Direct Observation of Lattice Aluminum Environments in Li Ion Cathodes LiNi1–y–zCoyAlzO2 and Al-Doped LiNixMnyCozO2 via 27Al MAS NMR Spectroscopy

详细信息    查看全文

• 作者：Fulya Dogan ; John T. Vaughey ; Hakim Iddir ; Baris Key
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：July 6, 2016
• 年：2016
• 卷：8
• 期：26
• 页码：16708-16717
• 全文大小：585K
• 年卷期：0
• ISSN：1944-8252

文摘

Direct observations of local lattice aluminum environments have been a major challenge for aluminum-bearing Li ion battery materials, such as LiNi_1–y–zCo_yAl_zO₂ (NCA) and aluminum-doped LiNi_xMn_yCo_zO₂ (NMC). ²⁷Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy is the only structural probe currently available that can qualitatively and quantitatively characterize lattice and nonlattice (i.e., surface, coatings, segregation, secondary phase etc.) aluminum coordination and provide information that helps discern its effect in the lattice. In the present study, we use NMR to gain new insights into transition metal (TM)–O–Al coordination and evolution of lattice aluminum sites upon cycling. With the aid of first-principles DFT calculations, we show direct evidence of lattice Al sites, nonpreferential Ni/Co–O–Al ordering in NCA, and the lack of bulk lattice aluminum in aluminum-“doped” NMC. Aluminum coordination of the paramagnetic (lattice) and diamagnetic (nonlattice) nature is investigated for Al-doped NMC and NCA. For the latter, the evolution of the lattice site(s) upon cycling is also studied. A clear reordering of lattice aluminum environments due to nickel migration is observed in NCA upon extended cycling.