Abstract: This invention relates to electrical engineering. In particular, the invention relates to the design of electrochemical device storing electric energy, and can be used in modern power engineering, for example, in devices storing regenerative braking energy in transport, as traction batteries for electric transport (electric vehicles, hybrid electric vehicles), in emergency power systems when operating in a floating or trickle charge mode. The invention ensures steady operation of this device due to stable preservation of a given concentration of electrolyte components on the electrodes, and improvement of service life in various modes of operation.