Application of Coffee Silverskin Cellulose/Polyacrylamide Gel Polymer Electrolytes for Rechargeable Zinc-Ion Batteries

Rechargeable zinc-ion batteries (ZIBs) have grown in popularity due to their low cost and the abundance of resources. However, there has been little research into the development of gel polymer electrolytes (GPEs) for high voltage and capacity ZIBs. The use of agricultural waste as a polymer electrolyte (PE) is gradually increasing in order to support a circular economy. This study focuses on the utilization of cellulose derived from coffee silverskin (CS); coffee silverskin is a by-product generated during coffee roasting. We employ a reasonable approach to create the coffee silverskin cellulose (CSC)/polyacrylamide (PAM) GPE, with the goal of achieving good properties and improved battery performance. An investigation was conducted to determine the effect of CSC content in GPEs on ZIB characteristics. The cellulose derived from CS had a crystallinity index (CrI) of 64.60%. The optimal amount of cellulose added to the acrylamide monomer (AM) for the GPE of ZIB was found to be 2.5 mg (CSC/AM/salt weight ratio of 0.01/6/23). This amount resulted in the highest electrochemical stability and a cycling time of approximately 226 h. Furthermore, the PAM/Cellulose 2.5-based GPE exhibited increased Young’s modulus and tensile strength compared to the pure PAM. The electrochemical impedance spectroscopy (EIS) test revealed a diffusion resistance of 27.47 Ω and an ionic conductivity of 9.10 mS/cm at a temperature of 25 °C. Additionally, the use of cellulose in GPEs does not affect the electrochemical window. When the pure PAM-based GPE was compared to the CSC/PAM-based GPE, the biocomposites demonstrated electrochemical stability for a cycle life of over 200 cycles in the ZIB application.