| 1. |
- Liu, Chenjuan, et al.
(författare)
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3-D binder-free graphene foam as a cathode for high capacity Li-O-2 batteries
- 2016
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4:25, s. 9767-9773
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Tidskriftsartikel (refereegranskat)abstract
- To provide energy densities higher than those of conventional Li-ion batteries, a Li-O-2 battery requires a cathode with high surface area to host large amounts of discharge product Li2O2. Therefore, reversible formation of discharge products needs to be investigated in Li-O-2 cells containing high surface area cathodes. In this study, a binder-free oxygen electrode consisting of a 3-D graphene structure on aluminum foam, with a high defect level (I-D/I-G = 1.38), was directly used as the oxygen electrode in LiO2 batteries, delivering a high capacity of about 9 x 10(4) mA h g(-1) (based on the weight of graphene) at the first full discharge using a current density of 100 mA g(graphene)(-1). This performance is attributed to the 3-D porous structure of graphene foam providing both an abundance of available space for the deposition of discharge products and a high density of reactive sites for Li-O-2 reactions. Furthermore, the formation of discharge products with different morphologies and their decomposition upon charge were observed by SEM. Some nanoscaled LiOH particles embedded in the toroidal Li2O2 were detected by XRD and visualized by TEM. The amount of Li2O2 formed at the end of discharge was revealed by a titration method combined with UV-Vis spectroscopy analysis.
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| 2. |
- Valvo, Mario, et al.
(författare)
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Electrochemical elaboration of electrodes and electrolytes for 3D structured batteries
- 2013
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Ingår i: JOURNAL OF MATERIALS CHEMISTRY A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 1:32, s. 9281-9293
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Tidskriftsartikel (refereegranskat)abstract
- The challenges associated with the fabrication of three-dimensional (3D) electrode and electrolyte materials for Li-ion batteries are discussed. The basic issues for achieving a solid 3D cell foundation, which can simultaneously offer sufficient electronic conductivity to enable stable cycling, as well as enough compatibility with the incorporation of complementary components, have been addressed. Various electrochemical strategies for elaborating such systems are discussed and critically examined. Several current collector systems are presented including electrochemically prepared Cu and Al nanorods and commercial aperiodic carbon structures. Further electrochemical coating approaches then provide a direct method for the deposition of thin layers of active materials successfully demonstrated here as coatings on both 3D metal structures and commercially available 3D-structured carbon substrates. Enhanced capacities per foot print area are demonstrated for a number of 3D electrode materials, namely polyaniline on reticulated vitreous carbon, Cu2O on copper nanorods and TiO2 on Al nanorods. The crucial points for achieving a thin conformal coating of the corresponding 3D electrode structures with solid polymer electrolytes are also carefully analysed and discussed. In this context electro-polymerisation is proposed as a viable route to form thin electrolyte layers with promising characteristics. The high versatility of electro-polymerisation in combination with the various structures and methodologies adopted here represents a further step towards the development of cost-effective 3D microbattery devices.
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| 3. |
- Valvo, Mario, et al.
(författare)
-
The impact of size effects on the electrochemical behaviour of Cu2O-coated Cu nanopillars for advanced Li-ion microbatteries
- 2014
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 2:25, s. 9574-9586
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Tidskriftsartikel (refereegranskat)abstract
- The generation of a distribution of nanoparticles upon conversion reaction of thin Cu2O layers is demonstrated to produce a wide electrochemical potential window, as well as a distinctive capacity increase in large area three-dimensional electrodes. Cu nanopillars with a 10-15 nm Cu2O coating containing traces of nanocrystattine Fe2O3 yield capacities up to 0.265 mA h cm(-2) (at 61 mA g(-1)), excellent cycling for more than 300 cycles and an electroactive potential window larger than 2 V. due to the size effects caused by the various Cu/Cu2O nanopartictes formed during conversion/deconversion. These 3D Li-ion battery electrodes based on etectrodeposited Cu nanopillars spontaneously coated with a Cu2O layer are compatible with current densities of 16 A g(-1) (i.e. 61 C rates) after aerosol-assisted infiltration with an iron acetate solution followed by low-temperature pyrolysis. The capacity of the composite material increases by 67% during 390 cycles due to the growth of the electroactive area during the electrochemical milling of Cu2O forced by its repeated conversion/de-conversion. The latter generates a distribution of nanoparticles with different sizes and redox potentials, which explains the broad potential window, as well as the significant capacity contribution from double layer charging. These 3D electrodes should be well-suited for Li-ion microbatteries and Li-ion batteries in general, since they combine high capacities per footprint area with excellent power capabilities. More importantly, such electrodes grant access to fundamental understanding of the electrochemical behaviour of these active materials providing new insights into both conversion mechanisms and nanostructured interfaces more in general.
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| 4. |
- Liu, Chenjuan, 1988-, et al.
(författare)
-
3-D binder-free graphene foam as cathode for high capacity Li-O2 batteries
- 2016
-
Ingår i: Journal of Materials Chemistry A. - 2050-7488. ; 4:25, s. 9767-9773
-
Tidskriftsartikel (populärvet., debatt m.m.)abstract
- To provide energy densities higher than those of conventional Li-ion batteries, a Li–O2 battery requires a cathode with high surface area to host large amounts of discharge product Li2O2. Therefore, reversible formation of discharge products needs to be investigated in Li–O2 cells containing high surface area cathodes. In this study, a binder-free oxygen electrode consisting of a 3-D graphene structure on aluminum foam, with a high defect level (ID/IG = 1.38), was directly used as the oxygen electrode in Li– O2 batteries, delivering a high capacity of about 9 *104 mA h g-1 (based on the weight of graphene) at the first full discharge using a current density of 100 mA ggraphene-1 . This performance is attributed to the 3-D porous structure of graphene foam providing both an abundance of available space for the deposition of discharge products and a high density of reactive sites for Li–O2 reactions. Furthermore, the formation of discharge products with different morphologies and their decomposition upon charge were observed by SEM. Some nanoscaled LiOH particles embedded in the toroidal Li2O2 were detected by XRD and visualized by TEM. The amount of Li2O2 formed at the end of discharge was revealed by a titration method combined with UV-Vis spectroscopy analysis.
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