Carboxymethyl cellulose as artificial solid/electrolyte interphases and separator for Zn-based battery

Abstract

As the quest for robust large-scale energy storage systems (EESs) intensifies, aqueous rechargeable zinc-based batteries are gaining traction for grid-scale applications due to their high theoretical capacity and safety. Despite this, their practical application is compromised by several zinc anode issues, including hydrogen evolution, corrosion, dendritic growth, and passivation. An artificial solid electrolyte interphase (ASEI) using polyelectrolytes, such as carboxymethyl cellulose (CMC), is emerging as a solution, offering economic and environmental advantages. CMC's structure, enriched with carboxyl groups, allows for the refined management of zinc ion distribution at the electrode surface, promising enhanced surface stability. This study delves into CMC's role as ASEI in zinc-iodine batteries (ZIBs), examining its effect on both the zinc anode, fabricated from a zinc sheet, and a composite anode with integrated CMC in systems with a composite carbon-iodine cathode. A novel CMC and polyvinyl alcohol (PVA) polyelectrolyte membrane, trialed in an electrochemical H-cell configuration, and CMC-coated carbon felt (CF) in a Zn-iodine flow battery, are also presented, highlighting their potential in enhancing battery operation. Our results show that a uniform CMC-ASEI layer mitigates side reactions and improves zinc ion distribution, with a Zn-CMC//I2 cell maintaining over 98% capacity after 2000 cycles at 5 mA/cm². The CMC/PVA membrane successfully prevents iodine and polyiodide migration, evidenced by over 300 stable cycles at 10 mA/cm² in an H-cell setup. Moreover, CMC-coated CF in a flow battery enhances zinc deposition, yielding more than 90% efficiency after 100 cycles at 80 mA/cm² and a capacity of 120 mAh/cm². These findings affirm CMC's vital role in advancing zinc-based battery technology, marking it as a key player for the next generation of EESs.