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The main challenges to implement sustainable energy storage technologies are the utilization of earth-abundant recyclable materials, low costs, safe cell reactions and high performance, all in a single system. Aluminum batteries seem to cover these requirements. However, their practical performance is still not comparable with the state of the art high performance batteries. A key aspect to further development could be the combination of aluminum with charge storage materials like conductive polymers in non-aqueous electrolytes taking advantage of the properties of each material. This review presents the approaches and perspectives for rechargeable aluminum-based batteries as sustainable high-performance energy storage devices. The storage of electricity is a key component in the drive to a sustainable energy society. However, current energy storage devices, like high performance lithium-ion batteries, have constrained raw material resources, difficult recycling process and danger of flammability. Far less attention has been directed to the use lightweight aluminum based batteries in non-aqueous systems as aluminum has lower cost, is more abundant and is safer than lithium. Furthermore, its specific capacity of 2980 mAh g −1 and volumetric capacity of 8040 mAh cm −3 , respectively, are higher than lithium. The number of studies on rechargeable aluminum-based batteries in non-aqueous systems has increased 10-fold in the last decade (Figure 1). Therefore, it seems appropriate and timely to review the state of the art and the implementation of novel ideas and approaches made for rechargeable high performance aluminum-based batteries and reflect on the perspectives, challenges and limitations that these relatively new systems face. Gifford et al. described this novel battery system in 1988 with aluminum and graphite as the negative and positive electrodes respectively, in a Lewis acidic chloroaluminate ionic liquid at room temperature. Chloroaluminate anions intercalated into the graphite electrode reaching 64 Wh kg −1 specific energy at 1.7 V discharge voltage over 150 cycles and 80-90% coulombic efficiency.2 The same idea was taken up several years later by various research groups 1,[3][4][5]

This paper presents a feasibility study of a nonaqueous rechargeable battery based on aluminum and poly-(3,4-ethylenedioxythiophene) conductive polymer in a chloroaluminate ionic liquid. The polymer was electrodeposited on a vitreous carbon working electrode in a chloride aqueous solution and the structure was analyzed by scanning electron microscopy. The doping/de-doping mechanism of chloride ions into the polymer structure was studied using a quartz crystal microbalance and cyclic voltammetry. The deposition/ dissolution of the aluminum negative electrode were investigated by electrochemical and microscopic methods. Performance data were obtained with a laboratory-scale aluminum-conductive polymer battery at constant current showing an average cell discharge voltage of 1 V and specific energies of at least 84 Wh kg −1 referred to the mass of the polymer and aluminum. The system is novel and the paper outlines further research to improve the cell performance.

The growing demand for safe, sustainable and energy-dense energy storage devices has spurred intensive investigations into post-lithium battery technologies. Rechargeable aluminium batteries are promising candidates for future electrochemical energy storage systems due to the high theoretical volumetric capacity of aluminium and its natural abundance in the Earth’s crust, but their practical application is currently hindered by the limitations of presently available electrolytes. In this review, we highlight the key considerations needed to optimise the electrolyte design in relation to the aluminium battery system and critically assess the current state of knowledge and new concepts in liquid and quasi-solid polymer electrolytes, focusing primarily on non-aqueous systems. We then discuss the challenges and approaches in developing polymer electrolytes and finally provide an overview of the opportunities in quasi-solid electrolytes which could pave the way to achieving further improvements in aluminium batteries.