Formation, chemical evolution and solidification of the dense liquid phase of calcium (bi)carbonate.

Metal carbonates, which are ubiquitous in the near-surface mineral record, are a major product of biomineralizing organisms and serve as important targets for capturing anthropogenic CO emissions. However, pathways of carbonate mineralization typically diverge from classical predictions due to the involvement of disordered precursors, such as the dense liquid phase (DLP), yet little is known about DLP formation or solidification processes. Using in situ methods we report that a highly hydrated bicarbonate DLP forms via liquid-liquid phase separation and transforms into hollow hydrated amorphous CaCO particles.

Accelerating Computational Materials Discovery with Machine Learning and Cloud High-Performance Computing: from Large-Scale Screening to Experimental Validation.

High-throughput computational materials discovery has promised significant acceleration of the design and discovery of new materials for many years. Despite a surge in interest and activity, the constraints imposed by large-scale computational resources present a significant bottleneck. Furthermore, examples of very large-scale computational discovery carried out through experimental validation remain scarce, especially for materials with product applicability.

From Bulk to Interface: Solvent Exchange Dynamics and Their Role in Ion Transport and the Interfacial Model of Rechargeable Magnesium Batteries.

Multivalent battery chemistries have been explored in response to the increasing demand for high-energy rechargeable batteries utilizing sustainable resources. Solvation structures of working cations have been recognized as a key component in the design of electrolytes; however, most structure-property correlations of metal ions in organic electrolytes usually build upon favorable static solvation structures, often overlooking solvent exchange dynamics. We here report the ion solvation structures and solvent exchange rates of magnesium electrolytes in various solvents by using multimodal nuclear magnetic resonance (NMR) analysis and molecular dynamics/density functional theory (MD/DFT) calculations.

Understanding the Surprising Ionic Conductivity Maximum in Zn(TFSI) Water/Acetonitrile Mixture Electrolytes.

Aqueous electrolytes composed of 0.1 M zinc bis(trifluoromethylsulfonyl)imide (Zn(TFSI)) and acetonitrile (ACN) were studied using combined experimental and simulation techniques. The electrolyte was found to be electrochemically stable when the ACN V% is higher than 74.

Electrolyte Reactivity on the MgVO Cathode Surface.

Predictive understanding of the molecular interaction of electrolyte ions and solvent molecules and their chemical reactivity on electrodes has been a major challenge but is essential for addressing instabilities and surface passivation that occur at the electrode-electrolyte interface of multivalent magnesium batteries. In this work, the isolated intrinsic reactivities of prominent chemical species present in magnesium bis(trifluoromethanesulfonimide) (Mg(TFSI)) in diglyme (G2) electrolytes, including ionic (TFSI, [Mg(TFSI)], [Mg(TFSI):G2], and [Mg(TFSI):2G2]) as well as neutral molecules (G2) on a well-defined magnesium vanadate cathode (MgVO) surface, have been studied using a combination of first-principles calculations and multimodal spectroscopy analysis. Our calculations show that nonsolvated [Mg(TFSI)] is the strongest adsorbing species on the MgVO surface compared with all other ions while partially solvated [Mg(TFSI):G2] is the most reactive species.

Multi-Step Nucleation of a Crystalline Silicate Framework via a Structurally Precise Prenucleation Cluster.

Hierarchical nucleation pathways are ubiquitous in the synthesis of minerals and materials. In the case of zeolites and metal-organic frameworks, pre-organized multi-ion "secondary building units" (SBUs) have been proposed as fundamental building blocks. However, detailing the progress of multi-step reaction mechanisms from monomeric species to stable crystals and defining the structures of the SBUs remains an unmet challenge.

Understanding the Solvation-Dependent Properties of Cyclic Ether Multivalent Electrolytes Using High-Field NMR and Quantum Chemistry.

Efforts to expand the technological capability of batteries have generated increased interest in divalent cationic systems. Electrolytes used for these electrochemical applications often incorporate cyclic ethers as electrolyte solvents; however, the detailed solvation environments within such systems are not well-understood. To foster insights into the solvation structures of such electrolytes, Ca(TFSI) and Zn(TFSI) dissolved in tetrahydrofuran (THF) and 2-methyl-tetrahydrofuran were investigated through multi-nuclear magnetic resonance spectroscopy (O, Ca, and Zn NMR) combined with quantum chemistry modeling of NMR chemical shifts.

An automated framework for high-throughput predictions of NMR chemical shifts within liquid solutions.

Identifying stable speciation in multi-component liquid solutions is fundamentally important to areas from electrochemistry to organic chemistry and biomolecular systems. Here we introduce a fully automated, high-throughput computational framework for the accurate prediction of stable species in liquid solutions by computing the nuclear magnetic resonance (NMR) chemical shifts. The framework automatically extracts and categorizes hundreds of thousands of atomic clusters from classical molecular dynamics simulations, identifies the most stable species in solution and calculates their NMR chemical shifts via density functional theory calculations.

Concentration-dependent ion correlations impact the electrochemical behavior of calcium battery electrolytes.

Ion interactions strongly determine the solvation environments of multivalent electrolytes even at concentrations below that required for practical battery-based energy storage. This statement is particularly true of electrolytes utilizing ethereal solvents due to their low dielectric constants. These solvents are among the most commonly used for multivalent batteries based on reactive metals (Mg, Ca) due to their reductive stability.

Role of a Multivalent Ion-Solvent Interaction on Restricted Mg Diffusion in Dimethoxyethane Electrolytes.

The diffusion behavior of Mg in electrolytes is not as readily accessible as that from Li or Na utilizing PFG NMR, due to the low sensitivity, poor resolution, and rapid relaxation encountered when attempting Mg NMR. In MgTFSI/DME solutions, "bound" DME (coordinating to Mg) and "free" DME (bulk) are distinguishable from H NMR. With the exchange rates between them obtained from 2D H EXSY NMR, we can extract the self-diffusivities of free DME and bound DME (which are equal to that of Mg) before the exchange occurs using PFG diffusion NMR measurements coupled with analytical formulas describing diffusion under two-site exchange.

Role of Polysulfide Anions in Solid-Electrolyte Interphase Formation at the Lithium Metal Surface in Li-S Batteries.

Delineating intricate interactions between highly reactive Li-metal electrodes and the diverse constituents of battery electrolytes has been a long-standing scientific challenge in materials design for advanced energy storage devices. Here, we isolated lithium polysulfide anions (LiS) from an electrolyte solution based on their mass-to-charge ratio and deposited them on Li-metal electrodes under clean vacuum conditions using ion soft landing (ISL), a highly controlled interface preparation technique. The molecular level precision in the construction of these model interfaces with ISL, coupled with X-ray photoelectron spectroscopy and theoretical calculations, allowed us to obtain unprecedented insight into the parasitic reactions of well-defined polysulfides on Li-metal electrodes.

Insights into Spontaneous Solid Electrolyte Interphase Formation at Magnesium Metal Anode Surface from Molecular Dynamics Simulations.

Spontaneous chemical reactivity at multivalent (Mg, Ca, Zn, Al) electrode surfaces is critical to solid electrolyte interphase (SEI) formation, and hence, directly affects the longevity of batteries. Here, we report an investigation of the reactivity of 0.5 M Mg(TFSI) in 1,2-dimethoxyethane (DME) solvent at a Mg(0001) surface using molecular dynamics (AIMD) simulations and detailed Bader charge analysis.

Quantifying Species Populations in Multivalent Borohydride Electrolytes.

Multivalent batteries represent an important beyond Li-ion energy storage concept. The prospect of calcium batteries, in particular, has emerged recently due to novel electrolyte demonstrations, especially that of a ground-breaking combination of the borohydride salt Ca(BH) dissolved in tetrahydrofuran. Recent analysis of magnesium and calcium versions of this electrolyte led to the identification of divergent speciation pathways for Mg and Ca despite identical anions and solvents, owing to differences in cation size and attendant flexibility of coordination.

Role of Solvent Rearrangement on Mg Solvation Structures in Dimethoxyethane Solutions using Multimodal NMR Analysis.

One of the main impediments faced for predicting emergent properties of a multivalent electrolyte (such as conductivity and electrochemical stability) is the lack of quantitative analysis of ion-ion and ion-solvent interactions, which manifest in solvation structures and dynamics. In particular, the role of ion-solvent interactions is still unclear in cases where the strong electric field from multivalent cations can influence intramolecular rotations and conformal structural evolution (i.e.

Energy storage emerging: A perspective from the Joint Center for Energy Storage Research.

Energy storage is an integral part of modern society. A contemporary example is the lithium (Li)-ion battery, which enabled the launch of the personal electronics revolution in 1991 and the first commercial electric vehicles in 2010. Most recently, Li-ion batteries have expanded into the electricity grid to firm variable renewable generation, increasing the efficiency and effectiveness of transmission and distribution.

Origin of Unusual Acidity and Li Diffusivity in a Series of Water-in-Salt Electrolytes.

Superconcentrated aqueous electrolytes ("water-in-salt" electrolytes, or WiSEs) enable various aqueous battery chemistries beyond the voltage limits imposed by the Pourbaix diagram of water. However, their detailed structural and transport properties remain unexplored and could be better understood through added studies. Here, we report on our observations of strong acidity (pH 2.

Variable Temperature and Pressure Operando MAS NMR for Catalysis Science and Related Materials.

The characterization of catalytic materials under working conditions is of paramount importance for a realistic depiction and comprehensive understanding of the system. Under such relevant environments, catalysts often exhibit properties or reactivity not observed under standard spectroscopic conditions. Fulfilling such harsh environments as high temperature and pressure is a particular challenge for solid-state NMR where samples spin several thousand times a second within a strong magnetic field.

Adsorption and Thermal Decomposition of Electrolytes on Nanometer Magnesium Oxide: An in Situ C MAS NMR Study.

Mg batteries have been proposed as potential alternatives to lithium-ion batteries because of their lower cost, higher safety, and enhanced charge density. However, the Mg metal readily oxidizes when exposed to an oxidizer to form a thin MgO passivation surface layer that blocks the transport of Mg across the solid electrode-electrolyte interface (SEI). In this work, the adsorption and thermal decomposition of diglyme (G2) and electrolytes containing Mg(TFSI) in G2 on 10 nm-sized MgO particles are evaluated by a combination of in situ C single-pulse, surface-sensitive H-C cross-polarization (CP) magic-angle spinning (MAS) nuclear magnetic resonance, and quantum chemistry calculations.

Role of Inorganic Surface Layer on Solid Electrolyte Interphase Evolution at Li-Metal Anodes.

Lithium metal is an ideal anode for rechargeable lithium-battery technology. However, the extreme reactivity of Li metal with electrolytes leads to solid electrolyte interphase (SEI) layers that often impede Li transport across interfaces. The challenge is to predict the chemical, structural, and topographical heterogeneities of SEI layers arising from a multitude of interfacial constituents.

A novel high-temperature MAS probe with optimized temperature gradient across sample rotor for in-situ monitoring of high-temperature high-pressure chemical reactions.

We present a novel nuclear magnetic resonance (NMR) probe design focused on optimizing the temperature gradient across the sample for high temperature magic angle spinning (MAS) experiments using standard rotors. Computational flow dynamics (CFD) simulations were used to assess and optimize the temperature gradient across the sample under MAS conditions. The chemical shift and linewidth of Pb direct polarization in lead nitrate were used to calibrate the sample temperature and temperature gradient, respectively.