A Bismuth-Based Protective Layer for Magnesium Metal Anode in Noncorrosive Electrolytes

Abstract

Rechargeable magnesium (Mg) metal batteries are provided with potential advantages over lithium counterparts with respect to volumetric capacity and natural abundance (equivalent to low cost and sustainability). However, Mg metal anodes suffer from surface passivating behavior among numerous conventional Mg electrolytes, leading to irreversible Mg plating/stripping behavior. Herein, a modified Mg metal anode with a bismuth (Bi)-based artificial protective layer has been obtained via a facile solution process (soaking briefly in bismuth trichloride solution). This Bi-based protective layer is mainly composed of ion-conducting Bi metal and corresponding alloy and electronically insulating magnesium chloride. Various electrochemical tests and interface characterizations have proved that the protected Mg electrodes effectively inhibit the harmful parasitic reaction between Mg metal and noncorrosive Mg electrolyte, which further enables suppression of uneven growth during repeated Mg stripping/plating. More importantly, the assembled Mg–Cu2–x S and Mg–O2 full batteries utilizing the as-modified Mg anodes all deliver remarkably improved performance owing to the superior protection properties of a Bi-based artificial layer. These novel findings will inspire lot of efforts to modify the Mg metal anode with targeted surface coatings for high-performance rechargeable Mg batteries.

Room‐temperature metal–sulfur batteries: What can we learn from lithium–sulfur?

“…Only until recent years have there been focused research efforts on exploring Mg-ion conductive SEI layers. [139][140][141][142] Approaches such as the ex-situ design of Mg 3 Bi 2 artificial layer, 139 the in-situ formation of SEI layers via addition of electrolyte additives (e.g., iodine and bulky anion lithium salt), 140,141 and the cyclization of polyacrylonitrile polymer with magnesium triflate on the Mg surface 142 effectively suppressed the passivation of Mg anodes upon cycling. Another encouraging point is that the reversible plating/striping of multivalent metal anodes can be realized through appropriate design of electrolytes.…”

“…In contrast to a large number of Li + ionic conductive layers reported for the Li anode, there are much less reports on ionic conductive layers for multivalent metal anodes. Only until recent years have there been focused research efforts on exploring Mg‐ion conductive SEI layers 139–142 . Approaches such as the ex‐situ design of Mg 3 Bi 2 artificial layer, 139 the in‐situ formation of SEI layers via addition of electrolyte additives (e.g., iodine and bulky anion lithium salt), 140,141 and the cyclization of polyacrylonitrile polymer with magnesium triflate on the Mg surface 142 effectively suppressed the passivation of Mg anodes upon cycling.…”

Current Design Strategies for Rechargeable Magnesium-Based Batteries

“…Recently, Cui and co-workers also designed Bi-based artificial protecting layers on Mg metal anodes via a facile solution strategy. , In noncorrosive Mg­(TFSI) 2 -based electrolytes, this artificial layer could avoid the parasitic reactions with Mg metals. In APC electrolytes, this protective layer could facilitate the Mg atoms adsorption and diffusion.…”

Non-passivating Anion Adsorption Enables Reversible Magnesium Redox in Simple Non-nucleophilic Electrolytes

“…As shown in the cycling stability test (the gray line in Figure S3), after 177 h cycling, the voltage of Mg–Mg cells with pristine electrolyte suddenly dropped to 88 mV because of the internal short circuit induced by three-dimensional growth of Mg deposits . The reason why short-circuited Mg–Mg cells still retained a considerable polarization is the strong tendency of the Mg anode to be passivated. , The high-dimensional Mg deposits will be instantaneously covered by a passivation layer with high resistance, resulting in a much larger polarization than short-circuited Li–Li cells. , This phenomenon was also investigated in previous reports. , Therefore, the sudden voltage drop during galvanostatic testing was regarded as the occurrence of a soft short circuit . Moreover, exposing the pristine electrolyte to air results in an extremely short cycle life (<10 h, the gray line in Figure d).…”

“…GeCl 4 and SnCl 2 enabled reversible Mg reaction via the in situ formation of a Ge/Sn-based protective layer. However, a high concentration of additives was required (0.1–0.4 M) because the Ge/Sn-based interface can be easily peeled off, hence exposing the fresh Mg surface and resulting in continuous consumption of the Mg anode . Moreover, the compatibility between the reported additives and electrophilic organic cathodes is yet to be confirmed.…”