Oscar Tutusaus

An Efficient Halogen‐Free Electrolyte for Use in Rechargeable Magnesium Batteries

Unlocking the full potential of rechargeable magnesium batteries has been partially hindered by the reliance on chloride-based complex systems. Despite the high anodic stability of these electrolytes, they are corrosive toward metallic battery components, which reduce their practical electrochemical window. Following on our new design concept involving boron cluster anions, monocarborane CB11H12(-) produced the first halogen-free, simple-type Mg salt that is compatible with Mg metal and displays an oxidative stability surpassing that of ether solvents. Owing to its inertness and non-corrosive nature, the Mg(CB11H12)2/tetraglyme (MMC/G4) electrolyte system permits standardized methods of high-voltage cathode testing that uses a typical coin cell. This achievement is a turning point in the research and development of Mg electrolytes that has deep implications on realizing practical rechargeable Mg batteries.

Novel and versatile room temperature ionic liquids for energy storage

Due to their high glass transition temperatures, ionic liquids based on closo-boron clusters have been long discounted from consideration in energy storage applications. Here, we report a strategy that resulted in a novel family of closo-boron-cluster based room temperature ionic liquids (RTILs). Their very low glass transition temperatures, high cathodic and anodic stabilities and compatibility with Li and Mg metals make them excellent candidates as electrolytes for rechargeable batteries and hybrid devices.

Small-molecule crystallography in the battery electrolyte development

Rechargeable Mg batteries have been proposed as candidates for post lithium-ion batteries due to their higher volumetric capacity, lower cost, and absence of dendrite formation. One of the current challenges in their development is the identification of electrolyte that is noncorrosive and chemically stable to Mg metal. Here, we will share a structural characterization of a new electrolyte, magnesium monocarborane (MMC), that stands out as the first simple-salt magnesium compound, providing high anodic stability, non-corrosive, and chemically robust. Dissolving MMC in various glymes (monoglyme (G1 or DME), diglyme (G2), and tetraglyme (G4)) resulted in crystallization of MMC-glyme solvates [Mg(G1)3](CB11H12)2 (1), [Mg(G2)2](CB11H12)2·(G2) (2), and [Mg(G4)2(H2O)](CB11H12)2 (3), respectively. Their X-ray diffraction analysis revealed Mg solvent-separated ion pairs, indicative of a high level of salt dissociation despite the low solvent polarity. Moreover, in the case of G4 two or more adjacent oxygen atoms at one end of the tetraglyme are not involved in Mg coordination, perhaps assisting effective salt dissolution through cation–anion asymmetry. In the solid state structure of 1 two carborane half-cages displayed symmetry induced disorder for Cand B-atoms, which was modeled by allowing shared 0.5:05 occupancy for B and C occupying the same position. The crystal structure of 2 is an inversion twin and the ratio of the two twin components refined to 0.65:0.35. In 3, one of the side chains of G4 displayed a positional disorder, which was refined with the 0.6:0.4 ratio between two orientations. The final R1 values were 0.0794 (wR2 = 0.2222) for 4904 reflections [I > 2(I)]; 0.0350 (wR2 = 0.0883) for 7162 reflections [I > 2(I)]; and 0.0649 (wR2 = 0.1670) for 1564 reflections [I > 2(I)] for 1, 2, and 3, respectively.