XXV General Assembly and Congress of the
International Union of Crystallography - IUCr 2021
August 14 - 22, 2021 | Prague, Czech Republic
Conference Agenda
Overview and details of the sessions of this conference. Please select a date or location to show only sessions at that day or location. Please select a single session for detailed view (with abstracts and downloads if available).
|
Session Overview |
Session | ||
SMS-6: Spectroscopy applied to electrochemistry: operando studies
Invited: Moniek Tromp (The Netherlands), Mahalingam Balasubramanian (USA) | ||
Session Abstract | ||
Ideally, dynamic processes ruling electrochemical energy storage are studied under operating conditions. In addition, research into new high-performance electrode materials requires a better understanding of the electrochemical reaction mechanisms that take place during the charge/discharge processes. Operando experiments are expected to provide a realistic representation of the reaction behavior found under normal operating conditions. The aim of this MS is to show the applications of spectroscopic methods in operando conditions for the best design of materials for energy storage materials. | ||
Introduction | ||
Presentations | ||
2:45pm - 2:50pm
Introduction to session 2:50pm - 3:20pm
Operando X-ray Absorption Spectroscopy probing Dynamic Processes in Batteries University of Groningen, Groningen, Netherlands, The An important element in the reduction of CO2 is the change of vehicles with internal combustion engines to electric battery powered vehicles. The as such produced renewable energy can be used for individual mobility as well as for a temporary intermediate storage of excess energy. A viable electric mobility concept requires however stable cycle batteries with high specific energy (minimising weight, maximising driving range). Li ion batteries are widely used in applications such as mobile phones and laptops, and will likely be key to future electromobility. An alternative promising battery is the lithium sulfur battery with a potential twofold energy density increase. The requirements for such batteries present major challenges; e.g. energy capacity, deactivation/stability and safety. A detailed understanding of the charge, discharge and deactivation mechanisms are thus required, preferably quantitative and spatially resolved. X-ray absorption spectroscopy (XAS) is a characterisation technique which provides detailed electronic and structural information on the material under investigation, in a time- and spatially resolved manner. Here, I will explain the strengths and limitations of XAS for battery research. A novel operando XAS cell design will be described [1], including the challenges to perform reliable experiments (electrochemically and spectroscopically). The cell allows time and spatial resolved XAS, providing insights in the type, location and reversibility of the intermediates formed in electrodes and electrolyte separately. Obtained insights in cycling and deactiviation mechanisms for the different battery types will be discussed [1-6] and future research directions described. [1] Y. Gorlin, A. Siebel, M. Piana, T. Huthwelker, H. Jha, G. Monsch, F. Kraus, H.A. Gasteiger, M. Tromp, J. Electrochem. Soc. 162(7): A1146-A1155, 2015. [2] Y. Gorlin, M. U. M. Patel, A. Freiberg, Q. He, M. Piana, M. Tromp, H. A. Gasteiger, J. Electrochem. Soc. 2016, 163(6), A930-A939. [3] J. Wandt, A. Freiberg, R. Thomas, Y. Gorlin, A. Siebel, R. Jung, H. A. Gasteiger, M. Tromp, J. Mater. Chem. A 2016, 4, 18300-18305. [4] A. T. S. Freiberg, A. Siebel, A. Berger, S. M. Webb, Y. Gorlin, H. A. Gasteiger, M. Tromp, J. Phys. Chem. C 2018, 122, 10, 5303-5316. [5] A. Berger, A. T. S. Freiberg, R. J. Thomas, M. U. M. Patel, M. Tromp, H. Gasteiger, Y. Gorlin, J. Electrochem. Soc. 2018, 165(7), A1288-A1296. [6] R. Jung, F. Linsenmann, R. J. Thomas, J. Wandt, S. Solchenbach, F. Maglia, C. Stinner, H. A. Gasteiger, M. Tromp, J. Electrochem. Soc. 2019, 166(2): A378-A389. External Resource: https://www.xray.cz/iucrv/vidp.asp?id=715
3:20pm - 3:50pm
Operando diagnostics of cathode materials based on novel sodium iron titanites 1Smart Materials Research Institute, Southern Federal University, Rostov-on-Don, Russian Federation; 2Department of Chemistry, Southern Federal University, Rostov-on-Don, Russian Federation A set of sodium iron titanite samples with general formula NaxFe+2x/2Ti2–x/2O4 was prepared using solid-state synthesis in an inert atmosphere to test for application as cathode materials for Na-ion batteries. These materials have several advantages over analogues with Fe3+, demonstrating better sodium ion conductivity and higher Na+ ions capacity without phase transition or destruction of the structure. [1] In the course of the investigation, several compositions of a new compound were obtained with NSIT-like structure type similar to Na0.9Fe3+0.9Ti1.1O4. Among them, composition with x = 0.9 was selected due to its electrochemical performance and structural peculiarity. From the crystallographic point of view, formation of phases in NaxFe+2x/2Ti2–x/2O4 system with Na0.9Fe3+0.9Ti1.1O4 structure (having Fe3+ ions mixed with Ti4+ ions) is rather unusual due to different radii of mixing ions (Fe2+ = 0.92 Å, Fe3+ = 0.785 Å, Ti+4 = 0.745 Å (CN=6) [2]). The Na0.9Fe3+0.9Ti1.1O4 was further studied by operando XANES spectroscopy. The sample was placed as a cathode inside custom electrochemical cell with glassy carbon X-Ray transparent windows. Li foil was used as anode and 1M LiPF6 in 1:1 EC:DMC commercial solution (Sigma) was used as electrolyte. The cell was cycled in 1.6 to 4.5 V range with current of C/20. Operando Fe K-edge XANES spectra were measured with the R-XAS Looper (Rigaku, Japan) laboratory X-Ray absorption spectrometer. In total 200 spectra were collected for NaxFe+2x/2Ti2–x/2O4 sample with x = 0.9 during 10 consecutive cycles, which were further analyzed by PCA to extract spectra of phases participating the electrochemical process and corresponding phase content diagrams. 2 components were successfully extracted (fig. 1). Component corresponding to a Fe2+ phase shows good agreement with FeTiO3 reference in terms of absorption edge position and overall profile of the spectrum. On the other hand, agreement with the spectrum of as-prepared sample is far from decent. Component corresponding to a Fe3+ phase shows good agreements with a reference compound (reference sample, fully oxidized in air). Comparison with theoretical spectra for various structural models have shown decent agreement of Fe2+ phase with the spectrum of freudenbergite. Fig. 2 shows the cell potential and phase concentrations from PCA as a function of time. One can clearly see the decrease in Fe2+/Fe3+ conversion rate during first 3 cycles, after that the rate remains stable and conversion is highly reversible. This decrease in conversion rate, as well as lack of agreement between Fe2+ phase from PCA and as prepared sample, might be accounted by electrochemical substitution of Na with Li that takes place during cycling in Li-based cell, which causes the change in local atomic and electronic structure of material, possibly leading to partially blocked or collapsed ion transfer channels. The degree and details of such substitution are subject for study by operando XRD and Mössbauer spectroscopy. [1] Rajagopalan et al., (2017) Adv. Mater. 29 [2] Shannon, R.D. (1976), Acta Crystallogr. Sect. A 32, 751-767 Authors would like to acknowledge the financial support of Russian Foundation for Basic Research in the framework of grant 20-32-70227 |