Scalable fabrication of MnO2 nanostructure deposited on free-standing Ni nanocone arrays for ultrathin, flexible, high-performance micro-supercapacitor

Abstract

Ultrathin and flexible power sources are essential for the rapid development of portable and wearable electronics. The deployment of 3-dimensional (3-D) nanostructured materials on the current collectors has recently emerged as a promising strategy for preparing high-performance supercapacitors. Additionally, it is equally important to develop an appropriate device packaging technique, so as to maximize the improvement of the electrode performance characteristic. Herein, we develop a simple and efficient method for fabricating ultrathin and flexible supercapacitor electrodes containing a manganese dioxide (MnO₂) nanostructure deposited onto 3-D nickel nanocone arrays (NCAs). The MnO₂-NCAs electrode was prepared by an electro-deposition technology, which involves the cathode deposition of NCAs on a titanium carrier film as the current collector and subsequent anode deposited from the MnO₂ nanostructures as the active material. The electrode can be peeled off from the carrier film and thus the resulting freestanding electrode is as thin as 3 μm, and exhibits outstanding mechanical robustness, high specific capacitance (632 F g⁻¹), enhanced energy density (52.2 W h kg⁻¹) and excellent cycle performance (95.3% retention after 20 000 cycles). We further fabricated ultrathin supercapacitors with a total thickness of ∼27 μm, which achieved unprecedented features including superior energy density by volume (2.7 × 10⁻³ W h cm⁻³), superior flexibility and reliability. We demonstrated the application of the MnO₂-NCAs supercapacitor as an ultrathin power source such as driving a LED indicator. This technology may find vast applications in future wearable electronics.