read this before ordering a ZCell, page-9

keeping ZCell warm enough isn't really an issue - it has twice the mass and approx. twice the daily energy throughput that will warm the battery. It will likely need insulation in Europe, but insulation is cheap and there are truly cutting edge options available now.

The key thing that Redflow has done is make the battery tolerate extreme temperatures, such as in the tropics, including high humidity etc. As you note, its these hot regions where older battery technologies, including lithium, show their weakness the most due to accelerated capacity fade.

If you want a battery that lasts 10 years, without capacity fade, and regardless of temperature extremes, then Redflow is the only option right now.