Granularity control enables high stability and elevated-temperature properties of micron-sized single-crystal LiNi_0.5Mn_1.5O₄ cathodes at high voltage

The development of high energy density LiNi_0.5Mn_1.5O₄ (LNMO) cathode materials for lithium-ion batteries are challenged by capacity degradation, which becomes more aggravated particularly at elevated temperatures. Thus, the practical strategy with facile craft and the viability of large-scale preparation for industrialized applications should be developed urgently. In this work, a micron-sized LNMO single crystals is synthesized by a facile two-step method consisting of an alcohol gel solvent method and a segmented sintering reaction. Results show that the truncated polyhedron LNMO-900 sample, with the moderate D₅₀ characteristic value of 4.429 μm and the highest tap density of 2.31 g cm⁻³, provides a stable structural and chemical stability even at elevated testing temperature due to its moderate specific surface area and the few Fd-3m phase. The LNMO/Li half-cells display more excellent capacity retention (87.3% at 1C and 25 °C after 500 cycles) and better thermal stability (76.65% at 1C and 55 °C after 200 cycles) than those of the single crystals of LNMO-850 and LNMO-950. Besides, the XPS, in-situ EIS and electrochemical tests results also prove that the LNMO-900 exhibits the lowest electrolyte decomposition degree, owing to a thin and effective solid-electrolyte interfacial film formed after cycles.