Ever-increasing demand for better batteries has set extraordinarily high standards for electrolyte materials, which are far beyond the realm of a conventional nonaqueous electrolyte design. Superconcentrated (or highly concentrated) solutions are emerging as a new class of liquid electrolytes with various unusual functionalities beneficial for advanced lithium (Li) battery applications. This article reviews unique features, as well as basic physicochemical properties, of highly concentrated electrolytes from the viewpoint of their peculiar solution structure, and discusses their future contributions to advanced battery technologies. The Author(s) 2015. Published by ECS. All rights reserved.