The trade-off in Auto vs Storage applications is power density vs cycle life. Telsa uses NCA chemistry in its auto applications for its superior power density and faster recharging rates. Tesla uses NMC chemistry for energy storage products like Powerwall and Powerpack for its superior life span (number of charge/recharge cycles to a given loss of capacity).
Why Tesla's grid batteries will use two different chemistries
"An NCA battery typically has a shorter cycle life and a higher energy density (and less stability). ... But an NMC battery also typically has a lower cost of energy because of the ability of an NMC battery to cycle with more stability than an NCA battery" (May 18, 2015)