The Mn-based Prussian blue analogues (MHCF) have attracted much attention as the promising cathode materials for sodium-ion batteries in recent years due to the large theoretical specific capacity of 170 mA h g−1 and high redox potential of 3.5 V. However, the as-prepared MHCF synthesized using the conventional coprecipitation method always obtain large amounts of Fe(CN)6 vacancies and interstitial and coordination water, which result in low alkaline ion content and poor electrochemical performance. In this study, the sodium citrate assisted coprecipitation method was adopted to prepare the high-quality K-based MHCF (KMHCF) by adjusting the concentration of raw materials and aging time. The characterizations of the as-prepared samples showed that similar crystal structure but different morphologies as well as electrochemical behaviours were obtained due to the variations of preparation conditions as shown in Fig. 1. Among them, the KMHCF2_24h exhibited the best electrochemical performance with large initial specific capacity of 140.3 mA h g−1 and high capacity retention of 87.95% after 50 cycles at 20 mA g-1. This should be ascribed to the regular cubic morphology of particles with the optimal size (1 µm) and aging time (24 h).

Particle size and aging time tuned potassium manganese hexacyanoferrate as a superior cathode for sodium-ion batteries

ACS Fall 2021

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