A Simple Cl^–-Free Electrolyte Based on Magnesium Nitrate for Magnesium–Sulfur Battery Applications

Abstract

The magnesium–sulfur (MgS) battery is a promising alternative to the post-lithium battery because of its low-cost construction, eco-friendliness, high theoretical energy density, and safety. However, the lack of simple compatible electrolytes, self-discharge, polysulfide shuttle effect, and the slow conversion reaction pathway still limit its practical applications. Here, we propose a simple halogen-free electrolyte (HFE) based on Mg­(NO3)2 dissolved in the cosolvent of acetonitrile (ACN) and tetraethylene glycol dimethyl (G4) that applies to a Mg/S full cell. The as-prepared Mg-ion electrolyte exhibits efficient Mg plating/stripping performance, high anodic stability (vs Mg/Mg2+), and a high ionic conductivity of ∼10–4 S cm–1 at 313 K. Chronoamperometry (CA), scanning electron microscopy, and energy-dispersive spectroscopy examinations report that the HFE supports flat, dendrite-free, and translucent Mg deposits. Polymer layer interface (PLI)-based polyvinylidene fluoride (PVDF) and Mg­(O3SCF3)2 have been designed to isolate the surface of the Mg anode from the liquid electrolyte. A sulfur cathode with the anchoring materials of silicon carbide and barium titanate-based material has been designed and characterized. The Mg/S battery has been constructed with an initial discharge capacity of up to 1200 mAh g–1, and it has retained a reversible capacity at 100 mAh g–1 after 10 cycles. This study offers a pivotal role in designing a promising HFE candidate for a high-performance MgS battery.

Determination of Average Coulombic Efficiency for Rechargeable Magnesium Metal Anodes in Prospective Electrolyte Solutions

“…Nonetheless, these average CE values are highly impressive for Cl-free systems and should not be taken for granted. 53,55 Furthermore, the increased anodic stability of Cl-free electrolyte solutions makes future efforts to enhance their CE very compelling.…”

“…In recent years, a variety of halide-free solutions have been investigated to demonstrate efficient Mg deposition behavior. ,− Fichtner et al proposed that cycling of Mg metal cells could be accomplished using magnesium tetra kis­(hexafluoroisopropyloxy)­borate (Mg­[B­(HFIP) 4 ] 2 ). , According to Dlugatch et al, this solution necessitates a thorough conditioning process to remove reactive contaminants that cause unavoidable passivation and deactivation of the Mg metal . This is unsurprising given that all Grignard-free electrolyte solutions lack strongly reductive agents capable of scavenging the different contaminants.…”

“…For example, the impact of irreversible chemical and electrochemical side reactions is less notable in short and shallow deposition/stripping cycles than in long and deep cycles. Nonetheless, these average CE values are highly impressive for Cl-free systems and should not be taken for granted. , Furthermore, the increased anodic stability of Cl-free electrolyte solutions makes future efforts to enhance their CE very compelling.…”

Evolution of the Dynamic Solid Electrolyte Interphase in Mg Electrolytes for Rechargeable Mg-Ion Batteries

“…The most easily obtained halogen-free electrolyte is a magnesium bis­(trifluoromethanesulfonyl) imide [Mg­(TFSI) 2 ]-based electrolyte that possesses multidentate anions with large charge delocalization, offering a facile way to prepare Mg electrolytes that achieve reversible Mg deposition. − Despite the significant advancements in the development of the halogen-free, less-corrosive Mg electrolytes, , there is a dire need to establish a fundamental understanding of the chemical and electrochemical processes at the electrolyte/electrode interface. The less-explored interfacial evolution governs the performance and longevity of the Mg battery.…”

Hydride-Enhanced Plating and Stripping of Aluminum from Tri-flate -Based Organic Electrolytes

“…32 AHF electrolytes take advantage of the fact that the halogen atoms are sequestered in a polyatomic anion, 37 which renders these systems free from the intrinsically corrosive haloaluminate complexes (for example, Al 2 Cl 7 -, AlCl 4 -, and solvated AlCl 3 ) and free halogen anions (for example, F -, Brand Cl -). One such example of these polyatomic anions is the trifluoromethanesulfonate (OTF -), which is known to be exceptionally stable to both oxidative and reductive cleavage, 38 thus, making OTF --electrolytes a suitable candidates for AHF systems and of potential application in rechargeable Mg [39][40][41] and Al batteries. 42,43 Thus far, only a handful of AHF organic electrolytes for rechargeable Al batteries have been reported.…”