Structurally Tailored Hierarchical Cu Current Collector with Selective Inward Growth of Lithium for High-Performance Lithium Metal Batteries

Li-metal is gaining attention as a next generation anode active material, of which the primary attribute is its energy density. However, Li dendrite formation is the primary challenge. Herein, a design strategy with increased structural dimensions and hierarchy for Li-metal anode is investigated to stabilize the dendrite formation for extending the cycle life with high reversibility. For this, diverse structural current collectors (CCs) are fabricated by manipulating structural design in different length scales and characterized as a Li-metal anode. The hierarchy (i.e., nanostructures inside the microcavities) can not only reduce the current density on entire anode surface but also concentrate the local electrical field onto inner surfaces of the microstructures, inducing preferential Li nucleation inside microcavities and promoting confined growth of Li. It is confirmed that introduction of structural hierarchy can enhance the cycle life by 364% and the preservation of coulombic efficiency > 90% by 266%. The design strategy is extended by exploring a practical one-step fabrication of the hierarchical CC with even greater performance via the inward growth mechanism. This work elucidates the mechanism of inward Li growth using tailored surface geometries for Li dendrite suppression, which can be a guideline for designing structured anode CCs for Li-metal batteries.