关键词: 锂离子电池, 正极, 水溶-蒸发法, 原位XRD, 结构转变

Abstract: The Li-rich Li_1.23Ni_0.09Co_0.12Mn_0.56O₂ material was synthesized via aqueous solution-evaporation route. The structure and morphology of the material were characterized by means of XRD and SEM. The results indicated that the single particle of the product was polygonal with the size of 330 nm and the structure was layered solid solution with a certain amount of Li₂MnO₃. Electrochemical tests showed that the first discharge capacity of the Li-rich layered material was 250.8 mAh·g^-1 at 0.1C，the capacity retention was 86.5% after 40 cycles. Through in-situ XRD study a new phase Li_0.9MnO₂ which would cause electrochemical properties deteriorated due to its structure transformation from layered to spinel came out with a small amount during the first charge-discharge cycle. Moreover, the value of c-parameter increased first and decreased before 4.54 V, and remained stable till the end of the first charge, and then reduced from the first discharge to the second charge continually. However, the value of a-parameter underwent a falling-steady-rising course. The change in the values of the lattice parameters corresponded to the variation of electrochemical behaviors.

Key words: Li-ion battery, cathode, aqueous solution-evaporation route, in-situ XRD, structure transformation