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Dihexyl-Substituted Poly(3,4-Propylenedioxythiophene) as a Dual Ionic and Electronic Conductive Cathode Binder for Lithium-Ion Batteries

Das, Pratyusha and Zayat, Billal and Wei, Qiulong and Salamat, Charlene Z. and Magdău, Ioan-Bogdan and Elizalde-Segovia, Rodrigo and Rawlings, Dakota and Lee, Dongwook and Pace, Gordon and Irshad, Ahamed and Ye, Liwei and Schmitt, Alexander and Segalman, Rachel A. and Miller, Thomas F., III and Tolbert, Sarah H. and Dunn, Bruce S. and Narayan, Sri R. and Thompson, Barry C. (2020) Dihexyl-Substituted Poly(3,4-Propylenedioxythiophene) as a Dual Ionic and Electronic Conductive Cathode Binder for Lithium-Ion Batteries. Chemistry of Materials, 32 (21). pp. 9176-9189. ISSN 0897-4756. https://resolver.caltech.edu/CaltechAUTHORS:20201021-121820625

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Abstract

The polymer binders used in most lithium-ion batteries (LIBs) serve only a structural role, but there are exciting opportunities to increase performance by using polymers with combined electronic and ionic conductivity. To this end, here we examine dihexyl-substituted poly(3,4-propylenedioxythiophene) (PProDOT-Hx₂) as an electrochemically stable π-conjugated polymer that becomes electrically conductive (up to 0.1 S cm⁻¹) upon electrochemical doping in the potential range of 3.2 to 4.5 V (vs Li/Li⁺). Because this family of polymers is easy to functionalize, can be effectively fabricated into electrodes, and shows mixed electronic and ionic conductivity, PProDOT-Hx₂ shows promise for replacing the insulating polyvinylidene fluoride (PVDF) commonly used in commercial LIBs. A combined experimental and theoretical study is presented here to establish the fundamental mixed ionic and electronic conductivity of PProDOT-Hx₂. Electrochemical kinetics and electron spin resonance are first used to verify that the polymer can be readily electrochemically doped and is chemically stable in a potential range of interest for most cathode materials. A novel impedance method is then used to directly follow the evolution of both the electronic and ionic conductivity as a function of potential. Both values increase with electrochemical doping and stay high across the potential range of interest. A combination of optical ellipsometry and grazing incidence wide angle X-ray scattering is used to characterize both solvent swelling and structural changes that occur during electrochemical doping. These experimental results are used to calibrate molecular dynamics simulations, which show improved ionic conductivity upon solvent swelling. Simulations further attribute the improved ionic conductivity of PProDOT-Hx₂ to its open morphology and the increased solvation is possible because of the oxygen-containing propylenedioxythiophene backbone. Finally, the performance of PProDOT-Hx₂ as a conductive binder for the well-known cathode LiNi_(0.8)Co_(0.15)Al_(0.05)O₂ relative to PVDF is presented. PProDOT-Hx₂-based cells display a fivefold increase in capacity at high rates of discharge compared to PVDF-based electrodes at high rates and also show improved long-term cycling stability. The increased rate capability and cycling stability demonstrate the benefits of using binders such as PProDOT-Hx₂, which show good electronic and ionic conductivity, combined with electrochemical stability over the potential range for standard cathode operation.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1021/acs.chemmater.0c02601DOIArticle
ORCID:
AuthorORCID
Zayat, Billal0000-0002-3794-3462
Magdău, Ioan-Bogdan0000-0002-3963-5076
Irshad, Ahamed0000-0001-7107-9623
Segalman, Rachel A.0000-0002-4292-5103
Miller, Thomas F., III0000-0002-1882-5380
Tolbert, Sarah H.0000-0001-9969-1582
Dunn, Bruce S.0000-0001-5669-4740
Narayan, Sri R.0000-0002-7259-3728
Thompson, Barry C.0000-0002-3127-0412
Additional Information:© 2020 American Chemical Society. Received: June 21, 2020; Revised: September 30, 2020; Published: October 19, 2020. This work was supported by the Center for Synthetic Control Across Length-Scales for Advancing Rechargeables (SCALAR), an Energy Frontier Research Center funded by the U. S. Department of Energy, Office of Science, Basic Energy Sciences under Award #DE-SC0019381. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. P.D. and L.Y. acknowledge USC Dornsife Graduate Student Fellowships. We also thank Ram Seshadri for helpful discussions, and we appreciate the assistance of Dr. Chun-Han Lai. Author Contributions: P.D. and B.Z. contributed equally. The authors declare no competing financial interest.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0019381
Department of Energy (DOE)DE-AC02-76SF00515
University of Southern CaliforniaUNSPECIFIED
Issue or Number:21
Record Number:CaltechAUTHORS:20201021-121820625
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20201021-121820625
Official Citation:Dihexyl-Substituted Poly(3,4-Propylenedioxythiophene) as a Dual Ionic and Electronic Conductive Cathode Binder for Lithium-Ion Batteries. Pratyusha Das, Billal Zayat, Qiulong Wei, Charlene Z. Salamat, Ioan-Bogdan Magdău, Rodrigo Elizalde-Segovia, Dakota Rawlings, Dongwook Lee, Gordon Pace, Ahamed Irshad, Liwei Ye, Alexander Schmitt, Rachel A. Segalman, Thomas F. Miller, Sarah H. Tolbert, Bruce S. Dunn, Sri R. Narayan, and Barry C. Thompson. Chemistry of Materials 2020 32 (21), 9176-9189; DOI: 10.1021/acs.chemmater.0c02601
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106185
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:21 Oct 2020 19:29
Last Modified:24 Nov 2020 17:35

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