Enhanced Stability in Zero-Excess Li-Metal Batteries via Prelithiated Carbon Nanofiber Interlayers

Zero-excess lithium metal batteries (ZELMBs), here referring to the absence of Li-foil on the anode side rather than the strict absence of additional lithium inventory, are considered a promising approach to increase energy density, but their performance is often limited by dendritic lithium growth and low Coulombic efficiency (CE). Here, we explore a chemically prelithiated carbon nanofiber (CNF) interlayer as a lithiophilic host to mitigate these challenges. Advanced characterization techniques, including solid-state NMR, Raman spectroscopy, and depth-profiling XPS, suggest that the prelithiation process leads to the formation of an inorganic-rich interphase containing LiOH, Li₂O, and lithium-containing organic species. This interphase is associated with reduced nucleation overpotential and more uniform lithium deposition, helping to suppress dendritic growth. Furthermore, prelithiation introduces additional lithium inventory into the CNF interlayer, a fraction of which may compensate for initial lithium loss during early cycling. As a result, CNF_Prelith paired with LiFePO₄ cathodes demonstrates improved cycling stability, with CE exceeding 99.95% and good capacity retention at elevated C-rates (up to 4 C). Notably, stable performance is achieved without extended formation protocols in full cell configurations. These findings indicate that prelithiated interlayers can be a useful strategy for stabilizing Li-foil-free lithium metal cells under limited-lithium conditions.