Triple-Function Electrolyte Regulation toward Advanced Aqueous Zn-Ion Batteries

The poor Zn reversibility has been criticized for limiting applications of aqueous Zn-ion batteries (ZIBs); however, its behavior in aqueous media is not fully uncovered yet. Here, this knowledge gap is addressed, indicating that Zn electrodes face a O-2-involving corrosion, besides H-2 evolution and dendrite growth. Differing from aqueous Li/Na batteries, removing O-2 cannot enhance ZIB performance because of the aggravated competing H-2 evolution. To address Zn issues, a one-off electrolyte strategy is reported by introducing the triple-function C3H7Na2O6P, which can take effects during the shelf time of battery. It regulates H+ concentration and reduces free-water activity, inhibiting H-2 evolution. A self-healing solid/electrolyte interphase (SEI) can be triggered before battery operation, which suppresses O-2 adsorption corrosion and dendritic deposition. Consequently, a high Zn reversibility of 99.6% is achieved under a high discharge depth of 85%. The pouch full-cell with a lean electrolyte displays a record lifespan with capacity retention of 95.5% after 500 cycles. This study not only looks deeply into Zn behavior in aqueous media but also underscores rules for the design of active metal anodes, including Zn and Li metals, during shelf time toward real applications.

Automated summary

This study reveals the challenges in aqueous Zn-ion batteries and proposes a new electrolyte strategy to address these issues. Experimental results demonstrate that the strategy can achieve high reversibility and long lifespan for Zn-ion batteries.