Solid-State NMR Strategies for the Structural Investigation of Carbon-Based Anode Materials

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• 作者：Sophia Hayes ; Leo van Wü ; llen ; Hellmut Eckert ; William R. Even ; Robert W. Crocker ; and Zhengming Zhang
• 刊名：Chemistry of Materials
• 出版年：1997
• 出版时间：April 1997
• 年：1997
• 卷：9
• 期：4
• 页码：901 - 911
• 全文大小：412K
• 年卷期：v.9,no.4(April 1997)
• ISSN：1520-5002

文摘

Multinuclear solid-state NMR spectroscopy is a well-suitedtechnique for structural analysisof amorphous carbon-based anode materials generated from pyrolysis ofpoly(methacrylonitrile/divinylbenzene) copolymers. Results are presented for theuntreated polymericprecursor, the oxidatively stabilized material, and amorphous carbonsprepared by high-temperature pyrolysis. In addition, structural effects of silicondopants and lithiumintercalants are studied. The structural changes occurring duringthe processes of oxidativestabilization and carbonization up to 700 C are effectivelymonitored by ¹³C and ¹⁵N cross-polarization/magic angle spinning methods. The peak assignments areassisted by shortcontact time and dipolar dephasing experiments. For carbonsprepared at higher pyrolysistemperatures this technique is limited by the low structural protoncontent. For suchmaterials, the ¹H chemical shifts of sorbed water moleculesare found to be linearly correlatedwith the pyrolysis temperature. This effect is attributed tosurface ordering phenomena.²⁹Si CPMAS spectra of carbons prepared withtetravinylsilane comonomers indicate thatthe silicon component is oxidized during the stabilization process.⁷Li MAS NMR is wellsuited to differentiate between electrochemically relevant intercalatedspecies and otherspecies that are unable to participate in the intercalation due toparasitic processes. Forthe intercalated species, a linear correlation of the⁷Li chemical shift with the chargingstateof the carbon is observed.