To clarify, I am very much
not in favor of standalone lithium ion battery packs; I'm just talking about harnessing the inevitable unused capacity of electric car batteries to smooth out the grid. The revenue from which could incentivize faster adoption of EVs, since the marginal cost of getting an EV is falling. If you had to pay for them as dedicated energy storage, it would be horrifically expensive.
As you say, many other technologies are far more suited to this kind of use.
You may be right about the cycle count; EVs are designed to be daily drivers, but charging and discharging 40-50% of a battery daily is likely more punishing than 10-20%. Though even if that is the case, it would just push my analysis 10 years into the future, when cheaper batteries and PV will make up the difference.
