The present invention relates to the use of porous structures comprising electrode active materials, which can be used as electrodes in electrochemical cells. In certain embodiments, the electrodes described herein can comprise a first porous support structure (e.g., a plurality of particles, which can be porous in certain cases) in which electrode active material is at least partially contained. The first porous support structure can be, in some embodiments, at least partially contained within the pores of a second porous support structure (e.g., an agglomeration of elongated fibers, a porous web formed by sintered particles, etc.) containing pores that are larger than the components of the first porous support structure.