In Situ NMR Study of a Cu 3 P Lithium Battery

Alan Wong (1) , Fabrizia Poli (2) , Laure Monconduit (3) , Michel Letellier (2)

1 LSDRM - Laboratoire Structure et Dynamique par Résonance Magnétique (LCF)
2 CRMD - Centre de Recherche sur la Matière Divisée
3 LAMMI - Laboratoire des Agrégats Moléculaires et Matériaux Inorganiques

In a quest for high capacity electrodes for lithium-ion secondary batteries, copper phosphide (Cu3P) has previously been investigated by in situ (real-time) XRD 2 as a possible negative electrode and demonstrated its good electrochemical performances. 1 However, the complete electrochemical mechanisms Cu3P⇌Li3P was not completely understood. For example, the expected final phase Li3P was not detected by XRD. For this reason, different analytical techniques should be considered to obtain complementary information and deduce the mechanism of the electrochemical reaction of Cu3P with lithium. Moreover, since Cu3P is a conversion material and that therefore metastable LixCu3-xP phases are formed during the potential cycling; consequently, in situ characterization is a preferable approach since the electrochemical reactions might evolve when the battery is stopped and dismantled for ex situ analyses. This study reports a multinuclei in situ NMR spectroscopic characterization of the electrochemical reactions of a Cu3P electrode towards lithium. Taking advantage of the different nuclear spin characteristics, we have obtained real-time 31 P and 7 Li NMR data for a comprehensive understanding of the electrochemical mechanism during the discharge (Cu3P→Li3P) and charge (Li3P→Cu3P) processes. The large NMR chemical shift span of 31 P facilitates the observation of the chemical evolutions of the different lithiated and delithated LixCu3-xP phases; whereas the quadrupolar line features in 7 Li enables the identification of the asymmetric Li sites. These combined NMR data offer an unambiguous identification of four distinct LixCu3-xP phases-Li3P, Li0.2Cu2.8P, Li2CuP and Cu 0-intercalated Li2CuP-and the characterization of their involvements in the electrochemical reactions. The study suggests that the presence of Cu 0-Li2CuP in the charge reaction might be responsible for the poor capacity retention in Cu3P lithium battery when cycles to a 'low' voltage potential.

Domaines: Matériaux

Alan Wong, Fabrizia Poli, Laure Monconduit, Michel Letellier. In Situ NMR Study of a Cu 3 P Lithium Battery. Zing Conference "Developments and Applications od Solid State NMR to Materials Science", May 2016, Varna, Bulgaria. ⟨cea-02345999⟩