【摘要】 用EXAFS和XANES技术研究了高温固相反应法合成尖晶石结构的LiMn2 O4 中Mn原子的局域结构受到焙烧温度的影响 .XANES结果表明 ,B1 峰和B2 峰强度分别与Mn3+ ,Mn4 + 的含量高低相关 ,焙烧温度愈高 ,B1 峰的强度愈大 .EXAFS给出的结构参数结果进一步表明 ,LiMn2 O4 (6 73K)的Mn -O第一配位和Mn Mn第二配位的无序度σ1(0 .0 0 5 9nm)和σ2 (0 .0 0 92nm)分别小于及大于LiMn2 O4 (973K)的σ1 (0 .0 0 6 6nm)和σ2 (0 .0 0 81nm) ,LiMn2 O4 (10 73K)的σ1 (0 .0 0 6 4nm)和σ2 (0 .0 0 79nm) ,说明低温焙烧的LiMn2 O4 (6 73K)样品中Mn原子的局域配位环境结构与高温焙烧的LiMn2 O4 (973K)和LiMn2 O4 (10 73K)的相比有较大差异 ,前者为LiMn2 O4 和Li2 MnO3(或Li4 Mn5O1 2 )两种混合物相 ,后者为正尖晶石结构的LiMn2 O4 单一物相更多还原

【Abstract】 The local structures of spinel lithium manganese oxides prepared by means of high temperature solid phase reaction, were investigated by extended x ray absorption fine structure (EXAFS) and x ray absorption near edge structure (XANES) techniques. The XANES results indicated that the intensities of B 1 and B 2 peaks were related to the contents of Mn 3+ and Mn 4+ , respectively. Furthermore, the EXAFS results showed that the Debye Waller factor σ (0.0059nm) of the first shell of Mn-O coordination in LiMn 2O 4 (673 K) is smaller than those in LiMn 2O 4 (973 K) ( σ 1=0.0066nm) and LiMn 2O 4 (1073 K)( σ 1=0 0064nm). In contrast, the σ 2 (0 0092nm) of the second shell of Mn-Mn coordination in LiMn 2O 4 (673 K) is larger than these in LiMn 2O 4 (973 K) ( σ 2=0.0081nm)and LiMn 2O 4 (1073 K)( σ 2=0.0079nm). It suggests that there is a large difference in the local structures around Mn atoms between LiMn 2O 4 (673 K) and both of LiMn 2O 4 (973 K) and LiMn 2O 4 (1073 K). We proposed that LiMn 2O 4 (673 K) is a mixture of LiMn 2O 4 and Li 2MnO 3 (or Li 4Mn 5O 12 ), and LiMn 2O 4 or LiMn 2O 4 (1073 K) is spinel LiMn 2O 4.更多还原