This journal is © The Royal Society of Chemistry and the Chinese Chemical Society 2018 Mater. Chem. Front., 2018, 2, 1811--1821 | 1811 Cite this: Mater. Chem. Front., 2018, 2, 1811 A novel lithium-ion hybrid capacitor based on an aerogel-like MXene wrapped Fe 2 O 3 nanosphere anode and a 3D nitrogen sulphur dual-doped porous carbon cathode† Xiao Tang, a Hao Liu, a Xin Guo, a Shijian Wang, b Wenjian Wu, b Anjon Kumar Mondal, a Chengyin Wang c and Guoxiu Wang * a Lithium-ion capacitors (LICs) have emerged as promising energy storage devices with both high energy density and high power density. However, due to the mismatch of charge-storage capacity and electrode kinetics between battery-type anodes and capacitor-type cathodes, the application of lithium- ion capacitors has been limited. In this work, interconnected aerogel-like MXene wrapped Fe 2 O 3 nanospheres have been prepared and investigated as battery-type anode materials for lithium-ion capacitors. In this rationally designed hybrid electrode, the Ti 3 C 2 T x MXene matrix is capable of providing fast transport of electrons and suppressing the volume change of Fe 2 O 3 . Simultaneously, Fe 2 O 3 hollow nanospheres offer large specific capacity and prevent restacking of the MXene layers, synergizing to boost the electrochemical performances of such hybrid electrodes. Meanwhile, the three-dimensional (3-D) nitrogen and sulphur dual-doped porous carbon (NS-DPC) derived from biomass has also been fabricated as a capacitor-type cathode material for lithium-ion capacitors. Consequently, the lithium-ion capacitors can demonstrate a high energy density of 216 W h kg À1 at a power density of 400 W kg À1 and a high power density of 20 kW kg À1 at an energy density of 96.5 W h kg À1 . This work elucidates that both high energy density and power density can be achieved in hybrid lithium-ion capacitors. Introduction With the soaring demand for portable electronic devices, hybrid electric vehicles, and large-scale electricity grid storage, future energy-storage devices are required to possess features of high energy density, high power density and superior cycling stability. 1 Lithium-ion batteries (LIBs) can provide a high energy density of B150 W h kg À1 . 2 Nevertheless, intrinsically slow solid- state diffusion and volumetric strain lead to low power density. In contrast, supercapacitors (SCs) are able to deliver a high power density of 2–5 kW kg À1 and an excellent cycling performance. However, as charges are only stored on the surface of the active material, SCs usually suffer from low energy density (3–6 W h kg À1 ). Hence, the development of new energy-storage devices with features of both LIBs and SCs is highly desirable. 3,4 Recently, lithium-ion capacitors (LICs) have been proposed to bridge the gap between LIBs and SCs, and to deliver higher power density than LIBs and higher energy density than SCs. LICs have previously been constructed by an LIB-type anode with large capacity, an SC-type cathode with superior rate capability and nonaqueous Li-salt-containing electrolyte that can provide a wide working voltage window. 2–4 So far, in order to optimize the electrochemical performance of LICs, various electrode materials have been developed. 5 Many carbonaceous materials, including active carbon, 3,6 graphene, 7–9 dual-doped carbon nanofibers 10 and metal–organic-framework derived carbon, have been reported as cathodes for LICs. In addition, for LIB-type anodes, insertion-type materials (TiO 2 , 7,11–13 Nb 2 O 5 , 14 FeOOH, 15 Li 4 Ti 5 O 12 , 16–18 and graphite, 19–22 etc.), conversion-type materials (such as MnO, F-doped Fe 2 O 3 23 and Fe 3 O 4 , 8 etc.) and alloy-type materials (including Sn-encapsulated nitrogen-rich CNT, 24 Si/Cu, 25 etc.) have been utilized to realize high- performance LICs with both high energy density and power density. Fe 2 O 3 has attracted tremendous attention due to its high specific capacity, low voltage plateau, low-cost and eco-friendliness. 26–29 Nevertheless, the poor ionic/electronic conductivities cause sluggish transport of lithium ions and electrons, therefore leading to inferior a Centre for Clean Energy Technology, Faculty of Science, University of Technology Sydney, Sydney, NSW 2007, Australia. E-mail: guoxiu.wang@uts.edu.au b Department of Materials Science and Engineering, Dongguan University of Technology, Dongguan, China c College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, China † Electronic supplementary information (ESI) available: Additional characterization and electrochemical tests. See DOI: 10.1039/c8qm00232k Received 14th May 2018, Accepted 16th July 2018 DOI: 10.1039/c8qm00232k rsc.li/frontiers-materials MATERIALS CHEMISTRY FRONTIERS RESEARCH ARTICLE Published on 18 July 2018. Downloaded on 5/5/2021 1:25:44 PM. View Article Online View Journal | View Issue