High-energy cobalt hexacyanoferrate and carbon micro-spheres aqueous sodium-ion capacitors

•Aqueous sodium-ion capacitor was assembled based on CoHCF and CMS electrodes.•The hybrid capacitor cell showed an extended operating cell voltage of 2 V.•The aqueous supercapacitor exhibited high energy density (54.4 Wh kg−1).

Sodium-based intercalation aqueous pseudocapacitive energy systems are attractive because of their obvious advantages including improved safety, low cost and environmental friendliness. Herein, an aqueous sodium-ion capacitor with the cobalt hexacyanoferrate (CoHCF) as the cathode electrode and carbon micro-spheres (CMS) as the anode electrode was fabricated, showing an extended operating voltage window (2 V), excellent capacitance behaviour, and high energy density (54.4 Wh kg−1). The present results provide meaningful clues to design new intercalation pseudocapacitor for future practical applications. And these remarkable features may pave the way to next-generation large-scale production of high performance hybrid supercapacitors performed as regulation or complementary devices.

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