It is aimed at inorganic materials in general, and many of the calculations are bootstrapped from existing experimental crystal databases.
However, this is not to say there aren't some biases. A lot of the Materials Project collaborators work on battery research, so there is some bias towards battery materials. But people have used MP to search for new photocatalysts, for example (or carbon capture materials, new phosphors, thermoelectrics for solid-state refrigeration, lead-free piezoelectrics, transparent conductors, etc.. the list goes on).
However, this is not to say there aren't some biases. A lot of the Materials Project collaborators work on battery research, so there is some bias towards battery materials. But people have used MP to search for new photocatalysts, for example (or carbon capture materials, new phosphors, thermoelectrics for solid-state refrigeration, lead-free piezoelectrics, transparent conductors, etc.. the list goes on).