In Situ Doping Polyanions Enables Concentration-Gradient Ni-Rich Cathodes for Long-Life Lithium-Ion Batteries

The novel Ni-rich cathode materials with concentration-gradient structures have become a research hotspot by virtue of their advantages of high specific capacity and thermal stability. However, the unfavorable interdiffusion of transition metals (TMs) during lithiation leads to flattening of the gradient and weakens the surface passivation effect. Herein, we successfully constructed a concentration-gradient nickel-rich cathode with an average composition of LiNi 0.83 Co 0.05 Mn 0.12 O 2 via a SiO 4 4– polyanion doping strategy (GNCM-Si). SiO 4 4– doping allows the preservation of the concentration-gradient structure at high lithiation temperatures by hindering TM (Ni, Mn) interdiffusion, ensuring high surface stability of nickel-rich cathodes at the end of charge. Besides, the strong Si–O bond effectively stabilizes the lattice oxygen framework, thereby reducing oxygen evolution and further enhancing thermal stability. Accordingly, the as-obtained concentration-gradient cathode demonstrates a high reversible specific capacity of 210.5 mA h g –1 and a high Coulombic efficiency of 89.7% at 0.1C. Impressively, it retains 92.7% of its initial capacity after 500 cycles in pouch-type full cells at 25 °C and 1C. This finding offers a viable idea for constructing concentration-gradient cathodes to meet the high safety requirements of lithium-ion batteries.