Contemporary scientific literature on electrochemical supercapacitors is reviewed. The electrochemical supercapacitors are fast-rechargeable energy storage devices. They are classified as electrical-double-layer capacitors based on the recharging of the electric double layer; pseudocapacitors, and hybrid capacitors. The electrochemical supercapacitors are used in devices of pulse technology, for electrical energy accumulation, for starting and recuperation of the braking energy in internal combustion engines; for smoothing out peak loads in electrical networks and in numerous portable devices. The electrochemical supercapacitors are subdivided into those of power type and energy type. The power-type (pulsed) supercapacitors have high specific power (~up to 100 kW/kg); the energy-type ones, high specific energy (~up to 25 W h/kg). Compared to batteries, the power-type supercapacitors have a much higher power density and cyclability, up to hundreds of thousands and even million cycles. The electrical-double-layer supercapacitors are also used in the capacitive water deionization devices for water desalination.

The literature on capacitive deionization (CDI) of water is discussed. The CDI is a new method of water desalination which consists of pumping water to be deionized between highly disperse carbon electrodes with a certain potential difference applied to these electrodes. The CDI is characterized by the lower expenditure of energy as compared with the other desalination methods. Different modifications of CDI are considered such as membrane capacitive deionization (MCDI), CDI with redox reactions on electrodes, and CDI with flow-through electrodes. The dependence of CDI on the porous structure of electrodes, the size of hydrated ions, the type of carbon used for electrodes, the electric double layer capacitance, the presence of functional groups, the wettability of electrodes, the pH, and other factors is considered. The problems of the production of pure drinking water and also of the degradation of electrodes are discussed. The use of CDI in practice is described.

The aim of the work was to elucidate the nature of charge-selective properties of macroporous composite inorganic membranes modified with nanoparticles of hydrated zirconium dioxide. The membranes have been investigated using methods of standard contact porosimetry, potentiometry, electron microscopy and small-angle X-ray scattering. The ion exchanger has been found to deposit inside pores of ceramics. Differential curves of pore volume distribution have been resolved using Lorentz functions; each maximum has been related to structure elements of the matrix and ion exchanger by means of calculations according to homogeneous and heterogeneous geometrical models. It was found that the voids, the radius of which is 4 to 8 nm, are responsible for charge selectivity of the composite membranes. These pores are formed due to blocking of macropores of ceramics with aggregates of nanoparticles of the ion exchanger; the radius of these aggregates is 20 to 24 nm. The membranes were applied to desalination of the solution containing NaCl. The removal degree of the salt from the solution reached 95% and 9% for the composite and unmodified membranes, respectively.

A review of modern scientific literature on the electric double layer capacitors based on the recharging of the electric double layer is presented. The electric double layer capacitors are used in pulse technology devices, as electric energy storage devices, for starter firing, for the recuperating of the braking energy of internal combustion engines, for smoothing peak loads in electric networks, and in various portable devices. The electric double layer capacitors are subdivided into the power electric double layer capacitors and the energy ones. The power (pulse) electric double layer capacitors have a high specific power (up to hundreds of kW/kg), whereas the energy electric double layer capacitors have a high specific energy (~25 W h/kg and higher). Compared to batteries, the power electric double layer capacitors have a much higher power density and better cyclability—up to hundreds of thousands and millions of cycles. Publications on the electric double layer capacitors’ self-discharge are reviewed.