Dendrite growth and safety issues in a liquid electrolyte seriously hinder the development of Li metal batteries. Hierarchical nanoporous gamma-Al2O3 is synthesized through a hydrothermal method, followed by sufficient encapsulation of a typical organic liquid electrolyte (1 M LiPF6 in EC:DMC). Thus obtained quasi solid electrolyte (QSE) displays combined advantages of the rigid inorganic framework (from solid gamma-Al2O3) and high ionic conductivity (from liquid organic electrolyte). Specifically, the QSE affords a conductivity of 1.1 x 10(-3) S cm(-1) at room temperature and behaves a fine lithium ion transference number of 0.62. Inheriting the merits of solid framework, it also exhibits remarkable thermal/mechanical stabilities and a broad electrochemical window up to 5.0 V (vs. Li+/Li). The assembled LiFePO4 (LFP)/QSE/Li cell delivers a high specific capacity of 136.8 mAh g(-1) after 50 cycles, with capacity retention of 96.5% at room temperature, which is mainly attributed to the high ionic conductivity and remarkably suppressed Li dendrite growth by the QSE. This work extends the application of hierarchical nanoporous structure and enables a safe, efficient operation of Li anode in next generation energy storage systems.