They don’t operate below 10c or above 40c due to their chemistry so unless your location has a very temperate climate 24/7/365 the energy density is the least of your worries.
As long as your average temperature is between 10C and 40C, with sufficient volume of water you'd have enough thermal mass to ride out the day and night fluctuations.
In some climates, you might need to get fancier to try to nudge the temperature in the right direction. Hot climates shouldn't be much of a problem, but even if they are you could use fans or vents to create a system that's insulated and shaded during the day but open to outside air at night. In cold climates, you might want to have a greenhouse kind of setup to capture some extra heat and prevent convection cooling so it stays above 10°C.
Li-ion doesn’t have this problem as much heck the PANASONIC NCR-18650 can be discharged safely even at 60c.
That means, for any large enough scale plant, the cost to keep it at a fixed temperature diminishes to insignificant.