Biopolymer pectin with calcium ion crosslinker as biocompatiable electrolyte for energy storage applications

Abstract

Biopolymer electrolyte-based electrochemical devices for charge storage, such as supercapacitors and rechargeable batteries, attract wide attention. This study proposes that thin, transparent, and flexible polymer electrolytes can be fabricated using pectin, poly (ethylene glycol) (PEG), and calcium chloride (CaCl2) by solvent casting. CaCl2 plays a vital role as a crosslinker to form the film. The developed pectin/CaCl2 (PeO) and PEG/pectin/CaCl2 (PPe) polymer films are subjected to Fourier transform infrared analysis (FTIR) to confirm polymer matrix formation with the salt ions. The biopolymer membrane's glass transition temperature (Tg) is analyzed using differential scanning calorimetry (DSC). Symmetric supercapacitor devices were fabricated using activated carbon (AC) as electrode material, functionalized carbon fiber as a current collector, and pectin polymer films (PeO and PPe) as a gel electrolyte/separator. The symmetrical device with AC as the electrode and PPe as the electrolyte [AC||PPe||AC] exhibited a specific capacitance of 879 mF cm−2 at 15 mA cm−2, which is considerably higher than the similar device with PeO as electrolyte [AC||PeO||AC]. The cyclic stability of the [AC||PPe||AC] supercapacitor device was 83 % over 5000 cycles. Three supercapacitor devices connected in series is capable to glow 5 light-emitting diodes (LEDs). Good storage and stability indicate that the PPe is suitable as a gel polymer electrolyte material. This polymer electrolyte has excellent prospects in practical applications of all-solid-state, flexible, portable, and biocompatible energy storage devices.