In Situ Chemical Lithiation Transforms Diamond-Like Carbon into an Ultrastrong Ion Conductor for Dendrite-Free Lithium-Metal Anodes.

Lithium (Li)-metal anodes are of great promise for next-generation batteries due to their high theoretical capacity and low redox potential. However, Li-dendrite growth during cycling imposes a tremendous safety concern on the practical application of Li-metal anodes. Herein, an effective approach to suppress Li-dendrite growth by coating a polypropylene (PP) separator with a thin layer of ultrastrong diamond-like carbon (DLC) is reported. Theoretical calculations indicate that the DLC coating layer undergoes in situ chemical lithiation once assembled with the lithium-metal anode, transforming the DLC/PP separator into an excellent 3D Li-ion conductor. This in situ lithiated DLC/PP separator can not only mechanically suppress Li-dendrite growth by its intrinsically high modulus (≈100 GPa), but also uniformly redistributes Li ions to render dendrite-free lithium deposition. The twofold effects of the DLC/PP separator result in stable cycling of lithium plating/stripping (over 4500 h) at a high current density of 3 mA cm-2 . Remarkably, this approach enables more than 1000 stable cycles at 5 C with a capacity retention of ≈71% in a Li || LiFePO4 coin cell and more than 200 stable cycles at 0.2 C in a Li || LiNi0.5 Co0.3 Mn0.2 O2 pouch cell with cathode mass loading of ≈9 mg cm-2 .