Optimization and Investigation of a Sustainable K2Mn[Fe(CN)6]||Graphite Potassium-Ion Battery Full Cell

Abstract

Many positive–negative electrode configurations have been demonstrated for potassium-ion battery (KIB) full cells, but the pairing of the Prussian blue analogue K2Mn[Fe(CN)6] (KMF) and graphite has the most promise for future development. However, research on this full cell remains highly fundamental, with little understanding of the behavior of KMF at high areal loadings, low amounts of conductive carbon, and high calendering density, along with how the electrochemical performance varies with N/P ratio and cutoff voltage. Therefore, to address this research deficiency, we report the optimization of a K2Mn[Fe(CN)6]||graphite full cell through investigating the KMF positive-electrode composition, particle size, areal loading, and porosity, yielding an electrode with 93 wt % active material, an areal loading of >20 mg cm–2, and a reversible areal capacity of >2 mAh cm–2. The effect of calendering is also investigated, delivering a maximum energy density of 528 Wh L–1 at 47% porosity. The resulting full cell, using uncycled graphite, is then optimized in terms of N/P ratio and cycling voltage, achieving an initial coulombic efficiency (ICE) of 83.3% and a reversible capacity of >2.2 mAh cm–2 and demonstrates the viability of the K2Mn[Fe(CN)6]||graphite configuration for KIB full cells.