De man badblocks
:
-o output_file
Write the list of bad blocks to the specified file. Without
this option, badblocks displays the list on its standard output.
The format of this file is suitable for use by the -l option in
e2fsck(8) or mke2fs(8).
Então, o caminho correto seria:
badblocks -o filename /dev/sde1
mkfs.vfat -l filename /dev/sde1