A Microfluidic Device to Measure Electrode Response to Changes in Electrolyte Composition

Willey, Mark J.; West, Alan C.

doi:10.1149/1.2201253

Cited by 30 publications

(36 citation statements)

References 14 publications

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“…30,31 This cell was originally designed to resolve fast electrolyte changes over the working electrode. However in this work we used it to minimize ohmic resistance, while simultaneously controlling working electrode hydrodynamics.…”

Section: Methodsmentioning

confidence: 99%

An In Situ Synchrotron Study of Zinc Anode Planarization by a Bismuth Additive

Gallaway

Gaikwad

Hertzberg

et al. 2013

J. Electrochem. Soc.

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Cyclic voltammetry of zinc plated from flowing alkaline zincate electrolyte with a bismuth additive showed a marked mass transport effect during metal layer deplating. This bismuth was added as Bi 2 O 3 and had a saturated concentration of 26 ppm bismuth. Using a small, transparent window flow cell the mechanism was studied in situ using synchrotron X-rays. X-ray microdiffraction revealed that the metal-electrolyte interface was bismuth rich, and bismuth behaved in a manner similar to a surfactant. Transmission X-ray microscopy revealed that in the presence of bismuth additive, 5 μm raised features on the metal layer were preferentially dissolved during deplating. However, macro-morphology experiments demonstrated that at 26 ppm a detrimental bismuth buildup occurred over many cycles. By reducing additive concentration to 3 ppm a metal layer was planarized compared to a no-additive control, while avoiding the bismuth buildup. These findings suggested that 3 ppm bismuth could be used to planarize zinc metal layers such as those in flow-assisted zinc batteries. However, concentration will need to be well-controlled.Zinc anode batteries are desirable for secondary energy storage due to the water-compatibility, natural abundance, safety, and high energy density of zinc. 1 Zinc anodes are found in several forms, which vary widely in design. Examples include the anodes in the following: metallic zinc flow battery hybrids, pelletized zinc-air battery/fuel cell hybrids, zinc-manganese dioxide batteries, and flow-assisted alkaline nickel-zinc batteries. 2-9 Systems in which a zinc anode is plated onto a current collector from electrolyte under forced convection have received attention for large scale applications, as in the flow-assisted nickel-zinc battery referenced above. 4 A key challenge for these systems is high aspect ratio zinc "dendrites" which progressively form during charge-discharge cycling of the zinc layer. Unless mitigated, these structures cross the electrolyte gap and short the cell.The micro-morphology of these progressive dendrites is generally the mossy form of zinc. Thus they are not like crystalline dendrites or diffusion limited aggregation structures except in their aspect ratio. Strategies to prevent dendrites during metal plating are the subject of frequent investigations, such as varying current density, electrolyte flow rate, and current waveforms. 10-12 These all aim to prevent initial formation of a high aspect ratio profile on the metal layer, as once that has occurred electric field effects will intensify dendrite formation. Additives or leveling agents also work in this way, suppressing deposition at asperity tips. 13 Screening electrolyte additives for use in flow-assisted batteries, we observed that ppm quantities of bismuth oxide provoked a substantial mass transport effect during anodic dissolution of zinc. This lead us to speculate that small quantities of bismuth oxide could act as a "reverse" leveling agent, planarizing zinc layers during discharge of the layer. The action of bismu...

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Section: Methodsmentioning

confidence: 99%

An In Situ Synchrotron Study of Zinc Anode Planarization by a Bismuth Additive

Gallaway

Gaikwad

Hertzberg

et al. 2013

J. Electrochem. Soc.

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“…The channel design for the cell has been discussed in detail elsewhere. 24 Briefly, the microfluidic channels were molded from polydimethylsiloxane ͑PDMS͒ over a negative pattern created from SU-8 photolithography. The working channel had a rectangular cross section 500 m wide and 180 m tall, as confirmed by profilometry, through which the plating solution was flowed at 30 mL/h or 9.3 cm/s.…”

Section: Methodsmentioning

confidence: 99%

“…24,27 Figure 4a shows galvanostatic plating at −6.6 mA/cm 2 with 300 ppm of the indicated suppressor molecule introduced at time t = 0, either alone ͑solid lines͒ or with 10 ppm SPS ͑dashed lines͒. The additives were removed at time t = 108 s, when the plating bath returned to VMS.…”

Section: D148mentioning

confidence: 99%

Acceleration Kinetics of PEG, PPG, and a Triblock Copolymer by SPS during Copper Electroplating

Gallaway

Willey

West

2009

J. Electrochem. Soc.

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Three copper-plating suppressors are examined in three-additive baths: a polyethylene glycol ͑PEG͒, a polypropylene glycol ͑PPG͒, and a triblock copolymer of the two. Bis͑3-sulfopropyl͒-disulfide ͑SPS͒ is found to transition each to a state of nonsuppression, i.e., accelerate each, at a rate dependent on the suppressor molecule, the SPS concentration, and, to a lesser extent, the suppressor concentration. Using a planar microscale working electrode ͑d = 100 m͒, the kinetic currents of the plating reactions are observed without the influence of ohmic resistance, revealing far higher current densities than previously reported. Potentiostatic and galvanostatic experiments of additive adsorption at short times, t Ͻ 20 s, are compared quantitatively using a surfaceblocking model to transform the data to effective surface coverage, EFF , vs time. A major difference is found in SPS acceleration between galvanostatic and potentiostatic experiments, with the rate of change in suppression being proportional to the current density. This results in a constant rate of change in EFF under constant current but a self-reinforcing rate of change in EFF at constant potential. A simple additive model is introduced to characterize the results.The chosen material for interconnect manufacture in the semiconductor industry is electrodeposited copper, switched from aluminum in the late 1990s to achieve architecture scales below 250 nm. 1,2 The drive for increasing computing power continues, following the relation known as Moore's Law, and the characteristic scale of interconnects has fallen below 100 nm, approaching 30 nm and lower in the coming years. Electrodeposition of copper in highaspect-ratio features on this scale requires plating bath additives, which suppress and enhance deposition rates at the feature mouth and floor, respectively, to achieve bottom-up, void-free copper filling. This is referred to as superconformal filling or superfill.The additives required for superfill are a halide-ion promoter such as Cl − , a polyether suppressor such as polyethylene glycol ͑PEG͒, and a sulfur-containing molecule such as bis͑3-sulfopropyl͒-disulfide ͑SPS͒. Superfilling behavior results from an interaction of these additives, and this study focuses on plating behavior as a function of bath composition in order to formulate for decreasing feature sizes. It has been shown that the polyether suppressor and chloride ions coadsorb on the copper electrode surface, raising the overpotential required for a constant plating current. 3-7 This suppression becomes minor if the halide is not present and is a function of both halide and polyether concentration. 5 Other polyether molecules besides PEG ͓polypropylene glycol ͑PPG͒ and pluronic triblock copolymers of ethylene oxide ͑EO͒ and propylene oxide ͑PO͔͒ display the same characteristic suppression, although its degree is a function of the molecular structure. 8,9 A proportional increase of PO repeat units in the chain causes an increase in suppression. However, the presence of long, hydrophobic PO...

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“…To emulate the latter condition, a microfluidic device was used to observe in-situ changes on the electrode structure: the electrolyte flow is a medium to induce shear stress on the electrode surface. [10][11][12] This shear stress was correlated with the shear stress observed on the electrode surface during the flexing of the battery. Learning from these studies, we demonstrated a flexible battery electrode based on a mesh embedded architecture.…”

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confidence: 82%

Further studies in the electrochemical/mechanical strength of printed microbatteries

Gaikwad

Steingart

2011

SPIE Proceedings

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Flexible electronics require flexible energy storage, and electrochemical batteries are currently the strongest option for such devices. We further our previous investigation, beginning to add quantitative analysis to the composite mechanical/electrochemical performance of printed electrodes. The presented work will explain the principles of microfluidic stress analysis and how it provides insight into the operating conditions of real microbatteries. Introduction:

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A Microfluidic Device to Measure Electrode Response to Changes in Electrolyte Composition

Cited by 30 publications

References 14 publications

An In Situ Synchrotron Study of Zinc Anode Planarization by a Bismuth Additive

An In Situ Synchrotron Study of Zinc Anode Planarization by a Bismuth Additive

Acceleration Kinetics of PEG, PPG, and a Triblock Copolymer by SPS during Copper Electroplating

Further studies in the electrochemical/mechanical strength of printed microbatteries

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