Preparation of neodymium‐doped <scp> LiMnPO ₄ </scp> /C cathode by sol‐gel method with excellent electrochemical performance for lithium‐ion batteries

Abstract

The porous spherical structure neodymium-doped LiMn1−xNdxPO4/C nanoparticles have been prepared through glycolic acid-assisted sol-gel method. The neodymium-ion doping effect on the crystalline microstructure, crystal appearance, and electrochemical parameters of LiMnPO4/C cathodes have been detected by X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), charge and discharge test, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) method. XRD patterns show that a proper amount of neodymium-ion doping could not change the host crystal structure; combined with EDS spectra, we could conclude that Nd3+ has successful embedding into the lattice structure of LiMnPO4/C. SEM analysis shows that the LiMn0.94Nd0.06PO4/C sample has the uniform and fine particles diameter distribution in comparison with other doped samples. The electrochemical measurement results indicate that the LiMn0.94Nd0.06PO4/C has the initial discharge specific capacity of 155.2 mAh/g at 0.05 C discharge rate; after 200 cycles, the capacity value reduces slightly to 138.7 mAh/g, the capacity retention rate is maintained at 89.4%. The LiMn0.94Nd0.06PO4/C has high-rate discharge performance with the specific capacity value of 128.0 mAh/g (10 C). The results conclude that a proper amount of neodymium-ion doping ratio could effectively enhance the lithium-ion diffusivity and improve high-rate performance of LiMnPO4 cathode materials.