Edit category output

You will need to use style parameter to define the type of list. And to remove <br /> tags from the list, set parameter 'echo' => 0 and str_replace to remove <br /> tag from the output.

$args = array(
    'orderby' => 'name',
    'show_count' => 0,
    'pad_counts' => 0,
    'hierarchical' => 1,
    'taxonomy' => $tax,
    'title_li' => '',
    'echo' => 0,
    'style' => 'simple'
);

echo '<span class="tags-button" style="list-style:none; float:left;">';
    echo str_replace( '<br />', '', wp_list_categories( $args ) );
echo '</span>';