Abstract
<title>Abstract</title> <p>The practical operation of aqueous zinc-ion batteries is often limited by insufficient ion transport, water-induced interfacial reactions, and uneven Zn deposition. To address these issues, oxidized sodium alginate (OSA) was introduced into a polyacrylamide (PAM) matrix to form a functional hydrogel electrolyte. At an OSA loading of 0.9 g per batch, the resulting PAM OSA-0.9 hydrogel developed a more open porous structure and showed improved wettability. Compared with the unmodified PAM electrolyte, its ionic conductivity increased from 16.2 to 28.6 mS cm⁻¹, and its apparent Zn²⁺ transference number increased from 0.88 to 0.93. The electrochemical stability window was also extended from 2.47 to 2.64 V. Meanwhile, hydrogen evolution and Zn corrosion were alleviated, and the Zn nucleation and deposition processes became more uniform. As a result, Zn//Zn symmetric cells operated continuously for 1300 h at 1.0 mA cm⁻² and 1.0 mAh cm⁻². In Zn//NaV₃O₈·xH₂O full cells, 79% of the capacity was retained after 220 cycles at 1.0 A g⁻¹, while 58% remained after 3500 cycles at 5.0 A g⁻¹. These findings show that OSA can simultaneously improve ionic transport and interfacial stability in PAM-based hydrogel electrolytes, thereby supporting durable aqueous Zn batteries.</p>