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The inactive lithium generated by the formation of solid electrolyte interface (SEI) and "dead lithium", and the side reaction of Li with the reactive 3D framework, lead to the low coulombic efficiency (CE) and short cycle life of metal Li anode. In this work, a 3D porous biochar modified by silver nanoparticles (PB-Ag) with high lithiophilic and chemically stable surface is designed as a host for Li anode, achieving no dead lithium generation, small SEI area and minimized side reaction between lithium and the frame surface. Since the paths of inactive lithium production are systematically blocked, this composite lithium anode with 3D frame exhibits a high cycle CE. Characterizations of the PB-Ag show that selectively oxidative decomposition of the active group (-COOH) on the surface and loading of highly dispersed silver nanoparticles are achieved simultaneously through a simple and mild one-step liquid phase reaction. Electrochemical tests demonstrate that the PB-Ag possesses an excellent lithiophilicity, and maintains almost 100% CE and very low mass-transfer polarization potential (<20 mV) after 200 cycles. Moreover, the deposition process of lithium on PB-Ag is investigated in detail by ex-situ SEM. [ABSTRACT FROM AUTHOR]