High Potential And Capacity Of Layered Structure Li-rich Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ Composite As Cathode Material For Lithium-ion Batteries

With the development of our society, our living standard increased,and also for the need of energy. As the quantum of traditional fuel energy is limited, the development of sustainable clean energy is significant. Since SONY introduced the first commercial Li-ion battery in 1991, it has gone deep into our life in many aspects. To satisfy the need for high energy, high work voltage and low price of portable energy storing devices, the research for Li-ion has never been interrupted, and we wish more breakthrough in technology of every aspect for Li-ion batteries. Compared with the conventional cathode material of LiCo O2, LiMn2O4 and LiFePO4, layered lithium-rich material xLi2MnO3·(1-x)LiMO2(M=Ni, Co, Mn···) received great attention and much research, because of its high capacity, high work potential, low cost and environment friendliness.In this paper, we synthesized spherical nano-powder of Li1.2Mn0.54Ni0.13Co0.13O2 by co-precipitation. On the basis of the favorable synthesis condition, we futher enhanced the electrochemical properties by surface-modification. We obtained the information of their structure, composition and morphology by XRD, SEM, TEM measurement. To investigate the properties of the layered lithium-rich cathode composites, half coin-cells were assembled and tested.We synthesized layered lithium-rich cathode composites with transition-metal sulfate and sodium bicarbonate as raw material. The precursor of carbonate was prepared by co-precipitation, subsequently mixing with lithium carbonate and annealing to get the final products. To studying the influence of different annealing temperatures and annealing time on the composite’s structure, morphology, and electrochemical property, we take 750 °C, 800 °C, 850 °C, 900 °C as annealing temperatures, and 9 h, 12 h, 15 h, 18 h as annealing times. The best composition synthesis parameters were found to be T=850 °C and t=15 h. The cathode of layered lithium-rich composites were assembled into coin cell and cycled between 2.0~4.8 V at the current density of 0.2 C(1 C=300 mAh/g), and the first discharge capacity was 202.3 mAh/g with a coulombic efficiency of 62%. The average discharge capacity was 103 mAh/g of the whele 60 cycles at a current density of 1 C.For solving the problem of low first coulombic efficiency, fast capacity decay and worse cycling stability, the layered lithium-rich cathode of Li1.2Mn0.54Co0.13Ni0.13O2 was treated by acid etching and LiMn1.5Ni0.5O4 layer coating. With a coated layer of LiMn1.5Ni0.5O4, the layerd Li1.2Mn0.54Co0.13Ni0.13O2 cathode has a discharge capacity of 150 mAh/g after 60 cycles at 1 C rate, with a 50% improved capacity and a 87.7% capacity reservation.