Superior performances of supercapacitors and lithium-ion batteries with carboxymethyl cellulose bearing zwitterions as binders

Background: The zwitterionic effect on binder material remains unclear. Methods: We propose that carboxymethyl cellulose (CMC) is subjected to oxa-Michael addition with sulfobetaine methacrylate (SBMA) to fabricate CMC-SBMA as binders for supercapacitor and lithium-ion battery. CMC-SBMA is certified by ¹H nuclear magnetic resonance spectra with the grafting fraction of 40.5%. Significant findings: With zwitterionic modification, the activation energy and limiting molar conductivity of CMC-SBMA polymer electrolyte will respectively decrease to 0.058 eV and increase to 61 S.cm²/mol. Because zwitterion segment can simultaneously provide quaternary ammonium and sulfonic group respectively for electron and lithium-ion receptions, CMC-SBMA applied as binder of graphite anode for lithium-ion battery shows an extra discharging voltage plateau at 3.35 V and high specific capacitance of 140 mAh/g (LiFePO₄). Meanwhile, both less decomposition of electrolyte and low reduction potential during solid electrolyte interface formation process are observed. CMC-SBMA is also applied as the binder of activated carbon electrode for supercapacitor showing low internal resistance, low diffusion parameter of 0.03, and high specific capacitance of 277.9 F/g. This study is the first to demonstrate that CMC-SBMA as a binder regulates ion transportation for the superior performance of energy storage devices.