【作者】 曾跃武； 屠小燕； 吕光烈；

【Author】 ZENG Yue-wu, TU Xiao-yan, LU Guang-lie (Center of Analysis and Measurement, Zhejiang University, Hangzhou 310028, China)

【机构】 浙江大学测试中心；

【摘要】 在200℃水热条件下,采用Mn2O3、Cr2O3和LiOH·H2O合成了正交层状结构锰酸锂;以0.5 C与1 C 倍率放电时其比容量可达150 mA·h/g和135 mA·h/g,50次循环后的容量衰减量约5%。透射电镜和X射线衍射分析表明:未充放电前.这种层状结构的LiMnO2是由25 nm左右的小晶粒堆叠成的大团聚体;电化学循环后, 正交层状结构转为成均有电化学活性的晶粒尺寸6 nm的类尖晶石型与20 nm的氯化纳型结构,晶体结构中8 a 位、16 d位和4 a位均由Li和Mn共位,其摩尔比分别为0.91:0.09,O.1:0.9和0.5:0.5。当充放电倍率从0.2C增大到1 C时,氯化纳型丰度在18%-42%之间变化变化;在2.0-4.5 V电化学循环过程中,未出现除这两种晶型外的其它晶型;纳米晶团聚的显微结构和Li、Mn在类尖晶石型和氯化纳型结构中的占位无序,有效地抑制了活性材料在电化学循环过程的姜泰勒畸变效应和电解质对材料的腐蚀,使其呈现良好的电化学性能。更多还原

【Abstract】 Orthohombic layered lithium manganese oxide were prepared by hydrothermal method using Mn2O3, Cr2O3 and LiOH## H2O at 200 ℃ , the maximum discharge capacity of which can reach 150 mA·h/g and 130 mA·h/g at 0. 5 C and 1 C rate, respectively,with a capacity retention rate of about 5% after 50 cycles. The analysis by X-ray diffraction and transmission electron microscopy shows that the structure of pre-cycled layered lithium manganese oxide can be observed as large particles agglomerated with 25 nm primary crystallites. After several cycles, the crystal structure has changed from layer lithium manganese oxide to 6 nm spinel-type Li0.91 [Mn(Cr)]0.09-[Mn(Cr)]1.84-Li0.16O4 and 20 nm sodium chloride-type Li0.5[Mn(Cr)]0.5O, both of which are electrochemically active materials. In the structure of them, 8 a site, 16 d site and 4 a site are all occupied by atoms of Li and Mn with mole ratios of 0. 91 : 0. 09, 0. 1: 0. 9 and 0. 5 : 0. 5. With the increasing charge and discharge current density from 0. 2 C to 1 C, the abundance of the sodium chloride-type phase increases from 18% to 42%. During electrochemical cycling with a cutoff voltage of 2. 0 - 4. 5 V, there is no other phase formed. The microstructure agglomerated by nano-domain crystals and the disorder occupying site of Li and Mn atoms in spinel-type and sodium chloride-type structure effectively suppress the Jahn-Teller distortion of active materials during electrolyte, and keep active materials having better electrochemical properties.更多还原