Molten salt-assisted encapsulation of prussian blue with carbon for high-performance potassium-ion storage

Abstract

• A molten salt-assisted method was proposed to encapsulate Prussian blue with carbon. • This method showed great prospects in large-scale production for anode materials. • The half-cell delivered K-storage capacity of 365 mAh/g at 0.1 A/g after 1000 cycles. • The full-cell delivered a capacity of 153.4 mAh/g at 0.2 A/g after 200 cycles. In this work, a unique molten salt-assisted carbothermal strategy was proposed to fabricate carbon-encapsulated Prussian blue material. In this strategy, Fe/C composite was firstly synthesized by employing molten sodium chloride as a floating template that carried iron nuclei through the holes in the carbon matrix, and thereafter ensured uniform growth and distribution of iron crystals. Then this Fe/C intermediate was transformed into carbon-encapsulated Prussian blue material via its impregnation into potassium hexacyanoferrate solution. Since this strategy was not unique to the system demonstrated, it should provide general guidance as to the fabrication of carbon-encapsulated Prussian blue analogs. The carbon-encapsulated Prussian blue material was characterized by XRD, Raman, TG, DSC, XPS, XANES, SEM, TEM and HRTEM measurements. Also, it was tested as a potential anode material for potassium-ion storage both in half and full cells through galvanostatic test, rate performance test, cyclic voltammetry and electrochemical impedance spectroscopy.