title: Synthesis, Structure, and Electrochemical Properties of Na3MB5O10(M = Fe, Co) Containing M2+in Tetrahedral Coordination.
abstract: In the search for new cathode materials for sodium ion batteries, the exploration of polyanionic compounds has led to attractive candidates in terms of high redox potential and cycling stability. Herein we report the synthesis of the two new sodium transition-metal pentaborates Na3MB5O10(M = Fe, Co), where Na3FeB5O10represents the first sodium iron borate reported at present. By means of synchrotron X-ray diffraction, we reveal a layered structure consisting of pentaborate B5O10groups connected through M2+in tetrahedral coordination, providing possible three-dimensional Na-ion migration pathways. Inspired by these structural features, we examined the electrochemical performances versus sodium and showed that Na3FeB5O10is active at an average potential of 2.5 V vs Na+/Na0, correlated to the Fe3+/Fe2+redox couple as deduced from ex situ Mössbauer measurements. This contrasts with the case for Na3CoB5O10, which is electrochemically inactive. Moreover, we show that their electrochemical performances are kinetically limited, as deduced by complementary ac/dc conductivity measurements, hence confirming once again the complexity in designing high-performance borate-based electrodes.
authors.affiliation: National Institute of Chemistry , Hajdrihova 19, SI-1000 Ljubljana, Slovenia.|Sorbonne Universités - UPMC Univ Paris 06 , 4 Place Jussieu, F-75005 Paris, France.|UMR 8260 "Chimie du Solide et Energie", Collège de France , 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France.|ALISTORE-European Research Institute , 33 rue Saint-Leu, 80039 Amiens Cedex, France.
authors.forename: Florian
authors.initials: F
authors.lastname: Strauss
authors.affiliation: Sorbonne Universités - UPMC Univ Paris 06 , 4 Place Jussieu, F-75005 Paris, France.|UMR 8260 "Chimie du Solide et Energie", Collège de France , 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France.|ALISTORE-European Research Institute , 33 rue Saint-Leu, 80039 Amiens Cedex, France.|Réseau sur le Stockage Electrochimique de l'Energie (RS2E), FR CNRS 3459 , 33 Rue Saint Leu, 80039 Amiens Cedex, France.
authors.forename: Gwenaëlle
authors.initials: G
authors.lastname: Rousse
authors.affiliation: ALISTORE-European Research Institute , 33 rue Saint-Leu, 80039 Amiens Cedex, France.|Réseau sur le Stockage Electrochimique de l'Energie (RS2E), FR CNRS 3459 , 33 Rue Saint Leu, 80039 Amiens Cedex, France.|Institut Charles Gerhardt - UMR 5253 , 34095 Montpellier Cedex 5, France.
authors.forename: Moulay Tahar
authors.initials: MT
authors.lastname: Sougrati
authors.affiliation: UMR 8260 "Chimie du Solide et Energie", Collège de France , 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France.|Réseau sur le Stockage Electrochimique de l'Energie (RS2E), FR CNRS 3459 , 33 Rue Saint Leu, 80039 Amiens Cedex, France.
authors.forename: Daniel Alves
authors.initials: DA
authors.lastname: Dalla Corte
authors.affiliation: Réseau sur le Stockage Electrochimique de l'Energie (RS2E), FR CNRS 3459 , 33 Rue Saint Leu, 80039 Amiens Cedex, France.|Laboratoire de Réactivité et Chimie des Solides, Université de Picardie Jules Verne , 33 Rue Saint Leu, 80039 Amiens, France.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Courty
authors.affiliation: National Institute of Chemistry , Hajdrihova 19, SI-1000 Ljubljana, Slovenia.|ALISTORE-European Research Institute , 33 rue Saint-Leu, 80039 Amiens Cedex, France.
authors.forename: Robert
authors.initials: R
authors.lastname: Dominko
authors.affiliation: Sorbonne Universités - UPMC Univ Paris 06 , 4 Place Jussieu, F-75005 Paris, France.|UMR 8260 "Chimie du Solide et Energie", Collège de France , 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France.|ALISTORE-European Research Institute , 33 rue Saint-Leu, 80039 Amiens Cedex, France.|Réseau sur le Stockage Electrochimique de l'Energie (RS2E), FR CNRS 3459 , 33 Rue Saint Leu, 80039 Amiens Cedex, France.
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Tarascon