High Lithium Conductivity of Miscible Poly(ethylene oxide)/Methacrylic Sulfonamide Anionic Polyelectrolyte Polymer Blends

Abstract

In this work, we develop novel single-ion polymer electrolytes by mixing poly(lithium 1-[3-(methacryloyloxy) propylsulfonyl]-1-(trifluoromethanesulfonyl) imide) (PLiMTFSI) and poly(ethylene oxide) (PEO) with different molecular weights. The impact of PLiMTFSI on the crystallization and conductivity of the blends was explored in detail. When PLiMTFSI (an amorphous polymer) is added to PEO, the crystallization ability of PEO decreases. However, blends with high-molecular weight PEO (1000 kg/mol) experience a lower reduction in crystallinity and melting points. As a result, lower conductivity values were obtained in these blends, which is why most of the study was then focused on blends incorporating a lower-molecular weight PEO (100 kg/mol). We show that the melting point, degree of crystallinity, spherulitic growth, and overall crystallization kinetics decrease in the presence of PLiMTFSI, which are all signs of miscibility. Furthermore, the blends show a single glass transition temperature over the whole composition range. Therefore, our results indicate that PEO and PLiMTFSI are miscible, as corroborated by applying the Nishi−Wang equation and obtaining negative χ 12 values (i.e., the Flory−Huggins interaction parameter) for all blends. Our results show that intermediate molecular weight blends (100 kg/mol PEO and 50 kg/mol PLiMTFSI) showed the highest ionic conductivity value. Interestingly, a value of 2.1 × 10 −4 S/cm was obtained at 70 °C, which is one of the highest reported so far for a free-standing film of single-ion conducting polymer electrolytes. Finally, employing dielectric spectroscopy, the contribution of ion density and ion mobility to ionic conductivity could be separated. It was found that ion mobility is the parameter that has a greater weight in the conduction process.

Electrolyte and anode‐electrolyte interphase in solid‐state lithium metal polymer batteries: A perspective

“…S/cm at 70 • C. 12 For example, Blazejczyk et al 22 reported that the addition of calixarene-type supramolecular compounds as anion traps could greatly suppress the mobility of I − ions in LiI/PEO but with a low σ Li + close to 10 −5 S/cm at 95 • C. By chemically tethering anions to polymer backbones, Figure 1C, for example, grafting a TFSIlike (i.e., CF 3 SO 2 N (−) SO 2 -) moiety to polystyrene, [23][24][25] polyacrylates, 26 could sufficiently immobilize negative charges and approach T Li + close to unity. The polymer core could be also replaced by inorganic nanoparticles, that is, nanoalumina, nanosilica, etc., Figure 1D, high T Li + values are also reported.…”

Single‐Ion Conducting Polymer Electrolytes for Solid‐State Lithium–Metal Batteries: Design, Performance, and Challenges

“…Due to the extensive demand of world energy consumption, energy storage devices with high energy density and improved safety are needed. [ 1–10 ] Solid‐state rechargeable batteries have received significant attention not only because they can address conventional liquid electrolytes’ safety issues, which suffer from flammability and leakage due to organic solvents, but also the potential to enhance the overall energy density. [ 11–15 ] Among various solid‐state electrolytes (SSEs), many efforts have been devoted to solid polymer electrolytes (SPEs), which possess numerous attractive properties, including high flexibility, processability, and shape versatility, as well as low density.…”

Ionic Transport and Thermodynamic Interaction in Precision Polymer Blend Electrolytes for Lithium Batteries

“…Recent literature reports an interaction parameter of −1.15 between methacrylic sulfonyl imide derived polyelectrolyte (PLiMTFSI) and PEO with the melting point depression going from 69 to 62 °C at only 30 wt% polyelectrolyte. [ 34 ] In contrast, our blend compositions exhibit a narrower melting point depression range (5 °C) with larger compositions of study. The magnitude of T m depression for PLiMTFSI/PEO is larger than that observed in our study, which indicates PLiMTFSI/PEO has greater compatibility.…”

“…[ 27,28 ] Assuming reasonably high degrees of polymerization (greater than 100) such as those used in this study (454 for PEO, 116 for p 5PhS‐Li), the melting point composition expression for polymer‐diluent mixtures equation can be written as [ 29,30 ] where T m,PEO is the melting point of pure PEO, T m,blend is the melting point of PEO in different blend compositions, R is the universal gas constant, V 2 is the molar volume per repeat unit of semicrystalline component (PEO), V 1 is the molar volume per repeat unit of the diluent ( p 5PhS‐Li), and φ 1 is the volume fraction of p 5PhS‐Li. The following values were used to calculate the interaction parameter: V 2 = 39.3 cm 3 mol −1 that is obtained by using the density of amorphous PEO at room temperature, [ 31,32 ] = 8942 J mol −1 , [ 33,34 ] and V 1 = 174.6 cm 3 mol −1 based on the density of p 5PhS‐Li and molar mass of a repeat unit. The data from Figure S10, Supporting Information, are plotted according to Equation () in Figure .…”

“…[43,44] Unlike sulfonate anions, larger and more delocalized anions such as trifluoromethylsulfonyl imide (TFSI) have been shown to suppress PEO crystallinity. [16,34] It also exhibits increased ionic conductivity at room temperature due to charge delocalization. [16,45,46] The smaller and less charge-delocalized anions of p5PhS-Li and pSSLi are not expected to fully disrupt crystallinity of PEO, which is verified by DSC results.…”