Multifunctional Doping Strategy to Develop High-Performance Ni-Rich Cathode Material

摘要

A high fraction of reactive Ni~(4+) ions at the cathode–electrolyte interfaces leadto capacity fading of Ni-rich cathodes. Therefore, a core–shell (CS) designencapsulating the Ni-rich region by a Ni-less shell is an effective approachfor improving the cycling stability of the cathodes. However, with increasingaverage Ni content to increase the capacity, the thickness of the shell shouldbe reduced or the Ni fraction of the shell will be inevitably higher, making itsusceptible to interdiffusion, which flattens the concentration gradient duringthe lithiation process. Herein, the limit of the average Ni composition in theCS-type cathode is pushed to 94 via Ta doping, which suppresses interdiffusionby segregating the Ta-rich phases at the particle boundaries. Ta dopingallows the maintenance of the highly aligned microstructure and the orderedintermixing structure of Li and transition metal ions, as well as the concentrationgradient, over a wide lithiation temperature range. The Ta-doped CS-typecathode retains 92.6 of its initial capacity after 1000 cycles and exhibitsresistance to damage from fast charging. Multifunctional Ta doping in theCS-type cathode provides a simple and all-around solution to maximize theelectrochemical performance of Ni-rich cathodes, providing flexibility in thelithiation process.