In Situ Synchrotron Characterization on Solid-State Synthesis of Ni-Rich Sodium Layered Oxide Cathodes

Layered transition metal oxides (LTMO) are appealing cathode materials in alkali-batteries. However, the performance degradation due to gradually accumulated microstrains within the materials during battery cycling is a limiting factor to the practical applications of these materials. Various approaches have been developed to control microstrain evolution during battery cycling. Nonetheless, controlling microstrains in pristine materials during calcination process, which are critical initiators for the performance degradation, has not been systematically studies. In this work, we developed a diagnose approach for evaluating microstrain evolution during solid-state calcination of LTMO materials based on in situ synchrotron XRD and TXM 3D XANES. We studied the effects of synthesis temperature, heating ramp rate, and chemical composition gradient on microstrain distributions. Based on the findings, an optimal synthesis condition is found for NaNi_0.8Mn_0.1Co_0.1O₂ that shows significantly enhanced cyclability and structural tolerance.