摘要
以Na2CO3、(CH3CO2)2Mn.4H2O、Y2O3和CH3COOLi.2H2O为原料,采用高温固相法经过2次灼烧和水热离子交换法得到一系列钇掺杂的LiMn1-xYxO2(x:0.01,0.02,0.03,0.05)化合物。通过XRD、XPS、循环伏安及恒电流充放电测试技术,研究了钇掺杂离子对合成正极材料结构及电化学性能的影响。结果表明,所得产物均具有单斜层状结构。合适的钇掺杂可以起到扩展锂离子脱嵌通道和稳定骨架结构的作用,钇离子的引入部分取代原有的三价锰离子,由于钇离子的离子半径较三价锰离子大,因此稀土掺杂锰酸锂材料的晶胞参数比未掺杂材料大,在一定程度上扩充了锂离子迁移的三维通道,更有利于锂离子的嵌入与脱嵌,提高单斜层状LiMnO2材料的电化学循环可逆性及循环稳定性。通过对所得化合物进行了钇掺杂量及电化学性能的研究,得到性能比较优良的LiY0.021Mn0.979O2化合物,其首次放电比容量为125.7mA.h/g,100次循环以后,放电比容量达212.1mA.h/g,远高于未掺杂材料的放电容量138mA.h/g。交流阻抗测试结果表明,Y3+的掺入能降低材料的电化学反应阻抗和提高材料中Li+的扩散能力。
A series of yttrium （ Ⅲ ） ion doped layered lithium manganese oxides LiYx Mn1-x O2 （ x ： 0. 01, 0. 02, 0. 03 and 0. 05） compounds was synthesized with Na2CO3, （CH3COO） 2Mn.4H/O, CH3COOLi·2H2O and Y2O3 as the starting materials by means of two-step high temperautre solid state reaction and hydrothermal ion exchange method. The y3 ＋-doping effect on the structure and the electrochemical performances of the samples were investigated by XRD, XPS, cyclic vohammetry and charge-discharge tests. The XRD results show that the samples exhibit the same phase as pure monoclinic layered sturcture. Electrochemical performances indicate that the yttrium ions can partially replace Mn3＋ in monoclinic structure LiMnO2 materials. Because the radius of y3 ＋ is bigger than that of Mn3＋ , samples doped with yittrium elements have larger lattice constant compared with that of undoped sample. Doping enables lithium ions to transport more freely in the three dimensional pathway, and all yittrium element doped materials show good cycle stability. Experiments of doping ratio and electrochemistry performance were carried out. The compound LiY0.021Mn0.979 02 obtained exhibited a better performance whose initial discharge specific capacity reached 123.4 mA-h/g respectivelY. After 100 cycles, the discharge capacity maintained 212. 1 mA.h/g, which is much higher than the discharge capacity 138 mA.h/g of the undoped monoclinic structure LiMnO2 materials. AC analysis shows lower electrochemical impedance and the diffusibility of lithium ions is clearly improved due to y3 ＋ doping. Keywords monoclinic LiMnO2 ,lithium-ion battery, cathode material, yttrium doping, electrochemical property
出处
《应用化学》
CAS
CSCD
北大核心
2010年第2期220-226,共7页
Chinese Journal of Applied Chemistry
基金
新疆师范大学博士后科研资助基金项目(XJNU0807)
关键词
单斜LiMnO2
锂离子电池
正极材料
钇掺杂
电化学性能
monoclinic LiMn02, lithium-ion battery, cathode material, yttrium doping, electrochemical property
作者简介
通讯联系人：粟智，男，博士，教授；E-mail：suzhixj@sina．com；研究方向：无机功能材料
