| 1. Li1.2Mn0.54Ni0.13Co0.13O2/C wire-like composite cathode material was prepared by ex-situ electrospinning method. At 0.2 C, although both of the wire-like composite material and pristine material have similar discharge capacity, the composite could still display 222 m Ah·g-1 with a capacity retention of 86.2% after 50 cycles, as well as maintain a discharge capacity of 176.7 m Ah·g-1 with 80.5% capacity retention after100 cycles at 250 m A·g-1, which exhibited a better cycling stability due to the amorphous carbon layer to prevent the Mn4+ dissolution. The EIS tests demonstrated that the wire-like composite could decrease the electronic transfer resistance during the electrochemical reaction due to the improved surface conductivity and more transport channels provided by the network structure.2. Tube-like Li1.2Mn0.54Ni0.13Co0.13O2 materials were synthesized by in-situ electrospinning method. The experimental results were showed below: 1. Sample synthesized at 850 ? has the lower cation mixing degree and better cyclic reversibility. 2. Sample synthesized for 7 h has the better cyclic performance. 3.Different sizes of the tube-like samples could be prepared with a precursor concentration of 5 or 10 mmol, while the bead-like structure corresponds to the precursor concentration of 13 mmol. The electrochemical tests demonstrated that the tube-like samples have higher discharge capacity than the bead-like sample, especially the 10 mmol sample, which displayed a discharge capacity of 193 m Ah·g-1 to 171.5m Ah·g-1 after 100 cycles at 250 m A·g-1.3. Different proportions of tube-like Li-rich/graphene composite cathode materials were prepared by physical mixing method. The experimental result showed that the composite displayed a better cycling stability with a mass propotion of 1:20,which maintained a higher capacity of 194.2 m Ah·g-1than the pristine sample of145.5 m Ah·g-1 after 100 cycles at 250 m A·g-1. Such improved performance should be benefited from the loading of graphene nanosheets, which not only protected theactive material to overexposure with electrolyte, but also accelerated the electronic/ionic transfer rate and buffered the polarization effect.4. Fiberous and particle LiFePO4/C composites were respectively synthesized by electrospinning and sol-gel methods. Both of the samples belonged to the olivine structure. At 0.2 C, the discharge capacity of particle and fiberous composite were respectively decreased from 135.9 m Ah·g-1 and 137 m Ah·g-1 to 129 m Ah·g-1 and134.1 m Ah·g-1 after 100 cycles. In addition, the electrochemical impedance test showed that the fiberous composite have lower electronic transfer resistance than the particle composite. Such better performance was benefited from the network structure formated from the fibers, which shorten and accelerated the electronic/ionic pathway,buffering the polarization effect. |
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