Because
of their high theoretical value of volumetric energy density,
excellent rate performance, and high level of safety, zinc–nickel
batteries (ZNBs) show potential applications for uninterrupted power
supply (UPS) systems. However, despite all the advantages of ZNBs,
the commercial application of ZNBs has been prevented by their short
lifetime caused by the shape change, the corrosion, and the dendrite
formation of the Zn anode. In this work, we proposed a flexible and
durable potassium polyacrylate (PAAK)–KOH gel polymer electrolyte
(GPE) prepared in a very simple way to solve the above problems of
the Zn anode. The obtained highly porous gel electrolyte showed higher
water retention, satisfying ionic conductivity (0.918 S cm–1), and a broad electrochemical stable voltage window. By providing
a stable and homogeneous electrode/electrolyte interface for the Zn
anode, the gel electrolyte can inhibit the uneven deposition and dendrite
formation. As a result, the gel electrolyte greatly prolonged the
cycling life to 776 h. In addition, because of the considerably batter
corrosion resistance of the Zn anode in the PAAK–KOH GPE, the
ZNB with gel electrolyte also exhibited a superior shelf life of more
than 431 h and a superior cycling performance under float charge for
more than 400 h at 60 °C. This work demonstrates that the gel
electrolyte with a simple preparation method is suitable for large-scale
practical production and can be successfully used in Zn–Ni
batteries as an electrolyte exhibiting excellent performance.