The Editorial Board outlines the history of publication by the Electrochemical Society of Japan as it celebrates its 90th anniversary. The history of the journal is told by the Society’s strong interest in publishing and its international development in line with current trends. The growing presence of the journal is described. This issue will also include the Comprehensive Papers by the winners of the ECSJ awards. The rationale for these awards will also be explained.
Research and development of Lithium Ion Battery (LIB) have been extensively performed based on material science and cell technology. In order to accelerate the development of LIB, a multi-scale researches have to be conducted under one roof. Here, several researches from nm scale to m scale on LIB were introduced to discuss an importance of multi-scale research. Then, the new platform for LIB development was proposed based on our several researches. (1) Interfacial analysis between cathode and electrolyte in LIB by using in-situ Fourier Transform Infrared method, (2) Preparation of LiFePO4 (LFP) with carbon coating, (3) Interfacial analysis on lithium metal anode for solid electrolyte interphase (SEI), (4) Preparation of 3 dimensionally ordered macroporous separator and its application to lithium metal battery, (5) Single particle measurement for evaluation of composite electrodes, (6) Failure mode analysis of LFP/Graphite cell.
Boron-doped diamond (BDD) electrodes are next generation electrode materials and their electrochemical applications have been actively developed in recent years. They are expected to be useful electrode materials for improving the environment and for bio-medical applications. Here, examples of practical applications as electrochemical sensors, the development of in vivo real time measurements, and electrochemical organic synthesis using BDD electrodes are briefly introduced. In the second part, our recent work on the production of useful chemicals by means of the electrochemical reduction of CO2 using BDD electrodes is described. The work has attracted particular attention for its potential contribution to carbon neutrality and carbon recycling.
Li salts and polar solvents form solvates, and certain solvates have low melting temperatures and remain in a liquid state at room temperature. Liquid-state solvates exhibit ionic conductivity and can be used as electrolytes in lithium batteries. The author and co-workers have systematically studied the interactions of Li+ ions with solvents and anions, Li+-coordination structures, thermal properties, transport properties, and electrochemical properties in molten-solvate electrolytes. In molten solvates, almost all solvent molecules are coordinated to Li+ ions, and uncoordinated (free) solvents are rare. Additionally, anions are involved in the coordination of the Li+ ions. The molten solvate electrolytes show non-flammability and negligible vapor pressure at room temperature because of the extremely low concentration (activity) of the free solvent, which can improve the thermal stability of Li batteries. The low activity of the free solvent results in a wide electrochemical window of the molten-solvate electrolytes, thereby suppressing undesired side reactions in Li batteries. The activity of the free solvent in the electrolytes significantly affects the electrochemical reaction processes, such as the reduction reaction of sulfur (S8) in a Li–S battery and the oxygen reduction reaction (ORR) in a Li–air battery. The solubility of the reaction intermediates of the S8 cathode and the ORR decreases with the decrease in solvent activity, which enables the highly efficient charge–discharge of Li–S and Li–air batteries. In molten solvates, Li+ ions diffuse and migrate by exchanging ligands (solvents and anions). Certain molten-solvate electrolytes show high Li+ ion transference numbers over 0.5, and these high transference numbers are useful in mitigating the concentration overpotential during the charging and discharging of Li batteries at high current densities.
The supporting electrolyte is an essential component of electrochemical reactions. Although there have been many reports on the influence of the type of electrolyte and its concentration on reaction efficiency in electrosynthesis, very few reports have systematically discussed the reasons for such effect. In several reaction systems, we have found that the coordination of anions from the supporting electrolyte to cationic organic species generated in electrochemical oxidation dramatically changes the reaction efficiency. In this comprehensive paper, we review these case studies, generalize the findings learned from them, and provide guidelines for strategic electrolyte design.
Renewable energy resources and rechargeable batteries are key to establishing a carbon-neutral society. Lithium-ion batteries (LIBs) have been widely used in portable electronic devices for the past 30 years. However, the further spread of large-scale batteries is essential in the household and industrial sectors, which drives the research and development of technologies beyond LIBs. Since ionic liquids are safe and confer unique physicochemical properties, several next-generation batteries utilizing ionic liquid electrolytes have been researched. Sodium-ion and potassium-ion batteries show promise in overcoming the potential problems of LIBs related to the uneven distribution of lithium and cobalt resources. Fluoride-shuttle batteries deliver significantly higher theoretical energy densities compared to current LIBs. Nevertheless, many issues remain unresolved for the practical application of these batteries. This comprehensive paper provides several research topics on next-generation rechargeable batteries utilizing ionic liquids and various charge carriers, unveiling their novelty, the issues to be solved, and future research directions.
We have established a method for measuring the zeta potential generated at the interface between a nonaqueous electrolyte solution utilized in LiClO4/propylene carbonate (PC) electrolyte and lithium cobalt oxide (LiCoO2) by the streaming potential method. Since the surface potential of the metal oxide dispersed in the aprotic nonaqueous solvent contains only a very small amount of water-based potential-determining ions such as H+ and OH−, the potential is determined by the adsorption of the solvated electrolyte itself. Unlike aqueous systems with potential-determining ions that exhibit specific adsorption, it took a very long time until the equilibrium state of the ion distribution near the solid surface was reached and the potential stabilized, with a time constant that amounted to about 5 minutes. Therefore, a detailed analysis of the change over time of the potential after the pressure setting showed that the predictive potential showed a change over time with almost a single relaxation having certain time constant. The measurement time of the streaming potential was corresponded to about the time constant, and the resulting zeta potential showed an anomalous concentration dependence as a maximum around 1.0 mol L−1 PC and a minimum at 1.5 mol L−1 PC for the concentration of each solution.
Steady-state experiments are often conducted to understand complicated cases in chemistry, since the kinetics does not have a time valuable and allows simple modeling of the reactions. The reciprocal of the overall rate of sequential steady-state reactions is often given in the reciprocal sum formula: sum of the reciprocals of the rates of the hypothetical rate-limiting processes at the individual stages. In this paper, the reciprocal sum relationship is generalized for sequential multi-step steady-state reactions, and the importance and usefulness of the concept is shown by applying it to describe several typical steady-state systems in enzyme reactions and voltammetry using rotating disk- and ultramicro-electrodes.
Rotating disk voltammograms of electrocatalytic reactions were often analyzed on a model of the totally irreversible reaction. The problem with the conventional method is pointed out, and the validity of an analysis method on a model of the electrocatalytic reaction is demonstrated for oxygen-reduction reaction (ORR) as an example. Rotating disk voltammograms of ORRs sometimes show gradual change in the limiting current region called residual slope. The phenomenon has been explained on a random distribution model in which the catalytic sites communicate in long-range electron transfer with the electronic conductors that locate at distances (z), and are uniformly distributed with respect to z. Observed data of an ORR were well reproduced by non-linear least squares analysis on the random distribution model. The result of the analysis is briefly discussed.