The dropping cost of wind and solar power intensifies the need for low-cost, efficient energy storage, which together with renewables can displace fossil fuels. While batteries for transportation and portable devices emphasize energy density as a primary consideration, here, low-cost, ultra-abundant reactants deployable at massive (TWh) scale are essential. An air-breathing aqueous sulfur flow battery approach with ultralow energy cost is demonstrated at laboratory scale and shown to have economics similar to pumped hydroelectric storage without its geographical and environmental limitations.
Cement production is currently the largest single industrial emitter of CO2, accounting for ∼8% (2.8 Gtons/y) of global CO2emissions. Deep decarbonization of cement manufacturing will require remediation of both the CO2emissions due to the decomposition of CaCO3to CaO and that due to combustion of fossil fuels (primarily coal) in calcining (∼900 °C) and sintering (∼1,450 °C). Here, we demonstrate an electrochemical process that uses neutral water electrolysis to produce a pH gradient in which CaCO3is decarbonated at low pH and Ca(OH)2is precipitated at high pH, concurrently producing a high-purity O2/CO2gas mixture (1:2 molar ratio at stoichiometric operation) at the anode and H2at the cathode. We show that the solid Ca(OH)2product readily decomposes and reacts with SiO2to form alite, the majority cementitious phase in Portland cement. Electrochemical calcination produces concentrated gas streams from which CO2may be readily separated and sequestered, H2and/or O2may be used to generate electric power via fuel cells or combustors, O2may be used as a component of oxyfuel in the cement kiln to improve efficiency and lower CO2emissions, or the output gases may be used for other value-added processes such as liquid fuel production. Analysis shows that if the hydrogen produced by the reactor were combusted to heat the high-temperature kiln, the electrochemical cement process could be powered solely by renewable electricity.
The need for higher energy density rechargeable batteries has generated interest in alkali metal electrodes paired with solid electrolytes. However, metal penetration and electrolyte fracture at low current densities have emerged as fundamental barriers. Here, we show that for pure metals in the Li-Na-K system, the critical current densities scale inversely to mechanical deformation resistance. Furthermore, we demonstrate two electrode architectures in which the presence of a liquid phase enables high current densities while preserving the shape retention and packaging advantages of solid electrodes. First, biphasic Na-K alloys show K + critical current densities (with K-β″-Al2O3 electrolyte) that exceed 15 mA⋅cm -2 . Second, introducing a wetting interfacial film of Na-K liquid between Li metal and Li6.75La3Zr1.75Ta0.25O12 (LLZTO) solid electrolyte doubles the critical current density and permits cycling at areal capacities exceeding 3.5 mAh⋅cm -2 . These design approaches hold promise for overcoming electro-chemo-mechanical stability issues that have heretofore limited performance of solid-state metal batteries.
Nonaqueous redox flow batteries are a fast-growing area of research and development motivated by the need to develop lowcost energy storage systems. The identification of a highly conductive, yet selective membrane, is of paramount importance to enabling such a technology. Herein, we report the swelling behavior, ionic conductivity, and species crossover of lithiated Nafion 117 membranes immersed in three nonaqueous electrolytes (PC, PC : EC, and DMSO). Our results show that solvent volume fraction within the membrane has the greatest effect on both conductivity and crossover. An approximate linear relationship between diffusive crossover of neutral redox species (ferrocene) and the ionic conductivity of membrane was observed. As a secondary effect, the charge on redox species modifies crossover rates in accordance with Donnan exclusion. The selectivity of membrane is derived mathematically and compared to experimental results reported here. The relatively low selectivity for lithiated Nafion 117 in nonaqueous conditions suggests that new membranes are required for competitive nonaqueous redox flow batteries to be realized. Large scale energy storage for the electricity grid is widely considered to be necessary for enabling the use of intermittent renewables as primary power sources, for stabilizing power delivery in developing economies, and for facilitating a range of high-value grid services aimed at improving efficiency and lifetime.1 To date, broad market penetration of energy storage systems has been hindered primarily by high installation and operation costs, resulting in only ∼2.5% of the total electricity production in the US relying on grid energy storage predominantly in the form of pumped hydro-electric.2 However, the rapid and sustained growth of renewable electricity generation (e.g., solar photovoltaic, wind) continues to drive the need for advanced low cost energy storage.3-5 While certain energy storage technologies, such as lithium-ion (Li-ion) batteries, are currently at a price point to fulfill niche markets, 6 present electrical energy storage technologies, in general, are still not economically viable for wide-scale deployment, spurring research and development efforts worldwide. 7Redox flow batteries (RFBs) are electrochemical systems wellsuited for multi-hour energy storage and offer several key advantages over enclosed batteries (e.g., Li-ion, Lead-acid) including independent scaling of power and energy, long service life, improved safety, and simplified manufacturing. [8][9][10][11] Since their advent in the 1970s, 12 numerous aqueous redox chemistries have been developed but none has experienced widespread commercial success. The use of nonaqueous electrolytes in flow batteries is a nascent, yet burgeoning, concept.Transitioning from aqueous to nonaqueous electrolytes offers an extended window of electrochemical stability (> 3 V) and an enriched selection of redox materials due to the broader design space. However, this approach is not without technical hurdles such as the identificati...
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