Recyclable High‐Performance Polymer Electrolyte Based on a Modified Methyl Cellulose–Lithium Trifluoromethanesulfonate Salt Composite for Sustainable Energy Systems

Although energy‐storage devices based on Li ions are considered as the most prominent candidates for immediate application in the near future, concerns with regard to their stability, safety, and environmental impact still remain. As a solution, the development of all‐solid‐state energy‐storage devices with enhanced stability is proposed. A new eco‐friendly polymer electrolyte has been synthesized by incorporating lithium trifluoromethanesulfonate into chemically modified methyl cellulose (LiTFS–LiSMC). The transparent and flexible electrolyte exhibits a good conductivity of near 1 mS cm−1. An all‐solid‐state supercapacitor fabricated from 20 wt % LiTFS–LiSMC shows comparable specific capacitances to a standard liquid‐electrolyte supercapacitor and an excellent stability even after 20 000 charge–discharge cycles. The electrolyte is also compatible with patterned carbon, which enables the simple fabrication of micro‐supercapacitors. In addition, the LiTFS–LiSMC electrolyte can be recycled and reused more than 20 times with negligible change in its performance. Thus, it is a promising material for sustainable energy‐storage devices. Reuse and recycle: A Li‐ion polymer electrolyte based on modified cellulose composited with lithium trifluoromethanesulfonate is developed (LiTFS–LiSMC). The electrolyte is highly transparent and flexible and has excellent ion transport properties. The compatibility of the electrolyte with standard carbon electrodes is excellent, thus, a high‐performance micro‐supercapacitor is fabricated. Additionally, the electrolyte and the supercapacitors are recyclable.