Interfacial mass storage in nanocomposites

The most significant electrochemical storage systems are insertion batteries in which the electrode function relies on the uptake of lithium (or sodium) ions and electrons by the electroactive phase. This short review considers the case of interfacial storage and focuses on abrupt junctions. The materials space may be substantially extended and the rate performance substantially enhanced by using job-sharing composites in which the Li⁺ (or Na⁺) are stored in one and the e⁻ in the other phase. Literature examples relying on such a mode are reviewed. Thermodynamics and kinetics of such space charge storage are discussed and the discussion embedded in the more general context of storage in mixed conductors which includes both bulk and space charge zones. In this way a deeper understanding of storage in nanosystems, the behavior of passivation layers as well as transfer and transport kinetics of battery systems is achieved.