| 1. |
- Mindemark, Jonas, et al.
(författare)
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Mechanical Stabilization of Solid Polymer Electrolytes through Gamma Irradiation
- 2017
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Ingår i: Electrochimica Acta. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0013-4686 .- 1873-3859. ; 230, s. 189-195
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Tidskriftsartikel (refereegranskat)abstract
- Attaining sufficient mechanical stability is a challenge for high-performance solid polymer electrolytes, particularly at elevated temperatures. We have here characterized the viscoelastic properties of the nonpolyether host material poly(epsilon-caprolactone-co-trimethylene carbonate) with and without incorporated LiTFSI salt. While this electrolyte material performs well at room temperature, at 80 degrees C the material is prone to viscous flow. Through gamma-irradiation at a dose of 25 kGy, the material stabilizes such that it behaves as a rubbery solid even at low rates of deformation while retaining a high ionic conductivity necessary for use in solid-state Li batteries. The performance of the irradiated electrolyte was investigated in Li polymer half-cells (Li vs. LiFePO4) at both 80 degrees C and room temperature. In Contrast with the notably stable battery performance at low temperatures using the non-irradiated material, during cycling of the irradiated electrolytes detrimental instabilities were noted at both 80 degrees C and room temperature. The possible effects of both radiation damage to the electrolyte and impaired interfacial contacts due to the crosslinking indicate that a different procedure may be necessary in order to stabilize these electrolytes for use in battery cells capable of stable long-term operation.
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| 2. |
- Mindemark, Jonas, et al.
(författare)
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Mechanical Stabilization of Solid Polymer Electrolytes through Gamma Irradiation
- 2016
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Konferensbidrag (refereegranskat)abstract
- Recent research efforts into solid polymer electrolytes (SPEs) beyond the polyether paradigm have broadened the research field with new materials that offer improvements in performance as well as opportunities for tailoring materials for specific applications. In particular materials based on polycarbonates and polyesters have shown to fulfil this promise, as shown for systems based on both the poly(ethylene carbonate) [1,2] and the poly(trimethylene carbonate) [3,4] backbone structures. This has ultimately led to the development of SPEs that can be used in Li batteries operational at room temperature. [1,4] Since ion conduction in these materials – at least at moderate salt concentrations – is coupled to the polymer chain dynamics, the performance of these electrolytes is inherently a compromise between mechanics and ion dynamics. While this is not necessarily an issue at room temperature, it becomes notable at elevated temperatures and we have observed migration of the electrolyte during long-term battery operation under such conditions, ultimately leading to failure of the electrolyte membrane to act as a separator between the electrodes with concomitant battery failure. A solution to this is to chemically crosslink the material in order to stabilize it mechanically. For the poly(ε-caprolactone-co-trimethylene carbonate) host material we have already successfully used in high-performance Li battery cells, [4] this can be done through γ-irradiation. [5] Here, we have explored this treatment in the context of SPEs and show the effects of γ-irradiation on the mechanical properties, ionic conductivity and battery cell performance at room temperature and beyond. Figure 1. Viscoelastic properties (left) and ionic conductivity (right) of pristine and γ-irradiated SPEs. References[1] K. Kimura, M. Yajima, Y. Tominaga, Electrochem. Commun. 66 (2016) 46-48.[2] M. D. Konieczynska, X. Lin, H. Zhang, M. W. Grinstaff, ACS Macro Lett. 4 (2015) 533-537.[3] J. Mindemark, B. Sun, D. Brandell, Polym. Chem. 6 (2015) 4766-4774.[4] J. Mindemark, B. Sun, E. Törmä, D. Brandell, J. Power Sources 298 (2015) 166-170.[5] E. Bat, J. A. Plantinga, M. C. Harmsen, M. J. A. van Luyn, Z. Zhang, D. W. Grijpma, J. Feijen, Biomacromolecules 9 (2008) 3208–3215
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| 3. |
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| 4. |
- Oltean, Gabriel, et al.
(författare)
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A Li-Ion Microbattery with 3D Electrodes of Different Geometries
- 2014
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Ingår i: ECS Electrochemistry Letters. - : The Electrochemical Society. - 2162-8734 .- 2162-8726. ; 3:6, s. A54-A57
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Tidskriftsartikel (refereegranskat)abstract
- A Li-ion microbattery comprising three-dimensional (3D) electrodes of different geometries is reported. While aluminum nanorods are used as the negative electrode a 3D carbon matrix with a larger surface area is used as support for the LiFePO4 positive electrode to compensate for the difference in the specific energy densities between LiFePO4 and Al. No difference in cycling behavior was observed for cells containing delithiated (Al) or partially lithiated (LixAl) nanorods as the negative electrode. The present electrode geometry concept is particularly promising for the design of Li-ion microbatteries in which 3D electrode materials with different specific energy densities are employed.
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| 5. |
- Oltean, Gabriel, et al.
(författare)
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Aluminium rods as current collectors and electrodes for 3D Li-ion micro-batteries
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The microelectronics industry has advanced at a rapid pace in the last decade. Further advancements are hampered by the lack of suitable on-board power devices. Although Li-ion batteries are the primary choice for energy storage, they cannot store enough energy per foot-print area without compromising power capability. Three-dimensional Li-ion batteries could offer the solution by using all three dimensions for efficient energy storage on a relatively small foot-print area.Aluminium rods were obtained by template assisted galvanostatic deposition of aluminium into the pores of a commercial membrane. By the subsequent chemical dissolution of the membrane, free standing arrays of aluminium rods deposited on an aluminium substrate were obtained. It was shown that the use of a nucleation pulse prior to deposition led to a homogeneous deposition of aluminium rods, while the use of pulsed current rather than constant current resulted in a narrower distribution of the rods heights [1].Aluminium is used as a current collector in Li-ion batteries. The deposition of TiO2 onto the aluminium rods was done by means of electrophoresis and a sol-gel derived impregnation method. While the electrophoretic deposition resulted in non-conformal coated rods, the impregnation method gave a thin amorphous deposit which could be cycled against lithium [2].Finally, aluminium can be used as a negative active material, as it alloys with lithium. A study of the alloying and dealloying of lithium and aluminium was done on the 3D aluminium rods and a model for the lithiation and delithiation of aluminium has been proposed [3]. The aluminium rods were used as a negative electrode in a Li-ion battery against LiFePO4 coated on carbon foam positive electrode in a 3D cell with different geometries of the two electrodes [4].References:[1] G. Oltean, L. Nyholm, K. Edström, Electrochim. Acta, 56 (2011) 3203.[2] G. Oltean, M. Valvo, L. Nyholm, K. Edström, Thin Solid Films, 562 (2014) 63.[3] G. Oltean, C.-W. Tai, K. Edström, L. Nyholm, J. Power Sources, 269 (2014) 266.[4] G. Oltean, H.D. Asfaw, L. Nyholm, K. Edström, ECS Electrochem. Lett, 3 (2014) A54.
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| 6. |
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| 7. |
- Oltean, Gabriel, 1982-
(författare)
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From Current Collectors to Electrodes : Aluminium Rod Structures for Three-dimensional Li-ion Micro-battery Applications
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The potential use of 3D aluminium nanorod structures as current collectors and negative electrodes for 3D Li-ion micro-batteries was studied based on the use of relatively simple and cost-effective electrochemical and sol-gel deposition techniques.Aluminium rod structures were synthesised by galvanostatic electrodeposition using commercial porous membranes as templates. It was shown that the use of a short (i.e., 50 ms long) potential pulse (i.e., -0.9 V vs. Al3+/Al) applied prior to a pulsed current electrochemical deposition gave rise to homogeneous deposits with more even rod heights. Electrophoretic and sol-gel deposition of TiO2 on the same substrates were also studied. The use of the sol-gel technique successfully resulted in a thin coating of amorphous TiO2 on the Al nanorod current collector, but with relatively small discharge capacities due to the amorphous character of the deposits. Electrophoretic deposition was, however, successful only on 2D substrates. Anodisation of titanium was used to prepare 3D TiO2 nanotube electrodes, with a nanotube length of 9 um and wall thickness of 50 nm. The electrodes displayed high and stable discharge capacities of 460 µAh/cm2 at a 0.1 C rate upon prolonged cycling with good rate capability.The 3D aluminium nanorod structures were tested as negative electrodes for Li-ion cells and the observed capacity fading was assigned to trapping of LiAl alloy inside the aluminium electrode caused by the diffusion of lithium into the electrode, rather than to pulverisation of the aluminium rods. The capacity fading effect could, however, be eliminated by decreasing the oxidation potential limit from 3.0 to 1.0 V vs. Li+/Li. A model for the alloying and dealloying of lithium with aluminium was also proposed. Finally, a proof-of-concept for a full 3D Li-ion micro-battery with electrodes of different geometries was demonstrated. The cell comprised a positive electrode, based on LiFePO4 deposited on a carbon foam current collector, with an area gain factor an order of magnitude larger than that for the Al nanorod negative electrode. This concept facilitates the balancing of 3D Li-ion cells as the positive electrode materials generally have significant lower specific energy densities than the negative electrodes.
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| 8. |
- Oltean, Gabriel, et al.
(författare)
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Galvanostatic electrodeposition of aluminium nano-rods for Li-ion three-dimensional micro-battery current collectors
- 2011
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 56:9, s. 3203-3208
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Tidskriftsartikel (refereegranskat)abstract
- Constant current and pulsed current electrodeposition of aluminium nano-rods, for use as three-dimensional (3D) Li-ion micro-battery current collectors, have been studied using an ionic liquid electrolyte (1-ethyl-3-methylimidazolium chloride/aluminium chloride) and a template consisting of a commercial alumina membrane. It is shown that the homogeneity of the height of the rods can be improved significantly by inclusion of a short (i.e. 50 ms) potential pulse prior to the controlled current deposition step. The latter potential step increased the number of aluminium nuclei on the aluminium substrate and the best results were obtained for a potential of -0.9 V vs. Al/Al3+. The obtained nanostructured surfaces, which were characterized using electron microscopy and X-ray diffraction, consisted of parallel aligned aluminium nano-rods homogeneously distributed over the entire surface of the substrate. A narrower height distribution for the rods was obtained using a pulsed galvanostatic approach then when using a constant current, most likely due to the less favourable diffusion conditions in the latter case. The results also indicate that depletion and iR drop effects within the nano-pores result in a more homogeneous height distribution. It is concluded that the height distribution of the nano-rods is controlled by a combination of the nucleation probability in each pore at the start of the experiment, and the homogeneity of the diameters of the pores within the commercial alumina membranes employed as the electrodeposition template.
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| 9. |
- Oltean, Gabriel, et al.
(författare)
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On the electrophoretic and sol-gel deposition of active materials on aluminium rod current collectors for three-dimensional Li-ion micro-batteries
- 2014
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 562, s. 63-69
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Tidskriftsartikel (refereegranskat)abstract
- Electrophoretic deposition of titanium oxide particles, as well as sol-gel synthesis of thin films of TiO2 employing a titanium isopropoxide precursor solution, were studied as possible deposition routes for the coating of aluminium pillar current collectors intended for three-dimensional Li-ion micro-batteries. While electrophoresis of TiO2 particles was homogeneously covering the two-dimensional aluminium substrates, it was difficult to conformally coat the three-dimensional current collectors with this technique. The sol-gel approach, on the other hand, gave rise to thin and amorphous TiO2 layers on the Al rod based current collectors. The latter could be cycled for 100 cycles indicating that such straightforward sol-gel approaches may be used for the manufacturing of 3D electrodes for Li-ion micro-batteries.
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| 10. |
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