PNNL

Abstract

Prussian blue analogues (PBAs) cathodes can host diverse monovalent and multivalent metal ions due to their tunable structure. However, their electrochemical performance suffers from poor cycle life associated with chemo-mechanical instabilities. This study investigates driving forces behind chemo-mechanical instabilities in Ni- and Mn-based PBAs cathodes for K-ion batteries by combining electrochemical analysis, digital image correlation, diffractometry, and spectroscopy techniques. Capacity retention in Ni-based PBA is 96% whereas it is 91.5% for Mn-based PBA after 100 charge-discharge cycles. Both cathodes undergo similar nominal electrochemical strains in each cycle. However, thicker organic compounds were detected in the cycled Mn-based PBA, whereas a thin layer of inorganic compounds was found in the cycled Ni-based PBA. Faster capacity fade in Mn-based PBA, compared to Ni-based ones, is attributed to the severe interfacial instabilities, rather than mechanical deformations. Understanding the driving forces behind instabilities provides a guideline to develop material-based strategies for better electrochemical performance.