The recharging capability of Ni-rich layered cathodes deteriorates rapidly upon cycling, mainly from mechanical instability caused by removing a large amount of Li ions from the host structure.^1,2 The resulting microcracks expose the cathode particle interior to electrolyte attack in addition to undermining the mechanical integrity of the cathode particle. In this study, we develop a Ni-rich layered cathode by combining precursor engineering and a new doping strategy during lithiation that generates minimal microcracking and exhibits substantially improved cycling stability. Excess Al is deliberately introduced into a concentration-gradient (CG) hydroxide precursor, which exhibits a highly oriented geometry in which elongated primary particles are aligned in the radial direction of a spherical secondary particles. The excess Al ions enable the refinement of the primary particles in a controlled manner and the precise tailoring of their morphology and orientation. It is demonstrated that the chemical and microstructural engineering of a Li[Ni_xCo_yAl_1–x–y]O₂ (NCA) cathode starting from its precursor stage produces a unique structure that relieves the detrimental mechanical strain and significantly extends the battery life. Thus, the designed CG Li[Ni_0.86Co_0.1Al_0.04]O₂ retains 86.5% of the initial capacity after 2000 cycles and an unprecedented 78.0% even at a severe operation condition of 45 ^oC. The proposed CG Li[Ni_0.86Co_0.1Al_0.04]O₂ represents a new class of Ni-rich NCA cathodes that can meet the energy density required for next-generation electric vehicles, without compromising the battery life and safety.

References:

[1] S. Watanabe, M. Kinoshita, T. Hosokawa, K. Morigaki, K. Nakura, J. Power Sources 258 (2014) 210–217.

[2] H.-H. Ryu, K.-J. Park, C. S. Yoon, Y.-K. Sun, Chem. Mater. 30 (2018) 1155–1163.