Flexible and wrinkle-free electrode fabricated with polyurethane binder for lithium-ion batteries

Abstract

Flexible and wrinkle-free electrodes for flexible lithium-ion batteries (LIBs) are prepared with a polyurethane (PU) binder by casting a slurry on a glass substrate and detaching the subsequent film after drying. The flexible electrodes do not include a metal-foil current collector that would limit the LIB flexibility. The presence of both soft and hard segments in the PU structure gives the electrodes great flexibility and allows them to be folded without wrinkling or deforming. Adding multi-walled carbon nanotubes (MWNTs) to the electrodes simultaneously enhances the electrochemical properties (discharge capacity, rate capability, and cycling stability) and increases their mechanical strength (tensile strength). The flexible electrodes exhibit excellent electrochemical performance, which may be due to the enhanced electronic conductivity provided by the MWNT network in the electrode. The effects of PU content on the electrochemical performance are also investigated; it is found that a small amount of PU, approximately 11.5 wt%, is sufficient to fabricate the flexible electrode.