Demand for flexible energy storage devices is rapidly increasing due to the development of new wearable and flexible electronics. These developments require improved integration of energy storage devices to meet the design specifications of these products. Polymer hydrogels are an alternative class of flexible electrolytes that can be used in power source systems. Herein, we present a new sustainable hydrogel electrolyte material made with apple pectin. Using an easy solution casting approach, a bio-based hydrogel was formed via pectin gelation. The resultant hydrogel was made with environmentally benign compounds including water, zinc and/or lithium sulfate salt, and a bio-based polymer. This hydrogel electrolyte exhibits ambient temperature ionic conductivities that are similar to those found in aqueous liquid electrolytes (∼5 × 10 −2 S cm −1 ), depending on electrolyte hydration. Its wide thermal stability window enables the electrolyte to be used at both low temperatures (−20 °C) and intermediate temperatures (50 °C), without significant changes in ionic conductivity (>10 −3 S cm −1 ). By proposing an energy-oriented solution using one of the food industry's major waste materials, we report a novel approach to processing a bio-based polymer for energy storage purposes.

With the increase of portable power sources demand, new technologies, e.g. wearable and flexible electronics, are projected to generate $1.25 billion market by 2022.[1] New storage energy devices are more than ever in demand which requires new specifications in order to be used in those future applications. To achieve this development, we have to minimize the environmental impact in the whole battery life cycle, from conception to degradation of the system, and reduce production costs. Polymer hydrogel electrolyte are one of the promising alternative for processing new flexible batteries.[2] A great hydrogel electrolyte should promise excellent ionic transport pathways and sufficient mechanical strength, not to cause short-circuits. As a matter of fact, hydrogel electrolytes are well-known for their good ionic conductivity. Nevertheless, the original polymers used in these systems don’t take into account the cost of the environmental impact and safety due to the processing or biodegradability of those hydrogels.[3] In this study, we report a new hydrogel-based electrolyte material made by apple pectin. This presentation will mainly focus on the interactions between pectin functional groups, water and ions using solid NMR spectroscopy. Thermal properties will be discussed based on differential scanning calorimetry analysis. Electrical and electrochemical characterisctics obtained by electrochemical impedance spectroscopy, galvanostatic cycling and cyclic voltametry will demonstrate the applicability of such hydrogel electrolyte. This study could promote a great innovation in the energy storage field, by recycling one of apple peel’s component (which is the main waste in preserves manufacturing[4]) into a hydrogel electrolyte. References [1] N. R. C. Canada in Environmentally friendly printed batteries, Vol. Boucherville, Quebec, 2021. [2] C. Y. Chan, Z. Wang, H. Jia, P. F. Ng, L. Chow and B. Fei, Journal of Materials Chemistry A 2021, 9, 2043-2069. [3] Y. Huang, M. Zhong, F. Shi, X. Liu, Z. Tang, Y. Wang, Y. Huang, H. Hou, X. Xie and C. Zhi, Angewandte Chemie International Edition 2017, 56, 9141-9145. [4] B. S. Virk and D. S. Sogi, International Journal of Food Properties 2004, 7, 693-703.