Improved Electrochemical Performance of Li1.25Ni0.2Co0.333Fe0.133Mn0.333O2 Cathode Material Synthesized by the Polyvinyl Alcohol Auxiliary Sol-Gel Process for Lithium-Ion Batteries

摘要

A lithium-rich manganese-based cathode material, Li_(1.25)Ni_(0.2)Co_(0.333)Fe_(0.133)Mn_(0.333)O_2, was prepared using a polyvinyl alcohol (PVA)-auxiliary sol-gel process using MnO_2 as a template.The effect of the PVA content (0.0–15.0 wt%) on the electrochemical properties and morphology of Li_(1.25)Ni_(0.2)Co_(0.333)Fe_(0.133)Mn_(0.333)O_2 was investigated.Analysis of Li_(1.25)Ni_(0.2)Co_(0.333)Fe_(0.133)Mn_(0.333)O_2 Xray diffraction patterns by RIETAN-FP programconfirmed the layered -NaFeO2 structure.The discharge capacity and coulombic efficiency of Li_(1.25)Ni_(0.2)Co_(0.333)Fe_(0.133)Mn_(0.333)O_2 in the first cycle were improved with increasing PVA content.In particular, the best material reached a first discharge capacity of 206.0 mAhg?1 and best rate capability (74.8 mAhg?1 at 5 C).Meanwhile, the highest capacity retentionwas 87.7%for 50 cycles.Finally, electrochemical impedance spectroscopy shows that as the PVAcontent increases, the charge-transfer resistance decreases.