Advanced Molecular Layer Deposition of Si_xZn_yO_z Thin Film Coatings for Improved Electrochemical Performance of NMC811

Abstract

The practical realization of Nickel‐rich layered oxide cathode materials such as LiNi0.8Mn0.1Co0.1O2 (NMC811) is hampered by several structural and interfacial instabilities over prolonged cycling. Several reports have proposed surface passivation via an artificial cathode electrolyte interphase (ACEI) as a promising method for mitigating the parasitic reactions affecting NMC811 while simultaneously improving its electrochemical performance over prolonged cycling. Herein, we report an in‐house designed (tBuMe2Si)2Zn single source precursor for developing SixZnyOz ternary CEI thin films on NMC811 via molecular layer deposition (MLD) in combination with O3 or H2O as oxidizing agent. We demonstrate that the single precursor (tBuMe2Si)2Zn avoids the need for two different precursors (Si & Zn). In‐depth spectroscopic studies reveal the mechanism of the formation of organosiloxane/zinc‐oxide composite thin film, via intermediates of unprecedented organo‐silicon‐zinc compounds. Understanding the reaction mechanism paved the path for a successful deposition of ACEI on NMC811. Rate capability studies shows the ACEI protected cathodes exhibit higher discharge capacity at 4 C than pristine NMC811. Furthermore, studies on full cells with graphite anode were conducted to evaluate the practical viability of SixZnyOz ACEI thin films on NMC811. After prolonged cycling the ACEI‐coated NMC811 full cells significantly improved the electrochemical performance than pristine NMC811 by ~12%.