Promoting grain growth in Ni-rich single-crystal cathodes for high-performance lithium-ion batteries through Ce doping

Preparing a high-performance Ni-rich single-crystal cathode for Li-ion batteries is challenging. This is because calcination must be performed at a high temperature to achieve particle sintering; however, Ni-rich layered cathode materials are damaged if calcination is performed at very high temperatures. Therefore, reducing the calcination temperature required for the synthesis of single-crystal cathodes can improve the performance of the cathode. In this study, a Ni-rich single-crystal Li[Ni0.9Co0.05Mn0.05]O2 (NCM90) cathode was successfully synthesized at a calcination temperature 50 °C lower than its optimal calcination temperature by introducing a Ce dopant. Depending on their properties, dopants affect the growth and sintering behaviors of cathode materials during calcination. W prevents the formation of single-crystal particles by retarding the growth and sintering of grains, whereas Ce promotes the formation of single-crystal particles. Leveraging this feature of Ce, a Ce-doped NCM90 cathode was synthesized at a calcination temperature of 800 °C; at this temperature, the pristine (undoped) NCM90 cathode remains polycrystalline. The Ce-doped NCM90 cathode delivers an initial capacity of 199.7 mAh g−1 at 0.1 C; moreover, cycled at 0.5 C, it retains 80.5% of its initial capacity after 100 cycles, demonstrating better cycling stability than a pristine NCM90 cathode. The reduced capacity loss of the Ce-doped NCM90 cathode is due to the protraction of the detrimental H2–H3 phase transition, as revealed by differential capacity analysis, and its superior thermal stability, which is attributed to the presence of Ce.