129MWh is a laughable amount of storage when you need at minimum 10000MWh per day for 1mln people. So you would need at least $12.5bln to build enough plants for just one day per 1mln people. And that's not counting maintenance. For that price 2-3 nuclear plants can be built which can last 30-50 years unlike the 10-20 years of lithium storage.

Instead of hideously expensive (and potentially explosive) lithium storage, solution should be synthesizing and storing some form of gas. This gas can then be produced and stored in underground locations during summer, and then spent during winter.