Solid-state synthesis of diminutively granular and highly crystalline manganese hexacyanoferrate for a supercapacitor electrode

Abstract

Supercapacitors are considered as promising energy storage devices due to their high power density, fast charging/discharging process and long cycle life. The synthesis of Prussian blue analogues (PBAs) by the traditional co-precipitation method faces the problems of wastewater treatment, poor material reusability and low space utilization rate. Herein, an efficient and simple solid-state synthesis protocol is used to prepare diminutively granular and highly crystalline manganese hexacyanoferrate (MnHCF). MnHCF exhibits excellent electrochemical properties with the specific capacitance of 202.8 F g⁻¹ at a current density of 1 A g⁻¹ in a neutral electrolyte. At the same time, MnHCF has good cycle stability, which could maintain 95.63% after 8000 charge–discharge cycles. The maximum energy density of the two-electrode system with MnHCF as a positive electrode and YP-50F as a negative electrode is 18.89 W h kg⁻¹ at 981.25 W kg⁻¹ and a maximum power density of 7184.73 W kg⁻¹ at 7.52 W h kg⁻¹. The outstanding electrochemical properties can be attributed to smaller particle size and higher crystallinity to achieve faster ion diffusion and greater diffusion depth. Therefore, adopting a solid-state synthesis protocol is a promising approach to achieve low-cost and large-scale production of PBAs.