Artificial cathode electrolyte interphase for improving high voltage cycling stability of thick electrode with Co-free 5 V spinel oxides

Spinel-type cathode LiNi0.5Mn1.5O4 (LNMO) has intrigued the transportation industry due to its high operating voltage and total elimination of the expensive cobalt element. However, LNMO cathode with high mass loading (> 3 mAh/cm2 in areal capacity) has suffered from excessive capacity degradation upon long cycling. Here, a robust Al2O3 surface layer is introduced to the thick LNMO electrode via atomic layer deposition (ALD). The capacity retention in full cells with the graphite anode is improved from 46.3% to 75.3% after 300 cycles with cutoff voltage up to 4.85 V, while enabling average Coulombic efficiency of 99.9% during the cycling. The post-mortem analyses reveal that the Al2O3 surface layer would convert to Al-O-F /Al-F species upon cycling, offering stable interphase to protect the cathode material. These results demonstrate the significance of surface modification enabling high voltage cathode for next-generation LIBs.