High Density Cation Adsorption Of Porous Aromatic Framework (PAF-1) Via Cation-? Interaction And Their Application

With the enlargement of city scale and explosion of population,the non-renewable fossil energy has become increasingly unaffordable.The use of fossil energy will bring a large amount of greenhouse gas emissions,leading to serious climate change,bringing a series of ecological imbalance.In the face of energy shortage and severe ecological environment,developing clean and recyclable energy materials has become a global focus.Because of their small size and portability,lithium secondary batteries have brought great changes to people's life and social economy since commercialization,and they are highly supported by people and make fossil-fuel-free societies possible.Development of electrolyte materials with high Li⁺adsorption and transport capacity is very important because the ability of electrolyte to absorb and conduct Li⁺determines the performance of lithium secondary batteries.In order to control the continued emission of carbon dioxide,it is also necessary to curb the use of fuel cars.In addition to choosing batteries to replace vehicle fuel,proton exchange membrane?PEM?fuel cell is also a candidate for vehicle energy.This new type of reverse device realized by water electrolysis is environmentally friendly and pollution-free,which is recognized as the first choice for electric vehicles.The key technology lies in the properties of PEM which requires high proton conductivity.Currently,Nafion,the most widely used PEM material,is highly dependent on environmental relative humidity and not suitable for working in an environment higher than 80?,which limits the development of its application scope.Therefore,the key to the development of PEM fuel cell is to find a high thermal stability material with high adsorption capacity of H⁺and high transmission efficiency.Ultimately,the challenge for current energy development is to address the storage and diffusion capacity of the two cations involved in battery reactions.Cation-?interaction are widely found in cationic and electronic rich carbon-based materials,especially those containing aromatic rings.Porous Aromatic Framework?PAF-1?is a kind of network polymer that connects aromatic elements through covalent bonds to form an open skeleton.This kind of material has a huge specific surface and excellent physical and chemical stability,which is very suitable for application in energy storage,adsorption and other fields.The unique aromatic and porous properties are the advantages of solving the adsorption and transport problems of H⁺and Li⁺.According to the requirements of current energy,the adsorption of Li⁺and H⁺in the porous aromatic framework polymer?PAF-1?based on cationic-interaction and their application in solid-state lithium secondary batteries and proton conduction materials are studied.The specific content includes the following parts:In Chapter 2,LiPF₆@PAF-1,H₂SO₄@PAF-1 and H₃PO₄@PAF-1were synthesized by cation-?interaction between PAF-1 and cations?Li⁺and H⁺?.Results of calculation and simulation show that PAF-1 has high absorption of lithium ion.The continuous three-dimensional porous network and large enough pore volume in PAF-1 provide unobstructed channel for lithium ions to rapid transmit.The results of IR showed that PAF-1 had adsorption properties to LiPF₆,H₃PO₄ and H₂SO₄.PXRD,TGA,XPS,EDS analysis results all prove that LiPF₆ exists in PAF-1,so that the structure of LiPF₆@PAF-1 keeps the amorphous shape of PAF-1and is reversibly recovers to PAF-1 after several washing exchanges with ethanol.DFT calculation shows that there is a strong binding force between PAF-1 and LiPF₆,and each PAF-1 unit can absorb up to 735LiPF₆ molecules.The simulation results of LiPF₆@PAF-1 by DL Poly computational code molecular dynamics simulation show that the optimal location of Li⁺adsorption is between two benzene rings in PAF-1.Static single pulse excitation?SPE?solid-state NMR prove that Li⁺has strong movement ability.In Chapter 3,H₂SO₄@PAF-1 and H₃PO₄@PAF-1 were synthesized and the properties of proton conductivity was explored.The proton conductivity of H₃PO₄@PAF-1 and H₂SO₄@PAF-1 was showed that both of these two substances had excellent proton conductivity under the condition of high temperature and super dry environment,which met the requirements of fuel cells for high proton conductivity and high temperature stability.In Chapter 4,The properties of LiPF₆@PAF-1 its application in solid-state lithium secondary batteries are introduced.Assemble the solid-state lithium secondary batteries by the LiFePO₄as the positive electrode,Li metal as the negative electrode material and the LiPF₆@PAF-1 as the solid electrolyte,electrode was treated with the droplet method to solve the solid-solid interface contact,a series of characterization of the battery performance were made.The results showed that the contact between solid and solid surface was improved after the electrode was treated.The results of the charge-discharge cycle stability test show that,compared with other solid-electrolyte batteries with the same electrode material,the battery can withstand higher current density and longer cycle period cycling.The results show that the battery has good cycling performance and stable interfacial contact.In conclusion,we take the development of new energy as the research motivation,a series of new materials were synthesized by PAF-1 as a raw material.The characterization,including structural simulation and electrochemical test,has proved that certain utilization value and development prospects for the application of new energy.