Influence of lithium silicate coating on retarding crack formation in LiNi0.5Co0.2Mn0.3O2 cathode particles

LiNi0.5Co0.2Mn0.3O2 particles coated with lithium silicate were prepared via a precipitation method and their charge and discharge properties were investigated. The capacity retention and coulombic efficiency of the 0.5 wt% lithium silicate-coated LiNi0.5Co0.2Mn0.3O2 was improved at a high cut-off voltage of 4.6 V. Cross-sectional scanning electron microscope images revealed that extensive cracks were formed within the uncoated LiNi0.5Co0.2Mn0.3O2 particle along the grain boundaries after the charge and discharge cycling, while the crack generation was significantly inhibited for the coated particles. From cross-sectional transmission electron microscope analysis, it was shown that Si-rich regions were concentrated not only on the surface, but also at the grain boundaries even at a depth of 400 nm from the surface of the lithium silicate-coated sample. These results suggested that the Si-rich regions inhibited the crack formation and prevented the intrusion and the decomposition of the electrolyte solution within the particles. Consequently, lithium silicate coating is an effective way for improving the charge and discharge characteristics of LiNi0.5Co0.2Mn0.3O2.