Samsung is reportedly working on a flexible battery for smartphones with a capacity of at least 3000mAh. This is in line with the capacity of batteries in current models. Samsung would work on a fully flexible smartphone.
Samsung has already shown a flexible battery, but it did not go beyond a capacity of 210mAh. That is about the battery that goes into a smartwatch. To make a smartphone bendable, Samsung will need many components that are bendable. Cover screens are flexible in themselves, although there is usually non-bendable glass over them for protection.
There have been rumors about flexible Samsung smartphones for years. The manufacturer does use curved screens for, among other things, Galaxy S and Note devices, such as the S9, Note 8 and S8. It contains non-bendable batteries.