Relieving Stress Concentration through Anion–Cation Codoping toward Highly Stable Nickel-Rich Cathode

• Published in: ACS nano 2023-10, Vol.17 (20), p.20621-20633
• Main Authors: Zhou, Yu, Zhang, Hanwei, Wang, Yinglei, Wan, Tao, Guan, Peiyuan, Zhou, Xindong, Wang, Xuri, Chen, Yichang, Shi, Hancheng, Dou, Aichun, Su, Mingru, Guo, Ruiqiang, Liu, Yunjian, Dai, Liming, Chu, Dewei
• Format: Article
• Language: English
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/acsnano.3c07655

Nickel-rich LiNi0.8Co0.15Al0.015O2 (NCA) with excellent energy density is considered one of the most promising cathodes for lithium-ion batteries. Nevertheless, the stress concentration caused by Li+/Ni2+ mixing and oxygen vacancies leads to the structural collapse and obvious capacity degradation of NCA. Herein, a facile codoping of anion (F–)-cation (Mg2+) strategy is proposed to address these problems. Benefiting from the synergistic effect of F– and Mg2+, the codoped material exhibits alleviated Li+/Ni2+ mixing and demonstrates enhanced electrochemical performance at high voltage (≥4.5 V), outperformed the pristine and F–/Mg2+ single-doped counterparts. Combined experimental and theoretical studies reveal that Mg2+ and F– codoping decreases the Li+ diffusion energy barrier and enhances the Li+ transport kinetics. In particular, the codoping synergistically suppresses the Li+/Ni2+ mixing and lattice oxygen escape, and alleviates the stress–strain accumulation, thereby inhibiting crack propagation and improving the electrochemical performance of the NCA. As a consequence, the designed Li0.99Mg0.01Ni0.8Co0.15Al0.05O0.98F0.02 (Mg1+F2) demonstrates a much higher capacity retention of 82.65% than NCA (55.69%) even after 200 cycles at 2.8–4.5 V under 1 C. Furthermore, the capacity retention rate of the Mg1+F2||graphite pouch cell after 500 cycles is 89.6% compared to that of the NCA (only 79.4%).