| 1. |
- Baur, Christian, et al.
(författare)
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Improved cycling stability in high-capacity Li-rich vanadium containing disordered rock salt oxyfluoride cathodes
- 2019
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 7:37, s. 21244-21253
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Tidskriftsartikel (refereegranskat)abstract
- Lithium-rich transition metal disordered rock salt (DRS) oxyfluorides have the potential to lessen one large bottleneck for lithium ion batteries by improving the cathode capacity. However, irreversible reactions at the electrode/electrolyte interface have so far led to fast capacity fading during electrochemical cycling. Here, we report the synthesis of two new Li-rich transition metal oxyfluorides Li2V0.5Ti0.5O2F and Li2V0.5Fe0.5O2F using the mechanochemical ball milling procedure. Both materials show substantially improved cycling stability compared to Li2VO2F. Rietveld refinements of synchrotron X-ray diffraction patterns reveal the DRS structure of the materials. Based on density functional theory (DFT) calculations, we demonstrate that substitution of V3+ with Ti3+ and Fe3+ favors disordering of the mixed metastable DRS oxyfluoride phase. Hard X-ray photoelectron spectroscopy shows that the substitution stabilizes the active material electrode particle surface and increases the reversibility of the V3+/V5+ redox couple. This work presents a strategy for stabilization of the DRS structure leading to improved electrochemical cyclability of the materials.
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| 2. |
- Hahlin, Maria, 1975-, et al.
(författare)
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Surface compostions of dye/TiO2 interfaces formed from ethanol, acetonitrile, and dichloromethane based solutions
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The molecular and electronic surface structure of three TiO2 surfaces sensitized with 3-(5-(4-(diphenyl amino) styryl) thiophen-2-yl)-2-cyanoacrylic acid (D5) using different solvents (acetonitrile, dicloromethane, and ethanol) was investigated by photoelectron spectroscopy. The results showed solvent dependence in surface coverage, dye surface structure and energy level matching. Corresponding basic results on photocurrent conversion and UV-vis absorption is also included. Together the results indicated surface aggregation when using dichloromethane as a solvent.
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| 3. |
- Marinado, Tannia, et al.
(författare)
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Surface Molecular Quantification and Photoelectrochemical Characterization of Mixed Organic Dye and Coadsorbent Layers on TiO2 for Dye-Sensitized Solar Cells
- 2010
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:27, s. 11903-11910
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Tidskriftsartikel (refereegranskat)abstract
- Different molecular layers on TiO2 were prepared by using the p-dimethylaniline triphenylamine based organic dye, D29, together with the coadsorbents decylphosphonic acid (DPA), dineohexyl bis(3,3-dimethylbutyl)phosphinic acid (DINHOP), and chenodeoxycholic acid (CDCA). The surface molecular structure of dye and coadsorbent layers on TiO2 was investigated by photoelectron spectroscopy (PES). A focus was to determine the surface molecular concentrations using characteristic photoelectron core levels. Dye-sensitized solar cells (DSCs) were prepared from the same substrate and were further characterized by photoelectrochemical methods. Together the investigation gives information on the arrangement of the mixed molecular layer and a first insight to the extent to which the coadsorbents exchange with dye molecules on the TiO2 surface for the examined conditions.
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| 4. |
- Schölin, Rebecka, et al.
(författare)
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Preventing Dye Aggregation on ZnO by Adding Water in the Dye-Sensitization Process
- 2011
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:39, s. 19274-19279
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Tidskriftsartikel (refereegranskat)abstract
- ZnO based dye-sensitized solar cells have been studied using N719 and Z-907 as sensitizing dyes, with and without including water to the dye solution. The solar cells have been characterized with photoelectric measurements and the interface between the dye and the ZnO surface has been studied using photoelectron spectroscopy. It was shown that water in the dye solution greatly reduces surface dye aggregation and thereby enhances the solar cell performance for N719. For Z-907 where no sign of dye aggregation could be found, the presence of water had minor effect on the surface structure and solar cell performance.
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| 5. |
- Akiyama, Tomoko
(författare)
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Ionization Influence on the Dynamics of Simple Organic Molecules
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This licentiate thesis is devoted to the investigation of how bonding in simple organic molecules are affected by X-ray beam irradiation. The investigation targets molecules with three carbons as their main-chain structure. The stability of the bonds under ionization are simulated using the SIESTA package. SIESTA is a simulation package that provides molecular dynamics simulations based on density functional theory within the Born-Oppenheimer approximation. The aim of this study is to understand statistically the damaging process and selectivity among different types of bond. As the first targets, 4 hydrocarbons are investigated. They are propane, propene, propyne and propadiene, which have different combinations of single, double and triple bonds as their main-chain structures. Depending on the combinations, the structures can be either symmetric around the central atom or not. The structure of the symmetric molecules propane and propadiene are stable until charge +3. In contrast, the asymmetric molecules propene and propyne, the main-chain bonds show a tendency towards a more similar bond-distance as the level of ionization increases. In addition, hydrogens relocation occurs in propene, leading to a symmetric structure. Secondly, the bond fluctuations are investigated among 4 types of three-carbon molecules which have functional parts. Alcohol and carboxyl groups molecules show the stable bond integrities at charging 0 to +2. On the other hand, the carbon-carbon bonds in molecules with acetyl and ketone groups are broken by ionization. Comparing the 8 kinds of bond breaking processes in these molecules, this statistical study gives an insight to organic molecules bonding systems.
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| 6. |
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| 7. |
- Aktekin, Burak, et al.
(författare)
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How Mn/Ni Ordering Controls Electrochemical Performance in High-Voltage Spinel LiNi0.44Mn1.56O4 with Fixed Oxygen Content
- 2020
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Ingår i: ACS Applied Energy Materials. - : AMER CHEMICAL SOC. - 2574-0962. ; 3:6, s. 6001-6013
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Tidskriftsartikel (refereegranskat)abstract
- The crystal structure of LiNi0.5O4 (LNMO) can adopt either low-symmetry ordered (Fd (3) over barm) or high-symmetry disordered (P4(3)32) space group depending on the synthesis conditions. A majority of published studies agree on superior electrochemical performance of disordered LNMO, but the underlying reasons for improvement remain unclear due to the fact that different thermal history of the samples affects other material properties such as oxygen content and particle morphology. In this study, ordered and disordered samples were prepared with a new strategy that renders samples with identical properties apart from their cation ordering degree. This was achieved by heat treatment of powders under pure oxygen atmosphere at high temperature with a final annealing step at 710 degrees C for both samples, followed by slow or fast cooling. Electrochemical testing showed that cation disordering improves the stability of material in charged (delithiated) state and mitigates the impedance rise in LNMO parallel to LTO (Li4Ti5O12) and LNMO parallel to Li cells. Through X-ray photoelectron spectroscopy (XPS), thicker surface films were observed on the ordered material, indicating more electrolyte side reactions. The ordered samples also showed significant changes in the Ni 2p XPS spectra, while the generation of ligand (oxygen) holes was observed in the Ni-O environment for both samples using X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). Moreover, high-resolution transmission electron microscopy (HRTEM) images indicated that the ordered samples show a decrease in ordering near the particle surface after cycling and a tendency toward rock-salt-like phase transformations. These results show that the structural arrangement of Mn/Ni (alone) has an effect on the surface and "nearsurface" properties of LNMO, particularly in delithiated state, which is likely connected to the bulk electronic properties of this electrode material.
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| 8. |
- Amici, Julia, et al.
(författare)
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A Roadmap for Transforming Research to Invent the Batteries of the Future Designed within the European Large Scale Research Initiative BATTERY 2030
- 2022
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Ingår i: Advanced Energy Materials. - : John Wiley & Sons. - 1614-6832 .- 1614-6840. ; 12:17
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Forskningsöversikt (refereegranskat)abstract
- This roadmap presents the transformational research ideas proposed by "BATTERY 2030+," the European large-scale research initiative for future battery chemistries. A "chemistry-neutral" roadmap to advance battery research, particularly at low technology readiness levels, is outlined, with a time horizon of more than ten years. The roadmap is centered around six themes: 1) accelerated materials discovery platform, 2) battery interface genome, with the integration of smart functionalities such as 3) sensing and 4) self-healing processes. Beyond chemistry related aspects also include crosscutting research regarding 5) manufacturability and 6) recyclability. This roadmap should be seen as an enabling complement to the global battery roadmaps which focus on expected ultrahigh battery performance, especially for the future of transport. Batteries are used in many applications and are considered to be one technology necessary to reach the climate goals. Currently the market is dominated by lithium-ion batteries, which perform well, but despite new generations coming in the near future, they will soon approach their performance limits. Without major breakthroughs, battery performance and production requirements will not be sufficient to enable the building of a climate-neutral society. Through this "chemistry neutral" approach a generic toolbox transforming the way batteries are developed, designed and manufactured, will be created.
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| 9. |
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| 10. |
- Andersson, Edvin K. W., et al.
(författare)
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Initial SEI formation in LiBOB-, LiDFOB- and LiBF4-containing PEO electrolytes
- 2024
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 12:15, s. 9184-9199
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Tidskriftsartikel (refereegranskat)abstract
- A limiting factor for solid polymer electrolyte (SPE)-based Li-batteries is the functionality of the electrolyte decomposition layer that is spontaneously formed at the Li metal anode. A deeper understanding of this layer will facilitate its improvement. This study investigates three SPEs – polyethylene oxide:lithium tetrafluoroborate (PEO:LiBF4), polyethylene oxide:lithium bis(oxalate)borate (PEO:LiBOB), and polyethylene oxide:lithium difluoro(oxalato)borate (PEO:LiDFOB) – using a combination of electrochemical impedance spectroscopy (EIS), galvanostatic cycling, in situ Li deposition photoelectron spectroscopy (PES), and ab initio molecular dynamics (AIMD) simulations. Through this combination, the cell performance of PEO:LiDFOB can be connected to the initial SPE decomposition at the anode interface. It is found that PEO:LiDFOB had the highest capacity retention, which is correlated to having the least decomposition at the interface. This indicates that the lower SPE decomposition at the interface still creates a more effective decomposition layer, which is capable of preventing further electrolyte decomposition. Moreover, the PES results indicate formation of polyethylene in the SEI in cells based on PEO electrolytes. This is supported by AIMD that shows a polyethylene formation pathway through free-radical polymerization of ethylene.
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