High Voltage Performance Of LiCoO₂ Cathode Materials For Lithium-ion Batteries

Lithium-ion batteries as an important energy storage device have been widely used in mobile electronic devices,electric vehicles and other fields.Li Co O₂（LCO）is one of the most important cathode materials for lithium-ion batteries.However,the inherent defects of LCO limits its further application.In this paper,the single metallic element ion doping and Multi-element co-doping in layered LCO cathode materials were studied under high voltage of 4.5 V.The main research contents are as follows:（1）Al-LCO,Mg-LCO,Ti-LCO and W-LCO cathode materials were successfully synthesized by high temperature solid phase method using cobalt trioxide and lithium carbonate as raw materials.Under high voltage of 4.5 V,the cycling performance of Al-LCO,Mg-LCO,Ti-LCO and W-LCO cathode materials are improved compared with Bare-LCO,in which W-LCO sample has the best cycling performance.After 200 cycles,the capacity retention of Bare-LCO（57%）is much lower than that of W-LCO（82%）,which is attributed to the effective inhibition of the"hexagonal-monoclinic-hexagonal"phase transition during the charge and discharge process and the stable structure of LCO.（2）TMA-LCO,TWA-LCO and MAW-LCO were successfully synthesized by high temperature solid phase method using cobalt trioxide and lithium carbonate as raw materials.TWA-LCO sample has the most excellent cycling performance in TMA-LCO,TWA-LCO and MAW-LCO samples.The capacity retention of the TMA-LCO sample is as high as 85%after 200 cycles at a high cut-off voltage of 4.5 V,which is 28percentage points higher than that of Bare-LCO material,which benefits from the inhibition the phase transition of LCO in the process of charge and discharge,the stable structure,and the decrease of the charge transfer impedance.