Durable Supercapattery Film with Dual-Branched Dense Hexagonal Fe(II)-Based Coordination Nanosheets for Flexible Power Sources

A durable supercapattery film was fabricated by a combination of dual-branched dense hexagonal Fe(II)-based coordinated nanosheets (polyFe-2D) and Fe-hexacyanoferrate. The complementary redox properties of the two materials led to a reversible push–pull phenomenon in the device. The fabricated device served as a supercapattery with high supercapacitor properties as well as high battery properties. Due to the high density of Fe(II) ions in the dense hexagonal structure of polyFe-2D, the maximum volumetric energy density reached 13.8 mWh/cm3, which is higher than those of thin-film lithium batteries. The power density (15.1 W/cm3) was also comparable to the conventional supercapacitors. The stable electrochemical redox between Fe(II)/(III) in polyFe-2D realized more than 10 000 cycles of charge/discharge in the device. The durable and flexible supercapattery is attractive as a wearable power source.