Interface Design for High‐Performance All‐Solid‐State Lithium Batteries.

All‐solid‐state batteries suffer from high interface resistance and lithium dendrite growth leading to low Li plating/stripping Coulombic efficiency (CE) of <90% and low critical current density at high capacity. Here, simultaneously addresses both challenges are simultaneously addressed and the Li plating/stripping CE is significantly increased to 99.6% at 0.2 mA cm−2/0.2 mAh cm−2, and critical current density (CCD) of > 3.0 mA cm−2/3.0 mAh cm−2 by inserting a mixed ionic‐electronic conductive (MIEC) and lithiophobic LiF‐C‐Li3N‐Bi nanocomposite interlayer between Li6PS5Cl electrolyte and Li anode. The highly lithiophobic LiF‐C‐Li3N‐Bi interlayer with high ionic conductivity (10−5 S cm−1) and low electronic conductivity (3.4×10−7 S cm−1) enables Li to plate on the current collector (CC) surface rather than on Li6PS5Cl surface avoiding Li6PS5Cl electrolyte reduction. During initial Li plating on CC, Li penetrates into porous LiF‐C‐Li3N‐Bi interlayer and lithiates Bi nanoparticles into Li3Bi. The lithiophilic Li3Bi and Li3N nanoparticles in LiF‐C‐Li3N‐Li3Bi sub‐interlayer will move to CC along with plated Li, forming LiF‐C/Li3N‐Li3Bi lithiophobic/lithiophilic sublayer during the following Li stripping. This interlayer enables Co0.1Fe0.9S2/Li6PS5Cl/Li cell with an areal capacity of 1.4 mAh cm−2 to achieve a cycle life of >850 cycles at 150 mA g−1. The lithiophobic/lithiophilic interlayer enables solid‐state metal batteries to simultaneously achieve high energy and long cycle life. [ABSTRACT FROM AUTHOR]