The present invention generally relates to batteries or other electrochemical devices, and systems and materials for use in these, including novel electrode materials and designs. In some embodiments, the present invention relates to small-scale batteries or microbatteries. For example, in one aspect of the invention, a battery may have a volume of no more than about 5 mm3, while having an energy density of at least about 400 W h/l. In some cases, the battery may include an electrode comprising a porous electroactive compound. In some embodiments, the pores of the porous electrode may be at least partially filled with a liquid such as a liquid electrolyte. The electrode may be formed from a unitary material. Other aspects of the invention are directed to techniques of making such electrodes or batteries, techniques of forming electrical connections to and packaging such batteries, techniques of using such electrodes or batteries, or the like.