In terms of security, it is not wise to use GET method to logout from your applications.
To make more secure, use POST method.
<li>
<a href="{{ url('/logout') }}"
onclick="event.preventDefault();
document.getElementById('logout-form').submit();">
Logout
</a>
<form id="logout-form" action="{{ url('/logout') }}"
method="POST" style="display: none;">
{{ csrf_field() }}
</form>
</li>
In your controller
public function logout()
{
if(Sentinel::logout()){
return redirect('/');
}
}