Modification of LiCoO2 through rough coating with lithium lanthanum zirconium tantalum oxide for high-voltage performance in lithium ion batteries

Abstract

In this study, the spray-drying technique was used to apply a 0.5 at%, 1 at%, and 1.25 at% of lithium lanthanum zirconium tantalum oxide (Li6.75La3Zr1.75Ta0.25O12) powder coating on the surface of lithium cobalt oxide (LiCoO2) cathode materials. Subsequently, these materials were sintered for either 5 or 10 h at 800 °C to obtain LiCoO2 cathode materials with a rough coating. X-ray diffraction, cyclic voltammetry, electrochemical impedance spectroscopy, and differential scanning calorimetry were then conducted to analyze differences in the structure, electrochemical properties, and thermostability of the materials before and after surface modification. The modified LiCoO2 cathodes with Li6.75La3Zr1.75Ta0.25O12 rough coating had more than twice the discharge capacity as the bare LiCoO2 cathode at a high discharge current density when the cutoff voltage ranged from 2.8 to 4.5 V. In addition, 1 at% Li6.75La3Zr1.75Ta0.25O12 coating and 5 h of sintering at 800 °C resulted in the optimal capacity retention of 85.4% after 80 cycles and a slower exothermic reaction than that of the bare LiCoO2 cathode. Thus, rough coating an adequate quantity of Li6.75La3Zr1.75Ta0.25O12 powder on a LiCoO2 cathode mitigated the reaction between the cathode material surface and electrolyte, stabilizing the main structure and enhancing the ionic conductivity and electrochemical characteristics of the material.