Aluminum/air electrochemical cells

Abstract

Aluminum (Al) is a very promising energy carrier given its high capacity and energy density, low cost, earth abundance and environmental benignity. The Al/air battery as a kind of metal/air electrochemical cell attracts tremendous attention. Traditional Al/air batteries suffer from the self-corrosion and related safety problems. In this work, three new approaches were investigated to tackle these challenges and to develop high-performance Al/air cells: (1) incorporate an additional hydrogen/air fuel cell to utilize the hydrogen from the parasitic reaction; (2) utilize organic alkaline anolyte instead of aqueous one in a dual- or tri- electrolyte membrane fuel cell; (3) integrate the microfluidic fuel cell structure into the Al/air battery. The self-corrosion reaction is either turned into a beneficial reaction or significantly inhibited through these approaches. Moreover, the Al/air cells exhibited improved current and/or voltage performance. With an alkaline anolyte and an acidic catholyte, the cell exhibited an open-circuit voltage of 2.2 V, the highest value so far reported. The capacity and energy density of the Al/air battery increased over 20 folds when conventional aqueous electrolyte was replaced with the selected organic electrolyte. The adoption of microfluidic fuel cell concept effectively miniaturized the Al/air cell, eliminated the self-corrosion during battery stand-by, and led to a higher current and power output than membrane-based cells due to reduced cell resistance. Overall, Al/air electrochemical cells with better performance and higher feasibility were developed based on the above three approaches, when they are used alone or collectively.