Microwave radiation (MWR), a type of electromagnetic excitation source,
reduces the synthesis temperature and processing time for chemical reactions
compared to traditional synthesis methods. Recently, we demonstrated that
MWR can engineer ceramics with different crystal phases compared to traditional methods [Journal of Materials Chemistry A 5, 35 (2017)]. In this study, we further apply the MWR-assisted technique to improve the electrochemical performance of LiCoO2 cathodes by engineering TiO2 and ZrO2 ceramic coatings. Electrochemical tests suggest that the TiO2 coating improves the rate capability of the LiCoO2 electrode. Both TiO2 and ZrO2 coatings improve the high-voltage (4.5 V) cycling stability of LiCoO2. The capacity remaining is improved from 52.8 to 84.4% and 81.9% by the TiO2 coating and the ZrO2 coating, respectively, after 40 cycles. We compare these results with existing studies that apply traditional methods to engineer TiO2/ZrO2 on LiCoO2, and find that the MWR-assisted method shows better performance improvement. X-ray photoelectron spectroscopy measurements suggest that the improved cycling stability arises from the formation of metal fluorides that protect the electrode from side reactions with electrolytes. This mechanism is further supported by the reduced Co dissolution from TiO2/ZrO2-coated LiCoO2 electrode after cycling. This study provides a new toolbox facilitating the integration of many delicate, low melting point materials like polymers into battery electrodes.
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Ultra-Light, Scalable and High-Temperature Resilient Ceramic Nanofiber Sponges
Ultralight and resilient porous nanostructures have been fabricated in various material forms, including carbon, polymers, and metals. However, the development of ultralight and high-temperature resilient structures still remains extremely challenging. Ceramics exhibit good mechanical and chemical stability at high temperatures, but their brittleness and sensitivity to flaws significantly complicate the fabrication of resilient porous ceramic nanostructures.
We report the manufacturing of large-scale, lightweight, high-temperature resilient, three-dimensional sponges based on a variety of oxide ceramic (for example, TiO2, ZrO2, yttria-stabilized ZrO2, andBaTiO3) nanofibers through an efficient solution blow-spinning process. The ceramic sponges consist of numerous tangled ceramic nanofibers, with densities varying from 8 to 40 mg/cm3. In situ uniaxial compression in a scanning electron microscope showed that the TiO2 nanofiber sponge exhibits high energy absorption (for example, dissipation of up to 29.6mJ/cm3 in energy density at 50% strain) and recovers rapidly after compression in excess of 20% strain at both room temperature and 400°C. The sponge exhibits excellent resilience with residual strains of only ~1%at 800°C after 10 cycles of 10%compression strain and maintains good recoverability after compression at ~1300°C. We show that ceramic nanofiber sponges can serve multiple functions, such as elasticity-dependent electrical resistance, photocatalytic activity, and thermal insulation.
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- Award ID(s):
- 1634492
- NSF-PAR ID:
- 10026158
- Date Published:
- Journal Name:
- Science advances
- Volume:
- 3
- Issue:
- 6
- ISSN:
- 2375-2548
- Page Range / eLocation ID:
- e1603170
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1126/sciadv.1603170
