On a BTRFS file system, the df command shows that the total number of inodes is 0. The Used and Free numbers are 0.
# df -i / Filesystem Inodes IUsed IFree IUse% Mounted on /dev/xvda2 0 0 0 - /
Note: The above output is taken from a virtual machine.
BTRFS does not use inodes in quite the same way as other filesystems, and it has no pre-determined limits, so it has nothing to count. The inode counts for BTRFS will always show zero due to the fact that BTRFS does not use inodes.