Structural complexity in Prussian blue analogues

TL;DR

This paper reviews various types of structural complexity in Prussian blue analogues, discussing their effects on material properties and how they can be controlled to improve performance in applications like batteries.

Contribution

It provides a comprehensive survey of structural complexities in PBAs and explores strategies to manipulate these features for enhanced material functionality.

Findings

Identification of key structural distortions affecting properties

Analysis of how composition influences complexity

Guidelines for optimizing PBA performance

Abstract

We survey the most important kinds of structural complexity in Prussian blue analogues, their implications for materials function, and how they might be controlled through judicious choice of composition. We focus on six particular aspects: octahedral tilts, A-site `slides', Jahn--Teller distortions, A-site species and occupancy, hexacyanometallate vacancies, and framework hydration. The promising K-ion cathode material K$_x$Mn[Fe(CN)$_6$]$_y$ serves as a recurrent example that illustrates many of these different types of complexity. Our article concludes with a discussion of how the interplay of various distortion mechanisms might be exploited to optimise the performance of this and other related systems, so as to aid in the design of next-generation PBA materials.