液相燃烧合成LiMn_2O_4及其Mn平均价态的测定

以硝酸锂(锰)、醋酸锂(锰)、尿素和柠檬酸为原料,利用液相燃烧合成方法研究了两种不同酸根盐体系以及燃料尿素用量和柠檬酸对燃烧合成尖晶石型LiMn2O4的影响,并用氧化还原滴定法测定产物中Mn的平均化合价作为合成产物为LiMn2O4的辅证依据。XRD分析表明,液相燃烧合成可制备得尖晶石型LiMn2O4物质,锂和锰的醋酸盐体系燃烧合成LiMn2O4比硝酸盐体系好,燃料尿素比柠檬酸好;醋酸盐和尿素的燃烧体系可得纯相LiMn2O4产物,硝酸盐和尿素的燃烧体系中含有较多Mn2O3,但随尿素量增多,杂相Mn2O3的含量减少;产物LiMn2O4中Mn的价态为+3.5左右,与LiMn2O4中Mn的标准价态相同。

Solution Combustion Synthesis of LiMn2O4 Powder and Determination of Manganese Average Valence State in LiMn2O4

Spinel LiMn2O4 powders were prepared by solution combustion synthesis using LiNO3,Mn(NO3)2 or LiAc and Mn(Ac)2 as raw materials and urea or citric acid as fuel.The effect of nitrates or acetates as raw materials and the dosage of urea and citric acid on the preparation of LiMn2O4 were studied.In addition,the average valence states of manganese in the as-prepared products were determined by means of redox titration method.XRD analysis indicated that spinel LiMn2O4 could be prepared by solution combustion synthesis,and acetates as raw materials were better for the formation of the LiMn2O4 than that of nitrates,and as fuel,urea was better than citric acid.Pure LiMn2O4 could be prepared in acetate-urea system.In nitrate-urea system,impurity phase,Mn2O3 appeared in the products,but decreased with the increment of urea.The average valence states of manganese in the asprepared products were about 3.5,which were approximate to the standard valence states in LiMn2O4.