Mechanistic Origin for High Structural Stability of Single Crystalline Nickel‐Rich Cathode Materials Via Al and Sm Co‐Doping

• Published in: Advanced functional materials 2023-06, Vol.33 (24), p.n/a
• Main Authors: Li, Jing, Zhong, Wentao, Deng, Qiang, Zhang, Qimeng, Lin, Zhang, Yang, Chenghao
• Format: Article
• Language: English
• Subjects: Cycles; doping; electrochemistry; Electrode materials; lithium‐ion batteries; Materials science; Nickel; nickel‐rich layered oxides; Nonaqueous electrolytes; Single crystals; Structural stability; Surface layers; Synergistic effect; Transition metals
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202300127

Nickel‐rich layered oxides have attracted many attentions for their superior specific capacity and low cost, but they are subjected to fast structural degradation during cycling. Herein, the Al and Sm co‐doped LiNi0.83Co0.07Mn0.10O2 (SC‐NCM‐AS) single‐crystal is demonstrated to overcome their cycling instability issue, and its mechanistic origin for improved structural stability is investigated. It is found that soluble Al ions are homogenously incorporated in the LiNi0.83Co0.07Mn0.10O2 (SC‐NCM) lattice, while Sm ions tends to aggregate in the SC‐NCM outer surface layer. The Li/Ni cation disordering is greatly suppressed through the pillaring effect of stronger AlO bond in SC‐NCM single crystals. Sm‐concentrated outer surface layer can effectively prevent the dissolution of transition metals from SC‐NCM‐AS and inhibit undesirable side reactions induced by the organic electrolyte. This synergistic effect facilitates to suppress the formation of LiOH/Li2CO3 and oxygen vacancies, resulting in released the internal strain, decreased in‐plane transition metals migration and gliding, and eventually preventing formation of nanocracks in SC‐NCM‐AS single crystals upon cycling at high cut‐off voltage. Consequently, Al and Sm co‐doped SC‐NCM exhibits a high specific capacity of 222.4 mAh g−1 and remarkable cycling performance with a capacity retention of 91.1% for 100 cycles. Al‐uniform and Sm‐enriched outer surface layer in SC‐NCM‐AS single crystals is achieved by a combination of solid phase method and calcination process. This synergistic effect enhances structural stability and electrochemistry performance by decreasing irreversible phase transition, gliding and nanocracks. This promising solution can be utilized for developing Ni‐rich single crystal cathode.