Understanding the Origin of the Ultrahigh Rate Performance of a SiO₂-Modified LiNi_0.5Mn_1.5O₄ Cathode for Lithium-Ion Batteries

LiNi_0.5Mn_1.5O₄ (LNMO) is one of the most promising cathode materials for next-generation lithium-ion batteries for rapid charging-discharging applications. The surfaces of LNMO samples are coated with different amounts (0.5-2.0 wt %) of silica (SiO₂) using a cost-effective and scalable ball milling process, and the surface-modified samples shows excellent electrochemical stability with conventional liquid electrolyte. The advantages of this coating are demonstrated by the improved electrochemical performances at ambient and elevated temperatures (25 and 55 °C) using half- and full-cell configurations. The solid electrolyte interface (SEI) and coating properties have been highlighted by ex situ TEM analysis, which indicates the close attachment and good wetting of the SiO₂ layer with the LNMO active particles. Importantly, the 1 wt % SiO₂-coated material cycled at 10, 40, and 80 C rates for 400 cycles exhibits excellent cycling stability with capacity retentions of 96.7, 87.9, and 82.4%, respectively. The 1 wt % SiO₂-coated material also shows excellent cycling stability when charged at 6 C (10 min.) and discharged at C/3 for 500 cycles. The interfacial resistances of the SiO₂-coated LiNi_0.5Mn_1.5O₄ is found to be much lower compared to bare material and does not considerably increase with the amount of coating. Overall, the scalable and cost-effective strategy of SiO₂ coating applied to LiNi_0.5Mn_1.5O₄ lowers the interfacial charge transfer resistance and enables the materials to be suitable for extremely fast-charging electric vehicle battery applications.