1. Spectroscopic insights into the electrochemical mechanism of rechargeable calcium/sulfur batteriesAntonio Scafuri, Romain Berthelot, Klemen Pirnat, Alen Vižintin, Jan Bitenc, Giuliana Aquilanti, Dominique Foix, Rémi Dedryvère, Iztok Arčon, Robert Dominko, Lorenzo Stievano, 2020, original scientific article Abstract: Calcium batteries represent a promising alternative to lithium metal systems. The combination of the low redox potential and low cost and the energy-dense calcium anode (2073 mAh/cm3, similar to 2044 mAh/cm3 for Li) with appropriate low-cost cathode materials such as sulfur could produce a game-changing technology in several fields of applications. In this work, we present the reversible activity of a proof-of-concept Ca/S battery at room temperature, characterized by a surprising medium-term cycling stability with low polarization, promoted by the use of a simple positive electrode made of sulfur supported on an activated carbon cloth scaffold, and a state-of-the-art fluorinated alkoxyborate-based electrolyte. Insights into the electrochemical mechanism governing the chemistry of the Ca/S system were obtained for the first time by combining X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. The mechanism implies the formation of different types of soluble polysulfide species during both charge and discharge at room temperature, and the formation of solid CaS at the end of discharge. The reversible electrochemical activity is proven by the reformation of elemental sulfur at the end of the following charge. These promising results open the way to the comprehension of emerging Ca/S systems, which may represent a valid alternative to Mg/S and Li/S batteries. Keywords: Calcium/Sulfur Batteries
EXAFS, XANES Published in RUNG: 17.10.2020; Views: 3532; Downloads: 0 This document has many files! More... |
2. Polysulfides formation in different electrolytes from the perspective of X-ray absorption spectroscopyRobert Dominko, Alen Vižintin, Giuliana Aquilanti, Lorenzo Stievano, Maria Joseph Helen, Anji Reddy Munnangi, Maximilian Fichtner, Iztok Arčon, 2018, original scientific article Abstract: Li-S batteries are promising energy storage technology for the future, however there two major problems remained which need to be
solved before successful commercialization. Capacity fading due to polysulfide shuttle and corrosion of lithium metal are directly
connected with the type and quantity of electrolyte used in the cells. Several recent works show dependence of the electrochemical
behavior of Li-S batteries on type of the electrolyte. In this work we compare and discuss a discharge mechanism of sulfur conversion
in three different electrolytes based on measurements with sulfur K-edge XAS. The sulfur conversion mechanism in the ether based
electrolytes, the most studied type of solvents in the Li-S batteries, which are enabling high solubility of polysulfides are compared
with the fluorinated ether based electrolytes with a reduced polysulfide solubility and in carbonate based electrolytes with the sulfur
confined into a ultramicroporous carbon. In all three cases the sulfur reduction proceeds through polysulfide intermediate phases
with a difference on the type polysulfides detected at different steps of discharge. Keywords: Li-S batteries, operando sulphur K-edge XANES, EXAFS, Li-polysulphides Published in RUNG: 01.06.2018; Views: 4184; Downloads: 0 This document has many files! More... |
3. The mechanism of Li2S activation in lithium-sulfur batteries: Can we avoid the polysulfide formation?Alen Vižintin, Laurent Chabanne, Elena Tchernychova, Iztok Arčon, Lorenzo Stievano, Giuliana Aquilanti, Markus Antonietti, Tim-Patric Fellinger, Robert Dominko, 2017, original scientific article Abstract: Electrochemical reactions in the LieS batteries are considered as a multistep reaction process with at least
2e3 equilibrium states. Here we report a possibility of having a conversion of Li2S into sulfur without
detectible formation of polysulfides. That was confirmed by using a novel material system consisting of
carbon coated Li2S particles prepared by carbothermal reduction of Li2SO4. Two independent in operando
measurements showed direct oxidation of Li2S into sulfur for this system, with almost negligible formation
of polysulfides at potentials above 2.5 V vs. Li/Liþ. Our results link the diversity of first charge profiles in the
literature to the Li2S oxidation mechanism and show the importance of ionic wiring within the material.
Furthermore, we demonstrate that the Li2S oxidation mechanism depends on the relative amount of
soluble sulfur in the electrolyte. By controlling the type and the amount of electrolyte within the encapsulating
carbon shell, it is thereby possible to control the reaction mechanism of Li2S activation. Keywords: Lithium-sulfur batteries
Li2S active material
XAS
UV/Vis spectroscopy
Li2S activation Published in RUNG: 03.03.2017; Views: 5940; Downloads: 0 This document has many files! More... |
4. Operando characterization of batteries using x-ray absorption spectroscopy: advances at the beamline XAFS at synchrotron ElettraGiuliana Aquilanti, marco Giorgetti, Robert Dominko, Lorenzo Stievano, Iztok Arčon, Nicola Novello, Luca Ivanc Olivieri, 2017, original scientific article Abstract: X-ray absorption spectroscopy is a synchrotron radiation based technique that is able to
provide information on both local structure and electronic properties in a chemically selective
manner. It can be used to characterize the dynamic processes that govern the electrochemical
energy storage in batteries, and to shed light on the redox chemistry and changes in structure
during galvanostatic cycling to design cathode materials with improved properties. Operando
XAS studies have been performed at beamline XAFS at Elettra on different systems. For
Li-ion batteries, a multiedge approach revealed the role of the different cathode components
during the charge and discharge of the battery. In addition, Li-S batteries for automotive
applications were studied. Operando sulfur K-edge XANES and EXAFS analysis was used to
characterize the redox chemistry of sulfur, and to relate the electrochemical mechanism to its
local structure. Keywords: operando studies, x-ray absorption spectroscopy, Li-ion batteries, Li-S batteries Published in RUNG: 03.03.2017; Views: 6873; Downloads: 0 This document has many files! More... |