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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >~7Li Solid-State Nuclear Magnetic Resonance as a Probe of Lithium Species in Microporous Carbon Anodes
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~7Li Solid-State Nuclear Magnetic Resonance as a Probe of Lithium Species in Microporous Carbon Anodes

机译：〜7Li固态核磁共振作为微孔碳阳极中锂物种的探针。

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摘要

Electrochemical insertion of lithium into pyrolyzed amorphous carbons prepared from polymeric precursors of methacrylonitrile and divinylbenzene has been investigated by ~7Li variable temperature static and magic angle spinning (MAS) NMR. This method is able to characterize the chemical inventory of lithium, differentiating between reversible species that are truly inserted into the carbon and irreversible species that are lost to traps and parasitic processes. Furthermore, large chemical shift effects indicate that the structural and electronic properties of the inserted reversible lithium species are sensitively dependent on the extent of loading. At loading levels ≤90% relative capacity, the trend is monotonic, whereas in more highly charged samples, two types of electrochemically relevant sites are observed, distinguishable from one another only at lower temperatures. At higher temperatures, dynamic exchange effects between them are evident on the NMR time scale. In the initially prepared state, these highly charged materials contain regular intercalated lithium sites as well as clusters of atomic lithium species dispersed in the amorphous matrix. The cluster sites are depopulated with time, a process that can be accelerated by heating.
机译：已经通过〜7Li可变温度静态和魔角旋转（MAS）NMR研究了将锂电化学插入由甲基丙烯腈和二乙烯基苯的聚合前体制备的热解无定形碳中。该方法能够表征锂的化学存量，从而区分出真正插入碳中的可逆物质和因陷阱和寄生过程而损失的不可逆物质。此外，大的化学位移效应表明，插入的可逆锂物质的结构和电子性质敏感地取决于负载的程度。在相对水平≤90％的负载水平下，趋势是单调的，而在带电更高的样品中，观察到两种类型的电化学相关位点，只有在较低温度下才能彼此区分。在较高的温度下，它们之间的动态交换效应在NMR时间标度上很明显。在初始制备状态下，这些带高电荷的材料包含规则的嵌入锂位以及分散在无定形基质中的原子锂物种簇。随着时间的流逝，集群的地点越来越少，这个过程可以通过加热来加速。

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