Those photos you’ve posted are NiMH batteries… which discharge on their own at a fairly rapid rate even if you’re not using them at all. They’re also pretty big and heavy for the amount of power they provide (which, due to the self-discharge issue, is effectively a lot lower than the official number on the battery).

I strongly recommend investing in devices that use 18650 batteries. Those are similar to cell phone/laptop/electric car batteries. It’s worth investing in good brands of battery too - the quality varies significantly from brand to the next.

For example, basically all power tool batteries.

If they advertise ~12V, it means it is 3 'cells' of 18650s in series. Crack open the case on such a tool battery and you'll find just that -- 3 18650 batteries for the small size. A high capacity battery might instead of 6, with 3 pairs of 2 parallel batteries, doubling the capacity. And nothing but weight and size stops them from just making them ever-larger.

18-20v tools are 6 cells (18v is the nominal voltage, 20v is the 'max' voltage at full charge). Higher cap, more batteries in parallel in each series cell.

It is RARE to be able to service these unless you have some specialized skills. Typically, they are spot welded together, which can be dangerous to attempt to DIY. That said, often when a battery 'fails', it's actually just one 18650 that has failed and taken the others down with it.

That said, these days you do see other sizes. 21700s or even pouch batteries are starting to be more common when tools need more stored joules per unit volume.