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

Abstract

The practical realization of Nickel-rich layered oxide cathode materials such as LiNi_0.8Mn_0.1Co_0.1O₂ (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 Si_xZn_yO_z 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 Si_xZn_yO_z ACEI thin films on NMC811. After prolonged cycling the ACEI-coated NMC811 full cells significantly improved the electrochemical performance than pristine NMC811 by ~12%.