MnO2 porous carbon composite from cellulose enabling high gravimetric/volumetric performance for supercapacitor.

Preparing electrode material integrated with high gravimetric/volumetric capacitance and fast electron/ion transfer is crucial for the practical application. Owing to the structural contradiction, it is a big challenge to construct electrode material with high packing density, sufficient ion transport channels, and fast electronic transfer pathways. Herein, MnO2 porous carbon composite with abundant porous structure and 3D carbon skeleton was facilely fabricated from Linum usitatissimum. L stems via NaOH activation and MnO2 introduction. The in-situ introduced MnO2 not only increases the packing density and the electrical conductivity of the porous carbon but also provides more active sites for oxidation reactions. These unique characteristics endow the resultant MnO2 porous carbon composite with remarkable gravimetric capacitance of 549 F g-1, volumetric capacitance of 378 F cm-3, and capacitance retention of 54.9 %. Giving the simple process and low cost, this work might offer a new approach for structural design and the practical application of high-performance electrode materials.

Construction of ion/electron transfer multi-channels for the composite film electrode from GO and cellulose derived porous carbon in supercapacitor.

Due to excellent flexibility and dispersibility, 2D graphene oxide (GO) is regarded as one of the prospective materials for preparing self-supporting electrode material. Nevertheless, the self-stacking characteristic of GO significantly restricts the ion transmission and accessibility in GO-based electrodes, especially in the direction perpendicular to the electrode surface. Herein, a novel composite film was fabricated from GO and 3D porous carbon (PC) through vacuum filtration combined with thermal reduction strategy. The combination of GO and PC not only avoids the self-stacking of GO, but also exposes more active sites for ions in the inner. A massive released nitrogen and oxygen-containing gases during the thermal reduction endows the reduced graphene oxide (RGO) with abundant porous and CC, which contributes to the energy storage in the direction perpendicular to the electrode surface. Besides, the high specific surface area of the prepared composite film is favorable for the storage and release of charge on the electrode surface. Benefiting from the above characteristics, the electrode assembled by the as-prepared film exhibits ultrahigh areal/volumetric specific capacitance in supercapacitor and ZIHCs (Zinc ion hybrid capacitors). This work provides a promising approach for the development of advanced self-supported electrode materials with desirable electrochemical properties.