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 a
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 able to withstand repeated charging and discharging. In some cases, the electrode may have a plurality of protrusions and / or a wall (which may surround the protrusions, if present); however, in other cases, there may be no protrusions or walls. The electrode may be formed from a unitary material. In certain embodiments, a nonporous
electrolyte may be disposed onto the electrode. Such an
electrolyte may allow ionic transport (e.g., of
lithium ions) while preventing dendritic formation due to the lack of pores. In certain embodiments the
porous electrode has a surface that is denser than its interior. 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.