Melamine sponge modified by graphene/polypyrrole as highly compressible supercapacitor electrodes

Compressible supercapacitors are particularly important in wearable energy storage because they can maintain desired levels of performance during repeated compressing and recovering process. However, it is still challenging for a compressible supercapacitor to maintain excellent electrochemical performances under highly compressive strain. Herein, a highly compressible reduced graphene oxide-polypyrrole-reduced graphene oxide-melamine sponge (G-PPy-G-MS) electrode is prepared via coating polypyrrole and a double layer of reduced graphene oxide on the melamine sponge. Polypyrrole provides the capability of high redox pseudocapacitive charge storage for the electrode, the electronic conductivity of the sample is greatly promoted by the double layer of reduced graphene oxide, and the melamine sponge ensures remarkable compressive properties. As a result, under the high compressive strain of 80 %, the G-PPy-G-MS electrode possesses a high specific capacitance of 464.10 F g−1, superior rate performance with 44.47 % retention from 0.5 A g−1 to 10 A g−1, and desirable cycling stability (remains 85.43 % after 5000 cycles). Moreover, the all-solid-state symmetric supercapacitor constructed by G-PPy-G-MS maintains 97.48 % specific capacitance after 100 compressing-recovering cycles at the high strain of 80 %. This work develops a novel and feasible strategy to fabricate composite electrodes with high electrochemical and mechanical performances for compressible supercapacitors.