Facile synthesis of FeVO@C materials as high-performance composite cathode for lithium-ion hybrid capacitor

Abstract

Abstract Due to its excellent power performance and high cycling stability, activated carbon is widely used as the cathode in Li-ion hybrid capacitors. However, it remains challenging to improve its energy density. In this article, we report a composite cathode material composed of iron vanadate (Fe5V15O39(OH)9·9H2O) (FeVO) particles and commercial activated carbon (YP50D), synthesized by a facile wet-chemical approach. The successful combination of the two materials results in the simultaneous action of electric-double-layer capacitive effects and a diffusion-controlled faradaic process during the charging-discharging cycles, enabling improved energy. LIC devices are fabricated using 10-FeVO@C as the cathode and pre-lithiated artificial graphite as the anode. Compared to pure YP50D, the 10-FeVO@C//AG LIC device delivers a much higher energy density of 117.9 W h kg−1 at a power density of 237.6 W kg−1 and retains 27.3 W h kg−1 at 20008.7 W kg−1. A reasonable cycling stability is achieved as well, with a capacitance retention of 70.7% after 1000 cycles. This work proves the great potential of composite cathodes, with the combination of a battery material and activated carbon, for high-performance lithium-ion hybrid capacitors.