Redox flow batteries (RFBs) have emerged as prime candidates for energy storage on the medium and large scales, particularly at the grid scale. The demand for versatile energy storage continues to increase as more electrical energy is generated from intermittent renewable sources. A major barrier in the way of broad deployment and deep market penetration is the use of expensive metals as the active species in the electrolytes. The use of organic redox couples in aqueous or nonaqueous electrolytes is a promising approach to reducing the overall cost in long-term, since these materials are low-cost and abundant. The performance of such redox couples can be tuned by modifying their chemical structure. In recent years, significant developments in organic redox flow batteries has taken place, with the introduction of new groups of highly soluble organic molecules, capable of providing a cell voltage and charge capacity comparable to conventional metal-based systems. This review summarises the fundamental developments and characterization of organic redox flow batteries from both the chemistry and materials perspectives. The latest advances, future challenges and opportunities for further development are discussed. Metal deposition or anode in one half-celli.e. Lithium/ organic hybrid FB Metal 'This review'

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A porous and mat-like polyaniline/sodium alginate (PANI/SA) composite with excellent electrochemical properties was polymerized in an aqueous solution with sodium sulfate as a template. Ultraviolet-visible spectra, X-ray diffraction pattern, and Fourier transform infrared spectra were employed to characterize the PANI/SA composite, indicating that the PANI/SA composite was successfully prepared. The PANI/SA nanofibers with uniform diameters from 50 to 100 nm can be observed on scanning electron microscopy. Cyclic voltammetry and galvanostatic charge/discharge tests were carried out to investigate the electrochemical properties. The PANI/SA nanostructure electrode exhibits an excellent specific capacitance as high as 2093 F g(-1), long cycle life, and fast reflect of oxidation/reduction on high current changes. The remarkable electrochemical characteristic is attributed to the nanostructured electrode materials, which generates a high electrode/electrolyte contact area and short path lengths for electronic transport and electrolyte ion. The approach is simple and can be easily extended to fabricate nanostructural composites for supercapacitor electrode materials.

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Multisequential reversible phase transitions based on molecular materials have important applications in ferroelastic materials, ferroeletric materials, switchable dielectric materials, and temperature-controlling materials. Here, we report that a new compound, [Hcpa-(18-crown-6)] + [ClO 4 ] − (1) (where Hcpa represents protonated cyclopentylamine cations) displays unusual multisequential reversible phase transitions accompanied by switchable dielectric behaviors. The stepwise synergistic disordering of Hcpa cations and ClO 4 − anions leads to the sequential reversible phase transitions and symmetry breaking. These unusual reversible phase transitions were further confirmed by the variable-temperature powder X-ray diffractometry (PXRD), thermal anomalies of differential scanning calorimetry (DSC) measurements, and abrupt dielectric anomalies in the heating and cooling processes.

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