Energy gels: A bio-inspired material platform for advanced energy applications

Energy conversion and storage systems with high efficiency have attracted great research interest in recent years. To improve the performance of energy devices, nanomaterials with delicately controlled structures and interfaces have been applied. However, low-dimensional nanomaterials suffer from inhomogeneous aggregation, severe re-stacking, and the formation of bottlenecks and poor contacts during the processing and assembly, thus hindering the transport of electrons or ions in energy devices. Gel materials, a special class of bio-inspired materials, are emerging as promising candidates to overcome the drawbacks of low-dimensional nanomaterials. The 3D nanostructured gel network promotes electron transport along the backbone while facilitating the diffusion of ions through hierarchical pores, as well as providing high surface area for interfacial reactions. In addition, the properties of gels can be facilely tuned, thereby further extending their applications and improving their performance. To date, various synthetic strategies have been developed for the preparation of gel materials, including carbon-based gels, conductive polymer gels, ionically conductive gels and inorganic gels. These gel materials have successfully served as electrode materials, electrolytes, self-supported current collectors, 3D binder systems, etc. in various kinds of energy conversion and storage applications, such as lithium ion batteries, supercapacitors, catalysts, and fuel cells. In this review, we summarize the synthesis of various electrically conductive gel materials, including carbon-based gels, conductive polymer gels, and ionically conductive gels and their applications in energy conversion and storage devices. We also provide the perspective on the future developments of these gel materials in energy-related fields. (C) 2016 Elsevier Ltd. All rights reserved.