ИСТИНА

The new horizons for the development of more efficient metal-ion battery systems are generally associated with the introduction of new metal-ion technologies, such as sodium-ion and potassium-ion batteries, or enhancing the energy characteristics of traditional lithium-ion batteries by employing new high voltage and high capacity materials in new stable electrolyte systems. Since the emergence of lithium-ion battery technology the successes in this area were based on the unique properties of ethylene carbonate (EC) cosolvent, which allows for the creation of lithium-ion permeable but electronically insulating layered interface at the anode, thus expanding the potential window of the solvent and, correspondingly, increasing the voltage of the battery. As well as in case of reductive EC decomposition, oxidative decomposition of the solvent takes place at the cathode material surface, providing, however, little stabilization of the cathode/electrolyte interface, if no specifically designed additives are employed. The attempts to switch to new electrolyte systems and new metal-ion chemistries inevitably call for the investigation of the interfaces formed in new battery systems. Superconcentrated electrolytes in both aqueous and nonaqueous implementation are considered as a promising new class of electrolyte solutions for high-voltage lithium ion batteries. Using extremely high concentrations of lithium salts in an organic or aqueous solvent was demonstrated to result in the kinetic suppression of both solvent oxidation and reduction, thus allowing for the application of higher voltage cathode materials and lower voltage anode materials. This intriguing approach, however, currently disregards the inevitable changes in the electrode/electrolyte interface structure and the corresponding rate limitations in the battery performance, which are not necessarily plausible. In this talk the thermodynamic and kinetic aspects of intercalation processes in highly concentrated aqueous and EC-based electrolytes are discussed with regard to the associated bottlenecks in fast charge transfer. Yet another problem related to the electrode/electrolyte interface studies arises when sodium and potassium cathode materials are considered in both conventional and new electrolyte solutions. Even given the absence of significant structural changes upon the insertion of larger sodium and potassium ions into the intercalating host matrix, the kinetics of the reaction is strongly affected by the electrode/electrolyte interface structure due to the dependence of the energetics of reactant’s approach on the cation’s size. Herein, we discus kinetic patterns of alkali metal ion intercalation into AVPO4F matrix in different organic electrolytes, with a special emphasis on the influence of barrier properties of interfacial layers on the reaction rates and its dependence on the cation’s radius.