Synthesis And Electrochemical Properties Of Iron (Oxyhydr) Oxides On Carbon Cloth For Chemical Energy Storage

The development of lightweight, thin, and flexible electronics is an emerging and promising technology for the next generation of optoelectronic devices, which have wide applications in rollup displays, smart electronics, memory chips and wearable devices. Among these, Li-ion batteries (LIBs) have triggered a gold rush because of their excellent advantages. Another candidate for the next generation energy storage devices is supercapacitors (SCs), which demonstrate outstanding power performance, superior reversibility and more safety. Iron (oxyhydr)oxides (Fe2O3, FeOOH) have the advantages of low cost, environmental benign and natural abundance. However, the iron (oxyhydr)oxides -based electrodes can not satisfy the demand for applications, due to their poor conductivity arising from kinetic limitations and poor cycling stability originated from large volume expansion during during cycling.To solve the above problems, constructing nano-scale structure, building three-dimensional (3D) integrated electrodes or adding conductive phase such as conducting polymer and carbon materials seems to be effective approaches. Therefore, our work foused on the synthesis the integrated electrode of iron (oxyhydr) oxides based on carbon cloth. The main results are as follows:(1) We report a facile hydrothermal route to synthesis self-organized bunched β-FeOOH nanorod arrays directly grown on carbon cloth (β-FeOOH/CC NRAs). Interestingly, the single nanorod was assembled by numerous small nanowires. A possible growth mechanism for this unique structure was proposed.(2) Owning to the essential crystal structure of β-FeOOH (body-centered cubic), porous morphology, high surface area and direct growth on current collector, the prepared β-FeOOH/CC NRAs manifest a very high reversible capacity of ≈2840 mAh g-1 (2.21 mAh cm-2), remarkable rate capability 568 mAh g-1 (0.43 mAh cm-2) at 10 C, stable cycling performance and greater mechanical strength.(3) We present a facile method for fabricating hematite nanocrystals/carbon cloth composite. The hierarchical manganite is chosen as the sacrificial precursor that does not contribute to the component of final iron oxide but can be in situ dissolved by the acid produced from the Fe3+ hydrolysis. This method effectively enhances the specific surface area and conductivity of Fe2O3 by attaching nanocrystals (around 5 nm) firmly on the surface of carbon fibers.(4) The obtained Fe2O3/CC can be directly used as binder-free electrode for supercapacitor, further boosting its energy storage capacity. Interestingly, the composite electrodes exhibit synergistic electrochemical capacitance (electrochemical double-layer capacitance and pseudo-capacitance). It manifests a very high areal capacitance (1.66 F cm-2 at 2 mA cm-2) and excellent cycling performance, which is among the best reported in the literature. Importantly, the as fabricated solid-state flexible symmetric supercapacitors show a maximum energy density of 8.74 mWh cm-3.