Alkali-tolerant polymeric gel electrolyte membrane based on cross-linked carboxylated chitosan for supercapacitors

Abstract

Tremendous efforts have recently been made in optimizing the electrolyte of flexible devices. Unfortunately, the bottleneck factors in electrolytes that largely limit the stability and applicability of devices have long been relatively neglected. Alkali-tolerant devices need alkali-tolerant hydrogel electrolyte as an essential component, while most hydrogels will lose their stability after being immersed with strong alkaline solution. This is why alkali-tolerant quasi-solid supercapacitors have less been reported so far. In this work, an alkali-tolerant hydrogel electrolyte membrane based on carboxylated chitosan hydrogel electrolyte membrane is fabricated through graft co-polymerization and crosslinking among acrylic acid, N, N′-methylene bisacrylamide, and potassium persulfate, followed by intense uptake of KOH electrolyte. In addition, we make an extension of the above work and prepare another hydrogel electrolyte membrane by selecting FeCl3 as crosslinking agent using the same method. The prepared alkali-tolerant hydrogel electrolyte membranes present obviously improved properties compared to PAAS electrolyte in terms of ionic conductivity (at room temperature) and electrolyte uptake. The quasi-solid supercapacitor in alkaline electrolyte exhibits admirabl eenergy density and power density (4.39 Wh kg−1 and 224.99 W kg−1, respectively), while has relatively low energy density and power density (3.77 Wh kg−1 and 225.00 W kg−1, respectively). Gratifyingly, the polymeric gel electrolyte can also be applied in acidic and neutral electrolytes. Our results highlight the potential of the alkali-tolerant hydrogel electrolyte to be widely used in next-generation alkaline energy devices.