Advanced Green Printed Batteries for Portable Devices

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Surface wettability modification of poly(vinylidene fluoride) and copolymer films and membranes by plasma treatment

Publication . Correia, Daniela M.; Nunes-Pereira, João; Alikin, Denis; Kholkin; Carabineiro, S.A.C.; Rebouta, Luis; Rodrigues, Marco S.; Vaz, F.; Costa, C. M.; Lanceros-Mendez, Senentxu

This manuscript reports on the modification of the surface wettability of poly (vinylidene fluoride) (PVDF) and PVDF copolymer films and membranes by plasma treatments at different conditions, under oxygen and argon atmospheres. It is shown that a more pronounced decrease of the contact angle after O2 plasma treatments is obtained, with a decrease of ∼20-30° for PVDF and its copolymers films, leading also to superhydrophilic membranes. This effect is related to a defluorination process, followed by the incorporation of oxygen atoms onto the surface of membranes that occurs during the surface modification. The influence of plasma treatments on surface morphology and topography was studied by atomic force microscopy, showing a decrease in the mean surface roughness with the plasma treatments, being more noticeable for Ar treatments. Finally, it is also shown that plasma treatments under Ar and O2 did not induce modifications in the physicochemical and thermal properties of PVDF and PVDF copolymers. The chemical reaction mechanism after plasma treatment is proposed for the different copolymers.

2019Journal article

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Mesoporous poly(vinylidene fluoride-co-trifluoroethylene) membranes for lithium-ion battery separators

Publication . Costa, C. M.; Kundu, Manab; Dias, J. C.; Nunes-Pereira, João; Botelho, Gabriela; Silva, M. M.; Lanceros-Mendez, Senentxu

Mesoporous separator membranes based on poly(vinylidene fluoride-co-trifluoroethylene), PVDF-TrFE, were prepared through the removal of ZnO nanoparticles from the polymer matrix composite. Different filler concentrations were used, and the evaluation of the morphology, mechanical properties, uptake and ionic conductivity of the membranes were demonstrated that they depend on initial ZnO content in the composite. On the other hand, the vibration peaks characteristics of PVDF-TrFE and the thermal properties are independent on initial filler content. The membrane with the best ionic conductivity, 1.6 mS/cm, is the one prepared after 70 wt.% ZnO removal. The separator membranes were assembled in Li/C-LiFePO4 half-cells exhibiting good rate capability and cycling performance, the best battery performance being obtained for the PVDF-TrFE after 70 wt.% ZnO removal. The good performance of the developed separators was also demonstrated in full battery cells. Thus, a way to tailor membrane mesoporosity is presented and it is shown that the obtained membranes represent suitable separators for lithium-ion battery applications.

2019Journal article

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Synthetic polymer-based membranes for lithium-ion batteries

Publication . Martins, Pedro; Nunes-Pereira, João; Lanceros-Mendez, Senentxu; Costa, C. M.

Efficient energy storage systems are increasingly needed due to advances in portable electronics and transport vehicles, with lithium-ion batteries standing out among the most suitable energy storage systems for a large variety of applications. In lithium-ion batteries, the porous separator membrane plays a relevant role as it is placed between the electrodes, serves as a charge transfer medium, and affects the cycle behavior. Typically, porous separator membranes are comprised of a synthetic polymeric matrix embedded in the electrolyte solution. The present chapter focus on recent advances in synthetic polymers for porous separation membranes as well as on the techniques for membrane preparation and physicochemical characterization. The main challenges to improve the synthetic polymer performance for battery separator membrane applications are also discussed.

2020Book part

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Effect of Polymer Dissolution Temperature and Conditioning Time on the Morphological and Physicochemical Characteristics of Poly(Vinylidene Fluoride) Membranes Prepared by Non-Solvent Induced Phase Separation

Publication . Cardoso, V. F.; Botelho, Gabriela; Morão, António; Nunes-Pereira, João; Lanceros-Mendez, Senentxu

This work reports on the production of poly(vinylidene fluoride) (PVDF) membranes by non-solvent induced phase separation (NIPS) using N,N-dimethylformamide (DMF) as solvent and water as non-solvent. The influence of the processing conditions in the morphology, surface characteristics, structure, thermal and mechanical properties were evaluated for polymer dissolution temperatures between 25 and 150 C and conditioning time between 0 and 10 min. Finger-like pore morphology was obtained for all membranes and increasing the polymer dissolution temperature led to an increase in the average pore size ( 0.9 and 2.1 m), porosity ( 50 to 90%) and water contact angle (up to 80 ), in turn decreasing the PVDF content ( 67 to 20%) with the degree of crystallinity remaining approximately constant ( 56%). The conditioning time did not significantly affect the polymer properties studied. Thus, the control of NIPS parameters proved to be suitable for tailoring PVDF membrane properties.

2021Journal article

Open access

Comparative Evaluation of Dielectric Materials for Plasma Actuators Active Flow Control and Heat Transfer Applications

Publication . Rodrigues, Frederico; Nunes-Pereira, João; Abdollahzadehsangroudi, Mohammadmahdi; Pascoa, Jose; Lanceros-Mendez, Senentxu

Dielectric Barrier Discharge (DBD) plasma actuators are simple devices with great potential for active flow control applications. Further, it has been recently proven their ability for applications in the area of heat transfer, such as film cooling of turbine blades or ice removal. The dielectric material used in the fabrication of these devices is essential in determining the device performance. However, the variety of dielectric materials studied in the literature is very limited and the majority of the authors only use Kapton, Teflon, Macor ceramic or poly(methyl methacrylate) (PMMA). Furthermore, several authors reported difficulties in the durability of the dielectric layer when the actuators operate at high voltage and frequency. Also, it has been reported that, after long operation time, the dielectric layer suffers degradation due to its exposure to plasma discharge, degradation that may lead to the failure of the device. Considering the need of durable and robust actuators, as well as the need of higher flow control efficiencies, it is highly important to develop new dielectric materials which may be used for plasma actuator fabrication. In this context, the present study reports on the experimental testing of dielectric materials which can be used for DBD plasma actuators fabrication. Plasma actuators fabricated of poly(vinylidene fluoride) (PVDF) and polystyrene (PS) have been fabricated and evaluated. Although these dielectric materials are not commonly used as dielectric layer of plasma actuators, their interesting electrical and dielectric properties and the possibility of being used as sensors, indicate their suitability as potential alternatives to the standard used materials. The plasma actuators produced with these nonstandard dielectric materials were analyzed in terms of electrical characteristics, generated flow velocity and mechanical efficiency, and the obtained results were compared with a standard actuator made of Kapton. An innovative calorimetric method was implemented in order to estimate the thermal power transferred by these devices to an adjacent flow. These results allowed to discuss the ability of these new dielectric materials not only for flow control applications but also for heat transfer applications.

2021Conference object

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