Three-dimensional (3D) porous frameworks have attracted considerable interest as lithium-metal electrodes for nextgeneration rechargeable batteries. The high surface areas and large pore volumes of 3D frameworks are beneficial for reducing local current densities and suppressing volume changes. However, uneven Li plating on top of the framework electrode (top growth) has yet to be resolved. To enable the bottom-up Li growth while suppressing the top growth, herein, we propose a rational design of 3D framework electrodes with an interfacial activity gradient (IAG) based on a kinetics-based mechanistic analysis. A simulation demonstrates that an IAG design promotes the bottom-up Li growth, which is experimentally proven using model architectures. The IAG-Cu framework shows considerable improvements in morphological stability and reversibility during high-capacity Li storage, compared to the Cu framework with a uniform interfacial activity. This work provides fundamental insight into the design of 3D frameworks to boost the cycling stability of Li-metal batteries.

Li metal batteries have been considered a promising alternative to Li-ion batteries because of the high theoretical capacity of the Li metal. There have been remarkable improvements in the electrochemical performance of Li metal electrodes, although the current Li metal technology is not sufficiently practical in terms of cycle performance, safety, and volume change during cycling. Herein, the role of pore size distribution in the Li metal plating behavior of porous frameworks is clarified to attain the ideal pore structure of the framework as a Li metal host. The monodisperse pore framework shows the conformal electrodeposition of the Li metal, whereas the pore size gradient framework exhibits the superconformal plating of the Li metal. The conformal and superconformal electrodepositions of the Li metal are elucidated in terms of variations along the pore depth direction in the charge-transfer resistance on the pore walls and the ionic resistance of electrolytes confined in pores. The pore size gradient framework also shows excellent electrochemical performance, such as stable capacity retention over 760 cycles with 0.5 mAh cm–2 at 2 mA cm–2. These findings provide fundamental insights into strategies to improve the electrochemical performance of porous frameworks for Li metal batteries.

The synergistic surface tailoring of three-dimensional Cu frameworks achieved via Ag-induced activation and Al2O3-induced passivation leads to a significant improvement in the Li plating–stripping efficiency and cycling performance.