Effect of Cations on the Electrochemical Properties of Insertion Reactions Using Prussian Blue Analogues

The increased interest in post-lithium-ion batteries (post-LIBs) in recent years has prompted the investigation of insertion materials containing various cations. The electrochemical properties of cation insertion reactions greatly influence the performance of post-LIBs. However, the relationship between these properties and the inserted cations has not been evaluated. In this study, we investigated the effect of inserted cations on the electrochemical properties of insertion reactions using Prussian blue analogues as the electrode material. The insertion reactions of mono-, di-, and trivalent cations exhibited a maximum potential difference of 200 mV, which correlated to the cation ionic radius. The rate capabilities corresponding to monovalent cations greatly depended on the ionic radius, while those of divalent and trivalent cations were similar for all tested ionic radii. For monovalent cation insertion reactions, the rate capability varied parabolically with the ionic radius, reaching a maximum at 1.3 Å. Furthermore, the rate capability decreased with increasing cation valency. The evaluation of the relationship between the electrochemical properties such as electrode potentials and rate capabilities and the cation valency and ionic radius in insertion reactions allows us to understand the electrochemical nature of this reaction and provides important information for the development of post-LIBs.