Comparison of Different Synthesis Methods for LiNi0.5Mn1.5O4—Influence on Battery Cycling Performance, Degradation, and Aging

The high-voltage spinel LiNi0.5Mn1.5O4 is one of the most promising candidates for use in high-energy-density lithium-ion batteries. To investigate the influence of the synthesis method and the resulting particle morphology on the electrochemical performance, performance degradation, and aging, different synthesis routes for LiNi0.5Mn1.5O4 were evaluated in this study. Inhomogeneous transition metal cation intermixing and exposure to high temperatures during synthesis led to the formation of a small amount of impurities, which had a severe impact on the electrochemical performance. Furthermore, the particle morphology influences the electrolyte decomposition and the formation of the cathode electrolyte interphase (CEI) on the surface of particles. Moreover, transition metal dissolution was investigated by analyzing the Ni and Mn content in the electrolyte after constant current charge–discharge cycling. The results suggest that an unstable delithiated structure at high potentials leads to the dissolution of Mn and Ni into the electrolyte, whereas the particle morphology had only a minor influence on the extent of transition metal dissolution.