Lithium batteries are considered the key storage devices for most emerging green technologies such as wind and solar technologies or hybrid and plug-in electric vehicles. Despite the tremendous recent advances in battery research, surprisingly, several fundamental issues of increasing practical importance have not been adequately tackled. One such issue concerns the energy efficiency. Generally, charging of 10(10)-10(17) electrode particles constituting a modern battery electrode proceeds at (much) higher voltages than discharging. Most importantly, the hysteresis between the charge and discharge voltage seems not to disappear as the charging/discharging current vanishes. Herein we present, for the first time, a general explanation of the occurrence of inherent hysteretic behaviour in insertion storage systems containing multiple particles. In a broader sense, the model also predicts the existence of apparent equilibria in battery electrodes, the sequential particle-by-particle charging/discharging mechanism and the disappearance of two-phase behaviour at special experimental conditions.

Nanostructured materials offer the possibility to make use of small transport lengths and small separation distances almost like in fluids, but unlike fluids, the higher structural stability of the solid state can be taken advantage of. Recent findings in the field of Li-batteries highlight the potential for room temperature applications. This paper addresses advantages and disadvantages of nanostructured matter with respect to stability, storage capacity, voltage and charging/discharging rates. In this context we discuss a novel interfacial storage mechanism for lithium which, in the mesoscopic case, forms a bridge between batteries and capacitors.

An exact equivalent circuit including terminal parts, which takes account of electrical and chemical control parameters in a uniÐed way, is derived for a cell with a mixed conductor (or electrolyte) without internal sources or sinks. In one-dimensional problems electrochemical kinetics can be mapped by two-dimensional circuits exhibiting the spatial and the thermodynamic displacement as two independent coordinates. One main advantage of the exact circuits with respect to the underlying di †erential equations is the ability to simplify the description according to speciÐc situations. As we show in several examples in the second part of the paper, it is straightforward to select the elements relevant for the particular experimental conditions and so to make appropriate approximations. This is most helpful for the description of electrochemical systems, such as fuel cells, membranes, pumps and batteries.

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