Surface deterioration dependent on the crystal facets of spinel LiNi_0.5Mn_1.5O₄ cathode active material

The spinel LiNi_0.5Mn_1.5O₄ (LNMO) cathode active materials (CAMs) are considered a promising alternative to commercially available cathodes such as layered and polyanion oxide cathodes, primarily due to their notable safety and high energy density, particularly in their single-crystal type. Nevertheless, the industrial application of the LNMO CAMs is severely inhibited due to the interfacial deterioration and corrosion under proton-rich and high-voltage conditions. This study successfully designed and synthesized two typical types of crystal facets-exposed single-crystal LNMO CAMs. By tracking the electrochemical deterioration and chemical corrosion evolution, this study elucidates the surface degradation mechanisms and intrinsic instability of the LNMO, contingent upon their crystal facets. The (1 1 1) facet, due to its elevated surface energy, is found to be more susceptible to external attack compared to the (1 0 0) and (1 1 0) facets. Our study highlights the electrochemical corrosion stability of crystal plane engineering for spinel LNMO CAMs.