Stripping and plating magnesium metal anode in bromide-based non-nucleophilic electrolytes.

We present here a new electrolyte formulation of non-nucleophilic HMDS magnesium containing bromide as halide instead of chloride, obtained via a simple and straightforward synthesis route and investigate the electrochemistry of magnesium through plating and stripping in three different HMDSBr-based electrolytes: Mg(HMDS)Br, Mg(HMDS)Br-BEt3 and Mg(HMDS)Br-AlEt3 dissolved in THF. We determine the different magnesium species in the electrolytes using NMR. Weak electron-withdrawing Lewis acids, BEt3 and AlEt3 were used intentionally and their impacts investigated. Contrary to expectation, substitution of chloride by bromide does not drastically narrow the electrochemical stability window. HMDSBr-based electrolytes demonstrate long-term (1000 cycles) stable reversibility and highly efficient (⁓99%) magnesium plating/tripping without high ratio of bromide compared to the MgHMDSCl-based electrolyte. The aprotic electrolyte shows furthermore comparatively high anodic stability (⁓2.4 V vs Mg/Mg2+) and high ionic conductivity of 1.16 mS cm-1 at room temperature. Plating of magnesium with low overpotential (<188 mV) reveals morphology dependence on the electrolyte type with a shiny metallic homogenous layer, thus suggesting a rational balance between nucleation and growth process in HMDSBr-based electrolyte. PMID: 32243696 [PubMed - as supplied by publisher]
Source: ChemSusChem - Category: Chemistry Authors: Tags: ChemSusChem Source Type: research