| Today, the most widely used cathode material for commercial lithium ion batteries is LiCoO2. Due to it's relatively high cost and poor safety, LiCoO2 is very difficult to meet the development demands of lithium ion battery in the future. Therefore, much more attempts are focused on developing new kinds of cathode materials with lower cost and higher performance which can substitute LiCoO2 materials. Comparing with LiCoO2, Li(Ni1/3Co1/3Mn1/3)O2 has lower cost and higher safety which can also be used in small-type lithium ion batteries. In this paper, we investigated the synthetic condition, structure, composition, and electrochemical performance of Li(Ni1/3Co1/3Mn1/3)O2. The effects of synthetic conditions on structure and electrochemical performance have been investigated and the optimum synthetic conditions were obtained. The obtained cathode materials were investigated by SEM, XRD, galavanostatic charge and discharge test, et al.In this paper, novel cathode materials with excellent electrochemical performance were prepared by anion-cation compound substitution at the base of Li(Ni1/3Co1/3Mn1/3)O2, which was attractive all around the world. Si and F elements were choosen as the co-doping agents to improve the electrochemical properties of Li(Ni1/3Co1/3Mn1/3)O2. The results indicated that Si, F co-doping can effectively steady the layered structure and improve rate-discharging capability of Li(Ni1/3Co1/3Mn1/3)O2 since Si-F substitution combined the increasing capacity of F-doping material with the good cyclability of Si-doping materials. In the range of 2.8-4.3 V, the Li[Ni1/3Co1/3Mn1/3]Si0.04O1.96F0.04 delivers an initial capacity of 176.9 mAh·g-1 and its capacity retention is 92.1% after the 20th cycle. The conclusion could be drawn that Si-F compound substitution elevated the capacity and improved the cyclability. Study of AC impedance indicated that Si, F co-doping can obviously suppress the increase of electrochemical impedance in the course of discharging at larger rate current. Therefore, it is a promising method for Si-F compound substitution in this kind of cathode materials of Li-ion batteries. |
PDF Full Text Request