Quasi-metallic lithium encapsulated in the subnanopores of hard carbon for hybrid lithium–ion/lithium metal batteries

• Hard carbon encapsulates QM-Li in its sub-nanometer structure for hybrid anode. • Sub-nanometer confinement strategy avoids side reactions. • The hybrid anode demonstrates a high CE of 99.7% for 240 cycles in half cell. The commercial application of Li metal anodes (LMAs) has been impeded by the irreversible side reactions, uncontrolled dendrite growth, and large volume changes. In this work, we utilize sub–nanometer confinement to address these challenges by encapsulating quasi–metallic Li (denoted as QM–Li) in the subnanopores of hard carbon (HC). The sub–nanometer pores can effectively prevent the contact between electrolyte and QM–Li, provide large pore volume for QM–Li storage, and restrain the dendrite growth. Therefore, the HC hybrid anode realizes a high Coulombic efficiency of 99.7% in half cell over 240 cycles in ester electrolyte. When coupled with LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), the assembled full cell exhibits stable cycling stability over 200 cycles with 0.1% capacity decay per cycle. The sub–nanometer confinement effect provides new route for practical LMAs.