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The transition towards electric vehicles and more sustainable transportation is dependent on lithium-ion battery (LIB) performance. Ni-rich layered transition metal oxides, such as NMC811 (LiNi0.8Mn0.1Co0.1O2), are promising cathode candidates for...

Fe 3 O 4 spherulites on carbon nanofibres (CNF) to form novel necklace structures have been synthesised using a facile and scalable hydrothermal method, and their morphology and structure have been characterized using a range of electron microscopy and other techniques.The formation mechanism for the necklace structure has been proposed. The Fe 3 O 4 /CNF necklaces were sprayed onto large area current collectors to form electrodes with no binder and then investigated for their potential in supercapacitor and Li-ion battery applications.Supercapacitor electrodes in an aqueous KOH electrolyte delivered a high capacitance of 225 F g -1 at 1 A g -1 and Li-ion battery electrodes delivered a reversible capacity of over 900 mAh g -1 at 0.05 C, and there was good cycling stability and rate capability in both configurations. When compared with the reduced performance of mixtures of the same materials without the necklace morphology, the enhanced performance can be ascribed to the robust, high mechanical stability and open scaffold structure in the necklace electrode that provides high ion mobility, while the percolating CNFs ensure low resistance electrical connection pathways to every electroactive Fe 3 O 4 spherulite to maximize storage behavior. IntroductionConcerns surrounding increasing environmental pollution and effects on climate change mandate increasing use of renewable and sustainable energy conversion technologies, which can be made more attractive by the use of efficient and safe electrical storage. Amongst the various energy conversion and storage technologies, supercapacitors and Li-ion batteries (LIBs) make use of electrochemical reactions to store electrical charge and have secured wide applications in portable electronics and electric vehicles. [1][2][3][4][5][6] Supercapacitors, also called electrochemical capacitors, are energy storage devices that have high power density, long cycle life, high cycling efficiency, and operate by storing electrical charge through ion adsorption/desorption at an electrode/electrolyte interface and/or through fast surface redox reactions. 1,7,8 The electrodes in a supercapacitor may be electrochemically identical because adsorption/desorption reactions, and the electric double layer that is formed, do not necessarily involve any physical changes. In contrast, LIBs have much higher energy density and store electrical energy through lithiation/delithiation reactions at electrochemically dissimilar anodes and cathodes. 4,9 Despite the relative maturity of supercapacitors and LIBs, the growing market for portable electronics and electric vehicles and in particular the desire for the decarbonisation of electricity supplies provides new opportunities for these devices. While further improvements in power and energy densities of supercapacitor and LIBs system will always be valuable, there 13 pseudo-capacitive behaviour. A pair of very broad peaks was located at approximately -0.77 V resulting from the redox reaction of oxygen-containing functional groups on the CNFs.Additionall...