In recent years, the key principles of the electric power industry have radically changed and the number of studies on the development of devices for electrical energy storage in a different form such as mechanical or chemical energy has rapidly increased. This review gives a brief description of these devices. The attention is focused on redox flow batteries (RFBs), a promising type of energy storage devices capable of efficiently operating in distributed power grids, in order to eliminate the imbalance between the time-varying electricity production by ‘unconventional sources’ and electricity consumption. At the design level, RFBs combine the principles of fuel cells and chemical energy sources with solid electroactive materials: transitions between electrical and chemical forms of energy in these devices occur upon oxidation and reduction of redox-active electrolytes, which are stored in separate tanks and pumped into the electrode compartments of the membrane electrode assembly (MEA) separated by a semi-permeable membrane. This approach ensures an important advantage of these devices over other types of chemical energy sources, that is, the possibility of independent scaling of the energy storage capacity and power characteristics of the system. This review provides a systematic description of the main types of RFBs and analysis of their fundamental benefits and drawbacks, which determine the prospects for practical applications of RFBs. The bibliography includes 149 references.

A great deal of research has been dedicated to improving the performance of vanadium redox flow battery (VRFB). In this work, we propose the design of a cell for testing membrane electrode assembly of VRFB, which enables the optimization of the flow field, conditions of charge‐discharge tests, and the nature of components (electrodes, membrane) with minimal time and material expenses. The essence of the proposed cell is that the system of channels distributing the electrolyte is made by cutting shaped holes in the sheets of graphite foil (GF). This manner allows easy modification of the flow field configurations. Polarization curves for serpentine, interdigitated, and flow‐through systems were measured according to procedures used in such studies. Cell with GF plates being tested with vanadium‐sulfuric acid electrolyte, outperforms the cell with conventional graphite plates with the same parameters of the flow field. It demonstrates 734 mW cm−2 of peak power density at SOC 50 and 84.3 % of energy efficiency at 84.5 % of electrolyte utilization under galvanostatic charge/discharge cycling with 75 mA cm−2.

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