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7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Calorimetric study of skutterudite (CoAs2.92) and heazlewoodite (Ni3S2)

Abstract Nickel and cobalt arsenides, sulfarsenides, and sulfides occur in many hydrothermal ore deposits, but their thermodynamic properties are not well known, in some cases not known at all. In this work, we determined a full set of thermodynamic properties for heazlewoodite and skutterudite. Both phases were synthesized in evacuated silica tubes at elevated temperatures, and electron microprobe analyses gave their compositions as Ni3S2 and CoAs2.92, respectively. Enthalpies of formation were measured by high-temperature oxide-melt solution calorimetry. The reference phases were pure elements, thus eliminating any systematic errors related to such phases. The enthalpies of formation at T = 298.15 K and P = 105 Pa are –216.0 ± 8.4(2σ) and –88.2 ± 6.1 kJ·mol−1 for Ni3S2 and CoAs2.92, respectively. Entropies were calculated from low-temperature heat capacity (CP) data from relaxation (PPMS) calorimetry and are 133.8 ± 1.6 and 106.4 ± 1.3 J·mol–1·K–1, respectively. The calculated Gibbs free energies of formation are –210.0 ± 8.4 and –79.9 ± 6.2 kJ·mol−1 for Ni3S2 and CoAs2.92, respectively. The PPMS CP data, together with a set of differential scanning calorimetry measurements, were used to derive CP polynomials up to 700 K with the Kieffer model based on previously published frequencies of acoustic and optic modes. Equilibrium constants for selected reactions with an aqueous phase were calculated up to 700 K. Geochemical modeling in these systems, however, should await until more reliable data for other phases from the system Co-Ni-As-S are available.

Geochemistry & Geophysics↗
DOE OSTI2020

Dual Functional Ni3S2@Ni Core-Shell Nanoparticles Decorating Nanoporous Carbon as Cathode Scaffolds for Lithium-Sulfur Battery with Lean Electrolytes

Lithium-sulfur batteries are very promising for next-generation energy storage. However, most studies use flooded electrolytes to achieve a high specific capacity at the expense of lowering the specific energy. Understanding lithium-sulfur battery performance with lean electrolytes is highly desirable. Herein, a modified Pechini method is developed to synthesize a nanoporous carbon host decorated with Ni3S2@Ni particles. Such a cathode delivers enhanced specific capacities with extended cycling life in lean electrolytes, due to the dual functions of the Ni3S2 shell, which can both facilitate reaction kinetics and promote electrolyte wetting. This work highlights a strategy to rationally design cathodes for highenergy lithium-sulfur batteries.

Zhang, Yulun↗
DOE OSTI2020

Materials Data on Ni3S2 by Materials Project

Ni3S2 is Hazelwoodite structured and crystallizes in the trigonal R32 space group. The structure is three-dimensional. Ni+1.33+ is bonded to four equivalent S2- atoms to form a mixture of distorted edge and corner-sharing NiS4 tetrahedra. There are two shorter (2.25 Å) and two longer (2.28 Å) Ni–S bond lengths. S2- is bonded in a 6-coordinate geometry to six equivalent Ni+1.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni3S2 by Materials Project

Ni3S2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Ni+1.33+ sites. In the first Ni+1.33+ site, Ni+1.33+ is bonded to five S2- atoms to form a mixture of edge, face, and corner-sharing NiS5 square pyramids. There are one shorter (2.24 Å) and four longer (2.39 Å) Ni–S bond lengths. In the second Ni+1.33+ site, Ni+1.33+ is bonded to five S2- atoms to form a mixture of distorted edge, face, and corner-sharing NiS5 trigonal bipyramids. There are a spread of Ni–S bond distances ranging from 2.30–2.48 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a body-centered cubic geometry to eight Ni+1.33+ atoms. In the second S2- site, S2- is bonded in a 7-coordinate geometry to seven Ni+1.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni3S2 by Materials Project

Ni3S2 crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are three inequivalent Ni+1.33+ sites. In the first Ni+1.33+ site, Ni+1.33+ is bonded in a 3-coordinate geometry to three equivalent S2- atoms. All Ni–S bond lengths are 2.28 Å. In the second Ni+1.33+ site, Ni+1.33+ is bonded to four S2- atoms to form distorted corner-sharing NiS4 trigonal pyramids. There are one shorter (2.15 Å) and three longer (2.30 Å) Ni–S bond lengths. In the third Ni+1.33+ site, Ni+1.33+ is bonded in a distorted trigonal non-coplanar geometry to four S2- atoms. There are three shorter (2.16 Å) and one longer (2.65 Å) Ni–S bond lengths. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 6-coordinate geometry to seven Ni+1.33+ atoms. In the second S2- site, S2- is bonded to four Ni+1.33+ atoms to form corner-sharing SNi4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Directly Embedded Ni3S2/Co9S8@S-Doped Carbon Nanofiber Networks as a Free-Standing Anode for Lithium-Ion Batteries

Transition metal sulfides as electrode materials for lithium-ion batteries have attracted significant research attention due to their high theoretical capacity, excellent redox reversibility, and earth abundance. However, this material family still suffers from poor conductivity and experiences huge volume changes. Here, we demonstrate a facile and scalable electrospinning method to prepare Ni3S2 and Co9S8 nanoparticles embedded in sulfur doped carbon nanofiber networks as a free-standing anode material for lithium ion batteries. Similar to literature findings, the coupling of two different metal sulfides indeed synergistically promoted the electrochemical performance. Embedding them within individual carbon nanofibers not only enhances the intrinsic conductivity, but also provides a highly stable structure, which results in excellent battery performance. Furthermore, the individual carbon nanofibers intertwine with each other to form a free-standing 3D nanofiber network which acts as a freeway network for fast electron transfer and the pores between fibers allow easy penetration of the electrolyte, namely easy lithium ion access to active nanoparticles. When directly applied as the anode in lithium ion batteries, the free-standing nanofiber mat bypassed all slurry making steps and showed excellent cycling stability with a high specific capacity of 528 mA h g-1 after 200 cycles at a current density of 300 mA g-1. Good rate capability was also obtained. Additionally, the charge storage process analysis indicated that the pseudocapacitive behavior of the material is attributed to its good performance. This work introduces a facile strategy to simultaneously and in situ generate Co9S8 and Ni3S2 nanoparticles within a S-doped carbon fiber matrix via facile electrospinning followed by a one-step heating procedure. It is demonstrated that the free-standing transition bimetallic sulfide nanofibers prepared are very promising for light and small battery applications.

ADVANCED PROPULSION SYSTEMS,ENERGY STORAGE↗