Interfacial effect of nano Al2O3 modifying LiFePO4 to improve capacity retention and rate capability of lithium ion batteries

Abstract

High rate performances and long cycling capability are crucial for lithium ion batteries especially for their applications in vehicles. To improve the performances of cathodes of lithium ion batteries, this work presented an nano Al2O3 modifying LiFePO4 method. Results of scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS) after 300 cycles showed that the Al2O3 coating layer was stable. With a thickness of Al2O3 coating of about 5–6 nm, the electrodes exhibited greater capacity retention over 300 cycles at a rate of 10 C, and the rate capabilities were also enhanced. The cyclic voltammogram (CV) and the electrochemical impedance spectroscopy (EIS) measurements results revealed that lower overpotential and decreased interface impedance were obtained in batteries with the Al2O3 coated LiFePO4 comparing with the pristine LiFePO4 materials. It was found that the Al2O3 modifying layer at the interface is effective in weakening polarization and stabilizing bulk structures of LiFePO4. These observations provide great prospect for making cathode materials with high rate and cycling performances of lithium ion batteries.