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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Studies on the properties and performance of TiS2 cathodes

Influence of raw material source, processing methods, and cell operating voltage limits on the performance of TiS2 cathode was examined. Raw materials obtained from three different sources were investigated. TiS2 electrodes were fabricated by painting, rolling, and pressing methods. Raw materials and electrodes were characterized for their physical, chemical, and electrochemical properties. The results obtained indicated that the performance of TiS2 cathodes was dependent on the purity and stoichiometry of the TiS2 material. Fabrication methods were found to have minimal influence on the performance of cathodes. The capacity loss observed during the early stages of cycling was attributed to the trapping of lithium in TiS2. Operating voltage limits were found to have significant influence on the cycle life performance of the cells.

Huang, C.-K.↗
NASA NTRS1990

Capacity decline of ambient temperature secondary Li-TiS2 cells

The main objective of the study described was to identify the causes responsible for the capacity losses observed during cycling of secondary Li-TiS2 cells. Experimental Li-TiS2 cells were fabricated and tested for their cycle life performance. The open circuit voltage of the cells was monitored during the rest period between the charging and discharging. The polarization at the Li and TiS2 electrodes was also monitored during cycling. Cycled cells were disassembled and the cathodes were analyzed by various analytical techniques. The results of the study indicate that the observed capacity loss is almost entirely due to the increased polarization of the TiS2 electrode with cycling. The electrolyte was found to degrade during cycling and the degradation products were found to deposit at the TiS2 electrode, which probably lead to the higher polarization.

Subbarao, S.↗
NASA NTRS1991

Advances In Li-TiS2 Cell Techno1ogy

JPL is involved in a NASA sponsored program to develop ambient temperature secondary Lithium - Titanium Disulfide Cells for future space missions. After several years of research on various lithium systems, the Li-TiS2 system was selected for development in view of its practically realizable high specific energy. In the last two years, the efforts were focused on improving the cycle life of the system and optimizing the cell design. A number of approaches, such as the use of mixed solvent electrolytes, the use of alternate anode materials, the operation of cells at low temperature, and the cycling of cells under optimized voltage limits, are examined to improve cycle life performance of this system. Cycling studies in small 150 mAh cell have identified 1.5 M LiAsF6/2-MeTHF, 1.5 M LiAsF6/EC+2-eTHF, and 1.5 M LiAsF6/THF+2-MeTHF+2-MeF as promising electrolytes for Li-TiS2 cells. Li-Al and Li-C were selected for further assessment as candidate anode materials after a detailed theoretical and experimental evaluation. Cycling of the cells at low temperature did not result in improving the cycle life of the cells. Charge and discharge voltage limits were found to have significant influence on the cycle life of the cells activated with 1.5 M LiAsF6/THF+2-MeTHF+2-MeF electrolyte. The influence of design variables, such as ratio of electrode capacity, quantity of electrolyte, pack tightness, cell configuration, etc., on the cycle life performance are being examined as a part of the design optimization study. Spiral-wound 1 Ah cells fabricated for the design studies have completed more than 500 cycles at 50% DOD. This paper summarizes the advances made in the Li-TiS2 technology at JPL since 1989.

Surampudi, S.↗
DOE OSTI2020

Materials Data on TiS2 by Materials Project

TiS2 is trigonal omega structured and crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of one TiS2 sheet oriented in the (0, 0, 1) direction. Ti4+ is bonded to six equivalent S2- atoms to form edge-sharing TiS6 octahedra. All Ti–S bond lengths are 2.43 Å. S2- is bonded in a distorted T-shaped geometry to three equivalent Ti4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiS2 by Materials Project

TiS2 crystallizes in the tetragonal I4/mmm space group. The structure is two-dimensional and consists of two TiS2 sheets oriented in the (0, 0, 1) direction. Ti4+ is bonded in a body-centered cubic geometry to eight equivalent S2- atoms. All Ti–S bond lengths are 2.58 Å. S2- is bonded in a 4-coordinate geometry to four equivalent Ti4+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1991

Advances in Li-TiS2 cell technology

JPL is involved in a NASA sponsored program to develop ambient temperature secondary cells for future space missions. After several years of research on various cathode materials, Titanium Disulfide (TiS2) was selected in view of its intrinsic reversibility and high faradaic utilization. In the last two years, the efforts were focused on improving the cycle life of the system and developing 1 Ah cells. Several approaches including the use of mixed solvent electrolytes, the operation of cells at low temperature, and the cycling of cells under different voltage limits, were initially examined to improve the cycle life performance of the Li-TiS2 system. Spiral wound 1 Ah cells fabricated incorporating the improvements from the above studies have delivered more than 600 cycles at 50% DOD. Work is in progress to identify alternate anode materials that can improve the cycle life of the cells to 1000 cycles at 50% DOD. This paper summarizes the advances made in the Li-TiS technology at JPL since 1989.

S Surampudi↗
NASA NTRS1991

The status of rechargeable Li-TiS2 cell technology

Ambient temperature rechargeable lithium-titanium disulfide (Li-TiS2) cells are under development at JPL for future NASA missions. The development of this technology has involved assessment and selection of electrolytes, optimization of cell design, fabrication of cells, preparation of TiS2 cathodes, and evaluation of lithium alloys. This effort has resulted in achieving a major milestone, completing 700 cycles at 50 percent depth of discharge in 1-Ah cells fabricated in house.

Halpert, G.↗
NASA NTRS1992

Effects of 12-crown-4 ether on the electrochemical performance of CoO2 and TiS2 cathodes in Li polymer electrolyte cells

The effect of adding 12-crown-4 ether (12Cr4) to the polyethylene oxide (PEO) electrolyte on the electrochemical properties of cells with Li(x)CoO2 or TiS2 as the cathode was investigated. The polymer electrolyte films were: (1) PEO, LiBF4; (2) PEO, LiBF4 with 12Cr4; (3) Li(x)CoO2, PEO, and LiBF4; and (4) Li(x)CoO2, PEO, LiBF4, and 12Cr4. It was found that, although 12Cr4 improved the cell performance over cells without 12Cr4 in the shallow c/d cycles (cyclic voltammetric behavior), it did not seem to prolong the active life of the cell. The cells with CoO2 as the cathode failed after a few c/d cycles, while similar cells with TiS2 did not fail even after 12 c/d cycles. The probable cause of failure in the case of CoO2 is ascribed to the instability of the CoO2 cathode.

Nagasubramanian, G.↗
NASA NTRS1992

Design analysis of bipolar Li-TiS2 batteries

The present study uses an empirical model to assess the feasibility of using the Li-TiS2 bipolar battery for high power applications. Predicted performance outputs at a variety of conditions were calculated. The effects of the design parameters on the performance of bipolar Li-TiS2 batteries are presented. Specific energies greater than 150 Wh/kg can be achieved at low rates. Specific power levels in excess of 100 W/kg can be reached at high rates but with a reduction of the specific energy to less than 70 Wh/kg.

Shen, D. H.↗
DOE OSTI2020

Materials Data on TiS2 by Materials Project

TiS2 is trigonal omega-like structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Ti4+ is bonded to six equivalent S2- atoms to form edge-sharing TiS6 octahedra. All Ti–S bond lengths are 2.43 Å. S2- is bonded in a distorted T-shaped geometry to three equivalent Ti4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(TiS2)4 by Materials Project

Ca(TiS2)4 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Ca2+ is bonded to six equivalent S2- atoms to form CaS6 octahedra that share corners with six equivalent TiS6 octahedra and edges with six equivalent TiS6 octahedra. The corner-sharing octahedral tilt angles are 4°. All Ca–S bond lengths are 2.67 Å. There are two inequivalent Ti+3.50+ sites. In the first Ti+3.50+ site, Ti+3.50+ is bonded to six equivalent S2- atoms to form TiS6 octahedra that share corners with six equivalent CaS6 octahedra and edges with six equivalent TiS6 octahedra. The corner-sharing octahedral tilt angles are 4°. All Ti–S bond lengths are 2.42 Å. In the second Ti+3.50+ site, Ti+3.50+ is bonded to six S2- atoms to form TiS6 octahedra that share edges with two equivalent CaS6 octahedra and edges with six TiS6 octahedra. There are two shorter (2.47 Å) and four longer (2.49 Å) Ti–S bond lengths. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three Ti+3.50+ atoms. In the second S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent Ti+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(TiS2)4 by Materials Project

Ca(TiS2)4 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Ca2+ is bonded to six equivalent S2- atoms to form distorted CaS6 octahedra that share corners with six equivalent TiS6 octahedra and edges with six equivalent TiS6 octahedra. The corner-sharing octahedral tilt angles are 8°. All Ca–S bond lengths are 2.80 Å. There are two inequivalent Ti+3.50+ sites. In the first Ti+3.50+ site, Ti+3.50+ is bonded to six S2- atoms to form TiS6 octahedra that share edges with two equivalent CaS6 octahedra and edges with six TiS6 octahedra. There are two shorter (2.44 Å) and four longer (2.47 Å) Ti–S bond lengths. In the second Ti+3.50+ site, Ti+3.50+ is bonded to six equivalent S2- atoms to form TiS6 octahedra that share corners with six equivalent CaS6 octahedra and edges with six equivalent TiS6 octahedra. The corner-sharing octahedral tilt angles are 8°. All Ti–S bond lengths are 2.44 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three Ti+3.50+ atoms. In the second S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent Ti+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiS2 by Materials Project

TiS2 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Ti4+ is bonded to twelve equivalent S2- atoms to form a mixture of edge and face-sharing TiS12 cuboctahedra. All Ti–S bond lengths are 2.89 Å. S2- is bonded in a 11-coordinate geometry to six equivalent Ti4+ and five equivalent S2- atoms. There are three shorter (2.49 Å) and two longer (2.93 Å) S–S bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiS2 by Materials Project

TiS2 crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are two inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to four S2- atoms to form corner-sharing TiS4 tetrahedra. The corner-sharing octahedral tilt angles are 60°. There are three shorter (2.26 Å) and one longer (2.45 Å) Ti–S bond lengths. In the second Ti4+ site, Ti4+ is bonded to six S2- atoms to form TiS6 octahedra that share corners with three equivalent TiS4 tetrahedra and edges with four equivalent TiS6 octahedra. There are a spread of Ti–S bond distances ranging from 2.28–2.61 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent Ti4+ atoms. In the second S2- site, S2- is bonded in an L-shaped geometry to two equivalent Ti4+ atoms. In the third S2- site, S2- is bonded in a distorted tetrahedral geometry to four Ti4+ atoms. In the fourth S2- site, S2- is bonded in a distorted trigonal planar geometry to three Ti4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Intrinsic Defect-Induced Local Semiconducting-to-Metallic Regions Within Monolayer 1T-TiS2 Displayed by First-Principles Calculations and Scanning Tunneling Microscopy

Using density functional theory (DFT) and scanning tunneling microscopy (STM), the intrinsic point defects, formation energy, and electronic structure of 1T-TiS2 were investigated. Defect systems include single-atom vacancies, interstitial and adatom additions, and direct atomic substitution. Using a collective approach for analyzing realistic systems for point defect investigation, we provide a more straightforward comparison to the experimental measurements, reproducing more realistic environmental conditions related to thin film growth. STM images are compared to computationally simulated electron density images to identify specific geometries that result from favorable point defects. DFT suggests that titanium interstitials are the most energetically favorable intrinsic defect, and sulfur vacancies are more likely to form than titanium vacancies within this realistic analysis, which is in agreement with STM data. A pristine, stoichiometric monolayer system is calculated to have a direct band gap of 0.422 eV, which varies based on local point defects. Local semiconducting-to-metallic electronic transitions are predicted to occur based on the presence of Ti interstitials.

Keeney, P. J.↗
NASA NTRS1992

High-Quality TiS2 For Li/TiS2 Cells

Modified process for synthesis of battery-grade titanium sulfide (TiS2) yields substantially improved material for Li/TiS2 electrochemical cells. Includes all-vapor-phase reaction between sulfur and titanium. Product less dense and more homogeneous, consists of smaller particles of higher crystalline quality, and purer. Cells have high cathode utilization and long cycle life performance. Expected to find applications in rechargeable lithium batteries for spacecraft, military equipment, telecommunication systems, automobiles, and consumer products.

Huang, Chen-Kuo↗
NASA NTRS1991

Cycle life characteristics of Li-TiS2 cells

The development of lithium ambient temperature rechargeable cells is discussed. During the development process, we hope to gain a greater understanding of the materials and the properties of the Li-TiS2 cell and its components. The design will meet the requirements of 100 Wh/Kg and 1000 cycles, at 50 percent depth-of-discharge, by 1995.

Deligiannis, Frank↗
NASA NTRS1991

Improved Li-TiS2 cell cycling in ether-based electrolytes with synergistic additives

Results of the application of 2-MeF and KOH additives to improve the lithium stability in THF, dioxolane, and THF/2-MeTHF solvent-based electrolytes are presented. The stability of these electrolytes with and without additives is evaluated by microcalorimetry and AC impedance spectroscopy. A novel method, cathode turnover number, is proposed to represent the electrolyte performance in a given system. The lithium cycling efficiency and cathode turnover number of the electrolytes are calculated from the cycle life data in experimental Li-TiS2 cells. Overall, THF/2-MeTHF electrolyte containing 2-MeF and/or KOH exhibited higher stability, lithium cycling efficiency, and cathode turnover number compared to THF and dioxolane electrolytes with and without additives.

Shen, D. H.↗