Enhanced Surface Stability of LiNi_0.95Mg_0.05O₂ Cathode Material by Gradient Coprecipitation Synthesis

A coprecipitation synthesis was performed to prepare a conventional LiNi_0.95Mg_0.05O₂ (LNMO) cathode and a gradient-modified variant (G-LNMO) for comparative analysis. G-LNMO featured a gradient structure with nickel content decreasing (98.86 to 87.93%) and magnesium increasing (1.24 to 14.73%) from the particle core to the surface. This design resulted in a more ordered layered structure and superior crystallinity than LNMO. Electrochemically, G-LNMO significantly outperformed LNMO, delivering higher initial discharge capacities (216.4 mAh g^-1 at 0.1C vs 197.1 mAh g^-1) and superior rate capability (196.8 mAh g^-1 at 1C vs 183.1 mAh g^-1). It also demonstrated excellent cycling stability, retaining 88.6% capacity after 100 cycles compared to 68.2% for LNMO. The enhanced performance is attributed to magnesium occupying both lithium and nickel sites, providing dual structural support that inhibits crack formation and improves the stability of the layered oxide framework. G-LNMO is a promising high-performance cathode material for lithium-ion batteries.