Quaternary layered Cr‐doped modified NCMFe cathode material for Lithium‐Ion Batteries

Abstract

A series of cathode materials, Li[Ni0.6Co0.12Mn0.2Fe0.08]1‐xCrxO2 (x=0, 0.02, 0.04, 0.06), are synthesized via the co‐precipitation method. Structural characterization shows that Cr3+ ions are successfully incorporated into the material structure and evenly dispersed on the surface of crystal particles with other metal elements. The Cr‐doped material shows a well‐defined hexagonal layered structure with less cation mixing, and the increase in interionic and interlayer distances is beneficial for the transport of lithium ions. Compared to the pure NCMFe phase, the cyclic and rate performances of the Cr‐doped quaternary materials have been significantly improved. Among them, the 4Cr material exhibits the best electrochemical performance. The capacity retention rate after 50 charge‐discharge cycles at 0.1 C was increased from 74.83% to 87.32%. The rate performance has also increased from 87.6% to 92.69%. The Cr‐doped cathode can reduce the charge transfer resistance and enhance the stability of the layered structure, which results in outstanding electrochemical performance of the Cr‐doped cathode. CV and EIS tests were conducted on materials with various Cr doping levels, further confirming that Cr doping can reduce the degree of polarization in electrode materials, enhance charge and discharge reversibility, and reduce the charge transfer resistance of materials.