WIKI [via link given above]
Currently, the most commonly used electrolyte for rechargeable Al batteries are acidic room temperature non-aqueous ionic liquids (IL) made of aluminium chloride (AlCl3) and 1-ethyl-3-methylimidazolium chloride ([EmIm]Cl). This addressed the initial issue that prevented Al batteries from becoming rechargeable: Al readily reacts to form a passivating oxide coating that is chemically inert and an extremely high potential is necessary to push ions through this layer. This high potential would degrade the electrolyte during recharging. The use of the ionic liquid as an electrolyte prevents passivation and allowed Al batteries to become rechargeable. As mentioned earlier, the active species in the IL electrolyte are AlCl4- and Al2Cl7-.
This electrolyte also faces multiple challenges. In the forefront of those challenges is their sensitivity to moisture. The electrolyte and water exothermically react to form gasses such as H2, Cl2 and HCl which causes cell expansion/distortion and reduction in performance (lower Coulombic efficiency, irreversible decay of capacity). The end result is an unstable cell, safety issues due leakage and corrosion, and more complex and costly manufacturing requirements. Liquid electrolytes have also faced issues such as poor electrode-electrolyte interface.
Beyond that... How well does it operate at -0F temps...
So this is established technology what Musk is using? Or has he solved a few of these problems?
Sounds like the chemistry can now work - in a lab, under lab QA conditions of cleanliness, temperature, controlled charge rates, vibration, shocks, and laboratory assembly and construction accuracy.
Let us applaud strongly the breakthrough.
Let us also wait for a few years of on-road service conditions and daily use by industry and consumers.
Industrial forklift recharging users?