Lithium Trapping in Microbatteries Based on Lithium‐ and Cu 2 O‐Coated Copper Nanorods

Microbatteries based on three‐dimensional (3D) electrodes composed of thin films of Li and Cu 2 O coated on Cu nanorod current collectors by electrodeposition and spontaneous oxidation, respectively, are described and characterised electrochemically. High‐resolution scanning electron microscopy (HR‐SEM) data indicate that the Li electrodeposition resulted in a homogenous coverage of the Cu nanorods and elemental analyses were also used to determine the amount of lithium in the Li‐coated electrodes. The results show that 3D Cu 2 O/Cu electrodes can be cycled versus 3D Li/Cu electrodes but that the capacity decreased during the cycling due to Li trapping in the Cu current collector of the 3D Li/Cu electrode. These findings highlight the problem of using copper current collectors together with metallic lithium as the formation of a solid solution yields considerable losses of electroactive lithium and hence capacity.