Transparent aqueous rechargeable sodium-ion battery

Aqueous sodium-ion battery is a sustainable, non-toxic, non-flammable, and low-cost alternative to lithium-ion batteries, while transparency is a growing requisite of modern and integrated devices that batteries have yet to fulfill. In this work we present the preparation of a transparent and rechargeable aqueous Na-ion battery, assembled with different thin films of carbon/cobalt-based nanomaterials as electrodes. Cobalt-filled carbon nanotubes and cobalt/cobalt oxide encapsulated carbon nanoparticles are simultaneously synthesized in one single experimental procedure and deposited as thin and transparent films through the liquid/liquid interfacial route. The former is used for the electrosynthesis of a Prussian blue analogue, yielding carbon nanotubes/cobalt hexacyanoferrate thin film nanocomposite used as cathodes, while the cobalt/cobalt oxide/carbon nanoparticles thin film is used as the anode. The transparent device is prepared using a diluted aqueous solution of NaCl as the electrolyte, reaching capacities of 22 mAh•g−1 at 2 A•g−1 that remains stable after 2000 charge/discharge cycles, and energy density of 19.2 Wh•kg−1 at 1.4 kW•kg−1.