Figure 1.

Ex-situ 17O MAS NMR spectra of LixCoO2 recorded at 14.1 T and 24 kHz MAS. The magnification factors are listed on the left side of each spectrum. (Reproduced from Ref.[17] with permission from The Royal Society of Chemistry) (color on line)

Figure 2.

In-situ EPR spectra of the NaCrO2/Na cell cycled at 10 mA·g-1 between (A) 2.2 ~ 3.6 V and (C) 2.2 ~ 4.5 V. The intensive Na signal in the range of 331 ~ 335 mT is truncated for clarity. (B, D) Corresponding voltage profiles (top) and EPR intensities (bottom) as a function of time. EPR intensities are calculated using half of the peak-to-peak intensity. (Reproduced from Ref.[21] with permission from American Chemical Society) (color on line)

Figure 3.

In-situ EPR images of the in-situ cell charged to 4.15 V on (A) the ZY plane and (B) the XY plane. Color bars on the right side show the normalized intensity of spin concentrations. (C) Digital photos of the cell used in EPR imaging. The sizes of the cathode and the separator are marked in blue and red, respectively. (D) Scheme for the orientation of the cell in the image coordinates. (Reproduced from Ref.[21] with permission from American Chemical Society) (color on line)

Figure 4.

(A, B) Ex-situ X-band EPR spectra of Li3V2(PO4)3 electrode materials cycled at different states-of-charge at 2 K. Cha denotes “charging” and Dis denotes “discharging”. (Reproduced from Ref.[22] with permission from Elsevier publisher) (color on line)

Figure 5.

(A) X-band EPR spectra for lithiation/delithiation of the r-CoHNta electrode materials cycled to different states-of-charge recorded at 2 K; (B) The corresponding electrochemical profile cycled at a current rate of 100 mA·g-1. (Reproduced from Ref.[24] with permission from Elsevier publisher) (color on line)

Figure 6.

(A) 23Na and (B) 31P MAS ssNMR spectra of NVOPF, NV3.8OPF, and NV3.6OPF. Spinning sidebands are marked with asterisks in (A) and (B). (C) Continuous-wave X-band EPR spectra recorded at 2 K of NVOPF, NV3.8OPF, and NV3.6OPF. (D) An enlarged EPR spectrum of NV3.8OPF. (Reproduced with permission from ref.[28], Copyright 2018, The Royal Society of Chemistry) (color on line)

Figure 7.

(A) 23Na MAS ssNMR spectra of the NV3.8POF electrodes under various SOC (states-of-charge) values during charge process; (B) Parallel-mode EPR spectra of cycled NV3.8POF under representative SOC. (Reprinted with permission from ref.[29], Copyright 2018, American Chemical Society) (color on line)

Figure 8.

Isotropic slices of 7Li pj-MATPASS NMR spectra for (A, C) pristine NLMO, and NLMTO-0.1, and (B, D) fully discharged NLMO and NLMTO-0.1 electrodes. The resonances within the blue-marked region correspond to the Li sites in the Na layer, while the resonances within the yellow-marked region correspond to the Li sites within the TMO2 layer. (Reproduced from Ref.[32] with permission from American Chemical Society) (color on line)

Figure 9.

(A) Fine scanning vertical-mode EPR spectra of cycled NLMO under the representative SoC; The O2n- EPR signals possess various hyperfine patterns. (B) Fine scanning vertical-mode EPR spectra of cycled NLMTO-0.1. (Reproduced from Ref.[32] with permission from American Chemical Society) (color on line)

Figure 10.

Ex-situ perpendicular-mode CW-EPR spectra of LTMO during the processes of (A) Mn oxidation, (B) O oxidation, and (C) reduction. These EPR measurements were performed at 1.8 K. Signal intensities are normalized based on the mass of each material scraped from the electrodes. The sharp signals centered at ~ 345 mT (g ~ 2.0) stem from the delocalized electrons in the conductive carbon black, which can be regarded as an external reference although it may cover up similar signals. (Reproduced from Ref.[34] with permission from The Royal Society of Chemistry) (color on line)

Table 1

Summary of important magnetic resonance techniques and their applications