In most of the databases you can use the limiters on the left hand side of the screen to help limit the number of articles, either by date, article type, subject, etc. Example:
Try putting quotations around terms that are meant to be searched as one term (example: "lithium battery"). Without the quotes, the database may search for the terms separately.
If you find an article that relates really well to your research question, look at the subject terms that are listed for that article and use them in a new search.