Biopolymer-assisted synthesis of 3D interconnected Fe3O4@carbon core@shell as anode for asymmetric lithium ion capacitors

Lithium ion capacitor (LIC) has been regarded as a promising device to combine the merits of high-energy lithium ion battery and high-power supercapacitor. The key challenge in developing high performance LIC is to achieve synergy between the high capacity of battery anode and the fast non-Faradaic reaction rate of capacitive cathode without compromising energy density. Here, we report 3D interconnected Fe3O4@C core@shell nanocomposites with enhanced lithium storage reaction kinetics as an anode material of LIC. Chitosan, a renewable biopolymer with rich functional groups, has been utilized as both structural directing agent and carbon precursor to assist the synthesis of Fe3O4 @C composites, which have small particle size and an in situ formed carbon coating layer. The carbon coating can not only dramatically improve the electronic conductivity, but also buffer the large volume expansion/ contraction of Fe3O4 during lithiation/delithiation. The Fe3O4 @C composites show a reversible capacity of 1116.1 mA hg(-1) at 0.1 Ag-1 and 587.2 mA hg(-1) at 2 Ag-1, as well as stable capacity retention over cycling. Furthermore, the hybrid device based on Fe3O4@C composites achieves a specific energy of 110.1 Wh kg(-1) at a specific power of 250 W kg(-1), demonstrating promising application of the reported hybrid systems. (C) 2018 Elsevier Ltd. All rights reserved.