In this study, we have prepared Sn-added SiO_x using a mechanical milling method and investigated the effect of Sn addition on the anode properties of SiO_x for lithium-ion batteries. A charge–discharge cycle test with a charge limit of 1000 mAh g⁻¹ shows that the SiO_x electrode causes a capacity fading loss by 170 cycles. Conversely, it is confirmed that the SiO_x electrodes with the addition of 1 or 3 wt% of Sn maintain a discharge capacity of up to 250 or 360 cycles, respectively, and the charge–discharge cycle life is extended depending on the amount added. Furthermore, the test is conducted by reducing the lithium-insertion amount from 1000 to 750 mAh g⁻¹ to observe the effect of Sn addition. Resultantly, the difference in cycle life is more pronounced, and the discharge capacity of the 3 wt% Sn-added SiO_x is maintained for up to 540 cycles. When the amount of Sn added is as small as 1 wt%, the lithium insertion reaction is locally concentrated because of insufficient electronic conductivity, and Li_3.75Si, with a large volume change, is formed. Resultantly, this electrode causes the disintegration of the electrode and a decrease in capacity. However, in the SiO_x electrode with 3 wt% of Sn, the reactivity of the lithium ions in the SiO₂ matrix is enhanced by the improvement in the electronic conductivity. Thus, the entire active material layer reacts easily and uniformly with the lithium ions. Resultantly, the structure is such that the stress of Si is less likely to concentrate, the damage to the electrodes is reduced, and the electrode disintegration can be suppressed, which is the reason for the enhanced cycle life.

For practical room-temperature magnesium rechargeable battery operation, utilizing the nano-sized MgMn₂O₄ spinel as cathode material is effective way to have high rate-capabilities; however, electrolyte decomposition at the cathode/electrolyte interface is inevitable. In this work, a Mg-Fe binary oxide is coated onto nano-sized MgMn₂O₄ to form stable cathode electrolyte interface (CEI). This developed cathode material suppresses the electrolyte decomposition and improves the cyclability at room temperature.

Porous La_2/3−xLi_3xTiO₃ (LLTO) for use as a Li ion conducting framework was prepared on sintered Li_0.29La_0.57TiO₃ bodies using either polyvinylpyrrolidone-assisted sol-gel or screen-printing methods. A mixture of Li and Co salts was subsequently applied to this porous material followed by heating at 700 °C for 1 h to obtain LiCoO₂ (LCO)-LLTO composite positive electrodes. These electrodes were subsequently assessed as components of all-solid-state Li secondary batteries (ASSBs). The effect of the amount of LCO loading on the electrochemical performance of these devices was evaluated, based on charge-discharge testing of ASSBs made by inserting Li_3.25Ge_0.25P_0.75S₄ between the LLTO and an In-Li alloy negative electrode. The porous LLTO permitted efficient utilization of the active material, and LCO loadings ranging from 1.1 to 6.5 mg cm⁻² were possible, with a maximum capacity of 0.65 mAh cm⁻². The electrochemical activity of 1 to 2 µm thick LCO layers prepared from molten salts on LLTO was confirmed in this work and LCO was demonstrated to function effectively as a component of a composite positive electrode. This synthesis using liquid sintering with molten salts is a promising approach to forming active electrochemical interfaces between oxides.

Attributing the peaks in the differential capacity profile (dQ/dV vs. V) to specific electrode reactions is an essential prerequisite for investigating the degradation patterns and mechanisms in Li-ion cells using the dQ/dV vs. V curve. In our previous study, we proposed an original method for attributing the peaks in the dQ/dV vs. V curve by using a three-electrode Li-ion laminate cell with a LiCoO₂ cathode, a graphite anode, and a lithium reference electrode. However, to ensure the reliability of the peak attribution results, it is necessary to verify these results using other measurement methods. Therefore, in this study, the attribution of peaks in the dQ/dV vs. V curve is confirmed by measuring and comparing the differential capacity profiles of three-electrode Li-ion laminate cells with different electrode capacity ratios.

Technology for ion conduction in Li₂S nanostructure has attracted considerable interest for achieving the intrinsic performance of Li-S batteries and for obtaining highly conductive materials. Herein, a quantitative relationship between ion transport and relaxation behavior in the Li₂S–CaS nanocomposite is revealed based on complex conductivity and electric modulus formalism. Li₂S–CaS nanocomposites prepared by high-energy ball milling show higher conductivity and activation energy for conduction than pure Li₂S. The activation energy for relaxation is lower than the activation energy for conduction in 80Li₂S·20CaS (mol%). The long-range ion transport involves high activation energy compared with the hopping of carriers at localized states in 80Li₂S·20CaS. Additionally, the dual doping of Ca and halogen reduces the activation energy for conduction and improves the conductivity of Li₂S. The findings show important insight for understanding ion transport in nanocomposites containing a Li₂S nanostructure.

To achieve stable charge-discharge operations of Li-S batteries, [Li₄Ti₅O₁₂ | sulfurized polyacrylonitrile (SPAN)] cells treated with a Li pre-doping process were prepared by two different techniques. Several different materials were studied without encountering any difficult barriers, and the obtained cells exhibited suitable charge-discharge operations with high efficiency.

Water and ethanol are conventional solvents, the anomalous physio-chemical properties of water ethanol binary solution have drawn intensive research. The unidirectional impedance evolution of ethanol-water binary solution in time domain was discovered through electrochemical impedance spectroscopy. Binary solution with different volume ratios has various self-assembly rates indicate ionization equilibrium of water molecule dominate the dynamic self-assembly process of water ethanol binary solution. Combined with molecular dynamics simulation and Raman Spectroscopy, we elucidated that this self-assembly behavior was driven by hydrogen bonding between water as proton donor and ethanol as proton receptor under water ionization, the bond length (162 pm). Different electrolytes addition in binary solution were applied to shift ionization equilibrium of water directionally, and subsequent specified self-assembly evolution was observed to prove the above hypothesis. We proposed the self-assembly mechanism of ethanol-water binary solution is relevant to ionization equilibrium of water for the first time, such perspective may provide some insight to understand the dynamic structural organization of ethanol-water and other binary solutions.

The Sabatier reaction, which converts CO₂ and H₂ into CH₄ and H₂O (methanation), is an attractive way to produce a hydrogen carrier for renewable energy and CO₂ recycling. Also, for air revitalization in space missions, water electrolysis provides not only O₂, but also H₂, which can hydrogenate metabolic CO₂ from human respiration using the Sabatier reaction, producing H₂O for O₂ regeneration with the electrolysis. In this study, we have developed a three-dimensional finite element model of a test tandem cell combining a low-temperature Sabatier reactor working at around 220 °C with a proton exchange membrane water electrolyzer at around 120 °C. The model with our developed Sabatier reaction catalyst demonstrated that appropriate heat balance between the reactor and electrolyzer establishes a CO₂ conversion above 90 % and thermal self-sustainability. An appropriate thermal insulator between the reactor and electrolyzer maintains them at predetermined temperatures. The thermal analysis also shows thermal self-sustainability for a plurality of the tandem cells, simulating a cell in a stack. Exergy loss ascribed to the entropy production rate with the temperature drop between the Sabatier reactor and electrolyzer is also evaluated.

The development of solid electrolytes is necessary for practical applications of all-solid-state Na-ion batteries. In this study, we systematically developed sulfide Na-ion conductors with central In cations, prepared by solid-state reaction and mechanochemical methods. Thermodynamically stable crystals of Na₅InS₄ and NaInS₂ were obtained by the solid-state reaction method, whereas amorphous and/or metastable phases were produced by the mechanochemical method. Two new metastable phases, Na₅InS₄ and NaInS₂, are expected to be examined in the future as end-members of sulfide Na-ion conductors with central In cations.