“Lithium‐Free” Anode Solid‐State Batteries Enabled by 3D Structured Miec Garnet

ABSTRACT

Inhomogeneous lithium nucleation at the current collector‐solid electrolyte interface leads to unstable lithium growth and poor reversibility in “lithium‐free” solid‐state batteries. Here we show that stable lithium formation occurs within a mixed ionic and electronic conducting (MIEC) garnet scaffold. The intrinsic electronic conductivity of the porous framework enables lithium to nucleate uniformly along internal pore surfaces, rapidly forming a conformal lithium coating, thus establishing electronic connectivity at very low lithium volume fraction. This uniform lithium formation dramatically lowers anode impedance, enabling reversible lithium plating and stripping with Coulombic efficiencies of a previously unheard‐of 99.95%. When paired with NMC811 cathodes, bilayer (MIEC(P)‐LLZ(D)) “lithium‐free” full cells exhibit stable, highly reversible cycling at practical current densities, all at room temperature with no applied pressure. The interplay between lithium volume fraction and impedance is quantitatively modeled, transforming the understanding of lithium nucleation in a “lithium‐free” cell from an empirical interface problem to a percolation‐governed transport process, guiding the design of electronically percolating scaffolds for next‐generation solid‐state batteries.