Expanded Solid-Solution Behavior and Charge-Discharge Asymmetry in Naxcro2 Na-Ion Battery Electrodes
Sodium chromium oxide, NaCrO2, has received significant attention as positive electrode (cathode) for Na-ion batteries mainly due the high capacity retention of the material. In this paper, we use operando powder X-ray diffraction to investigate the structural evolution of O3-NaCrO2 during Na-ion extraction and insertion with use of both liquid and solid-state electrolytes. This reveals a previously overlooked phase transition, causing formation of an unexplored O’3-NaxCrO2 intermediate during Na-ion extraction (charge). The phase transitions within the electrode are investigated by sequential Rietveld refinement and distortion analysis, which shows that the discovered O’3-NaxCrO2 intermediate accommodates the increasing interlayer repulsion and in-plane contraction with less distortion of the [NaO6]-polyhedra as compared to the other observed phases. Our structural findings are corroborated by analysis of the Na-ion diffusion coefficients through galvanostatic intermittent titration. Furthermore, the operando PXRD reveals substantial charge-discharge asymmetry with a significant preference for solid-solution and two-phase behavior during charge (Na-extraction) and discharge (Na-insertion), respectively
Year of publication: |
[2022]
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Authors: | Jakobsen, Christian Lund ; Brighi, Matteo ; Andersen, Bettina Pilgaard ; Ducrest, Gaëtan ; Cerny, Radovan ; Ravnsbæk, Dorthe B. Bomholdt |
Publisher: |
[S.l.] : SSRN |
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