Novel iron oxyhydroxide lepidocrocite nanosheet as ultrahigh power density anode material for asymmetric supercapacitors.
A simple one-step electroplating route is proposed for the synthesis of novel iron oxyhydroxide lepidocrocite (γ-FeOOH) nanosheet anodes with distinct layered channels, and the microstructural influence on the pseudocapacitive performance of the obtained γ-FeOOH nanosheets is investigated via in situ X-ray absorption spectroscopy (XAS) and electrochemical measurement. The in situ XAS results regarding charge storage mechanisms of electrodeposited γ-FeOOH nanosheets show that a Li(+) can reversibly insert/desert into/from the 2D channels between the [FeO6 ] octahedral subunits depending on the applied potential. This process charge compensates the Fe(2+) /Fe(3+) redox transition upon charging-discharging and thus contributes to an ideal pseudocapacitive behavior of the γ-FeOOH electrode. Electrochemical results indicate that the γ-FeOOH nanosheet shows the outstanding pseudocapacitive performance, which achieves the extraordinary power density of 9000 W kg(-1) with good rate performance. Most importantly, the asymmetric supercapacitors with excellent electrochemical performance are further realized by using 2D MnO2 and γ-FeOOH nanosheets as cathode and anode materials, respectively. The obtained device can be cycled reversibly at a maximum cell voltage of 1.85 V in a mild aqueous electrolyte, further delivering a maximum power density of 16 000 W kg(-1) at an energy density of 37.4 Wh kg(-1).
Karlsruhe Institute of Technology (KIT), Institut für Anorganische Chemie, Engesserstraße 15, D-76131, Karlsruhe, Germany.
Ying-Chu
YC
Chen
Yan-Gu
YG
Lin
Yu-Kuei
YK
Hsu
Shi-Chern
SC
Yen
Kuei-Hsien
KH
Chen
Li-Chyong
LC
Chen
anodes; asymmetry; iron oxides; nanostructures; supercapacitors