An Ultrastrong Double-Layer Nanodiamond Interface for Stable Lithium Metal Anodes

Effective stabilization of lithium metal has been hindered by the exacting requirements for the protection layer. Among all materials, the mechanical strength and electrochemical inertness of diamond is a prime candidate for lithium stabilization. Herein, we successfully rendered this desirable material compatible as lithium metal interface, which strictly satisfied the critical requirements. Our interface possessed the highest modulus among all the lithium coatings (>200 GPa), which can effectively arrest dendrite propagation. Since pinholes are the major failure mechanisms of artificial interfaces, a novel double-layer design was proposed to enhance the defect tolerance, enabling uniform ion flux and mechanical properties as confirmed by both simulation and experiments. Thanks to the multifold advantages of our interface design, high Coulombic efficiency of >99.4% was obtained at 1 mA cm−2; and more than 400 stable cycles were realized in prototypical lithium-sulfur cells with limited lithium, corresponding to an average anode Coulombic efficiency of >99%. [Display omitted] •Nanodiamond thin film was fabricated as interfacial protection for Li metal anode•A unique double-layer nanodiamond design was proposed to ensure uniform ion flux•The nanodiamond thin film possess >200 GPa modulus for dendrite suppression•Significantly improved battery performance was realized in half and Li-S full cells The Li metal anode holds great promise for next-generation battery systems. However, its practical applications are severely hindered by the low efficiency and potential safety hazards, largely due to the high reactivity of metallic Li toward liquid electrolytes. This work demonstrates the utilization of nanodiamond thin film as surface protection for metallic Li, where Li can be electroplated solely underneath the film and shielded from parasitic reactions with electrolyte. The nanodiamond thin film possesses not only excellent electrochemical stability but also extremely high modulus for dendrite suppression. Importantly, since pinholes in the surface protection layer undermine the uniformity of ion flux, a unique double-layer structure was proposed to enhance the defect tolerance of the design, where defects in one layer can be screened by the other intact layer. The nanodiamond interface enables efficient cycling of Li metal anode, paving the way for viable Li metal batteries in the future. The stability of the Li-electrolyte interface is critical to the practica