuran), resulting in a limited operating temperature range. Here, we aim to achieve high ionic conductivity and excellent thermal stability of Ca(BH4)2·2THF by compositing it with hexagonal boron nitride (h-BN) because h-BN is an insulating material that can form dispersed ionic conductors, and the interactions between this layered compound and the volatile ligands may functionalize the h-BN interface with fast ionic conductivity. Remarkably, the Ca(BH4)2·2THF−h-BN composites retain their pellet shape even after heating to 200 °C and exhibit fast conductivity on the order of 10−3 S cm−1 at 160 °C, whereas the pristine Ca(BH4)2·2THF material and Ca(BH4)2·2THF−mesoporous Al2O3 composites collapse after heating. Structural and nuclear magnetic resonance analyses reveal that the pelletized form suppresses the complete desorption of the THF ligands. Compositing Ca(BH4)2·2THF with h-BN is an effective strategy for simultaneously improving the ionic conductivity and high-temperature pellet durability, enabling the creation of a Ca-ion-conductive solid electrolyte.

Ruddlesden–Popper type oxysulfide Nd ₂ Ti ₂ O ₅ S ₂ shows monophasic reaction upon intercalation of Li ⁺ ions.

Manganese oxides have attracted considerable attention as sustainable functional materials owing to their earth abundance, rich redox chemistry, and structural diversity. Particle-size engineering has emerged as an effective strategy for enhancing their electrochemical and catalytic performances by increasing surface area, shortening diffusion pathways, and modifying surface structures; in particular, ultrasmall manganese oxides exhibit physicochemical properties inaccessible to bulk materials. This account summarizes recent advances in the synthesis and applications of ultrasmall manganese oxides. A low-temperature alcohol reduction process enables the preparation of highly dispersed manganese oxide nanoparticles with controlled crystal structures and exceptionally high specific surface areas. They exhibit enhanced performance in rechargeable battery cathodes, heterogeneous aerobic oxidation catalysis, and oxygen electrocatalysis, with new physicochemical properties and mechanistic insights, offering design principles for next-generation energy-storage and (electro)catalytic materials.

A simple combination of a 3D carbon architecture and electrodeposition of Zn and Mn oxide enables the concept of a 3D Zn-ion battery. A CNT network-embedded porous 3D carbon framework enables uniform electrodeposition, realizing fully three-dimensional electrodes with stable electrochemical operation.