| 1. |
- Ebadi, Mahsa, et al.
(författare)
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Density Functional Theory Modeling the Interfacial Chemistry of the LiNO3 Additive for Lithium-Sulfur Batteries by Means of Simulated Photoelectron Spectroscopy
- 2017
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:42, s. 23324-23332
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Tidskriftsartikel (refereegranskat)abstract
- Lithium-sulfur (Li-S) batteries are considered candidates for next-generation energy storage systems due to their high theoretical specific energy. There exist, however, some shortcomings of these batteries, not least the solubility of intermediate polysulfides into the electrolyte generating a so-called "redox shuttle", which gives rise to self-discharge. LiNO3 is therefore frequently used as an electrolyte additive to help suppress this mechanism, but the exact nature of the LiNO3 functionality is still unclear. Here, density functional theory calculations are used to investigate the electronic structure of LiNO3 and a number of likely species (N-2, N2O, LiNO2, Li3N, and Li2N2O2) resulting from the reduction of this additive on the surface of Li metal anode. The N is X-ray photoelectron spectroscopy core level binding energies of these molecules on the surface are calculated in order to compare the results with experimentally reported values. The core level shifts (CLS) of the binding energies are studied to identify possible factors responsible for the position of the peaks. Moreover, solid phases of (cubic) c-Li3N and (hexagonal) alpha-Li3N on the surface of Li metal are considered. The N is binding energies for the bulk phases of Li3N and at the Li3N/Li interfaces display higher values as compared to the Li3N molecule, indicating a clear correlation between the coordination number and the CLS of the solid phases of Li3N.
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| 2. |
- Ebadi, Mahsa, et al.
(författare)
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Modelling the Polymer Electrolyte/Li-Metal Interface by Molecular Dynamics simulations
- 2017
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Ingår i: Electrochimica Acta. - : Pergamon-Elsevier. - 0013-4686 .- 1873-3859. ; 234, s. 43-51
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Tidskriftsartikel (refereegranskat)abstract
- Solid polymer electrolytes are considered promising candidates for application in Li-metal batteries due to their comparatively high mechanical strength, which can prevent dendrite formation. In this study, we have performed Molecular Dynamics simulations to investigate structural and dynamical properties of a common polymer electrolyte, poly(ethylene oxide) (PEO) doped with LiTFSI salt in the presence of a Li metal surface. Both a physical (solid wall) and a chemical (slab) model of the Li (100) surface have been applied, and the results are also compared with a model of the bulk electrolyte. The average coordination numbers for oxygen atoms around the Li ions are ca. 6 for all investigated systems. However, the calculated Radial Distribution Functions (RDFs) for Li+-(OPEO) and Li+-(OTFSI) show sharper peaks for the Li slab model, indicating a more well-defined coordination sphere for Li+ in this system. This is clearly a surface effect, since the RDF for Li+ in the interface region exhibits sharper peaks than in the bulk region of the same system. The simulations also display a high accumulation of TFSI anions and Li+ cations close to interface regions. This also leads to slower dynamics of the ionic transport in the systems, which have a Li-metal surface present, as seen from the calculated mean-square-displacement functions. The accumulation of ions close to the surface is thus likely to induce a polarization close to the electrode.
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| 3. |
- Renault, Stevén, et al.
(författare)
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Dilithium 2-aminoterephthalate as a negative electrode material for lithium-ion batteries
- 2017
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738 .- 1872-7689. ; 307, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- This work presents the synthesis and characterization of a novel organic Li-battery anode material: dilithium 2-aminoterephthalate (C8H5Li2NO4). When investigated in Li half-cells, the resulting electrodes show stable capacities around ca. 180 mAh g− 1 and promising rate capabilities, with battery performance at 500 mA g− 1 and good capacity recovery, despite being an asymmetric compound. DFT calculations indicate a preferential lithiation on carboxylates close to the amino group.
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| 4. |
- Xu, Chao, et al.
(författare)
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LiTDI : A Highly Efficient Additive for Electrolyte Stabilization in Lithium-Ion Batteries
- 2017
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Ingår i: Chemistry of Materials. - : AMER CHEMICAL SOC. - 0897-4756 .- 1520-5002. ; 29:5, s. 2254-2263
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Tidskriftsartikel (refereegranskat)abstract
- The poor stability of LiPF6-based electrolytes has always been a bottleneck for conventional lithium-ion batteries. The presence of inevitable trace amounts of moisture and the operation of batteries at elevated temperatures are particularly detrimental to electrolyte stability. Here, lithium 2trifluoromethy1-4,5-dicyanoimidazole (LiTDI) is investigated as a moisture-scavenging electrolyte additive and can sufficiently suppress the hydrolysis of LiPF6. With 2 wt % LiTDI, no LiPF6 degradation can be detected after storage for 35 days, even though the water level in the electrolyte is enriched by 2000 ppm. An improved thermal stability is also obtained by employing the LiTDI additive, and the moisture-scavenging mechanism is discussed. The beneficial effects of the LiTDI additive on battery performance are demonstrated by the enhanced capacity retention of both the LiNi1/3Mn1/3Co1/3O2 (NMC)/Li and NMC/graphite cells at 55 degrees C. In particular, the increase in cell voltage hysteresis is greatly hindered when LiTDI is presented in the electrolyte. Further development of the LiTDI additive may allow the improvement of elevated-temperature batteries, as well as energy savings by reducing the amount of effort necessary for dehydration of battery components.
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