Sodium Ion Capacitor Using Pseudocapacitive Layered Ferric Vanadate Nanosheets Cathode

Summary

Sodium ion capacitors (SICs) are designed to deliver both high energy and power densities at low cost. Electric double-layer capacitive cathodes are typically used in these devices, but they lead to very limited capacity. Herein, we apply a pseudocapacitive layered ferric vanadate (Fe-V-O) as cathode to construct non-aqueous SICs with both high energy and power densities. The Fe-V-O nanosheets cathode displays remarkable rate capability and cycling stability. The pseudocapacitive sodium storage mechanism of Fe-V-O, with over 83% of total capacity from capacitive contribution, is confirmed by kinetics analysis and ex situ characterizations. The capacitive-adsorption mechanism of hard carbon (HC) anode is demonstrated, and it delivers excellent rate capability. Based on as-synthesized materials, the assembled HC//Fe-V-O SIC delivers a maximum energy density of 194 Wh kg ⁻¹ and power density of 3,942 W kg ⁻¹. Our work highlights the advantages of pseudocapacitive cathodes for achieving both high energy and power densities in sodium storage devices.

Graphical Abstract

Highlights

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  Pseudocapacitive cathode is applied to construct a high-energy sodium ion capacitor

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  Layered ferric vanadate cathode displays pseudocapacitive sodium storage behavior

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  Ferric vanadate cathode delivers remarkable rate capability and cycling stability

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  Hard carbon anode exhibits capacitive adsorption mechanism and high-rate performance

Abstract

Electrochemical Energy Storage; Energy Materials; Nanoelectrochemistry