Interesting that the records are incomplete.
Now, if there were these all black units were they composed of free black men or slaves being promised their freedom?
A mix. The southern congress didn't pass legislation allowing black combat soldiers, free or slave, until March 1865.
They were likely lost in the Richmond fire. Those that survive identify the officers of each unit and briefly describe some of their activities.
Now, if there were these all black units were they composed of free black men or slaves being promised their freedom?
Some of both. The majority of the troops in one of the units are known to have come from the Winder-Jackson military hospital staff in Richmond. It included both slaves and freedmen.