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To effectively fabricate and use MnO 2 in supercapacitors, a graphene/polyvinylidene fluoride (PVDF) composite binder has been designed and fabricated. The 5% CBE shows higher specific capacitance (220 F g −1 ) than the 5% PBE (202 F g −1 ) at 0.5 A g −1 with an identical amount of graphene, which is physically mixed in the manufacturing process of electrodes. It has been found that the graphene content in the composite binder has a significant effect on electrochemical activities of electrodes and capacitors manufactured from these methods. A maximum specific capacitance of 220 F g −1 can be obtained with graphene mass ratios up to 5 wt%. In addition, the 5% CBE shows excellent cycling stability that is over 90.07% of the initial specific capacitance and is retained after 1000 cycles. The improved electrochemical performance can be attributed to the formation of chemical bond between graphene and PVDF in the composite binder, which provides an effective electron pathway by bridging MnO 2 particles in the electrodes that leads to rapid electron transfer and low charge transfer resistance. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract An efficient and scalable method to improve the capacitive properties of MnO 2 is reported by inducing graphene (rGO) and oxygen vacancies via a thermal treatment in air, in which graphene oxide (GO) is in situ reduced and graphene/MnO x (rGO/MnO x) composite without oxygen vacancies-induced phase transformation is formed. RGO/MnO x composite exhibits a large specific capacitance (274 F g−1 at 0.5 A g−1), excellent cycling stability (98.8% after 5000 cycles at 1 A g−1) and rate performance (171 F g−1 at 10 A g−1). The performance improvement of rGO/MnO x sample is mainly attributed to the moderate concentration of oxygen vacancies, rGO and special 3D porous architecture, which facilitate the rapid ionic and electronic transport and promote a facile redox reaction and surface double-layer capacitance. The asymmetric supercapacitor composed of rGO/MnO x //Kochen Black (KB) also shows an outstanding cyclic stability (89% after 5000 cycles) in all-solid-state asymmetric supercapacitor. The design and synthesis method of rGO/MnO x sample offers a promising approach to broaden MnO 2 -based electrode materials for a new-generation energy storage device. [ABSTRACT FROM AUTHOR]

A facile and effective synthetic method via a thermal-decomposition reduction in air has been employed to synthesize Li 4 Ti 5 O 12 (LTO)/Graphene (RGO) nanocomposites as a promising anode material for high performance lithium-ion batteries. The structural, morphological, and electrochemical characteristics of the as-prepared LTO/RGO nanocomposites have been investigated with X-ray diffraction (XRD), X-ray photoelectric spectroscopy (XPS), scanning electron microscopy (SEM), infrared spectrum (IR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), respectively. It is found that graphite oxide (GO) is reduced at 300 °C in air. LTO/RGO exhibits higher capacity and better cycling performance than LTO. The superior electrochemical performances of the LTO/RGO electrode are attributed to the excellent electronic conductivity and the positive synergistic effect between RGO and LTO nanoparticles. [ABSTRACT FROM AUTHOR]

In this work, octahedral LiMn 2 O 4 (O-LMO) with exposed {111} crystal facets was prepared using MnCO 3 as a precursor via solid phase reactions. O-LMO was revealed to have the superior rate performance and good cycling stability in both a three-electrode system and full aqueous batteries with Li 2 SO 4 solution.The capacity retentions of 87% for 200 cycles at 0.1 A g−1 and 87% for 500 cycles at 1 A g−1 were achieved, in sharp contrast with 56% and 70% for the commercial LMO (C-LMO). Also, O-LMO showed the excellent performance in organic systems as well. The superior performance for both aqueous and organic systems may be related to the maintaining of octahedral structures and surface morphologies for O-LMO cycled 200 times at 0.1 A g−1 in aqueous system and the suppression of Mn dissolution and side reactions in both aqueous and organic systems, which originates from the stable {111} facets. [Display omitted] [ABSTRACT FROM AUTHOR]

Herein, the flower-like manganese oxide was synthesized by a hydrothermal method, and then modified by plasma H 2 for different time to create oxygen vacancies. The longer the treating time, the higher the concentration of oxygen vacancies. Meanwhile, the crystal structure and morphology of MnO 2 material remain the same as the raw material after plasma H 2 treatment. The sample modified by plasma H 2 for 10 min (MnO x -10) exhibited a high specific capacitance of 296.9 F g−1 at 0.5 A g−1 and a superior cycling stability with a capacity retention of 90.0 % after 5000 cycles. Moreover, the asymmetric supercapacitor (ASC) using the as-prepared MnO x -10 as cathode and Kochen Black (KB) as anode was fabricated and showed an outstanding cyclic stability with a capacity retention of 90.0 % after 5000 cycles and a high energy density of 61 Wh kg−1 at a corresponding power density of 750 W kg−1. This study provided a comprehensive understanding of plasma H 2 as an effective technique for introducing oxygen vacancies and further broaden the application of manganese oxide as a kind of high capacity and low cost electrode materials. [ABSTRACT FROM AUTHOR]