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 h g⁻¹ at 0.1 A g⁻¹ and 587.2 mA h g⁻¹ at 2 A g⁻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.