The Best of Both Worlds? Probing the Feasibility of Acquiring High-Energy and -Stability LiNi0.8Mn0.1Co0.1O2–LiFePO4 Materials through Mechanofusion Dry-Coating

Microsized polycrystalline Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC) was dry-coated with 2–4 wt % nanosized LiFePO4 (LFP) through a mechanofusion process. The effect of the surface modification was investigated by physicochemical and electrochemical characterization, focusing on cycle life and thermal stability. Cross-section SEM/EDS confirms the presence of a LFP coating on the NMC surface. Electrochemical characterization shows that both the NMC bulk and the LFP coating are electrochemically active and that both uncoated NMC and LFP-coated NMC have similar rate capabilities up to 4 wt % LFP coating in half-cell configuration. Long-term testing in full cells balanced against graphite shows that the uncoated NMC and LFP-coated NMC have similar initial electrochemical performance and cycle life characteristics. The reference NMC and coated NMC–4 wt % LFP respectively retain 83% and 84% of their 0.1 C capacities after 367 cycles, with post-mortem analysis confirming the preservation of the LFP coating. DSC measurements reveal that the LFP coatings do not affect the onset of the thermal decomposition. Increasing the amount of coating material to 6–10 wt % did not improve the electrochemical stability further. The ineffectiveness in improving the cycling and thermal stability is attributed to the porous character of the LFP coating and the inadequate coverage across the wide NMC particle size distribution.