(618bi) Micromachined High Surface Area Structures for Energy Storage Applications

A micron-scale, high surface area metallic structure was built based on a sequential multilayer robotic electroplating process. Alternating Ni and Cu layers were electrodeposited from their respective plating baths, followed by selective and partial chemical etching of the Cu layers to obtain a final high surface area Ni structure which was intended to serve as a backbone for the anode electrode in Zn-air microbatteries. The last step of anode fabrication process involves electrodeposition of Zn layer onto the Ni backbone structure. This fabrication resulted in a high surface area electrode with a reduction in internal resistance, which are crucial for high performance batteries, particularly at high discharge rates. Using this approach, an electrode composed of 10 pairs of Ni and Cu layers was built and tested. The surface area of the electrode was found to be more than 6 times higher than that of its footprint. Based on the discharge tests through various electrical loads, the areal capacity and energy density were measured as ~2.5 mAh/cm² and 2.5-3mWh/cm², respectively.