Analysis of LIB cathodes by using MATPASS with ultra-fast MAS

NMR is extremely useful for characterizing local structure of materials for lithium ion battery (LIB) because it is able to observe lithium ions directly . However, a solid state NMR analysis of cathode materials using ⁷Li by conventional MAS frequency (- 20 kHz) has been difficult due to a series of spinning side band (SSB) originated from paramagnetic shift anisotropy.
The ultra-fast MAS probes (1mm and 0.75mm) give high resolution and less SSB ⁷Li spectra as shown in an application note NM-140020. However, for many of LIB cathode materials the ultra fast MAS alone may not be sufficient to obtain spectra without effect of SSBs. An excellent solution to avoid the problem is MATPASS (Magic Angle Turning – Phase Adjusted Spinning Sideband) technique developed by Hung et al. ¹ The experiment allows SSBs free ⁷Li spectra of paramagnetic cathode materials. This technique is available for moderate speed MAS probes, but the ultra fast MAS probe still has great advantage because it allows wide range excitation leading to quantitative spectrum and experiment with small sample amount.

• SSB free ⁷Li spectrum
• Wide range excitation
• Small sample amount

1mm sample tube

1. I. Hung et al., J. Am. Chem.Soc. 2012, 134, 1898−1901

Deterioration analysis of LiMn₂O₄ by ⁷Li MATPASS spectra

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

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