Various strategies to improve LMR performance have been investigated. These include coating as well as modifications to bulk compositions, such as increasing nickel concentration to prevent voltage decay upon oxygen evolution. Modifications to the TM precursor have been leveraged to tune the morphology of the synthesized material as well as the extent of honeycomb-like ordering present in LMR materials. The optimal amount of Li excess is typically that which results in Ni +2 , Co +3 , and Mn +4 in the pristine calcined material. Previous work has investigated the calcination mechanism and optimized some calcination parameters. Optimization via modification to the calcination synthesis protocol is attractive because it does not involve additional steps in the synthesis; this motivates our investigation into the calcination mechanism. A common LMR synthesis involves a coprecipitated TM(OH) 2 (TM = transition metal) calcined with Li 2 CO 3 at a top temperature between 800 °C and 1,000 °C. A lower-temperature pre-lithiation step is sometimes utilized. Some modifications to the time-temperature profile, including a two-step high temperature treatment and quenched cooling, have been shown to improve performance. Morphological engineering during calcination is primarily achieved by modifying the top temperature as well as other methods e.g. by use of a flux medium to induce faceting. The calcination reaction between a TM hydroxide precursor and Li 2 CO 3 is in general given by: We note that hydroxide TM precursors exhibit advantageous tap density but lower capacity compared to carbonate analogs. Their use involves some experimental challenges, including the necessity of an inert atmosphere during precipitation. While the general mechanism of LMR calcination (and calcination of Ni-, Mn-, and Copositive electrode materials, or NMCs, more generally) has been described, some features are inconsistent in the literature and not well-understood. For a typical LMR calcination involving Li 2 CO 3 as Li source, the TM precursor will first decompose to an oxide, then dehydrate, and finally lithiate. Intra-secondary-particle compositional heterogeneity develops as Li and O are incorporated into the bulk structure and TMs diffuse toward the particle surface. In contrast, inter -secondary particle heterogeneity is rarely discussed in a calcination context, despite growing evidence that heterogeneity at these length scales is a driver of cathode performance. A variety of rocksalt-like and spinel-like intermediate phases, lithiated and not, are observed under different conditions. In addition to the gradual H 2 O and CO 2 loss and accompanying lithiation, some studies also observe a sudden mass loss at the melting point of the Li source. In situ X-ray diffraction (XRD) studies of calcination confirm that lithiation accompanies the rapid mass loss. Indeed the Li source melting feature visible in thermogravimetric analysis (TGA) and XRD has appeared, until now, to be relatively general; it is observed across stoichiometric and Li-rich compositions, varying TM compositions, and across different Li sources (e.g. LiOH and Li 2 CO 3 ). Yet it is absent in some studies, and the origin of the feature is poorly understood.