Stable Anode‐Free All‐Solid‐State Lithium Battery through Tuned Metal Wetting on the Copper Current Collector

Abstract

A stable anode‐free all‐solid‐state battery (AF‐ASSB) with sulfide‐based solid‐electrolyte (SE) (argyrodite Li ₆PS ₅Cl) is achieved by tuning wetting of lithium metal on “empty” copper current‐collector. Lithiophilic 1 µm Li ₂Te is synthesized by exposing the collector to tellurium vapor, followed by in situ Li activation during the first charge. The Li ₂Te significantly reduces the electrodeposition/electrodissolution overpotentials and improves Coulombic efficiency (CE). During continuous electrodeposition experiments using half‐cells (1 mA cm ⁻²), the accumulated thickness of electrodeposited Li on Li ₂Te–Cu is more than 70 µm, which is the thickness of the Li foil counter‐electrode. Full AF‐ASSB with NMC811 cathode delivers an initial CE of 83% at 0.2C, with a cycling CE above 99%. Cryogenic focused ion beam (Cryo‐FIB) sectioning demonstrates uniform electrodeposited metal microstructure, with no signs of voids or dendrites at the collector‐SE interface. Electrodissolution is uniform and complete, with Li ₂Te remaining structurally stable and adherent. By contrast, an unmodified Cu current‐collector promotes inhomogeneous Li electrodeposition/electrodissolution, electrochemically inactive “dead metal,” dendrites that extend into SE, and thick non‐uniform solid electrolyte interphase (SEI) interspersed with pores. Density functional theory (DFT) and mesoscale calculations provide complementary insight regarding nucleation‐growth behavior. Unlike conventional liquid‐electrolyte metal batteries, the role of current collector/support lithiophilicity has not been explored for emerging AF‐ASSBs.