Substitution-Mediated Calcination of Nickel-Based Cathodes: Decoupling Lithiation and Crystallization

Nickel-based layered cathodes such as LiNiO₂ offer high energy density for lithium-ion batteries, yet improvements in cycling performance and safety are required for practical use─often achieved through manganese and cobalt substitution as in LiNi_0.80Mn_0.10Co_0.10O₂ (NMC811). However, how such substitution impacts calcination, the key process that governs lithiation, structural ordering, crystallization, and ultimately the resulting material properties, remains unclear. Here, we investigate substitution-mediated calcination dynamics in NMC811 compared to LiNiO₂ using multiscale-correlated in situ spectroscopy and atomistic-to-mesoscale modeling. While both systems progress through the same sequence of intermediates toward the thermodynamically favored layered phase, NMC811 exhibits an earlier onset of layering, concurrent with hydroxide decomposition followed by sluggish crystallization. Modeling reveals that Mn and Co lower the energy barrier for lithium incorporation and ordering but increase the penalty for interlayer gliding, thereby slowing crystal growth at elevated temperatures. This substitution-mediated decoupling of lithiation and crystallization explains the fine-grained microstructure observed in NMC811 versus coarsened particles in LiNiO₂ and establishes a mechanistic framework for predictive microstructure engineering of Ni-based cathodes.