The demand for energy across the world is constantly rising. Therefore remarkable endeavors have been dedicated to the development of high-performance energy storage devices with nanoscale design and hybrid approaches. Inorganic nanomaterials like transition metal oxide/hydroxide, metal chalcogenide, metal carbide, metal–organic framework, carbonaceous compounds, polymer-based porous materials, and their hybrid nanocomposites are being used for energy storage purposes in lithium-ion batteries, supercapacitors (SCs), etc. To produce these nanomaterials that are ideal for energy storage, it is very important to have porous structures, high surface area, high electrical conductivity, charge accommodation capacity, and tunable electronic structures. These electrodes can be synthesized via several synthetic strategies like intercalative hybridization, core–shell architecture, surface anchoring, and defect control. This book attempts to discuss the synthesis and applications of various advanced nanomaterials and their hybrid nanocomposites that are being used for designing efficient batteries and SCs-based energy storage systems. Moreover, their features, limitations, and real-time resolutions will be focused on.