flexible category listing

Try to get the categories listed like this:

<?php
$categories = wp_list_categories('orderby=name&show_count=0&title_li=&hide_empty=0&echo=0');
foreach ($categories as $cat) {
echo '<li><a href="'.$cat->category_nicename.'" title="'.$cat->cat_name.'">'.$cat->cat_name.'</a></li>';
}
?>

Why this is not working? Is there an other option to display the categories in the sidebar.php completly the way I like? I like to define the complete HTMl-code for the listing.

Any ideas?

Thanks.