A supramolecular gel polymer electrolyte based on poly(vinyl alcohol) and tannic acid for flexible electrical double layer capacitors

Gel polymer electrolytes (GPEs) for flexible electrical double-layer capacitors (EDLCs) have gained significant attention due to their flexibility and security. However, it remains a great challenge to in situ prepare poly(vinyl alcohol) (PVA)/tannic acid (TA)-based GPEs, which is limited by the strong hydrogen bonds between PVA and TA. Herein, a novel strategy is proposed to in situ fabricate PVA/TA-based GPEs by using ethylene glycol (EG) and H2O as the binary solvent. The EG molecules disturb and weaken the hydrogen bonds, paving the way for the successful preparation of PVA/TA-based GPEs. The optimized GPE shows excellent mechanical properties, flexibility, and an ionic conductivity of 106.9 mS cm−1. The carbon-based solid-state EDLC containing this GPE delivers a voltage window of 0–2 V, an energy density of 21.3 Wh kg−1 at a power density of 480 W kg−1, and specific capacitance retention of around 90% after 10,000 charge/discharge cycles. Moreover, the corresponding flexible solid-state EDLC demonstrates acceptable bendability and robust serviceability. This work may provide a universal strategy for in situ preparation of PVA/TA-based gels in energy storage and other related fields.