Preparation and characterization of high-density spherical LiNi0.8Co0.2O2 cathode material for lithium secondary batteries

The lithium secondary batteries with high power density need the electrode materials with both high specific capacity and high tap-density. LiNi0.8Co0 .2O2 cathode material is a very promising candidate to replace the commerci alized LiCoO2 for lithium secondary batteries. Spherical Ni0.8Co0.2(OH)(2) powders were prepared via a "controlled crystallization" method using NiSO4 , CoSO4, NaOH and NH3.H2O. Spherical LiNi0.8Co0.2O2 powders with order laye red structure were easily synthesized by firing LiOH .H2O and the spherical Ni0.8Co0.2(OH)(2) in oxygen at 750 degreesC for 8 h. The relation among th e "controlled crystallization" conditions and the Ni0.8Co0.2(OH)(2) and LiN i0.8Co0.2O2 powders' structure. particle morphology, particle size. particl e size distribution, and tap-density was investigated. It is shown that wit h the suitable "controlled crystallization" conditions, the tap-density of the spherical LiNi0.8Co0.2O2 powders can be improved as high as 3.24 g cm(- 3), which is remarkably higher than the non-spherical LiNi0.8Co0.2O2 powder s available as commercial cathode materials. The cathode materials also sho w high reversible specific capacity and long cycling life. The high-density spherical LiNi0.8Co0.2O2 cathode materials can greatly improve the power d ensity of the lithium secondary batteries. (C) 2001 Elsevier Science B.V. A ll rights reserved.