Mechanically robust, anti-freezing, and dual cross-linked alginate-polyacrylamide hydrogel electrolyte for flexible zinc ion hybrid capacitors (ZHCs) with enhanced wide temperature range
摘要
Flexible energy storage devices are widely integrated into wearable electronics due to their shape conformability, high performance, and environmental friendliness. Among them, flexible zinc ion hybrid capacitors, constructed with hydrogel electrolyte, are preferred for their high specific capacity and flexibility. However, conventional hydrogel fails in subzero temperatures. Here, we fabricated a dual cross-linked hydrogel electrolyte (named as SAP) by integrating sodium alginate and polyacrylamide, which exhibit impressive mechanical properties with a compression strength of 2.38 MPa and a compressive strain at break of 95%. The corresponding hydrogel electrolyte displays high ionic conductivity of 22.22 ± 0.50 mS cm−1 at 25 °C and 5.33 ± 0.17 mS cm−1 even at a low temperature of − 35 °C alongside excellent electrochemical stability and reversibility. The assembled Zn@ hydrophilic carbon cloth (CC) | SAP-1.5 | activated carbon (AC) @CC capacitors show remarkable electrochemical performance with the initial specific capacities of 48.2 mAh g−1 (25 °C), 56.5 mAh g−1(50 °C), and 24.5 mAh g−1 (− 20 °C) at 1 A g−1, retaining 94.6, 93.8, and 90.7% of initial capacity after 10,000 cycles. Furthermore, the device performs normally under varied bending angles, confirming its potential as a flexible energy storage solution across wide temperature ranges.