Abstract
The trend of research towards more sustainable materials is pushing the application of biopolymers in a variety of unexplored fields. In this regard, hydrogels are attracting significant attention as electrolytes for flexible electrochemical devices thanks to their combination of ionic conductivity and mechanical properties. In this context, we present the use of cellulose-based hydrogels as aqueous electrolytes for electrochemical devices. These materials were obtained by crosslinking of hydroxyethyl cellulose (HEC) with divinyl sulfone (DVS) in the presence of carboxymethyl cellulose (CMC), creating a semi-IPN structure. The reaction was confirmed by NMR and FTIR. The small-amplitude oscillatory shear (SAOS) technique revealed that the rheological properties could be conveniently varied by simply changing the gel composition. Additionally, the hydrogels presented high ionic conductivity in the range of mS cm−1. The ease of synthesis and processing of the hydrogels allowed the assembly of an all-in-one electrochromic device (ECD) with high transmittance variation, improved switching time and good color efficiency. On the other hand, the swelling ability of the hydrogels permits the tuning of the electrolyte to improve the performance of a printed Zinc/MnO2 primary battery. The results prove the potential of cellulose-based hydrogels as electrolytes for more sustainable electrochemical devices.
Highlights
Wearable electronics with specific features are of increasing interest in applications such as medical sensing devices and smart labels in the frame of the rising of Internet of Things (IoT) [1]
We present the synthesis of self-standing cellulose-based hydrogels and their application as electrolytes for electrochemical devices
The reaction proceeded by the dissolution of carboxymethyl cellulose (CMC) and hydroxyethyl cellulose (HEC) in alkaline aqueous media (12 < pH < 13), followed by the addition of the crosslinking agent (DVS)
Summary
Wearable electronics with specific features (miniaturizing, flexibility and custom shape) are of increasing interest in applications such as medical sensing devices and smart labels in the frame of the rising of IoT [1] These systems include several flexible electrochemical devices (i.e., sensors, batteries, electrochromic, electronics), whose performance is not affected under different mechanical stresses [2]. These technologies rely on soft and flexible materials where hydrogels have shown up as promising electrolyte systems [3,4] These materials consist of tridimensional polymer networks that can accommodate a large amount of water within the interstices of the structure, mainly through polar or ionic bonding from functional groups in the backbone [5,6]. The most widely used polymeric materials as a hydrogel matrix are composed of synthetic monomers
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