Effects Of Heat Treatment And Doping On Performance Of LiNi_0.5Mn_1.5O₄Prepared At Low Temperature

The spinel material of LiNi0.5Mn1.5O4is a promising cathode material for lithium-ion batteries due to remarkably property of high charge/discharge voltage plateau around4.7V. In this study, LiNi0.5Mn1.5O4has been prepared by solid-state high temperature ball milling and sol-gel high temperature ball milling. The effects of heat treatment time, Ni-doped and Mg-doped on performances of spinel LiNi0.5Mn1.5O4have been investigated by XRD, SEM and electrochemical testing, respectively. The results are summarized as following.The crystalline structure, discharge capacity and rate cycle performance of LiNi0.5Mn1.5O4prepared by solid state high temperature ball milling are improved with the increasing of heat treatment time. The preferable performance of LiNi0.5Mn1.5O4is obtained with the initial discharge capacity of127.3mAh·g-1at the rate of0.2C by heat-treated time for10h at800℃.The discharge capacity and rate cycle performance of LiNi0.5Mn1.5O4prepared by sol-gel high temperature ball milling are improved and the spinel LiNi0.5Mn1.5O4is obtained with the initial discharge capacity of126.5mAh·g-1at the rate of0.2C by heat-treated time for6h at800℃.Cr-doped and Mg-doped compounds LiNi0.5-xCrxMni.5O4(x=0.05,0.10,0.15), LiNi0.5Mn1.4Cr0.1O4, LiNi0.5Mn1.5-xMgxO4(x=0.02,0.05,0.1), LiNi0.45Mg0.05Mn1.5O4have been prepared by solid state high temperature ball milling after by heat treatment. The results show that the preferable performance is obtained after Cr substitution for Ni rather than Cr substitution for Mn. The optimum amount of Cr substitution for Ni is0.10. The preferable performance is obtained after Mg substitution for Mn with the amount of0.05.Cr-doped and Mg-doped compounds LiNi0.5-xCrxMn1.5O4(x=0.05、0.10、0.15)、 LiNi0.5Mn1.4Cr0.1O4and LiNi0.5Mn1.5.xMgxO4(x=0.02、0.05、0.10) have been prepared by sol-gel high temperature ball milling after by heat treatment. The results indicate that the discharge capacity is remarkably improved when Cr substitution for Ni. The optimum amount is0.10. The cycle performance is improved by Mg-doped. However, the discharge capacity gradually decreases with the amount of Mg increasing.