Why would Germany need to run solely on battery for 2 weeks? Do you expect 2 weeks with 0 sun and wind all over continental Europe?
In any case, at $100/kwh, it would cost $250bn (EDIT: $25tn sorry) in batteries and maybe the same in installation costs to power Germany for 6 months a year. At the lower $20/kwh price tag it would be more like $5tn, compared to Germany's ~$4.5tn GDP. Over 10 years it could be done.
I mean not the whole Europe and this is obviously geography-dependent, but those "dark periods" are fairly common for Germany, as in there are weeks-long periods where Germany itself produces basically no electricity from wind or solar. In the most extreme case some years back, that "dark period" lasted almost two months.
This isn't to say they can't import it from elsewhere, they just can't make any of their own. Adding more capacity wouldn't do anything, it would take an incredible amount of batteries to handle the more extreme end of those "dark periods".
But that's my point. It would cost 1 year's worth of German GDP in batteries to power Germany on batteries for 6 months. No one would ever need that much battery backup. And while it's a huge number, it's not an unfathomably huge number.
That's the absolute most that handling the absolute worst case could cost today. It can only get cheaper from here. And there's no need for government debt.
In any case, at $100/kwh, it would cost $250bn (EDIT: $25tn sorry) in batteries and maybe the same in installation costs to power Germany for 6 months a year. At the lower $20/kwh price tag it would be more like $5tn, compared to Germany's ~$4.5tn GDP. Over 10 years it could be done.
(And 6 months' storage is maybe too much anyway)