Lithium prices have gone down almost 60% in the last year.

Short-term storage isn't that bad, we have other battery chemistries or even completely different types (e.g. flow batteries). A bigger problem is seasonal storage, for which most batteries are far too expensive.

Grid level battery storage is very likely moving to other chemistries. The only reason to use lithium is that it's the chemistry that's the most developed right now, but lithium-ion batteries do not fundamentally speaking have the best properties for grid storage. Lithium-ion is great for energy density, but that's not a critical requirement for the grid.

For grid storage I think molten metal makes the most sense. It's a technology that was developed to be ideal for grid storage from the start. Flow cell batteries might also make sense. And then there's other storage technologies like compressed air, pumped hydro, storing kinetic energy, storing thermal energy, etc.

http://news.mit.edu/2016/battery-molten-metals-0112 https://www.youtube.com/watch?v=NiRrvxjrJ1U

The fears of peak lithium are greatly overblown. New mines are coming online now that the element is in higher demand and the price is going down.

But that's only one of many energy storage technologies that can be used for batteries. It's popular for mobile/portable uses because it has high energy density, but that's not really necessary for grid-scale energy storage; whatever's cheapest will do (which may well be pumping water uphill).

Lithium deposits?

Most of the lithium found today is extracted from brine reservoirs located in regions of southwestern South America and China.