It depends on what you value. For performance and power density, nothing really beats lithium at the moment.

However, for grid-scale battery these parameters are not necessarily very important. What matters most is cost over the lifetime, and that's wher zinc batteries could be useful. They have the potential to be much cheaper than the cheapest lithium batteries.

They do. They are just looking for cheap way to store energy. They don't care if batteries are big, heavy and less efficient, they need something as cheap as possible for a range of use cases where cost is important.

Lithium is expensive. My bet is that, on the long term, sodium will be used for such use cases. But in practice decision must account for practical limitations, primarily supply chain