Herein the first inorganic magnesium salt solution capable of highly reversible magnesium electrodeposition is presented. Synthesized by acid-base reaction of MgCl2 and Lewis acidic compounds such as AlCl3, this salt class demonstrates upwards of 99% Coulombic efficiency, deposition overpotential of <200 mV, and anodic stability of 3.1 V.

Phosphate materials are being extensively studied as lithium-ion battery electrodes. In this work, we present a highthroughput ab initio analysis of phosphates as cathode materials. Capacity, voltage, specific energy, energy density, and thermal stability are evaluated computationally on thousands of compounds. The limits in terms of gravimetric and volumetric capacity inherent to the phosphate chemistry are determined. Voltage ranges for all redox couples in phosphates are provided, and the structural factors influencing the voltages are analyzed. We reinvestigate whether phosphate materials are inherently safe and find that, for the same oxidation state, oxygen release happens thermodynamically at lower temperature for phosphates than for oxides. These findings are used to recommend specific chemistries within the phosphate class and to show the intrinsic limits of certain materials of current interest (e.g., LiCoPO 4 and LiNiPO 4 ).

We have used density functional theory (DFT) to investigate the ternary phase diagram of the Li−Fe−F system and the reactions of Li with iron fluorides. Several novel compounds, not previously identified in the Li−Fe−F system, are predicted to be stable. Electrochemical voltage profiles, derived from the evolution of the Li chemical potential in the calculated phase diagram, are in reasonable agreement with experimental trends. The effect of particle size on the Fe that precipitates when Li x FeF3 reacts with Li is also investigated. We find that when 1 nm Fe particles form, the potential for this reaction is considerably reduced from its bulk value and relate this to the experimental observations. Furthermore, we formulate a model for the significant hysteresis that is observed in the lithiation and delithiation of FeF3. Nonequilibrium paths derived by assuming much faster diffusion of Li than Fe are in reasonable agreement with experimental profiles. Our kinetic model predicts that the iron fluoride reaction follows a different path through the phase diagram during conversion (discharge) and reconversion (charge), which results in the voltage profile hysteresis observed during experiment. The proposed kinetic model also explains why upon extraction of Li from a 3/1 mixture of LiF and Fe a rutile FeF2-like structure can form, even when iron should be oxidized to Fe3+ by extraction of three Li+ per Fe.

Identified Computationally. -A new class of materials which can intercalate lithium reversibly is discovered by a novel high-throughput ab initio computational approach. Na3FeCO3PO4 and Na3MnCO3PO4 are hydrothermally synthesized from aqueous solutions of FeSO4 or MnNO3, (NH4)2HPO4, and Na2CO3 (autoclave, 120°C, 70 h). Li-Na ion exchange produces Li 3 FeCO 3 PO 4 and Li 3 MnCO 3 PO 4 . The Mn carbonophosphate Li3MnCO3PO4 could potentially display a specific energy 45% greater than that of LiFePO4 and might be a promising cathode material for Li ion batteries. -(CEDER*, G.; et al.; Chem. Mater.