Enhanced electrical conductivity and stretchability of ionic-liquid PEDOT:PSS air-cathodes for aluminium-air batteries with long lifetime and high specific energy

A hydrogel film, poly-3,4-ethylenedioxythiophene (PEDOT):polystyrenesulfonate (PSS), containing an ionic liquid, is used as an air-cathode for a metal-air battery and its performance is investigated. This work presents the development of the air-cathode and the characterization of its physical, chemical and mechanical properties. Moreover, in view of wearable batteries, these air-cathodes are implemented within a flexible aluminium-air battery. It contains an aluminium anode, an electrolyte made of cellulose paper imbibed with an aqueous sodium chloride solution and the PEDOT:PSS air-cathode. Characterisation tests showed that the ionic liquid did not change the air-cathode chemically, while the electric conductivity increased considerably. The anode has an acceptable purity and was found to be resistant against self-corrosion. Discharge tests showed operating voltages up to 0.65 V, whereas two batteries in series could deliver up to 1.3 V at a current density of 0.9 mA cm(-2) for almost a day, sufficient for monitoring and medical devices. Several discharge tests with current densities from 0.25 up to 2.5 mA cm(-2) have presented operating lifetimes from 10 h up until over a day. At a current density of 2.8 mA cm(-2), the operating voltage and lifetime dropped considerably, explained by approaching the limiting current density of about 3 mA cm(-2), as evidenced by linear sweep voltammetry. The batteries showed high specific energies up to about 3140 Wh kg(-1). Mechanical tests revealed a sufficient stretchability of the air-cathode, even after battery discharge, implying an acceptable degree of wearability. Together with the reusability of the air-cathode, the battery is a promising route towards a low-cost viable way for wearable power supply for monitoring medical devices with long lifetimes and high specific energies. Optimization of the air-cathode could even lead to higher power applications.

Automated summary

A hydrogel film containing an ionic liquid is developed and used as an air-cathode for a metal-air battery. The air-cathode shows improved conductivity without chemical changes. The battery demonstrates high specific energies and sufficient stretchability, making it a promising option for wearable power supply.