Comprehensive study of Zr-doped Ni-rich cathode material upon co-precipitation step for Li-ion batteries

LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) is a promising cathode material for high-energy-density Li-ion batteries (LiBs). However, its practical application is limited by capacity fading during electrochemical cycling, mainly associated with cation mixing, structural degradation, and lattice collapse at high voltages. In this work, zirconium (Zr) doping was introduced during the co-precipitation step to improve the structural stability of NMC811 and mitigate its degradation mechanisms. X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) measurements confirmed the incorporation of Zr into the NMC811 host structure at low doping concentrations, whereas concentrations above 0.1 mol% promoted the formation of an additional Li 2 ZrO 3 (LZO) phase. The excess Zr was found to segregate locally on the surface of NMC811 particles rather than forming a homogeneous protective coating. Although higher Zr concentrations improved the rate capability, combined electrochemical and morphological analyses revealed that this enhancement primarily originates from the formation of smaller secondary particles induced by Zr addition during co-precipitation. However, the increased fraction of smaller particles negatively affects long-term cycling stability by promoting a larger electrode–electrolyte interfacial area and enhanced parasitic reactions. These results highlight that controlling the Zr concentration is essential to maximize lattice incorporation while minimizing secondary-phase formation and undesired morphological changes.