Electrochemical activity and high ionic conductivity of lithium copper pyroborate Li₆CuB₄O₁₀

F. Strauss (1, 2, 3, 4, 5) , G. Rousse (6, 5, 1, 2) , Daniel Alves Dalla Corte (5, 6) , M. Ben Hassine (7) , M. Saubanère (8, 6) , M. Tang (9, 6) , H. Vezin (6, 10) , M. Courty (11, 6) , R. Dominko (3, 2) , J.-M. Tarascon (5, 1, 2, 6)

1 UPMC - Université Pierre et Marie Curie - Paris 6
2 ALISTORE-ERI - Advanced Lithium Energy Storage Systems - ALISTORE-ERI
3 KI - National Institute of Chemistry [Llubljana]
4 Faculty of Chemistry and Chemical Technology
5 Collège de France - Chaire Chimie du solide et énergie
6 RS2E - Réseau sur le stockage électrochimique de l'énergie
7 SPMS - Laboratoire Structures, Propriétés et Modélisation des solides
8 ICGM - Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier
9 CEMHTI - Conditions Extrêmes et Matériaux : Haute Température et Irradiation
10 LASIRE - Laboratoire Avancé de Spectroscopie pour les Intéractions la Réactivité et l'Environnement - UMR 8516
11 LRCS - Laboratoire réactivité et chimie des solides - UMR CNRS 7314

In the search for new cathode materials for Li-ion batteries, borate (BO₃^3-) based compounds have gained much interest during the last two decades due to the low molecular weight of the borate polyanions which leads to active materials with increased theoretical capacities. In this context we herein report the electrochemical activity versus lithium and the ionic conductivity of a diborate or pyroborate B₂O₅^4- based compound, Li₆CuB₄O₁₀. By combining various electrochemical techniques with in situ X-ray diffraction, we show that this material can reversibly insert/deinsert limited amounts of lithium (~0.3 Li⁺) in a potential window ranging from 2.5 to 4.5 V vs. Li+/Li0. We demonstrate, via electron paramagnetic resonance (EPR), that such an electrochemical activity centered near 4.25 V vs. Li⁺/Li⁰ is associated with the Cu³⁺/Cu²⁺ redox couple, confirmed by density functional theory (DFT) calculations. Another specificity of this compound lies in its different electrochemical behavior when cycled down to 1 V vs. Li⁺/Li⁰ which leads to the extrusion of elemental copper via a conversion type reaction as deduced by transmission electron microscopy (TEM). Lastly, we probe the ionic conductivity by means of AC and DC impedance measurements as a function of temperature and show that Li₆CuB₄O₁₀ undergoes a reversible structural transition around 350 °C, leading to a surprisingly high ionic conductivity of ~1.4 mS cm^-1 at 500 °C.

Domaines: Chimie théorique et/ou physique

F. Strauss, G. Rousse, Daniel Alves Dalla Corte, M. Ben Hassine, M. Saubanère, et al.. Electrochemical activity and high ionic conductivity of lithium copper pyroborate Li₆CuB₄O₁₀. Physical Chemistry Chemical Physics, 2016, 18, pp.14960 - 14969. ⟨10.1039/c6cp01581f⟩. ⟨hal-01348686⟩