Energy storage technology has received significant attention for portable electronic devices, electric vehicle propulsion, bulk electricity storage at power stations, and load leveling of renewable sources, such as solar energy and wind power. Lithium ion batteries have dominated most of the first two applications. For the last two cases, however, moving beyond lithium batteries to the element that lies below-sodium-is a sensible step that offers sustainability and cost-effectiveness. This requires an evaluation of the science underpinning these devices, including the discovery of new materials, their electrochemistry, and an increased understanding of ion mobility based on computational methods. The Review considers some of the current scientific issues underpinning sodium ion batteries.

The emerging chemistry of sodium ion batteries for electrochemical energy storage.

Owing to almost unmatched volumetric energy density, Li-ion batteries have dominated the portable electronics industry and solid state electrochemical literature for the past 20 years. Not only will that continue, but they are also now powering plug-in hybrid electric vehicles and electric vehicles. In light of possible concerns over rising lithium costs in the future, Na and Na-ion batteries have re-emerged as candidates for medium and large-scale stationary energy storage, especially as a result of heightened interest in renewable energy sources that provide intermittent power which needs to be load-levelled. The sodium-ion battery field presents many solid state materials design challenges, and rising to that call in the past couple of years, several reports of new sodium-ion technologies and electrode materials have surfaced. These range from high-temperature air electrodes to new layered oxides, polyanion-based materials, carbons and other insertion materials for sodium-ion batteries, many of which hold promise for future sodium-based energy storage applications. In this article, the challenges of current high-temperature sodium technologies including Na-S and Na-NiCl2 and new molten sodium technology, Na-O2 are summarized. Recent advancements in positive and negative electrode materials suitable for Na-ion and hybrid Na/Li-ion cells are reviewed, along with the prospects for future developments.

Sodium and sodium-ion energy storage batteries

Dolomite: occurrence, evolution and economically important associations

: Geochemical reaction path modeling is useful for rapidly assessing the extent of water-aqueous-gas interactions both in natural systems and in industrial processes. Modeling of some systems, such as those at low temperature with relatively high hydrologic flow rates, or those perturbed by the subsurface injection of industrial waste such as CO2 or H2S, must account for the relatively slow kinetics of mineral-gas-water interactions. We have therefore compiled parameters conforming to a general Arrhenius-type rate equation, for over 70 minerals, including phases from all the major classes of silicates, most carbonates, and many other non-silicates. These data have been added to a computer code that simulates an infinitely well-stirred batch reactor, allowing computation of mass transfer as a function of time. Actual equilibration rates are expected to be much slower than those predicted by the selected computer code, primarily because actual geochemical processes commonly involve flow through porous or fractured media, wherein the development of concentration gradients in the aqueous phase near mineral surfaces, which results in decreased absolute chemical affinity and slower reaction rates. Further differences between observed and computed reaction rates may occur because of variables beyond the scope of most geochemical simulators, such as variation in grain size, aquifer heterogeneity, preferred fluid flow paths, primary and secondary mineral coatings, and secondary minerals that may lead to decreased porosity and clogged pore throats.

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A Compilation of Rate Parameters of Water-Mineral Interaction Kinetics for Application to Geochemical Modeling

Effects of climate on chemical_ weathering in watersheds

Strontium as a tracer of weathering processes in a silicate catchment polluted by acid atmospheric inputs, Strengbach, France

Central Andes in Bolivia and northern Chile contain numerous internal drainage basins occupied by saline lakes and salt crusts (salars). Salts in inflow waters stem from two origins: alteration of volcanic rocks, which produces dilute waters, and brine recycling, which leads to brackish waters. Chilean alteration waters are three times more concentrated in average than Bolivian waters, which is related to a higher sulfur content in Chilean volcanoes. Brackish inflows stem from brines which leak out from present salars and mix with dilute groundwater. Most of the incoming salts are recycled salts. The cycling process is likely to have begun when ancient salars were buried by volcanic eruptions. Three major brine groups are found in Andean salars: alkaline, sulfate-rich, and calcium-rich brines. Evaporation modeling of inflows shows good agreement between predicted and observed brines in Chile. Alkaline salars are completely lacking in Chile, which is accounted for by higher sulfate and lower alkalinity of inflow waters, in turn related to the suspected higher sulfur content in Chilean volcanic rocks. Six Bolivian salars are alkaline, a lower number than that predicted by evaporative modeling. Deposition on the drainage basin of eolian sulfur eroded from native deposits shifts the initial alkaline evolution to sulfate brines. The occurrence of calcium-rich brines in Andean salars is not compatible with volcanic drainage basins, which can only produce alkaline or sulfate-rich weathering waters. The discrepancy is likely due to recycled calcic brines from ancient salars in sedimentary basins, now buried below volcanic formations. Calcic salars are not in equilibrium with their volcanic environment and may slowly change with time to sulfate-rich salars.

Origin of Salts and Brine Evolution of Bolivian and Chilean Salars

Influence of acid atmospheric inputs on surface water chemistry and mineral fluxes in a declining spruce stand within a small granitic catchment (Vosges Massif, France).

Hydrochemical budgets have been obtained for the 3-yr period 1986–89 at Strengbach, a small granitic basin in the Vosges mountains (north-eastern France). Here, the spruce forest shows both yellowing and crown thinning, symptoms of forest decline. Water amount and surface water chemistry were monitored in each ecosystem compartment. Bulk precipitation is acidic. Some pollution episodes occur in winter and early spring, but the annual bulk deposition acidity is rather low. Throughfall however, is much more concentrated, particularly for H+ and associated strong acid anions. These inputs come as occult deposits which comprise major ecosystem inputs, as confirmed by the chloride balance for the catchment. Input-output budgets for the catchment indicate a net deficit of base cations, especially calcium. Sulfate also shows a net loss while N budget is well balanced. As the soil exchange capacity is nearly exhausted for base cations, and dominated by H+ and Al, the neutralization of incident acid inputs occurs mainly in the weathered bedrock. Silicate weathering processes lead to high losses of cations and of silica. Aluminium hydroxide is precipitated; however, bicarbonate remains very low indicating poorly-buffered surface water.

Bertrand Fritz

Papers

Strontium as a tracer of weathering processes in a silicate catchment polluted by acid atmospheric inputs, Strengbach, France

Origin of Salts and Brine Evolution of Bolivian and Chilean Salars

Influence of acid atmospheric inputs on surface water chemistry and mineral fluxes in a declining spruce stand within a small granitic catchment (Vosges Massif, France).

Hydrochemical budgets of a small forested granitic catchment exposed to acid deposition: The strengbach catchment case study (Vosges massif, France)

Dissolution of subglacial volcanic glasses from Iceland: laboratory study and modelling