Ultrasmooth and Dense Lithium Deposition Toward High-Performance Lithium-Metal Batteries.

Lithium (Li)-metal batteries (LMBs) with stable solid electrolyte interphase (SEI) and dendrite-free formation have great potential in next-generation energy storage devices. Here, vertically aligned 3D Cu 2 S nanosheet arrays are fabricated on the surface of commercial Cu foils, which in situ generate ultrathin Cu nanosheet arrays to reduce local current density and Li 2 S layers on the surfaces to work as an excellent artificial SEI. It is found that Li presents a 3D-to-planar deposition model, and Li 2 S layers are reversibly movable between the 3D nanosheet surface and 2D planar surface of Li during long-term cycling. This enables ultrasmooth and dense Li deposition at 1 mA cm -2 , presenting an average thickness of ≈53.0 µm at 10 mAh cm -2 , which is close to the theoretical Li foil thickness and is highly reversible at different cycles. Thus, 1150 stable cycles with high Coulombic efficiency (CE, 99.1%) at ether-based electrolytes and 300 stable cycles with high CE (98.8%) at carbonate electrolytes are realized in half-cell with a capacity of 1 mAh cm -2 at 1 mA cm -2 . When coupled with commercial cathodes (LiFePO 4 or LiNi 0.8 Co 0.1 Mn 0.1 O 2 ), the full cells present substantially enhanced cyclability under high cathode loading, limited (or zero) Li excess, and lean electrolyte conditions, even at -20 °C.