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

Nickel-rich layered cathodes, such as LiNi 0.8 Mn 0.1 Co 0.1 O 2 (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.