Sputtered manganese oxide thin film on carbon nanotubes sheet as a flexible and binder-free electrode for supercapacitors

Summary By using oxalic acid (OA) as template and reducer, a novel approach is developed to prepare reduced graphene oxide films with capsular pores (C‐rGOFs) under a hydrothermal condition. The effect of preparation conditions including concentrations of OA and reaction temperatures on the films' structure and capacitive performances has been systematically investigated. The optimal C‐rGOF shows uniform capsule‐like morphology and exhibits a density of 1.18 g cm−3. Tested by using a two‐electrode system, the optimal film shows gravimetric specific capacitance of about 234.9 F g−1 and volumetric specific capacitance of 277.2 F cm−3. Additionally, the optimal film which shows good rate capability can retain 63.9% of initial capacitance at high scan rate of 1.0 V s−1, which is much higher than that of the controlling reduced graphene oxide film (rGOF, 180.5 F g−1, 373.6 F cm−3 and retain only 45.0% of its initial capacitance at 1.0 V s−1). The cells assembled by the optimal C‐rGOF exhibit maximum energy density of 7.5 Wh kg−1, power density of 16.9 kW kg−1, and excellent cycling stability with 91.2% capacitance retention after 21 000 cycles. It is believed that this method can be developed as a useful strategy to prepare rGO‐based materials for energy storage applications.

Section: Introductionmentioning

confidence: 99%

The electrochemical properties of reduced graphene oxide film with capsular pores prepared by using oxalic acid as template

Gao

Han

et al. 2019

“…In addition, SCs have unwieldy body that hinders their use in portable energy storage applications, while the development of miniaturized and flexibility flexible SCs has to been pursued in recent research effort and achieved significant advances. However, most of these studies have focused on electrode materials rather than on electrolyte; hence, problematic safety hazard and volume issues problems still hinder SC applications . Actually, SCs can be optimized by substituting for the liquid electrolyte with the solid electrolyte of conventional SCs such as the typical gel electrolytes (GEs) and ion‐exchange polymer electrolytes.…”

Section: Introductionmentioning

confidence: 99%

Multi‐walled carbon nanotubes incorporation into cross‐linked novel alkaline ion‐exchange membrane for high efficiency all‐solid‐state supercapacitors

Guo

Wang

et al. 2020

Summary An increasing number of focus has been paid to the study of supercapacitors in the context of the increasing demand for energy storage. As an important component of supercapacitors, the electrolyte has become a focus of research. In this work, an inexpensive and readily approach for synthesizing the polymer electrolytes was established by introducing multi‐walled carbon nanotubes (MWCNTs) as the filler on the basis of cross‐linked chitosan (CS) and poly‐(diallyldimethylammonium chloride) (PDDA), followed by a facile ion‐exchange in the KOH solution. The resultant MWCNTs‐CP‐OH− membrane manifests superb chemical stability, high hydroxide conductivity (0.033 S cm−1), and enhanced mechanical/chemical properties. Consequently, the fabricated all‐solid‐state supercapacitors using MWCNTs‐CP‐OH− composite membrane as a polymer electrolyte displayed prominent cyclic stability over 4000 cycles with 75.3% retention of the capacitance. Aforementioned merits make the MWCNTs‐CP‐OH− membrane highly promising candidate electrolyte material in all‐solid‐state supercapacitors.

“…Among them, MnO 2 is most potential transition metal oxide electrode materials due to its cost‐effectiveness, natural abundance, and high theoretical capacitance . However, low practical capacitance is usually produced as a result of the poor intrinsic electrical conductivity MnO 2 , which can be improved by doping carbon materials …”

Section: Introductionmentioning

confidence: 99%

“…15,16 However, low practical capacitance is usually produced as a result of the poor intrinsic electrical conductivity MnO 2 , 17 which can be improved by doping carbon materials. 18,19 Graphene, a most promising carbon material, become a research hotspot owing to the high electrical conductivity and large theoretical surface area. 20 However, the strong π-π interaction causes the face-to-face stacking of graphene sheets, which severely reduces accessible surface areas and effective ion transport channels.…”

Section: Introductionmentioning

confidence: 99%

Holey graphene/MnO ₂ nanosheets with open ion channels for high‐performance solid‐state asymmetric supercapacitors

Gao

Shu

et al. 2020

Holey graphene/MnO2 (HG/MnO2) composites with open ion channels are synthesized by an electrostatic self‐assembly method. The HG with rich in‐plane nanopores is prepared via a mild etching reaction first, followed by modified with poly‐diallyldimethylammoniumchloride (PDDA) to transfer the surface charge of HG nanosheets from negative to positive, which are eventually assembled on the negatively charged MnO2 nanosheets via electrostatic attraction. As a result, the HG allows ions to pass through the graphene sheet, improving the ion transport channels. Besides, the electrostatic self‐assembly between HG and MnO2 enables the composite a high conductivity, providing effective electron transport pathways. The HG and MnO2 sheets are observed to be tightly bounded by the transmission electron microscope (TEM), and the HG content in the composites is determined to be 9.6% to 20% by the thermogravimetric (TG) test. The HG/MnO2‐2 electrode with the HG content of around 14.8% displays the large specific capacitance of 219.3 F g−1 at 0.5 A g−1 and the high rate capacity of 134.7 F g−1 at 10 A g−1. Furthermore, the as‐prepared solid‐state asymmetric supercapacitors (SSAS) achieve a wide stable operating voltage of 1.8 V, a high energy density of 16.8 Wh kg−1 at the power density of 224.6 W kg−1, and low capacitance degradation of only 6.3% after 5000 cycles.