In situ growth of Cu(OH)2@FeOOH nanotube arrays on catalytically deposited Cu current collector patterns for high-performance flexible in-plane micro-sized energy storage devices

Although integrated energy storage devices, such as in-plane micro-supercapacitors (MSCs), are attractive for powering portable microelectronic devices, it is still challenging to develop patterning techniques with high practicability and to rationally design and fabricate electrochemically active materials using feasible procedures. Here, we propose a facile solution-immersion method of fabricating interdigitated copper electrodes with an in situ converted array of Cu(OH)2@FeOOH nanotubes (NTs). A copper current collector can be patterned together with widely employed copper circuits by a facile copper-patterning approach based on cost-effective electroless catalytic deposition of copper with patterned Ag catalysts, which is greatly conducive to the integration of in-plane energy storage devices into microelectronic systems. Furthermore, the rationally designed array of Cu(OH)2@FeOOH NTs, which was converted in situ from the patterned copper electrodes, was demonstrated to be an excellent electrochemically active material with advantages that included a porous structure with a large specific surface area, excellent wettability by the electrolyte, short ion diffusion lengths and one-dimensional electron transport pathway. The resulting MSC devices that were fabricated with the interdigitated Cu(OH)2@FeOOH/Cu electrodes exhibited a high specific capacitance (58.0 mF cm−2 at 0.1 mA cm−2), a high energy density (18.07 μW h cm−2), excellent cycling stability and desirable flexibility.