Multifunctional\nMolecular Design as an Efficient Polymeric Binder for Silicon Anodes\nin Lithium-Ion Batteries

Abstract

This work demonstrates the design,\nsynthesis, characterization, and study of the electrochemical performance\nof a novel binder for silicon (Si) anodes in lithium-ion batteries\n(LIBs). Polymeric binders with three different functional groups,\nnamely, carboxylic acid (COOH), carboxylate (COO^–), and hydroxyl (OH), in a single polymer backbone have been synthesized\nand characterized via ¹H NMR and FTIR spectroscopies. A\nsystematic study that involved varying the ratio of the functional\ngroups indicated that a material with an acid-to-alcohol molar ratio\nof 60:40 showed promise as an efficient binder with an initial columbic\nefficiency of 89%. This exceptional performance is attributed to the\nstrong adhesion of the binder to the silicon surface and to cross-linking\nbetween carboxyl and hydroxyl functional groups, which minimize the\ndisintegration of the Si anode structure during the large volume expansion\nof the lithiated Si nanoparticle. Polymers with multiple functional\ngroups can serve as practical alternative binders for the Si anodes\nof LIBs, resulting in higher capacities with less capacity fade.