In Situ Insights into Cathode Calcination for Predictive Synthesis: Kinetic Crystallization of LiNiO₂ from Hydroxides

Abstract

Calcination is a solid‐state synthesis process widely deployed in battery cathode manufacturing. However, its inherent complexity associated with elusive intermediates hinders predictive synthesis of high‐performance cathode materials. Here, we use correlative in situ X‐ray absorption/scattering spectroscopy to investigate the calcination of nickel‐based cathodes, focusing specifically on LiNiO2 synthesized from hydroxides. By combining in situ observation with data‐driven analysis, we reveal concurrent lithiation and dehydration of Ni(OH)2 and, consequently, the low‐temperature crystallization of layered LiNiO2 alongside lithiated rocksalts despite its thermodynamic unfavorability. Following early nucleation, layered LiNiO2 undergoes sluggish crystallization and structural ordering while depleting rocksalts until full lithiation. Subsequent high‐temperature sintering induces rapid crystal growth, accompanied by undesired delithiation and structural degradation. These observations are further corroborated by mesoscale modeling, emphasizing that, even though calcination is thermally driven and favors transformation towards thermodynamically equilibrium phases, the actual phase propagation and crystallization can be kinetically tuned via lithiation to achieve structural and morphological control during the calcination process.This article is protected by copyright. All rights reserved

Computationally Guided Synthesis of Battery Materials

“…Formation of a layered Li 1– x NiO 2 ( x < 1) phase occurs at temperatures exceeding 436 °C, with further heating required to complete its lithiation. Several related studies have reported similar findings, in which LiOH begins to react with and lithiate NiO at temperatures ranging from 210 to 450 °C. ,, In contrast, Li 2 CO 3 does not react with the Ni precursor in appreciable amounts until the synthesis temperature exceeds 600 °C, likely due to the higher melting point of Li 2 CO 3 (723 °C) in comparison to LiOH (462 °C) . Increased reactivity at low temperature has also been reported when using LiOH to synthesize other cathode compositions. , These low temperatures not only diminish Ni Li antisite defects, but also provide improved control over product morphology at the expense of higher material costs and more processing challenges.…”