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 LiFePO₄ (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.