Synthesis of metal ion substituted P2-Na2/3Ni1/3Mn2/3O2 cathode material with enhanced performance for Na ion batteries

• Metal ion substituted P2-Na2/3Ni2/9M1/9Mn2/3O2 (M=Mg, Al, Fe, and Co) was prepared.
• Metal ions substitution barely affects the main structure of P2-Na2/3Ni1/3Mn2/3O2.
• Short-range structure of P2-Na2/3Ni1/3Mn2/3O2 changed after metal substitution.
• Metal ion substituted P2-Na2/3Ni2/9M1/9Mn2/3O2 exhibits improved performance.

The structure and electrochemical properties of metal ion substituted P2-Na2/3Ni2/9M1/9Mn2/3O2 (M=Mg, Al, Fe, and Co) were investigated. X-ray diffraction (XRD) results reveal that the partial substitution of Ni with other metal ions has no effect on the main structure of P2-Na2/3Ni1/3Mn2/3O2. Raman scattering and Fourier transform infrared spectroscopy (FTIR) results demonstrate that short-range structure might be affected. In contrast to the multi-step type charge–discharge profiles for pristine P2-Na2/3Ni1/3Mn2/3O2, metal substituted samples show sloping charge–discharge curves. Furthermore, they exhibit enhanced cycling performance compared to P2-Na2/3Ni1/3Mn2/3O2. Our study suggests that further modification of P2-Na2/3Ni1/3Mn2/3O2 with metal substitution would shed some light on achieving layered Na-containing compounds cathode material with enhanced performance for Na ion batteries.