Hierarchical VOOH hollow spheres for symmetrical and asymmetrical supercapacitor devices.

Xuyang Jing,Yifu Zhang,Hanmei Jiang,Na Xing,Wenjing Feng,Xiangyu Lu,Changgong Meng,Cong Wang

doi:10.1098/rsos.171768

Abstract

Hierarchical VOOH hollow spheres with low crystallinity composed of nanoparticles were prepared by a facile and template-free method, which involved a precipitation of precursor microspheres in aqueous solution at room temperature and subsequent hydrothermal reaction. Quasi-solid-state symmetric and asymmetric supercapacitor (SSC and ASC) devices were fabricated using hierarchical VOOH hollow spheres as the electrodes, and the electrochemical properties of the VOOH//VOOH SSC device and the VOOH//AC ASC device were studied by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS). Results demonstrated that the electrochemical performance of the VOOH//AC ASC device was better than that of the VOOH//VOOH SSC device. After 3000 cycles, the specific capacitance of the VOOH//AC ASC device retains 83% of the initial capacitance, while the VOOH//VOOH SSC device retains only 7.7%. Findings in this work proved that hierarchical VOOH hollow spheres could be a promising candidate as an ideal electrode material for supercapacitor devices.

Highlights

Energy storage devices including Li-ion batteries (LIBs), Na-ion batteries (NIBs), supercapacitors and fuel cells have played an important role as energy resources applied to various electronic devices such as portable and wearable electronics, hybrid electric vehicles, bio-implantable devices and LED devices [1,2,3,4,5,6,7,8,9,10]
VOOH hollow spheres have a rough surface comprising lots of nanoparticles. These characteristics indicate that VOOH hollow spheres might possess high specific surface area and hierarchical structure, which are proved by nitrogen adsorption– desorption isotherms [35]
The formation of hierarchical VOOH hollow spheres undergoes an inside-out Ostwald ripening [27]. Such structures indicate that hierarchical VOOH hollow spheres probably exhibit excellent electrochemical performance that can be applied to symmetric SC (SSC) and asymmetric SC (ASC) devices [36]

Summary

Introduction

Energy storage devices including Li-ion batteries (LIBs), Na-ion batteries (NIBs), supercapacitors and fuel cells have played an important role as energy resources applied to various electronic devices such as portable and wearable electronics, hybrid electric vehicles, bio-implantable devices and LED devices [1,2,3,4,5,6,7,8,9,10]. Xie’s group prepared various VOOH structures such as hollow dandelions [26], single-shelled/double-shelled hollow nanospheres [27], quadrangular nanorods [28] and hollow nanourchins [29] These reports were focused on the synthesis and shape control as well as the application to lithium-ion batteries [26], electrical switch [28] and the conversion to VO2 [29,30]. We synthesized hierarchical porous VOOH hollow spheres and studied their electrochemical properties as an SC’s electrode in aqueous and organic electrolytes [34,35]. We put emphasis on the electrochemical performance of hierarchical VOOH hollow spheres applied to SSC or ASC devices. Findings demonstrated that the electrochemical performance of the VOOH//AC ASC device was better than that of the VOOH//VOOH SSC device

Synthesis and characterization

Results and discussion

Conclusion