Surface-finish induced textured electrodeposition on 20 μm Li-metal anode

Abstract

Implementing Li metal anode with thickness <50 μm is a key step to achieve high energy density lithium metal batteries. However, the production of thin Li-foils is non-standardized, with the supplier-dependent qualities incurring uncertainties for cell development and evaluation. Here, we demonstrate that Li-foils with varying thicknesses possess distinct surface finishes and bulk-phase textures. As the extrusion-produced 200 μm Li foils are rich in inorganic surface species and (110)-texture, the 20 μm Li produced via rolling feature organic surface species and (100)-Li texture underneath. The surface finish and foil textures are rooted in the angled shear forces and rolling lubricant. Textured Li foils are conducive to epitaxial Li deposition however the native surface passivation layer perturbs the substrate-deposits intimacy and degrades its electrochemical reversibility. Mechanical and chemical polishing were employed to refine the Li surface finish, only the latter achieves an ideal surface finish that reinstates epitaxial Li-electrodeposition. This engenders textured Li deposits, greatly improving the lifespan of lithium metal anodes. Pouch cells employing chemically polished 20 μm Li anodes and 20 mg/cm² NCM811 cathodes exhibit capacity retention of 97.1 % after 100 cycles. The benefit of surface-finish in 20 μm Li was verified in >400 Wh/kg Ah-pouch-cells.