I remember seeing this about a year ago and thinking it was BS, but looking deeper and realizing it wasn't and had competitive efficiencies as well (not finding those details in this article though).

In addition to being a viable storage solution without as much dependence on limited materials, there are a few other potential pros: scalability as adding more storage could allow for increasing storage (and the storage I expect is relatively cheap compared to the compression/extraction equipment); potential symbiotic with sequestration installations (e.g. If the storage requirements are seasonal, it could be used to liquid extracted carbon for transport/long term sequestration, you could potentially even use the heat generated in that process for other purposes (e.g. If sequestered the heat isn't needed for subsequent evaporation and could be used in industrial or generation applications). It could make sense to put these on retired coal plants where they are already discussing use of thermal batteries to make power for more cross utilization of similar systems. Even if the systems need to be different, the spring workforce would benefit from economies of scale related to the worker skill sets (and the abandoned coal storage would be suitable for the larger footprints)