In-situ-foaming synthesis of cheese-like Fe3S4/Ti3C2Tx electrode material with both high energy and power density for Al/Zn-ion supercapacitors

Abstract

Although supercapacitor technology has been proposed as a promising new-generation energy means for its rapid charging speed and high operation safety, the shortcoming of low energy density has long been a big obstacle due to the low voltage window and storage capacity. In this study, a new kind of electrode material of Fe3S4/Ti3C2Tx has been proposed by a facile in-situ-foaming strategy through the reaction of Na2S with Fe(NO3)3. Herein, the byproducts of trace H2S and H2 gases were found to appear and expel, creating a lot of pores inside the Fe3S4/Ti3C2Tx composites with a cheese-like heterostructure. Therefore, the maximum specific capacity of Fe3S4/Ti3C2Tx-42% is measured up to 305.8 C g−1 at 2 A g−1, 3.4 times that of Fe3S4 and 5.9 times that of Ti3C2Tx. When Fe3S4/Ti3C2Tx-42% is assembled as a cathode for the Al-ion capacitors and Zn-ion capacitors, the devices both possess superior electrochemical performance. Especially for the Zn-ion capacitors, the device exhibits a high power density of 5500 W kg−1 at a maximum energy density of 61 W h kg−1 and a high stability after 10,000 cycles, showing a distinct advantage over previously reported literatures. Density functional theory (DFT) simulation and XPS analysis are used to validate the beneficial transformation mechanism of reactive sites, thus providing a novel idea for solving the poor structural stability of sulfide materials and MXene-based nanomaterials.

Keywords

• Ti3C2Tx MXene
• Fe3S4/Ti3C2Tx
• ‘Cheese’ heterostructure
• Supercapacitor