Electrophoretically deposited artificial cathode electrolyte interphase for improved performance of NMC622 at high voltage operation†

High-voltage Ni-rich active materials are widely used in cathodes of high-energy-density lithium-ion batteries (LIBs). However, the high charge cutoff voltages lead to significant degradation and capacity fading, caused by electrolyte decomposition, transition metal dissolution, structural distortion, and more. Herein, we present an artificial cathode electrolyte interphase (ART-CEI) as a protective coating on the surface of the LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622) cathode. A composite film, prepared from argyrodite Li₆PS₅Cl (LPSC) ion conducting nanoparticles and a polymerized ionic liquid (PIL) as a binder, was electrophoretically deposited on the surface of the cathode. We found that capacity retention at high-voltage operation (4.3 and 4.5 V) is improved due to the coating. Besides the stability improvement, the electrochemical performance of the coated cathode shows an enhancement in rate performance and lower resistances of the anode solid electrolyte interphase (SEI), the cathode electrolyte interphase (CEI), and charge transfer processes during cycling.