Copy the UUID (in this case this would be 111DA74D-EDC4-498B-AE2C-50E07ACAE7CA) of the drive and run disktuil corestorage changeVolumePassPhrase theUUID.
Enter the old password, then twice the new one and after a few seconds you are done
fabian@heartofgold ~ diskutil corestorage changeVolumePassphrase 111DA74D-EDC4-498B-AE2C-50E07ACAE7CA
Repeat new passphrase:
Started CoreStorage operation
Logical Volume passphrase has been changed
Core Storage LV UUID: 111DA74D-EDC4-498B-AE2C-50E07ACAE7CA
Finished CoreStorage operation