Engineering thin 3D Li-composite foil negative electrodes with high mechanical toughness

Current three-dimensional lithium negative electrodes are plagued by inherent trade-offs among mechanical robustness, thin processability, and electrochemical performance. Here, we engineer a free-standing Li-composite foil negative electrodes by integrating a lithiophilic Li-Zn alloy with a Li₃N-enriched carbon nanotube network. The Li-Zn alloy strengthens tensile resistance and regulates lithium deposition, while the Li₃N-enriched carbon nanotube network reinforces mechanical toughness, achieving a rupture toughness of 1.3 × 10⁶ J/m³, a 12-fold enhancement over bare lithium. This property enables the fabrication of thin negative electrodes (<10 μm) that resist pulverization during deep Li plating/stripping. In cells with LiNi_0.8Co_0.1Mn_0.1O₂ positive electrodes, the composite negative electrode facilitates extended cyclability (>500 cycles in coin cells at 1 C, 92% retention after 300 cycles in Ah-grade pouch cells at 0.5 C) and sustain high-rate operation (10 C). An 8.5 Ah pouch cell demonstrates a practical specific energy of 553 Wh kg^-1 at cell level when tested at 0.1 C. This work presents a design strategy for realizing high-energy, long-cycle-life lithium metal batteries.