Graphitized Layers Encapsulated Carbon Nanofibers as Li-Free Anode for Hybrid Li-Ion/Metal Batteries

Hard carbon, the Li-free anode for hybrid Li-ion/metal batteries (LIB/LMBs), has great potential for enhancing fast charging capability, energy density, and battery lifespan. However, low initial Coulombic efficiency (ICE) and Li dendrite growth are crucial factors constraining its development. In this work, graphitized layers encapsulated carbon nanofibers (G-CF) are fabricated via Joule heating within 10 s. The C_sp2 structure in graphitized layers reduces side reactions with the electrolyte, promotes LiC compound formation, and improves Li ions/metal reversibility. The inner amorphous carbon structure boosts fast charging capability. As a result, the G-CF anode attains an 85.2% high ICE and exhibits long-term cycling stability. Under 2 C fast charging, it maintains an average Coulombic efficiency of 99.94% and a 500 mAh g^-1 capacity after 200 cycles. Moreover, when the N/P ratio is 0.5, the G-CF||NCM811full cell has an ICE of 84.5% and provides a capacity of 530.8 mAh g^-1 and an energy density of 365.9 Wh kg^-1 at 1C. The G-CF||LFP full cell can also provide a capacity of 541.0 mAh g^-1 under the same N/P ratio. A 30 mAh pouch cell can stably cycle over 100 times. This heterogeneous hard carbon design paves a revolutionary path for manufacturing high-efficiency Li-free anodes for hybrid LIB/LMBs.