Superdense Lithium Deposition via Mixed Ionic/Electronic Conductive Interfaces Implanted In Vivo/Vitro for Stable Lithium Metal Batteries

Abstract Lithium metal batteries specialize in energy density, while the immoderate dendrite growth and solid electrolyte interphase (SEI) proliferation have been impeding their practical application. The key is the regulation of Li + diffusion/nucleation behaviors toward a dense deposition. Herein, Li 9 Al 4 /Li 3 N energized mixed ionic/electronic conductive (MIEC) interfaces are pre‐implanted in both the surface and bulk of the lithium metal anode. Such MIEC interfaces are activated from the in situ conversion and nano‐alloying reactions between AlN and metallic Li and are uniformly dispersed via facile mechanical kneading. In vitro, MIEC interfaces participate in the formation of an inorganic‐enriched SEI that balances ionic transport, electron blocking, and mechanical strength to guarantee homogeneous ion fluxes and structural integrity. In vivo, a unique nanorod‐array architecture enables a released internal stress and rapid diffusion kinetics, affording a dense and large granular plating manner. As a result, the symmetric cell delivers a striking cumulative capacity of >120000 mAh cm −2 at 20 mA cm −2 @20 mAh cm −2 with a prolonged lifespan of over 6000 h. The improved machinability also enables a scalable fabrication of ultrathin foil to achieve a stable high‐areal‐capacity full cell for 320 cycles with enhanced energy density characteristics both gravimetrically and volumetrically.