Preparation and Properties of Cellulose/Polyether Ketone Composite Membrane
With the development of the society,the demand for energy is increasing.The excessive exploitation of petrochemical resources results in fewer and fewer exploitable resources,and also brings a series of problems such as climate change,environmental pollution and so on Applying renewable resources to replace part of petrochemical resources and developing new green energy are the key to solve the problems.Fuel cells and lithium-ion batteries are typical representatives in the field of new energy sources.The membrane is one of the key components in fuel cell and lithium battery.In the field of fuel cells,Nafion proton exchange membranes has been applied wildly which have excellent mechanical properties,good chemical stability and relatively high proton conductivity.However,its application is limited due to its complex synthesis process,high cost,high methanol permeability and easy swelling in high temperature working environment.In the field of lithium batteries,PE and PP membranes are the representatives.Polyolefin membranes have the advantages of high mechanical strength,good chemical stability and low cost.However,polyolefin membranes have some disadvantages,such as low polarity,poor affinity with electrolytes and poor thermal stability.In order to solve these problems,the renewable biomaterial:cellulose,and high performance polymers:poly(aryl ether ketone)with excellent mechanical properties and good chemical stability were applied in proton exchange membranes and lithium battery separators.First,proton conductivity improvement effect of cellulose on sPEEKK based PEMs with excellent dimensional stability and high proton conductivity was studied.Second,nanocellulose reinforced proton exchange nanocomposite membranes coated with TEOS which has high water absorption,high proton conductivity and excellent dimensional stability were studied.Third,PE@P7C separator membranes with high discharge specific capacity,good rate performance and thermal stability were prepared and studied.At last,PE@PEEK separator for lithium-ion batteries presented excellent thermal stability,good coulomb efficiency and long-cycle life was prepared and studied.The research contents are as follows:(1)In order to improve the dimensional stability and proton conduction efficiency of the proton exchange membrane at high temperature,cellulose was introduced into the sPEEKK proton exchange membrane system.Cellulose was entangled with sPEEKK in molecular state through hydrogen bonds,so as to greatly improve the dimensional stability of the composite membrane at high water absorption rate.Since the hydroxyl group on the cellulose and the sulfonic acid group of sPEEKK are hydrophilic groups,the proton conductivity of the composite proton exchange membrane is significantly improved,and the proton conduction mechanism of the composite membrane is clarified.(2)In order to improve the sPEEKK the wateruptake and proton conductivity of proton exchange membrane,sPEEKK proton exchange membrane was enhanced by amino modified nanocrystellulost(NN),and the water absorption of the composite membrane was further improved by TEOS coating.The effects of nanocrystalline cellulose(CNC),amino modified nanocrystalline cellulose(NN)and TEOS coatings on mechanical properties,dimensional stability and proton conductivity of sPEEKK proton exchange membrane were investigated,and the proton conduction mechanism was determined.(3)To improve the thermal stability of PE seperator,PE@PEEK separator with high thermodynamic stability was prepared by phase transformation method.The study showed that PEEK coating significantly improved the thermal stability of PE,and the thermal shrinkage rate of composite membrane was less than 10%when treated at 200 ℃ for 0.5h.Furthermore,because the ether bond and ketone bond on PEEK have good interaction with electrolyte solution,PE@PEEK has better battery performance than PE membrane.(4)To improve the electrical conductivity between dielectric material PEEK and electrode materials,which is useful for improving the utilization efficiency of batteries,different content of carbon nanoparticles from cellulose was applied as a conductive agent.The effects of different content of cellulose based carbon nanoparticles as conductive agents on the surface morphology,thermal shrinkage,electrolyte solution infiltration,initial battery efficiency,battery cycling performance and battery rate performance of PE@PEEK composite film were studied.The experimental results showed that the addition of carbon nanoparticles help to improve the performance of PE separator for initial charge-discharge efficiency,and improve the rate performance.