Modification of a Cu Mesh with Nanowires and Magnesiophilic Ag Sites to Induce Uniform Magnesium Deposition.

The nature of dendrite-free magnesium (Mg) metal anodes is an important advantage in rechargeable magnesium batteries (RMBs). However, this traditional cognition needs to be reconsidered due to inhomogeneous Mg deposits under extreme electrochemical conditions. Herein, we report a three-dimensional (3D) Cu-based host with magnesiophilic Ag sites (denoted as "Ag@3D Cu mesh") to regulate Mg deposition behaviors and achieve uniform Mg electrodeposition. Mg deposition/stripping behaviors are obviously improved under the cooperative effect of nanowire structures and Ag sites. The test results indicate that nucleation overpotentials are reduced distinctly and cycling performances are prolonged, suggesting that the general rules of 3D structures and affinity sites improve the durability and reversibility of Mg deposition/stripping. Besides, a unique concave surface structure can induce Mg to deposit into the interior of the interspace, which utilizes Mg more efficiently and leads to improved electrochemical performances with limited Mg content. Furthermore, in situ optical microscopic images show that the Ag@3D Cu mesh can attain a smooth surface, nearly without Mg protrusions, under 8.0 mA cm ^-2 , which prevents premature short circuits. This report is a pioneering work to demonstrate the feasibility of modification of Cu-based current collectors and the necessity of functional current collectors to improve the possibility of practical applications for RMBs.