High-performance Ni-rich Li[Ni0.9–xCo0.1Alx]O2 cathodes via multi-stage microstructural tailoring from hydroxide precursor to the lithiated oxide†
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. Through multi-stage microstructural tailoring, which refers to optimal engineering of the precursor microstructure and then deliberately over-doping of Al during the lithiation stage to preserve the needle-like morphology of the precursor, we optimize the primary particle morphology of the cathode. It is demonstrated that the chemical and microstructural engineering of a Li[Ni0.9–xCo0.1Alx]O2 cathode starting from its precursor stage produces a unique structure that relieves the detrimental mechanical strain and significantly extends the battery life. Excess Al-doped Li[Ni0.86Co0.1Al0.04]O2 with the compositional partitioning of Ni produces a highly aligned microstructure in which constituent primary particles are refined to a sub-micrometer scale. Thus, the designed Li[Ni0.86Co0.1Al0.04]O2 retains 86.5% of the initial capacity after 2000 cycles and an unprecedented 78.0% even at a severe operation condition of 45 °C. The proposed Li[Ni0.86Co0.1Al0.04]O2 represents a new class of Ni-rich Li[NixCoyAl1–x–y]O2 cathodes that can meet the energy density required for next-generation electric vehicles, without compromising the battery life and safety.