Epitaxial Electrocrystallization of Magnesium via Synergy of Magnesiophilic Interface, Lattice Matching, and Electrostatic Confinement

Abstract

Rechargeable magnesium batteries are particularly advantageous for renewable energy storage systems. However, the inhomogeneous Mg electrodeposits greatly shorten their cycle life under practical conditions. Herein, the epitaxial electrocrystallization of Mg on a three-dimensional magnesiophilic host is implemented via the synergy of a magnesiophilic interface, lattice matching, and electrostatic confinement effects. The vertically aligned nickel hydroxide nanosheet arrays grown on carbon cloth (abbreviated as "Ni(OH) 2 @CC") have been delicately designed, which satisfy the essential prerequisite of a low lattice geometrical misfit with Mg (about 2.8%) to realize epitaxial electrocrystallization. Simultaneously, the ionic crystal nature of Ni(OH) 2 displays a periodic and hillock-like electrostatic potential field over its exposed facets, which can precisely capture and confine the reduced Mg 0 species onto the local electron-enriched sites at the atomic level. The Ni(OH) 2 @CC substrate undergoes sequential Mg-ion intercalation, underpotential deposition, and electrocrystallization processes, during which the uniform, lamellar Mg electrodeposits with a locked crystallographic orientation are formed. Under practical conditions (10 mA cm −2 and 10 mAh cm −2 ), the Ni(OH) 2 @ CC substrate exhibits stable Mg stripping/plating cycle performances over 600 h, 2 orders of magnitude longer than those of the pristine copper foil and carbon cloth substrates.

Solvent Molecule Design Enables Excellent Charge Transfer Kinetics for a Magnesium Metal Anode

“…Lithium-ion batteries have ushered in a revolution ranging from portable electronic equipment to electric vehicles. − However, their further large-scale application is still hampered by unsatisfied energy density, safety anxiety, and high cost. − Therefore, exploration of an alternative battery system has attracted much attention recently. − Among numerous candidates, rechargeable magnesium batteries (RMBs) are expected to become a potential next-generation energy storage system because of their following advantages, such as high volumetric energy density (3833 mAh cm –3 ), − the intrinsic property of a low tendency to dendritic formation, and low reactivity with air and moisture. − In addition, abundant Mg resources in the earth’s crust can relieve the concern about the limitation of metal resources effectively. − Unfortunately, the bivalent nature causes an unwished high charge density for the Mg 2+ ion, leading to a strong electrostatic interaction and an extremely sluggish Mg 2+ ion diffusion kinetic in most materials. − For this reason, in sharp contrast with Li metal, the solid-electrolyte interphase (SEI) on Mg metal anode is not Mg 2+ -conducting and is even called a passivation layer for RMBs, showing large overpotentials and irreversible Mg plating/stripping behaviors. Typically, Mg metal is passivated in traditional electrolytes which contain conventional polar solvents (such as ethylene carbonate and acetonitrile) and simple Mg 2+ salts (such as Mg­(TFSI) 2 and Mg­(ClO 4 ) 2 ), leading to incompatibility with a Mg metal anode, even though these traditional electrolytes show attractive advantages of commercial accessibility and low cost. , This fatal obstacle brings huge challenges to the research of RMBs and hinders the development of RMBs seriously.…”

MXene‐Based Anode‐Free Magnesium Metal Battery

“…The above remarkable cycling performance greatly outperforms those of previously reported 2D and 3D current collectors, especially under high‐current densities and high DOD conditions. [ 12b,c,13 ] The high CE of Ti 3 C 2 T x MXene film plays an indispensable role in reducing the irreversible consumption of active materials in a battery with limited Mg resources.…”

Boosting Magnesium Ion Storage Behavior via Heteroelement Doping in a Porous Tunnel Framework Cathode for Aqueous Mg‐Ion Batteries

“…Aqueous magnesium ion battery (AMIB) has attracted aggressive efforts due to the endowed virtue of its non-flammable and nonpoisonous electrolyte, 5 th reserves in the earth's crust, and low cost (Li metal is 30 times more expensive than Mg metal). [2][3][4][5][6][7] In addition, the radius of Mg 2 + is analogous to that of Li + , and Mg 2 + is the divalent current carrier that can transmit double electrons than Li + during the cycling process. [8] Accordingly, an aqueous Mg-ion battery is one of the most promising alternative candidates for Li-ion batteries.…”

“…The reasons mentioned above inhibit the application in the large‐scale grid. Aqueous magnesium ion battery (AMIB) has attracted aggressive efforts due to the endowed virtue of its non‐flammable and nonpoisonous electrolyte, 5 th reserves in the earth‘s crust, and low cost (Li metal is 30 times more expensive than Mg metal) [2–7] . In addition, the radius of Mg 2+ is analogous to that of Li + , and Mg 2+ is the divalent current carrier that can transmit double electrons than Li + during the cycling process [8] .…”