Analysis of LIB cathodes by ultra-fast MAS solid state NMR

　NMR has been widely used  in research and development of  lithium ion battery (LIB)  because it is  able to observe lithium ions directly and thus is extremely useful for characterizing local structure  of  materials for LIB.
　Two types of lithium nuclears, ⁶Li and ⁷Li,  are NMR observable. ⁷Li has the much higher sensitivity than ⁶Li because of  higher natural abundance and gyromagnetic moment. However,  a solid state NMR analysis of  cathode materials using ⁷Li by conventional MAS frequency ( - 20kHz) has been difficult due to a series of  spinning side band (SSB) originated from paramagnetic interaction.
　The ultra-fast MAS probes (1mm and 0.75mm) give high resolution and less SSB ⁷Li spectra. These are available for analyses of  degradation behavior  of cathode materials.

Ultra-fast MAS

• 1mm (-80kHz) and 0.75mm (-110kHz)  probes
• analysis of microscale sample
• less SSB ⁷Li spectra

Sampling of a cathode material

Sampling from  a cathode sheet.

1mm sample tube

MAS frequency dependence of ⁷Li  spectra

Spectral change before and after cycles

Acknowledgment

Samples before and after cycles were kindly provided by Prof. Y.Oka (Univ.Hyogo)