A first principle method, based on the density functional theory, was used to investigate the average voltage of lithiation/delithiation for Li-ion battery materials across 7 categories and 18 series, including LiMO 2 , LiMn 2 O 4 , LiMPO 4 , Li 2 MSiO 4 and graphite. The average voltage of lithiation/delithiation in the relevant electrode materials was obtained by comparing the total-energy difference, before and after an electrochemical reaction. The calculated values were in good agreement with experimental data. The systematic difference between the simulated and experimental values could be explained in terms of the binding energy on the surface of the lithium electrode. This type of calculation method could be applied as an easy and effective tool for predicting the potential performance of new lithiation/delithiation materials.
A series of Ba_8Ga_(16)Si_(30) clathrate samples were prepared by arc melting,ball milling,acid washing,and spark plasma sintering(SPS).X-ray diffraction analysis revealed that the lattice of the Ba_8Ga_(16)Si_(30) samples expanded as the SPS temperature was increased from400 to 750℃.Lattice contraction recurred when the SPS temperature was further increased in the range of 750-1000℃.This phenomenon can be explained by the variation of Ga content in the lattice.The thermoelectric figure of the merit ZT value of clathrates increased with the increase in SPS temperature and reached a maximum when the sample was subjected to SPS at 800℃.A further increase in SPS temperature did not contribute to the improvement of ZT.The variation of the lattice parameter a vs.SPS temperature T was similar to the variation observed in the ZT-T curve.
Li-hua LiuFeng LiNing ChenHong-mei QiuGuo-hui CaoYang Li
