There is another interesting class of power storage called "pumped-storage hydroelectricity" [1] - for example - there is one in use in Missouri that actually burst in 2005 [2]. Li-ion batteries have a round-trip efficiency of 80-90% - pumped-storage has ~70-80%.

[1] https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...

[2] https://en.wikipedia.org/wiki/Taum_Sauk_Hydroelectric_Power_...