No abstract

Calcium is a highly attractive metal anode because of its high earth abundance and low reduction potential. However, the lack of calcium electrolytes for reversible calcium deposition significantly hampers the development of Ca rechargeable batteries. Herein, the calcium deposition/stripping behaviors of a calcium salt electrolyte, Ca[B(hfip)4]2 ([B(hfip)4]−=tetrakis(hexafluoroisopropyloxy)borate) were systematically studied using different working electrodes (GC, Pt, Cu, and Al) and different solvents including tetrahydrofuran (THF), dimethoxyethane (DME), and diglyme (DGM). It was found that the Ca[B(hfip)4]2/DGM electrolyte demonstrated the highest reversibility and stability in cyclic voltammetry and symmetric Ca/Ca half‐cell studies. The Ca[B(hfip)4]2/DGM electrolyte was further employed to demonstrate a 3.4 V Ca battery using a FePO4 cathode with a discharge capacity of 120 Ah/mg.

Calcium batteries are a potentially sustainable, high‐energy‐density battery technology beyond Li ion batteries. Now the development of Ca batteries has become possible with a newly invented Ca electrolyte capable of reversible Ca deposition/stripping at room temperature.

DFT calculations were conducted to provide unprecedented thermodynamic insights on tetrahydrofuran (THF) solvation, isomerization, and complexation of possible MgÀ Cl coordination species for popular MgÀ Cl electrolytes for magnesium batteries. Computational results using the M06-2x functional with the 6-31 + G(d) basis set indicate that trigonal bipyramidal e,e-cis-tbp-MgCl 2 (THF) 3 dichloride species and octahedral [MgCl (THF) 5 ] + monochloride species are the dominant mononuclear species. These two can combine to form the dinuclear species [(μ-Cl) 3 Mg 2 (THF) 6 ] + with a free energy À 6.30 kcal/mol, which is calculated to be the dominant MgÀ Cl species in solution. Two mono-cation species, [(μ-Cl) 3 Mg 2 (THF) 6 ] + and [MgCl(THF) 5 ] + , have comparable LUMO energies, thus both of them can act as active species for Mg deposition. However, the significant dominance of the dinuclear species in the electrolyte indicates that it is the primary species involved in reversible Mg deposition.[a] J.

Metal organic frameworks (MOFs) of the type NBu4M­(DHBQ)1.5 (M = Ni2+, Fe2+, and Co2+; DHBQ = 2,5-dihydroxy-1,4-benzoquinone) were prepared with improved yield up to 100% via a simple benchtop aqueous addition reaction. For the first time, the crystalline phase of this formula polymer was synthesized without in situ generation of the DHBQ ligand from 2, 5-diamino-1,4-benzoquinone (DABQ). Powder X-ray diffraction and elemental analysis confirm the crystalline phase and composition of products. Infrared and electron dispersive spectroscopy further confirm that the materials are homologous to the reported single crystalline polymers. The present MOF synthesis can be extended to halide-substituted ligands, i.e., 3,6-dichloro-2,5-dihydroxy-1,4-benzoquinone (chloranilic acid, CAN) and 3,6-difluoro-2,5-dihydroxy-1,4-benzoquinone (fluoranilic acid, FAN).