NSRRC Activity Report 2023

Energy Science 065 Fig. 3 , the conventional Fd3m-type LiMn 2 O 4 and typical spinel LiNi 0.5 Mn 1.5 O 4 are converted to Li-rich Li 2 MnO 4 and Li 2 Ni 0.5 Mn 1.5 O 4 by applying contact pre-lithium strategies. This phase transition was demonstrated to be reversible through ex-situ XAS of Mn and Ni during the different charge/discharge plateaus. 4,5 Solid electrolytes (SEs) are vital to ensure all-solid-state batteries (ASSBs) with improved safety, long cyclability, and feasibility at different temperatures in lithium batteries. The teams of Xue-liang Sun (University of Western Ontario, Canada) and Lo-Yueh Chang (NSRRC) reported a novel amorphous SE x Li 2 O–MCl y (M = Ta or Hf 0.8≤ x ≤ 2, y = 5 or 4), obtaining one of the highest values among all the reported amorphous SEs. To assess the local environment of the ASSBs, the absorption edge of Ta was measured as shown in Fig. 4 in next page. 6 The absorption edge energy of the Ta L 3 -edge was between that of Ta 2 O 5 and TaCl 5 , indicating oxidation of TaCl 5 when LiO 2 was added. To further explain the coordination of Ta in x Li 2 O-TaCl 5 , Fourier transform (FT) and wavelet transform (WT) EXAFS analyses were conducted. Based on these results, Ta in each x Li 2 O–TaCl 5 amorphous SE was found to be coordinated by O and Cl. When adding more LiO 2 , the signal of Ta–O increased in intensity. The local environment of the Ta-based amorphous SEs was identified as [TaCl 5-a O a ] a- (1 ≤ a < 5) trigonal bipyramidal, displaying an abundance of terminal chlorines with weak direct interactions with Li ions. Bridging oxygens, serving as joints in the networks of amorphous SEs, can induce a wide range of distortions in Li sites. Fast Li-ion conduction in x Li 2 O–TaCl 5 amorphous SEs may benefit from a mixed anion chemistry. The optimized 1.6 Li 2 O–TaCl 5 and 1.5 LiO 2 –HfCl 4 amorphous SEs displayed good cathode compatibility with conventional layered oxide cathode materials (NCM83 and LCO). Fig. 2 : (a) Charge/discharge profile showing the voltage positions for the ex-situ experiments. (b) Ex-situ Fe K-edge XANES spectra of NaMnFe–PB electrodes with references. The insets highlight the pre-edge region and principal maximum of the charged and discharged electrodes. (c) Ex-situ Mn K-edge XANES spectra with references. Insets show the magnified peaks indicative of the change in oxidation state of the transition metal during cycling. [Reproduced from Ref. 3] Fig. 3 : (a) Mn K-edge XANES spectra, (b) Ni K-edge XANES spectra, and (c) edge positions of the Mn K-edge and Ni K-edge at different voltage states. (e) XANES spectra, and (d) edge positions at the Mn K-edge of the LMO electrodes at different voltage states. [Reproduced from Refs. 4 and 5]