Functionalized nano-SiO2 for improving the cycling stability of 4.6V high voltage LiCoO2 cathodes

Abstract

In order to elevate the high voltage resistance and stability of LiCoO2 cathodes, its application potentialis further excavated. In this paper, the functionalization of nano SiO2(PDA@SiO2) was realized by using the self polymerization coating characteristics of dopamine. Its functionalization with the fumed SiO2 nano-particle center allows even 2% PDA@SiO2 to be uniformly coated onto a LiCoO2 cathode via rotary steaming. It is demonstrated by scanning electron microscope (SEM) and X-ray energy dispersive spectroscopy (EDS) that the functional nano-coating is distributed homogeneously on the surface of LiCoO2 particles. The close interaction between nano PDA@SiO2 coating and LiCoO2 particles is emerged, which avoids the agglomeration of nano SiO2 and enhances the function of solid superacid formed by fumed SiO2. The X-ray photoelectron spectroscopy (XPS) shows that less undesired side products are deposited on the surface of LiCoO2, and X-ray diffraction (XRD) and SEM indicate that the lattice expansion and irreversible phase transformation of crystal structure are effectively inhibited. The interface stability and ionic conductivity of LiCoO2 cathodes at high voltage are elevated substantially. Thus, the cycle stability of LiCoO2 cathodes during charge and discharge at 4.6 V high voltage is significantly improved. At room temperature, the modified LiCoO2 cathode with functionalized nano-SiO2 achieved a reversible capacity of around 190 mAh g−1 with the capacity retention of 78% after 200 cycles at 1C, along with a relatively high cyclability of 68% capacity retention after 100 cycles at 1C and 50°C.