I have found a solution myself.
<ul data-role="listview" data-filter="true">
<li class="custom-li">
<div class="custom-collapsible" data-name="1" data-role="collapsible" data-theme="b" data-content-theme="d" data-corners="false">
<h3>Userstory 1</h3>
<p>Content</p>
</div>
</li>
<li class="custom-li">
<div class="custom-collapsible" data-name="2" data-role="collapsible" data-theme="b" data-content-theme="d" data-corners="false">
<h3>Userstory 2</h3>
<p>Content</p>
</div>
</li>
</ul>
with css styling:
.custom-li {
padding: 0 !important;
border-width: 0 !important;
}
.custom-collapsible {
margin: 0 !important;
border-bottom-right-radius: 0 !important;
border-bottom-left-radius: 0 !important;
border-width:0 !important;
}
This is the demo: http://jsfiddle.net/lightbringer/jWaEv/