Sustainable Carbon Fibers Enable Stable Long-Term Lithium Metal Deposition for Prospective Zero-Excess Lithium Metal Batteries

Three-dimensional current collectors have emerged as a promising strategy to promote uniform Li deposition and extend the cycle life of zero-excess lithium metal batteries. However, excessive Li loss in the first cycle due to solid electrolyte interphase (SEI) formation on the large surface area, combined with the use of dense or nonrenewable materials and complex, multistep fabrication processes, limits their practical implementation. In this work, a lightweight, lignin-derived carbon fiber (CF) current collector is presented. It is fabricated via a simple and sustainable electrospinning process, and after carbonization has abundant structural defects and nanoscale porosity. Surface defects promote the formation of a stable, inorganic-rich SEI, efficiently passivating the current collector, while pores of ∼1.0–1.4 nm enable quasi-metallic Li clusters to form before plating, providing a conductive network and distributed nucleation sites that enhance Li plating/stripping reversibility and cycle life. This CF current collector exhibits a first-cycle active Li loss of only 4.8%–8.9% relative to the typical Li inventory of commercial lithium-ion battery cathodes and maintains a coulombic efficiency of 99.0% over 200 cycles, demonstrating excellent electrochemical performance.