Electrophoretic Deposition (EPD): An Alternative To Obtain Better Polymer - PowerPoint Presentation

1. Electrophoretic Deposition (EPD): An Alternative To Obtain Better Polymer Aluminium Electrolytic CapacitorsNéstor Calabia Gascón, Herman Terryn, Annick Hubin Vrije Universiteit Brussel, Pleinlaan 2, 1050 BrusselsConclusionsResults and DiscussionPoly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) has been proven as a versatile conductive polymer with a wide range of applications. Among others, its use in electrolytic capacitors is one of the most predominant. PEDOT:PSS – aluminium electrolytic capacitors show low internal equivalent series resistances (ESR), in contrast to their liquid counterparts, and can withstand temperatures up to 280 °C. As ideal as it sounds, obtaining the optimal properties for these capacitors requires achieving an intimate contact between the polymer phase and the porous aluminium structure. However, as a consequence of the viscosity of PEDOT:PSS dispersions, this is not an easy task. There exist different methods that try to achieve the optimal coverage, but they are time and energy consuming and they do not achieve the best coverage of PEDOT:PSS over porous aluminium. By applying a potential bias between the porous electrode while being immersed in PEDOT:PSS solution, this problem could be tackled. We explored the application of different potential biases that attract different ions in the polymeric dispersion to help the impregnation of porous electrodes to form the solid state PEDOT:PSS – aluminium capacitors with an optimized performance.IntroductionWakabayashi, T., et al., PH-Tunable High-Performance PEDOT:PSS Aluminum Solid Electrolytic Capacitors, ACS Appl. Energy Mater. 1, 2157–2163 (2018)Zhang, D. et al., Electrophoretic deposition of PTFE particles on porous anodic aluminum oxide film and its tribological properties, Appl. Surf. Sci. 290, 466–474 (2014)Electrophoretic deposition of PEDOT:PSSPEDOT+Electronic conductiveHydrophobicMinor componentPSS-Ionically conductiveHydrophillicStabilizes PEDOT in waterMajor componentAl substratePEDOT:PSSPorous Al~ 3 μm< 2 μm18 μmUnused porous structure Applying voltage of different signs, ions are separated by travelling to the two electrodesRepresentation of a micelle of PEDOT:PSS in waterPorous anodized aluminium electrode1 μmIntoThese sample treatments aim for two goals: Bringing in the highest amount of polymer possibleReducing the quantity of PSS that is incorporatedAl substrateWECE-+++++++------Micelle size 20 – 50 nmPore size > 500 nmBoth positive and negative voltages around Open Circuit Voltage (OCV) are usedNegative voltages attract preferentially PEDOTPositive voltages attract preferentially PSS, potentially dragging some PEDOT alongAs a preliminary approach to the selective inclusion of ions within a porous structure, this method proved to have little impact on the electrical properties of the produced samples when comparing a blanco sample with the polarized ones. Nevertheless, this electric response is far from an ideal capacitor. Consequently, applying -0.5 V and 0.5 V vs OCV for 10 minutes seems to have a negative impact on the electric response. Using different voltages could explain whether they damaged any of the materials upon application of the polymer. Despite the electrical response, there is evidence that part of the polymeric material is brought into the porous structure, as perceived in the SEM-EDX analysis. EPD shows to be a promising method of applying ionic dispersions where one of the ions is desired, even for large polymeric ions. Therefore, EPD can help reduce time and energy for the production of new PEDOT:PSS – aluminium capacitors.PEDOT:PSS3.81 μmPorous aluminium27.4 μmAluminium substrateSampleEffectVoltageapp vs OCVTimeBlancoNone0 V10 min- polarizedPEDOT is attracted-0.5 V10 min+ polarizedPSS is attracted0.5 V10 minElectrophoretic deposition1. Soak porous anodized aluminium in 0.1M Na2SO42. Substitution of solution by PEDOT:PSS3. Apply voltage for 10 minWECE4. Get rid of excess of PEDOT:PSS, dry and apply Ag pasteA negative voltage on the aluminium, attracts the electronically conductive PEDOTThe negative PSS stays around the counter electrodeUpon the absence of a voltage bias most of the dispersion remains outside the porous structureThe impregnation of PEDOT:PSS within the porous structure is followed thanks to the S signal in both components of PEDOT:PSSElectrochemical Impedance (EIS) AnalysisSEM morphology analysis SEM-EDX composition analysis Blanco- polarized+ polarizedPEDOT:PSSPEDOT:PSSPEDOT:PSSRegardless of the configuration, an accumulation of PEDOT:PSS can be observed outside of the porous area of thicknesses comprising between 1.7 μm and 2.1 μmThe close up look at the interface does not reveal a higher impregnation at those samples where a voltage was applied. There exists an abrupt decrease of sulphur contentThanks to the composition analysis, it is observed that the negatively polarized sample shows a higher amount of SThe higher amount of S compounds at the interface can be attributed to the sample that was positively polarized. However, the S content drops shortly after.The electrochemical analysis via EIS shows similar behavior for the 3 samples. This behavior is far from an ideal capacitive behavior (angle = -90°). A slight reduction on the impedance can be observed for both polarized samples vs the blanco.Ag pastePEDOT:PSSPEDOTPSS+Evolution of current during polarizationRE