Investigation of Structural Evolution of Li_1.1V₃O₈ by In Situ X-ray Diffraction and Density Functional Theory Calculations

Abstract

is a promising cathode material for Li-ion batteries, because of its high theoretical capacity (362 mAh g −1 ) and good rate performance. In this study, the structural evolution of Li 1.1 V 3 O 8 material during electrochemical dis(charge) processes was investigated using a combination of theoretical calculations and experimental data. Density functional theory (DFT) was used to predict the intermediate structures at various lithiation states, as well as the stability of major phases. In order to validate these predictions, in situ X-ray diffraction (XRD) data was collected operando, allowing for the phase transformations to be monitored under current load and eliminating the possibilities of structural relaxation processes and environmental oxidation. Rietveld refinement was performed to fit the diffraction data with the DFT-derived structures and to analyze the fractions of major phases as a function of dis(charge). The DFT calculations identified three stable states that were validated by the in situ XRD result: a Li-poor αphase (Li 1 ), a Li-rich α-phase (Li 2.5 ), and a β-phase (Li 4 ). The DFT-predicted particle shape based on the surface energy of the (100), (001), and (010) planes rationalized the preferential orientation of Li 1.1 V 3 O 8 particles along the [010] direction in the electrode. Furthermore, the onset and offset of the α → β transition, as well as the phase fractions of α and β determined via in situ XRD, related well with the DFT-derived relative stability of each phase. Thus, by integrating DFT calculations with experimental work, this work provides a thorough understanding of the structural transformations in Li 1.1 V 3 O 8 during electrochemical dis(charge).

Systems-level investigation of aqueous batteries for understanding the benefit of water-in-salt electrolyte by synchrotron nanoimaging

“…The morphology of the LiV 3 O 8 powder is shown in the scanning electron microscopy (SEM) image in fig. S1B, which has the bar-like shape consistent with what is predicted by density functional theory simulation (28) (30).…”

“…The standard spectra, including pristine LiMn 2 O 4 and fully discharged (delithiated) LiMn 2 O 4 , were also measured on TXM at 18-ID, NSLS-II, with the same conditions as 2D XANES images. The reference materials after lithiation/delithiation were prepared through the battery reaction with conventional organic electrolyte (1 M LiPF 6 in EC:DMC = 1:1) in coin cell; the reaction products were previously reported (28,30).…”

“…Third, the material is an excellent choice to achieve high benefit from the TXM experiment. The distinctively different morphology of our synthesized LiV 3 O 8 (28,29) compared to LiMn 2 O 4 and low x-ray absorption are important considerations for the experimental design. These two factors enable the differentiation of the LiMn 2 O 4 compo-nent from the LiV 3 O 8 during the operando TXM study, which is the emphasis of this work.…”

Operando Study of LiV3O8Cathode: Coupling EDXRD Measurements to Simulations

“…1,4 Phase transitions during battery operation are significant because they have implications for electrochemical performance, rate capability, as well as cycle life. Previous studies have interrogated phase change using a variety of methods, both experimental and theoretical: electrochemical, [5][6][7] in-situ 8,9 and ex-situ 10 characterization (SEM, 7,11 XRD 4,5,7,10,11 ), DFT, 9,12 and continuum modeling. 6 Electrochemical measurements are commonly used to investigate battery performance.…”

Lab‐Scale In Situ X‐Ray Diffraction Technique for Different Battery Systems: Designs, Applications, and Perspectives

“…d) Expansion view of selected peak regions of Li 1.1 V 3 O 8 in the charge and discharge process. Reproduced with permission . Copyright 2017, American Chemical Society.…”