Dendrite growth under large current density is the key intrinsic issue impeding a wider application of Li metal anodes. Previous studies mainly focused on avoiding dendrite growth by building an additional interface layer or surface modification. However, the mechanism and factors affecting dendrite growth for Li metal anodes are still unclear. Herein, we analyze the causes for dendrite growth, which leads us to suggest three-dimensional (3D) metal anodes as a promising approach to overcome the dendrite issues. A 3D composite Li anode was prepared from renewable carbonized wood doped with Sn to demonstrate its superior electrochemical performance compared with Li foils. The anode was cycled at various current densities from 0.1 to 10 mA cm-2 for five cycles at each current density, displaying low overpotential compared with conventional Li foils. Long galvanostatic cycling at 1 mA cm-2 for 1000 h and at 2 mA cm-2 for 500 h was achieved without dendrite growth. Further analysis reveals that the 3D structure facilitates surface diffusion by increasing the surface area from 5.23 × 10-3 m2 g-1 (Li foil) to 2.64 m2 g-1 and by creating nanoscale separation walls. The tin alloying effectively prevents non-uniform lithium plating by creating abundant nucleation centers. Additionally, suitable alloying elements for a wider range of 3D Li anodes have been identified from density functional theory calculations.
Keywords: 3D anode; dendrite; formation energy; lithium metal battery; metal anode.