Ta/Ti Codoped Concentration\nGradient High-Ni Cathodes\nfor Long-Life Li-Ion Batteries

Full concentration gradient nickel-rich ternary materials\n(GNCM)\ndemonstrate cost-effectiveness and higher discharge capacity as lithium-ion\nbattery (LIB) cathodes. However, unsatisfactory rate performances\nof GNCM are recognized as a limitation caused by concentration gradient\nelimination and surface Mn enrichment during the calcination process.\nTo address this issue, a Ta/Ti codoping approach is developed, showing\nthat Ta<sup>5+</sup> can upgrade the surface of the primary particle\nto mitigate element diffusion at the grain boundaries, and meanwhile,\nTi<sup>4+</sup> can stabilize Ni–O to weaken Ni<sup>2+</sup> migration. Such impacts on GNCM bring in significant advantages\nin terms of structure and performance to prevent irreversible phase\ntransitions from the layered to the rock-salt structure and accelerate\nthe diffusion kinetics of Li<sup>+</sup> and electrons with increased\nelectric conductivity. Consequently, the Ta/Ti codoped GNCM (labeled\nas GNCM-TaTi) delivered a high reversible capacity of 210.9 mAh/g\nat an initial rate of 0.1C and maintained 106.8 mAh/g even at a high\nrate of 10C. The capacity retentions can remain 98.2 and 94.7% after\n100 cycles at 0.5 and 3C, respectively. Further evaluations of GNCM-TaTi\nin a pouch cell show a capacity retention of 90.3% at 3C after 500\ncycles. The presented Ta/Ti codoping validates an effective route\nto strengthen the LIB performance of the high-Ni NCM with a full concentration\ngradient structure.