A reference electrode equipped with ionic liquid salt bridge consisting of tributyl(2-methoxyethyl)phosphonium bis(pentafluoroethanesulfonyl)amide has been employed for potentiometric precipitation titration of chloride with silver ions in water at 25 °C. A model for the titration curve was regressed to experimental curves, taking into account the change in the activity coefficients of relevant ionic species in the course of the titration, to obtain the least square estimates of two adjustable parameters in the model, the solubility product (K_sp) and the analyte concentration. The least-square estimate of K_sp, (1.840 ± 0.060) × 10⁻¹⁰, i.e., pK_sp = 9.736 ± 0.014, is in good agreement with literature data, but with higher precision.

Our group has investigated the properties of lithium-ion battery anodes fabricated using Sn/SiO_x (SiO_x is a mixed phase of Si clusters and amorphous SiO₂ matrix). The addition of Sn improves the conductivity of the SiO₂ matrix, while the formation of the Li⁺-conductive Li₂Si₂O₅ phase in the SiO₂ matrix improves Si utilization. The charge–discharge cycle life is also extended. In this study, Sn-doped SiO_x has been used to fabricate the anode of a sodium-ion battery, and its charge–discharge properties are evaluated. The addition of 3 wt% Sn to SiO_x improves the cycle property, as revealed by charge–discharge tests. X-ray diffraction analysis confirmed that the Na⁺-conductive Na₂Si₂O₅ phase is formed during the charging and discharging processes. These results indicate that adding Sn improves the electronic conductivity of SiO₂, and Na₂Si₂O₅ facilitated the movement of Na in the SiO₂ matrix. Thus, the utilization of Si is enhanced, and a high discharge capacity is achieved.

Electrochemical intercalation behaviors of alkali metals into graphite have been vigorously studied in academic and industrial fields, whereas their mechanisms are still unclarified. In this study, we report a novel rubidium-ion battery utilizing an ionic liquid electrolyte and natural graphite as the negative electrode material operating at room temperature. The electrochemical phase evolution behavior of rubidium–graphite intercalation compounds was elucidated using X-ray diffraction. The graphite negative electrode exhibited an initial discharge capacity of 216 mAh g⁻¹ at 0.05 C rate, and retained its capacities of around 180 mAh g⁻¹ even at 0.5 C rate for 50 cycles.

Hard carbon (HC) is receiving widespread attention as a negative electrode material for sodium secondary batteries. In this study, spherical HC with three different diameters (1 µm, 1.5 µm, and 5 µm) are investigated using ionic liquid (IL) and organic electrolytes. The HC with a diameter of 5 µm demonstrated the best performance with IL at 90 °C (capacities of 327 mAh g⁻¹ at 20 mA g⁻¹ and 77 mAh g⁻¹ at 2000 mA g⁻¹ and initial Coulombic efficiency of 78.9 %). The HCs showed stable cycling in ILs as compared to the organic electrolytes in the first few cycles.