Reduced\nGraphene Oxide-Wrapped Nickel-Rich\nCathode Materials for Lithium Ion Batteries

Abstract

The encapsulation of Ni-rich cathode\nmaterials (LiNi_0.6Co_0.2Mn_0.2O₂) for lithium ion batteries in reduced graphene oxide (rGO)\nsheets is introduced to improve electrochemical performances. Using\n(3-aminopropyl)­triethoxysilane, the active materials are completely\nwrapped with several rGO layers of ∼2 nm thickness. By virtue\nof the great electrical conductivity of graphene, the rGO-coated cathode\nmaterials exhibit much enhanced electrochemical performances of cycling\nproperty and rate capability. In addition, it is shown that the structural\ndegradation of the active materials, which is from the rhombohedral\nlayered structure (<i>R</i>3̅<i>m</i>) to\nthe spinel (<i>Fd</i>3̅<i>m</i>) or rock-salt\nphase (<i>Fm</i>3̅<i>m</i>), is significantly\nreduced as well as delayed due to the protection of the active materials\nin the rGO layers from direct contact with electrolytes and the consequent\nsuppression of side reactions.