work-life balance
Well, you will have to specify what you mean by work-life balance. Are there any existing studies that use this term? If so, write about them to help the reader understand your theme.
Is this limited to a particular industry?
This sounds like it will probably be an exploratory study, maybe using grounded theory with data from interviews. That would be cool! But you should focus on something that is an urgent need, some pressing matter, some problem you can help solve.
Google this: grounded theory constant comparison interview categories