Synthesis And Modification On Spinel Cathode Material LiNi_0.5Mn_1.5O₄

With the development of electronic devices and automobile industry, there is an urgent demand for efficient and clean energy. Lithium-ion batteries as the light-weight and high energy density energy storage devices, are becoming more and more important in our daily life. Researchers are looking for a cathode material that has quick charge and discharge performance, high energy density, good safety and long life. Among all the cathode material, layer and olivine cathode material can not fully satisfy the ever-increasing demand for batteries with higher energy density, but spinel LiNi_0.5Mn_1.5O₄ has a lot of advantages: high capacity, low cost, non-toxic, abundant raw material and excellent safety performance, which is considered to be a promising high potential cathode material, and has attracted more and more attention.In this work, a hollow spherical morphology spinel LiNi_0.5Mn_1.5O₄ composed of small particles has been synthesized through a universal template-dipping method with different precursors. The physical and electrochemical characterization of those samples synthesized with different precursor indicates that the precursors can influence the physical and electrochemical characteristics of these products. Among those products, the LiNi_0.5Mn_1.5O₄ produced with Li OH?H2O, Ni?NO3?2?6H2O and Mn O2 shows the best electrochemical performance, which displays a discharge capacity of 128 m Ah/g at the current density of 30 m A/g, and excellent cycle life?after 100 cycles, the discharge capacity rentention is as high as 90.5%?, and at the current density of 15 m A/g, 30 m A/g, 75 m A/g, 150 m A/g, 300 m A/g, the rate performance of LiNi_0.5Mn_1.5O₄ remains 130 m Ah/g, 112 m Ah/g, 90 m Ah/g, 55 m Ah/g and 15 m Ah/g, respectively.In order to further improve the cycle performance and rate performance of LiNi_0.5Mn_1.5O₄, the hollow spherical structured LiNi_0.5Mn_1.5O₄ is modified by Al-coating and Al3+-doping. The morphology, structure and electrochemical performance of the two kinds of modified LiNi_0.5Mn_1.5O₄ are investigated by SEM, TEM and charge/discharge test. Compared to the bare LiNi_0.5Mn_1.5O₄, both the Al-coating and Al-doping products show better cycle performance and rate performance. In contrast, the Al-coating products show better rate performance, and the discharge capacity is 131.8 m Ah/g, 125.6 m Ah/g, 120.8 m Ah/g, 115.9 m Ah/g, 106.5 m Ah/g at the current density of 15 m A/g, 30 m A/g, 75 m A/g, 150 m A/g, 300 m A/g, respectively; while the Al-doping products show better cycle performance, and the discharge capacity is 129.1 m Ah/g at the first cycle, the discharge capacity remain 126 m Ah/g after 100 cycles?97.6%?.