A chemical reaction generates an electrical charge inside the battery shell, and the charge is then used to power devices. Since it's a chemical reaction that generates the electricity, temperature can slow down or speed up the reaction. Since batteries have a limited amount of chemical in them, it seems reasonable to think that refrigeration will slow down the reaction until we're ready to use it. You might be too young to remember when it was necessary to add water to car batteries. Chemical reactions are accelerated by high temperatures and retarded by low temperatures.
Refrigerated storage is neither necessary nor recommended.
A common misconception is that batteries are generating electricity even when they're not being used. That's not the case. Until somebody throws the switch, a battery only has electrical potential . If no juice is flowing, no chemicals are reacting, and there's no point in refrigerating the battery. That's why car batteries don't work well in subzero temperatures.