The influence of temperature on a nutty-cake structural material: LiMn1−xFexPO4 composite with LiFePO4 core and carbon outer layer for lithium-ion battery

Abstract

The extremely low electronic conductivity, slow ion diffusion kinetics, and the Jahn–Teller effect of LiMnPO4 limit its electrochemical performance. In this work, a nutty-cake structural C–LiMn1−xFexPO4–LiFePO4 cathode material is synthesized by hydrothermal method and further calcined at different temperatures. The influence of calcination temperature on the electrochemical behavior is investigated by X-ray diffractometer, scanning electron microscope, field-emission high-resolution transmission electron microscope, energy-dispersive X-ray spectroscopy, electrochemical impedance spectroscopy and charge–discharge tests. And the performance of C–LiMn1−xFexPO4–LiFePO4 materials has a relationship with its crystal structure. The well-crystallized Sample-600 calcined at 600 °C shows the smallest charge transfer resistance, the largest lithium ion diffusion coefficient (DLi) and the best cycling stability. The discharge capacity of Sample-600 holds around 112 mAh g−1 after the 3rd cycle at 0.1 C rate. The performances improvement of C–LiMn1−xFexPO4–LiFePO4 material can be mainly attributed to the iron diffusion from the LiFePO4 core to the outer LiMnPO4 layer under appropriate calcination temperature.