Spectroscopic Insights into the Electrochemical Mechanism of Rechargeable Calcium/Sulfur Batteries

Antonio Scafuri (1, 2, 3, 4) , Romain Berthelot (3, 1, 5) , Klemen Pirnat (2) , Alen Vizintin (2) , Jan Bitenc (2) , Giuliana Aquilanti (6) , Dominique Foix (7, 5) , Rémi Dedryvère (7, 5, 1) , Iztok Arčon (8, 9) , Robert Dominko (2, 1, 4) , Lorenzo Stievano (3, 5, 1)

1 ALISTORE-ERI - Advanced Lithium Energy Storage Systems - ALISTORE-ERI
2 KI - National Institute of Chemistry [Llubljana]
3 ICGM - Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier
4 University of Ljubljana
5 RS2E - Réseau sur le stockage électrochimique de l'énergie
6 Elettra Sincrotrone Trieste
7 IPREM - Institut des sciences analytiques et de physico-chimie pour l'environnement et les materiaux
8 University of Nova Gorica
9 IJS - Jozef Stefan Institute [Ljubljana]

Calcium batteries represent a promising alternative to lithium metal batteries. The combination of the low redox potential and low-cost and 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 on 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 polysulfides 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.

Domaines: Matériaux

Antonio Scafuri, Romain Berthelot, Klemen Pirnat, Alen Vizintin, Jan Bitenc, et al.. Spectroscopic Insights into the Electrochemical Mechanism of Rechargeable Calcium/Sulfur Batteries. Chemistry of Materials, 2020, 32 (19), pp.8266-8275. ⟨10.1021/acs.chemmater.0c02074⟩. ⟨hal-02966157⟩