If your husband didn't live in your home during the last 6 months of the year, and you paid more than half the cost of keeping up the home for you and your children, you are "considered unmarried," which allows you to file as head of household. You will not need your husband's information.
If you do not meet those requirements to be "considered unmarried," then it depends on exactly what "separated" means in your case. If you are "legally separated under a divorce or separate maintenance decree," you are also considered unmarried and can file as head of household. Not all states have a legal separation or "separate maintenance decree" that meets the IRS requirements. So you would have to ask your divorce lawyer or, preferably, a tax lawyer, whether your separation meets the requirements. (Divorce lawyers often know a lot less about tax law than they think they know.)
Again, if you can file as head of household you will not need your husband's information.
