P-redox mechanism at the origin of the high lithium storage in NiP2-based batteries

Simeon Boyanov (1) , J. Bernardi (1) , Emilie Bekaert (2) , Michel Ménétrier (2) , Marie-Liesse Doublet (1) , Laure Monconduit (1)

1 ICGM ICMMM - Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier
2 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

The Li reactivity of NiP₂ is investigated by means of electrochemical tests, in situ XRD, and ³¹P NMR characterizations as well as first principles DFT calculations. A two-step insertion/conversion reaction is shown to transform the NiP₂ starting electrode into an intermediate Li₂NiP₂ single phase and then to convert into the Li₃P/Ni° nanocomposite. The ternary phase is fully characterized and is shown to be structurally very close to the starting NiP₂ regarding the Ni ions environment. This demonstrates that its formation results from a P-redox insertion mechanism associated with a very good reversibility. However, its nucleation upon delithiation from the fully converted Li₃P/Ni composite is shown to be kinetically limited (poor structural relationship) which strongly suggests that restricted lithiation is required for best cycleability of the NiP₂/Li cell.

Mots clés: Lithium; Reactivity; NiP₂; Electrochemistry; XRD; ³¹ P Nuclear magnetic resonance; DFT

Domaines: Matériaux

Simeon Boyanov, J. Bernardi, Emilie Bekaert, Michel Ménétrier, Marie-Liesse Doublet, et al.. P-redox mechanism at the origin of the high lithium storage in NiP2-based batteries. Chemistry of Materials, 2009, 21 (2), pp.298-308. ⟨10.1021/cm802393z⟩. ⟨hal-00355776⟩