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Electrolytes are an important component of electrochemical energy storage systems and their optimization is critical for emerging beyond lithium ion technologies. Here, an integrated computational-experimental approach is used to rank-order and aid the selection of suitable electrolytes for a Na-ion battery. We present an in silico strategy based on both thermodynamic and kinetic descriptors derived from molecular dynamics simulations to rationally arrive at optimal electrolytes for Na-ion batteries. We benchmarked various electrolytes (pure and binary mixtures of cyclic and acyclic carbonates with NaClO4 salt) to identify appropriate formulations with the overarching goal of simultaneously enhancing cell performance while meeting safety norms. Fundamental insights from computationally derived thermodynamic and kinetic data considerations coupled with atomistic-level description of the solvation dynamics is used to rank order the various electrolytes. Thermodynamic considerations based on free energy evaluation indicate EC:PC as a top electrolyte formulation under equilibrium conditions. However, kinetic descriptors which are important factors dictating the rate capability and power performance suggest EC:DMC and EC:EMC to be among the best formulations. Experimental verification of these optimized formulations was carried out by examining the electrochemical performance of various electrolytes in Na/TiO2nanotubes half cells with NaClO4 salt. Our rate capability studies confirm that EC:DMC and EC:EMC to be the best formulations. These optimized formulations have low-rate specific capacities 120–140 mAh/g whereas the lower ranked electrolytes (EC: DEC) have capacities 95 mAh/g. The various electrolytes are also evaluated from a safety perspective. Such results suggest encouraging prospects for this approach in the a priori prediction of optimal sodium ion systems with possible screening implications for novel battery formulations

Based on current estimates of reserves, coal could satisfy even a very much increased world energy demand for centuries, if only the emission of CO2 into the atmosphere could be curtailed. Here we present a method of CO2 disposal that is based on combining CO2 chemically with abundant raw materials to form stable carbonate minerals. A major advantage of this method is that the resulting waste product is thermodynamically stable and environmentally neutral. It is therefore possible to store large quantities permanently with minimal environmental impact and without the danger of an accidental release of CO2 which has proven fatal in quantities far smaller than contemplated here. The raw materials to bind CO2 exist in nature in large quantities in ultramafic rocks. They are readily accessible and far exceed what would be required to bind all CO2 that could possibly be generated by burning the entire fossil fuel reserves. In this paper we outline a specific process that we are currently investigating. Our initial rough cost estimate of about 3~/kWh is encouraging. The availability of a CO2 fixation technology would serve as insurance in case global warming, or the perception of global warming, would cause severe restrictions on CO2 emissions. If the increased energy demand of a growing world population is to be satisfied from coal, the implementation of such a technology would be unavoidable. Published by Elsevier Science Ltd

Surface enhanced Raman spectroscopy (SERS) data of W in acidic solution were characterized by modes associated with hydration (WO,(H2O), 942 cm') as well as modes characteristic of WO, (816 cm'). At applied anodic potentials, the WO,(H,O)5 content in the oxide was greater than the WO, content, while at applied cathodic potentials the WO, content was larger. These results are consistent with a bilayer film on W in acidic solution which consists of a compact inner layer of WO, and an outer layer of WOa(HzO)r Rotating disk electrode experiments (RIlE) demonstrated that the passive dissolution (i ass) ofW in acidic solution increased with the angular velocity of the electrode. An increase in i55, and a corresponding decrease in the thickness of the surface layer with increasing angular velocity is consistent with a reversible dissolution mechanism where dissolution is limited by the mass transport of a loosely bound WO,(H,O) layer from the surface. Electrochemical impedance spectroscopy measurements found that W dissolution in acidic solution was associated with an adsorption pseudocapacitance presumably due to the outer WO,(H,O)X layer. The value of this pseudocapacitance increased with increasing angular velocity, indicating thinning of the layer consistent with RIlE and SERS results. Results for W in alkaline solution are also presented.