There are a range of non-lithium storage technologies that are much more suited to the task. As you say, lithium batteries are only suitable for diurnal mismatch and dealing with curtailment. But there is a lot of investment going into non-lithium batteries, electro-mechanical, etc to solve the bigger issues of seasonal storage and resilience. A lot of people like vanadium flow batteries for their unique properties but that may create a supply chain issue. I also like iron based solutions. But they will take a long time to validate and lithium LFP is ready now.