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.