Preparation of NiS[sub 2] Using Spark-Plasma-Sintering Process and Its Electrochemical Properties

Abstract

Single-phase NiS 2 , which was hardly prepared by conventional processes such as mechanical milling or precipitation reaction, was prepared using the spark plasma sintering ͑SPS͒ process. Using porous Ni ͑porosity 95%͒ as a starting material, similar-shaped porous NiS 2 ͑porosity 89%͒, containing trace amounts ͑ca. 3%͒ of NiS, and finally single-phase NiS 2 powder were obtained by the SPS process. The electrochemical tests demonstrated that the present NiS 2 samples showed the initial discharge capacity of ca. 820 mAh g −1 , which was ϳ94% of the theoretical value. The capacity retention after 10 cycles was ca. 19%, and such rapid degradation was mainly attributable to the irreversibility of the Li extraction from the lithiated ͑discharged͒ NiS 2 electrodes and the electrical disconnections among the active materials, carbon powders, and/or current collectors.Sulfur and metal sulfides are promising cathode materials for high-energy rechargeable lithium batteries because of their high theoretical capacities and relatively low costs.

Beyond Intercalation‐Based Li‐Ion Batteries: The State of the Art and Challenges of Electrode Materials Reacting Through Conversion Reactions

“…In general, the cycling properties of NiS 2 , [ 195 ] NiS, [ 190 , 196-199 ] and Ni 3 S 2 , [200][201][202] using a variety of electrolyte confi gurations (lithium salts in carbonate-based solvents, ionic liquids, polymer-based or inorganic glasses) have proved to be defi cient. The losses observed are, at least partly, due to the ineffi ciency of the re-conversion reaction from Ni and Li 2 S, [ 195 ] as it has been shown for NiS by the presence of Ni 3 S 2 at the end [ 231 , 232 ] before the reduced metal starts precipitating out. Density function theory (DFT) calculations have revealed that the very covalent nature of the M-P bonds yields electronic structures around the Fermi level (i.e., the electronic states involved in the redox activity of the compounds) in which bands with a strong P(3 s ,3 p ) character lie at high energy.…”

Recent Progress in Cathode Materials for Thermal Batteries

“…Inferred from the results of this study, the negative influence of the intermediate phase (NiS) becomes stronger when the NiS 2 particles are larger due to the relatively low conductivity of NiS, 96) leading to a decrease in discharge performance. In other words, NiS 2 produced rapid intermediate phase evolution, which increased the discharge capacity of the NiS 2 cathode.…”

Synthesis of submicron-sized NiPS₃ particles and electrochemical properties as active materials in all-solid-state lithium batteries

“…After the first discharge, the absorption edge slightly shifted toward the low energy region, suggesting that the valence of nickel slightly decreased during the discharge process. 32) A weak absorption edge around 8330 eV was observed, similar to the absorption edge of Ni metal though the absorbance was much weaker [ Fig. 5(e)].…”