C-rate and temperature dependence of electrochemical performance of Li[Co0.1Ni0.15Li0.2Mn0.55]O2 cathode materials before and after Co3(PO4)2 coating

Li[Co_0.1Ni_0.15Li_0.2Mn_0.55]O₂ was synthesized, as a cathode material with high capacity, by a simple combustion method followed by annealing at 800?°C. Li[Co_0.1Ni_0.15Li_0.2Mn_0.55]O₂ cathode materials were coated with lithium-active Co₃(PO₄)₂ to improve the electrochemical performance of rechargeable lithium batteries. Morphologies and physical properties of Li[Co_0.1Ni_0.15Li_0.2Mn_0.55]O₂ before and after the Co₃(PO₄)₂ coating were analyzed with a scanning electron microscope equipped with an energy dispersive X-ray spectroscope. Transmission electron microscopy, powder X-ray diffraction, and Brunauer?CEmmett?CTeller surface area analyses were also carried out. The electrochemical performances of Li[Co_0.1Ni_0.15Li_0.2Mn_0.55]O₂ cathode material before and after Co₃(PO₄)₂ coating were evaluated by galvanostatic charge?Cdischarge testing at different charge and discharge densities. The temperature dependence of the cathode material before and after Co₃(PO₄)₂ coating was investigated at 0, 10, 20, 30, 40, and 50?°C at a rate of 0.1?C. Co₃(PO₄)₂-Li[Co_0.1Ni_0.15Li_0.2Mn_0.55]O₂ exhibited good electrochemical performance under high C-rate and experimental temperature conditions. The enhanced electrochemical performances were attributed to the formation of a lithium-active Co₃(PO₄)₂-coating layer on Li[Co_0.1Ni_0.15Li_0.2Mn_0.55]O₂.     

Fabrication and performance of nanoporous TiO2/SnO2 electrodes with a half hollow sphere structure for dye sensitized solar cells

The incorporation of nano-crystalline semiconductors with novel kinds of ordered microstructure is a very important area of research in the field of dye sensitized solar cells. A sol–gel method involving hydrolysis of titanium isopropoxide was used to form TiO₂ nanoparticles on the surface of SiO₂ spheres. In this process, 1, 5, or 10 wt% of SnCl₂.2H₂O was added to the sol–gel solution. To prepare TiO₂/SnO₂ nanoparticles with a half hollow sphere structure, SiO₂ was removed with NaOH solution. The crystal phase, crystal shape, and surface properties of the metal oxide nanocrystals were studied by x-ray diffraction and scanning electron microscopy. The photovoltaic performance of the TiO₂/SnO₂ nanoparticles with half hollow sphere structures was measured. The dye sensitized solar cell using nanoporous TiO₂ as electrode materials exhibits an overall conversion efficiency of 7.36% with a light intensity of 100 mW/cm². The short circuit photocurrent (I_sc), open circuit photovoltage (V_oc), and conversion efficiency (η) of these solar cells were improved over conventional materials.