No abstract

Aluminium is an attractive active material for battery systems due to its abundance, low cost, a gravimetric energy density of 2.98 Ah g −1 (c.f. lithium 3.86 Ah g −1 ) and a volumetric energy density of 8.04 Ah cm −3 (c.f. lithium 2.06 Ah cm −3 ). An aqueous electrolyte-based aluminium-ion cell is described using TiO 2 nanopowder as the negative electrode, CuHCF (copper-hexacyanoferrate) as the positive electrode and an electrolyte consisting of 1 mol dm −3 AlCl 3 and 1 mol dm −3 KCl. Voltammetric and galvanostatic analyses have shown that the discharge voltage is circa 1.5 V. Both a single-cell and 2-cell battery are demonstrated using 10 cm 2 electrodes and 126 and 256 mg total active material for the 1-cell and 2-cell batteries, respectively. The single cell exhibits an energy density of circa 15 mW h g −1 (combined positive and negative electrode masses) at a power density of 300 mW g −1 with energy efficiency remaining above 70% for over 1750 cycles. Initial characterisation shows that charge storage is due to the presence of Al 3+ . Cell capacity is circa 10 mA h g −1 and operates with a discharge voltage of circa 1.5 V (efficiency > 80% at 20C charge/discharge rate). Graphical AbstractKeyword Aqueous aluminium ion battery

In order to decrease the global dependence on fossil fuels, high energy density, rechargeable batteries with high charge capacity are required for mobile applications and efficient utilization of intermittent sources of renewable energy. Metal-air batteries are promising due to their high theoretical energy density. In particular, the iron-air battery, with a maximum specific energy output of 764 W h kg−1Fe, represents a low cost possibility. This paper considers an iron-air battery with nanocomposite electrodes, which achieves an energy density of 453 W h kg−1Fe and a maximum charge capacity of 814 mA h g−1Fe when cycled at a current density of 10 mA cm−2, with a cell voltage of 0.76 V. The cell was manufactured by 3D printing, allowing rapid modifications and improvements to be implemented before an optimized prototype can be manufactured using traditional computer numerical control machining.

Keywords:bifunctional air electrode palladium catalyst metal-air battery A B S T R A C T Designing a bifunctional air electrode which catalyses both the oxygen reduction and oxygen evolution reactions is an essential part of progress towards fully rechargeable metal-air batteries, such as the ironair battery which is environmentally friendly, low cost, and does not suffer risk of thermal runaway like lithium-ion batteries. This paper reports the development of a lightweight carbon-based bifunctional air electrode, catalysed by a small (0.5 mg cm À2 ) loading of 30 wt.% palladium on carbon. The Pd-catalysed air electrode showed good bifunctional activity, with 0.53 V potential difference between oxygen reduction and evolution. The Pd/C air electrode showed improved catalytic activity at high current densities (! 50 mA cm À2) and enhanced durability compared with two commercial Pt/C air electrodes produced by Gaskatel GmbH and Johnson Matthey. A stable oxygen evolution potential was maintained over 1,000 charge-discharge cycles.Crown

Figure 11. Layers of protection against TR in a high-power lithium-ion battery. The layers are ordered to how close they are to the internal protection of the cell.