[Functional Artist]

It seems like it would make sense to leave a gap between each battery module for instance if we look at the Nissan Leaf book like modules we could put an 1/8 of an inch spacer in between them or 1/4" to allow the heat to dissipate essentially making them air cooled
I can think of space as being an issue but wouldn't there be a trade off for cooler battery operating temperature?
Is it to prevent them from bulging?
I'm new to this so please be gentle.

Yup, the "compression" or bolting them together helps to keep 'em in the proper shape & thickness

As an alternative kooling option, I'd thought of installing aluminum sheets in between each module
...but, have them stick out a bit (probably like 1/2" to 1") on each side, essentially adding cooling fins to the pack

 

[Functional Artist]

heatsinks essentially !

Yup, kinda like having your leg protrude, out from under the covers, if/when you get a bit too hot, while sleeping

 

[Functional Artist]

OMG, do you have a WebCam in our Master Bedroom or something ??? I call it the antenna and can't fall asleep without it sticking out (I guess I'm calling back to the Mother Ship)

He, He ya never know

 

[Functional Artist]

Also, after adding the heatsink/cooling fins, if ya enclosed the sides (air channels)
...& add a couple of fans

Ya just added a "forced air" cooling system, to the pack