Green and Scalable Biopolymer‐Based Aqueous Polyelectrolyte Complexes for Zinc‐Ion Charge Storage Devices

Abstract

Green and scalable materials are essential to fulfill the need of electrification for transitioning into a fossil‐fuels free society, and sustainability is a requirement for all new technologies. Rechargeable batteries are one of the most important elements for electrification, enabling the transition to mobile electronics, electrical vehicles and grid storage. We here report synthesis and characterization of polyelectrolyte complexes of alginate and chitosan, both biopolymers deriving from the sea, for transport of zinc ions in hydrogel electrolytes. We have used vibrational spectroscopy, thermal measurements and microscopy, as well as transport measurements with ohmic or blocking contacts. The transference number for zinc ions is close to 1, the conductivity is ≈10 mS/cm, with stability at Zn interfaces seen through 7000 cycles in symmetric zinc//zinc cell.

Algae-Based Biopolymers for Batteries and Biofuel Applications in Comparison with Bacterial Biopolymers—A Review

“…Blending alginate with chitosan and doping the blend with ZnCl 2 ( Figure 9 ), Fernández-Benito et al prepared an aqueous zinc ion polyelectrolyte with a conductivity of approx. 10 −3 S/cm and high electrochemical cyclability of over 7000 cycles [ 145 ].…”

“… ( A ) The sequential view of the compact polyelectrolyte complexes’ preparation route; ( B ) the ideal view of the ionic interactions between the polyelectrolyte chains and the ions involved in the synthesis of the coacervate (X + =H + ; Y − =CH 3 COO − ). From [ 145 ], originally published under a CC-BY license. …”

“…Blending alginate with chitosan and doping the blend with ZnCl2 (Figure 9), Fernández-Benito et al prepared an aqueous zinc ion polyelectrolyte with a conductivity of approx. 10 −3 S/cm and high electrochemical cyclability of over 7000 cycles [145]. Another algal biopolymer that has been investigated as a potential electrolyte for batteries is an agarose matrix with concentrated KOH as a liquid electrolyte for zinc-air batteries, amongst others [146].…”

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

“…The full cell delivered a capacity of 238.6 mAh g −1 and a capacity retention of 94.5% after 900 cycles at 2 A g −1 (Figure 8) [115]. Alginate was also combined with chitosan in research on the development of green and scalable hydrogel electrolytes for ZIBs (Figure 9) [117]. The hydrogel solutions were created through microfluidic mixing of aqueous solutions of sodium alginate and chitosan with ZnCl2 salt, followed by centrifugation to concentrate and separate the hydrogel electrolyte [117].…”

“…The hydrogel solutions were created through microfluidic mixing of aqueous solutions of sodium alginate and chitosan with ZnCl2 salt, followed by centrifugation to concentrate and separate the hydrogel electrolyte [117]. The produced hydrogel electrolyte had an ionic conductivity of about 10 mS cm −1 and demonstrated a stable interface with Zn electrodes in a symmetric cell, operating for more than 7000 galvanostatic cycles [117]. In another study, a hydrogel was prepared with sodium alginate, guar gum, and ethylene glycol to create flexible and anti-freezing ZIBs [116].…”