The electronic band structures and band gap bowing parameters of In_xGa_(1-x)N are studied by the firstprinciples method based on the density functional theory. Calculations by employing both the Heyd-ScuseriaErnzerh of hybrid functional(HSE06) and the Perdew-Burke-Ernzerhof(PBE) one are performed. We found that the theoretical band gap bowing parameter is dependent significantly on the calculation method, especially on the exchange-correlation functional employed in the DFT calculations. The band gap of In_xGa_(1-x)N alloy decreases considerably when the In constituent x increases. It is the interactions of s–s and p–p orbitals between anions and cations that play significant roles in formatting the band gaps bowing. In general, the HSE06 hybrid functional could provide a good alternative to the PBE functional in calculating the band gap bowing parameters.
A vanadyl phosphate containing a new member of tancoite-like single chain,(DAPH2)[VIVO(HPO4)2]·xH2O(x≈0.2,DAP=1,3-diaminopropane,C3H10N2),has been synthesized under hydro(solvo)thermal conditions.It crystallizes in orthorhombic space group P21212(No.18)with a=7.1730(14),b=19.252(4),c=8.6557(17),Z=4,V=1195.3(4)3,C3H14.38N2P2VO9.19,Mr=338.47,Dc=1.881 g/cm3,μ(MoKα)=1.138 mm–1and F(000)=692.The final full-matrix least-squares refinement converged to R=0.0408,wR=0.1046 for 2498 observed reflections with I>2(I)and R=0.0456 and wR=0.1080 for all data(2750)and S=1.001.Its one-dimensional structure consists of tancoite-like1{VIVO(HPO4)2}2–single chains surrounded by DAPH22+ions and water molecules.The single chain is built from trans-corner-sharing octahedral{VIV=O···VIV}backbone loop-branched by HPO4groups like staple forming a new member of tancoite single chain.Due to the special coordination of VIVO6,the1{VO(HPO4)2–}chain adopts a larger M–O–M angle(V–O–V=135o)than those of tancoite chains reported before.The corner-sharing linear{VIV=O···VIV}chain structure also leads to a one-dimensional weak antiferromagnetic interaction at low temperature.The magnetic measurements confirm the 4+valence state of vanadium.IR and TG results of the title compound are also discussed.
The effects of methylene methanedisulfonate（MMDS） on the high-temperature（50℃） cycle performance of LiMn2O4/graphite cells are investigated.By addition of 2 wt%MMDS into a routine electrolyte,the high-temperature cycling performance of LiMn204/graphite cells can be significantly improved.The analysis of differential capacity curves and energy-dispersive X-ray spectrometry（EDX） indicates that MMDS decomposed on both cathode and anode.The three-electrode system of pouch cell is used to reveal the capacity loss mechanism in the cells.It is shown that the capacity fading of cells without MMDS in the electrolytes is due to irreversible lithium consumption during cycling and irreversible damage of LiMn2O4 material,while the capacity fading of cell with 2 wt%MMDS in electrolytes mainly originated from irreversible lithium consumption during cycling.
首次采用溶胶-凝胶法制备Na2MnSiO4/C纳米复合正极材料.X射线衍射（XRD）和Rietveld结构精修结果表明,合成的Na2MnSiO4材料为单斜晶系、Pn空间群.红外光谱（FTIR）结果证实材料中不含有Na2SiO3和SiO2等杂质.电化学测试结果表明,该材料在1 mol·L-1NaClO4/PC电解液中,电流密度为14 m A·g-1、电压范围为1.5~4.2V（vs.Na＋/Na）测试条件下,其首次可逆放电比容量高达113 m Ah·g-1.
