Liu Hao, Hua Weibo, Kunz Sylvia, Bianchini Matteo, Li Hang, Peng Jiali, Lin Jing, Dolotko Oleksandr, Bergfeldt Thomas, Wang Kai, Kübel Christian, Nagel Peter, Schuppler Stefan, Merz Michael, Ying Bixian, Kleiner Karin, Mangold Stefan, Wong Deniz, Baran Volodymyr, Knapp Michael, Ehrenberg Helmut, Indris Sylvio
Institute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen, Germany.
School of Chemical Engineering and Technology, Xi'an Jiaotong University, No.28, West Xianning Road, Xi'an, Shaanxi, China.
Nat Commun. 2024 Nov 18;15(1):9981. doi: 10.1038/s41467-024-54312-z.
The high-voltage oxygen redox activity of Li-rich layered oxides enables additional capacity beyond conventional transition metal (TM) redox contributions and drives the development of positive electrode active materials in secondary Li-based batteries. However, Li-rich layered oxides often face voltage decay during battery operation. In particular, although Li-rich positive electrode active materials with a high nickel content demonstrate improved voltage stability, they suffer from poor discharge capacity. Here, via physicochemical and electrochemical measurements, we investigate the correlation between oxygen redox activity and superstructure units in Li-rich layered oxides, specifically the fractions of LiMn and Ni-stabilized LiNiMn within the TM layer. We prove that an excess of LiNiMn hinders the extraction/insertion of lithium ions during Li metal coin cell charging/discharging, resulting in incomplete oxygen redox activity at a cell potential of about 3.3 V. We also demonstrate that lithium content adjustment could be a beneficial approach to tailor the superstructure units. Indeed, we report an improved oxygen redox reversibility for an optimized Li-rich layered oxide with fewer LiNiMn units.
富锂层状氧化物的高压氧氧化还原活性能够提供超出传统过渡金属（TM）氧化还原贡献的额外容量，并推动了锂基二次电池正极活性材料的发展。然而，富锂层状氧化物在电池运行过程中常常面临电压衰减问题。特别是，尽管高镍含量的富锂正极活性材料表现出更好的电压稳定性，但它们的放电容量较差。在此，通过物理化学和电化学测量，我们研究了富锂层状氧化物中氧氧化还原活性与超结构单元之间的相关性，特别是TM层中LiMn和Ni稳定的LiNiMn的比例。我们证明，过量的LiNiMn会在锂金属硬币电池充电/放电过程中阻碍锂离子的脱出/嵌入，导致在约3.3 V的电池电位下氧氧化还原活性不完全。我们还表明，调整锂含量可能是一种有益的方法来定制超结构单元。事实上，我们报道了一种具有较少LiNiMn单元的优化富锂层状氧化物具有改善的氧氧化还原可逆性。
