Cellulosic biomass derived molecules such as glucose can be converted into specific platform chemicals like 5-hydroxymethylfurfural (HMF), levulinic acid and gamma valerolactone (GVL). The solvation medium plays an important role in the selective conversion of glucose to these platform chemicals and it is shown that the addition of co-solvents increases the selectivity towards desired products and minimizes the formation of undesired condensation/polymerization products and humins. Hence, it becomes imperative to understand the implications of the solvation of glucose by co-solvents on glucose conversion reactions. In the present paper, we implement OPLS-AA force-field based molecular dynamics simulations to investigate the solvation of glucose in water, in the presence of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF) and tetrahydrofuran (THF). The local arrangement of solvents around the glucose molecule is analyzed using 2-dimensional radial pair distribution functions and 3-dimensional volumetric maps. Additionally, lifetimes and activation free energies of hydrogen bonds between solvents and glucose and the tendency of glucose molecules to agglomerate were studied. It was observed that all the aforementioned co-solvents compete with water to be in the first solvation shell of glucose and significant amount of water is pushed to the second coordination shell.Though fewer water molecules are directly coordinated with glucose in the presence of co-solvents, they are bound strongly to it. Additionally, DMSO, THF and DMF tend to localize more around the hydrogen atom of the hydroxyl groups of selected carbon atoms of glucose. This preferential arrangement of co-solvents and water around glucose may play a role in facilitating the reaction pathway for the formation of HMF and levulinic acid and may reduce the likelihood of glucose' degradation to unwanted dehydration/rehydration products. Increasing the proportion of co-solvents also increases the hydrogen bond lifetimes between water and glucose and reduces the mobility of glucose molecules within the solvent. The reduced mobility of glucose molecules in the presence of cosolvents might be correlated to the experimentally observed reduction in the rate of formation of polymerization/condensation products and humins. † Electronic supplementary information (ESI) available: Centre of mass RDFs for glucose-co-solvents, co-solvent-water and water-water pairs are provided. See

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Magnesium (Mg) metal has been widely explored as an anode material for Mg-ion batteries (MIBs) owing to its large specific capacity and dendrite-free operation. However critical challenges, such as the formation of passivation layers during battery operation and anode-electrolyte-cathode incompatibilities, limit the practical application of Mg-metal anodes for MIBs. Motivated by the promise of group XIV elements (namely Si, Ge and Sn) as anodes for lithium-and sodium-ion batteries, here we conduct systematic first principles calculations to explore the thermodynamics and kinetics of group XIV anodes for Mg-ion batteries, and to identify the atomistic mechanisms of the electrochemical insertion reactions of Mg ions. We confirm the formation of amorphous MgxX phases (where X = Si, Ge, Sn) in anodes via the breaking of the stronger X-X bonding network replaced by weaker Mg-X bonding. Mg ions have higher diffusivities in Ge and Sn anodes than in Si, resulting from weaker Ge-Ge and Sn-Sn bonding networks. In addition, we identify thermodynamic instabilities of MgxX that require a small overpotential to avoid aggregation (plating) of Mg at anode/electrolyte interfaces. Such comprehensive first principles calculations demonstrate that amorphous Ge and crystalline Sn can be potentially effective anodes for practical applications in Mg-ion batteries.Consequently, the active search for alternative anode materials, in particular, insertion-type anodes for MIB, is necessary.Relative to Li-and Na-ion batteries, much less is known about suitable insertion-type anodes and the associated electrochemical reactions for MIBs due to the unique challenge of identifying host materials with appropriate electrochemical capacities that allow for repeated cyclic insertion and deinsertion. Although the ionic radius of Mg (0.72 Å) is smaller than that of Li and Na (0.76 Å X=Si, Ge, Sn, respectively (see S2 in Supporting Information). After correcting the diffusivities for the inherent stresses at different temperatures, Arrhenius relation 53D D E k T  was used to extrapolate the diffusivities at 300 K, Eba, kB, T, D0 being the energy barrier, the Boltzmann constant, temperature and the prefactor. Figure 4 shows the intrinsic diffusivities of Mg and X atoms at 300 K for different values of coupling parameters for all anodes considered here. The magnitudes of the residual compressive stresses are listed in energy barriers of Mg and X species in crystalline and amorphous X anodes; supporting table exhibiting the average inner stress induced by magnesiation in Mg-X systems (PDF).

Developing an electrolyte candidate with a wide voltage window, highly reversible cycling with Mg-metal anode, and without the use of any flammable solvents is a major challenge for rechargeable Mg batteries. While there have been several reports on Mg2+-conducting polymer electrolytes with high ionic conductivities, studies to determine their cycling performance and Mg-deposition overpotentials have been scarce. Here, we report a composite polymer electrolyte that exhibits a highly reversible cycling with Mg-metal anode at room temperature. The synthesized polymer electrolyte has a high conductivity of 0.16 mS cm–1 at room temperature, and the galvanostatic cycling tests of Mg | Mg symmetric cells reveal that the reversible Mg deposition/stripping occurs at low overpotentials of 0.1–0.3 V for up to 400 cycles. The cycling stability of this composite polymer electrolyte is unprecedented among ambient-temperature solid-state Mg electrolytes, and the observed overpotential values are even comparable to those of the present state-of-the-art liquid electrolytes.

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