Biomimetic Mesoporous Cobalt Ferrite/Carbon Nanoflake Helices for Freestanding Lithium-Ion Battery Anodes

Structural biomimicry is a fascinating concept to explore hierarchically organized nanomaterials for mechanical structures, catalysis, sensing, and energy storage applications. Here we report the fabrication of biomimetic mesoporous cobalt ferrite/carbon nanoflake materials with helical morphologies and evaluate their electrochemical properties as free-standing lithium-ion battery (LIB) anodes. Iridescent chiral nematic mesoporous chitosan films obtained from crab shells were combined with binary metallic ions to afford helical cobalt ferrite/chitosan membranes. The cobalt ferrite/chitosan composites were thermally converted to cobalt ferrite/carbon replicas with hybrid nanoflakes arranged in a twisted Bouligand-type mesoporous network. The structure of the materials was probed by electron microscopy, powder X-ray diffraction, and Raman spectroscopy. We directly used these freestanding cobalt ferrite/carbon films as binder- and additive-free LIB anodes, where they showed a first discharge capacity of 862 mAh g(-1)(at 100 mA g(-1)), which faded during subsequent charge-discharge cycles. Our work demonstrates a new potential use of chiroptical chitosan membranes to develop energy storage materials, a process that may be extended to other metal-oxide based components.