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Li reactivity of the monoclinic NiP2 electrode is investigated through first-principles density functional theory calculations and local chemical bond analysis. The stability of various Li x NiP2 is studied with respect to the conversion reaction $${\text{NiP}}_{\text{2}} + {\text{6Li}} \to {\text{2Li}}_{\text{3}} + {\text{Ni}}^\circ $$ . The T = 0K Li x NiP2 phase stability diagram, as obtained, reveals that several ternary phases of lithium composition Li2NiP2 can be electrochemically achieved upon reduction. They correspond to monoclinic or tetragonal structures in which Ni adopts a square-planar (D4h-Li2NiP2) or a pseudo-tetrahedral (Td-Li2NiP2) environment. A local chemical bond analysis suggests that D4h–Li2NiP2 would result from an interlayer P–P bond breaking induced by a two-phase (P redox) process, while Td-Li2NiP2 would result from a Jahn–Teller distortion associated with a single-phase (Ni–P redox) process.

International audience; The iron-based metal organic framework (MOF) presently studied is the first example of MOF showing a reversible electrochemical Li insertion with a very good cycling life. Its potential application as a cathode material in Li-ion battery is nevertheless curbed by a rather poor capacity of 70 mAh/g. To figure out the origin of this limited insertion, first-principles density functional theory (DFT)+U calculations were performed. The results show that FeIII{OH(BDC)} is a weak anti-ferromagnetic charge transfer insulator at T=0 K with iron in the high-spin S=5/2 state. In agreement with the absence of electronic delocalisation along the inorganic chains, lithium insertion leads to the stabilisation of a FeII/FeIII mixed-valence state of class I or II in the Robin–Day classification, whatever the Li sites considered in the calculations. Among these Li sites, the most probable site I (OH-Li) and site II (O=CO-Li) are shown to induce incompatible structural changes on the reduced Li0.5Fe{OH(BDC)} form that could be at the origin of the small capacity measured for this compound.

Copper phosphide, Cu3P has been synthesized using a ceramic route, and its electrochemical behaviour versus lithium has been studied studied galvanostatic and potentiodynamic measurements and in situ X-ray diffraction analysis. The insertion/extraction mechanism proceeds with the formation of at least three different LixCu3−xP (x=1, 2, 3) phases. The electrochemical behaviour of Cu3P samples obtained from ceramic and solvothermal syntheses are compared to further understanding of the complex redox mechanism occurring during insertion/extraction. First-principle electronic structure calculations show that discharge probably begins with the formation of a solid solution LixCu3−yP (x