Performance study of magnesium–sulfur battery using a graphene based sulfur composite cathode electrode and a non-nucleophilic Mg electrolyte

Abstract

Here we report for the first time the development of a Mg rechargeable battery using a graphene-sulfur nanocomposite as the cathode, a Mg-carbon composite as the anode and a non-nucleophilic Mg based complex in tetraglyme solvent as the electrolyte. The graphene-sulfur nanocomposites are prepared through a new pathway by the combination of thermal and chemical precipitation methods. The Mg/S cell delivers a higher reversible capacity (448 mA h g(-1)), a longer cyclability (236 mA h g(-1) at the end of the 50(th) cycle) and a better rate capability than previously described cells. The dissolution of Mg polysulfides to the anode side was studied by X-ray photoelectron spectroscopy. The use of a graphene-sulfur composite cathode electrode, with the properties of a high surface area, a porous morphology, a very good electronic conductivity and the presence of oxygen functional groups, along with a non-nucleophilic Mg electrolyte gives an improved battery performance.

Application of a Sulfur Cathode in Nucleophilic Electrolytes for Magnesium/Sulfur Batteries

“…The fore-mentioned processes correspond to the reduction of the solid cyclo-S 8 to dissolved polysulfide MgS 8 (which is subsequently reduced to MgS 6 and then to MgS 4 ), MgS 4 to solid MgS 2 , and then MgS 2 to MgS. 8,14 The first charge curve exhibits a voltage plateau at 1.3 V and a sloping voltage profile from 1.6 V to 1.7 V, which correspond to the conversion of MgS/MgS 2 to low-order polysulfuides and further to high-order polysulfuides or sulfur. In the following discharge curves, the stable voltage plateau at 1.1 V for main capacity contribution shortens obviously.…”

“…13 On the other hand, some efforts have also been made to address the dissolution of magnesium polysufide (MgS x , x ≥ 4) by using a sulfur-carbon composite 8,11,14 or fabricating new elemental selenium (Se) and selenium-sulfur solid solution (SeS 2 ) cathodes to physically restrain polysulfides, facilitate electron transport, and provide free-space to accommodate the volume change in S/polysulfides.…”

“…12 Furthermore, a non-nucleophilic Mg electrolyte based on (HMDS) 2 Mg that uses lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as an additive was proposed to improve the reversibility of Mg/S batteries by activating inactive MgS and MgS 2 through Li + . 13 On the other hand, some efforts have also been made to address the dissolution of magnesium polysufide (MgS x , x ≥ 4) by using a sulfur-carbon composite 8,11,14 or fabricating new elemental selenium (Se) and selenium-sulfur solid solution (SeS 2 ) cathodes to physically restrain polysulfides, facilitate electron transport, and provide free-space to accommodate the volume change in S/polysulfides. 15 This study reported on the feasibility of a sulfur cathode in a typical nucleophilic electrolyte, (PhMgCl) 2 -AlCl 3 /THF, 16 which is easily prepared and possesses high anodic stability and reversibility of Mg deposition-dissolution, by simply using Cu as the cathode current collector.…”

Magnesium-sulfur battery: its beginning and recent progress

“…10(a)]. Interestingly, the overcharging behavior is much less significant compared with the previous [29,32] 3.9 ∼2 ∼100 Yes 260@20/20 [32] 1000@71/30 [33] 236@20/50 [34] 800@167/20 [ [47,53] 3.1 [47] , 2.5 [53] 2 [47] , 8.5 [53] 99 Yes 70@17/20 [53] Mg(TFSI) 2 Prospective Article reports and an overpotential during charge and discharge was <0.4 V. The Mg-S cells were cycled for 30 times with capacity retention >86% [ Fig. 10(b)].…”

“…This is the obvious reason for the superior electrochemical performance when compared with the electrolyte generated from HMDSMgCl-AlCl 3 containing several anionic species in form HMDS n AlCl 4−n − (n = 1-3). [28] Owing to the favorable electrochemical and chemical properties and its simplicity in preparation, this type of electrolyte has been employed in different Mg battery systems with both intercalation and conversion cathodes, including Mo 6 S 8 , [29] vanadium oxychloride (VOCl), [31] S, [32][33][34][35] Se, [36] and iodine. [37] Fluorinated alkoxide-based electrolytes…”