This whole Stanford aluminum battery thing had me scratching my head for a day. I read the full abstract from another reddit post (which I have pasted below) and it's pretty obvious now. The authors report a specific capacity of 70 mAh / g. This is SO LOW and immediately prevents it from being a competitive material. Pretty much all commercial lithium ion cathode materials have capacities above 160 mAh / g. It's not even close. Also the voltage is very low at only 2V... this battery is a joke and has no commercial viability. The authors and PIs both know this (I hope.) It's frustrating that these battery breakthrough stories keep getting this much coverage, but gotta get page views I guess. PS Elon was right

The development of new rechargeable battery systems could fuel various energy applications, from personal electronics to grid storage. Rechargeable aluminium-based batteries offer the possibilities of low cost and low flammability, together with three-electron-redox properties leading to high capacity. However, research efforts over the past 30 years have encountered numerous problems, such as cathode material disintegration, low cell discharge voltage (about 0.55 volts), capacitive behaviour without discharge voltage plateaus (1.1–0.2 volts or 1.8–0.8 volts) and insufficient cycle life (less than 100 cycles) with rapid capacity decay (by 26–85 per cent over 100 cycles). Here we present a rechargeable aluminium battery with high-rate capability that uses an aluminium metal anode and a three-dimensional graphitic-foam cathode. The battery operates through the electrochemical deposition and dissolution of aluminium at the anode, and intercalation/de-intercalation of chloroaluminate anions in the graphite, using a non-flammable ionic liquid electrolyte. The cell exhibits well-defined discharge voltage plateaus near 2 volts, a specific capacity of about 70 mA h g–1 and a Coulombic efficiency of approximately 98 per cent. The cathode was found to enable fast anion diffusion and intercalation, affording charging times of around one minute with a current density of ~4,000 mA g–1 (equivalent to ~3,000 W kg–1), and to withstand more than 7,500 cycles without capacity decay.