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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on MgV2O4 by Materials Project

MgV2O4 is Spinel structured and crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve VO6 octahedra. The corner-sharing octahedra tilt angles range from 58–59°. There are three shorter (2.00 Å) and one longer (2.01 Å) Mg–O bond lengths. There are four inequivalent V3+ sites. In the first V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with six equivalent MgO4 tetrahedra and edges with six VO6 octahedra. There are four shorter (2.06 Å) and two longer (2.07 Å) V–O bond lengths. In the second V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with six equivalent MgO4 tetrahedra and edges with six VO6 octahedra. There are a spread of V–O bond distances ranging from 2.05–2.07 Å. In the third V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with six equivalent MgO4 tetrahedra and edges with six VO6 octahedra. There are four shorter (2.06 Å) and two longer (2.07 Å) V–O bond lengths. In the fourth V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with six equivalent MgO4 tetrahedra and edges with six VO6 octahedra. There are four shorter (2.06 Å) and two longer (2.07 Å) V–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+ and three V3+ atoms to form a mixture of distorted edge and corner-sharing OMgV3 trigonal pyramids. In the second O2- site, O2- is bonded to one Mg2+ and three V3+ atoms to form a mixture of distorted edge and corner-sharing OMgV3 trigonal pyramids. In the third O2- site, O2- is bonded to one Mg2+ and three V3+ atoms to form a mixture of distorted edge and corner-sharing OMgV3 trigonal pyramids. In the fourth O2- site, O2- is bonded to one Mg2+ and three V3+ atoms to form a mixture of distorted edge and corner-sharing OMgV3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgV2O4 by Materials Project

MgV2O4 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine VO6 octahedra. The corner-sharing octahedra tilt angles range from 56–59°. All Mg–O bond lengths are 2.00 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three VO4 tetrahedra, and edges with six VO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.07–2.11 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine VO6 octahedra. The corner-sharing octahedra tilt angles range from 57–60°. There are a spread of Mg–O bond distances ranging from 1.99–2.02 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four VO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five VO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.09–2.11 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six VO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent VO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.13 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six VO4 tetrahedra, edges with two MgO6 octahedra, and edges with four VO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.13 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five VO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five VO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.07–2.13 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six VO4 tetrahedra, edges with two MgO6 octahedra, and edges with four VO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.12 Å. There are twelve inequivalent V3+ sites. In the first V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with three MgO4 tetrahedra, corners with three VO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four VO6 octahedra. There are a spread of V–O bond distances ranging from 2.01–2.10 Å. In the second V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent VO4 tetrahedra, edges with two MgO6 octahedra, and edges with four VO6 octahedra. There are a spread of V–O bond distances ranging from 2.00–2.11 Å. In the third V3+ site, V3+ is bonded to four O2- atoms to form VO4 tetrahedra that share corners with six MgO6 octahedra and corners with six VO6 octahedra. The corner-sharing octahedra tilt angles range from 56–58°. There is three shorter (1.95 Å) and one longer (1.97 Å) V–O bond length. In the fourth V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four VO4 tetrahedra, edges with three MgO6 octahedra, and edges with three VO6 octahedra. There are a spread of V–O bond distances ranging from 2.02–2.09 Å. In the fifth V3+ site, V3+ is bonded to four O2- atoms to form VO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine VO6 octahedra. The corner-sharing octahedra tilt angles range from 56–59°. There is one shorter (1.93 Å) and three longer (1.97 Å) V–O bond length. In the sixth V3+ site, V3+ is bonded to four O2- atoms to form VO4 tetrahedra that share corners with six MgO6 octahedra and corners with six VO6 octahedra. The corner-sharing octahedra tilt angles range from 55–59°. There are a spread of V–O bond distances ranging from 1.94–1.98 Å. In the seventh V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with six VO4 tetrahedra, edges with two equivalent VO6 octahedra, and edges with four MgO6 octahedra. There are a spread of V–O bond distances ranging from 2.04–2.08 Å. In the eighth V3+ site, V3+ is bonded to four O2- atoms to form VO4 tetrahedra that share corners with six MgO6 octahedra and corners with six VO6 octahedra. The corner-sharing octahedra tilt angles range from 57–59°. There are a spread of V–O bond distances ranging from 1.93–2.00 Å. In the ninth V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five VO4 tetrahedra, edges with three MgO6 octahedra, and edges with three VO6 octahedra. There are a spread of V–O bond distances ranging from 2.02–2.10 Å. In the tenth V3+ site, V3+ is bonded to four O2- atoms to form VO4 tetrahedra that share corners with six MgO6 octahedra and corners with six VO6 octahedra. The corner-sharing octahedra tilt angles range from 56–58°. There are a spread of V–O bond distances ranging from 1.94–1.99 Å. In the eleventh V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent VO4 tetrahedra, edges with two MgO6 octahedra, and edges with four VO6 octahedra. There are a spread of V–O bond distances ranging from 2.01–2.11 Å. In the twelfth V3+ site, V3+ is bonded to four O2- atoms to form VO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine VO6 octahedra. The corner-sharing octahedra tilt angles range from 57–59°. There is one shorter (1.94 Å) and three longer (1.97 Å) V–O bond length. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two V3+ atoms. In the second O2- site, O2- is bonded to two Mg2+ and two equivalent V3+ atoms to form distorted corner-sharing OMg2V2 trigonal pyramids. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the fourth O2- site, O2- is bonded to four V3+ atoms to form distorted OV4 trigonal pyramids that share corners with four OMg2V2 trigonal pyramids and edges with three OMgV3 trigonal pyramids. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two V3+ atoms. In the sixth O2- site, O2- is bonded to one Mg2+ and three V3+ atoms to form distorted OMgV3 trigonal pyramids that share corners with four OMg2V2 trigonal pyramids and edges with three OMgV3 trigonal pyramids. In the seventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the eighth O2- site, O2- is bonded to one Mg2+ and three V3+ atoms to form distorted OMgV3 trigonal pyramids that share corners with three equivalent OMg2V2 trigonal pyramids and edges with three OV4 trigonal pyramids. In the ninth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the tenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two V3+ atoms. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the twelfth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two V3+ atoms. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the fifteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the seventeenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two V3+ atoms. In the eighteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two V3+ atoms. In the nineteenth O2- site, O2- is bonded to two Mg2+ and two equivalent V3+ atoms to form distorted corner-sharing OMg2V2 trigonal pyramids. In the twentieth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the twenty-first O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the twenty-second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four V3+ atoms. In the twenty-third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the twenty-fourth O2- site, O2- is bonded to one Mg2+ and three V3+ atoms to form distorted corner-sharing OMgV3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgV2O4 by Materials Project

MgV2O4 is Spinel-like structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are six inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine VO6 octahedra. The corner-sharing octahedra tilt angles range from 56–60°. There are a spread of Mg–O bond distances ranging from 1.99–2.02 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six VO4 tetrahedra, edges with two MgO6 octahedra, and edges with four VO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.07–2.13 Å. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four VO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five VO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.12 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six VO4 tetrahedra, edges with two MgO6 octahedra, and edges with four VO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.15 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six VO4 tetrahedra, edges with two MgO6 octahedra, and edges with four VO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.11 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five VO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five VO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.07–2.13 Å. There are twelve inequivalent V3+ sites. In the first V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four VO4 tetrahedra, edges with three MgO6 octahedra, and edges with three VO6 octahedra. There are a spread of V–O bond distances ranging from 2.02–2.09 Å. In the second V3+ site, V3+ is bonded to four O2- atoms to form VO4 tetrahedra that share corners with six MgO6 octahedra and corners with six VO6 octahedra. The corner-sharing octahedra tilt angles range from 56–59°. There are a spread of V–O bond distances ranging from 1.93–1.98 Å. In the third V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent VO4 tetrahedra, edges with two MgO6 octahedra, and edges with four VO6 octahedra. There are a spread of V–O bond distances ranging from 1.99–2.13 Å. In the fourth V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four VO4 tetrahedra, edges with three MgO6 octahedra, and edges with three VO6 octahedra. There are a spread of V–O bond distances ranging from 2.04–2.07 Å. In the fifth V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with six VO4 tetrahedra, edges with two equivalent VO6 octahedra, and edges with four MgO6 octahedra. There are a spread of V–O bond distances ranging from 2.05–2.07 Å. In the sixth V3+ site, V3+ is bonded to four O2- atoms to form VO4 tetrahedra that share corners with six MgO6 octahedra and corners with six VO6 octahedra. The corner-sharing octahedra tilt angles range from 55–59°. There are a spread of V–O bond distances ranging from 1.94–1.98 Å. In the seventh V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with six VO4 tetrahedra, edges with two equivalent VO6 octahedra, and edges with four MgO6 octahedra. There are a spread of V–O bond distances ranging from 2.02–2.09 Å. In the eighth V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five VO4 tetrahedra, edges with three MgO6 octahedra, and edges with three VO6 octahedra. There are a spread of V–O bond distances ranging from 2.03–2.08 Å. In the ninth V3+ site, V3+ is bonded to four O2- atoms to form VO4 tetrahedra that share corners with six MgO6 octahedra and corners with six VO6 octahedra. The corner-sharing octahedra tilt angles range from 56–58°. There are a spread of V–O bond distances ranging from 1.92–1.98 Å. In the tenth V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five VO4 tetrahedra, edges with three MgO6 octahedra, and edges with three VO6 octahedra. There are a spread of V–O bond distances ranging from 2.03–2.09 Å. In the eleventh V3+ site, V3+ is bonded to four O2- atoms to form VO4 tetrahedra that share corners with six MgO6 octahedra and corners with six VO6 octahedra. The corner-sharing octahedra tilt angles range from 55–58°. There are a spread of V–O bond distances ranging from 1.93–1.98 Å. In the twelfth V3+ site, V3+ is bonded to four O2- atoms to form VO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine VO6 octahedra. The corner-sharing octahedra tilt angles range from 57–59°. There are a spread of V–O bond distances ranging from 1.94–1.98 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two V3+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two V3+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the fifth O2- site, O2- is bonded to two Mg2+ and two V3+ atoms to form distorted corner-sharing OMg2V2 trigonal pyramids. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the seventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the eighth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two V3+ atoms. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two V3+ atoms. In the tenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the twelfth O2- site, O2- is bonded to two Mg2+ and two V3+ atoms to form distorted corner-sharing OMg2V2 trigonal pyramids. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two V3+ atoms. In the fourteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two V3+ atoms. In the sixteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two V3+ atoms. In the seventeenth O2- site, O2- is bonded to two Mg2+ and two V3+ atoms to form distorted corner-sharing OMg2V2 trigonal pyramids. In the eighteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the nineteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms. In the twentieth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two V3+ atoms. In the twenty-first O2- site, O2- is bonded to four V3+ atoms to form distorted OV4 trigonal pyramids that share corners with three OMg2V2 trigonal pyramids and edges with two OMgV3 trigonal pyramids. In the twenty-second O2- site, O2- is bonded to one Mg2+ and three V3+ atoms to form distorted OMgV3 trigonal pyramids that share corners with three OMg2V2 trigonal pyramids and edges with two OMgV3 trigonal pyramids. In the twenty-third O2- site, O2- is bonded to one Mg2+ and three V3+ atoms to form distorted OMgV3 trigonal pyramids that share corners with three equivalent OMg2V2 trigonal pyramids and edges with two OV4 trigonal pyramids. In the twenty-fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three V3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgV2O4 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgV2O4 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
NASA NTRS2007

Investigation of Synthetic Mg(1.3)V(1.7)O4 Spinel with MgO Inclusions: Case Study of a Spinel with an Apparently occupied Interstitial Site

A magnesium vanadate spinel crystal, ideally MgV2O4, synthesized at 1 bar, 1200 C and equilibrated under FMQ + 1.3 log f(sub o2) condition, was investigated using single-crystal X-ray diffraction, electron microprobe, and electron backscatter (EBSD). The initial X-ray structure refinements gave tetrahedral and octahedral site occupancies, along with the presence of 0.053 apfu Mg at an interstitial octahedral site . Back-scattered electron (BSE) images and electron microprobe analyses revealed the existence of an Mg-rich phase in the spinel matrix, which was too small (less than or equal to 3microns) for an accurate chemical determination. The EBSD analysis combined with X-ray energy dispersive spectroscop[y (XEDS) suggested that the Mg-rich inclusions are periclase oriented coherently with the spinel matrix. The final structure refinements were optimized by subtracting the X-ray intensity contributions (approx. 9%) of periclase reflections, which eliminated the interstitial Mg. This study provides insight into possible origins of refined interstitial cations reported in the the literature for spinel, and points to the difficulty of using only X-ray diffraction data to distinguish a spinel with interstitial cations from one with coherently oriented MgO inclusions.

Uchida, Hinako↗
DOE OSTI2025

Thermal decomposition pathways of bulk electrolytes on vanadium oxide nanocrystals

The thermal stability of electrolytes at an elevated temperature induced by battery charge-discharge cycling is critical for the long cycling performance of a rechargeable battery. For many multivalent systems, such as rechargeable magnesium batteries, which offer great potential for high energy density and utilize earth-abundant resources, electrolyte instability and electrode surface passivation, arising from electrolyte decomposition, remain as major roadblocks. Understanding the electrolyte decomposition pathways at the electrode-electrolyte interface is essential to provide guidance in overcoming this challenge. In this work, in situ 13 C magic angle spinning nuclear magnetic resonance (MAS NMR) and first-principles calculations were used to investigate the thermal decomposition of the electrolyte in a system consisting of MgV 2 O 4 , a novel cathode for magnesium batteries, mixed with a bulk electrolyte consisting of magnesium bis(trifluoromethanesulfonyl)imide (Mg(TFSI) 2 ) in diglyme (G2). We show that significant electrolyte decomposition is observed in bulk 1.0 M Mg(TFSI) 2 in G2 mixed with nanometer sized MgV 2 O 4 powder at elevated temperatures. This observation is to mimic the possible thermal decomposition that might happen during battery cycling. We demonstrate that the MgV 2 O 4 surface is covered by a layer of decomposed G2 products. We conclude that the dominant reaction pathway for electrolyte decomposition is the thermal decomposition of the pure electrolytes at elevated temperatures, followed by adsorption of G2 decomposition products to the MgV 2 O 4 surface. The activation energy for the major decomposition pathway is obtained. In conclusion, this work highlights the importance of studying thermal decomposition of electrolytes for overall system stability and explores electrolyte stability at significantly elevated temperatures.

25 ENERGY STORAGE↗
DOE OSTI2023

Electrolyte Reactivity on the MgV 2 O 4 Cathode Surface

Predictive understanding of the solvation-dependent reactivity and molecular interaction of electrolyte ions and solvent molecules on reactive electrodes has been a major challenge but is essential for addressing instabilities and surface passivation that occur at electrode-electrolyte interface (EEI) of multivalent Mg batteries. In this work, the isolated intrinsic reactivities of prominent chemical species present in magnesium bis(trifluoromethanesulfonimide) (Mg(TFSI) 2 ) in diglyme (G2) electrolytes, including ionic (TFSI - , [Mg(TFSI)] + , [Mg(TFSI):G2] + , [Mg(TFSI):2G2] + ) as well as neutral molecules (G2) on magnesium vanadate cathode (MgV 2 O 4 ) surface has been studied using a combination of first-principles calculations and multimodal analysis of well-defined cathode electrolyte interphase (CEI) layers. Here, our calculations show that non-solvated [Mg(TFSI)] + is the strongest adsorbing species on the MgV 2 O 4 surface compared to all other ions while fully solvated [Mg(TFSI):2G2] + are least favorable to decomposition. The cleavage of C-S bonds in TFSI - to form CF 3 - is predicted to be most desired pathway for all ionic species, which is followed by the cleavage of C-O bonds of G2 to yield CH 3 + or OCH 3 - species. The strong stabilization and electron transfer between ionic electrolyte species and MgV 2 O 4 is found to significantly favor these decomposition reactions on the surface compared to intrinsic gas phase dissociation. Experimentally, we used state-of-the-art ion soft landing to selectively deposit mass-selected TFSI - , [Mg(TFSI):G2] + and [Mg(TFSI):2G2] + on MgV 2 O 4 thin film to form well-defined electrolyte-MgV 2 O 4 interface. Analysis of soft-landed interphase using X-ray photoelectron, X-ray absorption near edge structure, electron energy-loss spectroscopies as well as transmission electron microscopy confirmed the presence of decomposition species (e.g., MgFx, carbonates) formed in the interfacial region and the higher amount of MgFx with [Mg(TFSI):G2] + , which corroborates the theoretical observation. Overall, we established the mechanistic pathway for the electrolyte-induced formation of passivating fluorides on MgV 2 O 4 cathode facilitated by the surface adsorption and charge transfer, which provided essential knowledge for rational design of stable electrolytes for multivalent cathodes.

Cathode-electrolyte interphase formation↗