Preparation and characterization of high-density spherical LiNi 0.8Co 0.2O 2 cathode material for lithium secondary batteries

Abstract

The lithium secondary batteries with high power density need the electrode materials with both high specific capacity and high tap-density. LiNi 0.8Co 0.2O 2 cathode material is a very promising candidate to replace the commercialized LiCoO 2 for lithium secondary batteries. Spherical Ni 0.8Co 0.2(OH) 2 powders were prepared via a “controlled crystallization” method using NiSO 4, CoSO 4, NaOH and NH 3·H 2O. Spherical LiNi 0.8Co 0.2O 2 powders with order layered structure were easily synthesized by firing LiOH·H 2O and the spherical Ni 0.8Co 0.2(OH) 2 in oxygen at 750°C for 8 h. The relation among the “controlled crystallization” conditions and the Ni 0.8Co 0.2(OH) 2 and LiNi 0.8Co 0.2O 2 powders’ structure, particle morphology, particle size, particle size distribution, and tap-density was investigated. It is shown that with the suitable “controlled crystallization” conditions, the tap-density of the spherical LiNi 0.8Co 0.2O 2 powders can be improved as high as 3.24 g cm −3, which is remarkably higher than the non-spherical LiNi 0.8Co 0.2O 2 powders available as commercial cathode materials. The cathode materials also show high reversible specific capacity and long cycling life. The high-density spherical LiNi 0.8Co 0.2O 2 cathode materials can greatly improve the power density of the lithium secondary batteries.