Enhanced Longevity of Lithium Metal Anodes via Fluorine/Nitrogen Co‐Doped Lightweight 3D Carbon Porous Frameworks

Abstract Lithium metal anodes suffer from uncontrollable volume expansion during electrochemical cycling due to the host‐free nature of lithium deposition, leading to reduced Coulombic efficiency (CE) and shortened cycle life. In this work, a fluorine‐functionalized surface modification (FCMF) is applied to carbonized melamine foam (CMF) using a secondary chemical vapor deposition process, forming an amorphous nitrogen/fluorine co‐doped carbon layer ≈65 nm thick. The FCMF exhibits an exceptionally low areal density of 2.43 mg cm⁻ ² , which is only 28.5% of that of commercial 8 µm copper foil. Fluorine doping significantly enhances the lithium‐ion affinity of the substrate, facilitating uniform lithium deposition throughout the 3D framework. This results in an ultrahigh average CE (99.78% for FCMF vs 99.44% for CMF) and substantially improves symmetric cell cycling performance (2450 h vs 745 h). Additionally, the LiFePO ₄ (single‐side, 11.9 mg cm ^{− 2} ) | FCMF/Li full cell maintains over 400 cycles with 85.6% capacity retention at 2C. This work introduces a scalable chemical vapor deposition method for producing high‐performance 3D current collectors for lithium metal batteries.