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12 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Li(TiS2)2 by Materials Project

LiTi2S4 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Li1+ is bonded to six S2- atoms to form LiS6 octahedra that share corners with twelve equivalent TiS6 octahedra, edges with two equivalent LiS6 octahedra, and faces with two equivalent TiS6 octahedra. The corner-sharing octahedra tilt angles range from 43–51°. There are a spread of Li–S bond distances ranging from 2.58–2.69 Å. Ti+3.50+ is bonded to six S2- atoms to form TiS6 octahedra that share corners with six equivalent LiS6 octahedra, edges with six equivalent TiS6 octahedra, and a faceface with one LiS6 octahedra. The corner-sharing octahedra tilt angles range from 43–51°. There are a spread of Ti–S bond distances ranging from 2.39–2.56 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a rectangular see-saw-like geometry to one Li1+ and three equivalent Ti+3.50+ atoms. In the second S2- site, S2- is bonded to two equivalent Li1+ and three equivalent Ti+3.50+ atoms to form a mixture of distorted edge and corner-sharing SLi2Ti3 trigonal bipyramids.

36 MATERIALS SCIENCE↗
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.↗
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 NTRS1990

The influence of temperature on the cycle life performance of rechargeable Li-TiS2 cells

The authors report studies on the influence of low temperature on the properties and cycling performance of six selected electrolytes. The electrolytes investigated were 2-MeTHF, EC/2-MeTHF, THF, THF/2-MeTHF, EC/THF, and EC/THF/2-MeTHF. All the electrolytes contained 1.5M LiAsF6. Open circuit stand tests indicated that organic electrolytes exhibited improved stability towards lithium at 10 C. However, cycling of the cells at 10 C did not result in improved cycle life performance.

Shen, D. H.↗
NASA NTRS1990

The improvement of rechargeable lithium battery electrolyte performance with additives

The deliberate introduction of additives like 2-methylfuran (2-MeF) is known to improve Li cycleability in cyclic ether electrolytes. The authors found that the proclivity of 2-MeF to polymerize in the bulk electrolyte or on a TiS2 cathode was inhibited by the addition of reduced oxygen species, such as O2- and OH-. Additionally, the polymerization of tetrahydrofuran and dioxolane and the destructive processes initiated by AsF6- decomposition to AsF5 and AsF3 were inhibited by the introduction of reduced oxygen species, particularly OH- at the 10-ppm to 100-ppm level.

Dominey, L. A.↗
NASA NTRS1986

Examination of design options for 35 Ah ambient temperature Li-TiS sub 2 cells

The Jet Propulsion Laboratory is actively engaged in the development of ambient temperature rechargable lithium cells for future NASA geosynchronous Earth orbit (GEO) missions. To achieve these ambitious goals, Li-TiS2, Li-MoS3, and Li-V6O13 systems were examined in detail. Among these three, the Li-TiS2 system has shown the longest life cycle and highest rate capability. Experimental Li-TiS2 batteries (10.5 V, 0.4 Ah) developed in-house have completed eight simulated and accelerated GEO seasons successfully. Inview of the encouraging results, the design options were examined for a scaled-up Li-TiS2 cell. It is hoped that the results of these studies will provide guidelines for prioritizing the research efforts and guiding the selection of optimized materials. Designs for 35 Ah Li-TiS2 cell were examined because present day geosynchronous satellites are powered by batteries of 35 Ah capacity. A computer program was developed to evaluate the influence of various design parameters on the specific energy and the rate capability of the cells.

Shen, D. H.↗
NASA NTRS1991

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

Based on an extensive series of normalized full cell Li/TiS2 cycling studies, open-circuit storage tests, microcalorimetry and AC impedance studies, and chemical precedent, we propose an integrated chemical model consistent with experimental observations concerning the behavior of numerous LiAsF6/cyclic ether electrolytes. The particularly striking potency of certain additives such as 2-methylfuran and the hydroxide action resides in their ability to intercept several different adverse catalytic processes concurrently in the bulk electrolyte as well as the Li anode and TiS2 cathode.

Dominey, L. A.↗
DOE OSTI2020

Materials Data on LiTi(SO)2 by Materials Project

LiO2TiS2 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of one LiO2 sheet oriented in the (0, 0, 1) direction and one TiS2 sheet oriented in the (0, 0, 1) direction. In the LiO2 sheet, Li1+ is bonded to six equivalent O2- atoms to form edge-sharing LiO6 octahedra. There are four shorter (1.91 Å) and two longer (2.51 Å) Li–O bond lengths. O2- is bonded in a 4-coordinate geometry to three equivalent Li1+ and one O2- atom. The O–O bond length is 1.37 Å. In the TiS2 sheet, Ti3+ is bonded to six equivalent S atoms to form edge-sharing TiS6 octahedra. There are two shorter (2.42 Å) and four longer (2.46 Å) Ti–S bond lengths. S is bonded in a distorted T-shaped geometry to three equivalent Ti3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiTi(SO)2 by Materials Project

LiO2TiS2 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of one LiO2 sheet oriented in the (0, 0, 1) direction and one TiS2 sheet oriented in the (0, 0, 1) direction. In the LiO2 sheet, Li1+ is bonded to six equivalent O2- atoms to form edge-sharing LiO6 octahedra. There are four shorter (1.91 Å) and two longer (2.56 Å) Li–O bond lengths. O2- is bonded in a 4-coordinate geometry to three equivalent Li1+ and one O2- atom. The O–O bond length is 1.38 Å. In the TiS2 sheet, Ti3+ is bonded to six equivalent S atoms to form edge-sharing TiS6 octahedra. There are two shorter (2.42 Å) and four longer (2.46 Å) Ti–S bond lengths. S is bonded in a distorted T-shaped geometry to three equivalent Ti3+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1989

Advances in ambient temperature secondary lithium cells

The Jet Propulsion Laboratory is involved in a Research and Development program sponsored by NASA/OAST on the development of ambient temperature secondary lithium cells for future space applications. Some of the projected applications are planetary spacecraft, planetary rovers, and astronaut equipment. The main objective is to develop secondary lithium cells with greater than 100 Wh/kg specific energy while delivering 1000 cycles at 50 percent Depth of Discharge (DOD). To realize these ambitious goals, the work was initially focused on several important basic issues related to the cell chemistry, selection of cathode materials and electrolytes, and component development. The performance potential of Li-TiS2, Li-MoS3, Li-V6O13 and Li-NbSe3 electrochemical systems was examined. Among these four, the Li-TiS2 system was found to be the most promising system in terms of realizable specific energy and cycle life. Some of the major advancements made so far in the development of Li-TiS2 cells are in the areas of cathode processing technology, mixed solvent electrolytes, and cell assembly. Methods were developed for the fabrication of large size high performance TiS2 cathodes. Among the various electrolytes examined, 1.5M LiAsF6/EC + 2-MeTHF mixed solvent electrolyte was found to be more stable towards lithium. Experimental cells activated with this electrolyte exhibited more than 300 cycles at 100 percent Depth of Discharge. Work is in progress in other areas such as selection of lithium alloys as candidate anode materials, optimization of cell design, and development of 5 Ah cells. The advances made at the Jet Propulsion Laboratory on the development of secondary lithium cells are summarized.

Subbarao, S.↗
DOE OSTI2020

Materials Data on LiTiS2O by Materials Project

Li2O2(TiS2)2 crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of three Li2O2 sheets oriented in the (0, 0, 1) direction and three TiS2 sheets oriented in the (0, 0, 1) direction. In each Li2O2 sheet, Li1+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All Li–O bond lengths are 1.95 Å. O2- is bonded in a trigonal planar geometry to three equivalent Li1+ atoms. In each TiS2 sheet, Ti4+ is bonded to six S+1.50- atoms to form edge-sharing TiS6 octahedra. There are three shorter (2.41 Å) and three longer (2.43 Å) Ti–S bond lengths. There are two inequivalent S+1.50- sites. In the first S+1.50- site, S+1.50- is bonded in a 3-coordinate geometry to three equivalent Ti4+ atoms. In the second S+1.50- site, S+1.50- is bonded in a 3-coordinate geometry to three equivalent Ti4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

First-Principles Modeling of Sodium Ion and Water Intercalation into Titanium Disulfide Interlayers for Water Desalination

Recent experiments revealed the possibility of using titanium disulfide (TiS 2 ) as the cathode material in capacitive deionization (CDI) devices for water desalination. Although it performed stably up to 70 cycles with a salt removal capacity of 14 mg/g (corresponding to a sodium ion removal capacity of 35.8 mg/g) at high molar concentration (600 mM NaCl), the maximum capacity of TiS 2 as a CDI electrode was much lower (~70 mAh/g) than as a supercapacitor (239 mAh/g). Understanding why the ion capacities of these two configurations of the same material differ will entail elucidating detailed charge/discharge mechanisms at the atomic scale. Here, we present density functional theory simulations of sodium intercalation into TiS 2 interlayers in order to gain such understanding. We systematically investigated TiS 2 stacking patterns and ion intercalation sites, energetics of the intercalated compounds, and phase transformation during sodium intercalation. The calculated structural evolution and capacitance–voltage curve agree quite well with previous measurements. We conclude that the different maximum capacities of TiS 2 measured in aqueous and dry environments originate from weaker interlayer interactions with respect to shear strain after ~33% intercalation of Na + –H 2 O pairs, which is detrimental to the mechanical stability of TiS 2 . In conclusion, this study sheds light on the underlying mechanisms of ion intercalation into layered materials and contributes to understanding requirements for future design and optimization of CDI electrode materials for water desalination.

36 MATERIALS SCIENCE↗