Pre-heat Treatment Procedure And Nano-SnO₂ Coating Of Lithium-rich Cathode Materials Li_1.2Ni_0.13Co_0.13Mn_0.54O₂

Layered Li-rich oxide cathode materials have drawn more and more attention due to their extremely high reversible capacity and high energy density. Unfortunately, layered Li-rich oxide exhibits poor cyclic performance, serious voltage decay and low rate capability, which restricts its application. In this paper, we produced Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ material by a co-precipitation process followed by a high temperature reaction, and achieved process optimization of sintering. In addition, the influence mechanism of presintering process and nano SnO₂ coating were investigated systematically to improve the overall electrochemical properties of Li-rich material.From a practical perspective, we synthesized the lithium rich manganese base solid solution Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode material through coprecipitation-high temperature solid phase method. Moreover, we optimized sintering process inclouding several parameters of lithium contents, presintering temperature and atmosphere by comparing the first charge/discharge capacity and cyclic performance.The Mn_2/3Ni_1/6Co_1/6CO₃ precursor precipitation was pre-sintered in 500, 600 and 700 ℃ respectively. Then, the product after presintering mixed with Li OH to synthetize Li-rich material under same conditions in order to study how changing presintering temperature can affect on the structure and electrochemical performance of Li-rich materials. Due to different presintering temperature, the metal oxide exhibits different metal ion valence, material structure and electronic distribution. Under presintering in 600 ℃, we product a kind of high performance of layer-spinel heterostructure Li-rich sample, which shows high rate performance and cycic stability.Surface modification is considered to be one of the most effective methods to enhance the electrochemical performance of Li-rich cathode materials. The oxygendeficient SnO₂ material is a representative semiconductive material with many oxygen vacancies, which not only can possess the same protecting effect as other semiconductive or insulating materials, but also can take advantage of the oxygen defects inside SnO₂ material to promote the activation reaction of Li₂MnO₃. The asobtained Li-rich material performs more outstanding rate capability and cyclic performance than the pristine Li-rich material under room temperature and high temperature. More importantly, voltage fading is also suppressed.