Papers by Author: Rong Yang

Abstract: LiFePO4/C is synthesized via sol-gel method using Fe3+ as iron sources and complexing agents, followed by sintering at high temperature for crystallization. The amount of carbon in these composites is less than 6.8 wt.% and the XRD experiment confirms that all samples are pure single phase indexed with orthorhombic Pnma space group. The particle size of the LiFePO4/C synthesized by acetic acid as complexing agent is drastically fine with 200nm. The electrochemical performance of this material, including reversible capacity, cycle number and charge-discharge characteristics, exhibits better.

Abstract: To have a fundamental understanding on the principle of carbon aerogels when it is used as electrode materials in power battery, the effects of density and structural properties on the electrical conductivity of carbon aerogels was investigated in this paper. Carbon aerogels with different density were prepared via adjusting the chemical conditions of the primary solution. The morphology of carbon aerogels were observed by field emission scanning electron microscopy (FE-SEM). Experimental results show that the electrical conductivity of carbon aerogels is ranged from 10-6 Ω/cm to 10 Ω/cm, and that not only the density but also the carbon particle size and porosity of carbon aerogels effect the transport property greatly. With the increasing of the density the electrical conductivity of carbon aerogels increases. This indicates that larger particle size and lower porosity of the nano-structure lead to higher conductivity.

Abstract: Li2MSiO4(M=Mn, Co, Ni) is a potential high capacity cathode material because of its outstanding properties that exchange of two electrons per transition metal atom is possible and the theoretical capacity of Li2MSiO4 can reach as high as 330 mAhg-1. In this family, the cathode performance of Li2MnSiO4 synthesized by solution route has been published recently. However, it seems that the cycle life of Li2MnSiO4 fell short of our expectation. In this work, the Li2Mn0.7Fe0.3SiO4 cathode material was synthesized by traditional solid-state reaction method. The prepared powder was consisted of majority of Li2Mn0.7Fe0.3SiO4 and minor impurities which were examined by XRD. FESEM morphology showed that the products of Li2Mn0.7Fe0.3SiO4 and Li2MnSiO4 have similar particle size (about 50-300 nm). The electrochemical performance of Li2Mn0.7Fe0.3SiO4, especially for reversible capacity and cycle life, exhibited better than those of Li2MnSiO4.

Abstract: In this paper, homogeneous and well-crystallized LiFePO4 was synthesized by a novel modified solid-state reaction method following by heat treatment at relatively low temperature of 500°C in Ar. No impurities are detected in the XRD patterns. The initial charge specific capacity and discharge specific capacity reach 157.2mAhg-1 and 152.6mAhg-1 respectively at 20°C. Voltage plateaus at around 3.45V were observed in all the curves, indicating that the charge and discharge reaction proceeds as a two-phase reaction. The initial charge specific capacity is 157.2mAhg-1 at 0.1C rate, i.e. 92% of the theoretical capacity, and specific capacity decreases slightly after 100 circles at room temperature.