Improving the electrochemical behavior of Li1.27Cr0.2Mn0.53O2 cathode via the incorporating Cu2+ cations into the transition metal slab

Abstract

Cu-doped lithium-rich Li1.27Cr0.2Mn0.53-xCuxO2 cathode materials were synthesized by a solid phase reaction. The X-ray diffraction (XRD) investigation showed that the doped Cu cations were incorporated into the hexagonal lattice, and that no impurity phase was generated. Scanning electron microscopy (SEM) observation also implied that the crystal growth was suppressed when Cu ions were introduced. Further investigation with Electron spin resonance (ESR) confirmed that oxygen vacancies were generated due to the non-equal valence substitution of Cu in the transition metal slab. The vacancy containing Li1.27Cr0.2Mn0.50Cu0.03O2 material showed the best results, with an initial discharge capacity of 230.6 mAh·g−1, and a capacity retention of 91.8% after 100 cycles. When compared to the data of the pristine sample without Cu doping, obvious improvements of 22% and 7.4% were confirmed. Such improvement can be ascribed to the higher electronic conductivity (1.761 × 10−7 S cm−1 vs 3.51 × 10−8 S cm−1), and faster Li ion diffusion (1.081 × 10−10 cm2 s−1 vs 2.423 × 10−11 cm2 s−1), caused by the existence of the oxygen vacancies. The excellent electrochemical behavior of the materials prepared by our approach, shows their high potential for future application in the lithium ion battery (LIB) field.