LixMn2OyFz中锰的平均化合价的测定

以LiNO3、LiF和Mn(AC)2·4H2O为原料、采用柠檬酸络合法制备系列LixMn2OyFz电极材料。然后对每一试样取样3份,用已知浓度的草酸溶液溶解,应用高锰酸钾返滴定法测试试样得失电子数,而后在加入盐酸羟胺的条件下,不经离子分离直接用EDTA溶液滴定Mn2+,经数学计算可求出LixMn2OyFz试样中锰的平均价态。采用向标准的Mn2+溶液中加入LiF、K2SO4、(NH4)2SO4的方法分析了K+、NH4+、SO42-、F-对Mn2+滴定测试结果的影响。结果表明,物质的量是Mn2+的50～100倍的上述离子均不干扰Mn2+的测试结果,因此,做完氧化还原滴定的溶液可以不进行对上述离子分离直接进行对Mn2+的配位滴定。还利用锰的平均价态的测试结果分析了掺杂物质与锰的平均化合价的关系。

Determination of the Mean Valence of Mn in LixMn2OyFz

Using LiNO_3, LiF and Mn(AC)_2·H_2O as starting materials, a series of spinel Li_xMn_2O_yF_z were prepared by citric acid complex method. Every material was qualified and titrated three times. Firstly, the material was used to do redox titration and the total electron number transferred in oxidation-reduction was determined by the standard oxalic acid titrimetric method. Secondly, using NH_2OH·HCl as reducing agent, the solution was used to determine the total manganese by EDTA titration. And finally, the mean valence of manganese was calculated by the above two results determined. The influence of K~+, NH~(4+), SO_4~(2-) and F~- on the determination of Mn~(2+) was investigated by adding LiF, K_2SO_4 and (NH_4)_2SO_4 into the Mn~(2+) solution, and the result shows that these ions have no effect on the determination of Mn~(2+) even the ratio of these ions to Mn~(2+) is between 50 to 100 , thus the determination of Mn~(2+) can be performed without ion separation. The relation of the mean valence of manganese and the doping is investigated by analyzing the results of the experimental.