Enhanced stability and performance of LiNi0.8Mn0.1Co0.1O2 cathodes via vanadium-doped polyoxometalate coating

Nickel-rich layered cathodes, such as LiNi0.8Mn0.1Co0.1O2 (NMC811), offer high specific capacity and energy density but suffer from surface instability, cation mixing, and side reactions at the electrode-electrolyte interface. These issues lead to structural degradation, capacity fading, and reduced cyclic stability in lithium-ion batteries. In this study, we propose a strategy to engineer the interface of NMC811 cathodes with an ultrathin 3D-network vanadium-doped polyoxometalate (PMV) shell, synthesized via a facile wet chemical method, to enhance their electrochemical performance and cyclic stability. Structural characterizations reveal that the uniform PMV coating (thickness around 30–50 nm) preserve the crystal structure of NMC811 while enhancing the stability of the electrode-electrolyte interface and improving lithium-ion diffusion. Electrochemical studies determine that the PMV-coated cathodes achieve a superior initial discharge capacity of 217 mAh g−1, compared to 175 mAh g−1 for the uncoated NMC811 (at 0.1C). The rate capability of the PMV-coated cathode is also enhanced to gain a specific capacity of 87.4 mAh g−1 at 5C, which significantly outperform the uncoated cathode. Detailed investigations indicate that the coating minimizes particle cracking and voltage fading, thus contributing to improved long-term performance and cyclic stability. Applying this ultrathin, ion-conductive PMV coating highlights a viable path for optimizing nickel-rich cathodes.