Commercially available Prussian blue get energetic in aqueous K-ion batteries

Abstract

High-safety and low-cost aqueous rechargeable batteries are competitive candidates in the energy storage field. Here, we report the outstanding performance of commercial Prussian blue (Fe4III[FeII(CN)6]3·3.4H2O) in aqueous K-ion batteries. In the half cells, the charge/discharge curves show the quite flat voltage plateaus with ultra-small electrochemical polarization (below 0.1 V). At 1 C, the specific capacity can reach ~80 mAh g−1 with 82.4% retention over 500 cycles. At 10 C, the batteries still exhibit excellent performance of 80.8% capacity retention over 1000 cycles. And they also show the high rate capability. Moreover, when used as bipolar electrodes, the fabricated symmetric aqueous full cells deliver good cycling stability. In addition, we have established synergic relationships between the crystal structure, electronic states, storage kinetics and electrochemical performance to reveal K-ion insertion/extraction mechanisms. Form a practical perspective, the application of commercial Prussian blue to the high-safety aqueous batteries is a desirable choice for grid-scale energy storage.