Nuclear Magnetic Resonance Studies of Lithium-Ion Battery Materials
- PDF / 879,172 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 61 Downloads / 254 Views
Nuclear Magnetic
Resonance Studies of Lithium-Ion Battery Materials
Clare P. Grey and Steve G. Greenbaum Abstract Solid-state nuclear magnetic resonance (NMR) spectroscopy has been employed to characterize a variety of phenomena that are central to the functioning of lithium and lithium-ion batteries. These include Li insertion and de-insertion mechanisms in carbonaceous and other anode materials and in transition-metal oxide cathodes, and ion-transport mechanisms in polymer and gel electrolytes. Investigations carried out over the last several years by the authors and other groups are reviewed in this article. Results for lithium manganese oxide spinel cathodes, carbon-based and SnO anodes, and polymer and gel electrolytes are discussed. Keywords: diffusion, energy-storage materials, ionic conductors, ion–solid interactions, nuclear magnetic resonance, rechargeable lithium batteries, structure.
Introduction Structural studies of materials utilized in lithium battery technology are often hampered by the lack of long-range order found only in well-defined crystalline phases. Powder x-ray diffraction, while being an indispensable technique for the characterization of electrode materials, yields only structural parameters that have been averaged over hundreds of lattice sites. On the other hand, nuclear magnetic resonance (NMR) spectroscopy is one of a few very powerful methods for probing the immediate environments of ions such as Li in the solid state, especially in disordered materials. The NMR spectrum is sensitive to a number of physical parameters that are directly related to the efficacy of the working cell. These include Li-ion mobility, electronic conductivity, and the changes of valence or electronic structure of the cations that are involved in the redox processes. Furthermore, NMR is element-specific (i.e., nuclear-specific) and may be used to directly examine the species that are involved in the working battery. As a probe of the immediate environment of the nucleus under investigation, NMR is an ideal
MRS BULLETIN/AUGUST 2002
method for investigating the small changes in local structure that occur on doping, or for elucidating lithium insertion and extraction mechanisms. An important feature of NMR is that the integrated spectroscopic signal is proportional to the number of resonant NMR nuclei in the sample. Thus, NMR analysis can be used to ascertain the relative phase content of a material in cases where individual spectral contributions can be resolved. This review deals with lithium and lithium-ion battery materials, including carbonaceous and metal oxide anodes, transition-metal oxide cathodes, and both polymer and gel electrolytes. Space limitations do not allow an exhaustive survey of all Li battery materials, but the main intent of this review is to illustrate the power and versatility of NMR spectroscopy to address important materials issues.
Background The NMR-active nuclei can be divided into two types, the spin-1/2 nuclei such as 13 C and 1H and the quadrupolar nuclei (spin 1/2) such
Data Loading...
