(357b) Enhanced Durability of Li1.2Mn0.54Co0.13Ni0.13O2 Cathode Material By Slightly Fluorinated Al2O3 ALD Coating

Li-rich layered oxides have been in focus because of their high specific capacity. However, they still have severe challenges, such as phase transition, mechanical cracking, electrolyte decomposition, transition metal dissolution, poor rate performance, and instability in air. To address the interfacial challenges and achieve a stable cathode-electrolyte interphase, surface modification of cathode materials is the most effective approach to prevent electrolyte decomposition and transition metal dissolution. The basic requirements of the coating layers are (1) controllable thickness, (2) uniform and conformable coating on cathode material surfaces, and (3) good mechanical properties. In this study, Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ (NMC) particles were coated with slightly fluorinated Al₂O₃ film by atomic layer deposition (ALD) in a fluidized bed reactor. The charge/discharge cycling results of the assembled battery showed that its electrochemical performance was significantly improved, compared to that of the uncoated NMC. In addition, after being stored in air for one year, there was no degradation in the electrochemical performance of the fluorinated Al₂O₃ coated NMC, while that of pure Al₂O₃ coated NMC showed a significant decrease. Furthermore, full cells based on coated NMC were assembled; the performance of fluorinated Al₂O₃ coated NMC showed significant improvement, compared to those assembled from uncoated NMC.