Double-gradient host enabling bottom-up Li deposition towards hybrid lithium-ion/metal anode with long lifespan

Abstract

The graphite-based hybrid Li-ion/metal anode holds great promise to be one of the ultimate anode choices, owing to its high specific capacity (often up to 500 mAh/g), obviously superior to 372 mAh/g of the commercial graphite anode. Unfortunately, Li deposition on the top surface of the conductive graphite host can easily drive Li dendrite growth, dead Li accumulation, and the blockage of Li⁺ transport pathways, leading to low host space utilization and cycling stability deterioration. Herein, a graphite host with lithiophilicity and reactive activity dual-gradient is constructed by integrating a surface insulation passivation and a bottom lithiophilicity modification to realize the “bottom-up” deposition behavior for hybrid Li-ion/metal anode. The conformal coating layer of electrical insulating and lithiophobic polymer can efficiently retard Li⁺ reduction and deposition on the top surface of the conductive host, while the decorated Ag nanoparticles with high lithiophilicity on the host bottom enable much lower Li nucleation barrier, thereby guiding the preferential bottom-up Li deposition. Li dendrite growth is effectively inhibited and the synergistic effects realize high space utilization of the host. Consequently, the hybrid graphite-Li anodes with 600 mAh/g of lithiation capacity (∼3.0 mAh cm⁻²) deliver significantly improved cycling stability over 500 cycles with a negligible capacity fading rate of 0.05 % per cycle at 1 C in LiFePO₄-based full-cells (N/P ratio = 1.9).