Diffusion of charge-carrying ions in tunnel manganese oxides: effect of 1D tunnel size and ionic content

摘要

The low cost, environmental friendliness, and high electrochemical activity of manganese oxides make them attractive candidates for electrodes in intercalation-based battery systems. Tunnel manganese oxides are a subset of this materials family built from corner and edge sharing MnO_6 octahedra arranged around stabilizing cations and water molecules to form tunnels of various size and shape. Here, we synthesize three tunnel manganese oxides with different 1D diffusion channel size and ionic content. The apparent Li~+ ion and Na~+ ion diffusion coefficients are calculated from the galvanostatic intermittent titration technique to understand the effect of tunnel size and ionic content on diffusion of charge-carrying ions through the one-dimensional structural tunnels. In LIBs, the material with the largest tunnels demonstrated the highest Li~+ ion diffusion coefficient, while in SIBs the material stabilized by Na~+ ions (the same as the charge-carrying ions) demonstrated the highest rate performance, revealing the significance of ionic content in the structural tunnels. These results highlight the importance of the relationship between tunnel size and charge-carrying ion size and provide insight into the design and selection of tunnel manganese oxides for improved diffusion of charge-carrying species.