Interrogation of Electrochemical Properties of Polymer Electrolyte Thin Films with Interdigitated Electrodes

Sharon, Daniel; Bennington, Peter; Liu, Claire; Kambe, Yu; Dong, Ban Xuan; Burnett, Veronica F.; Dolejsi, Moshe; Grocke, Garrett; Patel, Shrayesh N.; Nealey, Paul F.

doi:10.1149/2.0291816jes

Cited by 38 publications

(58 citation statements)

References 44 publications

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“…To compare the ionic transport behavior in SEO-LiTFSI and the analogous homopolymer PEO-LiTFSI electrolyte as a function of salt concentration, we first need to mitigate structural and morphological factors so as to enable the determination of the intrinsic electrochemical properties of the BCE. To do so, we employ an experimental system that consists of fully connected self-assembled parallel lamellar SEO-LiTFSI film spanning the width between and on top of interdigitated electrodes (IDEs), as recently developed in our lab. − Briefly, the electrochemical measurements are done on fabricated IDE arrays with a well-known cell constant . The IDE surface is coated with 1–2 nm of SiO 2 by atomic layer deposition (ALD).…”

Section: Resultsmentioning

confidence: 99%

Molecular Level Differences in Ionic Solvation and Transport Behavior in Ethylene Oxide-Based Homopolymer and Block Copolymer Electrolytes

et al. 2021

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Block copolymer electrolytes (BCE) such as polystyrene-block-poly(ethylene oxide) (SEO) blended with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and composed of mechanically robust insulating and rubbery conducting nanodomains are promising solid-state electrolytes for Li batteries. Here, we compare ionic solvation, association, distribution, and conductivity in SEO-LiTFSI BCEs and their homopolymer PEO-LiTFSI analogs toward a fundamental understanding of the maximum in conductivity and transport mechanisms as a function of salt concentration. Ionic conductivity measurements reveal that SEO-LiTFSI and PEO-LiTFSI exhibit similar behaviors up to a Li/ EO ratio of 1/12, where roughly half of the available solvation sites in the system are filled, and conductivity is maximized. As the Li/EO ratios increase to 1/5 the conductivity, of the PEO-LiTFSI drops nearly 3-fold, while the conductivity of SEO-LiTFSI remains constant. FTIR spectroscopy reveals that additional Li cations in the homopolymer electrolyte are complexed by additional EO units when the Li/EO ratio exceeds 1/12, while in the BCE, the proportion of complexed and uncomplexed EO units remains constant; Raman spectroscopy data at the same concentrations show that Li cations in the SEO-LiTFSI samples tend to coordinate more to their counteranions. Atomistic-scale molecular dynamics simulations corroborate these results and further show that associated ions tend to segregate to the SEO-LiTFSI domain interfaces. The opportunity for "excess" salt to be sequestered at BCE interfaces results in the retention of an optimum ratio of uncompleted and complexed PEO solvation sites in the middle of the conductive nanodomains of the BCE and maximized conductivity over a broad range of salt concentrations.

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Section: Resultsmentioning

confidence: 99%

Molecular Level Differences in Ionic Solvation and Transport Behavior in Ethylene Oxide-Based Homopolymer and Block Copolymer Electrolytes

et al. 2021

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“…To distinguish ionic from electronic conductivity, we designed the experiment to utilize gold interdigitated electrodes (IDEs) to characterize the impedance of PEO while using Li metal as the source of Li ions. [20,21] Devices were prepared with a neat PEO thin film (110 nm) spin coated onto a prefabricated IDE device. Both vacuum-deposited Li (400 nm) and bulk Li foils were studied and compared in order to determine the impact of the amount of available Li metal on the observed reactivity (Figure 1a,d, see Experimental Section for details of sample preparation).…”

Section: Resultsmentioning

confidence: 99%

“…By further fitting the EIS results to the equivalent circuit, the film resistance R f and the conductivity of both samples were calculated and plotted over time (Figure 1c,f ). The conductivities were calculated based on the IDE configuration [20,21] and assume that the PEO films were homogeneous at all times. In Figure 1c, a three orders of magnitude conductivity increase from 1 Â 10 À7 to 1 Â 10 À4 S cm À1 was observed for the PEO in contact with bulk Li foil.…”

Section: Resultsmentioning

confidence: 99%

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Increasing Ionic Conductivity of Poly(ethylene oxide) by Reaction with Metallic Li

Liu

Counihan

Zhu

et al. 2021

Adv Energy and Sustain Res

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One of the most important technological advances in sustainable energy harvesting and storage is the development of the Liion battery technology. In recent years, increasing demand for energy has revived development of sustainable storage technologies with Li metal as the anode due to the high theoretical specific capacity of Li metal (3860 mA h g À1 ). [1][2][3][4] As a result, the focus of much research in the field of Li energy storage is centered on development of solid electrolyte materials that can replace flammable organic solvents and enable the use of Li metal anodes, required for high energy density batteries. [5,6] To fully implement solid-solid Li-ion technology, many challenges need to be resolved, namely the stability of electrode materials and electrolytes and selectivity of electrochemical interfaces. [7] Addressing these will minimize undesired side reactions at electrode surfaces and suppress Li dendrite formation on the anode to improve battery performance and lifetime.Polyethylene oxide (PEO), in particular, has attracted great interest as a polymer electrolyte for use in solid state Li batteries due to its low glass transition temperature (%À60 C), mechanical properties, low material cost, and good interfacial contact with the anode. [8][9][10] However, the ionic conductivity of pure PEO at room temperature is %10 À9 -10 À8 S cm À1 , five orders of magnitude lower than the practical threshold (10 À3 S cm À1 ) needed to achieve realistic charge-discharge rates. [11] This necessitates further doping with salts, e.g., LiTFSI. Even then, the best room temperature conductivity of simple LiTFSI-doped PEO is around 10 À5 S cm À1 , so high temperatures (≥60 C) are required to achieve sufficient ionic conductivity.When mixed with lithium salts, ether oxygens in the PEO backbone coordinate to Li þ , leading to salt dissociation and mobile charge carriers in the mixture. [12] The introduction of salt also suppresses polymer crystallization, leading to more amorphous content within PEO, which also improves conductivity. [9] However, the anion greatly contributes to the increased ionic conductivity of doped PEO. Strong coordination between ether oxygens and Li þ cations leads to low lithium transference

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“…Detailed IDE fabrication process is described in the prior publication. [68] Four-point probe conductivity measurements were performed using a custom-designed probe station in an argon glovebox. Voltage and current measurements were performed using a Keithley 2400 source measure unit and Keithley 6221 precision current source.…”

Section: Methodsmentioning

confidence: 99%

Ionic Dopant‐Induced Ordering Enhances the Thermoelectric Properties of a Polythiophene‐Based Block Copolymer

Dong

Liu

Onorato

et al. 2021

Adv Funct Materials

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Conjugated polymer-based block copolymers (CP-BCPs) are an unexplored class of materials for organic thermoelectrics. Herein, the authors report on the electronic conductivity (σ) and Seebeck coefficient (α) of a newly synthesized CP-BCP, poly(3-hexylthiophene)-block-poly (oligo-oxyethylene methacrylate) (P3HT-b-POEM), upon solution co-processing with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and subsequently vapor-doping with a molecular dopant, 2,3,5,6-tetrafluoro-7,7,8,8tetracyanoquinodimethane (F4TCNQ). It is found that the addition of the hydrophilic block POEM greatly enhances the processability of P3HT, enabling homogeneous solution-mixing with LiTFSI. Notably, interactions between P3HT-b-POEM with ionic species significantly improve molecular order and unexpectedly cause electrical oxidizing doping of P3HT block both in solution and solid-states, a phenomenon that has not been previously observed in Li-salt containing P3HT. Vapor doping of P3HTb-POEM-LiTFSI thin films with F4TCNQ further enhances σ and yields a thermoelectric power factor PF = α 2 σ of 13.0 µW m −1 K −2 , which is more than 20 times higher than salt-free P3HT-b-POEM sample. Through modeling thermoelectric behaviors of P3HT-b-POEM with the Kang-Snyder transport model, the improvement in PF is attributed to higher electronic charge mobility originating from the enhanced molecular ordering of P3HT.The results demonstrate that solution co-processing CP-BCPs with a salt is a powerful method to control structure and performance of organic thermoelectric materials.

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Interrogation of Electrochemical Properties of Polymer Electrolyte Thin Films with Interdigitated Electrodes

Cited by 38 publications

References 44 publications

Molecular Level Differences in Ionic Solvation and Transport Behavior in Ethylene Oxide-Based Homopolymer and Block Copolymer Electrolytes

Molecular Level Differences in Ionic Solvation and Transport Behavior in Ethylene Oxide-Based Homopolymer and Block Copolymer Electrolytes

Increasing Ionic Conductivity of Poly(ethylene oxide) by Reaction with Metallic Li

Ionic Dopant‐Induced Ordering Enhances the Thermoelectric Properties of a Polythiophene‐Based Block Copolymer

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