In Situ XRD Studies During Synthesis of Single-Crystal LiNiO₂, LiNi_0.975Mg_0.025O₂, and LiNi_0.95Al_0.05O₂ Cathode Materials

High-nickel, cobalt-free, single-crystal positive electrode materials could provide the ultimate intersection of high-specific capacity, low cost, and long-lifetime in lithium-ion batteries. In this work, the synthesis of LiNiO2, LiNi0.975Mg0.025O2, and LiNi0.95Al0.05O2 is studied by dynamic XRD during heating, in order to guide improvements in synthesis procedures. A comparison of Li2CO3 and LiOH·H2O lithium sources shows that either can be used to prepare these materials, but Li2CO3 requires a higher temperature. Mg doping is shown to be beneficial in lowering the temperature required to get fully lithiated, crystalline material. Additional experiments show that synthesis with a 480 °C preheat step, or synthesis directly from individual metal hydroxides (without a precursor), could be used as potentially viable alternative synthesis methods.