Succinonitrile-Polymer Composite Electrolytes for Li-Ion Solid-State Batteries-The Influence of Polymer Additives on Thermomechanical and Electrochemical Properties

Vanessa van Laack; Frederieke Langer; Andreas Hartwig; Katharina Koschek

doi:10.1021/acsomega.2c02174

Succinonitrile-Polymer Composite Electrolytes for Li-Ion Solid-State Batteries-The Influence of Polymer Additives on Thermomechanical and Electrochemical Properties

ACS Omega. 2023 Mar 2;8(10):9058-9066. doi: 10.1021/acsomega.2c02174. eCollection 2023 Mar 14.

Authors

Vanessa van Laack^{1

2}, Frederieke Langer³, Andreas Hartwig^{1

2}, Katharina Koschek^{1

2}

Affiliations

¹ Adhesive Bonding Technology and Surfaces, Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Wiener Straße 12, 28359Bremen, Germany.
² Department of Biology/Chemistry, University of Bremen, Leobener Straße 3, 28359Bremen, Germany.
³ Electrical Energy Storage, Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Lilienthalplatz 1, 38108Braunschweig, Germany.

Abstract

A plastic crystalline electrolyte (PCE) consisting of 0.4 mol/L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in succinonitrile (SN) was blended with poly(ethylene oxide) (PEO), poly(vinylpyrrolidone) (PVP), poly(ethylene carbonate) (PEC), and polyacrylonitrile (PAN). The influences of the regarding polymers on thermomechanical properties of the PCE were studied systematically, utilizing differential scanning calorimetry, thermogravimetric analysis, and oscillation experiments. Depending on the chosen polymer, the melting temperature and overall crystallinity of the PCE were increased. For PCEs containing PEO and PVP, overall crystallinity was enhanced the most resulting in lamellae-like superstructures, identified by light microscopy images. Furthermore, the onset for the sublimation process of SN was shifted to higher temperatures, and the mechanical strength was increased by the presence of some polymers, with exception of PEC. Electrochemical characterization, including electrochemical impedance spectroscopy and linear sweep voltammetry, revealed ionic conductivities of 10^-4 S/cm at room temperature for PCE with PAN and extended electrochemical stability windows of ≥4.5 V vs lithiated graphite for PCE with PEO. By correlating the thermomechanical and electrochemical properties, some structure-property relationships were drawn, pointing out great potential for specific tailoring of PCEs by polymer additives. The synergistic effect of increasing both, mechanical stability and ionic conductivity, made the PCE + PAN composition especially attractive for a possible application in batteries.