期刊
ACS APPLIED MATERIALS & INTERFACES
卷 11, 期 42, 页码 38689-38696出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.9b11888
关键词
magnesium battery; electrolytes; diglyme; Mg(TFSI)(2); C-13 NMR; DFT NMR calculations
资金
- Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub - U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (BES)
- Department of Energy's Office of Biological and Environmental Research at Pacific Northwest National Laboratory (PNNL)
- DOE, Battelle Memorial Institute [DE-AC06-76RLO 1830]
Mg batteries have been proposed as potential alternatives to lithium-ion batteries because of their lower cost, higher safety, and enhanced charge density. However, the Mg metal readily oxidizes when exposed to an oxidizer to form a thin MgO passivation surface layer that blocks the transport of Mg2+ across the solid electrode-electrolyte interface (SEI). In this work, the adsorption and thermal decomposition of diglyme (G2) and electrolytes containing Mg(TFSI)(2) in G2 on 10 nm-sized MgO particles are evaluated by a combination of in situ C-13 single-pulse, surface-sensitive H-1-C-1(3) cross-polarization (CP) magic-angle spinning (MAS) nuclear magnetic resonance, and quantum chemistry calculations. At 180 degrees C, neat G2 decomposes on MgO to form surface-adsorbed -OCH3 groups that are captured as a distinctive peak located at about 50 ppm in the CP/MAS spectrum. At low Mg(TFSI)(2) salt concentration, the main solvation structure in this electrolyte is solvent-separated ion pairs without extensive Mg-TFSI contact ion pairs. G2, likely including a small amount of G2-solvated Mg2+, adsorbs onto the MgO surface. At high Mg(TFSI)(2) salt concentrations, contact ion pairs between Mg and TFSI are formed extensively in the solution with the first solvation shell containing one pair of Mg-TFSI and two G2 molecules and the second solvation shell containing up to six G2 molecules, namely, MgTFSI(G2)(2)(G2)(6)(+). In the presence of MgO, MgTFSI(G2)(2)(G2)(6)(+) adsorbs onto the MgO surface. At 180 degrees C, the MgO surface stimulates a desolvation process converting MgTFSI(G2)(2)(G2)(6)(+) to MgTFSI(G2)(2)(+) and releasing G2 molecules from the second solvation shell of the MgTFSI(G2) 2 (G2)(6)(+) cluster into the solution. MgTFSI(G2)(2)(+) and MgTFSI(G2)(2)(G2)(6)(+) tightly adsorb onto the MgO surface and are observed by H-1-C-13 CP/MAS experiments. The results contained herein show that electrolyte composition has a directing role in the species present on the electrode surface, which has implications on the structures and constituents of the solid-electrolyte interface on working electrodes and can be used to better understand its formation and the failure modes of batteries.
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