No abstract

There is a pressing need for high-rate cycling and cost-effective stationary energy storage systems in concomitance with the fast development of solar, wind, and other types of renewable sources of energy. Aqueous rechargeable Ca-ion batteries have the potential to meet the growing demands of stationary energy storage devices because they are abundant and safe; they can also be manufactured at a low-cost and have a higher volumetric capacity. In this study, we have demonstrated a lowcost, safe, aqueous Ca-ion battery that is based on a low potential, lower specific weight, in situ polymerized polyaniline as an anode, and a high redox-potential open-framework structured potassium copper hexacyanoferrate as a cathode. The charge−discharge mechanism of this battery includes doping/dedoping of NO 3 − at the anode, and intercalation and deintercalation of Ca-ion at the cathode. This Ca-ion battery works successfully in a 2.5 M Ca(NO 3 ) 2 aqueous electrolyte that exhibits 70 Wh kg −1 specific energy at 250 W kg −1 and even maintains a high energy density of 53 Wh kg −1 at a higher rate of 950 W kg −1 ; this indicates a good rate capability (calculation based on anode active mass). At 0.8 A g −1 , the battery provides an average specific capacity of 130 mA h g −1 , exhibiting high Coulombic efficiency (∼96%), with 95% capacity retention of over 200 cycles across its life span, which is a new achievement in the electrochemical performance of aqueous Ca-ion batteries. Furthermore, the calcium-ion storage mechanism is investigated using high-end X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements. Thus, this significant electrochemical performance of the anode and the cathode renders the battery a promising candidate in grid-scale storage applications.

Room-temperature sodium−sulfur (RT Na−S) battery cathodes suffer from poor conductivity, rapid dissolution of intermediate products, and potentially destructive volume change during cycling. The optimal way to minimize these problems could be a construction of a nanocomposite cathode scaffold combining different components selected for their particular functions. Here, we have combined the excellent electronic conductivity of reduced graphene oxide, polysulfide adsorption ability of the ultrafine manganese oxide nanocrystals, rapid ion/electron dissemination efficiency of nanosized sulfur, and outstanding mechanical stiffness and good electrical conductivity of Na alginate/polyaniline hybrid binder in a single electrode heterostructure. At 0.2 A g −1 , an RT Na−S battery containing the freestanding cathode delivers an initial specific cap acity of 631 mA h g −1 . By delivering a nominal discharge voltage of 1.81 V, our Na−S batteries bestow a high specific energy of 737 W h kg −1 at the 2nd cycle and 660 W h kg −1 was retained after 50 cycles. The effect of the amount of electrolyte additive is also well demonstrated in this study. The electrode fabrication process provides a new approach to tailor the design and preparation of effective cathodes for the room-temperature sodium−sulfur batteries.

Capacity and stability enhancement has been observed for MoSe2 covered with N, P-doped rGO sheets. The sodiation behaviour was also investigated through different ex situ studies.

No abstract