There is a growing need for energy storage solutions with high energy density and high safety due to the quick growth of smart grids and electric cars. Although traditional liquid lithium-ion batteries have been commercialized, their energy density is close to the theoretical limit, and there are safety hazards such as electrolyte leakage and flammability. In contrast, all-solid-state lithium-ion-batteries (ASSLIBs) with non-combustible solid electrolytes can completely eliminate the risk of thermal runaway, making them the core direction of the next-generation energy storage technology. However, issues including the development of lithium dendrites and the high interfacial impedance between the solid electrolyte and the electrode have made it difficult to commercialize. This paper systematically reviews the key roles and design strategies of nanomaterials in the positive electrode, negative electrode and electrolyte of ASSLIBs. Through size effect, high specific surface area and controllable interface characteristics, nanomaterials provide innovative solutions for optimizing ion transport, suppressing volume expansion and enhancing interface stability. Research shows that nanotechnology significantly enhances the energy density, cycle life and fast charging performance of ASSLIBs through material nanoscale, composite structure design and interface optimization. In the future, through the integration of multi-disciplinary technologies and innovation in preparation processes, nanomaterials are expected to promote the commercial application of ASSLIBs in fields such as electric vehicles, and become the core technology of high-safety, high-energy-density energy storage technologies of the future.