Preparation and electrochemical performance of Li_2Mn_(0.5)Fe_(0.5)SiO_4 cathode material with sol-gel method for lithium ion batteries

Li2Fe0.5Mn0.5SiO4 material was synthesized by a citric acid-assisted sol-gel method. The influence of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+) on the electrochemical properties of Li2Fe0.5Mn0.5SiO4 was studied. The final sample was identified as Li2Fe0.5Mn0.5SiO4 with a Pmn21 monoclinic structure by X-ray diffraction analysis. The crystal phases components and crystal phase structure of the Li2Fe0.5Mn0.4SiO4 material were improved as the increase of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+). Field-emission scanning electron microscopy verified that the Li2Fe0.5Mn0.5SiO4 particles are agglomerates of Li2Fe0.5Mn0.5SiO4 primary particles with a geometric mean diameter of 220 nm. The Li2Fe0.5Mn0.5SiO4 sample was used as an electrode material for rechargeable lithium ion batteries, and the electrochemical measurements were carried out at room temperature. The Li2Fe0.5Mn0.5SiO4 electrode delivered a first discharge capacity of 230.1 mAh/g at the current density of 10 mA/g in first cycle and about 162 mAh/g after 20 cycles at the current density of 20 mA/g.

Al^(3+)掺杂立方相Li_7La_3Zr_2O_(12)的制备及性能表征

采用一种柠檬酸辅助聚合的溶胶-凝胶法制备了掺杂2%(摩尔分数)Al3+的立方相结构的Li7La3Zr2O12固体电解质,同时,采用高温固相法尝试合成不掺杂Al3+的Li7La3Zr2O12作为对比。分析结果表明:热处理温度超过1 000℃时Li7La3Zr2O12易发生分解;而掺杂2%(摩尔分数)Al3+的Li7La3Zr2O12能在900℃时保持稳定立方相结构,在1 000℃下烧结6 h后得到高致密度的烧结体。该法制备的Li7La3Zr2O12样品表现出高离子电导率:298 K时为4.5×10-5 S/cm,523K时达到3.6×10-3 S/cm。Li+迁移活化能大约为25.1 k J/mol。上述结果表明,作为全固态电池电解质,Al3+掺杂的Li7La3Zr2O12有较好的应用前景。