A similar project in Australia used Tesla megapack batteries, which are lithium ion.

Another form of stored energy uses thermal. A large scale project to plug ~50,000 idle and abandoned oil wells in Kern County, California.

Probably worth noting that for states and utilities, consumer solar without batteries has become a liability and doesn't scale up. So effectively, all future consumer solar installations in California will likely have batteries. So there will be batteries at the consumer point, and centralized large scale battery farms like this one to address peak demand and prevent situations where blackouts may need to occur.

https://eepower.com/news/engineers-repurpose-oil-wells-as-so...