Yifu Yang

Electrochemical reduction of oxygen on small palladium particles supported on carbon in alkaline solution

The electrocatalytic behaviour of highly dispersed Pd/carbon catalyst prepared by ion pre-adsorption method for oxygen reduction in alkaline solution was investigated with soft-embedded rotating disk electrode and soft-embedded microelectrode method. The results showed that this catalyst has high catalytic activity both for oxygen and for HO2− reduction in alkaline solution. The occurrence of the peak current on the polarization curves of oxygen reduction on the catalyst when potential was scanned negatively, and the occurrence of the negative slope of IDNIR vs. ω−12 relation were analyzed. It is proved that the competition of Pd and support surface for oxygen molecules during oxygen reduction was the main cause for this new phenomenon.

A study on capacity and power fading characteristics of Li(Ni1/3Co1/3Mn1/3)O2-based lithium-ion batteries

The objective of this study is to find out the factor that accounts for the capacity fading and to predict the cycle life of lithium-ion batteries by the driving cycle test. A new method, incremental polarization resistance, is elected to analyze the gradation mechanism based on incremental capacity analysis. It is summarized that the two major factors, the loss of lithium ions and the cathode fading, make the capacity loss in different stages. In the first stage, the loss of lithium ions, caused by the solid electrolyte interface (SEI) lay reaction, is the main reason for battery degradation. In the second stage, the cathode starts to decay and make the capacity loss, because of the less intercalation in cathode. In the third stage, the cathode degradation gradually outpaces the loss of Li and becomes the limit factor for the battery recession. Finally, a cycle life model was established to predict the capacity loss with cycle numbers.