Batteries contain metals with some structural rigidity themselves, and need encapsulation anyway. Could the batteries a spacecraft needs be used to build part of the physical structure, such as the arms holding up a solar panel on a com sat or a section of the hull protecting a crew in a spaceship? The point being to save some of the aluminium mass needed, rather than having the batteries being a box of payload that needs extra external physical support itself.
Do batteries need radiation protection? Do they cause bad secondary radiation? Li-ion batteries seem to contain iron massed metals like manganese and cobalt. Are there other risks like overheating, explosion, poisonous contamination. Has it even been done?