Mxenes As Sulfur Host Material for Magnesium-Sulfur Batteries

Magnesium-sulfur batteries offer the possibility of combining highly abundant and cheap elements with high energy density. Despite recent significant improvements, critical aspects still in need of optimization include electrolyte and cathode design [1]. The latter involves finding a cathode composition that prevents the polysulfide shuttle mechanism, which deteriorates the capacity retention, while at the same time providing high electrical conductivity to the insulating sulfur. Since its invention in 2011 [2], the MXene family of materials has attracted much attention for a range of applications, mostly due to its high electrical conductivity combined with hydrophilicity and good mechanical strength [3]. Recently, MXene-based sulfur composite cathodes have demonstrated promising performance for lithium-sulfur batteries [4]. Here, titanium- and vanadium-based MXenes have been investigated as sulfur host material for magnesium-sulfur batteries. MXenes were obtained by leaching out the aluminum from the corresponding MAX phase, which was confirmed by XRD and EDS. After sulfur loading, the MXene-sulfur composite was tested as cathode with a Mg anode, glass fiber separator and different Mg electrolytes, showing promising electrochemical performance. Optimization of the MXene surface termination, the sulfur infiltration method and the electrolyte is currently being investigated, with an aim of lowering the overpotential, improving capacity retention and increasing the sulfur utilization. References: [1] Z. Zhao-Karger, M. Fichtner, MRS Communications (2017), 7, 770–784.[2] Naguib et al., Adv. Mater. 23 (2011) 4248-4253.[3] B. Anasori, M. R. Lukatskaya, Y. Gogotsi, Nature Reviews Materials 2 (2017) 16098, 1-17.[4] Gao et al., Small (2018), 14, 1802443.