Revisiting Porous Foam Cu Host Based Li Metal Anode: The Roles of Lithiophilicity and Hierarchical Structure of Three-Dimensional Framework

Abstract

Lithium (Li) metal anode (LMA) is one of the most promising anode for high energy density batteries. However, its practical application is impeded by notorious dendrite growth and huge volume expansion. Although foam copper (Cu) sheet as three-dimensional (3D) host can enhance the cycling stability of LMA,  its performance still needs to be further improved and the key factors limiting Li plating/striping behavior is not well addressed. Herein, porous Cu foam is thermally infiltrated with molten Li-rich Li-Zn binary alloy (CFLZ) with variable Li/Zn atomic ratio. The cooling process allows phase separation of liquid Li-Zn alloy, in which LiZn intermetallic compound phase is self-assembled into a network of mixed electron/ion conductor distributed in the matrix of metallic Li phase, acting as the sublevel skeleton architecture in the pores of CF. The as-prepared CFLZ composite anodes are systematically investigated to highlight the roles of the tuneable lithiophilicity and hierarchical structure of the frameworks. Meanwhile, the CF scaffold itself is covered with a thin layer of Cu-Zn alloy, exhibiting high lithiophilicity. The CFLZ with high Zn content facilitates uniform Li nucleation and deposition, thereby effectively suppressing Li dendrite growth and volume fluctuation. Consequently, the hierarchical and lithiophilic framework shows low Li nucleation overpotential and highly stable Coulombic efficiency for 200 cycles in conventional carbonate based electrolyte. The full cell coupled with LiFePO4 cathode demonstrates high cycle stability and rate performance. This work provides valuable insights into the design of advanced dendrite-free 3D LMA toward practical application.

Keywords: Li metal anode, 3D skeleton, mixed electron/ion conductor, lithiophilicity