Preparation and characterisation of chitosan extracted from shrimp shell ( Penaeus monodon) and chitosan-based blended solid polymer electrolyte for lithium-ion batteries

A bioactive and non-toxic biopolymer-based electrolyte has gained attention in recent research for their potential applications in the fabrication of electrochemical devices. In this work, we extracted the chitosan successfully prepared from shrimp shells using Brine’s method. The solid polymer electrolyte comprising the blend of chitosan and agar–agar, plasticised with polyethylene glycol (PEG), as host polymer and lithium perchlorate (LiClO4) as a dopant is prepared by solution casting technique. Also, the effect of different weight percentage of the plasticiser PEG at a fixed ratio of perchlorate content is investigated. The obtained chitosan blended film is highly suitable as a electrolyte for electrochemical devices. The prepared polymer electrolyte is characterised using attenuated total reflection–Fourier transform infrared spectroscopy (ATR–FTIR), high-resolution scanning electron microscopy (HR–SEM), X-ray diffraction (XRD) and electrochemical impedance spectroscopy. The ATR–FTIR spectroscopy confirms the presence of particular functional groups present in chitosan and complex formation between blended polymers and lithium perchlorate. The surface morphology and amorphous crystallinity of chitosan and blended polymer electrolytes revealed from HR–SEM and XRD analysis. The ionic conductivity of the prepared materials is studied using AC impedance spectroscopy and compared. The highest ionic conductivity at room temperature obtained for the sample is 4.56 × 10−4 Scm−1 (CAP3). The mechanical properties of films have been studied using a Universal testing machine analysis. Wagner’s polarisation measurements have estimated the Li+ transport numbers of SPEs. Linear sweep voltammetry was performed on half-cell method to study the electrochemical stability window of the maximum ionic conductivity of SPEs.