| 11. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
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Effect of carbon coating methods on structural characteristics and electrochemical properties of carbon-coated lithium iron phosphate
- 2014
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 262, s. 25-29
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Tidskriftsartikel (refereegranskat)abstract
- The potential of LiFePO4 as cathode material has not been fully exploited due to its intrinsic poor electronic and ionic conductivities. Attempts have been made to improve these properties of which coating of the active carbon on the particle surface is the most viable method so far. Phase-pure LiFePO4 and two LiFePO4/C composites were synthesized by mechanical activation process employing two different methods: (i) direct addition of acetylene black carbon and (ii) addition of sucrose as carbon precursor. The samples were well characterized by various techniques like elemental analysis, Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and Raman spectroscopy to establish their composition, morphology, particle size and surface area. The structure of these samples is investigated as olivine structure space group Prima by X-ray powder diffraction. Transmission electron microscopy (TEM) confirms that the carbon nanocoating on the LiFePO4 particles has no visible dislocations and fractures. The electrochemical performance of LiFePO4/C is significantly affected by the nature of the carbon nanocoating, which in turn is affected by the choice of synthesis method.
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| 12. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
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Electrochemical properties of a full cell of lithium iron phosphate cathode using thin amorphous silicon anode
- 2014
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 268:Part B, s. 256-260
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Tidskriftsartikel (refereegranskat)abstract
- Carbon-coated lithium iron phosphate (LiFePO4/C) with uniform carbon coating was synthesized by a mechanical activation method. Silicon negative electrode material was obtained in the form of thin films of amorphous silicon on a Cu foil substrate by vertical deposition technique. The electrochemical performance of the full cell, LiFePO4/C-Si, was tested with 1 M LiPF6 in EC/DMC at 0.5 and 1 C-rates. The cell exhibited an initial discharge capacity of 143.9 mAh g(-1) at 0.5 C-rate at room temperature. A reasonably good cycling performance under a high current density of 1 C-rate could be obtained with the full cell.
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| 13. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
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Highly porous LiMnPO4 in combination with an ionic liquid-based polymer gel electrolyte for lithium batteries
- 2011
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Ingår i: Electrochemistry Communications. - : Elsevier BV. - 1388-2481. ; 13:10, s. 1105-1108
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Tidskriftsartikel (refereegranskat)abstract
- A porous well defined LiMnPO(4) cathode material is synthesized by a sol-gel method. The electrochemical performance of the cathode material is evaluated in a cell with an ionic liquid-based polymer electrolyte (0.5 M LITFSI in EMlmTFSI) and a lithium metal electrode. The results are compared to a cell with a traditional organic carbonate-based electrolyte (1 M LiPF(6) in EC/DMC). The cell with the ionic liquid-based polymer electrolyte presents an enhanced electrochemical intercalation performance of lithium ions, a high electrochemical stability window of 5 V, and an excellent cycling ability as compared with the organic based counterpart. Furthermore, the ionic liquid-based polymer gel electrolyte effectively prevents the dissolution of manganese - otherwise a common problem.
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| 14. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
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Improving the stability of an organic battery with an ionic liquid-based plymer electrolyte
- 2012
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 2:26, s. 9795-9797
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Tidskriftsartikel (refereegranskat)abstract
- A gel polymer electrolyte based on the ionic liquid {N-butyl-N-methyl-pyrrolidiniumbis(trifluoromethanesulfonyl) imide (Py14TFSI) and lithium bis(trifluoromethanesulfony)imide (LiTFSI)} is shown to prevent the dissolution from an organic electrode. The composite cell shows high energy efficiency although poor cycle stability is exhibited at very high current density (10 C-rate).
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| 15. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
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Nano-fibrous polymer films for organic rechargeable batteries
- 2013
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 1:7, s. 2426-2430
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Tidskriftsartikel (refereegranskat)abstract
- We propose a nano-fibrous polymer (NFP) film, fabricated by electrospinning poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA), as a key component in high performance organic batteries. The new strategy with a NFP film enables extraordinary rate capability and excellent cyclability, due to its special morphology. Moreover, the NFP film enhances the flexibility of the electrode at a low cost and prevents dissolution of PTMA into the electrolyte.
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| 16. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
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Preparation and application of TEMPO-based di-radical organic electrode with ionic liquid-based polymer electrolyte
- 2012
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 2:27, s. 10394-10399
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Tidskriftsartikel (refereegranskat)abstract
- In this study we report the synthesis and use of new organic materials, TEMPO di-radical [1,3-bis(4-(2,2,6,6,-tetramethyl-1-oxyl-4-piperidoxyl)butyl) imidazolium trifluorosulfonate]. Two cells were prepared with Li metal anode and the TEMPO di-radical based cathode with a microporous polymer electrolyte [1-butyl-3-methyl imidazolium bis(trifluoromethane sulfonyl) imide (BMImTFSI) in 0.5 M LiTFSI, and in 1 M LiPF6 in ethylene carbonate/dimethyl carbonate (EC/DMC)] hosted in electrospun poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP) membrane. The nature of the solvent was not found to affect the basic redox reaction behavior of TEMPO. The anodic and cathodic peaks were obtained at almost the same position and with some difference in the separation of peaks. The presence of BMImTFSI significantly affects the electrochemical performance of the battery as the cell having this RTIL exhibited far better electrochemical performance with 100% utilization of the active material and reasonably good cycling performance up to 200 cycles. We believe that this composite cell will contribute to organic green rechargeable batteries, although the cell is not fully organic composite.
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| 17. |
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| 18. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
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Towards flexible secondary lithium batteries: polypyrrole-LiFePO4 thin electrodes with polymer electrolytes
- 2012
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501 .- 0959-9428. ; 22:30, s. 15045-15049
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Tidskriftsartikel (refereegranskat)abstract
- A thin flexible polypyrrole-lithium iron phosphate (PPy-LiFePO4) based cathode has been fabricated. A slurry containing carbon black, a binder and the active material prepared by direct polymerization of pyrrole on the surface of LiFePO4 (LFP) was spread on an Al/carbon film substrate by the doctor blade method. Transmission electron micrographs reveal that PPy nanoparticles form a web like structure over the surface of LFP particles. After doping with lithium ions the PPy network becomes conducting. When evaluated as a cathode of 180 mu m thickness together with a gel polymer electrolyte and a lithium anode, the charge-discharge performance reveals that the electrochemical properties of LFP are influenced to a considerable extent by the PPy. The cells show high initial discharge capacities of 135 and 110 mA h g(-1) for 0.041 (C/10) and 0.21 (C/2) mA cm(-2), respectively, and high active material utilization. Furthermore the cells exhibit stable cycle properties even at 0.21 mA cm(-2) with a low capacity fade per cycle (similar to 0.3%).
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| 19. |
- Lim, D. H., et al.
(författare)
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Polymer electrolytes based on poly(vinylidene fluoride-co-hexafluoropropylene) nanofibrous membranes containing polymer plasticizers for lithium batteries
- 2012
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 225, s. 631-635
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Tidskriftsartikel (refereegranskat)abstract
- Gel polymer electrolytes (GPEs) were prepared with electrospun poly(vinylidene fluoride-co-hexafluoropropylene) [P(VdF-HFP)] nanofibrous membrane containing low molecular-weight polymer plasticizers, poly(ethylene glycol) dimethyl ether (PEGDME, Mw = 250 and 500). The fibers of electrospun membrane were stacked in layers to give fully interconnected pore structure with high porosity. The porous structure acted as a good host matrix to accommodate the polymer plasticizers. Thermogravimetric analysis (TGA) and field emission scanning electron microscope (FE-SEM) were used for thermal and physical characterizations, respectively. The GPEs exhibit high electrolyte uptake, high ionic conductivity, high anodic stability, and low interfacial resistance. Ionic conductivity and electrolyte uptake increased with the decrease in molecular weight of the polymer plasticizer. Prototype cells using electrospun P(VdF-HFP) nanofibrous GPEs with polymer plasticizers showed stable cyclic performances at different C-rates.
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| 20. |
- Lombardo, L., et al.
(författare)
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In-situ gelled electrolyte for lithium battery: Electrochemical and Raman characterization
- 2014
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 245, s. 232-235
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Tidskriftsartikel (refereegranskat)abstract
- n this paper we report a polymer lithium cell using a PVdF-based, gel-type electrolyte formed in-situ during cell assembly. The gel electrolyte formation is monitored prior to cell assembly by electro-chemical impedance spectroscopy and by Raman spectroscopy in order to determine the characteristics of the lithium salt diffusion into the gel-membrane. The results show an efficient gel formation and a fast lithium salt diffusion, this finally resulting in an optimized behaviour in a lithium cell using a high voltage spinel-type cathode. We believe that the results here reported may contribute to the enhancement of the safety of lithium batteries. (C) 2013 Elsevier B.V. All rights reserved.
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