Smart configuration of cobalt hexacyanoferrate assembled on carbon fiber cloths for fast aqueous flexible sodium ion pseudocapacitor.

Aqueous rechargeable batteries (ARBs) have the advantages of low cost, high safety and sustainable environmental friendliness. However, the key challenge for ARBs is the narrow electrochemical stability window of the water, undoubtedly leading to the low output voltage, the underachieved capacity and a low energy density. Prussian blues and their analogues have attracted great research interest for energy storage due to the advantages of facile synthesis, versatile categories and tunable three dimensional frameworks. Herein a flexible integrated potassium cobalt hexacyano ferrates (Co-HCF) on carbon fiber clothes (CFCs) were designed through a feasible route combining the controllable electrochemical deposition and the efficient co-precipitation process. The Co-HCF@CFCs demonstrate an excellent sodium ion storage with a high reversible capacity of 91 mAh g at 1 A g and 55 mAh g at 10 A g in aqueous electrolytes. The long cycling stability at the high current demonstrate the excellent structure stability of the Co-HCF@CFCs. Analysis on the rate Cyclic voltammograms (CV) profiles reveal the fast electrochemical kinetics with the capacitive controlled process, while galvanostatic intermittent titration technique (GITT) tests fast diffusion coefficient related with the sodium ions intercalation/deintercalation in the Co-HCF@CFCs. In addition, the flexible Co-CHF@CFCs also demonstrate excellent performance for quasi-solid-state ARBs even at the high bending angles. The high quality Co-HCF@CFCs with advantage of high rate capability and excellent reversible capacity make them a promising candidate for high performance ARBs.