Is it safe to use session_id with MD5?

Question

I’m taking the session_id and putting it with MD5 encryption, to make a logout process.

I’d like to know if there’s any safety issue with that, so I’ll do it, or I’ll take some risk in the future?

<a href="painel.php?logoff=true&token=<?php echo md5(session_id()); ?>">Sair</a>

---

if($logoff && $token == md5(session_id())){
    unset($_SESSION['userlogin']);
    session_destroy();
    header('Location: ../painel');
}