Sodium Alginate Reinforced PAAKS Hydrogel Electrolyte with Synergistically Enhanced Stretchability and Conductivity for Flexible Zinc–Air Batteries and Self-Powered Sensing

Abstract

Advanced human–machine interface technology demands flexible wearable electronics, including sensors and energy storage. Hydrogels, crucial to these devices, are often limited by poor toughness, cracking under strain, and low ionic conductivity. To address these issues, a high-performance composite hydrogel, PAAKS (as-prepared), was prepared by incorporating sodium alginate (SA) into an interpenetrating network. SA enhances mechanical properties, resulting in a tensile fracture energy of 1641 kJ·m–3, an elongation at break of 2260%, and a tensile strength of 5.5 kPa. It without KOH immersion, it boosts the ionic conductivity to 1.48 S·m–1, achieving synergistic optimization of strength, toughness, and conductivity. When used as an electrolyte in flexible zinc–air batteries (FZABs), the KOH-soaked PAAKS hydrogel enabled stable charge–discharge cycling for 33 h with a specific capacity of 798 mAh·g–1. Two series-connected batteries successfully power light-emitting diodes (LEDs) and electronic clocks. The hydrogel also demonstrated high sensitivity (gauge factor, GF = 2.28) as a strain sensor, detecting deformations from 1% to 600%, and functioned as a triboelectric nanogenerator with an open-circuit voltage of 11 V and a maximum power density of 0.027 W·m–2. This research offers new insights for designing hydrogel electrolytes and developing stable FZABs.