/html/com_content/categories/default.php

<script>
    jQuery('.toggle').click(function (event) {
        event.preventDefault();
        var target = jQuery(this).attr('href');
        jQuery(target).toggleClass('hidden show');
    });
</script>

/html/com_content/categories/default_item.php

 <!-- Start Tiles -->
            <div class="tiles-image">
            <a href="/<?php echo JRoute::_(ContentHelperRoute::getCategoryRoute($item->id, $item->language));?>">
            <img src="/<?php echo $item->getParams()->get('image'); ?>" alt="<?php echo htmlspecialchars($item->getParams()->get('image_alt')); ?>" /></a>
            
            <?php if ($this->params->get('show_subcat_desc_cat') == 1) :?>
                <?php if ($item->description) : ?>
                    <span>
                    <div class="category description">
                          <a href="#info<?php echo $item->id;?>" class="toggle"><i class="fa fa-info-circle"></i> Info</a>
                          <div id="info<?php echo $item->id;?>" class="hidden">
                          <?php echo JHtml::_('content.prepare', $item->description, '', 'com_content.categories'); ?>
                        </div>                        
                    </div>
                    </span>
                <?php endif; ?>
            <?php endif; ?>
            </div>
<!-- End Tiles -->