https://onedrive.live.com/recoverykey 

Generate a New Recovery Key:

open cmd as admin

temporarily suspend bitlocker

manage-bde -protectors -disable %systemdrive%

elete the current recovery key:

manage-bde -protectors -delete %systemdrive% -type RecoveryPassword

generate a new recovery key:

manage-bde -protectors -add %systemdrive% -RecoveryPassword

Write down or print out the recovery key displayed after you run this command and keep it in a safe place!
re-enable the BitLocker protection:

manage-bde -protectors -enable %systemdrive%