Solid-state lithium (Li) metal batteries (SSLMBs) have garnered considerable attention due to their potential for high energy density and intrinsic safety. However, their widespread development has been hindered by the low ionic conductivity of solid-state electrolytes. In this contribution, a novel Li-rich transport mechanism is proposed to achieve ultrafast Li-ion conduction in composite solid-state electrolytes. By incorporating cation-deficient dielectric nanofillers into polymer matrices, it is found that negatively charged cation defects effectively intensify the adsorption of Li ions, resulting in a high Li-ion concentration enrichment on the surface of fillers. More importantly, these formed Li-rich layers are interconnected to establish continuous ultrafast Li-ion transport networks. The composite electrolyte exhibited a remarkably low ion transport activation energy (0.17 eV) and achieved an unprecedented ionic conductivity of approaching 1 × 10⁻