I'm in the humanities, so I don't know how helpful this will be.
A lit review should just be a quick summary of the major things that have been written in the area you're doing your dissertation in. It is meant to demonstrate that you are aware of what others have worked on in your field, and that you have read the key works for your diss. So for example for mine, which was on Italian history, I just had a few paragraphs about some of the 'big books' about the subject, and some articles that were directly relevant to my particular topic. You can also include a short discussion of where your topic fits into what has already been written - so if you're writing about topic X, which articles Y & Z touched on but didn't go into much detail about, you can say how your diss is exploring topic X which has been neglected in the existing literature. Hope that helps a bit!