Electrochemically Dealloyed 3D Porous Copper Nanostructure As High-Performance Anode Current Collector of Li-Metal Batteries

Abstract

Li metal anode is the ultimate choice for Li batteries owning to its highest theoretical capacity (3806 mAh/g) and lowest redox potential (-3.04 V vs. standard hydrogen electrode) among possible candidates.[1] However, despite the advantages of Li metal anodes, a number of remaining challenges must be addressed before its commercialization: undesired dendrite growth of Li, and irreversible parasitic reactions between Li and electrolyte, etc.Stabilization of Li metal is essential for commercial application of Li metal anodes. In the past few years, several strategies have been developed to suppress Li dendrite growth and stabilize SEI formation during Li plating/stripping processes. Among these strategies, 3D current collectors showed its high potential in Li anode stabilization due to its much larger surface area, which can provide much more Li nucleation sites, alleviate volumetric changes of Li anode, and decrease practical current density. Thus, compared to flat Cu foil used in commercial Li-ion batteries, 3D Cu current collectors can facilitate uniform Li deposition, mitigate Li dendrite growth, and enhance Li cycling stability.[2]Our previous work reported a 3D porous Cu current collector fabricated via a facile one-step electrodeposition method directly on commercial Cu foil. [3] The fabricated 3D porous Cu current collector showed stable long-term cycling with a high areal capacity of 6 mAh/cm2 and no Li dendrite growth was observed during cycling process. However, for the one-step electrodeposition method, the thickness of the porous Cu deposition layer is limited. Thus, preparation of 3D porous Cu layers with both high thickness and high porosity is necessary to further improve the areal capacity of this current collector. Recently, we developed a new two-step electrochemical process to fabricate thick and porous Cu layer: a thick Cu-Zn alloy was first electrodeposited on commercial Cu foil, and Zn was then removed electrochemically, leaving a thick and highly porous 3D Cu layer. Compared to our previous method, this 3D Cu layer has a high thickness of ~14 um and porosity of ~72%. This new 3D Cu current collector can achieve stable Li cycling up to 230 h at high areal capacity of ~10 mAh/cm2 at a high current density of 10 mA/cm2, demonstrated its high commercial application potential in Li-metal batteries. Tarascon, J.M. and M. Armand, Issues and challenges facing rechargeable lithium batteries. Nature, 2001. 414(6861): p. 359-367.Yang, C.P., et al., Accommodating lithium into 3D current collectors with a submicron skeleton towards long-life lithium metal anodes. Nature Communications, 2015. 6.Ma, X., Z. Liu, and H. Chen, Facile and scalable electrodeposition of copper current collectors for high-performance Li-metal batteries. Nano Energy, 2019. 59: p. 500-507.