Li-rich layered transitional metal oxide Li1.2(Mn0.54Ni0.16Co0.08)O2 was prepared by sol-gel method and further modified by AlF3 coating via a wet process. The bare and AlF3-coated Li1.2(Mn0.54Ni0.16Co0.08)O2 samples were characterized by X-ray diffraction(XRD), scanning electron microscope(SEM), and high resolution transmission electron microscope(HRTEM). XRD results show that the bare and AlF3-coated samples have typical hexagonal α-Na Fe O2 structure, and AlF3-coated layer does not affect the crystal structure of the bare Li1.2(Mn0.54Ni0.16Co0.08)O2. Morphology measurements present that the AlF3 layer with a thickness of 5-7 nm is coated on the surface of the Li1.2(Mn0.54Ni0.16Co0.08)O2 particles.Galvanostatic charge-discharge tests at various rates show that the AlF3-coated Li1.2(Mn0.54Ni0.16Co0.08)O2 has an enhanced electrochemical performance compared with the bare sample. At 1C rate, it delivers an initial discharge capacity of 208.2 m A·h/g and a capacity retention of 72.4% after 50 cycles, while those of the bare Li1.2(Mn0.54Ni0.16Co0.08)O2 are 191.7 m A·h/g and 51.6 %, respectively.
Anodic electrodes with the mixture of hydrogen storage alloys and different contents of Co3O4(2%,4%,6% and 8%,mass fraction) powders were made.The effects of Co3O4 on the electrochemical performance of the alloy electrodes were studied.The constant charge-discharge tests show that the discharge capacity of alloy electrodes with Co3O4 significantly increases,and the maximum discharge capacities of electrodes with 2%,4%,6% and 8% Co3O4 are higher than the electrode with no Co3O4 by 0.83%,4.86%,7.18% and 9.21%,accordingly.Linear polarization(LP) and electrochemical impedance spectroscopy(EIS) tests suggest that charge-transfer resistance decreases by the addition of Co3O4.Cyclic voltammogram(CV),scanning electron microscopy(SEM) and energy dispersive spectrum(EDS) tests indicate that Co3O4 can partly dissolve and experience a reversible oxidation-reduction process of Co to Co(OH)2,leading to the improvement in the electrochemical performance of hydrogen storage alloy.
Nanostructured MnO2/CNT composite was synthesized by a soft template approach in the presence of Pluronic P123 surfactant. The product was characterized by X-ray diffraction, thermogravimetric and differential thermal analyses, Fourier transformed infrared spectroscopy and high-resolution transmission electron microscopy. The results show that the sample consists of poor crystalline α-MnO2 nanorods with a diameter of about 10 nm and a length of 30-50 nm, which absorb on the carbon nanotubes. The electrochemical properties of the product as cathode material for Li-MnO2 cell are evaluated by galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS). Compared with pure MnO2 electrode, the MnO2/CNT composite delivers a much larger initial capacity of 275.3 mA-h/g and better rate and cycling performance.