Synthesis and characterization of reversible thermosensitive methylated chitin and its application in zinc‐ion battery thermal runaway

Abstract

Novel water‐soluble methylated chitins (MCHs) were synthesized homogeneously in aqueous alkaline solution. The relatively mild reaction conditions resulted in the MCH with high degree of acetylation (DA >0.76). The chemical structure of the obtained MCHs was analyzed and the degree of methylation substitution (DS) and DA were determined by proton NMR in both D2O and 20% DCl/D2O. The MCH aqueous solutions (DS = 0.46 ~ 0.71) showed a reversible thermosensitive sol–gel–sol transition upon heating and cooling. The gel transition temperature of these MCHs (in the range of 15–85 °C) increased with increasing DS and decreasing polymer concentration. Thermal runaway has been an important safety issue impeding the development of high‐energy‐density zinc‐ion batteries. A smart thermosensitive reversible electrolyte was prepared based on this MCH for the aqueous zinc‐ion battery to prevent thermal runaway. When the temperature of zinc‐ion battery rises or even gets out of control, the thermosensitive electrolyte can quickly gel and inhibit the migration of zinc ions, resulting in increase of the internal resistance and realizing intelligent and efficient thermal self‐protection. Thus the novel thermosensitive methylated chitin shows promise for safe aqueous zinc‐ion batteries.

A Review of the Synthesis of Biopolymer Hydrogel Electrolytes for Improved Electrode–Electrolyte Interfaces in Zinc-Ion Batteries

“…The gelation process inhibited ion transfer and controlled reaction speed. ZIBs with this electrolyte and α-MnO 2 cathode demonstrated decreased capacity from 143.9 mAh g −1 at 35 • C to 2.4 mAh g −1 at 75 • C, with an energy density decrease from 199.7 Wh kg −1 to 2.4 Wh g −1 for the same temperature change [110].…”

“…A thermosensitive reversible electrolyte was prepared using modified chitin for the development of aqueous ZIBs, preventing thermal runaway by changing to a gel state at higher temperatures, inhibiting zinc ion migration [110]. The electrolyte was prepared by dissolving chitin in an aqueous solution of 11 wt% NaOH and 4 wt% urea, followed by the addition of iodomethane [110].…”

“…A thermosensitive reversible electrolyte was prepared using modified chitin for the development of aqueous ZIBs, preventing thermal runaway by changing to a gel state at higher temperatures, inhibiting zinc ion migration [110]. The electrolyte was prepared by dissolving chitin in an aqueous solution of 11 wt% NaOH and 4 wt% urea, followed by the addition of iodomethane [110]. Subsequently, the methylated chitin was dissolved in a 20 wt% NaOH aqueous solution, then iodomethane was added at 20 • C, followed by neutralization, dialysis, and freeze drying [110].…”

“…The electrolyte was prepared by dissolving chitin in an aqueous solution of 11 wt% NaOH and 4 wt% urea, followed by the addition of iodomethane [110]. Subsequently, the methylated chitin was dissolved in a 20 wt% NaOH aqueous solution, then iodomethane was added at 20 • C, followed by neutralization, dialysis, and freeze drying [110]. The electrolyte, produced by dissolving the prepared methylated chitin in distilled water and mixing it with 2 M ZnSO 4 and 0.1 M MnSO 4 , exhibited reversible temperature responsiveness, attributed to the hydrogen bonding and interaction of functional groups [110].…”

“…Subsequently, the methylated chitin was dissolved in a 20 wt% NaOH aqueous solution, then iodomethane was added at 20 • C, followed by neutralization, dialysis, and freeze drying [110]. The electrolyte, produced by dissolving the prepared methylated chitin in distilled water and mixing it with 2 M ZnSO 4 and 0.1 M MnSO 4 , exhibited reversible temperature responsiveness, attributed to the hydrogen bonding and interaction of functional groups [110]. The gelation process inhibited ion transfer and controlled reaction speed.…”