Bilayer interphase engineering enabling practical anode-free lithium metal batteries

The continuous lithium consumption between the interphase of electrolyte and lithium metal has primary influence for limited lifespan of anode-free lithium metal batteries (AFLMBs). Herein, an effective concept of using bilayer interphase engineering to regulate the nanoscale structure of the deposited Li has been proposed to enhance the cycling lifespan of AFLMBs. The nanoscale bilayer structure is tailored through magnetron sputtering. The inner layer is dominated by high-entropy alloy (HEA, CuInCdSnZn) to improve lithiophilicity. The outer layer contains lithium fluoride (LiF) to improve homogeneity, leading to reversible Li plating/stripping and mitigating reconstruction of solid-electrolyte interphase (SEI). Benefiting from the bilayer design, the coin cell consisting of a Cu-HEA-F anode and a high-loading cathode (NCM811, 10.5 mg cm⁻²) performs 35 cycles at discharge rates of 0.5 C, significantly outperforming for bare Cu. Large-capacity pouch cells (1.5/2.5 Ah) with high-loading cathode (7.6 mAh cm⁻², single side) and lean electrolyte (1.6 g Ah⁻¹), achieve high-energy density of 360/380 Wh kg⁻¹ and lifespan about 20 cycles.