The merits and uniqueness of nanotechnology have long attracted great interest and attention from energy storage/conversion-related fields, especially in rechargeable lithium (Li) batteries. For instance, nanosizing of active materials can reduce the Li diffusion paths, far enhancing the cell rate capability. Besides, nanoscale coating is beneficial to improve the stabilities of electrochemical materials. Despite such benefits, since nanosized active materials are facing the limitation of practical viability along with energy density and manufacturing process, new application strategies of nanotechnology in batteries have been proposed through the functionalization of inactive battery components. Among them, in this study, we present a new, hybrid type of the electrolyte containing the highly dispersed, nanosized functional particles, namely, nanoparticle-dispersed colloidal electrolytes (NDCEs). Throughout the article, fundamentals, microscale structures, and designing principles of NDCEs are comprehensively studied to achieve the desired properties for successful applications in conventional Li-ion batteries and beyond Li-ion systems, such as rechargeable Li-metal batteries. On a basis of the interesting features of NDCEs, future perspectives are suggested, which may help move forward its commercialization in the future battery technologies.