Effects of lithium excess and SnO2 surface coating on the electrochemical performance of LiNi0.8Co0.15Al0.05O2 cathode material for Li-ion batteries

摘要

Four LiNi0.8Co0.15Al0.05-based Li-ion-battery cathode materials, i.e., the pristine LiNi0.8Co0.15Al0.05, Liexcess Li1+xNi0.8Co0.15Al0.05, SnO2-coated LiNi0.8Co0.15Al0.05 and SnO2-coated Li-excess Li1+xNi0.8-Co0.15Al0.05 are prepared via a facile oxalate coprecipitation route, and are studied with respect to the effects of Li excess and SnO2 coating on the structure and electrochemical properties. X-ray diffraction and X-ray photoelectric spectroscopy demonstrate that a small amount of Li+ and/or Sn2+ ions are incorporated into the transition-metal slabs of the modified materials, and hence reduce the cationic disorder of Li+ /Ni2+. High-resolution transmission electron microscopy and scanning electron microscopy confirm the formation of a SnO2 surface layer that prevents the growth and aggregation of the primary particles during high-temperature solid reaction, and therefore results in formation of the SnO2-cB.Voated materials with nano/submicron sphere-like morphology. Lithium excess and SnO2 coating enhance the electrochemical performance. The SnO2-coated Li-excess Li1+xNi0.8Co0.15Al0.05 exhibits not only higher specific capacity and better rate capability but also excellent cycling stability. After 400 cycles at 1C rate, the capacity is decreased from 123.7 to 86.7 mAh g(-1), giving capacity retention of 70.1%. Li excess is believed to decrease the cationic mixing and SnO2 modification is deemed to restrict the undesirable side reaction between the active material and electrolyte. (C) 2019 Elsevier B.V. All rights reserved.