Long-lasting grid battery | MIT Technology Review
https://www.technologyreview.com/2022/02/23/1044962/grid-battery-iron-clean-energy/
>>can store energy for between four and 12 hours
That's an interesting strategy. If they are in fact super cheap, then you could couple them with batteries for longer storage. My understanding is that is the storage and discharge cycles that determine battery life, so you have the cheapo batteries for Day 1 storage and then expensive ones for Day 2 and they last a lot longer b/c you don't need to tap into Day 2 supply very often.