A non-nucleophilic gel polymer magnesium electrolyte compatible with sulfur cathode

Abstract

Magnesium/sulfur battery (Mg/S) has recently received wide attention due to its high theoretical energy density (3,260 Wh/L) and low cost. To further improve its safety and flexibility, developing a polymer electrolyte that can be compatible with both electrophilic S and Mg is critical. Here, we report a magnesium chloride-(fluorinated tetraethylene glycolic)borate (MgCl-FTGB) based non-nucleophilic, gel-type polymer electrolyte for Mg/S battery via a facile synthetic method through commercially available reagents. This electrolyte coupled with glass fiber allows reversible Mg deposition/dissolution (100% coulombic efficiency) with low polarization (500 μA/cm 2 , 300/300 mV), and shows a wide electrochemical window of 4.8 V (vs. Mg/Mg 2+ ). Mg/S battery assembled with this electrolyte can cycle over 50 times with a high specific discharge capacity retention of over 1,100 mAh/g.

Dual Role of Mo6S8 in Polysulfide Conversion and Shuttle for Mg–S Batteries

“…To evaluate the interaction between Mo 6 S 8 and the dissolved magnesium polysulfide, an adsorption experiment was conducted using a magnesium polysulfide (MgS n ) solution. The solution was prepared according to a reported procedure [ 11c ] and the corresponding photograph of the prepared MgS n solution is presented in Figure S5b of the Supporting Information. A simple visual adsorption test was performed by dispersing the Mo 6 S 8 powder in the MgS n solution.…”

“…The magnesium tetrakis(hexafluoroisopropyloxy)borate (Mg[B(hfip) 4 ] 2 ) electrolyte was synthesized in a reaction between Mg(BH 4 ) 2 and hexafluoroisopropanol in DME as reported. [ 11c ] 0.3 м electrolyte solution was prepared by dissolving proper amount of magnesium salt in DME. And the concentration is based on the molecular weight of Mg[B(hfip) 4 ] 2 .…”

“…[ 8 ] Nevertheless, similar to the Li–S battery chemistry, due to the known “shuttle” phenomena of polysulfide, Mg–S batteries suffer from continuous self‐discharge, rapid capacity decay and short cell life. [ 3b,8a,9 ] Pioneer works have been devoted to tackling the problematics related to the dissolution and migration of polysulfide species in Mg–S batteries, including designing sulfur cathode architectures, [ 10 ] electrolyte compositions, [ 4,11 ] and functional separators. [ 12 ]…”

Current Design Strategies for Rechargeable Magnesium-Based Batteries

“…Zhang and co-workers also developed a nonnucleophilic gel polymer electrolyte for Mg−S batteries. 116 The NG-NCNT@NCS@S cathode on a copper current collector could cycle for 50 times with high capacity of 1000 mAh g −1 , demonstrating its superiority. The selenium sulfide (SeS x ) materials showed both the beneficial high electronic conductivity of Se and high specific capacity of S, which were proposed by Cui and co-workers as a promising cathode for rechargeable Mg batteries.…”

Recent Advances in Emerging Non‐Lithium Metal–Sulfur Batteries: A Review

“…[178] They achieved a discharge potential of ≈1.65 V for Mg-S batteries, close to the theoretical thermodynamic value, and a long upper voltage plateau with a relatively higher capacity was obtained. To date, various Mg compounds, such as [(HMDS) 2 Mg], [178][179][180][181] and MgCl-based, [182,183] have been developed as non-nucleophilic Mg electrolytes. Among them, the (HMDS) 2 Mg salt has several disadvantages, including corrosion problems of current collectors and inhibition of Mg transport.…”