Magnesium batteries still encounter significant hurdles in their advancement, including
issues like rapid loss of capacity, absence of suitable electrolytes, passivation of the
magnesium anode, sluggish conversion reactions, and self-discharge. In this study, a
sulfur cathode incorporating carbon-based material S/C is devised and tested within a
magnesium battery framework utilizing a dual electrolyte system. This dual electrolyte
comprises two layers: one derived from a simple halogen-free electrolyte (HFE) and
another from a polymer layer interface (PLI). The HFE consists of magnesium nitrate
(Mg(NO3)2), magnesium triflate (Mg(CF3SO3)2), and succinonitrile (SN) dissolved in
acetonitrile (ACN)/tetraethylene glycol dimethyl ether (G4) cosolvents, supplemented
with dimethyl sulfoxide as a functional additive. The PLI, on the other hand, incorporates
polyvinylidene fluoride (PVDF), SN, and (Mg(CF3SO3)2), dissolved in methyl-2-
pyrrolidine (NMP)/G4 cosolvents, aimed at insulating the Mg anode surface from the
liquid electrolyte. The dual electrolyte demonstrates promising characteristics including
high ionic transference number ( 𝑡𝑚𝑔+2 = 0.9), excellent oxidation stability, low
overpotential, and consistent Mg stripping/plating for up to 100 hours. The Mg/S full cell
exhibits an impressive initial discharge/charge capacity of approximately 1312/432
mAhg-1
. Examination of sulfur cathodes at various electrochemical states indicates the
reversible conversion reaction of Mg2+ ions within the sulfur cathode framework.