Solid and Solid-Like Composite Electrolyte for Lithium Ion Batteries: Engineering the Ion Conductivity at Interfaces

The development of solid composite electrolytes or solid composite electrolytes (SCEs) consisting of an ionic conductor and a dielectric matrix offers an elegant strategy to enhance the ionic conductivity of electrolytes by engineering the interface conduction. At the conductor/matrix interface, the ionic conductivity can be enhanced by the enriched charge carrier concentration and/or the changed molecular structure of the ionic conductor. This review deals with the interfacial ion conduction mechanisms of the inorganic particle-based SCE, polymer-SCE, and ionic liquid electrolyte-based SCE (ILE-SCE). In the first part of this review, an overview is given of the space-charge theory developed to describe the increased vacancy concentration at the interface of inorganic particle-based SCE. In the second part, the proposed interface interactions and structural changes associated with interface conduction for the polymer-SCE and ILE-SCE are reviewed. For the ILE-SCE, the preparation methods and interface characterization are discussed together with the proposed conductivity models. The use of mesoporous matrix materials with high internal surface area for ILE-SCE is reviewed here for the first time.