In Situ Dendrimer-Crosslinked Gel Polymer Electrolytes for Lithium-Ion Batteries with High Ionic Conductivity and Excellent Electrochemical Performance

Previous studies have proven that using chemically crosslinked gels as a polymer host in gel polymer electrolytes (GPEs) has many advantages, including enhanced mechanical properties and high ion conductivity as two important factors in the efficiency of produced polymer electrolytes in lithium-ion batteries (LIBs). Several studies have been conducted on the preparation of crosslinked polymer electrolytes and many crosslinking agents have been used. Meanwhile, dendrimers as attractive multifunctional structures can be used with some structural modifications as practical options for crosslinking of a polymeric host in GPEs. The use of such structures in the production of polymer networks can not only improve the mechanical properties but also enhance the stability and electrochemical properties of GPEs. In the present work, poly(amidoamine) dendrimers have been synthesized in different generations of 0.0GD to 4.0GD, and then each generation has been transformed into a multifunctional branched crosslinker through surface modification by acryloyl chloride and subsequently creating reactive vinyl groups. Then, the synthesized crosslinker dendrimers were introduced into the poly(poly(ethylene glycol) methyl ether methacrylate) (poly(PEGMA)) matrix by in situ polymerization. The accuracy of synthesis in each step was proved through Fourier-transform infrared (FT-IR) and 1H NMR spectroscopies. Also, the synthesized poly(PEGMA) films were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). Moreover, dynamic shear rheometry was utilized to investigate the rheological behavior of prepared gel polymers and confirm the formation of gel polymer membranes. The prepared GPEs presented excellent electrochemical properties, including high ionic conductivity on the order of 10–2 S cm–1, considerable transference number of 0.65, a wide electrochemical stability window of up to 5 V vs Li/Li+, and low interfacial resistance. Also, they showed excellent cycling performance and a high specific capacity of 185 mAh g–1 in an LCO||Li cell.