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DOE OSTI2020

Materials Data on Ba(CuP2)2 by Materials Project

Ba(CuP2)2 crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight equivalent P1- atoms. There are four shorter (3.24 Å) and four longer (3.36 Å) Ba–P bond lengths. Cu1+ is bonded to four equivalent P1- atoms to form edge-sharing CuP4 tetrahedra. There are two shorter (2.32 Å) and two longer (2.37 Å) Cu–P bond lengths. P1- is bonded in a 6-coordinate geometry to two equivalent Ba2+, two equivalent Cu1+, and two equivalent P1- atoms. There are one shorter (2.19 Å) and one longer (2.34 Å) P–P bond lengths.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on CuP2 by Materials Project

CuP2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Cu2+ is bonded to four P1- atoms to form distorted CuP4 tetrahedra that share corners with four equivalent CuP4 tetrahedra, corners with seven equivalent PCuP3 tetrahedra, corners with two equivalent PCu3P2 trigonal bipyramids, and an edgeedge with one CuP4 tetrahedra. There are a spread of Cu–P bond distances ranging from 2.27–2.48 Å. There are two inequivalent P1- sites. In the first P1- site, P1- is bonded to three equivalent Cu2+ and two equivalent P1- atoms to form distorted PCu3P2 trigonal bipyramids that share corners with two equivalent CuP4 tetrahedra, corners with five equivalent PCuP3 tetrahedra, corners with six equivalent PCu3P2 trigonal bipyramids, and an edgeedge with one PCu3P2 trigonal bipyramid. There are one shorter (2.21 Å) and one longer (2.23 Å) P–P bond lengths. In the second P1- site, P1- is bonded to one Cu2+ and three P1- atoms to form distorted PCuP3 tetrahedra that share corners with two equivalent PCuP3 tetrahedra, corners with seven equivalent CuP4 tetrahedra, and corners with five equivalent PCu3P2 trigonal bipyramids. The P–P bond length is 2.21 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Dimer rattling mode induced low thermal conductivity in an excellent acoustic conductor

A solid with larger sound speeds usually exhibits higher lattice thermal conductivity. Here, we report an exception that CuP2 has a quite large mean sound speed of 4155 m s –1 , comparable to GaAs, but single crystals show very low lattice thermal conductivity of about 4 W m –1 K –1 at room temperature, one order of magnitude smaller than GaAs. To understand such a puzzling thermal transport behavior, we have thoroughly investigated the atomic structures and lattice dynamics by combining neutron scattering techniques with first-principles simulations. This compound crystallizes in a layered structure where Cu atoms forming dimers are sandwiched in between P atomic networks. In this work, we reveal that Cu atomic dimers vibrate as a rattling mode with frequency around 11 meV, which is manifested to be remarkably anharmonic and strongly scatters acoustic phonons to achieve the low lattice thermal conductivity.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Quantifying the reaction mechanisms of a high-capacity CuP 2 /C composite anode for potassium ion batteries

Introducing metals into phosphorus to form metal phosphide materials as anodes for potassium ion batteries (PIBs) is an effective strategy to improve the electronic conductivity and alleviate the volume change during cycling, although with a compromise of capacity. Here in this paper, we explore a CuP 2 /C composite as a novel anode for PIBs, which delivers a high reversible capacity of >450 mA h g -1 . Unexpectedly, our results reveal that the POx components existing in the prepared composite are reversible, through a quantitative analysis via high-resolution solid-state 31 P NMR and synchrotron X-ray diffraction tests. Their potassiation products K 3 PO 4 and K 4 P 2 O 7 can react with K–P alloys and turn back to PO x during depotassiation, which probably accounts for the high capacity of the prepared material. The results also illustrate a crystallization–amorphization evolution process during cycling involving nanocrystalline α-K 4 P 6 , K 4 P 3 and KP, and amorphous K 4 P 6 , KP and K 3 P phases, among which, the amorphous phases are identified for the first time.

25 ENERGY STORAGE↗