Carboxymethyl Cellulose – Polyvinyl Alcohol Composite-Based Gel Polymer Electrolyte for Rechargeable Zn-Air Batteries

Abstract

The high ionic conductivity, lower interfacial contact resistance, enhanced safety, non-toxicity, and biodegradability bring the gel polymer electrolytes (GPEs) as a prospective electrolyte for applications in high-energy density flexible Zn-air batteries (ZABs). The present study comprehensively optimizes the procedures to obtain carboxymethyl cellulose (CMC)–polyvinyl alcohol (PVA) composite-based GPEs holding a maximum KOH amount in the polymer matrix. Optimization of the GPE has been performed and demonstrated by an in-house-developed rechargeable ZAB cells using MnO2-based air cathode and Zn anode. The optimization parameters include the ratio of PVA:CMC, concentration of PVA-CMC in DI water, and thickness of the gel polymer electrolyte. Results show that a 4mm thick GPE prepared from a polymer membrane synthesized using PVA:CMC ratio of 5:2 at a concentration of 0.063 g ml−1 in DI water displayed the highest 6M KOH uptake, least charge transfer resistance of the device, higher discharge plateau, and 5–6 times more cycling compared to GPE made of PVA only. The “as-synthesized GPE” demonstrates high stability of GPE over 100h for a Zn-air battery device. The findings of this work shall speed up the development of Zn air batteries for applications as energy storage systems.