Magnesium-ion batteries (MIBs) offer improved safety, lower cost, and higher energy capacity. However, lack of cathode materials with considerable capacities in conventional nonaqueous electrolyte at ambient temperature is one of the great challenges for their practical applications. Here, we present high magnesium-ion storage performance and evidence for the electrochemical magnesiation of ammonium vanadium bronze NH4V4O10 as a cathode material for MIBs. NH4V4O10 was synthesized via a conventional hydrothermal reaction. It shows reversible magnesiation with an initial discharge capacity of 174.8 mAh g–1 and the average discharge voltage of ∼2.31 V (vs Mg/Mg2+) using 0.5 M Mg­(ClO4)2 in acetonitrile as the electrolyte. Cyclic voltammetry, galvanostatic, discharge–charge, FTIR, XPS, powder XRD, and elemental analyses unequivocally show evidence for the reversible magnesiation of the material and suggest that keeping the ammonium ions in the interlayer space of NH4V4O10 could be crucial for the structural stability with a sacrifice of initial capacity but much enhanced retention capacity. This is the first demonstration of electrochemical magnesiation with a high capacity above 2 V (vs Mg/Mg2+) using a conventional organic electrolyte with a relatively low water concentration.

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Freshwater in off-grid islands is sourced from rain, groundwater, or mainland imports, which are unreliable, limited, and expensive, respectively. Sustainable freshwater generation from desalination of abundant seawater is another alternative worth exploring. Model-based techno-economic simulations have focused on reverse osmosis desalination due to its low energy consumption and decreasing costs. However, reverse osmosis requires frequent and costly membrane replacement. Other desalination technologies have advantages such as less stringent feedwater requirements, but detailed studies are yet to be done. In this work, a techno-economic comparison of multi-effect distillation, multi-stage flash, mechanical vapor compression, and reverse osmosis coupled with solar photovoltaic-lithium ion-diesel hybrid system was performed by comparing power flows to study the interaction between energy and desalination components. Optimization with projected costs were then performed to investigate future trends. Lastly, we used stochastic generation and demand profiles to infer uncertainties in energy and desalination unit sizing. Reverse osmosis is favorable due to low energy and water costs, as well as possible compatibility with renewable energy systems. Multi-effect distillation and multi-stage flash may also be advantageous for low-risk applications due to system robustness.

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