Study Of Conducting Polymer-Gel Materials And Phosphate Based Organic Electrolyte For Electrochemical Energy Strorage

Energy development and climate change require people increase the development of sustainable and renewable resources.Electrical energy storage system is one of the most important energy storage system for the energy collection,storage and distribution.Amongst,Lithium ion batteries and electrochemical capacitors are two typical electrochemical energy storage systems.The electrochemical performance of Lithium ion batteries and electrochemical capacitors not only rely on the active electrode materials but also on the performance of electrolytes,separators,clean processes,efficient management protocols,etc.Herein,we design and synthesis conducting polymer PEDOT:PSS hydrogel and aerogel materials,investigated the related performance when PEDOT:PSS hydrogels applied as binders for lithium-ion batteries,the electrochemical performance of PEDOT:PSS aerogel as electrodes for electrochemical energy storage device.Furthermore,triethyl phosphate is investigated as solvent for organic electrolyte as a flame retardant electrolyte on electrical double layer capacitor.The main work is described as below:1.We show a simple mechanochemical conversion of a commercial PEDOT:PSS into a conducting polymer hydrogel.The key to the homogeneous hydrogel precursor formation is the result of slow incorporation of Fe³⁺ions that act as crosslinking agents within the polymer framework.The incorporation of iron was evidenced and quantified by energy dispersive X-ray spectroscopy?EDX?analysis.The analysis shows a linear dependence of the iron content with the ball milling time,consistent with the mechanism of slow oxidative dissolution of Fe⁰ from the stainless steel.The PEDOT:PSS ball milling induced hydrogel formation process is thus a simultaneous redox dissolution according to equation Fe⁰?Fe³⁺followed by PSS-/Fe³⁺coordination resulting in a cross-linked polymer network.This results in homogeneous and molecular level distribution of the Fe³⁺cross linker bridging the PSS?:PEDOT?chains.The formed hydrogel is mechanically robust and behaves as a tyxotropic fluid-appearance of a solid yet deformable under strain-even if containing a high water amount of about 98.7 wt%?e.g.1.3 wt%of PEDOT:PSS?.2.We design PEDOT:PSS 3D mesoporous aerogel electrodes through a simple and original one-pot mechanochemical route processing and super-critical point drying technique?CPD?.The hierarchical structure of neat PEDOT:PSS aerogels displays a highly interpenetrated porous conductive network with a record high active surface area of 470 m² g^-1 amongst the class of conducting polymer architectures.Robust structural and electrochemical performances are achieved with high gravimetric,areal and volumetric capacitance metrics of 120 F/g,2.5 F cm^-2,and 124 F cm^-3,respectively,as the result of a mixed hybrid faradai-capacitive charge storage mechanism.We undermine the fundamentals of the electrochemical operation in these electrodes and show that the electrolyte chemistry and the aerogel morphology particularly impact the charge storage performances demonstrating the superiority of the mesoporous architecture for charge transfer and ion exchange.Asymmetric cells are built having a specific capacitance of 40F/g based on the total mass of electrodes and a good cyclic stability with 90%capacitance retention after 1000 charge and discharge cycles.3.We show that mechanochemical conversion of a regular PEDOT:PSS water-based dispersion produces a hydrogel that meets all the requirements as binder for lithium-ion battery electrode manufacture.We particularly highlight the suitable slurry rheology,improved adhesion,intrinsic electrical conductivity,large potential stability window and limited corrosion of metal current collectors and active electrode materials,compared to standard binder or regular PEDOT:PSS solution-based processing.When incorporating the active materials,conductive carbon and additives with PEDOT:PSS,the mechanochemical processing induces simultaneous binder gelation and fine mixing of the components.The formed slurries are stable,show no phase segregation when stored for months,and produce highly uniform films in a single coating step,with no material segregation even upon slow drying.In conjunction with PEDOT:PSS hydrogels,technologically relevant materials including silicon,tin,and graphite negative electrodes as well as LiCoO₂,LiMn₂O₄,LiFePO₄,and carbon-sulfur positive electrodes show superior cycling stability and power-rate performances compared to standard binder formulation,while significantly simplifying the aqueous-based electrode assembly.4.The performance of organic electrolyte prepared by flame retardant triethyl phosphate solution for double layer capacitor was studied.The conductivity,viscosity,electrochemical stable voltage window performances of eletctrolytes with 1mol/L LiPF6in three solvent components:propylene carbonate,triethyl phosphate,propylene carbonate and triethyl phosphate mixture solvent are studied and compared.The results show that electrolyte with pure solvent riethyl phosphate?1M LiPF₆-TEP?has a wider electrochemical stable voltage window of 3.6V with balanced positive and negative electrode mass,while the electrolyte of 1M LiPF₆-PC only 3V,and the electrolyte with mixture solvent 1M LiPF₆-PC+TEP about 3.1V.