Yan-Hua Liu,a Jian-Long Xu,*b Xu Gao,b Yi-Lin Sun,c Jing-Jing Lv,b Su Shen,a Lin-Sen Chen*a and Sui-Dong Wang*b
aCollege of Physics, Optoelectronics and Energy, Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province & Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou, Jiangsu 215006, P. R. China.
bInstitute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou, Jiangsu 215123, P. R. China.
cInstitute of Microelectronics, Tsinghua National Laboratory for Information Science and Technology(TNList), Tsinghua University, Beijing 100084, P. R. China
Fully integrated ultrathin, transparent and foldable energy storage devices are essential for the development of smart wearable electronics, yet typical supercapacitor electrodes are substrate-supported which limits their thickness, transparency and mechanical properties. Employing freestanding transparent electrodes with no substrate support could bring ultrathin, foldable and designable supercapacitors closer to reality. Herein, we report a freestanding, ultrathin (<5 μm), highly conductive (3×104 S cm-1), highly transparent (>84% transmittance) and foldable metallic network electrode, loaded with MnO2 by electrochemical deposition, as a supercapacitor electrode. The freestanding metallic network electrode is fabricated via a simple and lowcost laser direct-writing micro-patterning technique followed by a selective electrodeposition process, where the metallic network patterns, network periods, metal thickness and also the electrode film patterns can be designed for different applications. The obtained freestanding MnO2@Ni network electrode delivers an outstanding areal capacitance of 80.7 mF cm-2 and long-term performance stability (96.3% after 10000cycles). Moreover, the symmetric solid-state supercapacitors employing the freestanding MnO2@Ni network electrode not only show high areal capacitance as well as high optical transparency (>80% transmittance), but also can be tailored, attached, folded, rolled up, and crumpled into any object or various shapes with only slight performance degradation. The advent of such freestanding transparent metallic network electrodes may open up a new avenue for realizing fully integrated ultrathin, foldable and designable supercapacitors towards self-powered wearable electronics.