The application of sodium alginate-chitosan hydrogel electrolyte in aqueous zinc-ion batteries

In this paper, sodium alginate and chitosan, two natural polymer materials, were used to prepare gel electrolyte through one-step synthesis, aiming to reduce the disordered growth of zinc dendrites and the occurrence of side reactions, and improve the cycle life and electrochemical performance of aqueous zinc ion batteries. The microstructure of the gel electrolyte was analyzed by Fourier transform infrared spectroscopy and scanning electron microscopy. Its porous structure can promote the transport of ions, and the ionic conductivity is 27.02 mS·cm⁻¹. The gel electrolyte was assembled into symmetrical cells, Zn-Mn full cells and Zn-Cu half cells, and electrochemical tests were carried out. The symmetrical cell had a long cycle life of 2400 hours at 1 mA·cm⁻² and 0.5 mAh·cm⁻², and the zinc ion transference number was 0.57. After 300 cycles, the full cell with CA gel electrolyte still had a large specific capacity. In contrast, the specific capacity of the separator battery decayed to 104 mAh·g⁻¹. The CE measurement of Zn||Cu half cells was carried out using batteries with ordinary separators and CA gel electrolyte. The battery with gel electrolyte showed stable CE, and the cycle life exceeded 700 hours. It had excellent long-cycle performance, and the average CE of the battery with gel electrolyte was as high as 99.7% after more than 700 cycles. In contrast, the CE of the battery with ordinary separator fluctuated sharply after more than 200 hours of cycling. In conclusion, a gel electrolyte that can significantly improve the performance of water system zinc ion battery was successfully synthesized in this paper.