Realizing a Low-Cost and Sustainable Rechargeable Aqueous Aluminum-Metal Battery with Exfoliated Graphite Cathode

A rechargeable battery with earth-abundant and low-cost aluminum (Al) metal as one of the electrodes holds immense promise as a sustainable and affordable energy storage device. The high gravimetric/volumetric storage capacities (2981 mAh g(-1)/8056 mAh cm(-3)) of Al along with the ability to exchange three electrons per cation are certainly advantageous for achieving batteries capable of delivering high energy and power densities. A recent yet exemplary example is the chloroaluminate electrolyte-based Al-metal battery with a carbonaceous cathode. However, chloroaluminate electrolytes are highly reactive to most of the metals and stainless steel, moisture sensitive, and expensive. These demerits of chloroaluminate electrolytes will certainly be impediments for mass-scale production of safe and low-cost Al-metal batteries. The use of water-based electrolyte in rechargeable Al-metal batteries is expected to mitigate these challenges. Herein, we report the working of a rechargeable aqueous Al-metal battery with electrochemically pretreated Al and graphite as electrodes. The electrochemical pretreatment process resulted in exfoliation of graphite electrode, which is termed as graphite foam. The discharge capacities for the initial and 50th cycles are 213 and 88 mAh g(-1), respectively, at a current density of 0.5 A g(-1). It is also found that the lifespan of the investigated Al-graphite cell is limited by the dissolution of the Al electrode during consecutive charge/discharge processes. But, the immense promise of long-term sustainability of the system is shown by mechanical recharge of the Al electrode. The uniqueness of the illustrated Al-graphite battery is that it takes the advantage of extremely low-cost resources and could be easily assembled at ambient atmosphere.