정용화 교수

Substantial interest in sodium resources that are inexpensive and abundant in the earth has guided intense research on Na-based electrode materials. We report a facile synthetic strategy to improve the rate performance of Na-based electrode materials in sodium-ion batteries. Na3V2(PO4)3 (NVP) is one of the most promising cathode materials with a NASICON structure, and it has been synthesized on a graphene sheet surface using a simple method that combines sol–gel and solid-state reaction. The NVP

Sodium layered oxides with mixed transition metals have received significant attention as positive electrode candidates for sodium‐ion batteries because of their high reversible capacity. The phase transformations of layered compounds during electrochemical reactions are a pivotal feature for understanding the relationship between layered structures and electrochemical properties. A combination of in situ diffraction and ex situ X‐ray absorption spectroscopy reveals the phase transition mechanis

An iron-based pyrophosphate compound, Na2FeP2O7, is investigated as a positive electrode material for aqueous sodium-ion batteries for the first time. The high rate capability and good cyclability of this material in aqueous electrolytes are advantageous for low-cost and safe battery systems.

Layered transition metal oxides, in particular P2-type ones, are considered as promising cathode materials for sodium-ion batteries on account of their high specific capacity and rate capability. Nevertheless, conventional layered compounds involve detrimental phase transformation throughout repeated cycles, which results in electrochemical performance degradation. Therefore, finding structurally stable layered compounds, featuring minimal phase transition has been a key theme of the sodium-ion

Abstract Manganese hexacyanomanganates have attracted significant attention as promising cathode materials for sodium‐ion batteries owing to the high theoretical capacity and low cost of Mn resources. Because of the strong Jahn–Teller effect, causing unstable local phase transition and distortion, the redox reactions of the high‐spin state of Mn(III) are considered to be a conundrum. Herein, it is reported that the charge‐redistribution mechanism of low‐spin Mn III + high‐spin Mn III → low‐spin

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have received great attentions because of diverse quantum electronic states such as topological insulating (TI), Weyl semimetallic (WSM) and superconducting states. Recently, the superconducting states emerged in pressurized semimetallic TMDs such as MoTe2 and WTe2 have become one of the central issues due to their predicted WSM states. However, the difficulty in synthetic control of chalcogen vacancies and the ambiguous magneto transp

Li substitution at the alkali site of an O3-type structure improved performance by lowering the energy barrier of Na intercalation and stabilizing the layered structure.

This paper represents the first description of the electrochemical sodium ion intercalation properties of Na2.7Ru4O9 in both nonaqueous and aqueous electrolytes. Na2.7Ru4O9 was synthesized at 700–850°C by solid-state reaction under Ar flow. It has single, double and triple chains of edge-sharing RuO6 octahedra and one-dimensional tunnels between them parallel to the b-axis, accommodating three different sites of Na1, Na2 and Na3. In an organic electrolyte (1 M NaClO4 in PC), Na2.7Ru4O9 shows thr