High Performance Ternary Solid Polymer Electrolytes Based on High Dielectric Poly(vinylidene fluoride) Copolymers for Solid State Lithium-Ion Batteries

João C Barbosa; Daniela M Correia; Arkaitz Fidalgo-Marijuan; Renato Gonçalves; Stanislav Ferdov; Verónica de Zea Bermudez; Senentxu Lanceros-Mendez; Carlos M Costa

doi:10.1021/acsami.3c03361

High Performance Ternary Solid Polymer Electrolytes Based on High Dielectric Poly(vinylidene fluoride) Copolymers for Solid State Lithium-Ion Batteries

ACS Appl Mater Interfaces. 2023 Jul 12;15(27):32301-32312. doi: 10.1021/acsami.3c03361. Epub 2023 Jun 28.

Authors

João C Barbosa^{1

2}, Daniela M Correia³, Arkaitz Fidalgo-Marijuan^{4

5}, Renato Gonçalves³, Stanislav Ferdov¹, Verónica de Zea Bermudez^{2

6}, Senentxu Lanceros-Mendez^{1

4

7}, Carlos M Costa^{1

8}

Affiliations

¹ Physics Centre of Minho and Porto Universities (CF-UM-UP) and Laboratory of Physics for Materials and Emergent Technologies, LapMET, University of Minho 4710-057 Braga, Portugal.
² CQ-VR, University of Trás-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal.
³ Centre of Chemistry, University of Minho, 4710-057 Braga, Portugal.
⁴ BCMaterials, Basque Center for Materials, Applications and Nanostructures, UPV/EHU Science Park, 48940 Leioa, Spain.
⁵ Department of Organic and Inorganic Chemistry, University of the Basque Country UPV/EHU, 48940 Leioa, Spain.
⁶ Department of Chemistry, University of Trás-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal.
⁷ Ikerbasque, Basque Foundation for Science, 48009 Bilbao, Spain.
⁸ Institute of Science and Innovation for Bio-Sustainability (IB-S), University of Minho, 4710-053 Braga, Portugal.

Abstract

Renewable energy sources require efficient energy storage systems. Lithium-ion batteries stand out among those systems, but safety and cycling stability problems still need to be improved. This can be achieved by the implementation of solid polymer electrolytes (SPE) instead of the typically used separator/electrolyte system. Thus, ternary SPEs have been developed based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene), P(VDF-TrFE-CFE) as host polymers, clinoptilolite (CPT) zeolite added to stabilize the battery cycling performance, and ionic liquids (ILs) (1-butyl-3-methylimidazolium thiocyanate ([BMIM][SCN])), 1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([PMPyr][TFSI]) or lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), incorporated to increase the ionic conductivity. The samples were processed by doctor blade with solvent evaporation at 160 °C. The nature of the polymer matrix and fillers affect the morphology and mechanical properties of the samples and play an important role in electrochemical parameters such as ionic conductivity value, electrochemical window stability, and lithium-transference number. The best ionic conductivity (4.2 × 10^-5 S cm^-1) and lithium transference number (0.59) were obtained for the PVDF-HFP-CPT-[PMPyr][TFSI] sample. Charge-discharge battery tests at C/10 showed excellent battery performance with values of 150 mAh g^-1 after 50 cycles, regardless of the polymer matrix and IL used. In the rate performance tests, the best SPE was the one based on the P(VDF-TrFE-CFE) host polymer, with a discharge value at C-rate of 98.7 mAh g^-1, as it promoted ionic dissociation. This study proves for the first time the suitability of P(VDF-TrFE-CFE) as SPE in lithium-ion batteries, showing the relevance of the proper selection of the polymer matrix, IL type, and lithium salt in the formulation of the ternary SPE, in order to optimize solid-state battery performance. In particular, the enhancement of the ionic conductivity provided by the IL and the effect of the high dielectric constant polymer P(VDF-TrFE-CFE) in improving battery cyclability in a wide range of discharge rates must be highlighted.

Keywords: PVDF copolymers; lithium salt and ionic liquids; lithium-ion batteries; solid polymer electrolytes; ternary composites.