摘要
Rechargeable magnesium (Mg) batteries have attracted increasing attention because Mg provides a high theoretical volumetric capacity (3,833 mAh/cm 3 ), is abundant in the Earth’s crust, low-cost, and environmentally friendly, and shows a reduced tendency to form dendrites during charging [1]. Although there has been steady progress in developing electrolytes and compatible cathode materials for rechargeable Mg batteries, the microstructural evolution of Mg metal anodes has remained relatively understudied. However, gaining a comprehensive understanding of the anode evolution is as critical for advancing rechargeable Mg battery technology. In recent years, anode-free configurations have been proposed as a means to further enhance the energy density of rechargeable batteries [2]. In these systems, the conventional bulk metal anode is removed, and a metallic layer is instead electrodeposited onto the current collector during the first charging cycle. Under such a design for rechargeable Mg batteries, the microstructure of the initially deposited Mg layer becomes a key factor controlling the performance and cycle life of the Mg anode during subsequent cycles. Therefore, in this work, we compared the microstructure of Mg layers electrodeposited onto copper (Cu) current collectors in different electrolytes under various deposition conditions. Electrodeposition of Mg was carried out using a Cu current collector||Mg||Mg cell in an all-phenyl complex (APC) electrolyte, a phenolate-based magnesium complex (PMC) electrolyte, and an all-ethyl complex (AEC) electrolyte. After electrodeposition, the surface morphology and crystal orientation of the Mg layers were examined using SEM/EDS and XRD. In addition to examining the deposited Mg microstructures, this study also measured the electrochemical properties of the electrolytes to establish a link between the electrolyte properties and the microstructures of the electrodeposited Mg layer. Cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA) were used to assess the electrolyte’s reversibility, deposition overpotential, limiting current density, reaction impedances, and diffusion coefficient of the Mg complex ions. Together, these electrochemical analyses help build a comprehensive understanding of how electrolyte properties affect the Mg electrodeposition processes and the resultant Mg layer microstructure. References: [1] Muldoon J, Bucur CB, Gregory T. Fervent hype behind magnesium batteries: an open call to synthetic chemists-electrolytes and cathodes needed. Angew Chem Int Ed 2017;56:12064–84. [2] Tian Y, An Y, Wei C, Jiang H, Xiong S, Feng J, Qian Y. Recently advances and perspectives of anode-free rechargeable batteries. Nano Energy 2020;78:105344.