Traditional planar solid-state Li-ion batteries suffer from an inherent coupling of energy and power densities such that an increase in one results in a decrease in the other. Moving from standard planar devices to three-dimensional ones has been shown to decouple these metrics allowing for both high-power and high-energy densities ¹. Recently, using standard semiconductor manufacturing techniques we have shown that nanoscale, three-dimensional, solid-state Li-ion storage systems can be competitive with traditional battery production².

Here we present wafer and nanoscale, three-dimensional solid-state Li-ion battery arrays fabricated in porous anodic aluminum oxide (AAO). Using Thompson’s method, which allows for the anodization of Al on a Si wafer³, tri-layers of Cu/W/Al are deposited by sputtering. The Al layer is then electropolished flat. Standard photolithography is then employed to mask-off and selectively anodize areas of the Al using 1M phosphoric acid, in a two-step method. The resulting nanopores have an average diameter of 400 nm and widely tunable pore lengths which are dependent on anodization time (500 nm-50 μm). More importantly, this method allows for perforation of the barrier layer at the bottom of the pore allowing for electrical contact to be made. The battery layers are vapor deposited by atomic layer deposition (ALD). A photograph of such a wafer and a cartoon of a completed device are provided in the Figure. The deposited stack is TiN/LiV₂O₅/Li₂PO₂N/SnO₂/TiN, where the V₂O₅ is electrochemically lithiated before the electrolyte layer is deposited. Details of the fabrication process, which also allows for highly flexible form factors, will be discussed. The power and energy densities of these devices will be reported as a function of their geometry.

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