摘要：
MoS2 with a 2D layered structure and high theoretical capacity has been regarded as a promising candidate for anode materials in lithium ion batteries. But its poor cyclic stability and low rate capability hinder its practical applications. Herein, hierarchical MoS2 nanotori consisting of MoS2 nanosheets with an increased interlayer distance were synthesized by a facile hydrothermal reaction for the first time. A possible formation mechanism of the hierarchical MoS2 nanotori is proposed based on the scanning electronic microscopy (SEM) results and the influence of the MoO3 precursor on the morphology of the MoS2 obtained. The hierarchical MoS2 nanotori display superior reversible capacity, good rate capability and improved cyclic performance, which can be attributed to their hierarchical surface, hollow structure feature and increased layer distance. The formation mechanism of hierarchical MoS2 nanotori proposed here should offer a new technique for the design and synthesis of MoS2 with different morphologies using MoO3 as the growth template.
关键词：
Aqueous electrolyte;Asymmetric supercapacitor;Electrochemical performance;Hollow LiMn 2 O 4 microspheres;Porous LiMn 2 O 4 microspheres
摘要：
Asymmetric supercapacitors (ASCS) with a battery-type electrode and a capacitor-type electrode have been regarded as the most promising energy-storage devices with high-energy and high-power densities. In this paper, the porous and hollow LiMn2O4 microspheres were prepared using MnCO3 microspheres as template and subsequently an ASCS with the as-prepared LiMn2O4 as cathode and activated carbon (AC) as anode in Li2SO4 aqueous electrolyte (designated by AC//LiMn2O4 ASCS) was assembled and investigated electrochemically. The results indicate that the porous LiMn2O4 exhibits a higher reversible capacity and rate capability compared to hollow LiMn2O4 microspheres, and delivers a specific capacitance of 536 F g(-1) at 1 mV s(-1). The assembled AC//porous LiMn2O4 ASCS presents a high energy density of 33.12 Wh kg(-1) at the power density of 90 W kg(-1). All these might be attributed to the unique microstructure of the as-prepared porous LiMn2O4 microspheres. (c) 2017 Elsevier B.V. All rights reserved.
摘要：
A facile sol-gel/emulsion approach was employed for the fabrication of mesoporous silica nanoparticles with a large BET specific surface area of 1594 m(2) g(-1). The as-prepared SiO2 electrode delivers a highly stable specific capacity of as large as 1060 mA h g(-1) at a current density of 100 mA g(-1) after 90 cycles, exhibiting a good cycling stability.
摘要：
The hollow Co9S8 nanospheres with ca. 50 nm were elaborately fabricated by a facile solvothermal method and characterized by powder X-ray diffraction (XRD), Scanning electron microscopy (SEM) and BET measurement to result in a specific surface area of 226 m(2) g(-1). The prepared hollow Co9S8 nanosphere electrode delivers a initial specific capacitance of 234.7 F g(-1) at a current density of 0.5 A g(-1), which can be retained up to the 60th cycle, indicating the good cycleability and excellent rate capability. As a consequence, the energy density of the prepared Co9S8 pseudocapacitor could reach up to 17.96 Wh kg(-1) at a power density of 32.82 W kg(-1), which is much more than those of common electric double capacitors, exhibiting the pseudocapacitive characteristic. This might be due to the unique hollow Co9S8 nanosphere structure to shorten the path of the electron transportation and the ionic diffusion.
摘要：
The nanosized spinel alpha-LiFe5O8 with a grain size of about 10 nm was fabricated by a facile solid state method via the assistance of oxalic acid. The as-prepared alpha-LiFe5O8 electrode for lithium ion battery delivers a high reversible initial specific capacity of 257.1 mA h g(-1) at 28 mA g(-1) and remaining at 130 mAh g(-1) at as high as 2820 mA g(-1) even after 100 cycles, as well as excellent rate capability and improved cycling stability, which has not reported before for lithium ferrite oxides. This might be attributed to the characteristic pseudocapacitive behavior of lithium storage in nanosized spinel alpha-LiFe5O8 and the structural stability of alpha-LiFe5O8 upon charge/discharge as well, as evidenced by CV measurement for the as-prepared alpha-LiFe5O8 electrode. The unique combination of those features for lithium ion battery and capacitor is potential to develop high performance hybrid energy storage device for the needs of electric vehicle batteries and other high powder applications.
摘要：
Polyvinyl pyrrolidone (PVP) as dispersant was employed to assist the hydrothermal synthesis of MoS2. The results show that the interlayer distance of the as-obtained MoS2 is smaller compared with the original MoS2 without PVP-assistance using XRD, SEM and TEM techniques for characterization. Investigations of the electrochemical performances of MoS2 with different interlayer distance as anode material for LIBs demonstrate that the specific capacity and the cycling performance of lithium storage of MoS2 is significantly dependent on the interlayer distance of MoS2, furthermore causing the different mechanism of lithium storage. This might be attributed to the varied internal resistance and Li-ion diffusion in layered MoS2 due to the different interlayer distance, which is validated from electrochemical impedance spectroscope of MoS2 electrode.
摘要：
The hierarchical nanostructured FeS2 hollow microspheres composed of nanoflakes were fabricated based on Ostwald ripening using sulfur powder as sulfur source and triethanolamine as both solvent and reducing agent, and electrochemically investigated as cathode material for lithium-ion batteries. The as-obtained FeS2 electrode delivered an initial capacity of 886.3 mA h g−1 at 0.1 C at ambient temperature, which is one of the highest values in the reported results. In the subsequent cycles following the first cycle, the electrode exhibited good reversibility at ambient temperature, resulting in good cycling stability and performance, and the discharge capacity of 392.7 mA h g−1 at 1 C was still retained after 30 cycles. This might be attributed to the unique FeS2 structure with hierarchical nanostructured hollow microspheres, showing potential to develop FeS2 cathode materials with high energy density for lithium-ion batteries.
摘要：
A facile process was developed to synthesize MoS2 nanospheres by a simple PVP assisted hydrothermal method. The samples were characterized by XRD, SEM and Electrochemical tests. SEM demonstrates that the obtained MoS2 has sphere-like morphology in the presence of surfactant PVP. Electrochemical measurements show that the initial discharge capacity of the MoS2 nanospheres is 1915.1, 895.8 and 761.6 mAh g-1 at current densities of 100, 400 and 800 mA g-1, respectively. Meanwhile, it is found that the MoS2 nanospheres have improved rate capacity and cycle stability.
关键词：
alpha-LiFeO2;Electrochemical performance;Lithium-ion batteries;Solid state method
摘要：
In this work, nanosized alpha-LiFeO2 were synthesized by a simple low-temperature solid state method. The obtained alpha-LiFeO2 nanoparticles were investigated by the measurements of X-ray diffraction pattern, scanning electronic microscopy, transmission electron microscope and electrochemical performance. Electrochemical measurements showed that the initial discharge capacity was 277.9, 188.4, and 158.2 mAh g(-1) at 0.1 C, 1 C, and 2 C, respectively. Meanwhile, the alpha-LiFeO2 nanoparticles exhibited improved cycle stability (123 mAh g(-1) at 2 C after 60 cycles). The high capacity, improved rate performance and cycle stability can be attributed to the smaller particle sizes, which can facilitate the contact between active materials and the electrolyte, enhance lithium and electron transport during cycling.
