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

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. A solid-state synthesis protocol enables the fabrication of diminutively granular and highly crystalline manganese hexacyanoferrate in a limited reaction region without additives and solvent.