Microstructure and Chemistry of Electrodeposited Mg Films

Abstract

We describe the structure, morphology, and chemistry of Mg films that were electrodeposited using different electrolytes (magnesium aluminum chloride complex (MACC), magnesium bis(trifluoromethylsulfonyl)imide (Mg-TFSI) and magnesium triphenoxyaluminate (MTPA)). The microstructure and chemistry of the Mg films, along with their overall cycling efficiency, showed a strong dependence on electrolyte chloride content. The films formed with the higher chloride concentration electrolytes (MACC and MTPA) yielded large and columnar grain structures with a strong [001] texture. The films formed using chloride-free TFSI that only has an 80% cycling efficiency showed much smaller grains and a more random texture. Electrochemically conditioned MACC and MTPA also led to smaller amounts of impurity being incorporated in the films than TFSI. The impurities detected in the form of Mg complexes such as Mg-O, Mg-H, Mg-OH, Mg-C, and elemental impurities (O, C, Cl, Al) tend to form discontinuous films orthogonal to the [001] direction.

Advancing Electrolyte Solution Chemistry and Interfacial Electrochemistry of Divalent Metal Batteries

“…(002) and (100) pole figures and SEM images of Mg layers deposited on Au (111) using (a, b, g) MACC, (c, d, h) MTPA, and (e, f, i) TFSI electrolytes respectively. Reproduced with permission from [78] . Copyright 2016 The Electrochemical Society.…”

“…Besides, the effect of chloride content on electrolyte chemistry, the microstructure, and the surface chemistry of electrodeposited Mg was systematically studied using different analytical methods. [78] Three different electrolytes were chosen, i. e., Mg aluminum chloride complex (MACC: MgCl 2 + AlCl 3 ) with the highest chloride content, Mg triphenoxyaluminate (MTPA: PhMgCl + Al(OPh) 3 in 4 : 1 ratio), and TFSI (Mg(TFSI) 2 in G2) with no chloride. The microstructure and chemistry of the Mg films, along with their overall cycling efficiency, showed a strong dependence on chloride contents in the electrolytes.…”

“…Reproduced with permission from. [78] Copyright 2016 The Electrochemical Society. mechanism on divalent metal anodes, and the insertion mechanism of electroactive cation species into high voltage cathodes will advance the fundamental understanding that will establish the scientific basis for the development of practical rechargeable divalent batteries.…”

“…Since this surface layer is not formed by the irreversible decomposition of the electrolyte formulation, the EAC electrolyte maintains dynamic reversible interphase. Besides, the effect of chloride content on electrolyte chemistry, the microstructure, and the surface chemistry of electrodeposited Mg was systematically studied using different analytical methods [78] . Three different electrolytes were chosen, i. e ., Mg aluminum chloride complex ( MACC : MgCl 2 +AlCl 3 ) with the highest chloride content, Mg triphenoxyaluminate ( MTPA : PhMgCl+Al(OPh) 3 in 4 : 1 ratio), and TFSI (Mg(TFSI) 2 in G2 ) with no chloride.…”

Al2O3 Thin Films on Magnesium: Assessing the Impact of an Artificial Solid Electrolyte Interphase

“…The high overpotential in Mg (TFSI) 2 electrolyte was attributed in some studies to the TFSI − anion's instability at the Mg anode which causes it to degrade and form MgS as well as MgF 2 (Yoo et al, 2017;Ding et al, 2018;Jay et al, 2019). Electrolytes containing the Mg (TFSI) 2 salt also demonstrate sensitivity to water, which can aid solvent decomposition (Yu et al, 2017) and passivate the Mg anode interface (Bachhav et al, 2016). While the degradation layer is not completely passivating, it causes large voltage hysteresis issues in full-cell systems (Meng et al, 2019).…”