Solid Electrolyte Interphase Growth on Mg Metal Anode: Case Study of Glyme‐Based Electrolytes

Abstract

Batteries based on Mg metal anodes promise high capacities and dendrite‐free metal deposition, making them one of the most promising candidates for post‐Li(Na) energy‐storage technologies. Herein, for the first time, the fundamental issue of solid electrolyte interphase (SEI) growth under open circuit voltage (OCV) conditions in a Mg salt–triglyme electrolyte as observed by electrochemical impedance spectroscopy (EIS) is dealt with. The EIS suggests that SEIs are liquid/solid composites where ion transport occurs predominantly via diffusion in the encapsulated liquid. Depending on the salt choice, volume percent of the liquid part of SEI is varied up to one order of magnitude. The surface limiting reaction growth mechanism proceeds through SEI densification or as a consequence of inherent mechanical instabilities.

Capturing the swelling of solid-electrolyte interphase in lithium metal batteries

“…This observation provides a practical method to quantitatively measure the electrolyte uptake of SEI in the liquid environment. Alternatively, this can also be viewed as SEI porosity at (sub)-nanoscale, as projected in earlier SEI models ( 27 – 30 ). By measuring the swelling ratio, defined as the thickness ratio of w-SEI and d-SEI, we can estimate the amount of electrolyte in the SEI region.…”

Phase Transfer‐Mediated Degradation of Ether‐Based Localized High‐Concentration Electrolytes in Alkali Metal Batteries

“…Notably, Popovic's recent studies have revealed the porous SEIs and further growth mechanism in metal anode cases with ether-based electrolytes. [16,17] The factor of porous SEI may also contribute to the K metal anode degradation in the ether-based LHCE system because it provides the chance for electrolyte penetration and facilitates K À /e s À formation. As a result, the side reactions between the e s À and TFTFE are largely accelerated, and the formation of stable SEI is inhibited.…”

The importance of electrode interfaces and interphases for rechargeable metal batteries

“…For example, it is reported that SEI formed on Na metal is partially soluble in alkyl carbonate electrolytes while, in ether-based electrolytes, the SEI on Na metal shows unexpectedly low initial resistances and transport instabilities after long-term ageing. Also, SEIs formed on K metal electrodes are reported as mechanically unstable, while SEIs on Mg metal electrodes formed during contact with glyme-based electrolytes are possibly composite in nature (comprising liquid and solid phases) 12 – 14 .…”