Precise regulation of particle orientation for Ni-rich cathodes with ultra-long cycle life

Abstract

Microstructure engineering of Ni-rich layered cathodes is crucial for mitigating mechanical degradation induced by anisotropic strain during Li-ion (de)intercalation. While the orientation of primary particles has been extensively controlled using high-valence dopants during calcination, the critical role of the hydroxide precursor in synthesizing radially aligned Ni-rich cathodes, along with the requirements for precursor characteristics, has been overlooked. Here, we present a method for precisely tailoring Ni-rich cathodes with superior radially aligned microstructure by combining strategic precipitation regulation and calcination tuning. Through stepwise control of ammonia concentration and pH during precipitation, elongated primary particles with appropriate size along [001] are promoted, facilitating the formation of radially aligned particles in the precursor. This approach enables the synthesis of LiNi0.94Co0.02Mn0.04O2 cathodes with exceptional radially aligned microstructure across a wide range of calcination temperature. Benefiting from the size-refined and radially aligned particles, as well as high crystallinity, the cathode derived from the tailored hydroxide precursor exhibit a high discharge capacity of 230 mAh g−1 at 0.05 C and 186 mAh g−1 at 5 C, with superb capacity retention of 95.6 % after 100 cycles at 1 C and 25 ℃ in half cell and 93.2 % after 1000 cycles at 1 C and 30 ℃ in full cell.