Atomic layer deposition of a thin TiO2 layer on nickel-rich cathode NCM83 for improved cycling stability

Abstract

Nickle-rich layered oxides (NCMs) are promising cathode materials for high energy-density lithium-ion batteries (LIBs). However, NCMs suffer from poor cycling stability because of severe interfacial side reactions and phase transitions during cycling. Here, we show that by coating a thin and uniform layer of titanium dioxide (TiO2) on the surface of NCM83 (LiNi0.83Co0.11Mn0.06O2) using the atomic layer deposition (ALD) method, its cycling stability is significantly improved with 87.3% capacity retention after 100 cycles at 1C, in sharp contrast to NCM83 without TiO2 coating with only 44.3% capacity retention under the same electrochemical measurement conditions. XPS and ToF-SIMS characterization results reveal that the coated TiO2 layer promotes the formation of a LiF-rich stable cathode/electrolyte interphase (CEI), which effectively suppresses interfacial side reactions and mitigates phase transitions. In-situ XRD characterization results show that the TiO2 coating layer regulates the phase transition process due to mechanical confinement effects, which alleviates crystal distortion and stress accumulation. This work offers an effective approach to modifying nickel-rich cathode materials for high energy-density LIBs.