Recently, Prof. Jianyong Yu and Prof. Faxue Li at our university collaborated with Prof. Tsu-Wei Chou at the University of Delaware (USA). The co-authored paper “Stretchable Wire-Shaped Asymmetric Supercapacitors Based on Pristine and MnO₂ Coated Carbon Nanotube Fibers” was published in the international prestigious research journal (ACS Nano2015, 9, 6088-6096).

        In the past decade, smart textiles have aroused extensive interests of domestic and abroad scholars. The emerged wire-shaped supercapacitors are able to integrate with well-developed textile technology in a highly versatile manner and have obvious advantages to apply into wearable lightweight, miniature and portable electronics. Therefore, the vital and first step to realize wearability is stretchability. However, it is still a challenge to fabricate wire-shaped supercapacitor with simultaneously robust mechanical stretchability and excellent electrochemical performance.

      In this paper,the asymmetric configuration was applied into the wire-shaped supercapacitors, extending the potential window from 0.8 V to 1.5 V, achieving tripled energy density and doubled power density compared to its asymmetric counterpart. The stretchable asymmetric WSS constituted of MnO₂/CNT hybrid fiber positive electrode, aerogel CNT fiber negative electrode and KOH-PVA electrolyte was endowed with the stretchability of up to 100% by using Dow XLA elastic fiber and the prestrainning-then-buckling approach. It possessed a high specific capacitance of around 157.53 µF cm^-1 at 50 mV s^-1 and a high energy density varying from 17.26 to 46.59 nWh cm^-1 with the corresponding powerdensity changing from 7.63 to 61.55 µW cm^-1. Remarkably, a cyclic tensile strain of up to 100% exerts negligible effects on the electrochemical performance of the stretchable asymmetric WSS. Moreover, after 10,000 galvanostatic charge-discharge cycles, the specific capacitance retains over 99%, demonstrating a long cyclic stability. The asymmetric configuration has been demonstrated to be the preferable supercapacitor structure to achieve higher operating voltage and high energy without sacrificing the power delivery and cycle stability.