Bifunctional lithiophilic carbon fibers with hierarchical structure for high-energy lithium metal batteries

Lithium (Li) metal is an impeccable candidate anode for satisfying the energy density requirements of next-generation Li batteries. However, Li dendritic growth and fragile solid-elecrolyte interphase (SEI) caused by the high reactivity between Li and electrolyte are the primary challenges for its large-scale applications. Herein, a bifunctional lithiophilic hierarchical substrate composed of high-density nitrogen-doped carbon nanotubes and Co nanoparticles encapsulated in graphene (Co@G) decorated carbon fibers (Co-N-CNT-CF) can modulate the structural dimensions and hierarchy of Li nucleation/growth and alleviate Li volume expansion, achieving the homogeneous Li plating/stripping behavior. Density functional theory (DFT) calculations and experimental results confirm the highly lithiophilicity of the substrate, which exhibits a low Li nucleation overpotential, enhanced Coulombic efficiency (CE), small voltage hysteresis, and ultrastable lifespan without dendritic formation. As coupled with the thick LiFePO4 and LiCoO2 (∼2 mA h cm−2) cathodes, the Co-N-CNT-CF@Li composite anode (N/P = 3) enables a high reversible capacity, high Li utilization, and improved cycle stability. This work engineers a hierarchical structure of the three-dimensional (3D) lithiophilic carbon substrate for realizing highly reversible, dendritic-free Li metal anodes.