A Passivation-Free Solid Electrolyte Interface Regulated by Magnesium Bromide Additive for Highly Reversible Magnesium Batteries

Abstract

Highly reversible Mg battery chemistry demands a suitable electrolyte formulation highly compatible with currently available electrodes. In general, conventional electrolytes form a passivation layer on the Mg anode, requiring the use of MgCl 2 additives that lead to severe corrosion of cell components and low anodic stability. Herein, for the first time, we conducted a comparative study of a series of Mg halides as potential electrolyte additives in conventional magnesium bis(hexamethyldisilazide)based electrolytes. A novel electrolyte formulation that includes MgBr 2 showed unprecedented performance in magnesium plating/ stripping, with an average Coulombic efficiency of 99.26% over 1000 cycles at 0.5 mA/cm 2 and 0.5 mAh/cm 2 . Further analysis revealed the in situ formation of a robust Mg anode−electrolyte interface, which leads to dendrite-free Mg deposition and stable cycling performance in a Mg−Mo 6 S 8 battery over 100 cycles. This study demonstrates the rational formulation of a novel MgBr 2 -based electrolyte with high anodic stability of 3.1 V for promising future applications.

Improving the Mg Sacrificial Anode in Tetrahydrofuran for Synthetic Electrochemistry by Tailoring Electrolyte Composition

“…Free Cl – , either generated through electrolyte conditioning or added in the form of metal chloride salts, can enable reversible Mg plating/stripping with low overpotential and high current density in MgCl 2 –AlCl 3 , − TFSI – , , and PF 6 – based electrolytes. Br – additives also improve the Mg plating/stripping behavior in Mg bis­(hexamethyldisilazide) based electrolyte . Additionally, both Br – and I – additives are able to improve voltage hysteresis in Mg–S batteries by decreasing the passivation layer on the Mg anode. , We hypothesize that the halides are readily adsorbed on Mg surfaces, as this process is predicted to be exothermic .…”

Enhanced interface stability of ammine magnesium borohydride by in situ decoration of MgBr2·2NH3 nanoparticles

“…22,23 For example, the addition of 20 mmol MgBr 2 in Mg(HMDS) 2 and TBABH 4 in dried DME lowers the energy barrier for Mg nucleation and promotes Mg homogeneous deposition on the magnesium electrode. 16 In the present study, the decoration of MgBr 2 ·2NH 3 nanoparticles with an average size of 3.7 nm may also lower the Mg nucleation barrier on the Mg anode and thus tremendously improve the compatibility with the Mg anode. Meanwhile, the interaction effect between conductors and insulating additives, such as oxides and polymers, which enhances the ionic migration due to the formation of active interfaces and the creation of fresh ionic environment, has been often reported for solid-state electrolytes.…”

“…Interfacial stability is a crucial factor influencing the performance of batteries. [14][15][16] Regarding the Mg(BH 4 ) 2 -based solidstate electrolytes, breaking the [BH 4 ] tetrahedral cages in Mg(BH 4 ) 2 could improve the ionic conductivity but also lower the stability. For instance, some electrolytes (e.g., Mg(BH 4 ) 2 Á (NH 3 BH 3 ) 2 , 9 Mg(BH 4 ) 2 ÁCH 3 NH 2 17 ) allow Mg stripping/plating only at a low current density r10 mA cm À2 , and decompose on the anode surface at higher current density of e.g., 0.1 mA cm À2 forming a passivation layer and hindering the Mg 2+ migration.…”

“…Interfacial stability is a crucial factor influencing the performance of batteries. 14–16 Regarding the Mg(BH 4 ) 2 -based solid-state electrolytes, breaking the [BH 4 ] tetrahedral cages in Mg(BH 4 ) 2 could improve the ionic conductivity but also lower the stability. For instance, some electrolytes ( e.g.…”

Chloride-Free Electrolyte Based on Tetrabutylammonium Triflate Additive for Extended Anodic Stability in Magnesium Batteries

“…Figure a shows the deconvoluted XPS spectra of elements present on the Mg anode surface cycled with different electrolytes. The deconvoluted peaks from C 1s spectra were indexed as C–C (284.8 eV), O–C–O (285.53 eV), CO (286.54 eV), O–CO (287.32 eV), and C 2 O 4 2– /CO 3 2– (289.02 eV). ,, The O 1s spectra confirm the existence of Mg–O (529.80 eV), Mg–O (vacancy) (530.93 eV), Mg­(OH) 2 (531.6 eV), C–O–C (532.76 eV), CO 3 (533.26 eV), and MgCO 3 (533.7 eV). From the C 1s and O 1s XPS spectra, we note that the anodes cycled in Mg­(OTf) 2 + Mg­(HMDS) 2 + TBAOTf and Mg­(HMDS) 2 + TBAOTf electrolytes possess higher organic species (ether and ester moieties) which can help in preventing the anode from passivation. , Conversely, anodes cycled in the Mg­(OTf) 2 + TBAOTf electrolyte have reduced organic species, which may be the reason for the short cycling life (Figures S8a and S10a).…”