Magnesium-ion batteries are plagued by interface issues consisting of electrolyte incompatibility, sluggish Mg-ion reaction kinetics at the cathode, and passivation layer formation on the Mg metal anode. One possible method for remedying all of these issues simultaneously is through the development of novel solid-state battery technology. One major issue with cathodes for Mg-ion storage is the loss of active material due to electrolyte dissolution. Additionally, one of the main sources of battery thermal runaway and explosion is the danger associated with the flammable organic liquid electrolytes used in these systems. The primary advantages of using a solid electrolyte include, but are not limited to, the suppression of active material dissolution and the increased safety due to the removal of flammable liquid electrolytes. In this work we demonstrate the versatility of polyoxometalates (POMs) by employing them as both the active material within the cathode and the Mg-ion conducting solid electrolyte material in a full-cell solid-state Mg-ion battery. Considered one of the most diverse classes of inorganic molecules, POMs are polyatomic clusters of early transition metals (Mo, W or Nb) joined by oxygen atoms to form a 3D framework. Known for their unique redox activity, they also possess high ionic conductivity and multiple stable reduced and oxidized states. Combined with their innate ability to delocalize electron density throughout the entire molecule without destroying the structural integrity of the molecule; POMs are ideal electrode materials for energy storage devices. By pairing the POM active material with conductive substrates, they can function as cathodes for efficient Mg-ion storage. However, without any conductive additives, the POM molecules can potentially serve as a Mg-ion conducting solid electrolyte. The functionality of this Mg solid-state battery is derived from the reactions that occur at the interface between the POM solid electrolyte and the Mg-metal anode. Using x-ray photoelectron spectroscopy (XPS), we can characterize the chemical species that form at the anode interface as a result of POM electrolyte reduction on the Mg-metal anode surface. The composition of this solid electrolyte interphase (SEI) layer on the Mg anode surface can provide insight as to why the layer is Mg-ion conductive.

Characterizing solid electrolyte interphase-layer formation using x-ray photoelectron spectroscopy in solid-state Mg-ion batteries

256th National Meeting (2018)

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