Three‐Component Solid Polymer Electrolytes Based on Li‐Ion Exchanged Microporous Silicates and an Ionic Liquid for Solid‐State Batteries

Abstract

Solid polymer electrolytes (SPEs) represent one of the most suitable options to overcome durability and safety issues. Herein, three‐component SPEs based on poly(vinylidene fluoride‐co‐hexafluoropropylene) as a binder, the 1‐butyl‐3‐methylimidazolium thiocyanate ionic liquid as an ionic conductive component, and zeolites, to improve SPE ionic conductivity and electrochemical stability, are prepared and characterized. Different zeolite and zeolite‐like structures (clinoptilolite, ETS‐4, and ETS‐10) are used, and the effect of lithium‐ion exchange in their structures is evaluated. A clear influence of the ion exchange process on the crystallinity of the prepared samples is observed, which plays a key role in the conduction mechanisms. The ionic conductivity of the samples at room temperature is of the order of 10−3 S cm−1, making them suitable for battery applications. The assembled batteries show promising results at room temperature, proving that the ion exchange has a positive effect on battery performance. The ion‐exchanged clinoptilolite sample presents the best performance at a prolonged cycle number, with an initial discharge capacity of about 130 mAh g−1 at C/10, and a capacity retention of 70% after 50 cycles. Thus, it is proved that the ion exchange process in microporous silicates represents a suitable strategy to develop high‐performance solid‐state lithium‐ion batteries (LIBs).

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

“…The thermal activation energy, calculated from the Arrhenius equation, are similar for samples (Table 3) and in line with those reported in literature for related systems. 28 The exception is the PVDF-HFP-CPT-LiTFSI sample, for which the activation energy is lower due to the interaction of the charged species with the polymer matrix. Further electrochemical analysis was carried out using cycling voltammetry to evaluate the electrochemical stability of the samples under different voltage conditions.…”

“…In this regard, 1-butyl-3-methylimidazolium thiocyanate ([BMIM]-[SCN]) has been explored as one of the most compatible IL for this purpose. 17,28 Another interesting IL is 1-methyl-1propylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([PMPyr][TFSI]) due to its high ionic conductivity and remarkable plasticizing effect. 29 The polymer matrix is a host for the fillers and an insulator barrier.…”

Influence of Solvent Evaporation Temperature on the Performance of Ternary Solid Polymer Electrolytes Based on Poly(vinylidene fluoride-co-hexafluoropropylene) Combining an Ionic Liquid and a Zeolite

“…25,26 Its ion exchange capacity and the possibility to include lithium ions in the CPT structure proved to improve battery capacity through the increase in the number of charge carriers. 27 Despite the importance of the materials selected in the SPE production, the preparation method is also a critical step to achieve optimized battery performance. In fact, it has been reported that the order of addition of the components has a significant influence on the battery stability with a capacity retention variation from 8 to 76% and a discharge capacity variation from ∼25 to 160.3 mAh•g −1 at a C/15-rate after 50 cycles, depending on the addition order of the fillers.…”

“…Regarding passive fillers, they allow us to improve the properties of the SPE, such as thermal and mechanical stability, contributing to further enhancing SPE operation . Although these passive fillers have usually been ceramics, in recent years the focus has also been placed on microporous materials, such as metal–organic frameworks (MOFs) and zeolites. , The interest in this kind of materials is mainly due to their high surface area and porous structure which allow a large number of interactions with other fillers and polymers, resulting in improved stability. , Different zeolites were studied recently, with clinoptilolite (CPT) being one of the most promising ones on account of its high thermal stability, low density, and high surface area. , Its ion exchange capacity and the possibility to include lithium ions in the CPT structure proved to improve battery capacity through the increase in the number of charge carriers …”

“…It must be emphasized that in the case of a polymer/solvent solution the solvent evaporation rate, depending on the processing temperature, strongly affects sample morphology and its physical-chemical, thermal, and electrical properties, which in turn will determine battery performance. In addition, the filler proportion for these ternary SPEs with two synergetic fillers has been optimized. , Thus, the goal of this work is to study the effect of solvent evaporation temperature during SPE processing by varying the temperature from room temperature to 160 °C, allowing both a deep understanding of the system and optimized performance. The ternary SPE studied is based on PVDF-HFP, CPT, and [Bmim]­[SCN], and the effect of the processing conditions on SPE morphology, physical-chemical characteristics (crystallinity and polar β-phase content), thermal and mechanical stability, ionic conductivity, electrochemical stability window, lithium transference number, and battery performance is reported.…”