Fast-Charging of Hybrid Lithium-Ion/Lithium-Metal Anodes by Nanostructured Hard Carbon Host

Lithium metal could provide ∼10 times the theoretical specific capacity compared to graphite. However, despite recent progress in improving the Coulombic efficiency (CE), metallic lithium still suffers from poor cyclic stability at high current densities, which limits applications of lithium-metal anodes in high-power scenarios. Here we report stable cycling of metallic lithium under high current densities and realistic cell conditions based on a flower-like nanostructured hard carbon host (CF). CF was both intercalated with lithium ions and plated with lithium metal to render a hybrid lithium-ion/lithium-metal anode capacity. The hybrid cells showed >99% CE up to 12 mA/cm²(4 mAh/cm²) with commercial carbonate electrolyte. The stability of the hybrid anodes was attributed to the uniform lithium plating morphology and fast ion diffusion pathways enabled by the open-pore nanostructures of CF. Moreover, the CF||NMC811 hybrid cells (2 mAh/cm²) showed ∼70% capacity retention after 200 cycles at 10 mA/cm²current densities, while demonstrating >2 times anode specific capacity and much better high-rate stability compared to graphite||NMC lithium-ion cells.