The storage of electroenergy is an essential feature of modem energy technologies. Unfortunately, no economical and technically feasible method for the solution of this severe problem is presently available. But electrochemistry is a favourite candidate from an engineering point of view. It promises the highest energy densities of all possible alternatives. If this is true, there will be a proportionality between the amount of electricity to be stored and the possible voltage, together with the mass of materials which make this storage possible. Insofar it is a matter of material science to develop adequate systems. Electricity is by far the most important secondary energy source. The present production rate, mainly in the thermal electric power stations, is in the order of 1.3 TW. Rechargeable batteries (RB) are of widespread use in practice for electroenergy storage and supply. The total capacity of primary and rechargeable batteries being exploited is the same as that of the world electric power stations. However, the important goal in the light of modem energy technology, namely the economical storage of large amounts of electricity for electric vehicles, electric route transport, load levelling, solar energy utilization, civil video & audio devices, earth and spatial communications, etc. will not be met by the presently available systems. Unless some of the new emerging electrochemical systems are established up to date, RB's based on aqueous acidic or alkali accumulators are mainly produced today.