Structural, electrochemical, and Li-ion diffusion properties of Mg&Mn dual doped LiNiO2 cathode materials for Li-ion batteries

A Co-free LiNiO2 (LNO) cathode material with high reversible capacity and low cost is promising for applications in lithium-ion batteries; however, it suffers from severe polarization increase and stress accumulation induced cracks, limiting its commercial applications. We investigate structural, electrochemical cycling, and lithium-ion diffusion properties of a 5 mol% Mg&Mn dual doped LNO cathode material compared with those of a bare LNO counterpart. The results show that the Mg&Mn dual doped LNO exhibit a capacity retention of 98.70% after 100 cycles at 1C, in contrast to only 69.89% for the bare LNO. Furthermore, combined electrochemical impedance spectroscopy and galvanostatic intermittent titration technic analysis reveal that LNMMO half-cell shows a much slower increase of charge transfer impedance and a more stable Li+ diffusion coefficient ~ (1- 10) x10-11 cm2/s at different voltages. In contrast, the LNO half-cell exhibits a faster increase of charge transfer impedance and a significantly fluctuating Li+ diffusion coefficient at phase change points. Ex-situ XRD studies also reveals that LNMMO cathode material shows limited lattice expansion after prolonged cycling, mitigating and particle cracks and consequently improving the structural stability and cycling performance.

Automated summary

The dual-doped LNO cathode material with magnesium and manganese exhibits higher capacity retention, more stable charge transfer impedance, and Li+ diffusion coefficient, improving its structural stability and cycling performance compared to the bare LNO counterpart.