Interfacially coupled Li5PMo10V2O40–MoS2 hybrid coatings for enhanced Li+ transport and high-voltage stability of Ni-rich cathodes

Ni-rich layered oxide cathodes offer high energy density but suffer from interfacial degradation and sluggish Li + kinetics at high cut-off voltages. We present a hybrid surface coating that combines a V-substituted Keggin-type polyoxometalate (Li 5 PMo 10 V 2 O 40 , PMV) with mixed-phase (1T/2H) MoS 2 nanosheets (TMD) to improve simultaneously the interfacial stability and the charge-transfer kinetics of NMC811. Conformal ∼30 nm hybrid layers, quantified by ICP-OES at 1.71 wt%, leave the R 3 ‾ m bulk lattice unchanged, as shown by Rietveld refinement, and create a hierarchical mesoporous surface. Single-component controls (NMC-PMV and NMC-TMD) show that the two constituents are complementary: MoS 2 contributes mainly to the rate capability, whereas PMV contributes mainly to interfacial stabilisation; their combination lowers the capacity-fade rate by 13% relative to the independent-action expectation. After 100 cycles at 0.1 C, the hybrid coating reduces the total interfacial resistance from ∼132 Ω to ∼51 Ω, increases the apparent Li + diffusion coefficient derived from impedance from 0.79 × 10 −12 to 3.14 × 10 −12 cm 2 s −1 , limits the increase in voltage hysteresis to 0.74 V (1.03 V for pristine NMC) and slows the decay of the mean discharge voltage from 6.8 to 5.0 mV per cycle. The hybrid cathode retains ∼90% of its capacity after 100 cycles at 0.1 C (2.8–4.7 V), 82.5% after 200 cycles at 1 C and 79.5% after 100 cycles at 1 C and 55 °C, where the amount of dissolved transition metals is reduced by 69%. These results show that coupling a 3D polyoxometalate framework with conductive 2D nanosheets is a promising interfacial design for stabilizing Ni-rich cathodes at high voltage.