Investigation the improvement of high voltage spinel LiNi0.5Mn1.5O4 cathode material by anneal process for lithium ion batteries

The spinel LiNi0.5Mn1.5O4 (LNMO) has been attracted great attention as lithium ion cathode material due to its high voltage and large energy density. However, the practical application of LNMO is still limited by poor cycling stability. Herein, to improve the cycling stability of spinel LNMO, it was treated with anneal process at 900 °C for 2 h after prepared by traditional solid-state method (LNMO-A). LNMO-A sample presented better electrochemical property especially under high rate, with capacity of 91.2 mAh g−1 after 1000 cycles under 10 C. Its superior electrochemical property was ascribed to the anneal process, resulting a stable crystal structure, indicated by XRD and Raman results of electrodes after 1000 cycles under 10 C and the longer solid-solution reaction, revealed by in-situ XRD. In addition, the optimized particle size, micro morphology and the larger BET area surface induced by the recrystallization in anneal process also contributes to its superior electrochemical property. What's more, the thin layer, which interacted LNMO-A particles with each other, induced by particles remelting in anneal process is also beneficial for its excellent electrochemical property. This study not only improved the electrochemical properties by anneal process, but also revealed the origins and mechanisms for its improvement.