Preparation And Properties Of High-temperature Anhydrous Ion Conducting Nanocomposites Via Polymerization-induced Microphase Separation

To cope with the severe energy and environmental issues facing the current society,fuel cells and lithium-ion batteries have been attracting more and more attention as clean and efficient energy conversion and storage devices.As the key component of the batteries,the electrolytes which with excellent performance have always been a target pursued by researchers.Compared with traditional liquid-state electrolytes,solid-state electrolytes have been much accounted of their excellent chemical stability and safety.However,the existing commercially available solid-state electrolyte need to be in a mild environment to achieve better performance,which limits their application in batteries to a certain extent.The design of using the self-assembly of inorganic fillers and block copolymers to prepare polymer composite solid-state electrolyte with microphase separation structure has become a hotspot owing to combine the advantages of polymer substrates and fillers.As a kind of nanometer clusters with precise structure and excellent electrochemical performance,particularly,polyoxometalates（POM）possess broad application prospects in the solid-state electrolyte.Therefore,a facile,scalable and one-pot synthetic strategy for preparing high-temperature anhydrous ion-conducting nanocomposites via polymerization-induced microphase separation has been proposed by this dissertation.Incorporating the polyethylene glycol-based macro-chain-transfer agent and polyoxometalates which with protons and lithium ions respectively in an organic solvent containing styrene and divinylbenzene monomers,after deaeration,simply heating required only to generate a reversible addition-fragmentation chain transfer（RAFT）polymerization reaction and the desired solid-state electrolyte can be obtained after drying treatment.The resulting high-temperature anhydrous ion conductive nanocomposite exhibit a bicontinuous morphology,in which the polyoxometalates is uniformly dispersed in the polyethylene glycol block（PEG/POM）to form a conducting pathway that successfully realizes the effective transfer of protons and lithium ions,and the highly cross-linked polystyrene（P（S-co-DVB））domains as mechanical support providing outstanding mechanical properties and thermal stability.The prepared nanocomposite material overcomes the safety and stability problems of traditional solid-state electrolyte when working under high temperature conditions,and avoids the shortcomings that the small molecule acids incorporated in existing solid-state electrolyte are easy to seep out from the polymer matrix.The process of this method is facile and scalable,and the quality is easy to control,which broadening the application of fuel cells and lithium-ion batteries in extreme environments.The proton conductive nanocomposite PW₁₂-PEG5k-b-P（S-co-DVB）prepared in this experiment has a bicontinuous morphology,and the characteristic length scale between the PEG/PW₁₂ and P（S-co-DVB）domains is 16～20 nm.Among 30 wt%PW₁₂-PEG5k-b-P（S-co-DVB）sample has a proton conductivity of 2.03×10^-4 S cm^-1 under the high temperature and anhydrous condition of 150℃that realizes the effective conduction of protons,and the thermal stability temperature of the material is above 200℃,which ensure the application of the obtained proton-type solid-state electrolyte in extreme environments.The lithium ion conductive nanocomposite 30 wt%Li₇V₁₅-PEG400 prepared in this experiment has a lithium ion conductivity of 1.12×10^-4 S cm^-1 at 80℃,and conductive activation energy is at a low level of 0.228～0.511 e V fitted by Arrhenius equation.The lithium ion conductive nanocomposite Li₇V₁₅-PEG5k-b-P（S-co-DVB）prepared in this experiment has a bicontinuous morphology,and the characteristic length scale between the PEG/Li₇V₁₅ and P（S-co-DVB）domains is 17～27 nm.Among 30 wt%Li₇V₁₅-PEG5k-b-P（S-co-DVB）samples have a lithium ion conductivity of 2.71×10^-6 S cm^-1under the high temperature and anhydrous condition of 145℃that realizes the effective conduction of lithium ion,and the thermal stability temperature of the material is above200℃,which ensure the application of the obtained lithium ion type solid-state electrolyte in extreme environments.A high Li transference number（LTN）of 0.87 at 80℃when applied to Li|Li₇V₁₅-PEG5k-b-P（S-co-DVB）|Li symmetric cell,which is close to single-ion-conducting polymer electrolyte.